A Mixed-Integer Linear Programming Method for Optimal Orificing in Breed-and-Burn Cores

Chris Keckler, Alper Atamturk, Massimiliano Fratoni and Ehud Greenspan. A Mixed-Integer Linear Programming Method for Optimal Orificing in Breed-and-Burn Cores. Transactions of the American Nuclear Society, Vol. 118, 887-890, 2018. https://atamturk.ieor.berkeley.edu/pubs/orificing.pdf.

In the design of nuclear reactors, it is important to ensure that each fuel assembly can be adequately cooled so that fuel melting does not occur. The assemblies are cooled by flowing coolant around and through the assemblies during normal operations. The amount of coolant that flows through each assembly can be controlled through the use of assembly orificing, where a specified pressure drop is induced by placing an “orifice” at the inlet of each assembly. To reduce manufacturing complexity, it is desirable to have as few unique orifices as possible (i.e. many assemblies have the same orifice, and therefore the same coolant flowrate). However, the orificing scheme must be designed so that each assembly can be adequately cooled during the course of operation, even though the power of each assembly varies throughout its lifetime. Additionally, the orificing must account for a number of engineering and safety constraints. Standard reactors are able to achieve these goals using typically only a handful of orifice groups (5-10). Furthermore, the orificing scheme can typically be determined through simple trial-and-error. However, a specific class of reactors called breed-and-burn reactors present a much larger challenge for the orifice designer. This paper explores the use of mathematical programming to determine a suitable orificing scheme which adheres to the outlined engineering constraints while simultaneously minimizing the number of orifice groups required.