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Okoshi, Minoru; Sakai, Akihiro; Abe, Masayoshi; Tanaka, Mitsugu
IAEA-CN-87/50 (CD-ROM), p.113 - 118, 2002/12
As the result of research activities for nuclear energy utilization over 45 years, large amounts of low-level radioactive waste (LLW) are stored at Tokai Research Establishment of JAERI. In order to plan the disposal program, JAERI carried out the radiological characterization of the waste. The results show that about 34,400 tons of LLW will arise from the operation and dismantling of the facilities by the end of 2045. The total activities of beta- and gamma-radionuclides and alpha-radionuclides are about 44 PBq and 56 TBq, respectively. By using the estimated total weight and radioactivities of the waste, important radionuclides were selected from the viewpoint of safety according to the performance assessment of near surface disposal facilities. As the results, twenty-seven radionuclides including twelve alpha-ray emitting actinides were selected as the candidate important radionuclides. Those are slightly different from important radionuclides selected for commercial nuclear power plants because of materials used for facilities and so on.
Okoshi, Minoru
Radioisotopes, 47(5), p.412 - 423, 1998/00
no abstracts in English
PNC TN9000 94-006, 60 Pages, 1994/07
Main features were studied about an objective deep sea reactor, which will be used as an electric power source at an unmanned deep sea base. The main features determined are as follows. [Thermal power 190 kWt, Fuel Mixed nitride, Cladding material Hasteloy N, Structual material Type 316 Stainless Steel, Coolant NaK, Core height and diameter about 25cm both, Reactor vessel outlet/inlet temperature 605/ 505
C, Operation term 10 years.] Some topic subjects of a talk during deep sea reactor research were studied like follows. Availability of electric transmission from the land or a ship is as follows. (1)The electric transmission from the land is limited up to 1,000m in the depth of water and 100km in the distance from the land. (2)The electric transmission from a ship is available only in the days when the sea is calm. Therefore these transmission methods can not be used as the power source for the base. Concerning reliability, reliability analysis were performed about the part of Closed Brayton Cycle Systems of the reactor. Success probability calculated on the part was 0.999942 in the case of continuous four years operation at 20 kWe. Concerning safety, radioactivity contained in the reactor was calculated. The radioactivity was about 1/50,000 of the radioactivity thrown away in the north Atlantic Ocean from 1962 to 1982. Concerning the experience of developping a NaK cooling reactor in U.S., no anormaly was reported to be found in fuel pins and a reactor vessel after about 400 days operation under a reactor outlet temperature condition over about 527C in the test of a ground test reactor FS-3 for SNAP-10A about thirty years ago.
