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Report No.

Neutron spectra and angular distributions of concrete-moderated neutron calibration fields at JAERI

Yoshizawa, Michio  ; Tanimura, Yoshihiko   ; Saegusa, Jun; Nemoto, Hisashi*; Yoshida, Makoto

The facility of Radiation Standards (FRS) of JAERI has equipped with the concrete-moderated neutron calibration fields as simulated workplace neutron fields. The fields use an Am-Be (37GBq) neutron source placed in the narrow space surrounded by concrete wall and bricks to produce scattered neutrons. The neutron spectra of the fields were measured with Bonner multi-sphere spectrometer system (BMS), spherical recoil-proton proportional counters (RPCs), and a liquid scintillation counter (NE-213). The results were compared with each other, and the neutron spectra and the ambient dose equivalent rate, ${it H}$$$^{*}$$(10), were agreed well within the uncertainty. The angular distributions of neutron fluence were calculated by the MCNP-4B2 Monte Carlo code to obtain the reference personal dose equivalent rate, ${it H}$$$_{p}$$(10). The calculated results show that the scattered neutrons have a wide variety of incident angles. The reference ${it H}$$$_{p}$$(10) values considered the angular distribution were found to be 10-18% smaller than those without consideration.



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Category:Environmental Sciences



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