Pore pressure calculation of the UO2 high burnup structure

UO2 high burnup structure has an important impact on fuel behavior, especially in case of reactivity initiated accident (RIA). Pore relaxation enhances local fuel swelling and puts additional load to the fuel cladding, which makes fuel more susceptible to pellet–cladding mechanical interaction induced failure. Therefore, pore pressure calculation becomes vital when evaluating the fuel failure. In this paper pore pressure is calculated as a function of pellet radial local burnup based on the basic characteristics of HBS using Ronchiʹs correlation. The results indicate that pore pressure will approach a stable value as HBS is developing. A best approximated C value of 55 N/m is recommended for pore pressure calculation.