United statM
EnvlronrrwnUI Protection
Ag«ncy
Offteaof
Radiation Program*
WMiilngton, D.C. 20480
 August 1984
EPAS20/  1-85-012
 (PM.-5235)
Radiation
METHODS FOR  MEASUREMENT OF 222Sn EMISSIONS
FEOM DHDERGSOOND CRANIUM MINIS

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                BIBLIOGRAPHIC INFORMATION
                                           PB85-187953

Methods for Measurement of  (222)Rn
Emissions from Underground Uranium Mines
Aug 84

by P. 0. Jackson.

PERFORMER:  Office of Radiation Programs, Washington, DC.
            EPA/520/1-85/012

SPONSOR:  Department of Energy, Washington,  DC.

Sponsored by Department of  Energy, Washington,  DC.

Three methods are described for use  in monitoring  the
emission rate (activity per unit  time) of 222Rn in
ventilation air exhausted from active underground  uranium
mines. The methods include  procedures for making (1)
concentration measurements,  (2) flow-rate measurements,  and
(3) emission rate calculations.

KEYWORDS:  *Radioactivity,  *Mine  gases,  *Uranium mines,
           *Radon 222.

Available from the National Technical Information  Service,
SPRINGFIELD, VA. 22161

PRICE CODE:  PC A03/MF A01

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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing;
1, REPORT NO. 2.
520/1-85-012
4. TITLE AND SUBTITLE
Methods for Measurement of 222Rn Emissions from
Underground Uranium Mines
7. AUTHOR(S)
P.O. Jackson
9. PERFORMiNG ORGANIZATION NAME AND ADDRESS
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency
401 M Street, S.W.
Washington, D.C. 20460
3, RECIPIENT'S ACCESSION NO.
PB85 1879537AS
5. REPORT DATE
August 1984
6. PERFORMING ORGANIZATION CODE
8. PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Three methods are described for use in monitoring the emission rate (activity
per unit time) of 222Rn in ventilation air exhausted from active undergroung
uranium mines. The methods include procedures for making (]) concentration
measurements, (2) flow-rate measurements, and (3) emission rate calculations.
17. KEY WORDS AND DOCUMENT
a. DESCRIPTORS b.lDENTI

18. DISTRIBUTION STATEMENT 19. SECU
_-tJm4.-_j unc
unlimited 2Q SEC(J
unc
ANALYSIS
FIERS/OPEN ENDED TERMS C. COSATI Field/Group

RITY CLASS (This Report} 21, NO. OT PAGES
lassified 32
RITY CLASS (Tills page) 22. PRICE
lassified
EPA Form 2220-1 (Rev. 4-77)    PREVIOUS  EDITION is OBSOLETE

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                                          EPA 520/1-85-012
                                          (PNL-5235)
METHODS FOR MEASUREMENT OF 222Rn EMISSIONS
      FROM UNDERGROUND URANIUM MINES
               P.  0.  Jackson
                August 1984
    Prepared for the U.S. Environmental
 Protection Agency  under a Related Services
  Agreement with the Department of Energy,
      Contact No. DE-AC06-76-RLO  1830
       Office of Radiation Programs
    U.S.  Environmental Protection Agency
           Washington. D.C.  20460

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                                 DISCLAIMER
     This report has been reviewed by the Office of Radiation Programs,
U.S. Environmental Protection Agency, and approved for publication.
Approval does not signify that the contents necessarily reflect the views
and policies of the U.S. Environmental Protection Agency, nor does mention
of trade names or commercial products constitute endorsement or
recommendation, for use.

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                  METHODS FOR MEASUREMENT OF 222Rn EMISSIONS
                        FROM UNDERGROUND URANIUM MINES
Forward:
     The following three methods are intended for use in monitoring the emission
rate (activity per unit time) of 222Rn in ventilation air exhausted from active
underground uranium mines.  The methods include procedures for making 1) concen-
tration measurements, 2) flow-rate measurements, and 3) emission rate calcula-
tions.  The general format follows the usage found in the Code of Federal
Regulations -Title 40, Part 60, Appendix A.

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METHOD 1—DETERMINATION OF RADON-222 EMISSION RATES FROM UNDERGROUND
  URANIUM MINES; GRAB SAMPLING METHOD FOR MEASURING RADON-222 CONCENTRATIONS
  i.N MINE EXHAUST AIR

                                  Introduction

  A method Is described that uses scintillation flasks for grab sampling and
measuring the concentration of 222Rri in air.  There is a variety of commercial
and shop made flasks and counting equipment that can be used with them, and
any system which uses a scintillation flask which can satisfy the criteria
below may be used as a measurement system.  Since this technique is to be used
to evaluate the average 222Rn emission rate from air streams that often are
characterized by significant temporal variations of radon concentrations, it
will be necessary to average samples collected at several times tj  achieve the
necessary precision and accuracy, as outlined below.  It will also  be-necessary
to measure the flow-rates of exhaust air  at approximately the same  times that
samples are collected.
  1.  Principle and Applicability
  1.1  Principle.  Air containing gaseous radon  is withdrawn from each mine
vent using either an in-line probe or a vent-outlet probe which uses  the velo-
city of the air stream to force a sample  through the collection apparatus.  A
fraction of the air is filtered and drawn into a scintillation flask.  After
allowing the ingrowth of 218Po, 214Bi, 2i4Pb  and 214Po, which are the short
lived daughters of radon, the radon is determined by counting the scintilla-
tions produced  in the zinc sulfide coat-ing on the flask walls by alpha-particles
within the flask.
  1.2  Applicability.  This method applies to radon-222  (radon) emissions.   It
does not measure radon-220 (thoron) emissions.   Both long-term and  short-term
variations in emissions occur at uranium  mines.  This procedure will  yield
estimates of the average emission rate for a  calendar quarter when  several
samples are collected over an interval of several days within one quarter.  To
estimate an annual average, the measurements  must be repeated quarterly and
the results for each quarter must be averaged.   Since existing uranium mine
vents have several configurations, two sampling  techniques  and equipment are
specified - one for in-stack sampling where accessible sampling ports are pre-
sent and the other for sampling at the outlet of the vent.
  2.  Sensitivity and Range
  2.1 Sensitivity.  The sensitivity of this method  depends  on the size of the
scintillation flask and its background scintillation rate,  which normally in-
creases with use because of the accumulation  of  210pjj ancj  its daughter 210p0
from the decay  of radon in air samples stored in the flasks.  When  new, back-
ground counting rates from about 0.1 counts per  minute  (c/m) up to  1  c/m have
been reported for commercially available  flasks, depending  on make  and model.
Typically, the  backgrounds of 0.1 c/m are associated with  small flasks which
have a capacity of about 100 ml and response  factors of  about 0.5 c/m per pCi/1.
Backgrounds of  1 c/m are associated with  larger  flasks with capacities up to
1.4 liters and  response factors of about  6 c/m per  pCi/1.
  The limiting  sensitivity is defined here as that  concentration which is needed
to  achieve the  overall precision standard of  22% total error at the 95% confi-
dence level.  As will be discussed under  Paragraph  4, sensitivity  is  limited
by the statistical variations inherent in counting  radioactive decay events  as
well  as  three other  sources of variation. Using reported  estimates for the
magnitude of these terms, this method has a minimum sensitivity of  about 10
pCi/1 for a 30-minute counting time for  100 ml  scintillation flasks with back-
grounds  of 1 c/m and efficiencies of 0.5  c/m  per pCi/l«-

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  2.2 Range.  The maximum concentration that can be determined  is limited by
the maximum counting rate that can be measured without unacceptable losses
caused, by the pulse pair resolution of the instrument.  The pulse pair resolu-
tion time is the time required for the instrument to process and record a count
before a second count can be  detected and processed.  As counting rates get
progressively higher, the time between individual pulses gets shorter and shorter.
Eventually a significant fraction of the pulses are lost because the instrument
can't detect them until it  has completed the processing of the  preceding pulses.
Corrections can be made for such losses, but it is best to limit the counting
rate so that the maximum correction will be less than 10% because such correc-
tions are normally only approximate.
  Typical laboratory scintillation counters have pulse pair resolution times
ranging from about 2 microseconds up to 20 microseconds.  However, some commer-
cial counting systems may have longer resolving times because they are designed
for portability or for environmental samples with low activity. For resolving
times less than 20 microseconds, count-rates up to 3 X 10$ counts per minute
can be tolerated.  This is  equivalent to a radon concentration  of about 1.5 X
105 pCi/i for a 100 ml flask.
  3.  Interferences
  3.1  Moisture Entrapment.  Air from some uranium mine vents contains signi-
ficant quantities of entrained water droplets  that will be collected by the
sample delivery system.  Normally, if a small  quantity of entrained water  is
present, it will be stopped by the inlet filter.  However, when a visible  spray
of water is present, the droplets can plug the inlet filter or  pass through it
.into the scintillation flask  where the water will affect the detection effi-
ciency of' the scintillator  for alpha particles.  Therefore, filters should be
checked to be sure that they  have not become plugged after the  sample has  been
collected, and the interior of the sampling flask should also be checked for
liquid water.  Visible droplets on the window  of the flask indicate the presence
of  excess moisture.  In such  cases, a water spray removal system must be employed
in  the sampling apparatus.
  3,2  Particulate Matter.  Occasionally the quantity of particulate matter
present in mine ventilation air may be sufficient to block the  inlet filter.
For this reason, high efficiency fiberglass filters have been specified for
the sample collection system  because they plug more slowly than other high
efficiency filters.  If air is no  longer passing through the filter after  the
scintillation flask has been  filled and removed from the sampling line, the
filter is plugged.  Another sample should be collected when dust levels are
lower, or a larger area in-line filter should  be used.
  3.3  Static Charge.  Scintillation flasks often acquire static charges on
their surfaces during handling.  Such charges  can drastically change the count-
ing efficiency of the flask by attracting the  charged  ions of radon progeny
born  in the flask to areas  of the  flask where  the detection efficiency for the
alpha-particles emitted  in  their decay is significantly  different from normal.
This  is especially true for scintillation flasks constructed of plastic materials
which are  inherently non-conductors of electrical charge.  Static charge can
also  occur on the glass viewing window of metallic  flasks  and on inlet tube
connections.  For this reason, flasks which have non-conducting parts must be
treated to make them at  least temporarily conductive.  Some manufacturers  apply
coatings to the interior  of such  surfaces to make them conductive.  All noncon-
ducting exterior  surfaces must  be  sprayed with an  antistatic spray  before  using
the flasks.  This must be  done at  least three  hours  before counting to permit
the decay  of any  daughter  ions  attracted to charged flask  areas prior to spray-
ing.  The  flasks  should  not be rubbed or wiped between  spraying and counting.

