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arXiv · 1403.4833

Influence of thermal and resonance neutron on fast neutron flux measurement by Pu-239 fission chamber

Lina zeng·Qiang Wang·Lingli Song·Chun Zheng
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Abstract

The Pu-239 fission chambers are widely used to measure fission spectrum neutron flux due to a flat response to fast neutrons. However, in the mean time the resonance and thermal neutrons can cause a significant influence on the measurement if they are moderated, which could be eliminated by using B and Cd covers. At a column enriched uranium fast neutron critical assembly, the fission reaction rates of Pu-239 are measured as 1.791*10-16,2.350*10-16 and 1.385*10-15 per second for 15mm thick B cover, 0.5mm thick Cd cover, and no cover respectively. While the fission reaction rate of Pu-239 is rapidly increased to 2.569*10-14 for a 20mm thick polythene covering fission chamber. The average Pu-239 fission cross-section of thermal and resonance neutrons is calculated to be 500b and 24.95b with the assumption of 1/v and 1/E spectra respectively, then thermal, resonance and fast neutron flux are achieved to be 2.30*106,2.24*106 and 1.04*108cm-2s-1.

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Lina zeng, Qiang Wang, Lingli Song, Chun Zheng. 2014-03-19. Influence of thermal and resonance neutron on fast neutron flux measurement by Pu-239 fission chamber. https://doi.org/10.1088/1674-1137%2F39%2F1%2F016001

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