[ RadSafe ] Fukishima Pu-239

[Brennan, Mike (DOH)]

I suspect that it is largely a matter of what "more" means in this context: more per unit mass of fuel, more per operating hour, more per unit of energy produced, etc.  It also depends on whether you are taking about Pu-239 made or Pu-239 releasable/recoverable (not fissioned in  the reactor where it is created).

You certainly can make Pu-239 with both heavy and light water reactors.  If you are looking to recover Pu for bomb making you want to be able to refuel online, because you don't want your fuel to "over cook", as Pu-240 and Pu-241 both present problems in processing plutonium (but are of much less concern if you are planning to burn up the fuel in a reactor).  

As to the release of Pu of any flavor from Fukushima: almost certainly.  How much and in what chemical form probably is still in the "anyone's guess" category, but it is quite reasonable to guess that it makes up only a tiny, tiny fraction of what has been released, whether measured by mass, atom, or activity.

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Jaro Franta
Sent: Friday, June 06, 2014 6:32 PM
To: 'The International Radiation Protection (Health Physics) Mailing List'
Subject: Re: [ RadSafe ] Fukishima Pu-239

Actually, enriched fuel like Fukishima produces MORE Pu than a heavy water reactor using unenriched fuel, for the simple reason that the irradiation of enriched fuel is about five times greater.

 Jaro
^^^^^^^^^^^^^^^^^^^^^^^^^





-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of sfisher373 at aol.com
Sent: June-06-14 8:15 PM
To: radsafe at health.phys.iit.edu
Subject: [ RadSafe ] Fukishima Pu-239



Pu-239 comes from the U-238 in the fuel.  So enriched fuel like Fukishima produces less Pu than a heavy water reactor using unenriched fuel.  



The neutrons are thermalized in the fuel and cause the U-235 to fission.
The ideal place for fissioning is on the outside of the fuel bundle.  Deeper in the neutrons have lost energy and are resonantly absorbed by the U-238.
The U-239 fissions easier than the U-235 so any U-239 formed on the outside will fission.  However, burnup also depends on where in the reactor the fuel bundle is. So the statement that there is more Pu on the outside of the bundle rather than deeper in does not make much sense.  


In Candu reactors about half the energy comes from the Pu-239 fissions.  One of the reasons why nuclear non proliferation groups do not like the CANDU reactor, along with on line refueling so it is theoretically easier to steal a bundle.  


However, separating the isotopes from a spent fuel bundle requires more expertise than just enriching fuel.  


Spencer M Fisher




 
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