ML11207A068
| ML11207A068 | |
| Person / Time | |
|---|---|
| Site: | Washington State University |
| Issue date: | 07/18/2011 |
| From: | Wall D Washington State Univ |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| Download: ML11207A068 (9) | |
Text
WASHINGTON STATE
~tUNIVERSITY Nuclear Radiation Center July 18, 2011 Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
Reference:
Washington State University Docket No. 50-27, License No. R-76
Subject:
WASHINGTON STATE UNIVERSITY - SUPPLEMENTAL INFORMATION FOR THE WSU LETTER SUBMITTED ON JUNE 13, 2008 IN RESPONSE TO A REQUEST FOR ADDITIONAL INFORMATION REGARDING THE WASHINGTON STATE UNIVERSITY TRIGA REACTOR LICENSE RENEWAL Washington State University (WSU) has applied to renew operating License Number R-76 (Docket number 50-27). As part of the license renewal process, Washington State University submitted a letter on June 13, 2008 describing the outcome of an MHA accident. The present letter provides supplemental information for the MHA analysis.
I declare under penalty of perjury that to the best of my knowledge the foregoing is true and correct.
Date Executed 0 1 Respectfully Submitted, Donald Wall, Ph.D.
Director Ao,2-P.O. Box641 300, Pullman, WA 991 64-1 300 509-335-8641
- Fax: 509-335-4433
- www.wsu.edu/nrc A0O3-5
Introduction This analysis is a supplement to the MHA analysis submitted on June 13, 2008.
The purpose of this report is to provide an analysis of dose rates to members of the public who would be off-site during the course of a Maximum Hypothetical Accident (MHA) resulting in the release of volatile radionuclides. The type of release considered in this letter is a ground release that would occur when the reactor building ventilation system is in the "isolate" mode.
Approach The U.S. Nuclear Regulatory Commission (NRC) provides for a means to calculate atmospheric dispersion for ground level releases. U.S. NRC Regulatory Guide 1.145 provides the equations for atmospheric relative concentration (X/Q) to determine the off-site concentrations of radionuclides in air, which are used to calculate whole body and inhalation doses. Equations (1),
(2) and (3) are reproduced from Regulatory Guide 1.145, along with the explanation for their use.
_Z=_ 1 (1)
Q U10 (rrya z ++/-A/2)
X =_ 1 (2)
Q Uio(37rtoayz) z1 (3)
Q U10-ryC7z)
Where X/Q is the relative concentration in s/m 3, U is windspeed at 10 meters above the plant grade, in m/s, Yyis lateral plume spread, in meters, (a function of atmospheric stability and distance),
Gyy is the vertical plume spread,, in meters, a function of atmospheric stability and distance, I is lateral plume spread with meander and building wake effects, in meters, a function of atmospheric stability, windspeed, and distance [for distances of 800 meters or less, Yy = May, where M is determined from Figure 3 (in Regulatory Guide 1.145); for distances greater than 800 meters, y = (M-1)y, 800 m+ Gy. In this analysis, M =4].
The values for lateral and vertical plume (oy and Ty) spread are taken from Figures 1 and 2 from Regulatory Guide 1.145. The figures are reproduced in Appendix A at the end of this letter. The 1 of 8
values of both lateral and vertical plume spread from Figures 1 and 2 are based upon Pasquill turbulence type F, i.e. moderately stable, which is the most conservative of the diffusion models.
Instructions in Regulatory Guide 1.145 state that the X/Q should be calculated for equations (1) through (3). The higher values for equation (1) or (2) should be selected, and then compared with the value of equation (3); the lower value of the comparison with (3) should be selected for the X/Q value.
The value for equation (1) is:
z _ 1=1 =0.0104 Q U 10(7tUO'y z +A /2) (1) 2 .5)( 9 .5)+43.2]
7r:(
2j The value for equation (2) is x...1.0.00447 Q U i0(3nyYCT yz) (1)(3)nc(2.5)(9.5)
And the value for equation (3) is:
S= 1 = 1 -0.00335 Q U*0*--' y("z (1)(3.14159)(10)(9.5)
According to the criteria set forth in Regulatory Guide 1.145, a value of 0.00335 should be used for x/Q.
The volume of the WSU reactor pool room used in these calculations is I x 109 mL. Based upon a leak rate of 100 CFM (47,195 mL/s), it would require 21,189 seconds to empty the pool room.
This number is conservative because the pool room leak rate must be balanced by an inflow rate, which would mix fresh air with pool room air, resulting in continuous dilution and extending the time of the release of the radionuclide inventory in the pool room. The longer release time would result in lower off-site doses due to radioactive decay proceeding for a longer period of time during the course of a release. However, an unforeseen event that could act to increase the rate of release would be bounded by using a constant release rate, uncorrected for either dilution or radioactive decay. Doses that result from ground releases are not therefore release rate dependent, as the total dose is determined the product of dose rate and time, with larger dose rates corresponding to more rapid releases, but which are integrated over correspondingly smaller time intervals. The building is the source term. The downwind dose in the plume can be determined as described in the following section.
