Reactor power transients
Tiret rouge


A research reactor for studying fuel and its cladding in accident conditions.​​​​​

CABRI is a pool-type research reactor currently operated under the Cabri International Programme (CIP) and managed by IRSN under the OECD. This programme includes various tests designed to study the behaviour of fuel rods and their cladding in the event of a reactivity insertion accident following control rod ejection in a pressurised water reactor (PWR). With a maximum power of 25 MW under steady-state conditions, the CABRI driver core comprises 1487 stainless steel clad UO2 fuel rods enriched by 6%. The pressurised water loop is installed in an experimental cell positioned in the centre of this core. It also houses the device containing the test rod subjected to a power transient of up to 20 GW in a few milliseconds. The reactivity injection is provoked by the rapid depressurisation of tubes (called transient rods) filled with helium-3, a neutron-absorbing gas.
In order to carry out these studies, our teams and those of IRSN have equipped the research reactor with instrumentation to measure all the relevant parameters, such as the flow rate, pressure, temperature, etc. The hodoscope, comprising 306 fast neutron-counting channels, provides a power profile of the test rod in real time. This allows us to measure any elongation in the rod and to detect any fuel relocation. The condition of the rod before and after the power peak is characterised by gamma spectrometry and X-ray tomography using the IRIS bench. The rod is then sent to LECA for destructive testing.

​Activités. © IRESNE/CEA​​


  • Operation of the research reactor and implementation of experiments,
  • PWRs,
  • Nuclear fuel and cladding,
  • Reactivity insertions,
  • Instrumentation and measurements.
​Equipements majeurs. © IRESNE/CEA

Major equipment

  • CABRI research reactor,
  • Instrumentation,
  • Pressurised water loop,
  • Transient rods,
  • Hodoscope.
​​Chiffres clés. © IRESNE/CEA​​

​Key figures

  • 40 people working in the CABRI licensed nuclear facility, including 2 doctoral students,
  • 6 experimental programmes since 1978: 3 on fast reactors (59 tests) 3 on pressurised water reactors (15 tests, with the CABRI International Programme (CIP) currently underway).
​​Partenaires. © IRESNE/CEA​​


  • IRSN,
  • CIP consortium.