Studies on thermal expansion and neutron irradiation effect of polycrystalline graphites

For thermal expansion and neutron irradiation effect, thermal expansion coefficients and physical properties were measured of polycrystalline graphites, neutron irradiated, unirradiated, and compressively pre-stressed at room temperature, respectively. Factors involved in the thermal expansion were thus clarified. Relationship between thermal expansion coefficient and dimensional changes of graphites irradiated at high temperatures was studied. Thermal expansion and physical properties were measured of the irradiated graphites and subsequently after their thermal annealing at elevated temperatures. Behavior of the irradiation-induced defects is discussed. (author)