ESS Target Station Ventilation - Managing Radiation Hazards

The ESS spallation target undergoes to a scheduled irradiation period of 5 years. After this time, the Target assembly (wheel and shaft) is transported to ESS Active Cell where a series of mechanical operations are foreseen in order to dismantle the target and sort the wastes before their disposal. The nature of the dismantling operations - mainly performed with sawing and shear cutting tools - generates activated aerodispersed particles (aerosols and gas) contributing to high contamination levels inside the Active Cell. The function of the HVAC is to ensure the dynamic confinement of the airborne contamination and to collect it, through filtration system, to a specific point before the release. In this paper, the study of the HVAC system is focused on the fire event case. This situation, among others involving the Active Cell, can jeopardize the dynamic confinement hence creating the potential for a radiation hazard for workers and public. With reference data coming from existing literature, the study shows that a controlled operational mode of the HVAC ensures, at the same time, the protection against the fire spread and the dynamic confinement of the airborne contamination for the entire duration of the postulated fire.