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JAEA Reports

Study of safety aspects for pyrochemical reprocessing systems


JNC-TN9400 2000-051, 237 Pages, 2000/04


In this study, we have proposed the concept of safety systems (solutions of safety problems) in pyrochemical reprocessing systems (lt consists of pyrochemical reprocessing methods and the injection casting process for the metal fuel fabrication, or vibro-packing process for the oxide fuel fabrication.) which has different concept from the existing PUREX reprocessing method and pellet fuel fabrication process. And we performed its safety evaluations. FoIlowing the present Japanese safety regulations for reprocessing facilities, we pointed out functions, design requirements and equipments relating to its safety systems and picked up subjects. For the survey of safety evaluations, we first selected anticipated events and accident events, and second by evaluated 6the correspondence of the limitation of the public exposure to the accidents above, by using two parameters, the safety design parameter (the filter performance to confine radioactive matelials) and the leak inventory of radioactivities, and last by picked up its problems. ln addition to the above evaluations we performed basic criticality analyses for its systems to utilize these results for the design and evaluation of the criticality safety management system. Thus this study specified the concept of safety systems for pyrochemical reprocessing processes and then issues in order to establish safety design policies (matters which must consider for the safety design) and guides and to advance more definite safety design.

JAEA Reports

Design of the HLW buffer

; Fujita, Tomoo; ; Iwasa, Kengo; Hasegawa, Hiroshi

JNC-TN8400 99-096, 23 Pages, 1999/12


The Japan Nuclear Cycle Development Institute (JNC) has prepared a second progress report (entitled H12) on research and development for geological disposal of high-level waste (HLW) in Japan. H12 report consist of a Project Overview Report and three Supporting Reports which cover the three major fields described in the AEC Guidelines: (1)evaluation of the geological environment, (2)repository design and engineering technology, (3)performance assessment. This report is prepared to explain background information of buffer design which is descried in Supporting Report 2 (Repository Design and Engineering Technology). In buffer design of H12 report, the design requirements of the buffer are assumed and the relationship between buffer thickness and density was shown corresponding design requirement as an area map. This report describes the background information such as the numerical formulations, assumptions, engineering judgement and so on.

JAEA Reports

Design concepts for overpack

*; *; Tanai, Kenji

JNC-TN8400 99-047, 54 Pages, 1999/11


This paper reports on the design process for a carbon-steel overpack as a key component in the engineered barrier system of a deep geological repository described in the 2nd progress report. The results of the research and development regarding design requirements, configuration, manufacturing and inspection of overpack are also described. The concept of a composite overpack composed of two different materials is also considered. First, the design requirements for an overpack and presume environmental and design conditions for a repository are provided. For a candidate material of carbon steel overpack, forging material is selected considering enough experience of using this material in nuclear power boilers and other components. Second, loading conditions after emplacement in a repository are set and the pressure-resistant thickness of overpack is calculated. The corrosion thickness to achieve an assigned 1000 year life time and the required thickness to prevent radiolysis of ground water which might enhance corrosion rate are also determined. As aresult, the total required thickness of a carbon-steel overpack is conservatively estimated to 190 mm. This is a reduction of about 30% from the previous estimate provided in the 1st Progress Report. Additional items that must be considered in manufacturring and operating overpacks (i.e. sealing of vitrified waste, examination of main body and sealing welding, mechanism of handling) are evaluated on the basis of current technology, specific future data needs are identified. With respect to the concept of composite overpack (i.e., an outer vessel to provide corrosion-allowance or corrosion-resistant performance and an inner vessel to provide pressure-resistance), the differences in design concepts between the carbon-steel overpack and such composite overpacks are analyzed. Future data needs and analytical capabilities with respect to overpacks are also summarized.

JAEA Reports

Investigations on repository layouts

Tanai, Kenji; Iwasa, Kengo; Hasegawa, Hiroshi; Goke, Mitsuo*; Horita, Masakuni*; Noda, Masaru*

JNC-TN8400 99-044, 140 Pages, 1999/11


This report consists of three items: (1)Study of the repository configuration, (2)Study of the surface facilities configuration for construction, operation and buckfilling, (3)Planning schedule, In the repository configuration, the basic factors influencing the design of the repository configuration are presented, and the results of studies of various possible repository configurations are presented for both hard and soft rock systems. Here, the minimum conditions regarding geological environment required to guide design are assumed, because it is difficult to determine the repository configuration without considering specific conditions of a disposal site. In the surface facility configuration, it is illustrated based on the results of construction, operation, buckfilling studies for underground disposal facility and EIS report of CANADA. In the schedule, the overall schedule corresponding to the repository layout is outlined in link with the milestone of disposal schedule set forth in the government's basic policy. The assumptions and the basic conditions are summarized to examine the General Schedule from start of construction to closure of a repository. This summaly is based on the technologies to be used for construction, operation and closure of a repository. The basic national policies form the framework for this review of the general schedule.

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