Safe shutdown earthquake

Safe shutdown earthquake (SSE) test This is defined by the most severe earthquake that could occur, producing the maximum vibratory ground movements at the place of installation. Safety-related machines, devices and components should remain functional during an earthquake of this magnitude and maintain the safety and integrity of the plant until a safe... 

In estimating the fragility parameters, it is convenient to work in terms of an intermediate random variable known as the factor of safety F. This is defined as the ratio of the grouiiti-aeederation capacity A to the safe shutdown earthquake (SSE) acceleration used in plant tlesign. 

A seismic event three times or more the 0.25 g safe shutdown earthquake was the only significant mechanism found to cause oxidation of the graphite moderator stack. 

The Safe Shutdown Earthquake (SSE) maximvun horizontal and vertical ground acceleration is less than or equal to 0.3g... 

The simultaneous occurrence of pipe break and either safe shutdown earthquake (SSE) or operating basis earthquake (QBE) as in Section 2.6, is considered too improbable to be incorporated in the plant design basis. This is reflected in the loading combinations for structures in Section 3.8. It is expected that the probabilistic risk assessment (PRA) will confirm the above, and additional revisions to load factors and load combinations may be made if they are supported by the results of probabilistic analyses. (Ref. 1) The current design is based on the following ... 

Seismic loads (E and Egg) are from the operating basis earthquake (QBE) and the safe shutdown earthquake (SSE), respectively. These seismic loads are inertial forces corresponding to maximum accelerations at floor elevations given for a range of site conditions. Seismic loads are determined based on analysis as described in Section 3.7. 

Regulatory Guide 1.165 (1997). Identification and characterization of seismic sources and determination of safe shutdown earthquake ground motion. Published by U.S. Nuclear Regulatory Commission. 

B. The flywheels will be designed to withstand normal operating conditions, anticipated transients, and the largest mechanistic pipe break size remaining after application of leak before break as described in Section 3.6, combined with the Safe Shutdown Earthquake. 

The criteria applied in the design of the Reactor Coolant System supports are that the specific function of the supported equipment be achieved during all normal, earthquake, safety valve actuation and Branch Line Pipe Break (BLPB) conditions. (BLPB includes feedwater line breaks and all loss-of-coolant-accident conditions resulting from breaks not eliminated by leak-before-break analysis in piping to branch nozzles of the reactor coolant system.) Specifically, the supports are designed to support and restrain the Reactor Coolant System components under the combined Safe Shutdown Earthquake and Branch Line Pipe Break loadings in accordance with the stress and deflection limits of Section III, ASME Code. 

The safety-related portions of the building complex, the reactor building with the reactor containment, the adjacent diesel buildings, and the control building, are designed to withstand the effects of earthquakes the standard nuclear island is designed to sustain a "safe shutdown earthquake" of 0,25 g. 

Various safety related systems and safety support systems are designed to appropriate safety class specifications depending on the functional importance. In addition, systems are seismically designed for two different intensities of earthquake. The operating basis earthquake (ODE) represents the intensity of earthquake for which the systems are designed to remain functional during and after the event. The safe shutdown earthquake (SSE) considers the maximum earthquake potential of the site and only those systems which are required to ... 

The system is totally independent from the main feed water system and is capable of supplying feed water at the rated pressure to the steam generator for decay heat removal. The auxiliary feed water system is designed to be operable under safe shutdown earthquake condition. 

Generic Safety Issue (GSI) 119.3 in NUREG-0933 (Reference 1), addresses the question of assuring the public safety during seismic events in a more rational manner by eliminating the requirement to relate the Operating Basis Earthquake (OBE) to the magnitude of the Safe Shutdown Earthquake (SSE). 

Leak-Before-Break methodology, are accounted for in the faulted condition analysis by applying a conservative factor to the safe-shutdown-earthquake resultant loads. 

Static and seismic loads are transmitted by bolts to floor embedments and/or to the k>o1 walls by horizontal compressive beams. During a safe shutdown, earthquake (SSE),. stored fuel integrity is maintained following im SSE, fuel is removable. Following a SSE, stored fuel is reusable. 

Beyond DBA (BDBA) and severe accidents can result from one of fhe initiating events as in case of DBA however combination of failure of ECCS system and emergency systems can lead to these events. Such accidents include those initiated by events, such as RPV rupture or a seismic event more severe than the safe shutdown earthquakes, that... 

This level corresponds to an earthquake level often denoted as a safe shutdown earthquake. The term design basis earthquake is sometimes used to refer to a standard or unified safe shutdown earthquake that is site independent. 

Various structures, systems and equipment of the CHTR would be designed for high level and low probability seismic events such as an operating basis earthquake (OBE) and a safe shutdown earthquake (SSE). Seismic instrumentation is also foreseen. 

The Class IE 125 VDC batteries of each redundant train are located in separate, seismic Category 1 rooms. In addition to providing protection against the safe shutdown earthquake, the walls of these rooms act as fire barriers to maintain the integrity of the redundant systems. Electrical separation is also maintained to ensure that a single failure in one train does not cause failure in the redundant train. 

The Temelin NPP had an original seismic design basis value 0.06 g. In order to follow IAEA recommendation 1, the recommendation of the IAEA expert mission to Temelin in 1992, and the IAEA Safety Guides 50-SG-Sl and 50-SG-D15, the safe shutdown earthquake (SL2) and operational basis earthquake (SLI) values have been re-evaluated as follows ... 

Safe Shutdown Earthquake 0.30g peak ground acceleration... 

The contaimnent, auxihary building, refuelling pool, and spent fuel pool are designed to seismic Category I requirements to thus provide their integrity in the event of a safe shutdown earthquake. 

It is important to reactor protection that the reactor coolant continues to flow for a time after reactor trip and loss of electrical power. To provide this flow, each reactor coolant pump has a high-density flywheel and high-inertia rotor. The rotating inertia of the pump, motor, and flywheel is used during the coastdown period to continue the reactor coolant flow. The reactor coolant pump is designed for the safe shutdown earthquake. The coastdown capability of the pump is maintained even for the case of loss of offsite and onsite electrical power coincident with the safe shutdown earthquake. Core flow transients and figures are provided in Sections 15.3.1 and 15. 3.2 of Reference 6.1. 

The minimum acceptable acceleration for the OBE will be taken at least one-half of the Safe Shutdown Earthquake (SSE) acceleration. Sometimes OBE < SSE have been permitted in some cases where SSE return period is such duration as not to be reasonably expected during the life of the nuclear power plant. If the vibratory ground acceleration of the site is equal to or greater tha n OBE acceleration, the US Federal Regulation makes it mandatory to shut the nuclear power plant for inspection. 

These loads include extreme environmental conditions, such as tornadoes and the safe shutdown earthquake postulated to oeeur during the life of the faeility. Also included are effeets resulting from a postulated rupture of a high-energy system during normal operation, startup or shutdown of the plant or other postulated design basis aeeident. 

E= safe shutdown earthquake resulting from horizontal rock acceleration of 0.18 g (0.18 g vertical). 

TENNESSEE VALLEY AUTHORITY 07107173 BNP PRIMARY CONTAINMENT STRUCTURE TRANS. + TORSIONAL RESPONSE GROUND ACCELERATION = 0.18 G SAFE SHUTDOWN EARTHQUAKE SPECTRAL EARTHQUAKE RESPONSE 5.0 PERCENT DAMPING HORIZONTAL BENDING MOMENT... 

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