EPA 680/0-74-004
August 1974
DETERMINATION OF THE PHYSICAL AND CHEMICAL CHARACTERISTICS OF
ENVIRONMENTAL PARTICULATES CONTAINING RADIONUCLIDES
by
E. W. Bretthauer
Monitoring Systems Research and Development Laboratory
National Environmental Research Center
Las Vegas, Nevada
Program Element 1FA083
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
LAS VEGAS, NEVADA 89114
-------
FINAL -
INTERIM REPORT
ROAP 21BAS. Tasks 03, 04. 13
ROAP 21AMI. Task 18
"Determination of the Physical and Chemical Characteristics
of Environmental Particulates Containing Radionuclides"
A. J. Cummings, J. A. Hodgeson, and E. W. Bretthauer
June 1974
-------
I CONCLUSIONS
Significant results obtained for Tasks 03, 04, and
13, ROAP 21BAS, and Task 18, ROAP 21AMI, to date are:
A. In-house work has shown that it is feasible to
collect, locate, and isolate alpha emitting particles col-
lected on air filters. An Interim Progress Report on this
work is shown in Appendix A. This work also showed that,
large conglomerate particles (10-20 ym) were subject to
fragmentation into smaller (1-2 pm) particles.
B. Preliminary chemical and physical analyses of
airborne plutonium particles collected in Area 11 of the
Nevada Test Site (NTS) have been made by GE Vallecitos
Nuclear Center. Analytical data on air filters included
size, specific activity, chemical composition, and isotopic
ratios. The data collected revealed the presence of at
least four classes of particles: (1) small, high-activity
in an organic matrix, (2) large, low-activity in a silicate
matrix, (3) large, low-activity in an organic matrix, and
(A) small, high-activity oxides.
C. A purchase order has been given to GE Vallecitos
Nuclear Center, through the Air Force Technical Applications
Center at Patrick Air Force Base, to perform detailed chemical
and physical characterizations of individual plutonium and
-------
americium containing particles collected on filter paper
during atmospheric sampling.
D- A dichotomous air sampler for fractionating
atmospheric particulates into respirable ys non-respirable
ranges, has been ordered and will be used to collect air
samples for the study.
E. Initial air sampling has begun at NTS. A remote
location southwest of Las Vegas has been chosen as a background
collection site.
F. Requirements for the physical and chemical character-
istics of environmental iodine-129 will not be satisfied under
present contractural arrangements. Instead an intensive litera-
ture review of the state-of-the-art knowledge has been performed,
A report derived from the review is being prepared.
II RECOMMENDATIONS FOR FY-75
Plans for the coming fiscal year relative to this task
are:
A. Efforts will be continued to obtain from the AEG
laboratories and the Department of Defense material relative to
this project. Significant findings from the literature review
will be incorporated into a final report, which will also
include results from the particle study being conducted
-------
by GE Vallecitos Nuclear Center.
B. In-house screening of local background samples will
be.conducted to determine level of atmospheric fallout of
plutonium. Some selected samples will be forwarded to the
GE Vallecitos Nuclear Center for detailed analysis.
C. Preliminary screening will also be conducted of
the NTS samples. A few selected samples will be forwarded
to the GE Vallecitos Nuclear Center for detailed analysis.
D. Dichotomous air samples will be collected in the
environs of other nuclear facilities, e.g., Rocky Flats,
Hanford Atomic Facility, and the Savannah River Nuclear
Facility. If suitable arrangements can be made, samples
will also be collected directly from each source. Such infor-
mation should give insight into the effects of resuspension
and aging on plutonium particulates.
Ill INTRODUCTION
The output of ROAP 21BAS consists of a series
of research reports on environmental transport of the radio-
nuclides plutonium and iodine-129 which define parameters for
-------
population exposure models. These parameters will be related
to the various types of environments typical of regions
near emission sources. While plutonium will receive primary
emphasis, iodine-129 and americium-241 will be studied
concurrently.
Most previous investigations dealing with environmental
radionuclide pollution have been confined to the determination
of the concentration of specific radionuclides at certain
locations and in certain media by simply assaying the radio-
activity of the collected samples. Relatively little is
known about the physical and chemical characteristics of
airborne plutonium or the effect of time and of soil
and climatic parameters on these characteristics after depos-
ition. This knowledge, however, is essential for any pre-
diction of transportation phenomena in terrestrial and aquatic
environments and for biological availability determination.
Our approach to these tasks has been (1) to review
currently available information on the chemical and
physical properties of radioactive plutonium, iodine,and
americium in the environment; (2) to conduct sampling at
various types of nuclear facilities involved in the nuclear
fuel cycle both at the source and in the surrounding environs,
and (3) to have detailed particle characterizations performed
under contract. By sampling at the source and in the local
-------
environs, information can hopefully be derived on the
effects of aging and resuspension on plutonium containing
particles. One critical problem that must be emphasized
at this point is that of obtaining approvals to sample
source terms at any of the more important nuclear fabrica-
tion facilities within the United States. In addition, all
nuclear fuel reprocessing plants are closed and not expected
to open for at least one year.
