Seismic qualification of equipment for NPPs must demonstrate the ability of a team to perform its safety function during and after the time it is subjected to forces resulting from an SSE. In addition, the equipment must support the effects of several OBE before the application of an SSE.
The safety ratings of electrical equipment and systems that are essential for:
- The reactor emergency Stop.
- The isolation of containment.
- Cooling the reactor core.
- The containment and heat-removal reactor, otherwise they are essential in preventing significant release of radioactive material to the environment.
Earthquake base for operation (OBE)
It is an earthquake that could reasonably produce on the plant site during the plant’s useful life considering regional and local geology, seismology and specific characteristics of local subsoil material.
It is that earthquake that produces the vibratory movement of the earth so that those characteristics of the nuclear energy of the plant, necessary for the continuation without undue risk for the health and the safety of the citizens, are designed to remain functional.
Earthquake safe Stop (SSE)
It is an earthquake based on an assessment of the potential maximum earthquake considering regional and local geology and seismology and specific characteristics of local subsoil material.
It is that earthquake that produces the maximum vibratory earth movement so that certain systems and components are designed to remain functional. These structures, systems and components are necessary for:
- Ensure the integrity of the pressure limits of the reactor coolant.
- The ability to shut down the reactor and keep in a safe shutdown condition.
- The ability to prevent or mitigate the consequences of accidents that may result in exposure beyond the potential comparable to the 10 CFR guideline exposure, part 100.