In order to complete current knowledge in the field of reactor core cooling during a loss of coolant accident (LOCA), IRSN launched the eight-year Loss of Coolant Study (PERFROI) project in 2013. Last October, as part of this project, the Institute conducted the first test in the COAL program, in collaboration with Stern Laboratories in Canada.

The PERFROI project studies the thermomechanical and thermohydraulic behaviour of fuel in a LOCA situation. The thermal-hydraulic component is the subject of the new COAL programme (COolability of a fuel Assembly during LOCA) the objective of which is to study the ability to cool the reactor core in an accident situation. Fuel rods that are not cooled during the first phase of the accident undergo a sharp rise in temperature and deformations of their cladding of ballooning type under the effect of their internal pressure. These deformations, which are likely to alter the circulation of water in the reactor core, may compromise the possibility of cooling the core with water from the safety injection systems.

While deformation phenomena have been investigated in the past, the COAL programme aims to study, through tests on different types of deformed and heated rods, the effect of local overpowering due to fuel relocation in the "ballooned" parts. The results of these tests, the first of which took place in October in Canada, will be used to validate the numerical models of the DRACCAR software, developed by IRSN to simulate the behaviour of nuclear fuel during a LOCA.