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Program Description

Tool for Internal Flooding Analysis (TIFA) is designed to utilize generic industry and user-defined information to perform a detailed internal flooding analysis. TIFA allows the user to define critical depths for plant rooms using information from plant drawings or plant walkdowns. This information includes heights of critical components or propagation pathways. TIFA uses these information sources to calculate pipe break frequencies for flood zones, timing for floods to reach critical depths, and flood propagation paths. TIFA then combines these calculation results to develop flood initiating events and corresponding consequential failures and provides them in a format that can be directly entered into CAFTA.

Features

TIFA utilizes a Microsoft® Access® platform in which user-defined, plant-specific information is combined with intenal software to perform a detailed flood evaluation to determine possible flooding rates and identify critical flooding zones (rooms). Plant-specific information entered by the user includes piping and flood zone characteristics, component elevations and sump capacities. The user enters this information into TIFA using a series of windows accessed through a user interface window shown at the top of the next panel. TIFA’s internal software used this information to develop a set of flooding information for each critical zone. This information includes flood rates, flood scenario timing, pipe break frequencies, valve rupture frequencies, potential mitigation of flood events and flood propagation sets.

For each pipe break, TIFA defines the resultant flood accumulation rate in each critical zone by accounting for area volumes, sumps, cutouts and doorways and other factors, such as the fluid pressure and flow restrictions, to estimate a flow into the zone. This process is repeated for breaks in all piping in a zone, and the time to reach one or more critical heights (the level at which one or more components will fail or at which the fluid will leave the zone and propagate to other regions) is calculated.

TIFA then groups the pipe breaks with similar timing to create a timing category and calculates a break frequency for that category. TIFA then collects the calculation results and groups them for each critical zone. This process focuses the analysis on critical zones, while excluding non-critical zones from further analysis.

Using a user-defined propagation matrix, TIFA tracks the propagation to neighboring zones to define additional multizone events and determines the consequential failures of PRA equipment.

A simple human reliability analysis tool is also included in TIFA to address operator mitigation such that both mitigated and non-mitigated events can be presented.

Input and Output

The TIFA’s internal software includes the equation sets needed to calculate pipe flood rates, flood scenario timing, and pipe break or valve rupture frequencies. The plant-specific information may then be input by an analyst through a series of user interface windows. These windows make extensive use of drop boxes to help simplify analyst input and to make the input consistent among the windows.

TIFA output is provided in a format that can be directly entered into CAFTA and is displayed in several tables and windows, some of which are listed below:

• All Flooding Sequences List - provides a detailed description of the retained flooding evaluation sequences. The sequences are defined based on failure of flooding sources, and sequence frequencies are calculated.
• Room Attributes Form - contains subforms that display the following information:
• The “PSA Significant Equipment” subform displays all equipment within the room that has a PRA safety function or impacts a safety-related component.
• The “Flooding Sources” subform contains a list of possible flooding sources for the selected room.
• The “Sump Mitigation” subform describes the water removal ability for the specified room.
• The “Equipment Failure and Flood Propagation” subform describes the room flooding properties, such as the water volume needed to fail equipment and the water volume to cause flood propagation.

Program Description

The Fire Area Target and Component Analysis Tool (FATCAT) is designed to organize and compile the information needed to perform and detailed internal fire analysis. FATCAT can be used stand alone or in combination with ignition source data sheets (ISDS) or general fire event trees (GFET), to develop plant-specific fire initiating events, fire initiation frequencies, fire zone definitions, component matrices and PRA model dependencies.

FATCAT also creates links between rooms (fire zones) in the plant and the basic (failure) event files of the plant's PRA computer analysis code. This is done by associating potentially damaged equipment or cables in a fire zone with their relevant basic events from the PRA model files.

Features

FATCAT utilizes a Microsoft Access platform in which industry and plat-specific fire event information can be used with a screening process to identify critical rooms (fire zones) within a plant and to develop plant-specific fire ignition frequencies and consequential component failures associated with them, which can be input into the plant's PRA code.

FATCAT is designed to accept information from a user-defined industry database. It is also allows the user to build a plant-specific database in which plant fires zones and the equipment in them are defined. Plant-specific information regarding buildings and fire zone locations, equipment location and type, cable types and cable routing information can be input by an analyst through a series of windows that are accessed through the user interface window shown below. This plant-specific database is use for tracing cable routes, and based on available information will extrapolate routes for cables whose routing is not known.

With the above information, the user may focus the analysis by screening from further consideration fire zones with no PRA related equipment or cables.

FATCAT or the ISDSs may be use for to determine fire ignition frequencies and severity factors for the fire zones remaining after the first screening. Having done this, the user can apply a second screen to eliminate fire zones with a fire ignition frequency that is below a selected screening value.

The fire ignition frequencies for the remaining fire zones can be further refined by using an RSC-development GFET. Unsuccessful GFET end states (e.g. fires that are unsuppressed) are combined to produce a fire initiating event frequency. The user may apply a third screen, based on a selected value for initiating event frequency, at this time. Fire initiating events are developed for the fire zones that remain after the third screening, along with the likelihood of fire propagation and a list of consequential failures associated with each fire-initiating event.

Input and Output

During the initial setup of FATCAT, generic (industry) fire information is input by an RSC analyst. As described previously, plant-specific information may be the input by an analyst through a series of user interface windows.

These windows make extensive use of drop boxes to help simplify analyst input and to make the input consistent among the windows

FATCAT output is provided in several tables and windows, some of which are listed below:

Fire Zone Equipment Listing - describes and provides a count of the equipment and equipment types contained in a selected fire zone. This information can be sued to identify potential fire targets associated with a fire in the zone.

Fire Zone Cable Count Listing - contains information about the cables passing through a fire zone and lists the number of zones through which a cable passes. This information is used in verifying cable routing information and in calculating the split fraction contribution of each cable to the fire zone.

Fire Zone Basic Event Listing - provides the PRA model's basic event names for the equipment in a zone and for the cables passing through a fire zone. This information is used to identify consequential equipment failures (throughout the plant) cause by a fire in the fire zone.

FSDS Zone Information Window - displays the information FATCAT provides for a fire zone's ISDS. This includes the equipment and cable counts that are used for calculating the fire ignition frequency for the fire zone.