Neutron moderator, neutron irradiation method, and hazardous substance detector

Abstract

In a neutron moderator, a neutron irradiation method, and a hazardous substance detection apparatus, an inspection chamber (21) where an inspection target (A) can be inserted and removed is provided. Around this inspection chamber (21), a thermal neutron absorbing material (15) is provided. A neutron generator(11) is arranged facing the inspection target (A) in the inspection chamber (21), and a neutron moderating material (12) is arranged at an opposing side of the inspection target (A) with respect to the neutron generator (11). The external surface of the neutron moderating material (12) is covered with gamma ray shielding materials (13, 14), and a Ge detector (24) and a BGO detector (25) are provided to detect gamma ray emitted from the inspection target (A). With this configuration, necessary fast neutron and thermal neutron can be taken out, while suppressing generated secondary gamma ray. Accordingly, a hazardous substance can be detected accurately regardless of a constituent element thereof.

Description

technical field [0001] The present invention relates to a neutron decelerator which decelerates very high-energy high-velocity neutrons generated by a neutron source to generate low-energy neutrons, and a hazardous substance detection device which uses the neutron decelerator to inspect dangerous substances such as explosives. Background technique [0002] For example, in large-scale gathering places where many people gather, such as stations, airports, ports, baseball stadiums, football stadiums, assembly halls, art galleries, etc., check the belongings of the entrants when entering the venue, and prevent dangerous substances such as explosives Bring in for safety. It is known to use neutrons to detect explosives. Nitrogen is often included as a constituent element of explosives. In previous developments, there was a proposal to decelerate high-speed neutrons from a neutron generating source into thermal neutrons through a deceleration material, irradiate the thermal neutr...

AI Technical Summary

Problems solved by technology

[0005] However, the neutron moderator material and the explosive are also composed of carbon, hydrogen, oxygen, nitrogen and other structural elements. When the high-speed neutrons from the neutron source pass through the moderator material, they will decelerate into thermal neutrons and irradiate the explosive. When gamma rays are detected, the amount of gamma rays detected is that the gamma rays generated by the explosives are mixed with the gamma rays generated by the neutron moderator, and there is a problem that the measurement accuracy deteriorates and the detection accuracy of explosives decreases.

When detecting the constituent elements of explosives based on gamma rays generated by irradiating thermal neutrons to explosives, the amount of gamma rays detected is that the gamma rays generated by explosives are mixed with carbon, hydrogen, and oxygen in the air. , Gamma rays produced by nitrogen reduce the detection accuracy of explosives

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