The last quarter of 2016 included the first power operation tests of the Cabri facility in more than a decade. A long test campaign of power transients (startup tests) will begin in January 2017 to characterize the entire operating domain of the facility. The startup tests verify that this CEA experimental reactor is ready for the first test of IRSN's CABRI International Program (CIP).
The initial power operation tests served to qualify the instrumentation of the Cabri facility by achieving several power levels from 5 to 23 MW and calibrate the neutron chambers used for online measurement of reactor power. In large part they constitute the final phase for requalification of the Cabri facility and complement the qualification tests of the reactor's new pressurized water loop in its nominal conditions (280°C and 155 bar). Analysis of these tests is required to receive authorization to carry out the CIP.
Power operation follow initial criticality of the Cabri reactor, October 20, 2015, in its new, post-renovation configuration. Performed between October 2015 and June 2016, low power tests (< 100 kW) have been used for neutron characterization of the reactor core. From 2003 to 2015, the Cabri reactor underwent an important renovation phase to respond to the requirements of CIP and current safety requirements (earthquake, fire, transport, etc.): seismic reinforcement of buildings and equipment, upgrade for controlling fire risk (measures to limit spread of a fire, etc.), renovation of several systems including reactor core cooling, replacement of nuclear ventilation and I&C, and in particular, replacement of the sodium test loop with the new pressurized water loop which reliably reproduces the pressure (155 bar) and temperature (280°C) conditions of a pressurized water reactor (PWR).
Originally, the Cabri reactor was intended for tests to study reactivity accidents  taken into account in the safety demonstration of certain research reactors. It went critical for the very first time in 1964. In 1977-78 the reactor was reconverted: the core was changed and the facility equipped with a loop reproducing the operating conditions of sodium-cooled fast reactors. From 1978 to 2001, safety tests for the Phénix and Superphénix fast reactors were performed followed by sodium loop studies of reactivity accidents in PWRs (PWR-Na program, 1993-2000). In 2000, after changes in the conditions for using fuel in reactors and to supplement the previous REP-Na program, IRSN launched CIP under the auspices of the OECD. Consisting of tests at the Cabri facility, it will study the behavior of PWR fuel rods during a reactivity accident with the fuel rods in conditions that are identical to those of the reactor. The program includes a total of 12 tests, of which two were already completed on the sodium loop in 2002. The tests will supplement the complete phenomenology of RIAs, particularly in the advanced phase for which the nature of the fluid (water or sodium) affects the physical phenomena that occur, especially the quantity of heat extracted from fuel rods by the cooling fluid. They will also refine the simulations that contribute to safety assessments.
 Reactivity injection accidents, often called reactivity accidents or reactivity-initiated accidents (RIAs), are generally taken into account in the reactor design. For PWRs, they result from the failure of a mechanism controlling a control rod assembly, which helps to regulate the nuclear reaction. Reactivity accidents leads to a rapid, violent generation of energy in the fuel.