Simon Vanmaercke's PhD Thesis

The ability to shut down the nuclear chain reaction is of course one of the most important safety features of any nuclear reactor. One common way of shutting down the reactor is by inserting a neutron absorbing rod into the reactor core. This rod will absorb a part of the neutrons in the reactor and stop the chain reaction. However in some, very unlikely, accidents it is possible that these rods cannot be inserted into the reactor, for instance due to deformation of the core.
The purpose of this PhD was developing an additional safety system, complementing the system based on the control rods that can also work in a liquid metal coolant. As a first step, a concept using spherical absorber particles and a metal melt seal was proposed. During normal operation the absorbing particles are kept above the core by means of an Aluminum melt seal. When something goes wrong, the temperatures in the reactor will increase till the Aluminum seal will melt. When the Aluminum seal is molten, the neutron absorbing particles are no longer supported and fall down into the active core region. In this way they will shut down the reactor.
As a next step, this concept was evaluated both through experiments as well as Discrete Element Method (DEM) and Smoothed Particle Hydrodynamics (SPH) particle-based simulations.
As will be demonstrated during my public defense, both the particle flow as well as the Aluminum seal showed unexpected results which I would be happy to share with you the 27th of February 2012.

Jury:
Pr. Yann BARTOSIEWICZ, Promoteur (UCL)
Pr. William D’HAESELEER, Promoteur (KULeuven, Belgique)
Pr. Grégoire WINCKELMANS, Président (UCL)
Pr. Michel GIOT, Secrétaire (UCL)
Pr. Hamid AIT ABDERRAHIM (UCL)
Dr. Engelbert TIJSKENS (KULeuven, Belgique)
Dr. Gert VAN DEN EYNDE (SCK.CEN, Belgique)
Dr. Werner MASCHEK (KIT, Allemagne)