Loading of a dummy P2M-D rodlet in the PWC device of the BR2 reactor
The Power to Melt and Maneuverability (P2M) project was launched as part of the Second Framework for Irradiation Experiments (FIDES-II), a joint NEA undertaking that enables countries to collaboratively define and finance research in the area of nuclear fuel and materials.
Led by the core group of SCK∙CEN, EDF and the CEA, two power transient tests will be undertaken under the aegis of the P2M. These tests will use double instrumented – fuel inner thermocouple (TC) and LVDT plenum pressure sensor – high burn-up UO2 rodlets at the Belgian Reactor 2 (BR2) operated by SCK∙CEN. The rodlets will be irradiated at high power until obtaining 10-15% of melted fuel volume fraction at the rodlet centerline in order to verify the absence of cladding failure. The other objective of this irradiation programme is to refine the understanding of the mechanisms and phenomena for high burn-up UO2 fuels for high power levels in order to strengthen the safety margins and to facilitate the operation of fuels in power plants.
Before this is done, prior safety qualification tests have had to be conducted in the pressurised water capsule (PWC) on instrumented mock-up (P2M-D) and fuel (P2M-Q1) rodlets at intermediate power during standard BR2 irradiation cycles of around 30 days. The aim is to validate both the irradiation protocol and the leak tightness of the instrumented fuel pin, while verifying the proper functioning of the various instrumentation cables and systems.
The P2M-D irradiation test was completed on 21 September 2025 and will be followed by the irradiation of the P2M-Q1 high burn-up UO2 fuel rodlet. This second test is foreseen to take place in the BR2 by May 2026. The P2M-Q1 instrumented irradiated fuel rodlet was recently remanufactured at the CEA LECA/STAR facility, marking a first time for such an operation since 15 years when rodlets used in the REMORA programme in the OSIRIS reactor were produced.
The P2M-Q1 test will help to complete the P2M safety demonstration at SCK∙CEN, as well as to study fission gas release in a domain where limited data is currently available. Additional furnace tests performed with the MERARGE equipment at the CEA LECA/STAR facility will also allow the study of Fuel Fragmentation in the specific case of P2M-Q1. Two melting tests (P2M-Q2 and P2M-T1) at high power on instrumented high burnup UO2 rodlets will follow at the end of 2026 and beginning of 2028 respectively.
The P2M-D irradiation test marks an important milestone for the P2M project. It demonstrates the ability of the irradiation device and the specific associated instrumentation feedthrough and systems to perform correctly under irradiation.