Measurement of specific heat on fluorite compounds

Hirooka, Shun ; Matsumoto, Taku; Kato, Masato   ; Tsuchimochi, Ryota; Ogasawara, Masahiro*

Fluorite compounds such as actinide oxide and CaF perform a rapid increase and a peak in the specific heat which are attributed by Bredig transition. The behavior is important as a nuclear fuel; however, the fact that the behavior occurs above 2000C makes the experiment difficult, and the reported data are scattered. In this work, measurement of specific heat was carried out on CaF, SrF and (Ca,Sr)F for the relatively lower melting temperature of below 1500C. (Ca,Sr)F which has lower melting temperature than CaF and SrF showed the rapid increase of specific heat and the peak at lower temperature. It is expected that UO, PuO and MOX that the high temperature data is limited and scattered could show the similar relationship between the specific heat and the melting temperature. Therefore, the results of the measurements on the fluorite compounds suggest the possibility that the Kopp's law is not applicable to the solid solution of fluoride materials at high temperature.