[en] A concept of commercial ATR (Advanced Thermal Reactor; heavy water moderated boiling light water cooled reactor) is studied for a large 1000MWe class plant to realize improvement of core performance and reduction of construction cost related to the major components and systems. As a result of the study, a concept of long cluster type fuel core with many small diameter fuel pins is proposed to minimize the increase of core size and to improve the core performance, and the total material weight used for reactor structure and reactor cooling system components and pipings is confirmed to be less than that of DATR (ATR demonstration plant, 606MWe) by adopting concepts of the combined structure of a calandria tank and an upper thermal shield vessel (partially integrated reactor), and the combined structure of a steam drum, a water drum and recirculation pumps (integrated drum using internal pumps.) (author)

[en] Hydrogen water chemistry (HWC) was applied to the Fugen Nuclear Power Station. This is the first application of HWC in Japan as a countermeasure against stress corrosion cracking (SCC) of Type 304 stainless steel. After one year of experimental HWC, critical oxygen concentration range was determined as 10∼15 ppb to protect sensitized Type 304 stainless steel from SCC. Corrosion potential corresponding to this oxygen concentration ranged -210∼-250 mV (vs. SHE). No significant dose increase or local hydrogen accumulation was observed with HWC. Hydrogen has been injected continuously since 1985 with a water electrolysis hydrogen/oxygen generating system. Integrity of the materials constituting reactor cooling system other than Type 304 stainless steel was also confirmed in in-plant and laboratory autoclave tests. (author)

[en] This paper presents an outline of developing plan of a target system and topics obtained by a pre-conceptual design, which aims to establish a technology base of the target system and to make clear a system concept. In the plan, two types of target - solid and mercury targets - are to be developed for a neutron scattering facility. Information obtained through the development shall be applied to designs of an irradiation and a transmutation facilities. Through the pre-conceptual design, system arrangement, scale etc. were made clear: total weight will be 12000 ton, and 26 beam lines with beam shutters will be equipped for 4 moderators. Engineering problems were also made clear through the design; high flux heat removal, dynamic stress caused by thermal shock and pressure wave, loop technology for the mercury target and a slurry moderator consisting of methane pellets and liquefied hydrogen. We are now constructing new test apparatuses and arranging computer codes for solving these problems. (author)

[en] In the development of a new chemical decontamination method which provides a high decontamination effect, less corrosion of base metal, and less radioactive waste generation, we developed a decomposition method for oxalic acid coexisting with hydrazine to decrease the amount of radioactive waste. Using a catalyst of 0.5wt% Ru supported by activated carbon grains, we decomposed oxalic acid and hydrazine, simultaneously and efficiently, with a stoichiometric concentration of H₂O₂. The decomposition ratios were decreased by the deposition of oxides. But even if the simulated reducing agent solution with high concentrations of coexisting Fe and K ions, which negatively effect decomposition ratio, was decomposed, the decomposition ratios of oxalic acid and hydrazine were kept high during decomposition of the amount of reducing agent used in actual chemical decontamination. Additionally, we examined the deposition ratios of metal ions on the catalyst as metal oxides. These results indicated about 2% of the radioactive species which were removed by the chemical decontamination were deposited on the catalyst column. ⁵⁹Fe and ⁵¹Cr were estimated to be about 90% of the total deposited amount of radioactive species and about 60% of the dose equivalent in the model calculation. But this problem should be easily dealt with by using shielding. (author)

[en] A new low corrosive decontamination method was developed which uses both oxalic acid and hydrazine as the reducing agent and potassium permanganate as the oxidizing agent. Less corrosion of structural materials during the decontamination is realized by pH control of the reducing agent. The pH of 2.5, attained by adding hydrazine to oxalic acid, was the optimum pH for maintaining a high decontamination effect and lowering the corrosion at the same time. As this reducing agent can be decomposed into carbon dioxide, nitrogen and water by using a catalyst column with hydrogen peroxide, the amount of secondary radioactive waste is small. These good features were demonstrated through actual plant decontamination tasks. (author)

[en] This feature article describes the current state of practical particle beam therapy of cancer, its future prospect, recent opening/construction of its facilities and manufacturers' view with following 9 topics presented by relevant experts. Gunma University (topic 1) started the carbon ion therapy from Mar., 2010, and has treated more than 100 cancer patients to aim the treatment of about 600 patients/year after several years. Fukui Prefectural Hospital Proton Therapy Center (topic 2) started from this March with proton beams for patients with its therapeutic standard, in cooperation with insurance companies and hotels for patients' convenience. Medipolis Proton Therapy and Research Center (Kagoshima Pref.) (topic 3) started this year with proton beams for 13 patients hitherto with reference protocol of Hyogo Ion Beam Medical Center. A new stereotactic irradiation system of proton beams for breast cancer has been developed. Construction of Saga Heavy Ion Medical Accelerator in Tosu (Saga Pref.) (topic 4) began this year to be completed in 2013. Aizawa Hospital (Nagano Pref.) (topic 5) plans to introduce the small-sized proton accelerator-gantry system (Sumitomo Heavy Ind., Ltd.) aiming the practice in 2013. Association for Nuclear Technology in Medicine (topic 6) reports the trends of current and future construction inside/outside Japan. Manufacturers comment their respective business: high-speed scanning irradiation system, next generation handling system of patient and particle beam therapy information system by Toshiba (topic 7); designation of the whole heavy ion beam therapy system (with NIRS), proton beam (as in topic 5) and system of BNCT (boron neutron-capture therapy) (Kyoto Univ.) by Sumitomo Heavy Ind., Ltd. (topic 8); and small-size proton therapeutic machine with 4D tracing capability for patient's movement (Hokkaido Univ.) and with spot-scanning irradiation technique by Hitachi (topic 9). (author)