IV RESULTS AND DISCUSSIONS
A. In-House Particle Study
A number of large diameter, 18.5 cm, air filters
from a previous REECo air sampling project were obtained
for analysis as a preliminary step to field sampling.
Several of these samples were subjected to autoradiographic
techniques to determine the presence of radioactivity. Those
areas showing activity were subjected to a cursory in-house
analysis. This analysis consisted of dissolving those
indicated areas of filter material in carbon tetrachloride and
filtering off the contained particles. The dried filtrate
was subjected to alpha counting for confirmation of radio-
activity and to microscopic examination. Several particles
were physically isolated for individual observation and photog-
raphy. The results of this preliminary investigation are
discussed in an interim progress report (Appendix A). In
this report it is shown that it was possible to locate the
-------
gross position of an alpha emitting particle on filters,
and to isolate and manipulate these particles for further
study, i.e., observation and gamma and/or alpha spectroscopy.
Some of the larger particles (10-20 micron diameter) were
very fragile and tended to shatter into fragments on the
order of 1 to 2 microns. This observation suggests that
during aging larger particles may degrade into particles
in the respirable range.
B. Extramural Particle Study
A single 18.5 cm filter was submitted to the GE
Vallecitos Nuclear Center for detailed examination. A
2
6.5 cm section was processed by the GE Vallecitos Nuclear
Center and 32 radioactive particles out of at least 55
observed were randomly selected for further analysis.
All 32 radioactive particles were microscopically sized.
Mass spectroscopy and electron probe analysis were performed
on 12 of the sized particles. The analysis indicated that
the observed geometric diameter ranged from <0.5 to
17.0 ym with an activity of 4 to 26 femtocuries/particle»
and further, that these particles could be grouped into
-------
four distinct classes (See Appendix B). The size, activity
and chemical composition of those particles are summarized
in Tables I & II of Appendix B.
A purchase order was accepted by the Air Force to
provide the services of GE Vallecitos Nuclear Center for
the subsequent analysis of air filter samples obtained under
this task. The work to be performed by GE Vallecitos Nuclear
Center can be summarized as follows:
1. Approximately 100 individual air samples will
be submitted and examined for radioactivity by autoradio-
graphic techniques.
2. The contractor will select approximately 25
of the above air samples for detailed analysis.
3. The detailed physical analysis will consist
of the following:
a) Total number of alpha-active particles
present.
b) Estimate of alpha activity per particle.
c) Estimate of physical size ranges of
alpha-active particles.
d) Density estimate from size and chemical
characterization (see Section 4 below).
e) Photographs of at least 10 particles.
-------
8
f) At least 2 submicron particles will be
examined by electron microscopy to determine size and shape.
g) Particles of diameter greater than 1 micron
will be sized and shaped by optical microscopy.
4. A detailed chemical analysis will consist of:
a) Gross elemental composition determination
by mass spectroscopy and electron probe analysis.
b) Ion microprobe analysis will be performed
on at least 2 particles per filter.
c) Isotopic composition of any uranium,
americium, and plutonium present will be determined.
d) Elemental distribution of at least one
large particle will be determined by scanning electron probe
analysis.
e) Gross chemical composition by electron
microprobe will be attempted on the two submicron particles
selected for step 3-f above.
f) Crystal structure for at least two
particles will be determined by x-ray and/or electron
diffraction.
C. Field Sampling
The field sampling program was begun by placing
two high volume (air flow ==0.5 m /min) air samplers in Area 8
at the NTS at the surface of ground zero of a previous air blast
A remote mountain peak 15 miles southwest of the city of
-------
Las Vegas has been chosen as a sampling area to obtain back-
ground samples. A southwesterly direction was chosen due
to the prevailing winds in this section of the country. This
area allows placement of our sampler in a region that should
be relatively free of contamination from the NTS and from
locally released particulates. The site is presently being
used by the Union Pacific Railroad as a communication site.
These air samples, as well as others later obtained,
are now being screened by EPA personnel. Some selected
samples will later be shipped to GE Vallecitos Nuclear Center
for detailed analysis. The pre-screening consists of
subjecting the filters to gross alpha counting and in-house
autoradiography. The 37 mm filters are counted directly;
particles collected on 185 mm filters are resuspended and
refiltered on 37 mm filters prior to counting. The detector
used is a zinc sulphide screen and photomultiplier-tube pulse
counter. The device is at least 49% efficient with a back-
ground of 0.18 counts per minute (170 femtocuries). This
background is sufficiently low to permit screening of most
o
filters. Selected 6.5 cm sections from four 185 mm
filters have been resuspended and screened and found to
contain greater than 1.5 picocuries of alpha activity/filter.
A two-stage dichotomous air sampler based on a design
developed at the National Environmental Research Center,
Research Triange Park, NC, has been ordered and should be in the
-------
10
field by approximately August 1, 1974. This sampler, using
37 mm diameter millipore type AA filters, separates the
particles into two groups, (L) those less than 2 ym in diameter,
and (2) those in the 2 to 20 ym diameter range. This separa-
tion is designed to yield fractions of respirable versus non-
respirable particulates directly. A third and separate filter
simultaneously collects a total particulate fraction. The
dichotomous sampler has the advantage over conventional
cascade impactors of a sharper size fractionation. The
particle re-entrainment problem, i.e., carry-over of large
particles to lower stages known to occur with Anderson
samplers, is avoided. In addition, the smaller size of the
filter collection area is much more amenable to the intended
subsequent analysis.
