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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.
Jo, Takahisa; Goto, Takehiro; Yabuki, Kentaro; Ikegami, Kazunori; Miyagawa, Takayuki; Mori, Tetsuya; Kubo, Atsuhiko; Kitano, Akihiro; Nakagawa, Hiroki; Kawamura, Yoshiaki; et al.
JAEA-Technology 2010-052, 84 Pages, 2011/03
JAEA-Technology-2010-052.pdf:17.14MB
The prototype fast breeder reactor MONJU resumed the System Startup Test (SST) on May 6th 2010 after five months and fourteen years shutdown since the sodium leakage of the secondary heat transport system on December 1995. Core Confirmation Test (CCT) is the first step of SST, which consists of three steps. CCT was finished on July 22nd after 78 days tests. CCT is composed 20 test items including control rods' worth evaluation, radiation dose measurement etc..
Goto, Takehiro; Tsushima, Hiroyuki; Sakurai, Naoto; Jo, Takahisa
Proceedings of 14th International Conference on Nuclear Engineering (ICONE-14) (CD-ROM), 13 Pages, 2006/07
MONJU is a prototype fast breeder reactor. Modification work commenced in March 2005. Since June 2004, MONJU has changed one-loop operation of the primary heat transport system with all of the secondary heat transport systems drained of sodium. Purposes of this change are to shorten the modification period and to reduce the cost incurred for circuit trace heating electrical consumption. Before changing condition, the following issues were investigated to show that this mode of operation was possible. The heat loss from the reactor vessel and the single primary loop must exceed the reactor core decay heat by an acceptable margin but the capacity of the preheater to keep the sodium within the primary vessel at about 200
C must be maintained. With regard to heat loss and core decay heat, the estimated heat loss in the primary system was in the range of 90-170kW in one-loop operation, and the calculated reactor decay heat was 21.2kW. Although the heat input of the primary pump was considered, it was clear that circuit heat loss greatly exceeded the core decay heat. As for the preheater, effective capacity was less than the heat loss. Therefore, the temperature of the reactor vessel room was raised to reduce the heat loss. One-loop operation of the primary heat transport system was able to be executed by means of these measures. The cost of electrical consumption in the power plant has been reduced by one-loop operation of the primary heat transport system. The modification period was shortened.
Naruse, Keiji; Matsui, Kazuaki; Obata, Ikuhito; Sawazaki, Hiromasa; Goto, Takehiro; Jo, Takahisa
no journal, ,
no abstracts in English
Nishino, Yuki; Kuramoto, Shimpei; Naruse, Keiji; Nishino, Hajime; Goto, Takehiro; Takeuchi, Toru
no journal, ,
no abstracts in English
Kobayashi, Hideharu; Naruse, Keiji; Hirako, Kazuhito; Sawazaki, Hiromasa; Goto, Takehiro; Obata, Ikuhito; Matsui, Kazuaki
no journal, ,
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.
Ono, Fumiyasu; Fukushima, Tsubasa; Naruse, Keiji; Matsui, Kazuaki; Obata, Ikuhito; Sawazaki, Hiromasa; Goto, Takehiro; Jo, Takahisa; Uchihashi, Masaya
no journal, ,
By storing fuel assemblies in the fuel pond in Phase 1, MONJU eliminates the residual risk of fuel assemblies remaining in the core, which holds chemically active liquid sodium, and from April 2023, Have moved to Phase 2 of decommissioning. As the decommissioning progresses, plant risks will continue to change. Therefore, we will organize the plant status at each Phase of decommissioning and formulate the concept of performance maintenance facilities for MONJU, which will be necessary in Phase 2, and Performance maintenance facilities were Reconsidered.