Impact of photo neutrons on reactivity worth of {sup 3}He in a reactor with beryllium reflector

Conference · Sat Jul 01 04:00:00 EDT 2006

OSTI ID:22039575

Kalcheva, S; Koonen, E ^[1]

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1. SCK CEN, Belgium Nuclear Research Centre, Boeretang 200, B-2400 Mol (Belgium)

A study about the contribution of photo neutrons, produced in ({gamma}, n) -reactions of {sup 9}Be into the reactivity worth of {sup 3}He in a reactor with beryllium reflector is presented. Neutron interactions with beryllium lead to formation of {sup 3}T and strong neutron absorbers {sup 3}He and {sup 6}Li in the reflector (so called beryllium poisoning). After the reactor shut down, the concentration of helium - 3 increases in time due to tritium decay. The negative reactivity effect of neutron absorption by accumulated {sup 3}He has been considered in a few papers, concerning reactivity losses in reactors with beryllium reflector. The contributions of the photo neutrons for additional production of tritium during the reactor operation and enhanced build up of helium - 3 after the shut down have not been discussed previously. Calculations of the photonuclear reactions in beryllium are performed for the Belgian Material Testing Reactor BR2 and for a generic reactor model with beryllium reflector. The calculation analysis has shown an increase of about {approx} 20% in the reactivity worth of helium-3 by photo neutrons. The effective fraction of photo neutrons is estimated using MCNP5 with included ({gamma}, n) - reactions. (authors)

• Research Organization: American Nuclear Society, 555 North Kensington Avenue, La Grange Park, IL 60526 (United States)
• OSTI ID: 22039575
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
BERYLLIUM
BERYLLIUM 9
BR-2 REACTOR
GAMMA RADIATION
HELIUM 3
LITHIUM 6
NEUTRON ABSORBERS
NEUTRON REACTIONS
NEUTRON REFLECTORS
PARTICLE DECAY
PHOTONEUTRONS
REACTIVITY WORTHS
REACTOR OPERATION
TRITIUM