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   3.4  Daughters of 220Rn.  In some cases, there is a possibility that signifi-
 cant quantities of 220Rn will be present in uranium mine air from deposits of
 thorium at the mine site.  Although 220Rn w-m decay to insignificance before
 counting because it has a half life of only 56 seconds, its longer lived daugh-
 ters, 2l2pb and 2081*1, will form within the scintillation flask between sample
 collection and counting.  This activity will be an insignificant fraction of
 the total activity unless the thorium content of the ore exceeds 5% of its
 uranium content by weight.  For mines that have thorium assays which average
 below 5 weight % of the uranium content, no corrections for 220Rn daughters
 are necessary.  For mines that do not have such assay information, or that
 have assay information indicating that the thorium content of the ore exceeds
 5% of its uranium content, a test must be performed to determine if a correc-
 tion for the 220Rn daughters will be necessary.  The correction must be deter-
 mined by re-counting one of the scintillation flasks, collected at each vent
 of the mine, three times at four-hour intervals after the initial count (one
 of the intervals may be as long as 20 hours if required by working shifts).
 The resulting count-rates should be plotted on semi-logarithmic graph paper.
 The final count should be decay corrected to the time of the initial count
 using the half-life of 222Rn.  if 220Rn daughters are present, the count-rate
 of the initial count will be higher than predicted by the extrapolation of the
 later counts.  The difference between the measured activities can give an in-
 dication of the amount of 220Rn daughters present.  Because this technique is
 sensitive to changes in count-rate, it is essential that the operator verify
 that the flasks being used do not leak significantly during the period of the
.evaluation and that procedures to minimize static charge have been used.
   If the'decay study of one set of samples indicates that the excess activity
 from the first count was less than 10X of the decay corrected activity from
 the later count, then the normal counting and delay intervals can be used for
 that vent.  If the excess exceeds 10%, the recommended procedure must be modi-
 fied on all subsequent samplings to permit a 2-3 day holding period before
 counting.  After that time the daughters of 220Rn will have decayed to less
 than 4% of their initial activity and can be assumed to be an insignificant
 fraction of the 222Rn activity, except for the highly unlikely event that the
 thorium content of the ore exceeds its uranium content, (in which case, the
 delay interval must be extended until counts taken at successive 24 hour inter-
 vals decrease with the characteristic half-life of 222Rn).
   4.  Precision and Accuracy
   4.1  Accuracy.  At the present time (Aug., 1984) there are no recognized
 primary national or international standard radon sources.  Laboratories per-
 forming radon calibrations normally use the equipment and method described in
 the ASTM standards (12.1).  In that method, radon ingrown in a sealed flask
 containing a  standard solution of 226Ra> traceable to the National Bureau of
 Standards  (NBS), is purged from the solution and transferred to the scintilla-
 tion flask using a prescribed transfer apparatus.  The radon ingrown in the
 sealed flask  between purges can be computed from the 226Ra concentration and
 the time  interval.
   Several  governmental  laboratories that routinely perform radon measurements
 using the  flask method have been participating  in an ongoing intercomparison
 study to evaluate the accuracy and precision of their measurements  (12.2, 12.3).
 These laboratories send four scintillation flasks to the Environmental Measure-
 ments Laboratory  (EML) of the U. S. Department of Energy.  There, the flasks
 are tested for  leaks and filled from  a large chamber containing air mixed with
 radon.  The scintillation flasks are  returned to the laboratories where the
 radon concentrations are measured.  Fisenne  (12.2, 12.3), reported the results

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 of the first  four  intercomparisons.   Those  results  indicated that there were
 difficulties  with  leaks  and/or  the calibrations  of  the radon flasks.  The range
 of average  results for eight  laboratories was  22% in the first  intercomparison,
 and  26%  in  the  second.   This  scatter  1n  calibrations is greater than would be
 predicted on  the basis of  the precision  of  replicate measurements and is also
 much  greater  than  the errors  normally estimated  for NBS radium  standards.  For
 this  reason,  the calibration  of scintillation  flasks by the ASTM method is not
 recommended at  this time.
   Currently,  two laboratories have tentatively been designated  to provide cali-
 brated mixtures of radon in  air based on their in-house calibration techniques.
 EML  can  provide radon concentrations  appropriate for environmental measurements.
 The  Bureau  of Mines maintains a laboratory in  Denver, Colorado which can provide
 radon at concentrations  typical of those encountered in uranium mine air.  For
 calibrations, scintillation  flasks must  be  shipped  to that laboratory where
 they will be  filled with the  standardized mixture.
   4.2 Precision.   Analysis  of  the errors contributed by various  sources inherent
 In this  method  indicates that it is  practical  to estimate the quarterly average
 radon concentration in  air from a uranium mine vent with a total  error of 22%
 at the 95%  confidence  level.  Therefore, an arbitrary limit of  22% has been
 set  for  this  total error.  The  total  % error,  (1.96 ST), can be derived from
 the  following expression:

      ST =

 where,   ..                              C
        ST =  the  total %  standard deviation of the method
        sc =  the  % standard deviation  from counting  statistics
        sm =  the  inherent  % standard deviation from replicate measurements
        sa =  the  stated % standard deviation of the  calibration standard
    and,
        ss =  the  standard  deviation of the measured  radon concentrations re-
        sulting from the  temporal variations of concentrations present  in air
        from  a  mine  vent.
   This formula  must be  adjusted for  the numbers of repeated sampling  and repli-
 cate flasks that must  be collected from a mine vent to  achieve  the required
 precision,  as will be  described later in this section.

   The %  standard  deviation from counting statistics, sc.
   The formula for  sc is  as follows:

                                 .  .  100 (EC + 2B)1/2
                                  c "      ECt1/2

 where,
    E  = the  counting efficiency,  counts/minute per pCi/1,
    C  = the measured radon concentration, pCi/1,
    B  = the  background count-rate, counts per minutes,
and t  = the  length  of sample and  background counts,  minutes

 Example:
 For  a scintillation flask with  a background of 1 c/m,  an  efficiency  of  0.5 c/m
  per  pCi/liter and  counting intervals of 30 minutes for  both sample  and  back-
 ground measurements,

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            100 (0.5C + 2)1/2

      c  "    0.5COO)"172


            (667C * 2670)1/2
     sc  "        C


For C = 10 pCi/1, sc = 9.7%.

  The inherent error of the flask method, sm.
  This error must be determined by filling several scintillation flasks with a
  constant known source of radon and calculating the standard deviation of the
  measured radon concentrations using the ordinary statistical formula, and not
  counting statistics (9.7).  Results reported by Jackson (12.4) indicate that
  the maximum inherent error should be about 7% for this method.  The measured
  value of sm must not exceed 7%.
  Precision of calibrations, sa.   This term should be obtained from precision
  estimates supplied by the calibration laboratory of'the Bureau of Mines.  If %
  standard deviations are not supplied, the reported standard deviations and
  average concentrations should be used to compute sa (using the same formula
  used for calculating s^ from the measured standard deviation (9.7).

  Variability of source term concentrations.  ss.   The variability of concen-
  trations at individual mine vents cannot be determined in advance of measure-
  ments.- For the purpose of this method-the average value of ss reported by
  Jackson (12.4) for short term temporal variations of radon concentration
  measured at 150 vents of 27 operating mines will be assumed to apply.
  Ss * 24X.

  Since the error associated with temporal variations of the source term alone
exceeds the prescribed limit for total error, this method requires that samples
be collected from each vent on more than one occasion.  The collection times
should be spaced at intervals.  It is also necessary to collect a duplicate
set of flasks at each vent at each sampling time to assure that the scintilla-
tion flasks have been properly filled and have not leaked.  Pairs of measure-
ments differing by more than the maximum allowable error (11.1) should be re-
peated at about the same collection time on another day.  The replicate measure-
ments will affect sc, sm and ss, but sa will not be affected.  A total of six
acceptable pairs of samples must be collected.
  To account for the total number of samples which will be collected, the formula
for the total error must be modified.  The standard deviation of the average
of several measurements  is equal to the standard deviation of the individual
measurements divided by the square-root of the number of measurements.  Since
sc and sm are affected by the total number of samples measured, but ss is only
affected by the number of repeated samplings, the total % error becomes:
        Total  % Error  «  1.96  sy =   1.96

  where
  12 = the total  number of samples (6 times  2)  and
  6   = the number of  repeated samplings.

