Takiya, Hiroaki; Kadowaki, Haruhiko; Matsushima, Akira; Matsuo, Hidehiko; Ishiyama, Masahiro; Aratani, Kenta; Tezuka, Masashi
JAEA-Technology 2020-001, 76 Pages, 2020/05
Advanced Thermal Reactor (ATR) FUGEN was operated for about 25 years, and now has been proceeding decommissioning after the approval of the decommissioning plan in Feb. 2008. The reactor, heavy water system and helium system are contaminated by tritium because of neutron absorption of heavy water, which is a moderator. Before dismantling these facilities, it is necessary to remove tritium from them for not only reducing the amount of tritium released to surrounding environment and the risk of internal exposure by tritium but also ensuring the workability. In first phase of decommissioning (Heavy Water and Other system Decontamination Period), tritium decontamination of the reactor, heavy water system and helium system started in 2008 and completed in 2018. This report shows the results of tritium decontamination of the reactor, heavy water system and helium system.
Tachibana, Mitsuo; Murata, Masato; Tasaki, Tadayuki; Usui, Hideo; Kubota, Shintaro
Proceedings of 21st International Conference & Exhibition; Nuclear Fuel Cycle for a Low-Carbon Future (GLOBAL 2015) (USB Flash Drive), p.1987 - 1996, 2015/09
230 various types of nuclear facilities were constructed in JAEA's R&D Institutes or Center until the establishment of the JAEA in 2005. The JAEA has efficiently and systematically decommissioned nuclear facilities that would no longer be required after the establishment of the JAEA. Decommissioning of nuclear facilities in each JAEA's R&D Institutes or Center was continued based on the second midterm plan of the JAEA from FY2010 to FY2014. Decommissioning of 2 nuclear facilities was completed during the second midterm. This report describes current status of decommissioning activities in the JAEA during the second midterm and outline of the decommissioning plan in the third midterm.
Iwai, Hiroki; Nakamura, Yasuyuki; Mizui, Hiroyuki; Sano, Kazuya; Morishita, Yoshitsugu
Proceedings of 7th International Congress on Laser Advanced Materials Processing (LAMP 2015) (Internet), 4 Pages, 2015/08
The reactor of FUGEN is characterized by its tube-cluster construction that contains 224 channels arranging both the pressure and the calandria tubes coaxially in each channel. And the periphery part of the core has the laminated structure of up to 150 mm thickness of carbon steel for radiation shielding. Method for dismantling the reactor core is also being studied with considering processes of dismantlement by remote-handling devices under the water for the radiation shielding. In order to shorten the term of the reactor dismantlement work and reduce the secondary waste, some cutting tests and literature research for various cutting methods had been carried out. As the result, the laser cutting method, which has feature of the narrow cutting kerf and the fast cutting velocity, was mainly selected for dismantling the reactor. In this presentation, current activities of FUGEN decommissioning and R&D of laser cutting tests are introduced.
Hidaka, Akihide; Kudo, Tamotsu; Fuketa, Toyoshi
Transactions of the American Nuclear Society, 91, p.499 - 500, 2004/12
The radionuclides release from MOX under severe accident conditions was investigated in the VEGA program to prepare the technical bases for safety evaluation including PSA for LWR using MOX. The MOX specimen irradiated at ATR Fugen was heated up to 3123K in He at 0.1MPa. The Cs release started at about 1000K and was enhanced below 2200K compared with that of UO. The possible reason is due to the formation of cracks connected to the high burn-up Pu spots. The total fractional releases were evaluated by alpha-ray, gamma-ray and ICP-AES and compared with the ORNL-Booth model. Although the model was prepared based on the tests with UO, the predictions are in reasonable agreement with the measurements. The VEGA test showed that the total releases from MOX are almost the same as those from UO under extremely severe accident conditions. This indicates that the consequences of LWR using MOX are mostly equal to those using UO. The effect of difference between MOX and UO on the consequences will be systematically investigated using the JAERI's source term code, THALES-2.
Iguchi, Yukihiro*; Kanehira, Yoshiki*; Tachibana, Mitsuo*; Johnsen, T.*
Journal of Nuclear Science and Technology, 41(3), p.367 - 375, 2004/03
The Fugen Nuclear Power Station (NPS) was shut down permanently in March 2003, and preparatory activities are underway to decommission the Fugen NPS. An engineering system to support the decommissioning is being developed to create a dismantling plan using state-of-the-art software such as 3-dimentional computer aided design (3D-CAD) and virtual reality (VR). In particular, an exposure dose evaluation system using VR has been developed and tested. The total system can be used to quantify radioactive waste, to visualize radioactive inventory, to simulate the dismantling plan, to evaluate workload in radiation environments and to optimize the decommissioning plan. The system will also be useful for educating and training workers and for gaining public acceptance.
PNC TN3410 98-002, 34 Pages, 1998/01
A new and improved Graphical User Interface (GUI) to the Modular Accident Analysis Program for FUGEN (MAAP/FUGEN) has been developed and implemented at Fugen. The new user interface is a superset of the existing GUI to MAAP - the MAAP/FUGEN/GRAAPH - in the meaning that it contains all the features of the GRAAPH, but in addition offers a number of new features. The new interface, named MAAP-PICASSO is based on the Picasso-3 technology developed by Institutt for Energiteknikk/OECD Halden Reactor Project. The main difference between the MAAP-PICASSO and MAAP-FUGEN-GRAAPH GUIs is that the MAAP-PICASSO GUI is completely decoupled from the numerical simulator. This gives a far higher flexibility regarding enhancement of the GUI, connection to other, external software and user friendliness. It also includes techniques for presenting 2 byte character set - i.e. displaying text in Japanese characters. A special software has been developed for automatic extraction and reuse of the graphical plant information provided in MAAP/GRAPH into Picasso language. This software-has been demonstrated not only on the Fugen plant data, but also other Nuclear Power Plant picture definitions provided by Fauske Inc. The new GUI requires a minimal modification of the MAAP code itself However, these modification is only for parameter communication and is not intrusive to the numerical computations of MAAP itself. The GUI has been developed using modular and object-oriented programming techniques, which makes it relatively easy to extend and modify to fulfill present and future requirements from the users at Fugen, and makes it compatible with future versions of the MAAP code. MAAP-PICASSO is developed on and currently running only on HP UNIX workstations. However, a new NT-based version of Picasso-3 will be released from the Halden Project in February 1998. This will further enhance the applicability and usability of the MAAP-PICASSO GUI.
Yuasa, Toyotaka; Abe, Teruyoshi; Nakamura, Takahisa; Myochin, Munetaka; Takagi, Hisatsugu
no journal, ,
Suffered SCC (stress corrosion cracking) at the primary cooling system in 1980, the Fugen power station introduced the three preventive technologies immediately. After the upgrade of the plant, no SCC occurred during the operation period. We have inspected the actual structural materials of the Fugen power station on its decommissioning stage to evaluate effectiveness of SCC management technologies, which are combining material replacement, induction heating stress improvement (IHSI) to reduce the welding residual tensile stress, and application of hydrogen addition to reduce oxygen in the water. No crack in the materials was found by metallurgical structure observation. Moreover, judging from the analysis of residual stress and the heat affected zone in the materials, the effectiveness of SCC management technologies was verified.