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Neutronic Design and Analysis of a Small Nuclear Reactor to Supply District Heating and Electrical Energy to Canadian Forces Bases Located in the Arctic or the Northern Remote Communities

Stéphane Paquette, Hugues W. Bonin

Nuclear Technology / Volume 176 / Number 3 / December 2011 / Pages 315-336

Technical Paper / Fission Reactors /

The present work describes the preliminary design of a 25-MW(thermal) nuclear reactor capable of providing safe and reliable heating and electricity to any Canadian Forces Bases, especially in the Arctic, as well as in comparable civilian applications. The aim of the project is to provide a nuclear reactor system with sufficient inherent safety characteristics as it is intended to run in automatic mode and be monitored by operators with limited experience and training. For the neutronics calculations, the design work of the reactor's core is carried out using the probabilistic simulation code MCNP 5 along with the Winfrith Improved Multigroup Scheme-Atomic Energy of Canada Limited (WIMS-AECL) deterministic code, Version 3.1, thus permitting a code-to-code comparison of the numerical results. Several design constraints related to coolant temperature and pressure, reactivity control, fuel enrichment, and time between refueling have been considered. The final reactor concept, named the Super Near Boiling 25 reactor (SNB25), provides heat energy dedicated to building and domestic water heating and supplies electricity through an organic Rankine cycle energy conversion plant. SNB25 employs TRISO fuel particles, contained in zirconium-sheathed fuel rods, and is light water cooled and moderated. Complete reactivity control is achieved through simple and reliable mechanical means consisting of 133 control rods and six adjustable radial reflector plates. The optimized reactor core configuration, along with its intrinsic control system, allows for the power plant to operate safely for more than a decade between refuelings from a typical central heating plant or the basement of a multilevel office building. The work also included a preliminary investigation of the nonnuclear part of the energy supply system including heat exchangers and the turbine-driven, electricity-generating system.

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