Plant Damage States

Classification and grouping of accident sequences into plant damage states follows the same basic principles as for the power PSA. The list of plant damage states is more extensive than for the power PSA. 

Typically, the following plant damage states may be considered in SLP PSA  

The status of the containment may be of high importance in defining the plant damage states. For some plants the containment cannot be closed in a short time and any of fuel damages would directly result in an off-site release. Therefore, some SLP PSAs include containment consideration in the definition of the plant damage states. 

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The combinations of failures and non-failed conditions define the state of the pJani at the right branches. The damage associated with these plant damage states are calculated using thermal-hydraulic analyses to determine temperature profiles that are related to critical chemical reactions, explosions and high pressure. These end-states serve as initiators fot breaking confinement that leads to release in the plant and aquatic and atmospheric release outside ol the plant,... 

Estimate the frequencies of various fire-initiated plant damage states. 

Enter failure probabilities (ones) in the system model to determine the plant damage states as a function of water depth... 

Guides 1.3 and 1.4 which were used by the RSS. The RSS presented results of accident progression and fission products in release categories associated with various plant damage states. 

Category 2. Release of liquid ammonia from pipe failure for two plant-damage states involved the assumptions ... 

The SARDB consists ofhundreds ofcalculationresults for significant core damage scenarios by using integrated severe accident analysis codes, for example, MAAP (FAl, 1994) or MELCOR (USNRC, 1990). It includes most of the high frequency accident sequences which are selected from the plant damage state event tree of a level 2 probabilistic safety analysis... 

Severe accident progression starting from the plant damage states, which are the end states of Level-11 PRA... 

The event trees modelled in the Level 1 PRA identify all of the plant event sequences that lead to core damage. Many of the core damage sequences have common characteristics with respect to the reactor system and containment system response. Such sequences can be grouped together into end states (plant damage states) to reduce the number of containment event trees that need to be quantified. The end states form the link between the core damage event tree and the containment event tree. 

The core damage sequences from the Level 1 PRA are grouped together into end states or plant damage states (PDSs) on the basis of similarities in the following characteristics ... 

Table 5.5 -1 summarises the core damage end states that emerge as the dominant ones at the end of plant core damage calculations. The frequency of each plant damage state is calculated by adding the frequencies of all the Level 1 sequences. Each plant damage state is connected to a containment event tree. 

Accident sequence modelUng, including event sequence and system modelling, human performance analysis, dependence analysis and classification of accident sequences into plant damage states ... 

The simplified hybrid method is proposed for evaluation of the seismic safety of existing research reactor facilities or the seismic design review of new ones. This method is especially effective for research reactors, where the success path or the plant damage state cut set can be determined with less effort than for an NPP. 

Equation (20) shows how the individual component fragihties are combined to obtain the plant damage state fragihty parameter using the plant damage state cut set. The above calculations have to be done for at least 10 to 20 acceleration values within the acceleration range of interest. 

A plant damage state is a group of accident sequences that has similar characteristics with respect to accident progression and containment engineered safety feature operability. 

The plant damage states define the important initial and boundary conditions for the Level 2 accident progression and source term analyses. 

Conditional probability of early containment failure for key plant damage states (PWRs) 5.1-28... 

As indicated above, it is not possible to predict with certainty the source term that would result from a given plant damage state. What, then, is the feasibility of on-line monitoring to measure source term characteristics required to project off-site doses ... 

Figure 7 shows the early and latent cancer fatality risk results for the longterm station blackout plant damage state without and with containment flooding. The early fatality risk was decreased when containment flooding was included, but there was only a minimal Impact on the latent cancer fatality risk. 

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