Dosimetry test program on experimental fast reactor 'JOYO'

In fast reactors, neutron irradiation to the fuels and materials constructing the cores is higher than that of thermal reactors. Therefore, in the experimental fast reactor JOYO , the post-irradiation examination has been implemented for core-constructing elements such as fuel assemblies, and the surveillance test has been performed for structural materials. The post-irradiation examination includes the soundness evaluation for fuel material and fuel assembly components and the measurement of fuel burn-up. The surveillance test is that carried out over about 20 years for verifying the soundness of structural materials during reactor operation, i.e. the test under an obligation to secure the reactor safety, and which is now underway. For these examination and testing, the measurement of neutron irradiation dose is indispensable. At present, neutron flux monitors and dosimeter sets composed of Fe, Ni and Cu foils are loaded in the JOYO irradiation rig. Those are taken out after a certain time elapsed. This paper explains the progress of dosimetry test and JOYO dosimetry system (including analytical procedure). For the test results, domestic mutual comparison has been carried out in four organizations; Tokyo and Kyoto universities, JMTR (Japan Material Testing Reactor) in Japan Atomic Energy Research Institute, and JDWG (JOYO Dosimetry working group) in Power Reactor and Nuclear Fuel Development Corp. (PNC). Also, in 1980, mutual comparison between PNC and Department of Energy, USA, has been implemented. This is a mutual dosimetry test between JOYO and EBR-II reactors. Finally, the causes of the problems in dosimetry tests are listed. (Wakatsuki, Y.)