A leak rate of 100 cfm enters a volume of space outside the reactor building and is swept away by air movement which is conservatively set at 1 m/s. Since the building is the source term, the 2 of 8
100 cfm (47,195 mL/s) enters the volume outside the reactor building at a rate that is described by the building width x building height x 1 meter per second.
17.07 m x 8.53 m xl m/s where 17.07 m is the building width, 8.53 m is the building height, and 1 m/s is the wind speed.
This corresponds to a dilution factor of 30.85 of the plume upon leaving the building. In the cases of the inhalation and submersion doses the assumption is made that the member of the public is not evacuated and remains exposed to the plume during the entire time of passage of the plume. A constant release rate, uncorrected for radioactive decay, brackets all possible release rates because the time of exposure to the plume is a function of release rate, with shorter exposure times resulting from faster release rates. The distance to the closest occupied dwelling is 626 meters.
Table I provides the radionuclide inventory released into the pool room, as calculated by General Atomics (documented in a June 13, 2008 letter to the U.S. NRC) following failure of the fuel cladding of a single fuel rod. The fission product radionuclides Br-85, Br-87, Kr-89, 1-136 and Xe-137 are not used in the dose calculations because their short half-lives do not lead to exposure to the public.
Table I. Volatile Fission Products and Quantities Radionuclide Activity concentration at the Isotope released (mCi) Bg in ool rm source term (Bg/m 3)
Br-82 0.026 9.62 x 10' 0.312 Br-83 3.3 1.22 x 108 39.6 Br-84 6.4 2.37 x 108 76.8 1-131 17.8 6.59 x 108 213 1-132 26.8 9.92 x 108 321 1-133 41.3 1.53 x 109 495 1-134 47.6 1.76 x 109 571 1-135 38.7 1.43 x 109 464 Kr-83m 3.3 1.22Yx 108 39.6 Kr-85m 7.5 2.78 x 108 89.9 Kr-85 0.5 1.85 xl107 6.0 Kr-87 15.3 5.66 x 108 183 Kr-88 21.7 8.03 x 10" 260 Xe-131m 0.2 7.40 x 106 2.40 Xe-133m 1.2 4.44 x 107 14.4 Xe133 40.3 1.49 x 109 483 Xe-135m 7.2 2.66 x 108 86.3 Xe-135 27.5 1.02 x 109 33.0 Xe-138 39.1 1.45 x 109 469 3 of 8
The inhalation dose for a member of the public at the nearest occupied dwelling is given by:
Dose(Sv) = x DCF x Ax BR x t Where yi/Q is the factor that describes plume dispersion, DCR is dose conversion factor in Sv/Bq, A is concentration in Bq/M3of radionuclides in the plume at the point of exposure, BR is breathing rate of 3.3 x 10- 4 m3/s, and tis time in seconds-Table II provides the inhalation dose coefficients for thyroid and whole body exposure. The values for inhalation dose coefficients are taken from "Limiting Values of Radionuclide Intake And Air Concentration and Dose Conversion Factors For Inhalation, Submersion, And Ingestion", U.S. Environmental Protection Agency, EPA-520/1-020, September 1988. Table III provides the corresponding inhalation doses.
Table II Inhalation Dose Coefficients (Sv Bq1)
Whole Body Dose radionuclide Thyroid Dose Coefficients Coefficients Br-82 2.38 x 1040 3.31 x 10-1' Br-83 3.29 x 1012 2.33 x 10"1 Br-84 3.12 x 1012 2.61 x 10I1 1-131 2.92 x 10-7 8.89 x 10-'
1-132 1.74 x 10-9 1.03 x 1040 1-133 4.86 x 10-' 1.58 x .10-9 1-134 2.88 x 10-10 3.55 x 10-1 1-135 8.49 x 10-9 3.32 x 10-1' 4 of 8
Table III. Inhalation Dose Equivalent for Thyroid and Whole Body Exposure Radionuclide Thyroid (mrem) Whole Body (mrem)
Br-82 1.74 x 10-7 3.02 x 107 Br-83 3.05 x 10-7 2.23 x 105 Br-84 5.61 x 10-7 4.69 x 10."
1-131 0.146 4.45 x 10-3 1-132 1.31 x 10-' 7.75 x 10-5 1-133 0.056 1.83 x 10-3 1-134 3.85 x 10-4 4.75 x 10-5 1-135 9.23 x 10-3 3.61 x 10.4 TOTAL 0.21 0.00679 The air submersion dose for a member of the public at the nearest occupied dwelling is given by:
Dose(Sv) =j-xDCFxAxt Where x/Q is the factor that describes plume dispersion, DCR is dose conversion factor in Svom 3/Bqos, A is plume concentration in Bq/m3 at the point of exposure and t is the time of exposure in seconds.
