ENEA's activity in the Safety Analysis of the gas cooled eXperimental Accelerator Driven System (XADS)

This document deals with the activity performed by ENEA as contribution to the deliverable 'Transient Accident Analysis of the Gas-Cooled XADS'. It provides the results of the analyses concerning two accidents: Loss of Flow (LOFA) and water ingress in the Primary Coolant System. In spite of an upgrading of the design, required to guarantee the decay heat removal in depressurised conditions, the plant response to an unprotected LOFA remains critical thus emphasizing the need of a beam shutdown system with a very high degree of reliability. Preliminary evaluations on the risk of recriticality due to water ingress in the Primary Coolant System at shutdown conditions shown negative values of the reactivity inserted for all the transients considered. Although conservative and different scenarios have been considered, these analyses have to be revisited once a complete definition of the SCS loop will be available.