Our laboratory envisions carbon-neutral society that makes maximum use of variable renewable energy, and has been engaged in basic research on mutli-functional small/micro nuclear reactors that work together with solar and wind powers. In order to achieve an energy mix that balances electricity supply and demand while achieving carbon neutrarity, nuclear reactors will need to play a new role as load-following power sources in addition to their traditional role as base-load power sources. Since nuclear reactors have unique reactivity feedback characteristics, we have been studying passive autonomous load following methodology for nuclear reactors that take advantage of the inherent characteristic by comparing it with active load following methodology.

Keywords

Reactor kinetics and thermal-hydraurics, Load following, Cogeneration, Small modular reactors, Micro reactors, Simulator, Visualization

Examples of Research Themes

1. Study on multi-functional small/micro nuclear reactors that work together with variable renewable energy.

2. Development of analysis code/simulator for load-following operation of small nuclear reactors using simplified reactor model.

Publications

researchmap, Researchgate, Scopus

Removal of fuel debris, a mixture of molten nuclear fuel and structural materials that has cooled and re-solidified, from the damaged reactor containment vessel is planned at Fukushima Daiichi Nuclear Power Station (1F). This work is one of major processes in the 1F decommissioning. Since the fuel debris is essentially different from normal nuclear fuel in composition, shape, and spacial distribution, it is important to prepare for the unlikely recriticality event in addition to ensuring that the removal work is carried out in a subcritical state. 

Our laboratory has been developing a criticality impact analysis methodology specialized for fuel debris many-particle systems as a fundamental technology necessary for establishing measures to ensure the safety of fuel debris removal workers, within the framework of a collaborative research project with Japanese nuclear industry.

Keywords

Criticality safety analysis, Space-dependent kinetics, MIK2.0, MVP, Serpent, Statistical geometry model (STGM), Monte Carlo neutron transport calculation, High performance computing, Fuel debris, Decomissioning

Examples of Research Themes

1. Development of a space-dependent kinetic analysis code Multi-region Integral Kinetic ver. 2.0 (MIK2.0) (MEXT/JAEA-CLADS Project 2019-2023) 

2. Criticality impact analysis of fuel debris removal work by the weak coupling of MIK2.0 code and MPS method on high performance computing platform. (NDF, Science Tokyo, TCU, NAIS, CRIEPI, 2024-)

Publications

researchmap, Researchgate, Scopus

As a way to utilize radioactive waste to benefit society, we have been focusing on batteries that convert radiation energy into electricity. These batteries are mainly classified into two types depending on the energy conversion method:

1. Thermoelectric Conversion

・Radioisotope Thermoelectric Generator (RTG)

2. Direct Energy Conversion

・β/γ volatics using semiconductor with/without scintillator (Same principle as solar cells)

・Direct Charge Nuclear Battery (DCNB)

One of our research focuses is on DCNB, which are expected to have higher conversion efficiency than RTG and β/γ voltaics, and has been studying the their application to long-life, low-power batteries for infrastructure devices used in underground and deep sea.

Keywords

Nuclear battery, RTG, Beta/Gamma voltaics, Direct charge nuclear battery, Direct energy conversion, Monte Carlo paricle transport calculation, PHITS, EGS, Radioactive waste

Examples of Research Themes

1. Development of DCNB for long-life and low-power battery (JSPS Grant-in-Aid for Scientific Research (C) 2025-2028)

2. Study on conversion efficiency of various batteries using radioisotopes

Publications

researchmap, Researchgate, Scopus