D. Literature Surveys
A literature review is being,conducted on the
physical and chemical properties of plutonium containing
particles in the environment. Those publications available
are listed in Appendix C.
An extensive literature survey on the physical
and chemical characteristics of environmental iodine-129 has been
conducted and a report summarizing this review will be
published separately.
-------
11
V APPLICATION TO ROAP 21AMI. TASK 18
The subject task calls for, (a) developing methodology
for characterizing individual particulates in the environ-
ment, and (b) defining the shape, density and specific activity
of plutonium particulates which are airborne, in soils, and on
plants. Thus the physical and chemical charac-
terization work called for under these tasks is quite
similar to the requirements of ROAP 21BAS, Tasks 03,.04 and
13. Only the nature of the samples differs. ROAP 21BAS will
require airborne samples collected at or in the vicinity of
nuclear facilities. ROAP 21AMI, in addition, calls for
soil and plant samples collected from the environment. However,
the effort to this point has concentrated only on developing
the methodology for isolating and characterizing individual
particles, and such work could most easily be performed
using air filter samples. Thus, the reports for tasks in both
ROAPs have been combined.
During FY-75 soils and plant samples will be collected
simultaneously and at the same location that air samples
are being taken. These samples will also be submitted for
analysis under the contract with GE Vallecitos Nuclear Center.
Concurrent sampling will allow a comparison of plutonium
containing particulates isolated from soil, plants, and air.
-------
APPENDIX A
PROGRESS REPORT FOR ROAP 21AMI - TASK 17
DEVELOPMENT OF METHODOLOGY FOR DETERMINATION OF PHYSICAL
CHARACTERISTICS OF AIRBORNE PARTICLES CONTAINING PLUTONIUM
by
A. J. Cummings, Dr. S. C. Black,
and E. W. Bretthauer
July 3, 1973
National Environmental Research. Center-Las Vegas
Office of Research and Monitorings
United States Environmental Protection Agency
Las Vegas, Nevada 89114
-------
TABLE OF CONTENTS
gage
Table of Contents i
Illustrations ii
I. INTRODUCTION 1
II. DEVELOPMENT OF PROCEDURE 1
A. Detection 1
1. Autoscintography 1
2. Alpha Count 2
B. Resuspension 3
1. Refiltration 3
2. Visual Observation, Autoradiography, Removal and
Alpha Count 3
C. Characterization 4
1. Size Determination 4
2. Specific Activity 4
3. Mass/Density Measurement 5
4. Electron Probe and X-Ray Diffraction 5
a. Debye-Scherrer X-Ray Powder Diffraction Method . 5
b. Electron Microprobe 6
III. STEPWISE PROCEDURE 7
IV. SUMMARY 7
V. REFERENCES 8
VI. ILLUSTRATIONS 9
-------
LIST OF ILLUSTRATIONS
»
1. Process Flow Chart
2. Air Sample Filter
.3. Autoradiograph Sandwich
4a. Autoradiograph of 15 cm Filter
4b. Autoradiograph of Plutonium Particle in Solution
5a. Typical Large Particles
5b. Large Particle Before Fracture
5c. Large Particle After Fracture
5d. Stereo Pair; Copper Particle
6a. Microscopy Facility
6b. Microscope and Micromanipulator
7. Tooled Particles
ii
-------
PROGRESS REPORT FOR ROAP 21AMI - TASK 17
*
DEVELOPMENT OF METHODOLOGY FOR DETERMINATION OF PHYSICAL
CHARACTERISTICS OF AIRBORNE PARTICLES CONTAINING PLUTONIUM
by
A. J. Cummings, Dr. S. C. Black,
and E. W. Bretthauer
I. INTRODUCTION
Plutonium activity can be detected in air samples taken in areas where
the soil has been contaminated with plutonium. The possibility that this
resuspended plutonium represents a hazard on inhalation depends, primarily
on the respirable characteristics of the particles.
The basic problem is to determine the physical characteristics (size,
shape, density, mass, distribution, specific activity, etc.) of airborne
debris bearing particles or chemical combinations of plutonium isotopes.
The method we have developed can be broken down into three categories:
(1) detection, (2) separation, and (3) characterization. It was developed
for examination of microsorban filters obtained from high velocity impact
air samplers located at the Nevada Test Site (NTS). These filters have a
retentivity of 100% for particles of three microns or larger.
The work reported herein describes background activities and the pro-
cedures developed for characterization of individual plutonium containing
particulates collected from air samples.
II. DEVELOPMENT OF PROCEDURE
The procedure developed is described below and flow-charted in Figure 1.
Section III contains the stepwise procedure.
