RE: Nuclear-powered spacecraft plan feared

["Grimm, Lawrence" <LGrimm@FACNET.UCLA.EDU>]

Radsafers:



A radsafer sent me the following (slightly edited), and my response to him follows.  I am seeking your comments/advice on the assumptions I am making regarding a Pu accident. Please comment privately. Thanks. -lg  



Larry,



Normally I don't respond to posts on radsafe, but your letter to the SF

Chronicle reporter has me worried.  We as a health physics community need to

respond to outlandish statements voiced by members of the anti-nuclear crowd

with factual and reasoned scientific argument.  Your statements on Pu

exposure were not.



The most likely uptake method in such an accident scenario or for that matter most

any scenario apart from eating Pu particulate or sucking on a contaminated

finger is inhalation of suspended Pu oxide.  Unlike Natural U (or even

weapons grade U) inhaled Pu (239, 240 or 238) is much more of a radiological

hazard than chemical because of its specific activity.  A small amount of S

or M class Pu can cause a very large committed dose to the lungs based upon

the ICRP 66 models.  - CP



My Response.



CP: I appreciate the advice.  I fully agree with your assessment of the potential lung dose. I would be interested if you have info to the contrary, but it is my understanding that PuO does not stay suspended in the air very long due to its large atomic weight.  In an accident scenario, unless the person is near the location, the risk of inhalation drops dramatically with distance.  I am also making the presumption in an accident with a rocket, e.g. the shuttle or other space craft, that it would occur at high altitude.  As a result, any created PuO would disperse over a huge area, with a lessening of inhalation risk as it disperses.  In a rocket accident, the better percentage of the Pu would remain in the debris as particulate material, with the subsequent risk of ingestion primarily being particulate mishandling, e.g. sucking on a contaminated finger. 



It is very tough to simplify these sorts of assumptions in statements to the public.  Frankly, if I said all of the above to a reporter, the reporter would tune out immediately.  When I make simplified statements to reporters, I always have a defensible position ready in case I am challenged.   - Larry Grimm



Larry Grimm, Senior HP

UCLA EH&S/ Radiation Safety Division

*	lgrimm@admin.ucla.edu   Phone:310/206-0712   Fax: 310/206-9051

	Cell: 310/863-5556  Pager:1-800-233-7231ext93569

*	On Campus: 501 Westwood Plaza, 4th Floor, MS 951605

*	Off Campus: UCLA Radiation Safety Div, 501 Westwood Plaza 4th

Fl, Box 951605, Los Angeles, CA 90095-1605

*	If this email is not RSD business, the opinions are mine, not UCLA's.

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