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JNC TN9410 2000-003, 52 Pages, 1999/12
JNC-TN9410-2000-003.pdf:3.51MB
In May, 1999, disassembly and cleansing of sodium residues contained in the large cold trap (50MWSG) were carried out. Two cold trap units, one from the primary sodium loop and the other from the for the secondary sodium loop were disassembled and cleaned. This report describes the procedures, methods, and tasks under taken in the clean-up effort, including countermeasures for safe handling of sodium. The disassembly of the cold trap was based an information regarding similar cleansing activities external to JNC. There was also same a priori knowledge of the type and amount of sodium-laden residues. As this result, we conducted disassembly and cleansing task as provisionally planned. In fact we learned that disassembly methods for the specific components could be conducted in an aerated atmosphere. We thus gained additional disassembly and sodium cleansing experience under manageable and safe conditions.
; Kano, Yutaka; ; Shindo, Katsutoshi
JNC TN9410 2000-001, 20 Pages, 1999/12
JNC-TN9410-2000-001.pdf:1.84MB
The 12th periodic inspection had been executed at the experimental fast reactor JOYO from February 24,1998 to June 28,1999. This inspection had been extended about three months because it was addtion to the work for the safety countermeasure. The result of collective dose equivalent was 263.92 man*mSv, whereas, the expected collective dose equivalent was about 407 man*mSv in the whole period of this inspection. It was confirmed that this inspection was carried out with the suitable radiation protection programmes. In this report, provided in 12th periodic inspection, were described with taking the results of the past periodic inspections into consideration.
*; *; Tanai, Kenji
JNC TN8400 99-050, 94 Pages, 1999/11
This paper reports on the evaluations of operational activities for a High Level Radioactive Wastes Disposal Facility, from initial acceptance of vitrified waste at a surface facility to emplacement engineered barriers in underground facilities. The purpose of this analysis is to confirm the technical feasibility of geological disposal. First, the basic design and repository system requirements are identified. Second, operational activities in surface facilities, access facilities and underground facilities are described. The required procedures and equipment, suitable for specific emplacement concepts and configurations for engineered barrier systems are discussed for specific examples. Countermeasures for potential adverse events or conditions are based on extensive civil engineering and mining experiences in Japan and abroad. The time schedule is also evaluated on the basis of these concepts. In addition, the concept of stationary and mobile radiation control areas is studied based on experiences and practice in current nuclear facilities. Finally future research and development items are summarized.