[ RadSafe ] Cl-38 and neutrons
mcnaught at lanl.gov
Fri Apr 1 16:53:26 CDT 2011
Thank you for the valuable comments.
What minimum gamma energy is required to produce photo-neutrons from deuterium? The higher-energy gammas are mostly from the shorter-lived radionuclides. Most of the remaining fission products emit lower-energy gammas. Do these have sufficient energy?
From: radsafe-bounces at health.phys.iit.edu [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Phil Simpson
Sent: Friday, April 01, 2011 3:12 PM
To: The International Radiation Protection Mailing List
Subject: [ RadSafe ] Cl-38 and neutrons
I'm very suspect that Cl-38 was detected for reasons already cited on
this forum (Where are its activation product cohorts?).
I also find it extremely unlikely that a criticality event has or will
occur at the shutdown and crippled reactors. It is quite an
engineering feat to create a critical mass of low enriched uranium.
See the prior discussions touching on core design, fuel to moderator
ratio, "buckling", etc. Any event that degrades the core geometry will
make criticality that much less likely to occur.
However, some sub-critical neutron multiplication is probably taking
place. This very low level neutron flux will be generating neutron
activation products. But, their significance is dwarfed by the existing
fission product inventory. The source of the neutrons is not primarily
spontaneous fission but instead photo-neutrons. The photo-neutrons are
generated by fission product gamma reactions with deuterium naturally
present in water.
As an aside, photo-neutrons from fission product gammas and activated
reactor structural materials are also the primary neutron startup
source for any reactor that has been operating for a while.
Assistant Reactor Manager (Ret.)
University of Michigan
Ford Nuclear Reactor
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