Objective: Quantify thermomechanical clad load mechanisms during LWR slow transient
Facilities: BR2 reactor and hot cells (Belgium) and CEA’s LECA/STAR facility (France)
Core Group: SCK.CEN (Belgium), CEA and EDF (France)
P2M includes in-pile tests and Post-Irradiated Examinations in Hot-Laboratory to assess the operational margins at high power. The aim is to generate a deeper understanding of the threshold for incipient fuel centreline melting during slow and long lasting high power transients. The tests will also be used to quantify pellet cladding mechanical interaction (PCMI) resulting from the partial melting. In addition, the fuel thermal fission gas release (FGR) threshold will be confirmed during the stepwise power increase. One of the planned tests will be performed in a manner similar to historic tests in the Halden Reactor Project (HRP). Another test will be conducted with a linear heat rate high enough to enable the study of the effects of the gaseous fuel swelling and the partial centreline fuel melting on the overall fuel rod behaviour.
P2M experimenters are collaborating closely with modelers to maximise the value of each test. A modeling exercise was launched before any testing began. Over 40 modelling experts participated in an exercise using archive data to exercise their codes can be used to assess their ability to predict fuel melting. Through this modelling exercise, a better understanding of the boundaries of existing models has been developed. The exercise also allowed participants to better appreciate specific experimental and examination needs that could improve the modelling of fuel melting behaviour. This “feedback loop” of experiments and simulations was one of the key ambitions of FIDES and this fuel melt prediction exercise was a concrete example of “closing a loop”: improving experimental design, programme planning and research outcomes through an international analysis of calculation results.
Image: BR2 Reactor Diagram / SCK-CEN