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Tanai, Kenji; Iwasa, Kengo; Hasegawa, Hiroshi; Miura, K.*; Okutsu, Kazuo*; Kobayashi, Masaaki*
JNC TN8400 99-046, 177 Pages, 1999/11
For the construction of underground facilities comprising access tunnels, connecting tunnels, main tunnels and disposal tunnels, a large number of tunnels will be excavated in deep rock formations. These excavations will extend hundreds kilometers in total length. Therefore, special attention must be paid, to transporting large volume of debris, ventilation, emergency escape routes in case of accident, and other factors. In addition, special attention must also paid to potential accidents which might in underground excavations, including unstable facing phenomena (such as collapse and swelling of facing at weak layer sections), spring water flow resulting collapse of rock, gas eruption, and rock burst. While considering these factors to be emphasized during the construction of geological disposal facilities, the investigation reviewed the existing working methods on individual construction technologies of access tunnels, main tunnels, connecting tunnels, disposal tunnels, and disposal pit, based on the recognition that the present state deals with a wide range of geological environments, and conducted investigation about the construction methods for each tunnel on the basis current technologies, and described the outline of these methods. Furthermore, for the items to be particulaly emphasized on site characterization koko and siting data such as ground pressure and spring water, the investigation reviewed the current countermeasure works, and made survey on the phenomena appeared during actual tunnel construction works and their countermeasres, and carried out a study on effectiveness of these countermeasures. This constructing of disposal site in deep geological formations is basically possible by applying, or confirming, current excavation technologies for tunnels and underground facilities, A systematic construction system combines separate technologies relating to construction, (excavation technology, tunnel support work method, etc.). Such systems ...
; ; Yamada, Takeshi; ; ; ; Kaito, Yasuaki; ; Kotaka, Yoshinori; ; et al.
PNC TN2410 96-005, 339 Pages, 1996/03
Construction of the 'Monju' fuel handling systems was completed in April, 1992. From March 1991 to August 1992, pre-commissioning tests were carried out. In December 1992, all the systems of Monju were transfered to PNC, and commissioning tests and reactor physics tests, were started. For the first time, during these physics tests, the fuel handling systems were operated for one of the commissioning tests 'Loading to Criticality', without significant problems. 168 fuel sub-assemblies were loaded into the core and the first criticality was achieved on 5th April 1994. The fuel handling systems continued in operation for the 'Loading to Full Size of the Core', power distribution test and for cleaning discharged dummy sub-assemblies. To keep these fuel handling systems working somothly and satisfactorily annual maintenance has been carried out since 1992. This paper describes the operation and maintenance experience of fuel handling systems after the pre-commissioning tests and future study items for system reliability improvement.
