[en] A batch operation of charging temperature-elevated nitric acid and waste resins (spent ion exchange resin containing radioactive nuclides) into a nuclide separating vessel and stirring, and drawing nitric acid solution after the completion of the stirring are repeated for a number of times, thereby separating radioactive nuclides from spent ion exchange resins. In this case, it is preferred that the temperature of the nitric acid is from 80 to 90degC, and stirring is continued for about 1 hour for 1 batch operation. In particular, it is preferred to use 2-N nitric acid, equalize the injection amount thereof with that of the spent ion exchange resins and repeat the batch operation from 10 to 15times. With such procedures, radioactive nuclides can be separated efficiently from resin wastes having relatively large amount of deposited cruds. In addition, the amount of nitric acid to be used can be reduced. (T.M.)

[en] Heavy water recycling and tritium internal dose reduction are key issues for the heavy water handling technology in the Fugen Nuclear Power Station. Heavy water upgrading has been performed by two upgraders, namely Upgrader-1 and Upgrader-2. Although the original 160 ton of heavy water was imported from the former West Germany, Norway, United States, and China, no heavy water has been imported after the completion of the Upgrader-2 in 1987. Annual tritium internal dose has been suppressed to less than 0.02 person·Sv with very tight structure of the heavy water system and a specific radiation protection method in the Fugen. This paper describes operating performance of heavy water upgraders, and Tritium effulent control experience in Fugen. 3 refs., 3 tabs., 18 figs

[en] Tritium is generated mainly from the activation of the heavy water moderator at Fugen. Its control is a key issue for heavy water handing technologies there. This paper describes the equipment considerations, methods of tritium monitoring, radiation work control, gaseous/liquid emission control, and personnel dose management for tritium that were developed and improved through the more than two decades of operation of the Fugen Nuclear Power Station. (author)

[en] Latest nuclear power plants require advanced control techniques in the water quality control for reactor coolant water as the measures to prevent stress corrosion cracking and to reduce exposure dose. To meet these requirements, the analysis in ppb or ppt (parts per trillion) level is often necessary. In such super-micro trace analysis, an analyst must pay very close attention. Specifically, the analysis of anions by absorptiometry or solvent extraction is insufficient in the sensitivity and requires hands. To overcome these difficulties, an ion chromatograph system has been for the first time introduced and tested in the ''Fugen'' plant. The system is initially used for chlorine ion analysis, but presently successfully applied to the analysis of almost all anions. In this paper, the circumstances of its introduction, the outline of the system and the application to the ''Fugen'' plant are described. One of its features is the capability of performing micro trace analysis in a short time. Though the precision of the analysis has only one or two digits of significant figure, it seems to be very suitable for the water quality analysis in nuclear power plants, which needs highly sensitive detection of low concentration materials. (Wakatsuki, Y.)

[en] The Fugen Power Station started the full scale operation in March, 1979, and it has become clear that water quality control or water chemistry is very important for the operation management of the reactor, from the operational experience for about 4 years such as the stress corrosion cracking of reactor cooling pipes, the lowering of performance of the resin for heavy water purification, the increase of radiation dose rate due to corrosion products and so on. The chemical management for the Fugen is mainly the water quality control of heavy water moderator and reactor cooling water. The control of heavy water is mainly the control of the concentration of deuterium in helium and the maintenance of the water quality by removing impurities accumulating in the heavy water. The various countermeasures to extend the life of the resin for heavy water purification were taken. Mixed bed deionizers are used for removing fission products and corrosion products in the reactor purification system and the feed water and condensate system. As the other chemical management, the control of cooling water for reactor auxiliary equipment and the control of cooling water for shielding are carried out. (Kako, I.)

[en] The ATR Fugen is the prototype reactor of heavy water-moderated, boiling light water-cooled pressure tube type, and the power station started the full scale operation in March, 1979. Through the operation for more than 5 years, it has accomplished the role of verifying the technical development of ATRs. As of the end of March, 1984, Fugen has attained the average capacity ratio of 58.8%, and now, it has just completed the fourth regular inspection. Through these operational experience, it has been endeavored to accumulate the technology of utilizing plutonium and that of the plant systems for pressure tube type reactors, and to verify the operational reliability and maintainability of ATRs. In this paper, the operational experience concerning the chemical control is summarized. First, the Fugen Power Station is outlined. In this reactor, heavy water is used as the moderator, consequently, the neutron economy and the efficiency of using nuclear fuel are superior to those of LWRs. As the experience of chemical control, the decomposition of heavy water, the extension of the life of resin for heavy water purifying system, the measures to reduce radioactive crud and the measures to prevent stress corrosion cracking in reactor cooling water, and the control of other cooling water are reported. (Kako, I.)

[en] Applicability of the zinc injection technique for reducing the equivalent dose of annual inspection workers has been cleared and confirmed by several out-of-pile tests at Fugen Nuclear Power Station. A trial, which aimed at compressing the dose rate increase, was developed by BWR and was carried out in several plants from 1986. And then, regular zinc injections were started from Aug. 1999 after the start up of the 15^th annual inspection. As a result of this injection, the ⁶⁰Co ion concentration in reactor has been reduced by the order of about 30%, and a radioactivity reduction effect has also been confirmed. Also, the rebuild up rate of ⁶⁰Co on piping surfaces has been drastically reduced from about 60% to about 12% after system decontamination. According to an analysis of the practical method, the adhesive rate coefficient of ⁶⁰Co to metal oxide film is compressed to about 1/3. (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] Based on the report titled Activities of Fugen NPS after permanent shutdown, Fugen has been preparing for the project, including necessary development of technologies. The development of decommissioning for Fugen is divided into two areas. One area is development of unique technology for dismantling special components such as the reactor core and the heavy water system. Another area is improvement and enhancement of existing technologies. Especially, the former area requires effort and comprises development of the reactor dismantlement, tritium decontamination of heavy water system and engineering support systems. Moreover, the technical results of technology development and decommissioning activity should be organized and opened to the public so that they can contribute to other decommissioning projects. For this purpose, information exchange and co-operation with domestic and international organizations are underway. (author)

[en] An activity removal method from spent ion exchange resin was developed in the Fugen Nuclear Power Station. Nitric acid of 2N is used as the eluent of spent resin. Cobalt 60 in the spent resin was reduced from 700 kBq/cm³ to less than 7 kBq/cm³ after ten batches of one hour stirring at 90degC. Nitric acid of 18 cm³ was stirred with the same volume of spent resin in each batch. After this treatment the spent resin is available to be burned in the incinerator of the Fugen. Stabilizing way of the effluent nitric acid is under development. (author)