[ RadSafe ] LTN

William Lipton doctorbill34 at gmail.com
Wed Jun 24 19:01:33 CDT 2015

The NRC recently received petitions from Carol Marcus, Mark Miller, and
Mohan Doss requesting that NRC radiation protection regulations be based on
hormesis rather than the Linear No Threshold (LNT) hypothesis.  A notice
requesting comments was published in the Federal Register on June 23,
2015.  Although flawed, these petitions are probably worthy of some

The problems with these petitions are best describe in 3 categories:

(1) procedural - Since NRC rad protection regulations must be based on EPA
guidance, the NRC cannot change their basis even if it wanted to.  They
should petition the EPA, which superseded the Federal Radiation Council, in

(2) scientific - The EPA requires following scientific consensus, as
published by groups such as the International Commission on Radiological
Protection (ICRP).  The references quoted by the petitioners do not seem to
represent scientific consensus.  It's important to keep in mind that LNT is
NOT presented as being real, only as a safe, conservative basis for
planning.  One of the petitions even recommends raising the allowed dose
for declared pregnant workers AND members of the public to 10 rems.  This
is clearly approaching levels at which teratogenic effects have been found.

(3) practical - Besides assuring adequate standards for radiation
protection, the LNT  - based concept of "As Low As is Reasonably
Achievable" (ALARA) promotes sound practices which generally increase work
efficiency.  Keep in mind that the definition of ALARA specifies practical
measures which take economic, technological, and societal factors into
account.  I've personally found that, at power reactors, the application of
ALARA concepts promotes sound work planning, which increases efficiency
and, ultimately, saves money.  (When I began my career in rad protection,
in the 1970's, there were reports of physicians increasing x-ray exposure
times rather than replacing weak film developer solutions, as well as
poorly collimated beams which exceeded the film size.  Also, power reactor
Radiological Environmental Technical Specifications allowed plant operation
with failed fuel.  Those reactors which did this have long regretted this
practice, since it resulted in residual alpha contamination which makes
work much more difficult.  Such non-ALARA practices should not be allowed.)

Bill Lipton CHP (emeritus)

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