[ RadSafe ] question on LNT relating to SNF TRU versus U-ore NORMs

[Jaro]

Most of the knowledgeable folks on this list appear to agree that its highly
inappropriate to apply LNT for risk estimation w.r.t. alpha-active
radionuclides, such as the NORMs in U-ore, or TRUs in SNF, because of a
well-defined threshold dose (examples being the Radium Dial Painters, and B.
Cohen's domestic Radon effects study).

Yet it seems that ICRP is doing just that, in its calculation of the Water
Dilution Volumes (WDVs) required to meet regulatory safety limits.

Specifically, in calculating the WDVs as a function of time following
discharge of SNF from a reactor, and plotting that curve on a graph that
also shows the horizontal reference line for U-ore, Eisenbud says
("Environmental Radioactivity," 4th Ed.) that the big difference in x-over
points between NRC (<1000y) and ICRP (>10,000y) is due mainly to the Np237
change in absorption factors for transfer from the intestines to blood,
which ICRP changed in its Part 2 of Publication 30 (1979 - 1988), and which
US agencies later adopted.

One might think that it should be a straight forward calculation to compare
radiotoxicity vs time for SNF and U-ore.
But that's obviously not the case, since the x-over point moves around by
orders of magnitude, depending on the assumed absorption factors and, more
importantly, whether one applies LNT to very low dose levels.

Does anyone know what the WDV curve for SNF would look like if an
appropriate, threshold-type dose-response relationship were applied in place
of LNT, and whether-or-not ICRP will ever get around to correcting its
recommendations & calculations ?
Also, are there any other authorities that currently use the non-LNT
calculation for deriving WDV curves ? (links please).
What is the HPS's position on this ? ....RSH ?

Thanks very much.

 Jaro Franta, P.Eng.
Tel.: (514) 875-3444
Montréal, Québec
frantaj at aecl.ca
web master, CNS Québec branch:
http://www.cns-snc.ca/branches/quebec/quebec.html

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