Re: Thermalisation optimisation

["H.Wade Patterson" <hwade@talltown.com>]

Anthony Barber wrote, in part:
> 
> I am looking for information to help optimise the thermal neutron flux in
> the cavity around a 370GBq Am/Be and 370GBq Pu/Be source.
> 
> What thickness of polyethelene will produce optimised thermal neutron flux
> in this configuration?

> I'm considering polyethelene moderator surrounded by a Be reflector, then a
> 1m thick concrete bunker. (if practical)
> 
> All help and suggestions greatfully accepted.

Anthony:
There's a brief discussion of this matter on page 306 of Accelerator
Health Physics, Patterson and Thomas, Academic Press, 1973.
The walls can't be too thick, because the thermal flux in the cavity
depends only on the mean depth of fast neutron thermalization in the
wall material. If you make the walls equal to (or even greater than)
this thickness the thermal flux is optimized.
-- 
Cordially,

Wade

<hwade@talltown.com>

H.Wade Patterson
1116 Linda Lane
Lakeview OR 97630
ph 541 947-4974