Re: So, is reprocessing in America's future?

["Zack Clayton" <zack.clayton@EPA.STATE.OH.US>]

Posted to the list for others that don't have this info available.  

I don't recall signing a secrecy agreement, so:



The way I understand it is the Pu239/240 ratio is dependant on dwell time in the neutron flux.  Hanford may do further tuning of the neutron spectrum to enhance Pu production over power generation but I believe the mechanism and decay pathways stay the same.  I can see no way to change that.



Pu 239 increases in concentration for about 120 days and then plateaus.  Pu240 is formed by neutron capture and reaches about 10 atoms/barn*cm*10e-6 at about 1000 hours and continues to increase beyond that time before it reaches steady state**.  This is why a reactor with on line refueling capability  is considered a proliferation threat more than a light water boiler or PWR.  The original Hanford reactor was graphite moderated with a dwel time in the active core of a little less than 40 days.  Fuel was fed in one end and fell out the other end of the fuel channel for reprocessing after a short decay time.  The exact dwell time was probably chosen to max out the Pu239/U238 ratio and minimise the Pu239/240 ratio. 



See Nuclear Engineering, 2nd Ed,  Ronald Allen Knief, 1992.  isbn1-56032-089-3.  Lib Congress TK9145.K62.

**See fig 6-2.



As a side note, this was one reason that (allegedly) the Soviet Union built so many RMBK reactors.  They could refuel them on line if they wanted a surge of PU239 production.  Of course there were other problems associated with that idea.



Zack Clayton

Ohio EPA - DERR

email:  zack.clayton@epa.state.oh.us

voice:  614-644-3066

fax:       614-460-8249





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