silo 3 - U.S. Department of Energy

E N 0 I N E E R I N GQP
Transport and Dose Calculation using CAPSI-PC
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Calculation Number:
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35H19605
40430-CA-0003
The atmospheric releasddispersiodexposure calculations were performed usin the annual estimated
release rates, Table 2, for the major radionuclides in the Silo 3 waste, includingg'QRn, 210Rn and =Rn.
Radionuclide concentrations and doses were calculated as a function of 16 uniformly distributed directions
and potential receptor/monitoring station locations of 332 m, 527 m, 582 m, 930 m, QQlm, 994 m, 1064 rn,
1241 m, 1320 rn, 1356 m, 1390 rn, 1454 m, 1457 rn, 1497 m. and 1506 rn from the stack. In addition, the
location of the maximum exposure and dose is determined.
Five CAP88-PC input files and execution runs were performed: 1) particulate releases during Phase 1,
and 2, and 2) specific radon isotope releases for each project phase. The calculated results are detailed
in ATTACHMENT C. The dose is not calculated for the initial headspace venting since the source term
released in negligible. T,h" initial 48 mCi release is less than the average released per - day -. during removai --
activities (e.g., 6.63 x 10 pCilmin or 95 mCilday)
The maximum exposure/dose occurs at a distance of 994 m from the stack and in the north-easterly
direction, for both the particulate and =Rn releases. Maximum exposure to *'Fin and =Rn occurs at
332 m in the north-easterly direction, which is closer to the stack release location relative to the particulate
and =Rn maximum exposure/dose location. This is due to the shorter half-life of 2'DRn (4s) and ='Rn
(55s).
Exposure of a hypothetical rural receptor, at 994 m northeast, to particulates resulting from the retrieval
and packaging of Silo 3 waste would yield an estimated dose of 6.40 x lo4 mrew during Phase 1, and
4.33 x lo4 mrem/yr during Phase 2. Dose rates due to isotopic radon that do not emanate from the solid
particulate matrii and is atmospherically dispersed were not evaluated and are considered to insignificant.
Thorium-230 is the largest contributor to risk. The 2?h concentration at the location of maximum dose is
approximately 2.6 x 10'" pCVL and 1.7 x 10'" pCVL, during Phase 1 and 2, respectively.
I
Radoq
The CAP-88 output for the release of various radon isotopes are shown in Attachment C3 - C8. The
maximum concentration and dose due to =Rn and daughters occurs at 994 rn from Silo 3 in the north-
easterly direction - The =Rn concentrations at this location are 1.5 x lo4 pCVL for both Phases 1 and 2.
The dose-rates due to pure radon inhalation are 0.033 mremEyr for both Phases 1 and 2.
The =Rn progeny dose is expressed in terms of working level, which is adjusted for a 31% equilibrium
fraction at 994 m. The working level (WL) concentrations for Phase 1 and 2 are 4.76 x lob at the
maximum exposure location. The dose for this working level can be correlated to dose assuming an 100%
exposure time duration outdoors by using the outdoor conversion factor of 570 mremMILM, where a
working level month, WLM, is 170 hours of exposure. Therefore, Phase 1 and 2 doserates are
Dose-rate for Phase 1 and 2 = 4.76 x lo4 WL x (8760 hrs/yr / 170 hrs/mo) x 570 mremMlLM
= 0.14 mremw.
The total dose-rate from =Rn and progeny for a receptor located at 994 m from Silo 3 in NE direction are:
Total dose-rate for Phase 1 and 2 = 0.033 + 0.14 = 0.17 mremlyr
The corresponding =Rn dose conversion factor is approximately 0.01 1 pCVL per mrem/yr at 31 percent
equilibrium, the assumed exposure durations, and at the stated dose conversion factor of 570 mrem
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