A. Detection
1. Autoscintography
A typical fifteen-centimeter impacted filter is shown in Figure
2. The first step is to produce an autoradiograph of the filter to determine
the location of radioactive particles. The autoradiograph is produced oh
-------
a photographic emulsion thru light emission generated by alpha-particle
«
bombardment from the plutonium upon zinc sulfide (ZnS) crystals. A sand-
wich is made of (1) the air filter, (2) a sheet of ZnS, and (3) a photo-
(1 2}
graphic emulsionv ' '. This sandwich is then enclosed in a light-tight
package and left for a period of time (see Figure 3). The exposure time
is determined by the light sensitivity of the emulsion and the radio-
active strength of the particle. Little has been done as yet to optimize
this step of the process. Typical particles require 21 days of exposure
when Kodak X-ray type film is used. This time has been reduced to a one-
to-two day exposure using fast film such as Kodak Royal Pan (ASA 400)
There is sufficient background of data to determine gross activity levels
r\ §
at this step ' ; however, additional work must be done. Recordings of
film density as a function of known activity levels would have to be made.
This would require acquisition of a densitometer and particles of known
size and activity. Then, for various film types, a study would be made
of the film grey scale as a function of radioactivity level. The most
difficult step would be in obtaining known, fractional nanocurie plutonium
samples and a densitometer of fractional micron spatial resolution. A
preliminary calibration attempt is shown in Figure 4b. This autoradiograph
represents a drop of 5,000 dpm plutonium solution. The solution consists
of particles of 0.1 to 0.3 micron diameter in suspension. The exposure
was on Kodak Royal Pan film for 16 hours. The activity is so great that
it is impossible to determine the location of a single particle. Discrete
points are visible; however, the number of particles per point has not
been determined. We are attempting to refine this approach by depositing
a small amount of the solution on an electron microscope grid. Observation
and autoradiography of the grid may allow determination of spot size for
a single particle.
The radiograph from the above step is then examined for
activity. Figure 4a shows the results of a typical exposure with three
points of activity readily seen.
2. First Cut and Count
The area of interest containing the source of radiation is
removed from the air filter for further processing. A circle of
-------
approximately 1 cm in diameter centered on the particle is cut from the
sample with a cork borer and subjected to alpha spectrometry. The alpha
count at this step is included only to determine whether or not the
particle is contained in the. filter aliquot. Typically, particles are
embedded in the filter material and give a distorted spectrum when counted
at this point. If the count shows activity, the filter is prepared for
visual microscopic observation, photography, and resuspension.
B. Resuspension
1. Refiltration
The cut sample from step A is dissolved in reagent grade carbon
tetrachloride and refiltered onto a 2.5 cm, 0.3 micron micropore filter
(preliminary attempts at fractional filtration have been made but were
found to be unnecessary since the same results are achieved by going
immediately to the smallest pore size filter).
2. Visual Observation, Autoradiography, Removal and Alpha Count
The second filtered sample is now observed visually through a
light microscope and particles of size 20 microns and larger are photo-
graphed and removed to a glass microscope slide for analysis. The filter
is then set up for a second autoradiograph to locate remaining radioactive
particles. Figure 5a shows typical particles removed at this stage. Con-
siderable difficulty has been encountered with fracturing of these large
particles into small (-5 micron) fragments (Figures 5b and 5c). We have
found it possible to obtain stereophotographs of the larger particles.
The stereophotos, however, are of only minor interest due to the shallow
depth of field inherent in microscope lenses. Figure 5d is a stereopair
of a copper particle. When properly viewed, some depth of field is seen.
Removal of the particles is aided through the use of a Sensaur
Pneumatic micro-manipulator and Zeiss photomicroscope (see Figure 6).
After removal, they may be subjected to X-ray diffraction, electron probe
analysis and alpha spectroscopy. The analytical instruments require the
particle to be attached to a glass probe. Figure 7 shows some such particles.
The probe is formed from a pulled glass rod. A short, thin section of the
pulled glass is waxed into a fine capillary tube and mounted in the
-------
micro-manipulator head. Rubber cement is added to the probe tip and the
particle picked up from the filter paper. The chosen particle and probe
tip are deposited on a microscope slide by melting the wax on the capillary
tip.
The second autoradiograph is developed and examined for
activity. Those portions showing activity are then subjected to the same
process of observation, photography,and removal as described above.
C. Characterization
1. Size Determination
An estimate of particle size can be made from visual observa-
tion through the microscope. A calibrated grid reticle is available for
use in the eyepiece. Alternately, size can be compared to glass spheres
or objects of known diameter. Photographs of known size particles or grid
scales can be stereoscopically superimposed over particle photographs to
estimate size. Due to particle irregularities such measurements are only
rough estimates. A review of the literature shows that particle size can
be related to autoradiography spot diameter ' ' . This, however, is true.
only for particles of pure elements. This diameter could be roughly deter-
mined visually through the microscope. There is a recording electrophoresis
densitometer available for use, although it has not been tested for resolu-
tion in the micrometer range. We will evaluate several types of film for
spot size versus radioactivity to correlate with other work. Size deter-
mination will then be based on visual and autoradiography spot size measure-
ments.
2. Specific Activity
Specific activity is defined as radioactive disintegrations
per unit time per unit mass. This measure has a twofold application as
it may be applied to either gross alpha counting or alpha spectroscopy.
