No
An explosion such as the one that occurred in the n° 4 reactor of the Chernobyl power plant due to a runaway fission reaction cannot happen with the ILL’s reactor. The equivalent scenario for research reactors like ours, known as a BORAX accident, does not produce an explosion capable of damaging all the reactor’s structures, including its containment. The energy stored in the reactor core and released in the “explosion” is much too low to do such damage. Obviously, this is due to the fact that the core of the ILL’s reactor is very small (10 kg of uranium compared with the 190 tonnes contained in the core of Chernobyl's RBMK-type reactor).
The French Nuclear Safety Authority (ASN) requires that the design of experimental reactors such as the ILL’s take into account a so-called “BORAX-type accident” scenario, named after an American research facility that was deliberately destroyed in the 1950s in order to study this phenomenon.
An accident of this type did actually occur at the SL1 reactor in the United States when one of the reactor’s control rods was accidentally and extremely quickly withdrawn from the core. This led to such a rapid exponential increase in the nuclear power generated by the chain reaction that the heat produced in the fuel plates caused them to melt before it could be transferred to the cooling water. The dispersal in the cooling water of a large amount of molten aluminium in the form of very fine droplets then caused the water to vaporise suddenly and explosively. This is known as a “vapour explosion”.
To come back to the ILL’s reactor, the energy released in such a scenario would be less than 200 MJ and would cause the partial destruction of the reactor vessel. The reactor pool and its metal liner have therefore been designed to withstand this “explosion” while remaining leaktight. This phenomenon might also produce a spray of water, but this would not be very powerful and would not therefore damage the reactor containment.
It is important to note that even the most highly unlikely scenario would not create the conditions necessary to trigger a BORAX-type accident at the ILL’s reactor. In fact, this is generally true for the other comparable research reactors in the world. In most other countries, therefore, the safety authorities do not include a BORAX-type accident in the design basis of their reactors.