?/EPA
United States
Environmental Protection
Agency
Environmental Monitoring
Systems Laboratory
P.O. Box 15027
Las Vegas NV 89114-5027
EPA 600/4-86-030
DOE/DP/00539-057
July 1986
Research and Development
Off-Site
Monitoring for
the Mighty Oak
Nuclear Test
prepared for the
U.S. Department of Energy
under Interagency Agreement
Number DE-A108-76DP00539
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o
EPA/600/4-86-030
OOE/DP/00539-057
July 1986
OFF-SITE MONITORING FOR THE MIGHTY OAK NUCLEAR TEST
by
Stuart C. Black, Allan E. Smith and Charles F. Costa
Nuclear Radiation Assessment Division
U.S Environmental Protection Agency
Las Vegas, Nevada 89114
v> prepared for the
^ U.S. Department of Energy
vy under Interagency Agreement
Number DE-A108-76DP00539
O
ENVIRONMENTAL MONITORING SYSTEMS LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
LAS VEGAS, NEVADA 89114
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NOTICE
This report has been reviewed in accordance with the U.S. Environmental
Protection Agency's peer and administrative review policies and approved for
publication. Mention of trade names or commercial products does not consti-
tute endorsement or recommendation for use.
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LIST OF ABBREVIATIONS AND SYMBOLS
ABBREVIATIONS
ICRP -- International Commission on Radiological Protection
1-131 radioactive iodine isotope, a radionuclide
MDC Minimum Detectable Concentration
yrem microrem = one millionth of a rem
mrem mi Hi rem = one thousandth of a rem
m^ cubic meter, about 35 cubic feet
pCi -- picocurie - unit representing 2.22 atoms decaying per
minute
rem unit of dose = 100 ergs per gram x modifying factors
Xe-133 radioactive xenon isotope, a radionuclide
m
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INTRODUCTION
The Mighty Oak event was a low-yield (less than 20 kt) test conducted in
the T-tunnel on the Nevada Test Site (NTS) on April 10, 1986. As with all
nuclear explosives tests conducted on the NTS, the Nuclear Radiation Assessment
Division deployed personnel and equipment in the area downwind from the test
location to measure any radioactivity which might be released as a result of
the test. The normal monitoring networks for detecting airborne or other radio-
activity were also operating. These networks and the operating procedures are
described in annual reports entitled "Off-Site Environmental Monitoring Report,"
the latest issue of which has the report number EPA-600/4-85-035.
During and immediately following the detonation of Mighty Oak, no radio-
activity related to that test was detected by the off-site radiation safety
personnel or by the monitoring networks. Following the Mighty Oak event the DOE
Test Controller notified the Nuclear Radiation Assessment Division (NRD) that a
ventilation procedure would be instituted within the next several days to purge
the tunnel of airborne radioactive materials so that personnel could re-enter
the tunnel to recover equipment and records. Ventilation or purging of a
tunnel involves the extraction of tunnel air with clean air make-up, filtration
of the extracted air through particulate and charcoal filters, and further dilu-
tion with clean make-up air prior to environmental release. As a result of
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this procedure, most of the radioactive noble gases in the tunnel air and a
very small fraction of other radionuclides are discharged into the atmosphere.
To more readily follow the steps in the purging procedures described
below, a schematic drawing of the outer portions of the tunnel is shown in
Figure 1.
PROCEDURES
Purging of the tunnel, when the amount of radioactivity contained therein
is high enough that it may be detectable off site, is performed only when the
wind will carry the radioactivity into unpopulated or sparsely populated areas
so that exposures will be as low as reasonably achievable. To insure this,
purging is performed only when meteorological data from the Weather Service
indicates an acceptable wind direction and speed. NRD is then notified of the
planned purging schedule so that special noble gas samplers and air samplers
equipped with particulate and charcoal filters can be placed in appropriate
locations to supplement the routine monitoring networks.
After the purging and requisite sampling period the noble gas and air
filter samples are collected and returned to the laboratory for analysis. The
noble gas and air samplers are re-started in place or moved to new locations as
necessary. The noble gas samples are analyzed for xenon-133 and krypton-85 and
the air filters are analyzed for gamma-emitting radionuclides (e.g. iodine-131)
by means of gamma spectrometry.
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MIGHTY OAK
T-Tunnel
(Not to Scale)
g Driftf
Protection
II Plug"""
Figure 1. Schematic diagram of a test tunnel
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TABLE 1. PURGING AND MONITORING SCHEDULE
Date
1986
04/16
Wind
Sector
Hiko-Rachel
Purging
Times - PST
1445-1500
Sampler
Locations
Medlin Rn. ,
Rachel ,
Hiko, Alamo
Comments
Relieved excess pres-
sure between Gas Plug
and Drift Protection
Plug.