The latter case requires a determination of the various alpha emitters
present on or in a particle. The parameters of the spectrometer, i.e., resolu-
tion and counting efficiency, allow relation back to the energy and type
of the radionuclides. .Then, since the specific activity of these nuclides
is known to a good degree of accuracy^ ', the mass of each nuclide present
-------
may be calculated. These individual masses have further significance to
be considered in £he section II C 3 (Mass/Density Measurement).
The relation of specific activity to mass as determined by
gross counting (no isotope identification) technique is quite different.
These data will be used to determine aerodynamic and inhalation character-
istics of particles and to facilitate calculation of radiation dosage from
inhalation of a given volume of air.
3. Mass/Density Measurement
The specific activity and alpha spectroscopy measurements dis-
cussed previously allowed a determination of the amounts and types of
radionuclides. These can be related to total particle mass, assuming the
nuclides to be attached to an unknown substance, through electron probe
and X-ray diffractometer analysis. These measurements can give an estimate
of the constituents of a particle and relative percentages. The three
measurements then combine to determine the make-up of a particle as to
types of element, amount of each and total particle weight. Density is
then determinable from weight and size. A second means of mass deter-
mination will be developed to supplement electron probe and diffractometer
measurements.
4. Electron Probe and X-Ray Diffraction
a. Debye-Scherrer X-Ray Powder Diffraction Method
The X-ray diffraction analysis of small particles necessi-
tates the use of a film method in order to integrate the intensity of the
diffraction arcs by the Debye-Scherrer Powder method.
The Debye-Scherrer camera used for particles is 57.3 mm
in diameter and 35 mm in width. The particle is mounted on a small glass
fiber with an appropriate adhesive by use of a micro-manipulator. The
fiber and particle are placed in a mount in the center of the camera and
the camera is loaded with a strip of non-screen X-ray film. The sample
is exposed to copper Ka X-radiation for a period of one to fifty hours.
If the particle is large enough and has a crystalline structure, the X-ray
film, upon development, will contain a series of diffraction arcs. The
position and intensity of the arcs are used to determine the crystalline
-------
structure and relative amounts of elements. The crystalline structure
and the elemental analysis will usually indicate the chemical compound(s)
in the sample.
Limitations of the Debye-Scherrer method when used for
particles are:
1. The particle must be large enough (10-20 microns
depending upon the sample) to produce a diffraction pattern.
2. A sample containing a large amount of iron will have
a high background due to copper Ka induced fluorescence from the iron.
3. Quantitation is not possible because this laboratory
does not have a densitometer.
b. Electron Microprobe
The electron microprobe yields qualitative and quantitative
information on areas one to fifty microns in diameter on a sample surface.
The information is obtained by bombarding a sample under vacuum with a
focused electron beam to produce characteristic fluorescence X-rays from
the elements in the sample. The X-rays energies are determined by energy
dispersive techniques in a single crystal goniometer containing a thin
window gas-flow proportional counter. The data for qualitative analysis
are collected on a strip chart recorder in units of goniometer degrees
versus peak height in counts per second. The goniometer values in degrees
plus the known 'd' value of the analyzing crystal in the goniometer applied
to the Bragg equation gives the X-ray energy. The total spectrum and
associated peak heights indicate the type and quantity, respectively, of
elements in the sample.
The limitations of the probe are:
1. The sample must be of low volatility.
2. The minimum size particle is about two microns in
diameter.
3. The sample must be optically flat for quantitation.
-------
III. STEPWISE PROCEDURE
The step-by-step procedure thus far developed is listed below.
A. Large Filter Autoradiograph
B. Removal of Active Areas
C. Dissolution and Refiltration of Each Active Area
D. Separate Large Particles from Filtrate
1. Large Particles
a. Microscopic Observation and Photography
b. Alpha Spectrescopy
c. Electron Probe and X-Ray Diffractometer Analysis
2. Filtrate
a. Autoradiography
b. Microscopic Observation and Photography
c. Removal
d. Alpha Spectroscopy
e. Electron Probe and X-Ray Diffractometer Analysis
E. Analysis of all of the above data to determine types of nuclides
present and the size and shape of particles bearing this nuclide.
IV. SUMMARY
Some success has been experienced in the characterization of particles
containing plutonium. We have found it possible to locate the gross position
of particles by autoradiography and further to observe and handle these
particles. These techniques have been developed through a cooperative
effort by the EPA-NERC-LV staff, particularly Mrs. Betty Mitchell and
Mr. Dale Modine. Further effort is required in the areas of autoradiography,
electron probe, and X-ray diffraction before final results can be tabulated.
Preliminary features of the particles characterized will be published in a
subsequent report.
-------
V. REFERENCES
1. Hsieh, J., F. Hungote, S. Wilson, (1965) "Autoradiography:
Technique for Drastic Reduction of Exposure Time to Alpha
Particles," Science, Vol. 150, p. 1821.
2. Rogers, A. W., (1967) Techniques of Autoradiography,
Elsevier Publishing Co.
3. Ferron, G. H. and E. Hyatt, (1970) "Size-Selective
Sampling of Plutonium and Uranium Aerosols," American
Industrial Hygiene Association Journal, p. 282.
4. Kelkor, D. N. and P. Joshi, (1970) "Size Determination
of Airborne Plutonium Particles by Autoscintography,"
Health Phvsics. Vol. 19, p. 529.
