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

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D.12<br />

The concentration during the next 40 years after the release has stopped is this 30th year<br />

concentration corrected for decay. Thus the total time-integrated concentration (TIC) is the<br />

sum <strong>of</strong> the combined expressions for concentration during the two time periods (0 to 30 years<br />

and 30 to 70 years). This yields the following equation:<br />

TIC = (2.53 x 10 - 7 ) (1/<br />

where<br />

2 ) [t1 + exp (-t 2 ) - exp(-At)1 (pCi*yr/m ) per Ci/yr released<br />

t I = time over which release occurs,<br />

t 2 = time over which dose is calculated,<br />

At = t 2 - t 1<br />

For t 1 = 30 years and t 2 = 70 years the expression within brackets becomes 448, which<br />

yields a time-integrated concentration <strong>of</strong><br />

1.13 x 10 - 4 pCi.yr/m 3 per Ci/yr.<br />

Unlike H and C, which emit only low-energy beta particles during their radio-<br />

active decay, 85Kr emits a gamma photon in a small percentage <strong>of</strong> its decays. These photons<br />

plus a small contribution from bremsstrahlung associated with the beta decay are<br />

capable <strong>of</strong> irradiating the whole body(a) during external exposure to 85Kr dispersed in air.<br />

Krypton-85 is not significantly absorbed into the body during inhalation, and this pathway<br />

makes a negligible contribution to the whole-body dose (NCRP 1975).<br />

Soldat et al. (1973) have calculated the whole-body dose factor for a person immersed<br />

in a half-infinite cloud <strong>of</strong> 85Kr to be 2.2 x 10 - 3 mrem/hr per Ci/m 3 (1.9 x 10 -8 rem/yr per<br />

pCi/m3). Combining this dose factor and a constant world population <strong>of</strong> 6.4 x 109 persons<br />

with the expression for concentration (C 3 0 ) yields the world population whole-body dose<br />

rate in the 30th year as follows:<br />

- 6<br />

3.34 x 10<br />

(pCi/m 3 ) per (Ci/yr)] (6.4 x 109 persons) [1.9 x 10 8 (rem/yr) per (pCi/m3)]<br />

= 4.08 x 10 -4 man-rem/yr per Ci/yr released for 30 years.<br />

The accumulated 70-year dose is<br />

[1.13 x 10 - 4 (pCi.yr/m 3 ) per (Ci/yr)J (6.4 x 109 persons) 1[.9 x 107 8 (rem/yr) per (pCi/m 3 )]<br />

= 1.38 x 10 -2 man-rem/70 years per Ci/yr released for 30 years.<br />

These factors are summarized in Table D.2.1.<br />

(a) Defined as the layer <strong>of</strong> tissue lying 5 cm below the surface <strong>of</strong> the skin.

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