France's Cabri research reactor at Cadarache has once again achieved criticality after several years of renovation and upgrading as part of the Cabri International Programme (CIP) for the study of reactivity accidents with high burn-up fuel assemblies in pressurised water reactors (PWRs).
CIP is led by France's Institute for Radiological Protection and Nuclear Safety (IRSN) under the aegis of the OECD Nuclear Energy Agency (NEA) and is coordinated and co-funded by 18 partners from 12 countries.
IRSN said the objective of CIP, originally launched in 2000, is to study the behaviour of nuclear fuel rods and their cladding during a reactivity injection accident (RIA) in pressurised water reactors. Such an accident would result in a rapid, sudden and local increase in the neutron flux, which would induce a sharp power peak due to nuclear fission.
The CIP programme comprises 12 tests in total. The first two reactivity injection tests on irradiated rods were carried out in the Cabri research reactor equipped with a "sodium loop" representings the primary circuit in which the reactor coolant circulates. These two tests made it possible to study phenomena that do not depend on the nature of this coolant. However, to study conditions representative of an accident in PWRs, the "sodium loop" had to be replaced by a pressurised water loop.
NEA said CIP aims to extend the database for high burn-up fuel behaviour and, importantly, perform the majority of tests in conditions representative of light-water RIAs.