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

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probability that the drill (0.5 m in diameter) will strike a waste canister is 0.005 per
drilling event, because of the relative cross sectional areas involved.
For dose calculations it is assumed that during drilling one-fourth of the waste in one
canister is circulated to the surface with the drilling mud, and the radioactive material is
uniformly distributed over 0.5 ha in the top 5 cm of the surface soil.
Table 5.5.10 lists the expected releases to air from contaminated surface soil. These
values are based upon 1) a resuspension factor of 0.011/yr 2) the assumption that one-fourth
of the radioactive material in the top 5 cm is available for resuspension and 3) that 0.10
of the material resuspended is respirable. The maximum individual is exposed, on the aver-
age, to the contaminated soil for 12 hr/day. Based on the releases given in Table 5.5.10
and methods of dose calculations presented in Appendix D, first-year doses and 70-yr doses
to the maximum individual who will reside and grow crops for his consumption on the con-
TABLE 5.5.10. Respirable Radionuclides Released to the
Atmosphere from Salt Repository Breach by
Drilling 1000 Yrs After Repository Closure, Ci
Radionuclide Spent Fuel HLW
14C(*) 1.7 x 10- 4 1.1 x 10o 6
- 5
- 4
126Sb 1.2 x 10 1.1 x 10
1 2 6 Sn 1.2 x 10- 5 1.1 x 10- 4
1291(*) 8.6 x 10- 6 7.4 x 10- 7
2 3 9 Np 3.4 x 10- 4 9.0 x 10- 3
2 4 0 Pu 1.1 x 10- 2
4.4 x 10- 4
2 4 1 Am 2.2 x 10- 2 3.2 x 10- 2
239u 7.3 x 10- 2 6.3 x 10- 4
(*) The bulk of the C and I is volatized during
dissolution of the spent fuel and stored in
separate containers and locations different
than those used for HLW in the repository.
For these two nuclides, 100% of the material
resuspended is assumed respirable.
taminated land were calculated. The first-year whole-body doses amounted to 13 rem for
drilling through a spent fuel canister and 19 rem for drilling through a HLW waste can-
ister. The 70-yr whole body doses were 9.4 x 102 and 1.4 x 103 rem, respectively.
The predominant mode of exposure is direct radiation(a) from contaminated soil and
as a consequence, dose to the various organs is substantially the same the first year.
During the 70-yr dose period the dose via the ingestion pathway increases substantially,
particularly in terms of dose to bone. The 70 year accumulated doses as calculated might
result in a small increase in risk of life shortening, contracting lukemia, etc.
(a) 2 4 1 Am is the principal contributor to the direct radiation dose. The dose from
breach of a HLW canister was reported in the draft Statement, and in supporting
documents, as about 100 times higher than here because an incorrect 2 4 1 Am inventory
was used.