Ghent University’s Thetis nuclear reactor was used for scientific research until 2003. After a lengthy preparation period, the reactor has now been officially dismantled. This means that there are no longer any radioactive substances or materials in the building. The declassification of a nuclear reactor, a first in Belgium, is the result of an outstanding partnership between Ghent University and SCK•CEN.
The Thetis research reactor of Ghent University was in operation since 1967. It was a test reactor, which was deployed solely for scientific experiments, not for generating energy. ‘Our work group has used this unique nuclear reactor as a neutron source used to carry out radiation research for other research centres and for our own research, especially neutron activation analysis,’ says Karel Strijckmans, chairman of the Analytical Chemistry professional group and the final operator of the nuclear reactor.
Thetis was finally shut down on 17 December 2003. After that, the necessary measures were taken to put the reactor in safety mode pending fuel unloading and dismantling.
Dismantling – outstanding expertise in Belgium
To manage the dismantling of Thetis, Ghent University called upon the services of SCK•CEN, which has built up a wealth of unique knowledge through the dismantling of its BR3 reactor. ‘In 1989, BR3 was selected as a European pilot project to study the technical and economic feasibility of reactor dismantling; our pressurised water reactor was a test case for the development of the Belgian legislation,’ says Luc Noynaert, head of the Dismantling, Decontamination and Waste department at SCK•CEN. ‘Thetis is a different type of reactor than BR3 and easier to dismantle, but the methodology and approach are the same. The experience with Thetis has been an essential learning experience for our other dismantling projects and for the further development of this unique Belgian expertise.’
History of the discharge and dismantling
In 2010, Transnubel carried out the unloading and evacuation of all nuclear fuel. What was left behind was the strongly activated structure in the reactor vessel and the infrastructure which was necessary, among other things, for cooling and ventilation. Some parts might also be slightly radioactive. These parts were dismantled by Belgoprocess (in collaboration with Mourik) between 2013 and 2015. Everything was dismounted and, after a very thorough check for radioactivity by the Health Physics department from Ghent University, was safely evacuated. Finally, the same department has scanned the entire reactor building to trace any residual radioactivity and, if necessary, safely remove it.
In the meantime, there are no longer any radioactive substances in the reactor building. The building, apart from the bottom of the reactor pit, has been released. After extensive inspections, the International Atomic Energy Agency (IAEA), Euratom, and the Federal Agency for Nuclear Control (FANC) officially declared the nuclear reactor dismantled in 2015. The conclusion of that decision-making process was the publication of a Royal Decree (14 December 2015) for the prorogation of the licence for the reactor.