04/22 Reed-Rachel 1000 4/22 to
1030 4/23
04/25 Rachel-Alamo 1030-1400
04/28
to
04/30
Rachel-Alamo
1000 4/28 to
0300 4/29
1030 to
1500 4/29
Twin Springs Rn.,
Hiko, Medlin Rn.,
Reed Rn. turn-
off, Pioche,
Penoyer Farm
Hiko, Glendale,
Penoyer Farm,
Twin Springs Rn.,
Medlin Rn.
Hiko,
Penoyer Farm,
Medlin Rn.
Purging of tunnel
between the Gas Plug
and Drift Protection
Plug.
Purging of the
tunnel behind the
Drift Protection
Plug.
Purging of the
tunnel behind the
Drift Protection
Plug.
04/30
to
05/5
05/5
to
05/09
Hiko to
Warm Springs
variable
1400 to
1800 4/30
1000 to
1930 5/1
0930 5/2 to
0520 5/4
continuous
after 1540
on 5/4
Hiko, Twin
Springs Rn.,
Penoyer Farm,
Medlin Rn.
Hiko, Twin
Springs Rn.,
Penoyer Farm
Purging of the
tunnel behind the
Drift Protection
Plug.
Purging of the
tunnel behind the
Drift Protection
Plug.
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The purging times and sampler locations are shown in Table 1 for the
period from April 16, the initiation of the purging, until May 9. Special
sampling was discontinued after May 9 following return of airborne xenon con-
centrations to background levels. Location of the special samplers and center-
line wind directions during purging are shown in Figure 2.
RESULTS
The results from the analyses of the special samples collected during the
purging are shown in Tables 2 and 3. Also operating during this time were the
routine Air Surveillance Network (ASN - 30 locations, Figure 3), the Noble Gas
and Tritium Surveillance Network (NGTSN - 15 locations, Figure 4), the Pressur-
ized Ion Chamber Network (PIC - 23 locations), and thermoluminescent dosimeters
at 127 locations. The PIC's are at all the NGTSN stations shown in Figure 4
plus Complex 1, Furnace Creek, Lathrop Wells, Nyala, Stone Cabin Ranch, Tikaboo
Valley and Twin Springs Ranch. These routine networks operate continuously
year round. Other than background levels of krypton-85, the only radioactivity
detected by these networks were xenon-133 concentrations of 36 and 38 pCi/m^ at
Rachel and Alamo, respectively, in 1 week samples collected April 23 through
April 30. Of all the samples collected the week ending May 9, only that col-
lected at Rachel (operated 4/30 to 5/7) had a detectable xenon concentration
(Table 2). This was most likely due to the purging from May 1 to May 4 since
no xenon was detected in the sample collected at Penoyer Farm, which is closer
to the NTS, during the period May 5 to May 9.
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N
Scotty't^
Cattle
n Routine Sampling Locations
A Special Sampling Locations
Figure 2. Special sampler locations and centerllne winds.
6
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TABLE 2. XENON-133 SPECIAL STUDY-MIGHTY OAK
Location
Alamo, NV
Reed Rn. Turnoff
Glendale, NV
Hiko, NV
Pioche, NV
Rachel, NV
Penoyer Farm
Medlin Rn.
(Tikaboo Valley)
Twin Springs
Rn.
Start
Day
04/09*
04/16
04/16*
04/23*
04/30*
04/22
04/25
04/16
04/21
04/25
04/28
04/30
05/05
04/22
04/09*
04/16
04/16*
04/23*
04/30*
04/22
04/25
04/28
04/30
05/05
04/16
04/22
04/25
04/28
04/30
04/21
04/25
04/30
05/05
Start Time
Hour
1030
1140
1150
1230
1145
1030
1200
1100
1300
1100
1030
1100
1130
1100
0930
1040
1015
1200
1000
1200
1000
1115
1245
1400
1130
0800
1300
1235
1130
1020
1000
1430
1500
Run Time
Hours
169
23
167
168
169
23
25
23
48
23
48
120
95
96
168
22
168
166
169
22
17
49
121
92
22
28
11
47
120
48
26
120
92
Result
pCi/m3
ND
ND
ND
38 ± 7
ND
81 ± 10
ND
ND
ND
270 ± 7
116 ± 20
ND
ND
ND
ND
ND
ND
36 ± 7
26 ± 8
23 ± 6
ND
210 ± 7
35 ± 7
ND
ND
ND
550 ± 15
120 ± 6
ND
ND
insufficient
124 ± 8
ND
*NGTSN samples
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Location
Alamo
Glendale
Hiko
Lathrop Wells
Medlin Rn.
