A Comparison of Reactivity Parameters of CANDU Fuel Bundles over Fuel Lifetime

Authors

  • Michael D Tucker Engineering Pysics, McMaster University

Abstract

Two important parameters for safety analysis of CANDU fuel are the coolant void reactivity (CVR) and the adjuster rod reactivity worth near the fuel. In this study the CVR and adjuster rod worth of two CANDU fuel designs, the standard 37 element natural uranium bundle and the 43 element CANDU Flexible Fuelling (CANFLEX) bundle containing slightly enriched uranium are compared over the useful life of the fuel. Analysis of the neutron multiplication factor of each bundle found that the useful life of the CANFLEX fuel is approximately 32 days longer than the standard CANDU fuel. The plutonium peak, a well-known trait of natural uranium CANDU fuel, was not observed in CANFLEX fuel design. It was found that the presence of a burnable neutron absorber in the centre pin of the CANFLEX fuel reduces CVR by approximately 55%, from about 16.2 mk for the natural uranium fuel to 7.0 mk for CANFLEX before irradiation. The worth of adjuster rods near CANFLEX fuel was found to vary by approximately 5 mk over the life of the fuel. Adjuster rods became more effective as the CANFLEX fuel was irradiated. Standard CANDU fuel exhibits different behaviour. The adjuster rod reactivity becomes less negative for the first 100 days of the fuel cycle before dropping to within 1 mk of the fresh fuel reactivity worth at the end of the useful life.   The standard CANDU fuel bundle is a safer design during normal operating conditions, while the CANFLEX fuel bundle is safer during a loss of coolant accident.

Author Biography

Michael D Tucker, Engineering Pysics, McMaster University

Undergraduate student, engineering physics, McMaster University

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Vol. 1 No. 1 (2017)

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Published

2017-08-22

Issue

Vol. 1 No. 1 (2017): The McMaster Journal of Engineering Physics

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