[en] Analysis on behavior of fission product in the experimental VHTR plant has been carried out to examine intensively the effect of core temperature. In this analysis, the core averaged fission product release fraction of various kinds of fission product is prepared by a newly developed computer code, FPCORE. In this code, core temperature and power distributions can be taken into account using the fission product release data from the coated fuel particle (cfp) and the barrier effect of fuel sleeve at each temperature. Fission product release fractions from the core for different core temperatures are calculated by FPCORE code. The results of analysis indicate that the amount of metallic fission product into the primary circuit increases rapidly at the higher core temperature. This suggests that the retention of metallic fission product in cfp must be investigated for higher core temperature