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The Influence of the (n,2n) and (n,/cap alpha/) Reactions of Beryllium on the Neutron Balance in a BeO or Be Moderated Reactor and Its Consequences on the Long Term Reactivity Changes; INFLUENCE DES REACTIONS (n,2n) ET (n,*cap alpha/) DU BERYLLIUM SUR LE BILAN NEUTRONIQUE D'UN REACTEUR MODERE A L'OXYDE DE BERYLLIUM OU AU BERYLLIUM. CONSEQUENCES SUR L'EVOLUTION A LONG TERME De la reactivite

Technical Report ·
OSTI ID:4276499
The reaction probabilities in an infinite and homogeneous medium of BeO or Be were calculated from neutron cross section curves. for a neutron produced with an energy distribution similar to a fission spectrum. The calculation shows that after several elastic collisions the neutron still has an appreciable probability to undergo a reaction, in spite of the energy degradation in the spectrum due to each collision. This degradation was calculated, taking irto account the anisotropy of the collisions. The gain of the reactivity in a reactor was obtained affer correcting these probabilities for the attenuation of the flux of fission neutrons due to the inelastic scattering in the uranium. Finally, the calculation shows that in a power reactor this gain of reactivity is in practice destroyed in a few years by the accumulation of poisonous nuclei such as Li/sup 6/ and He/sup 3/ following (n, alpha ) reactions. (auth)
Research Organization:
France. Commissariat a l'Energie Atomique, Paris
NSA Number:
NSA-13-009362
OSTI ID:
4276499
Report Number(s):
CEA-826
Country of Publication:
France
Language:
English