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Using the previous estimates of sc, sm» sa, and Ss» the maximum total error is
as follows:


Tot.1 Error - 1.96

            = 22%

  5.  Apparatus
  5.1 Sampling Apparatus  (See Figures  1 through 4)
  5.1.1»  In-Stack Grab Sampling Probe.  This unit must comply with  specifica-
tions given in 10CFR60 Appendix A, Method 3, (2.1.1 and 2.1.2).   (See Figure 1).
  5.1.2   Vent-Outlet Sampling Probe*   The probe must be made of metal or  plastic
components joined with flexible tubing.  Joints must be clamped.  It must incor-
porate a  funnel  at the inlet to collect sufficient air to maintain  a positive
air flow. The funnel must  have a diameter of  at least 10 cm at the larger end
and no less than 1 cm at  the smaller end.  The funnel should be connected to a
stainless steel  tube of 1.3 cm  (1/2 inch) diameter and should be  formed with a
curve at  one  end with a radius  of approximately 23 cm (9 inches)  so that  the
funnel can be inserted into the outlet of a vent.  The overall length should be
about 1.8 meters (6 feet) and the short end should be about 38 cm (15 inches)
from the  top  (see Figure  2).
  5.1.3   Water Separator.  When water  is entrained in the ventilation air, a
separator for removing the  water must  be attached to the sampling probe at the
.bottom of the long end.   Flexible tubing-should be used for attachment.   Joints
should be" leak tight.  Water separators may be constructed of metal, glass, or
plastic.   However, glass  impingement separators are not recommended for field
work unless properly housed, because of the possibility of breakage.  Water
separators can be obtained  from commercial sources or can be shop-made.
  5.1.4   In-line Filter.  The  in-line  filter apparatus must use high efficiency
fiberglass filters with an  active filter area  of at least 7.5 cm2.   Filters
must be  at least 99.9% efficient for standard  0.3 |im OOP particles  in air.
Filter papers must pass at  least 20 liters/minute  at 2.75 psi head  pressure.
Filter housings  must be leak tight and suitable for fiberglass filters.   To
prevent  tearing  when using  units with  replaceable filter elements,  the com-
pressive  connections with the edge of  the filter paper must not rotate  as the
assembly is tightened.  Filter  housings which  prevent the filter  paper from
tearing  with  flow  in either direction  are recommended but not essential.   Plastic
or  metal  tubing  connectors  and  adaptors with leak  tight ribbed or serrated
tapers may be used.  At  least  two filter units will be  needed.  Ready-to-use
one-piece filtration devices with  suitable characteristics may be used  if integ-
rity of  filter and seals  are verified.
   5.1.5   Flowmeter.  The  flowmeter must be a rotameter  that  is direct reading
for air  and  has  a minimum scale reading 1  liter/minute  or  less and  a maximum
reading  between  9  and  15  liters/minute.  The scale accuracy must  be certified
by the manufacturer  or  a  test  laboratory to  ±  10%  or  less of full scale.
   5.2  Scintillation Flasks.  At  least four  scintillation flasks  of the  same
type must be  available  for  measurements.   Scintillation flasks may  be con-
 structed of metal,  glass, or plastic.  Flasks  must be  equipped with a flat
 transparent  viewing  window.  Viewing windows must  not  be  larger  in  diameter
 than the diameter  of the  face of  the photomultiplier  tube  used  in the counting
 system.   Flasks  must be  coated  with  silver-activated  zinc  sulfide phosphor on
 all interior surfaces  except the  viewing window.   They must  be equipped with

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       PROBE
                              FLEXIBLE TUBING
FILTER (GLASS WOOL)
                                                    TO ANALYZER
                  SQUEEZE BULB
      FIGURE 1.  In-stack grab sampling probe

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                               18" —
FIGURE 2.   Vent-outlet sampling probe

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Mine Vent (not drawn to scale)
                  \
                                • Vent Outlet Sample Probe
Rotameter
                          Water Separator
                                                                             Flexible
                                                                             Tubing
                                                  In-Line Filter
                                                                       Scintillation
                                                                         Flask
                          FIGURE 3.   Vent-outlet radon  sampling apparatus

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      Gauge
      Valve
Gauge  «—i	'
 Tube  r—*
      Pump
      Valve
  A* V  -A I Vacuum
  fc—     I Gauge
  OO   O
                                           /"/Vacuum Hose
                                                       Filter Assembly
                                             Filter
                                             Valve
                                                  Flask
                                                  Valve
Scintillation
   Flask
            FIGURE 4.   Flask evacuation assembly

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Clear Silica or Pyrex
Glass Window Coated
with Stannic Oxide
                                            Stopcock
                                Zinc Sulf ide
                                 Scintillator
                                   Coated .
Metal Walls
                    FIGURE  5.  Scintillation flask

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one or two valves or stopcocks suitable for high vacuum and positive pressures
up to 14.7 psig.  Flasks may have any combination of efficiency, volume, and
background counting rate that produces a relative counting error sc (4.2) no
greater than 10% with air containing 10 pCi 222Rn/liter using a 30 minute count-
ing interval on the counting system in use.  A typical small scintillation
flask is  shown in Figure 5.
  5.3  Counting System.  The counting system must have at least the following
components.
  5.3.1   Light Tight Counting Chamber to house photomultiplier tube and  scin-
tillation flask.  The counting chamber must be equipped with a photomultiplier
tube base and a resister string capable of supplying appropriate bias  voltages
to the photomultiplier  (P.M.) tube dynode stages and anode.  Radio frequency
and magnetic  shielding for the P.M. tube must be provided.  Suitable  con-
nectors for applying  high voltage to the P.M. tube must be provided.  The
chamber must be equipped  to supply a pulse signal from the P.M. tube  anode
that is decoupled from  high voltage.  A preamplifier may be included in  the
electrical circuit.
  5.3.2   Photomultiplier (P.M.) Tube.  The P.M. tube-must be capable of  opera-
tion at overall bias voltages of  at least 1400 volts,  and must have a  peak
spectral  response for emission wavelengths of 440-450  urn.  P.M. tubes  must
have flat end viewing windows.
  5.3.3   High Voltage Power Supply.  The power supply  should be capable  of
delivering the D.C. voltage requirements of the photomultiplier tube and the
current requirements of the resister string of the tube base.  High voltage
must be filtered, to give <10 mV  ripple peak to peak 5 hz to 50 mHz and  regu-
lated to  provide ? 0.0025% variation in" the output voltage-for any combination
of  line and load variation within the operating voltage and current requirements
of  the photomultiplier  tube and tube base  in normal  counting operations. Voltage
settings  must be indicated and adjustable  in steps of  "<25 volts; any setting
must be repeatable to within ± 0.5%.  Temperature  stability must be T  ±  50 ppm/°C
from 0 to 50°C.  Voltage and current requirements  of the power supply  must be
compatible with either  the power  supplied by the  low voltage power supply to
the counting system, or by 110V AC  lines.
  5.3.4   Amplifier.  The counting system amplifier must be compatible  with the
pulses from the output  of the photomultiplier tube base  (voltage, time con-
stant  and electrical  impedence).  Amplifier overall  gain must be sufficient to
produce  signal  pulses  larger than the noise discrimination level used  in either
the amplifier output or the sealer  input when the  photomultiplier tube is operat-
ing in  its normal voltage range.  Gain must be externally  adjustable or  preset
for optimum  system performance.   If preamplification is not provided by  the
tube base (5.3.1), a suitable preamplification  stage must  be provided  in the
amplifier with  an externally accessable  signal  test  point  at  its output. Gain
drift  must be ? 0.005%/°C.  The  amplifier must  provide pulse shaping networks,
and baseline restoration suitable for zinc  sulfide scintillator count-rates
expected  from  radon  concentrations  up to 1.5  X  10^ pCi/liter.  It must have  an
operating temperature  range from  0  to 500C.
   5.3.5   Scaler/Discriminator/Timer.  Sealer  input requirements must be  com-
patible  with  amplifier  output pulses and  impedence.  The sealer must have a
preadjusted  input  discriminator,  or  if  a discriminating stage with an  indicating
external  adjustment  to  eliminate  spurious  counting from noise or other erroneous
pulses.   If  the amplifier  contains  an  indicating  output discriminator, or  if  a
separate discriminator  stage  1s  provided,  the  sealer discriminator need  not  be
 indicating.   Sealer  circuits must have  at  least  20 MHz count-rate capability.
The count readout must  be  at  least  six  decades with  either LED or LCD  display.