5. Vaone, J., E. de Ras, and Chr von Brandenstein, (1971)
"Autoradiography as a Help for Analyzing the Distribution
of Alpha-Active Isotopes in the Human Body after an Air
Contamination," Joint Nuclear Research Center, Karlsruhe
Establishment - Germany.
6. Goldstein, G. and S. Reynolds, (1966) "Specific Activities
and Half-Lives of Common Radionuclides," Nuclear Data A,
Vol. 1, No. 5, p. 43, July 1966.
-------
Large Sample
Autoradiograph
Large Particles
Observation
Photography
Removal
Dissolution:
Refiltration
Filtrate
Autoradiography
Observation
& Photography
Removal
Count
X-Ray Diffraction
Removal
Count
Electron Probe
Analysis
Figure 1
Process Flow Chart
-------
,
'
^
jj*.' ' ' ''''
s
.iffT.i
. , :
..
: - '
' , '
: -' \
!
^V**-*^-
rf>*^ "««.._ .i
^x,
> % "^L
X "'
\ vf
a, '
Figure 2
Air Sample Filter
-------
Figure 3
Autoradiograph Sandwich
-------
Figure 3
Autoradiogfaph Sandwich
-------
Figure 4a
Autoradiograph.of 15 cm Filter
-------
.
.
.
,
.
Figure Ab
Autoradiograph of Plutonium Particle in Solution
-------
, . .
.' - -
Figure 5a
Typical Large Particles
-------
Figure 5b
Large Particle Before Fracture
-------
»
*'
..
.
* jtk«A -
Figure 5c
Large Particle After Fracture
-------
. s
>
\.
V
Figure 5d
Stereo Pair; Copper Particle
-------
Figure 6a
Microscopy Facility
-------
,>w-"isr--.;*.* m *"₯
.r E *II-L _
^.ji|K^B*8*' '-*-*
, U| > k.
J^]!!lJ? f
m^iiiitn.-*^ V- .^ ' ' '"
V -
\ ^V^TaaBSB^y.
.-._iArV^jSi»^'^^(cii'i««S»ti*U^^^'"' ! .--
Figure 6b
Microscope and Micromanipulator
-------
Figure 7a
Tooled Particles
-------
>
'\
.
f.
Y
V
\
-
.
.
'
Figure 7b
Tooled Particles
-------
APPENDIX B
PRELIMINARY REPORT ON THE
CHEMICAL AND PHYSICAL PROPERTIES OF AIRBORNE PLUTONIUM
PARTICLES AT THE NEVADA TEST SITE
E. W. Bretthauer, P. B. Smith, A. J. Cummings,
G. B. Morgan, and S. C. Black
INTRODUCTION
Knowledge of the physical and chemical characteristics of
airborne plutonium particles is necessary to accurately assess
the biological availability of this radionuclide in the environs
of the Atomic Energy Commission's Nevada Test Site (NTS). There
has been much speculation as to the chemical forms and size of
airborne plutonium at the NTS; however, there appears to be
little published data to support these speculations. This pre-
liminary report suggests that there are at least four physical/
chemical forms of airborne plutonium, that most of the plutonium
particles would reach the alveoli, and that at least one of the
physical/chemical forms may become more biologically available
with time.
PROCEDURE
Sample Collection:
Microsorban filters with a collection efficiency of 100% for
particles greater than three micrometers diameter were used to
sample airborne plutonium particles in Area 11 of the Nevada Test
Site. The sampling rate of each air sampler was approximately
3
0.5 m per minute, each sampler was positioned vertically one
meter above the ground facing the explosion site of a previous
safety shot.
-------
Sample Analysis:
An autoradiograph was made of several microsorban filters by
sandwiching it between pieces of x-ray film which were subsequently
developed to determine the general location of the alpha-active
o
particles. A 6.5 cm section from a single filter containing
alpha-active particles was subsequently cut out and processed in
freon in an ultrasonic bath to separate the particles from the
filter material. These particles were spread out on cellulose
nitrate film, which was exposed for 72 hours and then analyzed
by track etch techniques for alpha tracks to quantitate the alpha
activity per particle. Thirty-two of these particles were selected
at random and sized by optical microscopy: Mass spectrometric
and electron microprobe analyses were performed on twelve of the
sized particles.
RESULTS
The resultant tracks on the cellulose nitrate film indicated
that there were at least 55 alpha-active particles present in the
o
6.5 cm sample. The results obtained by optical microscopy
and alpha track counting are shown in Table I. These results
indicate that the observed size range of the particles was <0.5
to 17.0 ym, and that the gross alpha activity ranged from 4 to
260 fCi/particle.
Results of the mass spectrometric and electron microprobe
analyses of the particles are shown in Table II. The data reveal
the presence of at least four classes of particles. The first class
(I) included the relatively small, high-activity particles composed
-------
of plutonium-uranium oxide, which were included in an organic
matrix. Previous experience with this type of particle in this
laboratory indicated that the organic matrix was extremely fragile
and fractured with the slightest manipulation.
The second class (II) included the larger, lower-activity
silicate particles in which plutonium was heterogeneously dis-
tributed in the particle in percentages too small to detect by
electron microprobe.
