Recently, “Safety” and “Security” for nuclear technologies are of strong interest worldwide: “Safety” for both nuclear plant and its fuel under normal operating and accident conditions, and “Security” against nuclear proliferation.The high temperature gas cooled reactor (HTGR) is one of small modular reactors (SMRs) to be used for high efficiency wide range of heat applications, which possesses inherent safety features by a physical phenomenon even if all power supplies are lost.The key technology for HTGR’s attractive features is fuel, which consists of tristructural-isotropic (TRISO) coated fuel particle and so-called “carbonaceous” matrix material of compact/pebble-shaped fuel element.On the other hand, this carbonaceous HTGR fuel is easily oxidized under the air-/water-ingress accidents. With regard to safety of the HTGR fuel, geometry of fuel assembly should be kept to prevent from recriticality accident.In addition, from the viewpoint of nuclear security against proliferation, the carbonaceous HTGR fuel could be a weak point because of existing basic technologies on extraction of nuclear material from the conventional HTGR fuel.Recently, silicon carbide (SiC) is focused worldwide on a base matrix material for the advanced HTGR fuel compact to essentially eliminate oxidation-related failure mechanisms during severe accidents, which provide even higher levels of defense-in-depth and inherent safety. Application of SiC for the matrix of HTGR fuel compact is being studied by Japan Atomic Energy Agency in Japan as well as the United States because of its chemical and mechanical stabilities, meeting the requirements on safety against accident and security against proliferation more fully. However, up to date the data on properties of the irradiated SiC-matrix has not been obtained so much.The aim of this project is to investigate irradiation properties of the advanced SiC-matrixed fuel compact strengthening not only its safety feature against air-/water-ingress accidents by SiC’s oxidation-resistance property, but also its security one against nuclear proliferation by both chemical/physical extraction and chemical conversion of nuclear materials.
Studies of properties of the irradiated SiC-matrix of the HTGR fuel element will be carried out in the RK ME Institute of Nuclear Physics, possessing required human resources (researchers and technical specialists experienced in in-reactor material trial), as well as required equipment.Goals of the project are as follows:1. Creation of a device for irradiation of specimens of the HTGR fuel SiC-matrix.2. Irradiation of specimens of the SiC-matrix.
3. Studies of physical-mechanical properties of the both unirradiated and irradiated specimens of the SiC-matrix.The result of this project will contribute significantly to enhancing both safety and security features of the HTGR fuel technology which is unlike any other in the world. The properties of the irradiated SiC-matrix obtained in this project can be applied for developing other small modular type of the fourth the generation nuclear energy system (GEN-IV).