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An overflow  indicator must be provided if less than seven decades are displayed.
Leading zeros must be suppressed.  If a separate timing unit is used, the sealer
must be provided with a gate to allow the timer to turn it on and off.  A test
feature which illuminates all segments must be provided for readouts.  The
timer must be crystal timebase controlled, with an inherent accuracy of at
least ± 0.0025%, and setable in minutes, with increments no larger than I minute
and a maximum interval that is not less than 60 minutes.  The timer must be
accurate to  within ± 0.01% over an operating temperature range of 0 to 50°C.
The timer must provide gating signals compatible with the sealer.
  5.3.6  Cabinet/Power Supply.  The amplifier, sealer, (discriminator), and
timer must be housed in a suitable cabinet that has provisions for housing the
power supply where necessary.  The cabinet must provide all power needs of the
equipment it houses with suitable regulation of the needed power.  Ventilation
must be adequate to prevent internal temperatures greater than 50°C with all
housed equipment operating, in an environment which is less than 35°C.
  5.4  Vacuum Pump.  A small one or two stage rotary vane vacuum pump must be
used.  The ultimate blank-off vacuum must be 20 microns or less and free air
pumping rates must be at least 20 1/min.  The exhaust outlet must be connectable
to tubing or hose no larger than 3/4" I.D. to permit exhausting to outdoors.
  5.5  Vacuum Sauge.  The vacuum-gauge must be a thermocouple type with a range
of 0-1000 microns of mercury (0-5000 microns optional) and a direct meter readout.
It must be equipped with a metal gauge tube with a male npt thread connector,
threaded to  metal or plastic tee adapter.  The metal gauge tube and tee adapter
are to be coupled to vacuum pump shut-off valve (5.8).
  5.6 Pressure Gauge, Air.  The range, ofcthe pressure gauge must be 0-15 psig.
It must b'e accurate to 3% of its scale range.
  5.7 Compressed Air Regulator.  The regulator must have single or double stage
control and  a flow indicator.  The regulator must conform to the following
specifications:  maximum inlet pressure:  3000 ps1; outlet pressure range:  4-
80 psi; flow range:  0.2-2 slpm.  The Inlet connector must be CGA 346 or other
as used for  air cylinders specified In Paragraph 6.2.  Regulator must be equipped
with shut-off and flow control valves.
  5.8 Vacuum/Pressure Valves (three required).  The valve shut-off, and connec-
tions must be leak tight.  The internal flow restriction must provide a maximum
flow of at  least 20 SCFM air at a pressure drop of 10 psi.  Valves isolate the
vacuum pump, (5.4) vacuum-gauge, (5.5) and the outlet of in-line filter (5.1.4).
  5.9 Explosion Shield.  The explosion shield must be suitable for scintilla-
  tion flask pressurization or evacuation operations.
  5.10 Barometer  (optional).  The barometer must be calibrated for the alti-
tudes at the sampling site against a mercury barometer.
  5.11 Oscilloscope  (optional).  The oscilloscope must provide a bandwidth 100
M Hz or more; a minimum sensitivity of 5 mV/div; fastest sweep of no more than
20 ns/div;  a triggered sweep.  It must provide sweep speeds from 20 ns/div to
at least  50  ms/div and calibrated verticle scale from 5 mV/div to at  least 5
V/div.
  6.  Reagents
  6.1  Anti-Static Spray.  Any commercial anti-static spray in an aerosol can  .
may  be used. Test a  small area to be certain that spray constituents do not
attack plastic  components of scintillation flasks.
  6.2 Air,  Dry  Compressed  .  Compressed  air must comply with the following
specifications:  maximum dew point -75°F, or maximum moisture 3 ppm; maximum
pressure  2200 psi; outlet connector compatible with regulator (5.8).  This air
must  be  aged at  least 30 days befora use, to allow 222Rn to decay.

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  7.  Standards
  7.1  Calibration Sources.  Caution.  Radioisotope standards  are  available
from commercial  and governmental suppliers.  However, the possession, trans-
portation,  and use of radioisotopes are regulated by federal,  state  and  local
statutes.   For possession of many radioisotopes, licenses are  required.  Per-
sons not  specifically trained  in the safe handling of radioactive  materials
'should not  perform analyses involving their use.  Compliance with  institu-
tional, local, state, and federal regulations concerning the procurement and
use of radioactive materials is the responsibility of the laboratory using
this method.
  7.1.1   Radon-222.  Institutionally calibrated  222Rn jn air  is  available from
the U. S. Bureau of Mines, Denver Research Center.  Flasks  to  be calibrated
must be appropriately packaged to prevent damage and shipped to  the  center
where they  will  be filled with air containing radon.  A range  of concentrations
is  available.  For the  purpose of this method, a concentration of 1000  ± 200
pCi/liter should be requested. The shipping address is:
          U. S. Bureau of Mines
          Denver  Research Center
          Bldg. 20, Denver Federal Center
          Denver, CO  30255
          Attention:  Radiation Hazards Group
  Prior to  sending flasks, a written request for calibration  should  be  sent to
the Research Center.  The type of flask to be filled, its  approximate volume,
the desired concentration, and the approximate date when the  calibration will
.be  needed,  should be specified.  Details can then be worked out  between the
laboratories.  The radon concentration, internal pressure,  relative  humidity
of  fill air, calibration date  and time, and the  estimated  accuracy of the cali-
bration at  one standard deviation will be needed from the  research center.
  A convenient regenerative source of radon in air  using 22bRa •}„ solution can
be  constructed  (12.1) or a radon generator using 226Ra  in  a solid substrate
can be purchased commercially. These sources can be used  to  make periodic
checks of counter characteristics but must not be used  for  flask calibrations.
  7.1.2   Control Source Scintillation Standard.  Point  source reference stan-
dards of  alpha-particle emitting radionuclides are  available  from the National
Bureau of Standards  or  commercial sources.  These standards are  prepared from
radioisotopes which  require a  federal or state license  for  repossession.  In
Table 7.1 are listed two appropriate  alpha-particle emitting point source  stan-
dards and potential  suppliers  (Other commercial  suppliers  may be available.
The listing of  a commercial supplier  does  not constitute  endorsement by the
U.S.  Environmental  Protection  Agency or  its contractors).


                                   TABLE 7.1

              Point  Source Alpha-Particle Emitting Standard Sources

  Radionuclide          Nominal Activity Range         	Supplier	

Plutom'um-238        11 -  540  nCi  (specify)            U.S.  Bureau of Standards
Americium-241                   50nCi                  New England Nuclear  Corp.


   Standards purchased  for  this method must have  a  nominal  activity in the
 range from 10-50 nCi.

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  After receipt, the alpha-particle-emitting control source should be mounted
on a disc of transparent plastic coated with silver activated zinc sulfide
scintillator.  Material of this type is available from William B. Johnson
and Associates, Research Park, Montville, N.J. 07045.  Other suppliers may
be available.  See endorsement disclaimer above.
  These scintillation control sources should be prepared by mounting the
alpha-particle emitting source(s) with emitting surface facing the scintillator
surface.  (Note:  if the two-source technique will be used to determine the
instrument dead time (9.3), the alpha particle emitting sources should not
be permanently attached to scintillator discs until after measuring the dead
time.  With that technique, both sources are mounted precisely on a scintilla-
tor disc and the counting rate measured.  Then each must be mounted separately
in the exact original positions and each counted.) After dead time measure-
ments are taken, each source must be permanently  attached to a scintillator
disc.  A diagram of one possible method for construction of this control
source is shown in Figure 6.  Specific dimensions of the scintillator disk
are not critical as long as it is larger in diameter than the mount of the
alpha-particle emitting point source, and equal to or. less than the diameter
of the face of the photomultiplier  (P.M.) tube used for counting scintillation
flasks.  If the outside diameter of the scintillator disk is the same as  the
face of the P.M. tube, it will be easier to reproducably mount the source at
one location on the P.M. tube.  An  index line should be marked on the edge
of the source  so that  its orientation can be reproduced in counting.
  8.  Safety Precautions.  The laboratory is responsible for compliance with
all applicable federal, state, local, and institutional health and safety
regulations  in performing this method.  "Appropriate eye, ear and hand protec-
tion and protective clothing should be worn.  Sorcie of the safety considera-
tions when  sampling uranium mine vents are  as follows:
  8.1. Operations involving handling pressurized  or evacuated scintillation
flasks  involve risk of explosion or implosion.  Care should be used to prevent
dropping or  damage.  Damaged scintillation  flasks should not be used until
repaired.   Appropriate explosion shields should be  used when pressurizing or
evacuating.
  8.2. The  sound pressure level near some operating mine vents can be suffi-
cient to cause hearing  imparement,  so effective ear protection should be
worn in these  cases.
  8.3.  Concentrations  of 222Rn  in air emitted from some mine vents may be
orders  of magnitude greater than the concentrations  specified for occupational
exposures.   Although potential exposure  intervals are very brief, for those
occasions where there  is risk of excessive  inhalation exposure,  appropriate
respiratory protection  should be worn.
  8.4.  When sampling or measuring flow rates  from operating vents,  it  is
necessary to be aware  of the  location of  air moving components,  so that  acci-
dental  contact with moving parts will be  avoided.
  8.5.  Since the  air velocity from  mine  vents can be  of the order of  several
hundred meters per  second, entrained  sand,  dust  and gravel can be thrown
from the vent  outlet with considerable force.  Appropriate eye protection
should  be worn.
  8.6.  The  operating voltage for  some fan motors  is as  high  as 440V.  Care
should  be taken to  avoid sources of electric  shock.
  ?.   Pretest  Procedures
  9.1  Leak-testing  Scintillation Flasks
  Scintillation flasks must  be  tested  for  leaks  before  and   after calibrating
and at  weekly  intervals when  samples  are being  collected  at  daily intervals

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Point Source Attached
with Pressure Sensitive
Plastic Tape
Alpha Particle Emitting
Point Source (Activity
Facing Scintillator)
                                                   Top Surface Coated
                                                   with Silver Activated
                                                   Zinc Sulfide Phosphor
                                                Transparent
                                                Plastic Film
                                       Reference Line for Positioning Source
                                       Drawn on Edge
      Alpha-Particles
                                                  Pressure Sensitive
                                                  Plastic Tape

                                                  Point Source
                                                  Zinc Sulfide
                                                  Phosphor on
                                                  Plastic Film
      FIGURE  6.   Suggested scintillating control  source assembly details

