Design basis earthquake

Design Basis Earthquake Ventilation system operating, entire target source term released 10 yyr 192 mrem 

While the maximum potential consequences are similar for the process spill and the SCB fire DBAs, the process spill scenario dominates the overall risk to the public by several orders of magnitude as compared to all other DBAs. The maximum potential consequence at the exclusion area boundary (3000 m.) is calculated to be 2 Rem, and the sequence of events that results in this dose is assessed to be extremely unlikely. Accidents that are expected to occur within the lifetime of the facility are (conservatively) calculated to have dose consequences of up to several miliirem at the exclusion area boundary. These DBAs bound ail other potential accidents that have been postulated to occur in the facility. 

This safety analysis has been prepared in accordance with the guidelines of DOE-STD-3009-94, and is presented in the format described in that standard. 

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The coo Ii ng funct ion of this UHS system can be provided by cooling towers or the natural or man-made passive water sources (e.g., reservoirs, rivers or lakes). For the case of cooling towers, the structure should be designed to withstand the effects of natural phenomena including tornadoes, tornado missiles, hurricane winds, floods, and the design basis earthquake. 

AH structures and equipment required to fulfil level FI safety functions shall be seismic category I. Such structures and equipment shall be qualified to withstand the effects of a design basis earthquake (DBF) (i.e. to remain structurally intact, leaktight in the case of fluid retaining equipment, and functionally operable to the extent required by its safety role). 

The design basis earthquake (DBE) for NPH performance category 2 (PC2) systems, structures and components (SSCs) is specified in accordance with DOE-STD-1020-94 as follows ... 

Design Basis Earthquake Natural Phenomena (Earthquake) Various... 

Fire in a radioactive material storage area Design Basis Earthquake... 

The Design Basis Earthquake (DBE) is a natural phenomena event, and is based on DOE-STD-1021. During normal HCF operations, the ventilation system maintains a zone-to-zone pressure hierarchy, which controls the migration of radiological contaminants. The normal flow of air sweeps contaminants that are present in contaminated confinement zones (Zone 1 and 2A) through filters, which are designed to capture and retain the contaminants. In the event of a DBE, many of these systems are expected to fail, and the normal pressure hierarchy would not be maintained. 

Design Basis Earthquake Frequency Bin IV-V, 10" > F 10- (Very Unlikely) 10" > F (Extremely Unlikely) 3.4 to 9 mrem 192 mrem YES... 

An evaluation of the response of the HCF in a Design Basis Earthquake (DBE) has been accomplished in Appendix 3E, and likelihoods of occurrence have been assessed for the configuration of confinement systems and availability of radiological inventory for reiease. 

The SCBs, and the floor, walls, and ceiling of the Zone 2A canyon and Room 109 constitute the structures designed to serve a radioactive material confinement function under all normal, abnormal, and accident conditions (refer to Appendix 3E, Section 3E.7 for design basis earthquake accident analysis assumptions). By reducing the likelihood of a radioactive material release these structures provide both defense in depth and worker safety functions. 

Results of geological surveys of the region surrounding the site, historical information on the occurrence of earthquakes in the region, and palaeoseismic data should be used to derive the SL-2 earthquake for the site, as indicated in IAEA Safety Series No. 50-SG-Sl (Rev. 1). The SL-2 earthquake should be used to establish the design basis earthquake (DBE) for the nuclear power plant. 

The systems, structures and components with the function of shutting down the plant and maintaining it in a long term safe stable state should be designed to withstand the design basis earthquake without a loss of function. 

The design basis earthquake for safety related equipment and structures is based on a load as high as 8 points (MSK-64 scale). 

All the equipment and engineering structures of the NHP are designed for a design basis earthquake with an intensity 8 on the MSK-64 scale. 

Buildings 1054 lOS-L, and lOS-P are passive structures and are therefore always available. Buildings 105-K, 105-1 and 105>P are not susceptible to hi ergetic events sudi as design basis earthquake tornadoes, ox stnu winds. 

The structures of Buildings 105-Is 105P are not susceptible to ilure during design basis earthquakes, tornadoes, and high winds, however, during seismic and shipping cask drop... 

The structure of the K-Reactor Purification Area building is not susceptible to failure during design basis earthquakes, tornadoes, and high winds. The sdsmic event could potentially damage the purification equipment, such as the tanks and lines relea g moderator. In addition, drums of moderator stored outside the Purification Area are susceptible to fireezing during cold weather which also could release moderator. The consequences of a moderator release in the Purification Area are discussed in Section 8.3.2.19 of this BIO. 

It is common practice to have more than one design basis earthquake associated with each hazard level, SL-1 and SL-2, each one representative of a potential seismogenic area. All of these should be considered in the design, and appropriate enveloping should be carried out on the results. 

Regardless of the exposure to seismic hazard, an SI 2 design basis earthquakes should be adopted for every nuclear power plant for the design of safety classified items. The minimum level should correspond to a peak ground acceleration of O.lg (zero period of the design response spectrum), to be considered at the free field. A unified, site compatible spectrum should be associated with this peak ground acceleration value. In this case SL-1 may be assumed to be coincident with SL-2. 

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. 

If the decoupling criteria are not satisfled, a suitable model of the subsystem should be included in the model of the main system. For a subsystem having all its resonant frequencies (with the flexibility of the support taken into account) higher than the amplified frequendes (above 15 Hz for the usual design basis earthquakes), only the mass should be included in the model of the main system. 

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