International Conference on Research Reactors:
Safe Management and Effective Utilization

14-18 November 2011, Rabat, Morocco

The aspects that were considered in the evaluation of the status of the beryllium reflector elements and the justification for the replacement are safety and operational related. The safety considerations were carefully examined against what is stated in the safety requirements document IAEA NR-S-4, and the following safety related functions were deduced as where the beryllium elements are deemed to be a contributor to their fulfillment, the maintenance of a constant core configuration, and the structural integrity of the core. These safety requirements are essential to the fulfillment of the shutdown and cooling safety functions. Furthermore on the topic of safety considerations is the accumulation of the highly radioactive Tritium that may leak through a cracked or broken element and threatens workers and public health. Operational considerations are the reflection efficiency of the elements, the impact on the core performance and on the in-core fuel management, the handling of the embrittled elements, the operational experience, and the replacement criteria by other research reactors. The three former considerations could be realized as related neutronics contributors to the operational performance and the later related to the safety considerations stated above. Against the above background, this paper presents an overview of the Beryllium reflector replacement evaluation with regard to fast neutron impact on ductility, swelling, bowing and subsequent operational difficulties. Lastly the paper highlights safety measures put in place to ensure a well controlled replacement exercise.

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