First test using CABRI pressurised water loop

18 April 2018

The first test simulating an accident situation in a pressurised water reactor has been successfully completed at the CABRI research reactor in Cadarache, southern France. The test was part of an international research programme aimed at improving knowledge of nuclear fuel behaviour during an accident involving a sudden increase of power.

CABRI - 460 (GCC Groupe)
The CABRI reactor at Cadarache (Image: GCC Groupe)

The CABRI pool-type research reactor is operated by France's Alternative Energies and Atomic Energy Commission on behalf of the Institute for Radiological Protection and Nuclear Safety (IRSN). The reactor was built in 1962 and has since been adapted for the purpose of safety studies on French nuclear facilities, from fast neutron reactors to recent pressurised water reactors (PWRs). It has undergone a major renovation programme in order to comply with current safety standards and to install an experimental sodium loop with a pressurised water loop.

The CABRI reactor features a rod system in its core, which uses an ultra-rapid depressurisation phenomenon to change the reactor power from 0.1 MW to 20,000 MW in just a few milliseconds, for a very short duration of 10-100 milliseconds. The test device containing the fuel rod under examination is equipped with a range of instrumentation making it possible to measure the main experimental parameters. The water loop is equipped with a gamma spectrometry unit used to characterise fission product releases in case of cladding failure. The reactor is fitted with a specific device called a hodoscope designed to measure fuel movement during the power transient.

Launched in 2000, the CABRI International Programme (CIP) aims to study the behaviour of nuclear fuel rods and their cladding during accident conditions in PWRs. Such an accident would result in a rapid, sudden and local increase in the neutron flux, which would induce an increase in nuclear power due to fission. The programme is led by IRSN and sponsored by the OECD Nuclear Energy Agency in collaboration with partners from the Czech Republic, Finland, France, Germany, Japan, Slovakia, South Korea, Spain, Sweden, Switzerland, the UK and the USA.

The CIP comprises 12 tests. The first two were performed in 2002 when the CABRI reactor was still cooled by a sodium loop.

On 16 April, the first test using the pressurised water loop was successfully conducted. The purpose of the test was to ensure that the new loop works properly, study the heat exchange between the coolant and rod cladding, along with the thermal interaction between the ejected fuel fragments and water in the event of cladding rupture.

IRSN Director General Jean-Christophe Niel said, "The next step in the programme hinges on testing the irradiated fuel rods in an environment as close as possible to that of a pressurised water reactor core." The CABRI water loop operates at a temperature of around 280°C, a pressure of 155 bar and a flow rate of up to 6 cubic meters per hour. "These conditions have never before been created in this kind of experiment." Niel noted. "The aim is to obtain the knowledge required to assess the safety of PWR reactors."

Researched and written
by World Nuclear News