Development Program of RAF and Materials Technology in Japan

摘要

RAF steel has been selected as a candidate material for a blanket structure of a prototype reactor in the intermediate term materials development program (approved by fusion council in June '00). RAF development has been conducted under the cooperation of JAERI and universities including supports and involvements of steel industries and national institutes for more than a decade. International collaboration under IEA implementing agreement and the Japan-US collaborations, JAERI-ORNL program and Monbusho-DOE program, have been important activities for the materials development. Since the establishment of the "office of fusion materials research promotion" in Naka Fusion Establishment, JAERI in 1998, the action to unify the RAF development activities in Japan has been initiated and emphasized toward the restructuring of government from 2001. This action has been enforced by the establishment of an official joint activity of RAF working group under JAERI and NIFS, as the managing institute for the fusion researches in universities since 2000. Design studies of prototype reactors using RAF steel have been conducted by JAERI for the Tokamak type reactors; SSTR and A-SSTR and by NIFS for the Helical type reactor; FFHR. The blankets are designed as water-cooled solid breeder systems and as a Flibe self cooling systems. As an important milestone, application of RAF to ITER test blanket has been also planned. Temperature of the structural material is designed to be in the range between 300-600C for these blankets. Potential issues of the materials are the degradation of fracture toughness by irradiation at relatively low temperatures and the deformation (including irradiation creep) at high temperatures under irradiation. The compatibility with high temperature coolants (water and Flibe) is also a subject to be solved. According to the current work scope, optimization of materials and process conditions, such as chemical composition, heat treatment, plastic deformation and joining/welding, has to be done by 2005. Strength and fracture behavior evaluation methods of simple model blanket structures have to be made during the time period based on sufficient neutron irradiated data. This will be one of the basics of design codes. The technology integrations of blanket fabrication, reduced activation steel fabrication, database development has to be synchronized with the basic activities. These are very ambitious plan requiring well-designed national program together with extensive international collaboration programs. In this meaning, IEA joint activity and on-going Japan-US collaboration programs have to be more emphasized and promoted. In the work scope, development of irradiation database with accelerator driven 14 MeV neutron source is to be started within several years after 2010.