Management of Commercially Generated Radioactive Waste - U.S. ...

103
CONSEQUENCE ANALYSIS
amount of radionuclides released to the atmosphere as given in Table 4.1.1-12 of DOE/ET-0029.
The amounts given in this table are based on release fractions given in Table 6.2.6 for acci-
dent number 6.2.8 in DOE/ET-0028. An examination of the release fractions and cask inven-
tories given in DOE/ET-0028 indicates that the amount of radionuclides given in DOE/ET-0029,
and hence the dose reported in Appendix N, are in error. There are three sources of error.
Mixed fission products and actinides have been excluded from the release, the amount of 85 Kr
released is underestimated, and the amount of 13 7 Cs released has been overestimated.
Finally, the following discussion shows that the amount of 13 4 Cs and 1 3 7 Cs released
for accident number 6.2.8 has been overestimated. The discussion on page 6.2.14 of DOE/ET-
0028 indicates that 6 x 10 -4 of the cesium inventory may be available for release as a
result of fuel rod perforation in a high temperature environment. This result is taken from
Supplement II to WASH-1238. According to Table 6.2.6 of DOE/ET-0028, the availability frac-
tion is divided in half between 13 4 Cs and 13 7 Cs. Table 3.3.8 of DOE/ET-0028 shows a cask
inventory of 1.7 x 105 curies and 9.4 x 104 curies per MTHM for 13 4 Cs and 137Cs, respectively.
Since a cask contains 4 MTHM, this results in 6.8 x 105 curies of 13 4 Cs and 3.8 x 10 5 of
137Cs in a cask. Applying the availability fraction of 3 x 10 - 4 for each isotope yields 204
curies of 13 4 Cs and 114 curies of 13 7 Cs available for release. Since in accident num-
ber 6.2.8, 50% of fuel rods are perforated, this results in 102 curies of 13 4 Cs and 57 curies
of 13 7Cs being released in this accident. Table 4.1.1-12 of DOE/ET-0029 shows 200 curies of
134 13 7
Cs and 110 curies of Cs being released. Perhaps the fact that only 50% of the rods
are perforated was not taken into account.
We recommend that the radiation dose to the maximum individual resulting from this
accident be reevaluated in light of the above comments. (208-NRC)
Response
This comment raises three main issues. First is that population doses have been omit-
ted from the discussion of severe accidents in the draft Statement. Second, population
densities used to evaluate radiological consequences of spent fuel accidents are inappro-
priate for accidents in urban areas. Last, release fractions used for a severe spent fuel
accident are in error. Each of these issues is discussed below.
The format used in the final Statement to discuss consequences of predisposal accidents
presents both maximum individual and population doses from umbrella source terms. A defini-
tion for umbrella source terms is given in Section 3.2.7 of this report. Transportation
accident impacts are described in Section 4.8.1.
The population density used for accident consequence analysis is 130 persons/km 2 and
is based on an average of populous U.S. regions. Population doses vary approximately lin-
early with population density. It higher population densities are assumed, high doses would
result. Current interim NRC rules prohibit the transport of spent fuel through highly pop-
ulated areas.