Neutron Detector for Reactor Control

Abstract

A parallel circular plate type ionization chamber (PCP) and a gamma ray compensated ionizattion chamber (CIC) to be used for reactor control have been made as much as possible with those home materials that are small in neutron absorption cross-section and induced activity and are also radiation and high temperature-resistive checked by activation analysis. Boron power (enriched 96% B) imported from ORNL, U.S.A. is used. During the preparatory work, technique of fine machining of reactor grade graphite, arc welding of magnesium in argon, and boron coating are developed. Neutron sensitivity, γ ray sensitivity, linearity, and induced activity of six kinds of neutron detectors including the author's PCP and CIC and one that was imported are tested by using JRR-I reactor and γ ray sources of 10 kc Co⁶⁰ in JRERI and 1 kc Co⁶⁰ in Toshiba radiation laboratory. Results of the tests show that the author's detectors are not only just as good as the imported but superior to it as regards the residual activity.