Boiling Water Reactor In-Core Fuel Management through Parallel Simulated Annealing in FORMOSA-B

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Title: Boiling Water Reactor In-Core Fuel Management through Parallel Simulated Annealing in FORMOSA-B
Author: Hays, Ross D
Advisors: Robert White, Committee Member
Paul J. Turinsky, Committee Chair
Edward Davis, Committee Member
Abstract: A commercial nuclear power plant with a boiling water reactor will utilize between 368 and 800+ individual fuel assemblies to generate steam for 18 to 24 months between refueling outages. The composition and reactivity of each fuel assembly will vary due to variations in initial enrichment, burnable poison loading and irradiation conditions in the core. These variations pose a challenge to the engineers who must design subsequent reloads because only one quarter to one half of the fuel will be replaced at a time. One of the challenges is to determine the optimum layout of the fuel within the core in order to get the highest value from the fuel without violating any safety or operational limits. The FORMOSA-B program was developed to automatically find a family of optimum loading patterns by combining a robust, accurate 3-D core simulator with a simulated annealing loading pattern search. Other features have been added to allow the program to rapidly compute shutdown margins and optimize control rod programming through the application of heuristic rules. One drawback of the FORMOSA-B program is that long run-times, sometimes exceeding a week, are required to generate and evaluate the large numbers of solutions required by the simulated annealing algorithm. The rising popularity and availability of parallel computing and computational clusters provides a possible solution to the problem of long run-times. To this end, a parallel simulated annealing capability has been developed for the FORMOSA-B program. The parallel simulated annealing driver utilizes standardized Message Passing Interface routines to divide the individual Markov search chains of the simulated annealing algorithm among a large number of processors. By evaluating multiple loading patterns concurrently, run times are significantly reduced. In testing with a 368-assembly BWR/4 model, parallel speedup factors exceeding 32 were observed with 48 processors. Parallel efficiencies are calculated to be in the range of 68% to 95% when correcting for hardware variations and CRP update frequency. Further testing was performed to investigate the effects on the annealing performance of the Control Rod Programming update frequency, Markov chain length versus parallelization width and solution downselect method.
Date: 2009-04-27
Degree: MS
Discipline: Nuclear Engineering

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