Background: Fission product gas accumulation in Tri-structural iso-tropic (TRISO) coated fuel particles can cause the failure of TRISO fuel elements. Purpose: The aim is to study the fission product gases (xenon and krypton) accumulation in UO2 and ThO2 coated particles with respect to various neutron spectra and neutron flux. Methods: Calculations were conducted using ORIGEN code with the neutron databases of THERMAL.LIB

BWRU.LIB

CANDUSEU.LIB and PWRU.LIB as input. Results: It was found that

with the same neutron spectrum

neutron flux and running time

the production of xenon is about 7 times of that of krypton in the UO2 coated particles

and about 4.5 times in the ThO2 coated particles. For the ThO2 coated particles

both xenon and krypton reach saturation earlier when the neutron spectrum are softer

and the saturation values are smaller compared with those in the harder spectrum environment. Conclusion: Taking the fission product gas accumulation as the main factor of TRISO coated particles

the calculation implies that the ThO2 coated particles can have a longer lifetime than the UO2 coated particles under the same neutron environment.Cited