5 - Key technologies for future sodium-cooled fast reactors

Abstract

This chapter describes the latest results and future prospects of the research and development activities in ten key technologies for the future sodium-cooled fast reactors (SFRs).1.Safety: Safety is the top priority for SFR development and design. In this section, research and development on the critical safety issues specific to SFRs are discussed, including safety design criteria and safety design guidelines (SDC/SDG), self-actuated shutdown system (SASS), severe accident, sodium combustion, sodium-water reaction, and source term.2.Sodium component development: Conceptual designing of Japan Sodium-cooled Fast Reactor (JSFR) has been conducted since 2006 and several innovative sodium component designs were established. The development plan for JSFR includes large-scale sodium component experiments and system demonstrations.3.Reactor core physics: JAEA has been developing a standard reactor core physics analysis method for fast reactors for many years. This analysis method was developed on the premise that integral experimental data are reflected in the core design using a kind of data assimilation methodology. This section outlines the features of this analysis method, including not only the analytical models and computer codes but also the experimental database.4.Fuel and materials: This section introduces the results of physical properties study, irradiation behavior evaluation and performance code development of MOX fuel, and long-life core material development such as ODS steel cladding that has been implemented in Japan for practically realizing fast reactors.5.Thermal-hydraulics: Various thermal-hydraulics phenomena should be evaluated accurately to ensure the safe and reliable operation of an SFR plant, mainly by computational fluid dynamics (CFD). These include plant dynamics, natural circulation, thermal-hydraulics in fuel assemblies, and the hot plenum of a reactor vessel.6.High-temperature structural materials and structural design: Elevated temperature design methods considering time-dependent deformation and failure by creep phenomena are required for design and construction of the SFRs operated at high temperatures. This section introduces the development and codification of the Japanese unique elevated temperature design codes.7.Seismic design: This section introduces some typical research activities related to the seismic design of SFRs. Establishing the seismic design technology of structures and mechanical components is a critical challenge in realizing SFRs in Japan that has many experiences of the severe earthquake disaster.8.Operation and maintenance: This section describes the fitness-for-service code and LBB assessment guidelines for sodium-cooled fast reactors that have been newly developed by the Japan Society of Mechanical Engineers. In addition, the development of an under-sodium viewer that is a unique technology for inspections in the opaque coolant is explained.9.Fuel cycle-related studies: JAEA has promoted the development of simplified pelletizing fuel fabrication and advanced aqueous reprocessing methods to establish the fuel cycle technology for fast reactors through the Fast Reactor Cycle Technology (FaCT) development project. In this section, the summary of the developments described before is introduced as the main issues in the fuel cycle-related studies.10.ARKADIA–Advanced reactor knowledge- and AI-aided design integration approach through the whole plant life cycle: JAEA has started to develop “Advanced Reactor Knowledge- and AI-aided Design Integration Approach through the whole plant life cycle (ARKADIA)” as one of the research and development infrastructures. ARKADIA offers the best possible solutions for any challenges that could arise in the plant life cycle, including plant design and safety measures, maintenance, and decommissioning.