Probabilistic Safety Analysis as Method for Design Assessment of Safety Instrumented Systems of a Cobalt-60 Irradiator (Category IV)

Abstract:

The Department of Nuclear Sciences of Escuela Politécnica Nacional of Ecuador has in its facilities a Cobalt-60 Irradiator. This category IV irradiator has been installed in 1975 and since its beginning, this facility has worked with rigorous protocols of operation, radiologic safety and maintenance. Due to old control systems, the department staff has developed new designs for safety instrumented systems. The design assessment of this one was carried out with the probabilistic safety analysis methodology. The assessment included some safety instrumented systems for determining if the designs developed comply the requirements of radiological safety set by international organizations as the International Energy Atomic Agency and the International Council Radiological Protection. The present study has considered the recharge project of Cobalt-60 irradiator until an activity of 50 000 Ci. Additionally, this study has prioritized the safety instrumented systems related to initial event: the loss wet shielding (water loss in the pool), that can derive in an overexposure of the POE. Further, for the evaluation of the exposition point, one close to the wet shield has been chosen with a hypothetical scenario that a total loss of water ocurred, this situation could happen during a moderate earthquake. Considering the mentioned event, this situation has been assessed by the PSA methodology and obtaining as a result that the annual occurrence probability of an overexposure higher to 2 000 mSv for the POE is 9,91E-8, this result is under the limit established by the International Council Radiological Protection for these events.

Año de publicación:

2022

Keywords:

• Probabilistic Safety Analysis
• Cobalt-60 Irradiator
• Safety Instrumented Systems

Fuente:

scopus