Safety analisys of the target design with electron accelerator

An accelerator-driven subcritical facility is being designed using high-fidelity analysis to investigate various target options. Such analysis involves a detailed three-dimensional representation of the geometry. Tungsten and uranium target materials of square cross-section are considered for generating neutrons from the interaction of a 100 kW electron beam of 100 MeV electrons with the target. The target configurations were previously optimized through sequential neutronic, thermal-hydraulic, and structural analyses for a comprehensive assessment of the multi-physics phenomena affecting each design. In the present work, the safety aspects of the design are investigated. In particular two scenarios have been examined in detail. In the first scenario one of the coolant channels is blocked in part or totally, thus increasing the temperature of the target. A thermal hydraulic simulation, performed assuming the same power distribution of the nominal case, was carried out. In the second scenario a loss of flow accident was simulated. In this case the flow is reduced to zero with an appropriate coast-down while the electron beam is being shut down. Full transient sequential neutronic and thermal-hydraulic simulations have been carried out proving that, when buoyancy is considered, the heat can be effectively removed without causing an excessive peak in the maximum target temperature.