Table IV provides the submersion dose coefficients for thyroid and whole body exposure. The values for submersion dose coefficients are taken from "EXTERNAL EXPOSURE TO RADIONUCLIDES IN AIR, WATER, AND SOIL", U.S. Environmental Protection Agency, EPA-402-R-93-081, September 1993. Table V provides the corresponding submersion doses.
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1!
Table IV Submersion Dose Coefficients (Sv m 3 Bq1 s-)
Radionuclide Thyroid Whole body Br-82 1.30x 1013 1.30x 1013 Br-83 3.80 x 10-l6 3.82x 10"6 Br-84 9.50 x 10-14 9.41x 10-14 1-131 1.81 x 10- 14 1.82x 10714 1-132 1.12x 10*13 1.12x 10-1 1-133 2.93 x 10-14 2.94x 10-14 1-134 1.30 x 1013 1.30x 1013 1-135 8.01 x 10-14 7.98x 10-14 Kr-83m 6.43 x 10-19 1.50x 10-18 Kr-85m 7.33 x 10-15 7.48x 1015 Kr-85 1.18 x 10-"6 1.19x 10-16 Kr-87 4.13 X 10-14 4.12x 10-14 Kr-88 1.03 x 1013 1.02x 10-13 Xe-131m 3.91 x 1016 3.89x 1016 Xe-133m 1.36 x 10-15 1.37x 10-15 Xe133 1.51 x 101" 1.56x 10-15 Xe-135m 2.04 x 10-14 2.04x 10-14 Xe-135 1.18 x 10-14 1.19x 10-14 Xe.-138 5.77 x 10-14 5.77x 10-14 6 of 8
C -
Table V Submersion Doses Equivalent for Thyroid and Whole Body Radionuclide Thyroid (mrem) Whole Body (mrem)
Br-82 8.59 x 10-5 8.59 x 10.
Br-83 3.19 x 10-5 3.20 x 10-5 Br-84 1.54 x 10.2 1.53 x 10-2 1-131 8.19 x I0.3 8.23 x 10.3 1-132 7.63 x 102 7.63 x 10-2 1-133 3.07 x 10-2 3.09 x 10-2 1-134 0.157 0.157 1-135 0.0788 0.0785 Kr-83m 5.39 x 10-8 1.26 x 10-7 Kr-85m 1.40 x 10-3 1.43 x 10-3 Kr-85 1.50 x 10-6 1.51 x 10-6 Kr-87 1.61 x 10-2 1.60 x 10-2 Kr-88 5.68 x 10-2 5.62 x 10-2 Xe-131m 1.99 x 10-1 1.98 x 10-'
Xe-133m 4.15 x 10-' 4.18 x 10-5 Xe-133 1.55 x 10-3 1.60x 10.'
Xe-135m 3.73 x 10-3 3.73 x 10-Xe-135 8.25 x 10-T 8.32 x 10-3 Xe-138 5.73 x 10-2 5.73 x 10-2 TOTAL 0.5119 0.5112 Conclusion The inhalation dose equivalent for thyroid and whole body exposures are 0.21 and 0.00679 mrem, respectively. The submersion dose equivalents for thyroid 'and whole body exposures are 0.5119 and 0.5112 mrem, respecti'ely. The dose equivalent values are much less than the 10 CFR 20.1301(a)(1) limit of 100 mrem total effective dose equivalent (sum of the deep-dose equivalent for external exposures and the committed effective dose equivalent for internal exposures). The dose rates are also less than 10 CFR 20.1301(2) of 2 mrem in any one hour. As a result, a ground release during the course of and following an MHA would not violate 10 CFR 20 limits for a member of the public at the nearest occupied dwelling who remained exposed during the entire time that would be required for the plume to pass.
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- 4 .
Appendix A.
Figures 1 and 2 from Regulatory Guide 1.145.
I0*
figure 1. Loteral d~ffusion witho~ut meander aund building waka effects, cry, vs..dvni-wuird distance fromn sourot, far Pasquil'5 turbuleneA tyP05 (nOspiherlo Aftbility l Ref. 71.
03 IC -- --- " fE, , ..
.*It *(I F
"*tX j-1. 1-1
- iZ:
[ 01/lIJ A-EXTREMELYUNSTASLE U
- ~~~ "---*t.,
- lmI I
~~ MODE-RoATELYrUNSTABLE
! 0 - SLIGHTLYUNSTA LE'I
.
i/~ . " -- NEWU'TL TR A
- EL -- _
J-: " iF - MODERATELY STILBLE*
10 5, It 5 2 5 tO1 ISA!2 5 to, 2 DISTANCE FROM SOURCE Wm Figure 2. Vertical diffusion without meander and building wake effects, 0'. vs. downwind distance from source for Pesquill's turbulence types (atmospheric stability) (Ref. 7).
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