Tomomi Otani

Development of 2012 Edition of JSME Code for Design and Construction of Fast Reactors: (1) Overview

This paper presents the main features of 2012 Edition of JSME (Japan Society of Mechanical Engineers) Code for Design and Construction of Fast Reactors (JSME FR Code). The first edition of the JSME FR Code was published in 2005 based on the requirements that had been applied to the Japanese Prototype Fast Breeder Reactor Monju. The latest 2012 Edition incorporated 316FR stainless steel and Mod.9Cr-1Mo steel of which application to the Japanese demonstration fast reactors is expected. 316FR is a low-carbon nitrogen added fast reactor grade 316SS which has been developed in Japan. Allowable stresses up to 300,000 hours along with various material properties equations from which they have been derived have been codified. The applicability of the code rules on elevated temperature design to the new materials has been extensively investigated. Focus was on the creep-fatigue interaction evaluation methods, and predictability in long-term regions was carefully demonstrated based on material tests. Various structural tests were also conducted to verify that sufficient margins are maintained for the newly implemented materials. The JSME FR Code will be further upgraded in the 2016 and codes such as fitness-for-service code and leak-before-break evaluation code and a guideline for reliability evaluation of static components will be developed utilizing the System Based Code concept.Copyright

Development of 2012 Edition of JSME Code for Design and Construction of Fast Reactors: (6) Design Margin Assessment for the New Materials to the Rules

New 2012 edition of JSME code for design and construction of fast reactors (FRs code) was published by Japan society of mechanical engineers (JSME). Main topic of the current JSME FRs code 2012 edition is registration of the two new materials, 316FR and Mod.9Cr-1Mo steel. Besides the allowable strength values and material properties were standardized for the registration, the design margins for the new materials to the rules for the components and piping serviced at elevated temperature described in the JSME FRs code were assessed. To confirm the design margins, a series of the assessment program for the new materials to the conventional design rules was performed using the evaluation of the experimental data and finite element analysis. Namely, the design margin including the evaluation procedure of creep-fatigue damage, strain range and the others were assessed based on the background concept of the conventional JSME FRs code. Since a number of the evaluation procedures described in the JSME FRs code were investigated, a several topical assessments of these are reported in this paper. Besides the assessed results of the evaluation of the accumulated creep-fatigue damage and enhanced creep strain are reported, the assessments results of the design margin including the concept of the elastic follow-up originally applied in the JSME FRs code were covered in this paper. Through these assessments, the enough design margins for new materials to the rules were confirmed.Copyright

Environmentally-Friendly HTGR: MHR-50/100—Concept and Characteristics

A business plan and a new concept of the Mitsubishi small-sized High temperature gas-cooled modular Reactors (MHR-50/100) had been developed as reported in a paper at the HTR-2010 conference in Prague. The present paper reports the results of ensuing conceptual design study including updated market researches, improved safety features of the plant, and the plant dynamics analysis. Market researches on Japan, the USA, Southeast Asia and the Middle East have been updated applying the latest energy outlook data. The result shows that the potential market share for the type of HTGR (high temperature gas reactor) reactors is expected to be 10–20% in new construction of heat source plants in those market areas. A financial analysis made based on the results of the updated market research and the plant cost evaluations indicates that the feasibility of an HTGR business potentially exists. Concerning about the conceptual design, as main themes of the study, a plant design, safety design and plant dynamics have been carried out. The MHR-50/100 high safety characteristics have been confirmed based on the results of the following studies as reported in the present paper: (1) An investigation of a safety scenario during occurrence of a Total Black Out event; (2) An analysis of the reactor decay heat removal via a natural circulation. Lastly, the control methods for the reactor and associated steam cycle system for the MHR-50 have been studied. The results show that the reactor power changes can be effectively achieved by controlling the primary system helium flow rate. The ASURA code developed by MHI is used for simulation of such typical plant transients as 10% step load reduction and full load rejection. The results confirm the easy operability and controllability of the plant.Copyright

Measurement of Thermal Ratcheting Strain on the Structures by the Laser Speckle Method

Prevention of thermal ratcheting is an important problem for high temperature components of fast breeder reactors that are subjected to cyclic thermal loads. To clarify ratcheting behaviors, structural model tests were planned. Strain measurement is important for understanding the thermal ratcheting phenomenon The conventional measurement by strain gauge is difficult at high temperature. Then, Laser speckle strain measurement system using the dual-beam set-up was developed to apply to high temperature structural model tests. This system was applied to the thermal ratcheting tests, which demonstrated the actual operative conditions of reactor vessels. Through comparison with uniaxial test results obtained by extensometers, the laser speckle method was verified. Measured data of structural model tests were utilized to certify the guidelines of inelastic analysis for design, which provide prediction method of strain in components of fast reactor.Copyright