Testing of Compton-emission neutron detectors with hafnium-containing emitter in RBMK-1000 reactors

The Compton-emission neutron detector (CEND) with an emitter containing hafnium is a promising detector for monitoring energy release (DMER) in nuclear reactors. In contrast to the ..beta..-emission neutron detectors (BEND) with a rhodium, silver, or vanadium emitter, which are used extensively in power reactors, CEND with a hafnium emitter has virtually no delay in response. It can be used, therefore, in automated systems for reactor monitoring, control, and protection, where higher requirements with respect to speed are placed on detectors. The detectors were tested under natural conditions in RMBK-1000 reactors of the first and second power units of the Chernobyl Atomic Power Plant and the third unit of the Leningrad Atomic Power Plant. The authors tested 13 hafnium CENDs of the cable type, which were similar in design to the previously tested BENDs with a silver emitter. The tests showed that to within +/- 4% the CEND signal is proportional to the power of the fuel assembly in which the CEND is installed, over the range from 4 to 100% of the nominal power. The CEND sensitivity was defined as the ratio of the CEND current to the power of the fuel assembly in which it is installed.