ML18213A080
| ML18213A080 | |
| Person / Time | |
|---|---|
| Issue date: | 07/31/2018 |
| From: | Tammie Rivera NRC/RES/DRA/FRB, Electric Power Research Institute |
| To: | |
| Shared Package | |
| ML18213A072 | List: |
| References | |
| Download: ML18213A080 (25) | |
Text
Joint EPRI/NRC
-RES Fire PRA WorkshopAugust 6-10, 2018Module III
-Fire AnalysisTask 1 -Plant PartitioningA Collaboration of the Electric Power Research Institute (EPRI) & U.S. NRC Office of Nuclear Regulatory Research (RES) 2Plant Partitioning Scope (per 6850/1011989)Task 1 covers the following topics:Plant Partitioning Analysis
-Define Global Analysis Boundary
-Partition into physical analysis units (PAUs) 3Corresponding PRA Standard ElementTask 1 maps to element PP
-Plant Partitioning
-PP Objectives (per the PRA Standard):To define the global analysis boundaryTo define physical analysis units 4PP HLRs (per the PRA Standard)HLR-PP-A: The Fire PRA shall define global boundaries of the analysis so as to include all plant locations relevant to the plant
-wide Fire PRA (1 SR)HLR-PP-B: The Fire PRA shall perform a plant partitioning analysis to identify and define the physical analysis units to be considered in the Fire PRA (7 SRs)HLR-PP-C: The Fire PRA shall document the results of the plant partitioning analysis in a manner that facilitates Fire PRA applications, upgrades, and peer review (4 SRs) 5Support Task A: Plant WalkdownsJust a Quick Note-.You cannotcomplete a Fire PRA without walkdownsExpect to conduct a number of walkdowns, especially for key areas (e.g., those analyzed in detail)Walkdownscan have many objectives and support many tasks:
-Partitioning features, equipment/cable mapping, fire ignition source counting, fire scenario definitions, fire modeling, detection and suppression features, operator actions HRAWalkdownsare generally a team activity so coordinate them to optimize personnel time and resourcesTake a camera and/or tablet if you can, keep good recordsCorresponding PRA Standard SR: PP
-B7 6Plant PartitioningGeneral Comment/ObservationThe recommended practice for Task 1 has changed little from prior methods.
-That means you can likely benefit from a previous analysise.g., your IPEEE fire analysis
-However: watch out for new equipment/cables, new initiators when screeningMay need to work closely with the cable routing experts to ensure coordination among the plant partitioning schemes
-A naming convention is one important issue here 7Task 1: Plant PartitioningKey Definitions: PAU vs. Fire Area/ZonePAUsare defined in the context of the Fire PRA only-They become the basis for analysis managementFire Areas are defined in the context of your regulatory compliance fire protection programFire Zones are generally defined in the context of fire protection features (e.g., detection, suppression, hazards)
-Fire zones have no direct meaning to the Fire PRA context and we avoid using this termBTW--PAU is "standard
-speak"-6850/1011989 used the term "compartments"
-We'll use Compartments andPAUs interchangeably 8Task 1: Plant PartitioningTask Objectives and OutputThere are two main objectives to Task 1:1. Define the Global Analysis BoundaryThe maximum physical extent of the plant that will be considered in the Fire PRA2. Divide the areas within the Global Analysis Boundary into analysis Physical Analysis UnitsThe basic physical units that will be analyzed and for which risk results will be reportedTask output isthe definition of these two aspects of the analysis 9Internal vs. external in PRA space and the implications of the Global Analysis BoundaryThe language here is changing!Historically we talked about "internal events" and "external events"
-Terms used to mean that the failures setting off an accident sequence either occurred internalor externalto plant systems/components
-Fire attacks equipment from the outside versus random failures that occur within the system/component
-Historically, fire was referred to as an external eventThe PRA standard used a different split:
-Internal Hazards
-External HazardsUnder the standard:
-Internal fires are an internal hazard
-External fires are an external hazard 10Internal vs. external in PRA space and the implications of the Global Analysis BoundaryKey notion: The global analysis boundary defines the split between internal and externalfires-This notion has now been accepted as a part of the standard at least in the context of fireSo going forward-
-We are talking about internal fires
--Which are part of the internal hazard groupBe careful
-folks will still refer to fires as an external event
-Not a big deal, but don't be surprised 11Task 1: Plant PartitioningTask InputNo real input from any other task is required (it is, after all, Task 1)-You may also find yourself iterating back to this task later in the analysis -that is fine, just be careful to track any changes
-A word of Caution: Many things will be traced and assigned based on the fire compartments. If you change partitioning decisions later, there are consequences relative to information trackingWhat do you need to support this Task?
