Evaluation method of check-valve integrity during sudden closure using thermal-hydraulic and structural analyses

The Advanced Thermal Reactor (ATR), a boiling-water-cooled, heavy-water-moderated, pressure-tube type reactor, has a series of check-valves just upstream of a water drum that serves as a distributing header for fuel channels. In the case of a hypothetical guillotine break upstream of the water drum, the check-valve integrity is a key issue for reactor safety during rapid closure. Pipe break experiments adjacent to and far from the water drum were conducted to measure the deformation of the valve and the water hammer behavior. Fastest disk impact was observed in the case of an adjacent break and water hammer was observed in the case of a break far from the valve. An evaluation method of valve integrity after the rapid closure to be taken over by the simple method is proposed. In the present study, the thermal-hydraulic analysis is conducted using the HITSL code with a dynamic check-valve model, and structural analysis is conducted by the DYNA3D code. Both behaviors relating thermal-hydraulics and structure are traced by these codes.