The third class (III) included the relatively large, low-
activity organic particles in which plutonium was also hetero-
geneously distributed with a concentration of <1%.
The fourth class (IV) includes the relatively small, high-
activity oxide particles in which the plutonium was homogenously
distributed throughout the particle.
DISCUSSION
Due to the extreme fragility of Class I particles, it may
be inferred that various meteorological phenomena such as wind,
rain, freezing, and thawing may cause this class of particles to
be easily fractured resulting in smaller particles which may be
both more respirable and more subject to redistribution with time.
From the results of the 32 particles analyzed, approximately
90% are less than 10 Pm diameter. When plotted on log-probability
paper the geometric mean diameter appears to be 1.5 ym.
A plot of alpha activity versus size yields a.scatter diagram
suggesting that plutonium is not homogenously distributed in these
air filter samples. Another approach to this apparent discrepancy
-------
is to use the specific activity concept. The particle with the
highest activity is 50% Pu (Table II). Because of the large dif-
ference in the half-lives of plutonium and uranium, essentially
all of the alpha activity is assumed to be due to plutonium.
For particle #805:
Volume = 310 ym3
Diameter = 8.2 ym
Activity = 261 fCi
Pu-239 Specific Activity = 6.13 x 10~2 Ci/g
Density (assumed) = 11.5 g/cm
Calculated Values of Mass and Volume are:
Mass of Pu = (2.61 x 10~13 Ci)(6.13 x 10~2 Ci/g)"1 =
4.26 x 10~12 g
Volume = (4.26 x 10~12 g)(11.5 g/cm3)"1 =
3.07 x 10~13 cm3 = 0.307 ym3
The calculated volume is about 1/1,000 the observed volume suggesting
that most of this particle is something other than plutonium.
With a geometric mean diameter of 1.5 ym, the particles
should be respirable ^ ' . A calculated aerodynamic diameter
based on this mean value is
% -1
Da = (P) V~ = (density) (geometric diameter)
Da = (11.5)^(1.5) = 5 ym
* A 5 ym diameter was -set in this report as the upper limit on
respirability.
-------
239
The maximum allowable exposure to soluble Pu in air
as set by the AEG can be calculated as follows:
(4)
Concentration guide (CG) limit =
2 x 10~12 pCi/cm3 = 2 pCi/m3
Reduced CG = 6 x 10"1 yCi/cm3 = 60 fCi/m3
Standard week = 168 hours
Work week = 40 hours
Breathing rate, standard week = 140 m /week
o
Breathing rate, work week = 33.3 m /week
Average activity of particles (GE data) = 46 fCi/particle
o o q
a) limit for Pu in pCi/week
L = (2 pCi/m3)(33.3 m3/week) = 67 pCi/week
b) for the average activity of 46 pCi/particle, this
limit in number of particles is
N = (6.7 x 104 fCi/week)(46 fCi/particle)~ =
1457 particles/week
c) reducing the CG by a factor of three for a suitable
population sample gives
Lr = (6 x 10" 2 pCi/m3)(33.3 m3/week) - 2 pCi/week
Nr = (2 x 103 fCi/week)(46 fCi /par tide) ~1 = 43 par tides/week
d) the particle inhalation rate at the reduced CG limit is
3 -1 3
R = (43 particles/week)(33.3 m /week) = 1.3 particles/m
Assuming a retentivity of 50%, the average person would inhale
2 pCi/week and retain 1 pCi/week.
-------
The air sampler used to collect these particles operated
o
for 24 hours at 0.56 m /min and,therefore, filtered particles from
3 ?
806 m of air. Based on 8.5 alpha-active particles per cm , the
o
total filter contained about 1,500 particles or nearly 2 particles/m ,
On the basis of the above calculation, this is about equal to the
reduced AEC CG.
ACKNOWLEDGMENT
The authors wish to thank the Environmental Sciences
Department, Reynolds Electrical and Engineering Company, Inc.,
Las Vegas, NV, for contributing the air filters; and the Advanced
Technology Division, General Electric Co., Vallecitos, CA, for
analyzing the particles.
