RE: [2]: CANDU Reactors

["Lieskovsky, Miro" <MLieskovsky@nbpower.com>]

Radsafers,

By the time a typical CANDU fuel bundle is taken out of the reactor,
approximately 40% of all fissions have been provided by the 239Pu. It is
created by radiative capture of 238U, i.e. a CANDU reactor is 'relatively' a
good producer of 239Pu since it uses nat-U.

Also both the moderator and the heat transport system contain heavy water
(D2O)

Regards, 
Miroslav Lieskovský
Health Physicist
NB POWER - PLGS
P.O. BOX 600
Lepreau, N.B.
Canada, E5J 2S6
Tel. (506) 659 7421
Fax. (506) 659 6981
mailto:mlieskovsky@nbpower.com
http://www.nbpower.com







-----Original Message-----
From: Rodney Bauman [mailto:rodney_bauman@wssrap-host.wssrap.com]
Sent: Wednesday, August 16, 2000 5:09 PM
To: Multiple recipients of list
Subject: Re:[2]: CANDU Reactors


Jaro wrote:

>CANDU uses natural uranium (with 0.71% U235).
>The point is that it also breeds quite a lot of RGPu in the process, >by
way of
the neutron capture by U238, without fission, yielding >Pu239, then 240,
241,
etc. with additional n-captures (though most >Pu burns up in-situ).

Good point, however this same process occurs in light water reactors, just
to a
lesser extent.  U-238 is not fissile and heavy water is still required to
achieve critically, especially at the beginning of core life.

An interesting note to this thread is exactly how much of the thermal energy
in
a commercial reactor core is actually the result of Pu-239 fissions and not
U-235 fissions.  The number is significant, and probably larger than most
people
suspect.  I recall something like 30% of the fissions are from Pu-239 for a
typical light water reactor near the end of core life.  Is this right?

Rodney Bauman, CHP, RRPT
rodney_bauman@wssrap-host.wssrap.com


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