Small Nuclear Reactors for the Production of Nuclear Medicine Radioisotopes and for Co-Generation

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The research project aims at developing two distinct small inherently safe nuclear reactors: the SNB25 district heating and co-generation reactor and the Homogeneous SLOWPOKE reactor.  Both reactors are simulated with the deterministic code WIMS-AECL and the probabilistic (Monte Carlo) code MCNP 5, with the results of both simulations agreeing very well. The SNB25 reactor is based on the TRISO fuel particles with an enrichment of 20% and produces 25 MW of heat by means of water at 95oC that is sent for heating the various buildings of a Canadian Forces base in the Arctic, such as the proposed base at Nanisivik, Nunavut.  This energy can also be supplied to a Rankine cycle-based system to produce electricity with a 16% efficiency.  Previous work has demonstrated the inherent safety characteristics of the concept and the 12-year minimum core life of the reactor, which indeed represents an important asset for applications in areas with harsh weather conditions such as in the Arctic.  The proposed work here aims at improving the computer modelling of the reactor and at designing a more efficient heat transport system and the electricity production system via an improved Rankine cycle.  The other nuclear reactor considered in the proposed project is the Homogeneous SLOWPOKE reactor, based on the successful SLOWPOKE-2 research reactor.  The Homogeneous SLOWPOKE reactor has a double mission: to replace the existing SLOWPOKE-2 research reactors at the end of their core service life and continue their research/teaching mission, and to produce radioisotopes used in several applications including important ones in nuclear medicine.  Like the SLOWPOKE-2 reactor, the Homogeneous reactor produces 20 kW of heat and has been proven as inherently safe in previous work.  The enrichment of the uranium fuel is kept to a maximum of 20% to comply with the Non Proliferation Treaty.  The fuel is an homogeneous aqueous solution of uranyl sulfate (UO2SO4) with a molality determined as 1.46 mol kg-1 for a Zircaloy-2 reactor vessel.  This pool-type nuclear reactor has an operating moderator-coolant temperature of 40oC and simulation work of the reactor in transient states has shown that the worst scenarios result in peak temperatures and power of 83oC and 546 kW, respectively. Further development work proposed for this research project includes replacing the 2-D WIMS-AECL simulation code with a 3-D deterministic software, developing a simulation code accounting for the movement of the fuel within the reactor core (coupling of neutronics and thermal-hydraulics codes), and modelling the behaviour within the reactor core of saturating fission products such as 135Xe .