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or oftener.  Both tests (9.1.1) and (9.1.2) should be performed initially,
then (9.1.1) can be used for routine testing.  Before vacuum leak testing,
the vacuum system between the pump shut-off valve and the gauge, and filter
assembly must be sufficiently leak tight that pressures do not drift more
than 5% in a one-hour period at total pressures below 800 microns of Hg.
Before pressure testing, verify that scintillation flasks are designed to
withstand high vacuum and internal pressures exceeding 14.7 psig because of
the explosion hazard.  During vacuum and pressure testing, scintillation
flasks should be behind a suitable explosion shield.
  9.1.1  Vacuum Testing.  Assemble the vacuum pump, gauge, and one of the
on-line filters.  Attach a vacuum valve  (5.8) to the pump (5.4) inlet, with
the flow direction  into the pump.  Attach  the vacuum-gauge (5.5) to the valve
inlet using a tee fitting.  Attach a second valve to the third leg of the
tee fitting.  Connect a flexible tube to the inlet of the second valve.  Attach
a tee fitting to the flexible tubing .  To one leg of the tee, attach the
third vacuum valve  (5.8).  To the vacuum valve attach the outlet of an in-
line filter (5.1.4).  To the other leg of  the tee, attach a length of flexible
tubing which can be attached to the scintillation flask  Inlets  (see Figure 5.)
These connections may be made with flexible tubing and ribbed connectors or
with threaded connectors.  All connections must be vacuum tight with the
scintillation flask inlet plugged  (see above).  Attach a scintillation flask
to the vacuum pump, gauge and filter assembly.  Evacuate the flask to give a
measureable vacuum  less than 800 microns.  Record the pressure, close the
scintillation flask valve and store for  at least 16 hours.  Reattach the
flask to the pump  assembly.  Evacuate  all  lines to the initial  internal pres-
sure of the flask.  Close valve between-the vacuum pump  and gauge and open
the scintillation flask valve.  Residual pressure in the scintillation flask
must not have  increased to more than 1000  microns.   If a greater pressure  is
measured,  determine source of the  leak and repair it.
  9.1.2  Pressure Testing.  Attach the output of the compressed air regulator
(5.7) to the inlet  of filter assembly.   Close the gauge  valve.  Insert a tee
fitting between  a  scintillation flask  and  the pump assembly inlet hose and
install the pressure gauge  (5.6).  With  regulator shut-off valve closed, set
the pressure of  the regulator output to  4  psi.  Open the regulator shut-off
valve and  flask  valve.  Slowly open the  flow control valve and  pressurize
the flask  to 4 psi  on  the pressure gauge attached to the tee.   Close the
flask valve  and  regulator shut-off valve.  Remove the flask and store it for
at  least  16 hours.  Re-attach the  flask  to the tee.  Open the  regulator shut-
off valve  and  again adjust  line pressure to  4 psi on gauge attached to tee.
Close the  regulator shut-off valve and open the flask valve.   The pressure
should  be  at  least  3.9 psi.  If a  pressure leak  is observed, the leak point
may be  determined  using a leak-testing bubble solution or by emersion of the
flask  in water.  Repair pressure  leaks before using  the  flask.
   9.2 Optimizing Electronic Set-points.  Unless the  optimum settings for
counting  scintillation  flasks  have been  previously determined,  the operating
high  voltage  (H.V.) and set-points for the counting  system must  be established.
The H.V.  applied to the P.M. tube  must be  within the operating range for the
tube  specified  by  the  manufacturer.   In  no case  should the H.V.  setting be
 above  the  maximum  specified for the  tube.
   Place a scintillation flask  filled with  air containing at  least 800 pCi
222Rn/liter on  the P.M. tube in the  light  tight chamber.  Close the chamber
 and wait 5 minutes. Attach  a  suitable oscilloscope  to the test point between
the preamplifier output and  amplifier  input.  Turn on  the H.V.  Increase  the
H.V.  while observing pulses from  preamplifier.   Pulses will  increase  in  size

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as voltage increases.  Increase the H.V. until the largest pulses from pre-
amplifier begin to clip (flatten at their top).  Then decrease the voltage
slightly until no clipping is observed.  Record this initial H.V. setting.
  If the amplifier has adjustable gain, set the control(s) to the approximate
center of the gain span.  Adjust the discriminator between amplifier and
sealer to minimum discrimination.  Take a count and record the count-rate.
Increase the discriminator setting by 10% of full scale.  Take a count and
record the count-rate.  Repeat over the full range of the discriminator.  At
minimum discrimination the highest count-rates should be observed.  The count-
rate should decrease with increasing settings.
  In the center of the span there should be a range of  settings where count-
rates change by about 5% between settings.  (This is the discriminator plateau.)
The set-point for the discriminator is the setting at about  the center of
the plateau.  If count-rate does not drop by at least a factor of two between
the discriminator plateau counts and those at the maximum setting, the amplifier
gain setting should  be reduced by about 10%.  Re-set the discriminator to
maximum and measure  the count-rate.  Continue decreasing amplifier gain by
10% steps and determine the point where the count-rate  is about a factor of
two lower than it is on the discriminator plateau region.  This is the ampli-
fier set-point.  Then take a new series of measurements with 10%  increments
of the discriminator.  Set the discriminator  at the set-point where the count-
rate is in the center of the discriminator plateau region as defined  above.
If there was no discriminator plateau on the original set of measurements,
and count-rates fell by a factor of two or more at lower discriminator settings,
the amplifier gain should be increased  i.;n 10% steps until the count-rate at
a discriminator setting of 30% of full  scale  is less than 10% lower than the
count-rate at a setting of 20% of full  scale.  This is  the  approximate ampli-
fier set-point.  Then the count rate should be remeasured at each discriminator
satting to establish the discriminator  plateau and set-point.  The  amplifier
set-point can be readjusted slightly if necessary to optimize the upper end
of the plateau curve.
  After the set-points for the discriminator  and amplifier  gain have  been
established, the H.V. plateau should be determined.  Set the amplifier and
discriminator to their set-points.  Lower the H.V. by 300 volts from  the
initial set-point, and measure the count-rate.  Increase H.V.  in  100  volt
steps, measuring the count-rate at each step.  The count-rate will  increase
rapidly at first, then increase more slowly.  When the  count-rate  again  in-
creases rapidly, discontinue increasing the H.V.  Reduce the H.V.  by  200 V.
  Make a  linear plot with the count-rate as the ordinate and the  H.V.  as the
abscissa.  The region of the curve through the data which has the minimum
slope is  the  H.V. plateau.  The slope  of the  H.V. plateau  should  be less
than 5%  increase of  count-rate per 100  V  increase of H.V.   The  length of the
H.V. plateau  should  be at least 100 V.  If necessary,  intermediate  points on
the plateau can be measured at 50 V intervals.  When measurements  are com-
pleted,  turn  off the H.V. and remove the flask.  The  useful  settings  for
H.V. are  approximately  in the center of the H.V. plateau  but should not  ex-
ceed the  initial H.V. setting determined by oscilloscope  testing,  by more
than 50V.  A  voltage plateau for the  instrument  background  should also be
measured  using  a new flask filled with  aged  air  (9.5).   A  series  of overnight
background counts  should be taken, one  at  each  of the  previously determined
H.V. plateau  set points.  The optimum  H.V.  setting will have the  minimum
background count for a  voltage  setting that  is  on the  original  plateau.   If
necessary, the  H.V.  set-point can  be  at any point that  is more than 50V  from
the extremities of  the H.V. plateau.   The  optimum  settings  and  all  sample,

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background, and calibration counts made at those settings must be recorded.
For nominally identical scintillation flasks, these settings may be assumed
to be the same from flask to flask.  Otherwise, optimum settings for H.V.
should be determined for each kind of flask, but amplifier and discriminator
settings should not be readjusted.
  9.3 Instrument Dead Time.  Unless the instrument dead time for the scintilla-
tion flask counting system has been provided by the manufacturer, it must be
determined by. the operator.  The  dead time should be determined using one of
the methods given by ':he National Council on Radiation Protection and Measure-
ments (12.9).  Zinc-sulfide scintillation counters may be assumed to have
non-extendable dead time effects, over the range of count-rates expected for
mine-vent monitoring.  One or two alpha-particle emitting source(s) mounted
on zinc sulfide phosphor disc(s)  (7.1.2) will be needed for this calibration.
  The source-pulser method is recommended for its relative accuracy and sim-
plicity; otherwise, the two-source method is suggested.
  Once the dead time has been established, the expression relating the true
count-rate to the observed count-rate is:
N = n/U-nr)
where,
      N = the corrected count-rate,
      n = the observed count-rate,
and,  T = the dead time in the same time units as count-rates.
  When T has been measured, this  equation can be used to determine the corrected
count-rate for any given measured rate.
Using the expression:                   ;.
                    _  0.01
the  count-rate  corresponding to a 1% correction  (N/n * 1.01) can be determined.
For  count-rates below  that quantity,  the dead time  correction may  be neglected.
   9.4 Control Source Checks.  The control  source (7.1.2)  is used to determine
that the  counting  efficiency of the counting system remains constant after
calibration.  The  count-rate for the control source is established during
calibrations.   Daily counts of the control  source are made when samples  are
being analyzed  to  establish that the efficiency  has not changed significantly.
   After the H.V. operating point has been established for scintillation  flasks,
the  control source must  be counted at that H.V.   Before flask calibration
counts are taken,  position the control source on the P.M. tube, close  the
light tight counting chamber, wait five minutes, adjust H.V. to the set-
point and take  a count of sufficient duration to accumulate at least 20,000
counts.  Record the count.  Turn off the H.V. Remove the source and then
replace it and  repeat  the counting process.  Repeat removing, replacing  and
counting  the control source ten times.  Remove the  source, and measure the
background counting rate for the empty counting  chamber using the  same count-
ing  interval.   Compute the count-rate for all counts.  Subtract the empty
chamber background count-rate from all control source count-rates. Then
compute the average count-rate for the control source and compute  the  rela-
tive standard deviation  of the net count-rate.  If  the relative standard
deviation exceeds  1% of  the average, the variability of control source counts
is excessive.   In  that case, it is necessary to  determine whether  the  source
positioning is  inconsistent or the counting system  is malfunctioning.  Once
the  source of excess variation has been corrected and a set of 10  control

