Safety Aspects in Dry Storage of Spent Nuclear Fuel in Long Term Operation for Brazilian Nuclear Power Plants

Abstract

The use of Dry Casks Storage Systems (DCSS) as a strategy for Spent Nuclear Fuel (SNF) management is a solution widely used by several countries. It should be noted that this approach was originally conceived as a temporary / supplementary storage solution, since the ultimate solution is the reprocessing or the storage of SNF in Finals Repositories of radioactive material. Taking into account the limited storage capacity of Angra I and II Spent Fuel Pool, the Nuclear Power Plants Operator has submitted to the Brazilian Nuclear Regulatory Body (CNEN) the design of the Dry Storage Unit (UAS) as an alternative to SNF management. This work performs a Safety Evaluation applying the methodology defined in NUREG 1927 [2]. Three Structures, Systems and Components (SSC), classified as ITS (Important to safety), were selected. Following the methodology, materials and service environments were identified for those SSCs previously selected. In a second moment the ageing mechanisms and degradation effects to be considered in the UAS Long Term Operation were presented. As a result of this Safety Evaluation, some recommendations were extracted. These recommendations together with those found in the literature can guide the regulatory decision-making process regarding to the license renewal of UAS in Brazilian territory.