[ RadSafe ] Thorium! Thorium reactor remixed lecture in 16 minutes

George Stanford gstanford at aya.yale.edu
Thu Feb 3 16:26:07 CST 2011


      The short answer is that it's pretty much equivalent, if not a 
little worse.  The thorium reactor is no more exempt from the need 
for safeguards than any other type of reactor.


(A)   First of all, any uninspected reactor can be modified to 
irradiate special U-238 fuel elements for short periods of time, to 
yield high-quality Pu-239 for weapons.  But with a thorium reactor, 
the modifications might have to be much more extensive than with a 
uranium reactor.

(B)  However, be aware that, regardless of how many reactors a nation 
has, it will not me able to make any A-bombs without one of 
these:  (a) an enrichment capability (for U-235 bombs), (b) a 
PUREX-type of fuel reprocessing facility (for Pu-239 bombs) or (c) a 
facility for extracting Pa-233 from thorium fuel (for U-233 
bombs).  Hence the need for inspectors, and for international 
supervision of enrichment and fuel-processing facilities.

(C)  Some thorium enthusiasts (not all) like to point out (correctly) 
that the U-233 in a thorium reactor is hopelessly contaminated with 
U-232.  But what they sometimes don't mention (and didn't in that 
rapid-fire YouTube video) is that at least some of the proposed 
thorium cycles involve running the liquid fuel through a processor 
that chemically separates Pa-233 from the mix before it decays to 
become pure U-233 (which is a superior bomb material) -- easily 
diverted for bombs.  But see (D), next.

(D)  The standard thorium-supporter's response to that Pa situation 
seems to be that the breeding potential of thorium reactors is so 
poor that diverting Pa would shut the reactor do\wn for lack of 
fissile material.  However, the initial charge of a thorium reactor 
has to be spiked with enough fissile in (low-quality) Pu-239 or 
low-enriched uranium to permit it to become critical in the first 
place.  Thus the infrastructure would be in place for substituting 
crappy uranium of plutonium for the Pa-233 diverted from the operating reactor.

(E)  The bottom line is that an unsafeguarded thorium reactor could 
rather readily serve as an efficient mechanism for converting 
weapons-useless uranium or plutonium into highly usable 
U-233.  Inspectors would be needed.

      Does this help?

      --  George Stanford
      Reactor physicist,retired


----- Original Message -----
From: "Michael McNaughton" <mcnaught at lanl.gov>
To: "The International Radiation Protection (Health Physics) Mailing 
List" <radsafe at health.phys.iit.edu>
Sent: Thursday, February 3, 2011 2:40:11 PM
Subject: Re: [ RadSafe ] Thorium! Thorium reactor remixed lecture 
in        16        minutes

Is the "proliferation" problem with a thorium reactor better or worse 
than with a conventional reactor?

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu 
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Jim Darrough
Sent: Thursday, February 03, 2011 1:06 PM
To: 'The International Radiation Protection (Health Physics) Mailing List'
Subject: Re: [ RadSafe ] Thorium! Thorium reactor remixed lecture in 16 minutes

If you talk to a Nuclear Engineer, and mention Th or U-233, the deal is
dead. They start parroting "proliferation" and become focused on the
possible production of weapons.

I think the Thorium fuel cycle is well worth the investment, but the
political rhetoric that has clouded the thinking of the people who can make
the decision to utilize it must be overcome. That is the real issue here.

Jim Darrough

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