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source measurements with acceptable variability has been accumulated, pre-
pare  a control chart with the average count-rate for that counting system
and limits of  ±2% of the average count-rate shown on the verticle scale and
the dates of measurements shown on the horizontal scale.
  Each day before samples are counted, make one measurement of the control
source and the empty-chamber background using the same time interval as pre-
viously.  Plot the net count-rate on the control chart.  If the net count-
rate is within ±2% of the previous average, the system is in control and may
be used for samples.  If a control source count-rate falls outside the limits,
repeat the count one time.  If it falls within limits, the instrument may be
used.  If it does not, a counter malfunction is likely, and the cause of the
changed counting efficiency must be determined and corrected.  If the first
count falls outside of limits on two consecutive days the cause must also be
determined and corrected.
  9.5 Backgrounds.  Prior to calibration or sampling, the background count-
rate for each  flask must be determined using scintillation flasks filled
with compressed air that has been aged for at least 30 days to permit the
decay of any radon initially present.
  9.5.1  Evacuation and Filling.  For flasks with two" inlet valves, evacuation
is unnecessary, and flushing may be accomplished with the vacuum-pump and
gauge isolated from the system, using aged compressed air, through the filter
inlet.  For flasks with a single inlet valve, the following procedure must
be followed.   Attach the vacuum pump, gauge and filter  assembly  (Figure 4)
to the flask using flexible tubing.  With the flask valve closed, evacuate
the system.  Turn on the thermocouple gauge.  While pumping, open the valve
on the scintillation flask and evacuate-to less than  1000 microns pressure.
Close the valve on scintillation flask.  Close the vacuum-guage valve and
open the filter-assembly valve.  Open the valve on scintillation flask and
allow it to fill with filtered ambient air.  Close the  filter assembly valve;
then open the  vacuum-gauge valve and evacuate the flask to less than 1000
microns pressure.  Repeat filling and flushing two more times.   Evacuate the
flask to less  than 1000 microns pressure and close the  flask and vacuum-
guage valves.  Attach the outlet of the compressed air  regulator to the filter
inlet.  Adjust the regulator pressure to 4 psi with regulator shut-off valve
closed.  Open  the  niter assembly and vacuum-gauge valves and pump the filter
assembly to  less than 1000 microns.  Shut off the gauge valve.  Open the
regulator  shut-off valve and flask-valve and slowly open the flow control
valve of the regulator.  Allow the flask to fill until  flow rate drops.  Close
the flask  valve  and regulator shut-off valve.  Remove the flask from the
assembly and open the flask valve briefly to allow pressure to equilibrate
with  ambient atmospheric pressure.
  9.5.2  Background Count Measurement.  Spray the exterior of the evacuated
flask with  anti-static spray and store overnight.  Place flask in the counting
chamber taking care to center the window of the  flask on the photomultiplier
tube.  Select  one orientation for  all flasks  (e.g. valve handle  facing forward)
so  that the  geometry  is  consistent.  Close the chamber.  Allow five minutes
for the phosphorescence  of the scintillator to decay  to insignificance and
adjust H.V.  to the  set-point  and  initiate a 30-minute background count.  Record
the counts  registered, the count  interval, flask number, and counting date
and time.   Compute  background counts per minute  and record.  The background
count-rate for each flask may be written on the  flask or  a label attached to
the top  of the flask.  However,  static charges may be induced when  removing
gummed  labels, so  they should not  be removed until after the sample has been
collected  and  counted.
                                      20

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  9.6 Calibration
  Prior to any sampling run, calibrate the system using  the following  proce-
dures.  A complete calibration should be performed before making  field measure-
ments and at six month intervals.  Send all scintillation flasks  used  for
field measurements (at least four flasks) to the Bureau  of Mines  to  be filled
with a known quantity of 222Rn in air (1000 ± 200 pCi/1),  (7.1.1.) When  flasks
are received, examine them for damage in shipping, spray all  exterior  surfaces
with anti-static spray.  Delay counting for at least three hours  after spraying.
Place a scintillation flask on the P.M. tube in the counting  chamber and
close the lid.  After five minutes, adjust the H.V. to the set-point.  Preset
the time to at least 30 minutes, and initiate the count. Record  the time  of
the count, flask identification code and length of the count.  After completion
of the count, record the count registered on the sealer. Turn  off the high
voltage, remove the flask and replace it with the next flask  to be calibrated,
and repeat the process.  After all flasks have been counted one time,  repeat
the process a second time for all flasks.  After 1-2 days, recount all flasks.
  If the elevation at the measurement site is more than  1000  feet higher or
lower than the elevation in Denver, Colorado, the pressure within the scintilla-
tion flask will be significantly different from the pressure  normally present
when flasks are filled during sampling.  This can make a small  difference in
the counting efficiency of the flasks.  If the elevation is  lower, filtered
ambient air may be allowed to bleed into each flask through  a length of  tubing.
(The radon concentration in the ambient air should be negligible  compared to
that inside the flask.)  Close flasks as soon as possible after filling  to
minimize outward diffusion of the fl as fcv contents.
  If the- altitude at the location of sampling is more than 1000 feet higher
than at Denver, CO., it will be necessary to bleed a portion  of the  air  from
each flask to achieve pressure equilibrium.  Bleed air from  the flask to the
outdoors or a suitable fume hood through a 4-5 foot length of tubing.  Close
the flask as soon as possible.  The dilution of the flask contents will  be
negligible and the net effect will be the removal of a fraction of the radon-
air mixture.  The fraction removed can be determined from the barometric
pressures and temperatures at the time of filling and at the  sampling site.
If a local weather station cannot provide the barometric pressure,  it must
be measured with a barometer (5.11).
  After bleeding or filling flasks, repeat the original  counting  procedure
again, taking three counts spaced by at least 1 to 2 days.  After counts
have been completed, efficiency factors should be computed before evacuating
flasks.
  9.6.1  Correction for loss of Flask Contents after Bleeding.  The  correction
factor for computing the fraction of the initial radon-air mixture remaining
in the flask is as follows:

                    . P2Ti
                    -  --
where:
   F  =  the fraction  of  initial air containing 222Rn remaining in the flask
   P!  =  the barometric pressure of the fill  air at the time of filling, mm
        Hg,
   ?2  -  the barometric pressure at the sampling site,. mm Hg,
   TI  =  the absolute  temperature of the fill  air  at the time of filling, °K,
and,
   T2  =  the absolute  temperature at the location  when bleeding air, °K.
                                      21

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  9.6.2  Efficiency Calculations.   The following  formula must  be  used  to
compute flask efficiencies:

       CCs-CB(ts/tB)](X) exp (XT)
   C. """ ""Pi
where,
  E  = the flask efficiency, counts/min per pCi Z22Rn/iiter,
  Cs = the observed standard count during the counting interval
  CB = the observed background count prior to filling,
       exp (X) is the XHL power of the base of natural logorithm
  X = the radioactive decay constant for 222Rn (1.259 x 10-4 min-1),
  T » the interval between the start of the count and the date/time of the
      fill at calibration, minutes,
  ts = the length of the standard count interval, in minutes,
  tg ~ the length of the background count, in minutes,
  F = the fractional loss of air for flasks bled at the sampling site, (F=1.0
      unless flask pressure was reduced by bleeding before the count)
  P = the calibration concentration of the 222Rn in the flask at the time of
      fill calibration, pCi/liter,
and,
  T = the dead time determined for flasks, minutes.

  Tabulate counting efficiencies and respective counting dates and times.
For each flask compute the average and relative standard error of the average
for the original set of three counts and also the second set if flask air
pressure was increased or decreased.  Use ordinary statistical formulas and
not errors based on counting statistics.  The statistical formula to use is
as follows:
                              ^ fxAc rv *2  1/2

                   1. = +(100)   1=1     1=1
                   x   ~
where,
   Eg -  the relative  standard error of the average efficiency, *,
   n   =  the number of replicate counting measurements used to determine the
   average efficiency,  (3  in this case),
and,
   Xi  =  the efficiency determined from the itn count, c/m per pCi/1.
   The relative  standard errors of each average must be less than ±3%.  If
errors  exceed 3%, determine if there is a decrease in efficiency with time
for  each set of counts.   Such decrease indicates that a flask is probably
leaking.  Scattered  efficiencies indicates that there has probably been a
problem with static  charge buildup on flasks.  In the latter case, an addi-
tional  set of counts may  be taken after again spraying with anti-static spray
and  waiting at  least three hours.  If flask internal pressures have been
adjusted, this  additional set should correspond to the set taken after adjust-
ment.  A new overall average and relative standard error of the average may
be taken after  discarding the efficiency of any single count which represents
an extreme value.  This relative standard error must not exceed ±3.
                                      99

