Preliminary study of fuel melt down

Asami, Naoto*; Nishikawa, Masana*

Establishment of the experimental equation of state for nuclear fuel materials at ultra-high temperature and pressure which correspond to hypothetical reactor excursion is a final target of this series of work. The dynamic method for this purpose must be developed since we have no available data for the extreme conditions. In this report, examination for the validity of the dynamic method and there search for the temperature measurement of UO vapor are described as a preliminary study. Considerations for the thermodynamical properties of high temperature states of UO are also made. About 40 Mwatts giant pulse laser is irradiated on the surface of UO sample for the generation of the vapor by intense heating. The vapor ejection pressure is determined from the torsion pendulum and pressure transducer with varying their radiated area. The maximum and minimum values of the pressure are about 1,700 and 20-atm, which correspond to the energy density of 1.110 and 410 joules/cm sec, respectively.