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

D.13
0.2.4 Dose Conversion Factors for System Analysis
The nuclear fuel cycle facilities in place and operating will change year by year. To
obtain a realistic assessment of the long-term population dose commitments, calculation of
the dose commitment from each year's operation followed by a summation of these yearly values
is necessary. This can best be assessed by deriving population dose commitment factors
for a one-year unit release.
Because of the nature of the three radionuclides involved in the world population dose
estimates ( 3 H, 14 C, and 85 Kr), there is no long-term accumulation in the body. Hence,
each year's release and resulting dose commitment can be treated independently of the
others.
The following expression relates the 70-year dose commitment (from a 1-year chronic
release) to the dose in the first year.
where
R = (1/x 2 ) Ati + exp(-xt 2) - exp (-XAt) (yr) 2
t I = 1 year,
t 2 = 70 years,
t = t 2 - t 1 = 69 years,
x = radioactive decay constant (1n2/half-life).
The values of this ratio for 3 H, 14 C, and 85Kr are given in Table D.2.
Table D.2.2 also includes the dose commitment factors per unit release obtained when these
ratios are applied to the first-year dose (item 1/1 from Table D.2.1).
Using these dose factors and annual releases of 3 H, 14C, and 85Kr from waste man-
agement facilities, estimates of worldwide population dose.can be obtained for the evolving
cycle systems.
TABLE D.2.2 70-Year World Population Dose Commitment
from a 1-Year Chronic Release, man-rem/70
years per Ci/yr released
Radionuclide Ratio ( a) Dose Commitment Factor(b)
H 17 - 3 8.2 x 10
14C 69 1.7 x 102
8 5 Kr 15 - 4 4.7 x 10
(a) Ratio of 70-year dose commitment from a 1-year chronic
release to the dose in the year of release.
(b) Seventy-year dose commitment to the world population
from a 1-year release of 1 Ci to the environment plus
continued exposure to the residual environmental
contamination.