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  If the relative error of the efficiency for any flask exceeds 3%, the flask
should be evacuated, checked for leaks, and leaks repaired, and returned to
the Bureau of Mines for recalibration.  The efficiency of a flask should be
constant under constant conditions of internal pressure.  A variation of
measured efficiencies can be caused by changes in internal pressure, the
distribution of radon progeny within the flask or the presence of a barrier
such as liquid water on the scintillation surface.  The average efficiency
for the set taken after any required pressure adjustment will normally differ
from the original average by less than 15%.  If pressure was increased, the
efficiency should decrease, and if pressure was decreased, the efficiency
should increase.  The ratio of the efficiency after pressure adjustment to
the original efficiency for flasks of the same nominal construction must be
consistent.  Any flask with a ratio differing from the average ratio for
other flasks of the same construction by more than 5% must also be re-cali-
brated.
  Average efficiency factors with less than 3% relative standard deviation
may be used in sample computations for the corresponding flask.  If adjustment
of the internal pressure of flasks was necessary, the average efficiency for
each flask after the pressure adjustment must be used in sample computations.
After calibration counts are complete, evacuate and flush the flasks with
ambient air, exhausting their contents outdoors or to a fume hood.
  Test all flasks for leaks (9.1).
  9.7 Replication Errors (sm)
  Replication error is the inherent error of  a set replicate measurements
when a constant concentration of radon- is measured with several flasks under
conditions such that the inherent counting errors are negligible.  Unless  a
source of radon, known to have a fixed concentration, is available at the
laboratory, flasks  should be returned to the  calibration facility of the
Bureau of Mines after the original .calibration.  At least four flasks must
be used in this test.  When flasks have been  filled and returned, the radon
concentrations should be measured and each corrected to a  single reference
time using the original calibrations.  Counting  intervals must be  long enough
to accumulate at least 20,000 counts for each flask so that  the error from
counting statistics is negligible.  Then the  standard deviation of the repli-
cate concentration measurements should be calculated using the usual statisti-
cal formula  (9.6.2).  sm must be equal to or  less  than 7X,  which  is the
assumed maximum  inherent error for this method.
   10. Sampling and Analysis Procedure.
   10.1 General Considerations.  This  section  describes  the use of  apparatus
and protocol for sampling and measuring 222Rn concentrations.  To  establish
the  average  characteristic emission rate during  a particular quarterly  interval,
 it is necessary  to  measure both the 222Rn concentrations  and vent  flows from
all vents  of a mine.  Because of the  short-term  variability  of the emission
rate, grab-sampling measurements must  be repeated on  six  occasions  and  averaged.
Duplicate  grab samples must be  taken  on each  occasion.  The  sampling schedule
must  be  adjusted to include emissions  under  typical operating conditions  and
to exclude occasions when non-typical  short-term variations  are probable.
All  six measurements must be completed in  a  calendar  quarter of a  year.   Samples
must  not  be  collected  at  the following times:
   1.  Within one hour of  shift  change  or blasting.
   2.  During a period when mine ventilation  is other  than that typical  during
 active  mining,   (e.g.  a  shut-down or  flow-reversal).
   3.  Within two hours after  shut-down or  reversal  of  vent fans.
   4.  During or  within 24 hours after passage of a  local  weather disturbance
 (storm)  that produces  an  atypical barometric pressure.  '

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  Sampling times must be spaced so as to obtain a representative sampling of
the air concentrations present during normal operating conditions.  One of
the six samples must be collected between 1:00 and 3:00 P.M. to include the
normal daily concentration maximum reported by Jackson (12.4).  The remaining
samples should be collected at uniform intervals during working shifts.  At
mines which have more than one exhaust vent, samples should be collected
from all exhaust vents before resampling any vent.
  Since some existing mine vents are not equipped with in-line sampling ports,
two alternate sampling methods are given.  For sampling from vents with exist-
ing sampling ports, the in-line sampling technique should be used.
  10.2 Sample Collection.  Use scintillation flasks that have been sprayed
with anti-static spray.  Measure flask background count-rates  before using.
For flasks with a single valve, evacuate before sampling.  Flasks with two
valves need not be evacuated.
  10.2.1 Sampling vent stacks with access sampling ports.  A modification of
the in-stack grab sampling procedure specified in Method 3 of Appendix A,
40CFR Part 60 (12.8) must be used.  When entrained water is present, fit the
water separator (5.1.3) to the outlet of the squeeze iulb (5.1.1).  Then
attach the inlet of the in-line filter assembly (5.1.4) either directly to
the squeeze bulb outlet or to the outlet of the water separator.  Insert the
probe into the access port and position as  instructed in Method 3 of (12.8).
Squeeze the bulb several times to completely flush the sampling system.  (At
least enough times to pump 10 times the normal volume of the system).  Attach
a scintillation flask (5.7) to the outlet of the  in-line filter using flexible
tubing.  Open the inlet valve of an evacuated flask or both valves of dual
inlet flasks.  Squeeze the bulb a sufficient number of times to pressurize
or flush the scintillation flask.  Flushing should be continued uoiil at
least 10 flask volumes have been pumped through.  Close the flask valve(s).
Remove the flask and attach a second flask.  Repeat filling or flushing the
flask.  After both samples have beetr collected, partially open one valve of
each for 1-2 seconds, then close, to allow  the internal pressure to equilibrate
with ambient atmospheric pressure.  Record  the flask identification codes,
sampling site, and the date and time of sampling  in a field notebook.  The
vent flow must be measured immediately preceding  or following sample collection.
Return flasks to the laboratory for counting.  Avoid rubbing flask exterior
surfaces to minimize the possibility of inducing  static charges.
  10.2.2 Sampling Vent Stacks without Access Ports.  Assemble vent outlet
sampling apparatus (5.2).  When entrained water is present, fit the water
separator  (5.1.4) to the outlet of the probe  (5.1.2) with flexible tubing.
Then attach the inlet of the in-line filter assembly  (5.1.4) either directly
to the probe outlet of the outlet of the water separator.  Connect the flow-
meter  (5.1.5) to the outlet of the in-line  filter.  Flexible tubing should
be attached to the outlet of the flow-meter to permit attaching the scintilla-
tion flasks.  See Figure 3.
  Before inserting the funnel end of the probe  into the outlet of a vent,
observe the interior of the vent to determine the locations of moving parts
and obstacles.  A suitable ladder may be needed.  Cautiously  insert the funnel
end of the probe into the air stream and into the vent.  With the outlet of
the probe  parallel to the air stream, the plane of the face of the probe
funnel  inlet will be facing to the stream.  The bend  of the metal probe tube
will  limit the depth that the probe ran be  inserted into the  vent.  It is
necessary  to insert the proba as deeply as  possible without touching moving
parts.  Do not  insert deeper than tlie limit created by the  bend in the metal
tubing.  Air will be forced through the probe and attached  equipment.  Adjust

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the position of the probe to obtain the maximum possible flow, indicated by
the flow-meter.  Any sampling flow-rate greater than 2 1/min will supply a
sample in a reasonably short time.  Attach a scintillation flask inlet valve
to the tubing on the outlet of the flow-meter.  Slowly open the inlet valve
of the scintillation flask.  For evacuated flasks, allow to fill slowly so
that the fill rate does not exceed the rate of supply.  For flasks with dual
inlet valves, open the second valve and allow the flask to flush for the
interval necessary to pass at least 10 flask volumes.  When evacuated flasks
are filled, the flow indication will drop to zero.  Close flask valve(s) and
remove from the hose.  Attach a second scintillation flask and repeat the
sampling.  After both samples have been collected, partially open the inlet
valve for 1-2 seconds, then close, to equilibrate the interior pressure with
the ambient atmospheric pressure.  Record the flask identification codes,
sampling site and the date and time of sampling  in a field notebook.  The
vent flow must be measured immediately preceding or following sample collec-
tion.  Return the flasks to the laboratory for counting.  Avoid rubbing the
flask exterior surfaces to minimize the possibility of inducing static charges.
   10.3 Counting Scintillation Flask.  Wait at least three hours after filling
scintillation flasks to permit the ingrowth of the short-lived daughters of
222Rn.  The counting system must be in control (9.3) before using.  Place a
scintillation flask in the light tight chamber in the same orientation to
the P.M. tube that was used during calibration.  Close the light tight chamber,
turn on H.V. and adjust to the set-point.  Wait  5 minutes.  Adjust the timer
for a 30-minute count interval.  Initiate the count.  Record the time that
the count started, the flask  identification code, sampling site, and the
date and -time of sampling.  When the count  is completed, record the number
of counts.  Turn-off the H.V. and, change samples.  Repeat the counting-proce-
dure for all samples.  Calculate the radon concentrations before pumping
samples from scintillation flasks.  If a pair of duplicate measurements differs
by more than the maximum allowable error  (e^x)  Siven below, recount both
flasks  and recalculate radon  concentrations  and  allowable errors.  Record
all results.  Any pair of  the measurements from  two flasks not differing by
more than eraax can be averaged and the average used as the acceptable measure-
ment for a given sampling.  If no pair of measurements are acceptable, the
sampling must be repeated.  If there  is a possibility that 220Rn -js present
in mine  air recount flasks  as indicated in Paragraph 3.4 and  use the results
to determine an appropriate delay time between sampling and counting.
   11. calculations.  Carry out all calculations  retaining one extra decimal
place beyond that present  in  the acquired data.  Round off the numbers follow-
ing calculations, retaining three significant figures.
   11.1  Allowable Error.  The  formula for the  allowable error  (e) between
replicate samples  is as follows:
                    e = 200
       1/2


100,
 where,
   e  = the allowable error between duplicates (%)
   Cs - the gross sample count including background,
   ts = the sample count interval, minutes,

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  CB = the background count interval,  minutes
  tB - the background count interval,  minutes
and
  sm = the measured inherent limiting  precision (9.7)  of scintillation  flask
  measurements, %.
  The allowable error or each of the pair of flasks must be  calculated.  The
  maximum allowable error (emax) 1s the larger of the two values  of  e.
  11.2 Radon.Concentration.  The formula for calculating the concentrations
of radon is as follows:
                                               [exp(XT)]
                                (l-exp(-Ats}]  E  [l-Cs(T/ts)]
where,
  P = the z"Rn concentration in pCi/liter,
  X = the decay constant for 222Rn (=1.259 X 10 "4 min'1),
  exp (X) = the X power of the base of the natural logarithm
  T = the interval between sample collection and the start of the sample
      count, minutes,
  E = the efficiency factor for the scintillation flask, c/m per pCi/1,
and
  T = the dead time for the counting system in minutes.  (T may be assumed
      to be zero for sample count-rates which give a dead time correction less
      than 1% (9.3).

After calculating the average concentrations for pairs of sampling flasks
with acceptable allowable error, for each of six samplings, record all results
on a sample record sheet.  (See Figure 7 for an example.)

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         FIGURE  7.  Example of Radon Count/Calculation Record'Table.
 Record  of Radon Concentration Measurements
 Company_

 Mine
 Vent  Identification
Sample  1.