Penoyer Farm
TABLE
4/17
GSN*
GSN
GSN
GSN
3. SPECIAL
4/23
GSN
GSN**
GSN
GSN**
GSN
4/26
GSN
GSN
GSN
GSN
GSN
GSN
AIR FILTER SAMPLES
4/30
GSN
GSN
GSN
GSN
GSN
Date Off
5/5 5/7
GSN
GSN GSN
GSN
GSN
- pCi/m3
5/8 5/5-5/9
1-131-
0.5
1-131-
0.2
1-131- 1-131-
0.10 0.9
1-131-
0.20
5/10
1-131-
1.2
1-131-
1.2
1-131-
1.9
Pioche
Rachel
Reed Rn Turnoff
Twin Springs
GSN
GSN GSN
GSN**
GSN** GSN
GSN GSN GSN GSN
GSN GSN GSN
1-131-
0.1
*GSN - gamma spectrum negligible
** - beryllium-7 detected, a natural radionuclide
NOTE: First detectable Chernobyl fallout found 5/7 in air samples from
Denver CO, Elko NV, Delta, Mil ford and Bryce Canyon UT, and in
snow from Mt. Charleston.
1-131
1.5
1-131
4.6
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Ely
Stone Cabin Rn.
Tonopah
Goldfield
0 Sunnyside
Blue Eagle Rn.
Nyala
(0
Twin Springs Rn.
TTR
Pioche
scony.jc,. _ « ^
,j Groom
Beatty- p">| ^^
X Site
Lathrop Wells*1M . ..
-i Indian
Salt Lake City
Delta
Milford
i Cedar City
St. George
Arizona
\ 'nflian «AOv rton
X Spnngs A i
Furnace Creek* PanrumpB m Jf Lake Mead
Death Valley Jet. \ La§ *\f**&
_. \ Vegas
Shoshone
l Community Monitoring Stations (15)
t Other Locations (15)
12/85
Figure 3. Air Surveillance Network stations (1985).
9
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12/85
Figure 4. Noble Gas and Tritium Surveillance Network sampling locations.
10
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SUMMARY AND CONCLUSIONS
During the purging procedure following the Mighty Oak event, special sam-
pling for radioactive noble gases and other airborne radioactivity was performed.
The location of the special samplers and their operating times were determined
from information supplied by the U.S. Weather Service and the Nevada Operations
Office, U.S. Department of Energy.
For the sampling periods indicated in Table 1, 33 samples were collected
and analyzed; 12 indicated the presence of low concentrations of xenon-133.
The maximum detected was 550 pCi/nv* for a sampling period of 11 hours at
Medlin's Ranch. This should be compared to the continuous exposure of 480,000
pCi/m3 which would be required to reach the annual whole-body dose limit of
100 mrem to a person in the general population as recommended by the ICRP. No
gamma-emitting radionuclides were detected on any air filter samples during
the period of the purging. The radionuclides shown in Table 3 starting May 8
originated from the reactor accident in the USSR (1-131 = iodine-131).
Ruthenium-103 was also detected in some of these early samples.
To estimate the whole-body dose from exposure to the measured xenon con-
centrations listed in Table 2, the air concentration (pCi/m^) is multiplied by
the collection time and summed for each site. This sum is then multiplied by
a dose conversion factor of 2.4 x 10"5 yrem/(pCi-hr/m3) to yield a whole body
dose for that location. The dose conversion factor is determined by dividing
the annual whole body dose limit (in yrem) by the product of 480,000 pCi/m3
(the Derived Concentration Guide calculated using the International Commission
11
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of Radiological Protection Report No. 30) and the number of hours per year
(8,766). This whole body dose is then compared to the ICRP whole body dose
limit of 100 mrem/yr (100,000 yrem/year) shown as %ICRP. These results are
shown below. As an additional comparison, the whole body dose at each location
is divided by the background dose rate to determine the extra minutes of equiv-
alent background (min. bkg.) exposure.
Site
Alamo
Hiko
Medlin
Penoyer Farm
Rachel
Twin Springs
Sum
(pCi-hr/m3)
6,350
11,780
11,640
15,030
10,370
13,920
Dose-
yrem
0.15
0.28
0.28
0.36
0.25
0.33
% ICRP
1.5 x 10-4
2.8 x 10-4
2.8 x ID'4
3.6 x 10-4
2.5 x 10-4
3.3 x 10-4
min. bkg.
