All power operated valve actuators that perform a critical safety function in nuclear power plants must be backed by testing to demonstrate they are capable of reliably performing their safety related function. Such actuators are denoted Class 1E and must be qualified according to IEEE-382 “Standard for Qualification of Actuators for Power-Operated Valve Assemblies with Safety-Related Functions for Nuclear Power Plants” which states that a Class 1E Actuator is essential to emergency reactor shutdown, containment isolation, reactor core cooling, and containment and reactor heat removal, or otherwise essential in preventing significant release of radioactive material to the environment. Qualification of these actuators involves type testing where one or several test specimens that adequately represent and span the entire represented fleet undergo rigorous testing commensurate with expected service. Then, for each application, an evaluation is performed to show how specific loading is enveloped with margin by the testing. IEEE-382 is a specific application of the more general IEEE-323 “Standard for Qualifying Class 1E Equipment for Nuclear Power Generation Stations” containing general requirements applicable to all Class 1E equipment; then, the rules of IEEE-323 add useful clarification to those of IEEE-382.
This paper describes actual type testing of a gas-hydraulic actuator where planned levels were not reached at all times for every test due to test apparatus limitations and shows that the resulting intermittently off target test levels need not envelope loading for all times compared to specific applications. IEEE-382 requires an evaluation showing that test conditions meet specific service conditions plus acceptable margin; however, demonstrating that margin also exists in the range of achieved test levels demonstrates that specified service conditions are adequately included even though specified levels are not enveloped at every time or frequency due to the test apparatus limit anomalies. One practical example is given that logically compares the achieved seismic test levels with a sample required load case for a line mounted valve assembly. Another example compares results from a simulated design basis environmental accident event involving high temperature steam with a sample expected event curve. Rather than compare test and application level by level and curve by curve, the physical effect of the loading, such as stress level, is compared between the test specimen and the application. It is concluded that test levels need not envelope requirements at every point if it can be shown and documented that important physical aspects including stress level, deflection magnitude, absorbed vibration cycles, and energy involvement are enveloped with the required margin.