Fission Chambers Detector Unit Mockup Testing at Research Reactors

This paper presents the results of the fission chambers (FC) behavior under intensive neutron and gamma radiation at the research reactors. The FC detector unit (DU) was designed for the International Experimental Thermonuclear Reactor neutron diagnostic “divertor neutron flux monitor.” Two mockups of the DU with FCs containing 1 g and 100 mg of 235U were tested. The test complex is based on the FC signal processing unit and the FC parameters’ monitoring system. The processing unit contains several measuring chains and acquire FC signal over a wide range of neutron flux variation. The FC parameters’ monitoring system records signal shapes, acquires pulse-height amplitude spectra, and checks electrical parameters of the neutron detector. The radiation tests were carried out at the research reactors IRT MEPhI and VVR-c. The structure and characteristics of the test complex as well measurement techniques and tools for FC characterization are discussed. The results of reactor experiments to determine characteristics of the DU mockup and wide-range neutron flux monitoring channels are presented.