0.7
1.5
1.0
1.3
0.9
1.2
The pCi-hr/m3 normalized to a daily integrated concentration, averaged
for the special samples, is plotted in Figure 5. Also shown are the start of
each purge period, the equivalent concentrations from the network shown in
Figure 3, and the minimum detectable concentration (MDC) during actual anal-
ysis. The plotted values are the results from analysis even though they might
be less than the MDC. The detectable concentrations at Alamo and Rachel pushed
the network average above the MDC for the period April 23 to April 30. The
increase in off-site concentration of xenon-133 from the purging reached a
maximum on April 25 and decreased to less than MDC after May 5.
In conclusion, the special monitoring for the tunnel purging following the
Mighty Oak test indicated that only xenon-133 was detectable in off-site areas.
No radioactivity attributable to Mighty Oak was detectable after May 5, 1986.
12
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0)
a
o
a
to
CO
CO
a>
X
103-
102.
Special Samplers
Network Samplers
Purging Periods
i Mill
Continuous
.I
MDC
I
4/10 15 20 25 30
Date: 1986
5/5
10
Figure 5. Integrated concentrations of xenon in Special and Routine
Network noble gas samples.
13
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The maximum radiation dose to an off-site resident, assuming that person remained
outdoors during the total sampling period, would have been 0.36 urem at Penoyer
Farm. This is equivalent to less than 1-1/2 minutes extra exposure to the back-
ground radiation at that location. All exposures to residents were negligible
fractions of both the ICRP guidelines for exposure of 100 mrem per year (ICRP77)
and the U.S. EPA guideline of 25 mrem/yr from airborne radionuclides (EPA85a).
REFERENCES
EPA85a U.S. Environmental Protection Agency, 1985, National Emission Stand-
ards for Department of Energy Facilities. 40 CFR 61 Subpart H,
published in FR:50, 5194, February 6, 1985.
EPA85b U.S. Environmental Protection Agency, 1985, Off-Site Environmental
Monitoring Report: Radiation Monitoring Around United States Nuclear
Test Areas, Calendar Year 1984, Environmental Monitoring Systems
Laboratory, Las Vegas, NV Report EPA/600/4-85-035.
ICRP77 International Commission on Radiological Protection, 1977, Recommenda-
tions of the ICRP, Pergamon Press, NY, Publication 26 (Revised 1983,
Publication 39).
ICRP79 International Commission on Radiological Protection, 1979, Limits for
Intakes of Radionuclides by Workers, Pergamon Press, NY, ICRP Pub-
lication 30.
14
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
DOE DP00539-057
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Off-Site Monitoring for the Mighty Oak Nuclear Test
5. REPORT DATE
June 1986
6. PERFORMING ORGANIZATION CODE
EPA 600/07
7. AUTHOR(S)
S. C. Black, A. E. Smith and C. F. Costa
8. PERFORMING ORGANIZATION REPORT NO.
EPA 600/4-86-030 July 1986
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Nuclear Radiation Assessment Division
Environmental Monitoring Systems Laboratory
U. S. Environmental Protection Agency
Las Vegas, Nevada 89114
10. PROGRAM ELEMENT NO.
X6EH10
11. CONTRACT/GRANT NO.
IAG DE-AI08-76DP00539
12. SPONSORING AGENCY NAME AND ADDRESS
Nevada Operations Office
U.S. Department of Energy
P. 0. Box 14100
Las Vegas. NV 89114
13. TYPE OF REPORT AND PERIOD COVERED
Response, Apr-May 86
14. SPONSORING AGENCY CODE
15. SUPPLEMENTARY NOTES
16. ABSTRACT
After a nuclear explosives test, code name Mighty Oak, the tunnel leading to the
test point became contaminated with radioactive debris. To re-enter and recover
valuable equipment and data, the DOE purged the tunnel air using particulate and
charcoal filters to minimize discharge of radioactivity to the atmosphere. During
this purging, the EPA established special air samples supplementing their routine
air monitoring networks. Analysis of the collected samples for radioactive noble
gases and for gamma-emitting radionuclides indicated that only low levels of
xenon-133 were released in amounts detectable in populated areas near the Nevada
Test Site. The maximum dose to an individual was calculated to be 0.36 microrem,
assuming that person remained in the open field at the measurement site during the
whole period of the purging.
17.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
18. DISTRIBUTION STATEMENT
RELEASE TO THE PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
16
20. SECURITY CLASS (This page!
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (R«v. 4-77) PREVIOUS COITION is OBSOLETE
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