Thermal Response of the accelerator-production-or-tritium target under cavity-flooding conditions

摘要

The thermal behavior of the Accelerator Production of Tritium (APT) Facility target during postulated low-frequency loss-of-coolant accidents (LOCAs) is a design and safety concern. In hypothetical low-frequency LOCAs, the cavity would be flooded to provide cooling. This paper investigates the target response when the cavity-flood system (CFS) is activated. Parametric studies are performed to develop design guidelines for the CFS. A code, APTRAD, has been developed to model heat production and heat transfer in the APT target. APTRAD, which uses new features, calculates transient ring temperatures to study the response of the target to various cavity-flood scenarios. The parametric studies evaluated the effect of the (1) initially water-filled rung on the peak temperatures, (2) cavity-flood delay on the peak temperatures. (3) rungs' surface heat flux as a function of time, and (4) reduced decay heat on peak temperatures. When the rung is initially filled with water, without flow, it takes less than 50 s for the water, without flow, it takes less than 50 s for the rung to dry out. The subsequent peak temperature is insensitive to the initial presence of water. The peak temperatures in the rung also are insensitive to the cavity-flood timing. the heat flux and temperatures on the rung exterior surface becomes quasi-steady ～10 min after CFS activation. If the decay heat is reduced below 75%, the peak temperature will be ≤800 °C, which is the threshold value for significant tungsten vaporization.