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Kobayashi, Hideharu; Naruse, Keiji; Hirako, Kazuhito; Sawazaki, Hiromasa; Goto, Takehiro; Obata, Ikuhito; Matsui, Kazuaki
Proceedings of 31st International Conference on Nuclear Engineering (ICONE31) (Internet), 9 Pages, 2024/11
The prototype fast breeder reactor MONJU is a loop-type sodium-cooled nuclear reactor to be decommissioned in Japan. Japan Atomic Energy Agency (JAEA) started decommissioning of MONJU in 2018, and will complete four phases of the decommissioning in about 30 years. The first Phase is the Fuel Assembly Removal Period, during which secondary sodium was drained, the fuel assemblies in the reactor core were removed and put in the storage in the spent fuel pool, and the distribution of contamination in buildings, components, equipment, etc. was evaluated. In the second Phase, the Preparation for dismantling period, the neutron shields in the reactor core will be moved and put in the storage in the spent fuel pool in preparation for the dismantling of the sodium equipment, the transport of sodium, and the dismantling and removal of the water and steam power generation system. We also continue to assess the distribution of contamination in buildings, components, equipments, etc. The third Phase is the Decommissioning Period I, which includes the dismantling of sodium equipment, the transport of spent fuel, and the removal of the water and steam power generation equipment. The final Phase is the Decommissioning Period II. The radiation controlled area will be freed and all the buildings will be dismantled and removed. This paper provides an overview of MONJU decommissioning, the results of its First Phase, and details of the second Phase, which is currently underway.
Kobayashi, Hideharu; Hirako, Kazuhito; Sawazaki, Hiromasa; Goto, Takehiro
Hozengaku, 23(2), p.27 - 33, 2024/07
The decommissioning of the Monju prototype fast breeder reactor, which began in 2018, has completed sodium removal and solidification of the secondary sodium system and fuel body removal, the main processes of the first stage of decommissioning, and moved to the second stage of decommissioning from fiscal 2023. Following the previous issue of "Monju Decommissioning Trend - Part 1: Completion of the 1st stage of Monju decommissioning" (Maintenance Science vol.23 No.1, 2024), this report describes the outline of the 2nd stage of Monju decommissioning, the review of the performance maintenance facilities that will change with the progress of decommissioning, the construction of the maintenance programme according to the review, and the maintenance of the 3rd stage of Monju, which will start full-scale dismantling. The review of the performance maintenance facilities that will change with the progress of decommissioning, the construction of the maintenance program according to the review, and the maintenance of the 3rd stage of Monju, which will start full-scale dismantling.
Hirako, Kazuhito; Sawazaki, Hiromasa; Goto, Takehiro
Hozengaku, 23(1), p.9 - 13, 2024/04
The decommissioning of the prototype fast breeder reactor Monju, which started in 2018, has completed the extraction and solidification of the secondary sodium and the removal of the fuel body, which are the main processes in the first stage of decommissioning, and has moved to the second stage of decommissioning from 2023. This report provides an overview of the Monju decommissioning programme and the first stage of Monju decommissioning as "Trends of Monju decommissioning, Part 1". The actions in the second stage of Monju decommissioning will be explained in the next issue, including the outline and the review of the performance maintenance facilities that will change with the progress of the decommissioning and the construction of the maintenance programme accordingly.
Seki, Masayuki; Kihara, Yoshiyuki; Kaito, Takeji; Tsukada, Tatsuya*; Motoki, Kazuhiko*; Hirako, Kazuhito*
Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 5 Pages, 2011/12
Oxide Dispersion Strengthened (ODS) steel has been developed as an advanced fuel cladding tube for sodium cooled fast reactors in Japan Atomic Energy Agency (JAEA) to attain the target burn up of 150 GWd/t in the bundle average because of its excellent swelling resistance and high mechanical strength in high temperature. If conventional TIG welding is applied to the ODS welding, it is difficult to obtain necessary mechanical strength at the weld zone because of the formation of porosity. It is formed by the argon bubbles which initially dissolve in the matrix and grow up under the high temperature during welding. Therefore JAEA has been conducted the development of pressurized resistance welding (PRW) technology for ODS cladding tube, which is one of the solid state welding methods. This paper describes in the development of PRW technology, an ultrasonic test method for detecting weld defects, the result of machine strength measurement examination in weld part and the result of fuel pin irradiation examination using nuclear reactor.
Seki, Masayuki; Ishibashi, Fujio; Kihara, Yoshiyuki; Hirako, Kazuhito*; Tsukada, Tatsuya*
JNC TN8410 2005-009, 131 Pages, 2005/04
JNC-TN8410-2005-009.pdf:41.38MB
The development of the welding technology for the ODS steel was started in JFY1987. The first welding examination used the tungsten inert-gas (TIG) welding method and the YAG pulse laser welding method. However, the existing fusion welding methods significantly degrade strength at the welded section, because large size of blowholes appears at the weld and induce coagulation of oxides to generate coarser particles. To solve this problem, we have developed pressurized resistance welding (PRW) as a solid phase welding method.The appropriate conditions, e.g. electric current, voltage and contact force, were selected. For the PRW welded specimens, the tensile, internal burst and creep rupture tests were conducted and its integrity was confirmed. In addition, an ultrasonic inspection method has been developed to assure non-destructively integrity of the welding between cladding and end-plug.
Seki, Masayuki; Kihara, Yoshiyuki; Tsukada, Tatsuya*; Motoki, Kazuhiko*; Hirako, Kazuhito*
no journal, ,
no abstracts in English
Seki, Masayuki; Kihara, Yoshiyuki; Hirako, Kazuhito*; Motoki, Kazuhiko*; Tsukada, Tatsuya*
no journal, ,
no abstracts in English
