Pyrotechnic-actuated valves are utilized for various applications requiring remote actuation with high reliability. One such application is passive safety injection (SI) within the emergency core cooling system (ECCS) within the Generation III+ advanced commercial nuclear power plant designs. The pyrotechnic (explosive) actuation within the valve internals, which opens the valve for water flow, creates a vertical force that must be supported by the surrounding piping restraints. This is a well-known phenomenon that is accommodated in the design.
However, there exists also a subsequent, lesser-known axial (horizontal) force that must be accommodated also. A RELAP5/MOD3.3 (patch03) code [1] model for the pyrotechnic valve and the broader injection system was configured to analyze the extent of this water hammer. Typically, the pyrotechnic actuation occurs at relatively low reactor coolant system pressure since the injection itself will eventually be a passive gravity-driven feed. However, even at this low actuation pressure, the RELAP5 analysis demonstrates that the hydrodynamic loads can be substantial. Furthermore, the analysis shows that staggered actuation of a two-valve parallel configuration can exacerbate and magnify the load, compared to a single valve actuation.
