For the realization of a practical high temperature gas-cooled reactor (HTGR), the fuel for the practical HTGR is essential. The required burnup of the fuel of a practical HTGR is about 100 GWd/t. The maximum burnup of the High Temperature Engineering Test Reactor (HTTR) fuel is about 33 GWd/t. Then the required burnup of a practical HTGR fuel is about three times as large as that of the HTTR.
The coated fuel particles (CFPs) are used in HTGRs. Fissile materials and fission products (FPs) are confined in each CFP. The gaseous FPs causes the internal pressure of the CFP, and finally burst the CFP. The increase of the burnup causes the increase of the generation of the gaseous FPs. This is one of the problems for realization of a practical HTGR.
Japan Atomic Energy Agency (JAEA) has developed the technology for design of the dimensions of the CFP (thickness of each coating layer and diameter of fuel kernel) for high burnup. Based on this technology, JAEA and a fuel maker have jointly carried out the development of the technology for the fabrication of the new CFP. The demonstration of the integrity of the fabricated new CFPs by irradiation test is essential. Then JAEA carried out the irradiation test of the new CFP in a foreign reactor, and is carrying out the post irradiation tests through an international collaboration.
- Reference
- S. Ueta, et al., Research and Development on High Burnup HTGR Fuels in JAEA, Proceedings of ICONE27 (2018).
- S. Ueta, et al., Development on extended burnup fuel technologies for practical high temperature gas-cooled reactors; Collaborative research with Kazakhstan, 2019 fall meeting of Atomic Energy Society of Japan, 2K11.