Adopting the 60-year design is regarded as one of the most effective means for the practical realization of Sodium-cooled Fast Reactor (SFR), which improves the economic efficiency and reduces the radioactive waste of SFR. In addition, since the happening of the severe accident (SA) at the Fukushima Daiichi Nuclear Power Station, the structural integrity evaluation of SA has been emphasized on SFR as well. As for the practical realization of SFR, it is indispensable to improve materials strength standards such as the extremely high temperature material properties which is required for the application of structural integrity evaluation during the happening of SA.
The material strength standards of SFR are stipulated by the Japan Society of Mechanical Engineers (JSME). However, in order to support the 60-year design, it is necessary to extend the time-dependent allowable value from 300,000 hours to 500,000 hours, as well as to increase the number of the fatigue evaluation cycles to up to 1×10^9 cycles. The Japan Atomic Energy Agency (JAEA) has developed a creep characteristic formula that is excellent for long-term creep evaluation based on the acquired long-term creep data, based on which a revised proposal to extend the evaluation time of material strength standard to 500,000 hours has been proposed. Furthermore, based on the high cycle fatigue data acquired for a maximum of 1×10^9 cycles, a high cycle fatigue evaluation method is under development. In order to evaluate the structural integrity during SA, the extremely high temperature material test data of SUS304 were acquired by JAEA and material strength standards were extended to 1000℃. In the future, to extend the material strength standards to high temperatures, it is scheduled to acquire extremely high temperature data for 316FR steels and Mod.9Cr-1Mo steels which are the main structural materials of SFR.
As described above, in order to make it possible to evaluate the structural integrity during 60-year design and SA, JAEA is working on the sophistication of the material strength standards. Moreover, material strength tests such as high temperature tensile tests, creep tests and fatigue tests are conducted systematically. In this presentation, the overall picture of material testing that we have acquired or plan to acquire in order to establish the JSME standard will be reported.
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|Affiliation/Organization||Japan Atomic Energy Agency|