The graphite sheets has a high melting point and a high high temperature strength, which can be used for a long time near 1000 ° C. This is superior to water and heavy water (water and heavy water can be used as a deceleration material). It has a small absorption probability of hot neutrons, but the deceleration ability of the heat neutron is not as heavy as weigh. Therefore, the nuclear reactor in the graphite plate is a nuclear reactor with a larger body.