[ RadSafe ] Cross Section and Critical Mass Data

Derek Putley derek.putley at serco.com
Tue Mar 22 03:20:26 CDT 2011

George / All
An excellent source of cross section data is the freely available JANIS database from OECD/NEA, see: -
For data on the critical masses of fissile and fissionable nuclides (and much more besides), see PNNL-19176. 
Table X gives calculated critical masses for common and "exotic"  nuclides.
I do, however, disagree with George's suggestion that the discovery of thermal neutrons proves the presence of water. 
Successive collisions with any nuclides will eventually reduce neutron energies to thermal values.
>Message: 5
>Date: Fri, 18 Mar 2011 12:41:01 -0700
>From: <GEOelectronics at netscape.com>
>Subject: [ RadSafe ] Neutron interaction data needed.
>To: <radsafe at agni.phys.iit.edu>
>Message-ID: <20110318124101.36F7C4CD at resin16.mta.everyone.net>
>Content-Type: text/plain; charset="utf-8"

>We need data on cross section ( Barns) and which elements
>will multiply with A) Fast neutrons and B) Thermal neutrons.
>What are chances of any sort of criticality, assuming a partial melt.

>PS water/no water in pools? Take a neutron spectrometer 8in, search for slow neutron Thermal neutrons = moderation=water. Also take an optical spectrophotometer reading of the "white vapor" rising >from buildings. hydrogen line (water), or is it zirconium smoke??

>George Dowell

Best Regards

Derek Putley

Technical Area Lead (Criticality) 
Serco (Technical Services)
Thomson House, Risley, Warrington, Cheshire, WA3 6GA, UK

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