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17 type PWR fuel cladding tube under LOCA-simulated burst conditionsFurumoto, Kenichiro; Udagawa, Yutaka
Journal of Nuclear Science and Technology, 60(5), p.500 - 511, 2023/05
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)Marufuji, Takato; Sato, Takumi; Ito, Hideaki; Suzuki, Hisashi; Fujishima, Tadatsune; Nakano, Tomoyuki
JAEA-Technology 2019-006, 22 Pages, 2019/05
JAEA-Technology-2019-006.pdf:2.84MB
Radioactive contamination incident occurred at Plutonium Fuel Research Facility (PFRF) in Oarai Research and Development Institute, Japan Atomic Energy Agency on June 6, 2017. During inspection work of storage container containing nuclear fuel materials, the PVC bag packaging in the storage container ruptured when a worker opened the lid in the hood, and a part of contents was spattered over the room. The cause of the increase of internal pressure of the storage container was gas generation by alpha radiolysis of the epoxy resin mixed with nuclear fuel materials. Opening inspection of about 70 similar containers stored in PFRF has been planned to confirm the condition of the contents and to stabilize the stored materials containing organic compounds. For safe and reliable open inspection of the storage containers with high internal pressure in the glove box, it is necessary to develop a pressure-resistant chamber in which the storage containers are opened and the contents are inspected under gastight condition. This report summarizes the concerns and countermeasures of the chamber design and the design results of the chamber.
Nakahira, Masataka
JAERI-Research 2005-030, 182 Pages, 2005/09
JAERI-Research-2005-030.pdf:12.57MB
It is difficult for Vacuum Vessel (VV) of ITER to apply a non-destructive in-service inspection (ISI) and then new safety concept is needed. Present fabrication standards are not applicable to the VV, because the access is limited to the backside of closure weld of double wall. Fabrication tolerance of VV is 
5mm even the structure is huge as high as 10m. This accuracy requires a rational method on the estimation of welding deformation. In this report, an inherent safety feature of the tokamak is proved closing up a special characteristic of termination of fusion reaction due to tiny water leak. A rational concept not to require ISI without sacrificing safety is shown based on this result. A partial penetration T-welded joint is proposed to establish a rational fabrication method of double wall. Strength and susceptibility to crevice corrosion is evaluated for this joint and feasibility is confirmed. A rational method of estimation of welding deformation for large and complex structure is proposed and the efficiency is shown by comparing analysis experimental results of full-scale test.
Nakahira, Masataka; Shibui, Masanao*
Nihon Kikai Gakkai Dai-9-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu, No.04-2, p.267 - 272, 2004/06
A small water leak can cause a plasma disruption in a tokamak-type fusion machine. This plasma disruption will induce electromagnetic (EM) force acting in the vacuum vessel that is a physical barrier of tritium and activated dust. If the VV can sustain an unstable fracture by the EM force, the structural safety will be assured and the inherent safety will be demonstrated. Therefore, a new analytical model to evaluate the through crack and leak rate of cooling water is proposed, with verification by experimental leak measurements. Based on the analysis, the critical crack length to terminate plasma in ITER is evaluated as about 2 mm. On the other hand, the critical crack length for unstable fracture is obtained as about 400 mm. It is concluded that EM forces induced by the small leak to terminate plasma will not cause unstable fracture of the VV; thus the inherent safety is demonstrated.
Nakahira, Masataka
Journal of Nuclear Science and Technology, 41(2), p.226 - 234, 2004/02
Times Cited Count：1 Percentile：9.98(Nuclear Science & Technology)A tokamak-type fusion machine is said to have inherent safety associated with plasma shutdown. A small leak of water can terminate the plasma safely and can cause a plasma disruption which will induce electromagnetic(EM) forces in the vacuum vessel (VV). From a radiological safety view point, the VV forms the physical barrier that encloses tritium and activated dust. If the VV can sustain an unstable fracture by EM forces from a through crack to cause the leak, the structural safety will be assured and the inherent safety will be demonstrated. Therefore, a systematic approach to assure the structural safety is developed. A new analytical model to evaluate the through crack and leak is proposed, with verification by experiment. Based on the analyses, the critical crack length to terminate plasma is evaluated as about 2 mm, and the critical crack length for unstable fracture is obtained as about 400 mm. It is therefore concluded that EM forces induced by small leak to terminate plasma will not cause the unstable fracture of VV, and then the inherent safety is demonstrated.
Nakahira, Masataka
JAERI-Tech 2003-087, 28 Pages, 2003/12
JAERI-Tech-2003-087.pdf:1.74MB
A tokamak-type fusion machine has been characterized as having inherent plasma shutdown safety. An extremely small leakage of cooling water will cause a plasma disruption. This plasma disruption will induce electromagnetic forces (EM forces) acting in the vacuum vessel (VV) which forms the physical barrier enclosing tritium and activated dust. If the VV has the possibility of sustaining an unstable fracture from a penetrating crack caused by EM forces, the structural safety will be assured and the inherent safety will be demonstrated. This paper analytically assures the Leak-Before-Break (LBB) concept as applied to the VV and is based on experimental leak rate data of a through crack having a very small opening. Based on the analysis, the critical crack length to terminate plasma is evaluated as about 2 mm. On the other hand, the critical crack length for unstable fracture is obtained as about 400 mm. It is therefore concluded that EM forces induced by small leak to terminate plasma will not cause the unstable fracture of VV, and then the inherent safety is demonstrated.
Konno, Chikara; Oyama, Yukio; Maekawa, Fujio; Ikeda, Yujiro; Kosako, Kazuaki*; Maekawa, Hiroshi; M.A.Abdou*; Bennett, E. F.*; A.Kumar*; M.Z.Youssef*
Fusion Technology, 28(2), p.347 - 365, 1995/09
no abstracts in English
Konno, Chikara; Oyama, Yukio; Maekawa, Fujio; Ikeda, Yujiro; Kosako, Kazuaki*; Maekawa, Hiroshi; M.A.Abdou*; A.Kumar*; M.Z.Youssef*
Fusion Engineering and Design, 28, p.708 - 715, 1995/00
no abstracts in English
Nakamura, Hideo; Kukita, Yutaka
Int. Conf. on New Trends in Nulear System Thermohydraulics,Vol. 1, 0, p.77 - 86, 1994/00
no abstracts in English
Hiratsuka, Hajime; Kawasaki, Kozo; Miyo, Yasuhiko; *; *; Shimizu, Masatsugu; ; Onozuka, Masanori*; Shimomura*; *; et al.
Fusion Engineering and Design, 13, p.417 - 424, 1991/00
Times Cited Count：4 Percentile：47.81(Nuclear Science & Technology)no abstracts in English
; *; ;
Nihon Kikai Gakkai Rombunshu, A, 52(477), p.1228 - 1231, 1986/00
no abstracts in English
; ; ; ;
JAERI-M 8497, 27 Pages, 1979/10
no abstracts in English