-------
Table I
Size ar.d Activity of Participates
Particle
Uu-ber
101
102
103
104
. 105
106
107
108
109
110
111
112
113
114
115
116
118
119
120
Diameter Gross Alpha
(vn) Activity
(fCi/particle)
-------
121
122
124
125
126
138
802
803
804
805
806
807
808
1.5
1.0
17.0
<0.5
<0.5
2.5
3.5
8.5
3.0
8.2
2.5
3.2
3.0
09
16
52
06
06
104
52
10
143
261
£5
78
21
-------
Table II
Chemical and Physical Forns of Particulates
*
Particle Composition of Particle Description of Particle Class
Nunber Containing riutior-iun
804 48% Pu, 33% U, 19% 0 <0.5 Via oxide particle in I
an organic natrix whose
diaceter is 3.0 Vm
806 48% Pu, 33% U, 19% 0 <0.5 vm oxide particle in I
. an organic r.atrix whose
diameter is 2.5 vz
805 50% Pu, 31% U, 192 On <0.5 wa oxide particle I
in an organic natrix
whose diaaeter is 8.2 y:s
123 14% Si, 5% .U, 3S% 0 , 34% Fe Silicate whose diameter' II
is 6.0 pi
803 ' 24% Si, 7% Al, 45% 0,, 9% Fe, Silicate whose dianeter II
8% K is 8.5 wn
124 31% Si, 4% Al, 47% 00, Silicate whose dianeter II
12% Fe, 2% Mg, 2% Ti" is 17.0 yn
112 \ 29% Si, 9% Al, 43% 00, 4% Hg, Silicate whose diameter II
3% Fe, 3% K, 1% Ca "" is 8.8 pn
120 97% C, 2% 0 Organic whose diar.eter III
is 11.5 Pa
113 95% C, 3% Si, 1% Al Organic whose diaaeter III
. is 8.0 vn
808 38% Pu, 22% U, 22% 0 , 14% Al, Oxide whose dianeter IV
1% Fe 2 is 3.0 vn
138 45% Pu, 21% U, 23% 0 , 10% Al Oxide whose diameter IV
is 2.5 pm
802 3% Pu, 79% U, 17% 0 Oxide whose diameter IV
is 3.5 vm
-------
REFERENCES
1. Fish, B. R. (Ed), (1967) Surface Contamination, Pergamon Press,
PS 13.
2. Fish, B. R. (Ed), (1967) Surface Contamination, Pergamon Press,
PS 75.
3. Mercer, T. T., (1973) Aerosol Technology in Hazard Evaluation,
Academic Press, PS 315.
4. AEC Manual Chapter 0524, (1968) "Standards for Radiation
Protection," Annex I.
5. AEC Manual Chapter 0524, (1968) "Standards for Radiation
Protection," Annex I, Part II, Sect. II, B.2.c.
-------
APPENDIX C
LITERATURE SURVEY - Plutonium Particulates
1. Nathans, M. W. and W. D. Holland, (1971) Analysis of 239Pu
Particles Collected Near the Rocky Flats Facility, Final
Report submitted to HASL, USAEC, NY Office, Contract No.
NY-72-1915, Trapilo/West - Division of LFE.
2. NAEG, (1973) "Distribution and Inventory - A Program Element
of the NAEG," NAEG Progress Report No. 1 (Draft).
3. Heft, R. E. and W. A. Steele, (1968) "Procedures for
Separation and Analysis of Radioactive Particles from Nuclear
Detonations, Lawrence Radiation Laboratory - UCRL-50428. TID-
4500, UC-48.
4. Tamura, T., (1973) "Distribution and Characterization of
Plutonium in Soils from NTS," Presentation at AEC Meeting,
Las Vegas, Nevada.
5. Romney, E. M., H. M. Mork, and K. H. Larson, (1970) "Persistence
of Plutonium in Soil, Plants, and Small Mammals," Health Physics,
Vol. 19, pp 487-491.
6. Poet, S. E. and E. A. Martell, (1974) "Reply to 'Plutonium-239
Contamination in the Denver Area1 by Krey," Health Physics,
Vol. 26, pp 120-122.
7. Noshkin, V. E., (1972) "Ecological Aspects of Plutonium
Dissemination in Aquatic Environments," Health Physics, Vol. 22,
pp 537-549.
8. Romney, E. M. and J. J. Davis, (1972) "Ecological Aspects of
Plutonium Dissemination in Terrestrial Environment's," Health
Physics, Vol. 22, pp 551-557.
9. Poet, S. E. and E. A. Martell, (1972) "Plutonium-239 and
Americium-241 Contamination in the Denver Area," Health Physics,
Vol. 23, p 537.
-------
10. Krey, P. W. and E. P. Hardy, (1970) Plutonium in Soil Around
the Rocky Flats Plant, USAEC Report HASL-235.
11. Hammond, S. E., (1971) "Industrial Operations as a Source of
Environmental Plutonium," in Proceedings of Environmental
Plutonium Symposium, Report LA-4756, pp 25-35, Los Alamos
Scientific Laboratory, Los Alamos, New Mexico.
12. Krey, P. W., (1974) "Plutonium-259 Contamination in the
Denver Area," Health Physics, Vol. 26.
-------
Large Sample
Autoradiograph
Removal
Large Particles
Observation
Photography
Removal
Dissolution:
Refiltration
Filtrate
Autoradiography
Observation
& Photography
Removal
Count
X-Ray Diffraction
Count
Electron Probe
Analysis
Figure 1
Process Flow Chart
-------
Figure 2
Air Sample Filter
-------
Figure 3
Autoradiograph Sandwich
-------
Figure 3
Autoradiograph Sandwich
-------
Figure 4a
Autoradiograph-of 15 cm Filter
-------
Figure 4b
Autoradiograph of Plutonium Particle in Solution
-------
Figure 5a
Typical Large Particles
-------
I
Figure 5b
Large Particle Before Fracture
-------
m
0
\
Figure 5c
Large Particle After Fracture
-------
Figure 5d
Stereo Pair; Copper Particle
-------
Figure 6a
Microscopy Facility
-------
Figure 6b
Microscope and Micromanipulator
-------
Figure 7a
Tooled Particles
-------
Figure 7b
Tooled Particles
------- |