  Sampling Date/T1me_

Background Counts
        Flask
                                      Date/Time
                                   Length of Count
   Total Counts
  Flask
              Instrument
Date/Time    Length of Count    Total Count     Radon Cone.
Allowable Error
Test A.  Minimum % Range Between Duplicate Flasks
B.  Maximum % Allowable Error
                                                                    *.  Test
                             _
      concentration from Test "A" Flask Measurements
pd/llter.  IF "A" > "BB".  Resamplc.
                                                 _
                                                £  If "B" > "A".  Average

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   12.  References
   12.1  Procedure 03454.   1984,  Annual  Book  of ASTM  Standards.   Section  11,
 Water and Environmental Technology.   Volume  11.02-Water  (II).   American  Society
 for Testing and Materials,  Philadelphia,  PA   15103.
   12.2  Fisenne, I.  M., A.  C.  George,  and H. W.  Keller.   Radon  Measurement
 Intercomparisons at  EML.   Environmental Measurements Laboratory, Department
 of Energy, New York, NY.   DOE/EML-397,  October 1981.
   12.3  Fisenne, I.  M., A.  C.  Seorge,  and H. W.  Keller.   The  1982 Radon  Inter-
 comparison Exercises at EML.   Environmental  Measurements Laboratory,  Department
 of Energy, New York, NY.   EML-413,  March 1983.
   12.4  Jackson, P.  0., et al.  An  Investigation of  Radon-222 Emissions  from
 Underground Uranium Mines.   Pacific Northwest Laboratory, Department  of  Energy,
 Rlchland, WA.  NUREG/CR-1273,  PNL-3262, RU.   February 1980.
   12.5  Beckman, R.  T. Calibration Procedures for Radon and  Radon-Daughter
 Measurement Equipment. Denver Technical Support Center, Mining Enforcements
 and Safety Administration,  Department of Interior, Denver, Colorado.   Informa-
 tional Report MESA-IR-1005.
   12.6  Lucas, H. F.  Improved Low-Level Alpha Scintillation  Counter  for
 Radon.  Review Sci.  Instrum.,  Volume 28, pg. 680, 1957.
   12.7  George, A. C.  Scintillation Flasks  for  the  Determination of  Low-
 Level Concentrations of Radon.  Proceedings  of the Ninth Midyear Health  Physics
 Symposium, Denver, Colorado.   February, 1976.
   12.8  Part 60, Appendix A-Reference Methods.   Code of  Federal Regulations-
 Title 40, Protection of Environment.  Parts  53 to 80. Revised as of  July 1,
-1982.  Available from Superintendent offDocuments, U.S.  Government Printing
 Office, Washington,  D.C.  20402.
   12.9  Dead-Time Corrections.  Handbook of  Radioactivity Measurement Procedures.
 Recommendations of the National Council on Radiation Protection and Measurements,
 7910 Woodmont Avenue, Washington, D.C. 20014, pp. 54-66, November, 1978.

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 METHOD 2  - VENT FLOW MEASUREMENTS

   1.  Principle and Applicability.
   1.1  Principle.   To determine the rate of 222Rn emissions  from underground
 uranium mines,  both the average radon concentration in the air and the volu-
 metric flow rate must be measured.   The volumetric flow rate measurements
 must be taken at the above ground portion of the mine exhaust vent using the
 reference technique found in Method 1 of Appendix A, 4QCFR Part 60, (See
 Method 1, 12.8 for reference).  A traverse of air velocity measurements
 must be taken in the accessible portion of the vent which best conforms to
 the requirements of that method.
   1.2  Applicability.  Method 1 (12.8) specifies that it can not be used
 when (1)  flow is cyclonic or swirling. (2) a stack is smaller than about
 0.3 m (12 in.)  in diameter or 0.071 m2 (113 in.2) in cross-sectional area or
 (3) the measurement site is less than two stack or duct diameter downstream
 or less than a half diameter upstream of a flow disturbance.  However, measure-
 ment points at existing mine vents rarely conform to item (3) and occasionally
 fail to conform to items (1) and (2).  At some vents-no in-line access ports
 have been provided for sampling and velocity measuring traverses.  At some
 mines, air is exhausted from large entry portals where no stack is present.
 Procedures for a detailed assessment of the applicability of this method are
 given in  the EPA Quality Assurance Handbook for Air Pollution Measurement
 Systems-Volume 3.  Stationary Source Specific Methods, EPA-600/4-77~027b
 August, 1977.  This volume also gives more detail about measurement and sampl-
. ing considerations than is present in ('|2.8).  If it is determined that the
 reference method is not applicable to a'measurement site, suitable modifica-
 tions to  the sampling site must be made or the administrator must be consulted
 about alternative measurement methods, such as the anemometer technique given
 in Method 14 of (12.8).
   2.  Computations.  For flow measurements from mine vents, the computation
 of average stack gas velocity conforms to Paragraph 5.2 of Method 1 (See
 Method 1, 12.8 for reference).  However, 2"Rn concentration measurements
 are made  after equilibrating the internal pressure of the sampled air in
 scintillation flasks with the local barometric pressure.  The normal computation
 for stack gas volumetric flow given in Paragraph 5.3 of the reference method
 converts  the velocity to the equivalent volume of dry air at standard barometric
 pressure and temperature.  For the purpose of this method, it will not be
 necessary to make this conversion.  The applicable formula is as follows:


                             3.6X106 VCAPC
                        Qe =	p	—
                                 pbar


 where,
   Qe - volumetric ambient stack gas flow rate corrected to local barometric
       pressure, liter/hour),
   3.6 X  10° = conversion factor, (sec/hr)(liters/m3),
   vs s Average stack gas velocity, m/sec,
   A = Cross sectional area of stack, m2,
   Ps * Absolute stack gas pressure, mm Hg,
        (Ps = Pbar + Pg)

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  Pbar = barometric pressure at measurement site,  mm Hg,
and
  Pg = stack static pressure, mm Hg.
  2.1  Summary Table.   A summary table must be prepared listing  the mine,
vent number, and flow  rates calculated for each of the six  sampling intervals.

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METHOD 3—COMPUTATION OF RADON EMISSION RATES
  1.  Principles and Limitations
  1.1  Principals.  Radon emission rates must be computed for each mine vent
from the average radon concentration measured in Method 1 and the flow rate
measured in Method 2.  An emission rate must be computed for each of six
sampling occasions.  Then the six emission rates must be average to give the
average rate  for that vent during one  quarter of a year.  The annual average
emission rate is the average of four quarterly averages.
  1.2  Limitations.  Limitations of the measurement processes are discussed
for methods 1 and 2.  The computational process produces average emission
rates relative to the barometric pressure at the sampling site.  Thus, the
emission rates are useful for predicting local concentrations of radon as a
result of  atmospheric dilution.  (If exposure rate estimates at distant sites
are required, radon concentrations and stack flow rate determinations would
have to be corrected to the equivalent dry air at standard temperatures and
pressures.)
  2.  Calculations.  Carry out calculations retaining one extra decimal figure
beyond that present in the required data or previously calculated values.
Round-off  results to three significant figures.
  2.1 Summary Table
  Prepare  a summary table listing the  radon concentration and flow rate for
each of the six sampling occasions at  each vent of the mine.  An example of
such a table  is shown in Figure 8.  Reserve the final column for the results
of emission rate calculations.
Operator:
                Figure 8.  Sample Summary Table

                         Summary Table
               	   Mine Identification:
Quarterly Interval;    4/84  -  7/84
Vent

1
1
1
1
1
1
2
2
  Samp! ing
  Date/Time
6-3-84/08:40
6-4-84/11:25
6-3-84/14:25
6-4-84/16:15
6-3-84/18:30
6-3-84/21:10
6-4-84/09:20
6-3-84/11:35
Vent/Flow fl/hr)
   8.49 X 107
   8.62 X 107
   8.52 X 107
   8.47 X 107
   8.53 X 107
   8.41 X 107
   5.13 X 107
   5.21 X 107
222f,oncentration
    fpCi/1)

     528
     541
     823
     613
     548
     534
    1560
    1610
    Emission
rate fl/hr)
   2.2   Emission Rate Calculation.   The emission rate for  any sampling  of  a
mine vent should be calculated using the following equation:


Evt •  10~12 
where:
   Evt  =  the hourly emission rate  of 222Rri from vent v at sampling  time t,
          Ci/hr
   Cyt  =  the measured average 222Rn concentration in air  from vent  v at
          sampling time t,  pCi/liter

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  Fvt =  the measured average volumetric stack gas/low rate for vent v at
         sampling time t, liter/hr.
  After calculation, emission rates should be placed in the summary table.
  2.3 Calculation of quarterly average vent emission rate.  The quarterly
average emission rate for each mine vent is the arithmetic mean of the six
measurements taken at that vent (all taken within a 30 day interval).

                 Ey » 1/6  I  Evt
WnfilTS*                    *.— 1
  Fv = the quarterly average emission rate of vent V, li/hr,
  *vt =  the emission rate of vent V at the ttn sampling, Ci/hr.

  2.4 Calculation of quarterly average mine emission rate.  The total emission
rate for a mine  is the sum of the average emission rates determined for all
exhaust vents for that quarter.  The emission rate is computed as follows:
J  E
                           Ev
where:                v=l      ««_
  !ma = tne quarterly average  *"Rn emission rate for mine m, with n vents,
Ci/hr.

  2.4 Calculation of annual average mine emission rate.  The annual average
emission rate for a mine  is the arithmetic mean  of four quarterly average
emission rate measurements taken at intervals  of about three calendar months
The formula for calculating the annual average is as follows:
                 Ema =  1/4   I   Emq
                           q=l
where:                     ,,.,,
  Ema * the annual  average "^Rn emission rate for mine m, C1/hr.

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