CFD analysis of the safety related thermal hydraulic parameters describing a flow domain of an experimental medical installation (BNCT converter) inside of the Research Reactor MARIA

The Boron-Neutron Capture Therapy (BNCT) is an experimental radiotherapy technique used to treat the most aggressive types of brain tumors that cannot be surgically removed from the human body. To date, clinical trials of BNCT have been initiated at only a handful of reactors around the world, but advanced studies on BNCT are still being carried out in numerous research centers where the suitable or convertible reactors are available. Construction of BNCT facilities is justified only at some existing reactors. Others can possibly be adapted for BNCT by using fission converters to modify the energy spectrum of the primary neutron beam, which makes it useful for treatment purposes. The BNCT converter, designed for use in the MARIA research reactor at the National Centre for Nuclear Research [W1] (NCBJ) in Świerk near Warsaw, Poland, consists of 99 fuel rods (containing low-enriched uranium) inside of the aluminum box. Since its installation affects the core layout and possibly may affect the normal operating regime of the reactor, additional safety analyses must be performed to prove the existence of sufficient safety margins. In this study modern Computational Fluid Dynamics (CFD) techniques have been applied to assess the maximum temperature of the rod wall surfaces, the temperature difference between the inlet and outlet of the converter channel, as well as the maximum and average velocity of the fluid and to compare them with the results presented in the reference analytical study.