The Japan Atomic Power Company (日本原子力発電, Nihon Genshiryoku Hatsuden, JAPC) is a company initially formed to jump start the commercial use of nuclear power in Japan, and currently operates two different sites. According to the official web site, JAPC is "the only power company in Japan solely engaged in nuclear energy".JAPC owns both units at the Tōkai Nuclear Power Plant and the Tsuruga Nuclear Power Plant with plans to expand at Tsuruga.The company is jointly owned by Japan's major electric utilities: The Tokyo Electric Power Company (28.23%), Kansai Electric Power (18.54%), Chubu Electric Power (15.12%), Hokuriku Electric Power Company (13.05%), Tohoku Electric Power (6.12%), and Electric Power Development Company (J-Power) (5.37%)..
A sodium-cooled fast reactor (SFR) has been developed as one option for energy de-carbonization in 2050 in Japan. The SFR is operated under a high temperature and a low-pressure condition compared with existing light water reactors (LWRs). The mechanical components and piping in the SFR are consequently designed as thin-walled structures from the perspective of the elevated temperature design. In addition, seismic design earthquake level is to be severe more and more by regulatory requirements based on past earthquake disaster experiences. To secure the seismic safety of the thin-walled mechanical components and piping under a severe design earthquake level, employing a three-dimensional (3D) seismic isolation system has been planned in the SFR. The development results of the 3D isolation system have been reported in previous papers so far. Its update is reported in Part 7 to Part 9. The proposed isolation system consists of a rubber bearing for reducing horizontal seismic load, disc spring units for reducing vertical seismic load, oil dampers for horizontal and vertical damping components, and a support function for assembling each isolation element. Part 7 describes the overview of the R&D, the test plan of the isolation system in the assembled state of each element, and the performance of individual isolation elements. In part 8, the performance of the isolation device that each element was assembled into was investigated through loading tests. Part 9 reports analytical studies by an analysis model validated based on the insight of the test results.
The authors have been developing the three-dimensional isolation system for the Sodium-cooled Fast Reactor (SFR). The three-dimensional isolation device consists of the laminated rubber bearing performing the horizontal isolation function, four-disc spring units, the sliding elements, strength members such as the horizontal support function, and dampers in the horizontal and vertical directions. We carried out the half-scaled assembly static tests under several bi-axial severe conditions from seismic design base loads to significantly exceeding seismic design base loads, as shown in Part 7. The test specimen was assembled elements of which the three-dimensional seismic isolation system is composed, but the horizontal and vertical damping devices were not modeled because of the static loading tests. This paper describes tests results, focusing on the following items. Behavior of smooth operation and ensuring the independency of horizontal isolation and vertical isolation performances Hypothesis and verification of load transfer mechanism under horizontal and vertical loads superposition Effect of reinforcing plates on the loading force reduction of horizontal support function Conditions of the specimen after tests and discussion
