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Success in Technical Development for Advanced Irradiation Utilizations in JMTR
-Development of Neutron-Irradiation Control Technology Leading Material Testing Reactors in the World-
Jan. 14, 2010
The Japan Atomic Energy Agency (JAEA, President Toshio Okazaki) has succeeded in �Development of neutron-irradiation control technology� using the irradiation capsule holder packed with beryllium pebbles. In result of the development, prospects are bright to offer user�s requested neutron irradiation field which is satisfied in accuracy.
Neutron irradiation tests are carried out with the irradiation capsules installed the specimens in almost Material Testing Reactors (MTR) in the world. Capsule holders made of beryllium and aluminum have been used usually in irradiation capsules. Neutron irradiation field is controlled normally by the material selection of capsule holders or by the utilization of profiled absorber in the irradiation capsule. However, current methods can not apply to the user�s requests for the neutron irradiation condition in accuracy. Therefore, the new control technology for neutron irradiation fields has been developed. The new irradiation capsule holder has a hollowed structure in which beryllium pebbles with the diameter from 0.2 to 2 mm are packed into the housing. As a result of a neutronic evaluation, it was found that continuous variable control of thermal neutron flux or neutron spectrum is possible by changing packing fraction of pebbles in order to control the neutron scattering cross section within two limits between beryllium and the aluminum capsule holders. The new developed technology with fine control in the neutron irradiation field would be possible to apply various kinds of utilization such as linear power density of LWR (Light Water Reactor) fuels irradiation, production of radioisotopes such as 99Mo, production of silicon semiconductor, and resolution of neutron irradiation effects for fusion research.
In future, high contribution of the developed technology is expected in the safety study for LWRs and development of next generation reactors, expansion of industry use for production of silicon semiconductor and radioisotopes, and progress of science and technology for development of fusion reactors.
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