Re: Nuclear Power

[Bernard L Cohen <blc+@pitt.edu>]

Bernard L. Cohen
Physics Dept.
University of Pittsburgh
Pittsburgh, PA 15260
Tel: (412)624-9245
Fax: (412)624-9163
e-mail: blc+@pitt.edu


On Thu, 29 Aug 1996 azapantis@MGDESTMX01.ERIN.GOV.AU wrote:

> 
> 1. Fast breeder reactors use a mixture of Pu239 and U238 as fuel. U238 atoms
> capture neutrons to become U239, then decay via beta emission to form Np239,
> then via beta emission again to form Pu239 (very quickly I assume). The Pu239
> atom thus formed can then also undergo fission induced by fast neutrons. Fast
> breeder reactors do not use any moderator

Correct.

> 
> 2. Fast breeder reactors require a much higher flux of neutrons in the core (10
> times, 100 times??) to sustain the chain reaction than "thermal reactors" and
> thus must be much more compact.
> 

The size of a power reactor is much larger than the minimum needed to make
the chain reaction critical. Criticality is adjusted with control rods.
Size is adjusted by heat transfer and other such considerations. Nearly
all  neutrons strike a fuel nucleus, but in a fast reactor they travel
further before doing so.
An FBR also uses a blanket to improve neutron economy, which substantially
increases the size.
> Questions;
> 1. What kind of coolant to FBR use?
> 
--They generally use liquid metal, which converts the name to LMFBR. The
liquid metal is usually sodium.


> 2. Are any FBRs currently commercially supplying electricity.
> 
Large amounts of electricity are now supplied from FBRs in France and
Russia

>