Annual report of department of research reactor, 2004. April 1, 2004 - March 31, 2005

The Department of Research Reactor is responsible for the operation, maintenance and utilization of the JRR-3 (Japan Research Reactor-3) and the JRR-4 (Japan Research Reactor-4) as well as for the related research and development (R and D). Besides them, the department carries out the radioisotope (RI) production as well as its R and D. The major outcomes were the followings in Japanese Fiscal Year 2005: 1) The JRR-3 and JRR-4 were well operated, as planned before. The operated cycles of the JRR-3 were 7 cycles (total 182 days) and those of the JRR-4 were 41 cycles (total 150 days). 2) Irradiation tests of 641, capsule irradiations of 2546, experiments of 6027 (workdays) were achieved through deliberate coordination for common utilization. Medical irradiations of 9 were done in the JRR-4. 3) The seventh transportation was accomplished for 80 spent fuel (JRR-3) to USA. Also, conceptual design for the spent fuel container was finished. 4) A prospect was obtained through optimization of moderator container form, upgrading of neutron guide performance, that the intensity of cold neutron beam of JRR-3 can be increased to 10 times larger. 5) The accuracy of irradiation dose for boron neutron capture therapy was enhanced through improvements of irradiation dose evaluation code system (JCDS) and setting system for patients. 6) Radioactive 88Re was produced for research of its labeling for cancer medicine. Water- and oil- densimeters were developed where gamma- and neutron- rays from 252Cf were applied simultaneously. Besides above-mentioned activities, the international co-operations with developing countries were carried out for operation and utilization of research reactors, RI application and so on. (author)