-Layout drawings that identify major structures, walls, openingsDrawings that identify Fire Areas are especially helpful
-Plan andelevation drawings are helpful
-You willneed to do a walkdownto support/verify decisions 12Task 1: Plant PartitioningTask Breakdown in StepsTask 1 has four steps: Step 1: Selection of Global Plant Analysis BoundaryStep 2: Plant PartitioningStep 3: Compartment Information Gathering and CharacterizationStep 4: Documentation 13Task 1: Plant PartitioningStep 1:Selection of Global Plant Analysis BoundaryWe generally recommend a liberaldefinition of the global analysis boundary-It's OK to include obviously unimportant areas, we'll drop them quickly, but better to do this formally
-Alternative is to explain choices/exclusions in your documentationEncompass all areas of the plant associated with both normal and emergency reactor operating including support systems and power productionSister units should be included unless they are physically and functionally separated
-Separated means:
noshared areas, noshared systems, noshared components and associated cables, noconjoined areas (e.g., shared walls) 14Task 1: Plant PartitioningSelection of Global Plant Analysis BoundaryBegin with your protected area: everything within the protected area should be included in the Global Analysis Boundary-In most cases that will capture all risk
-important locationsIf necessary, expand the boundary to include any other locations that house equipment or cables identified in Tasks 2 or 3
-This is the Task 2/3 link mentioned before!
-Example: If your offsite power related equipment is outside the protected area, you need to expand the Global Analysis Boundary to capture itCorresponding PRA Standard SR: PP
-A1 15Task 1: Plant PartitioningSelection of Global Plant Analysis BoundaryBy the end of the analysis, you need to provide a fire risk disposition for all locations within the global analysis boundary-Some locations may screen qualitatively
-Some may screen quantitatively
-Some willbe quantified in detail
-Bottom line
-all locations need some resolution 16Task 1: Plant PartitioningStep 2: Plant Partitioning (into PAUs)We divide the Global Analysis Boundary into smaller pieces (PAUs) for the purpose of tracking and reporting risk resultsA PAU can be many things, but when it comes down to it, a PAU is:A well-defined volume within the plant - that is expected to substantially contain the adverse effects of fires 17Task 1: Plant PartitioningPlant Partitioning into Fire CompartmentsThis task is often subjective
-judgment isrequiredIdeally: PAU = Room
-Locations that are fully defined by physical partitioning features such as walls, floors, and ceilingsBut the ideal is not the only solution
-other features and elements may be credited in partitioning
-That's where judgment comes into play!
-You must decide what to credit as a partitioning feature and then document and justify your choices
-Cable routing should be an influencing factor 18Task 1: Plant PartitioningPlant Partitioning into Fire CompartmentsA good starting point is your Fire Areas, but you are by no means limitedto equating PAUs to Fire Areas
-A Fire Area may be partitioned to two or more PAUs
-You may combine two or more Fire Areas into a single PAUIn the end: { Bnd. }-No omissions
-No overlapCorresponding PRA Standard SR: PP
-B6 19Task 1: Plant PartitioningPlant Partitioning into Fire PAUsSo what can you credit as a partitioning feature:
-Bottom line: anything you can justify
-see text for examplesYou do need to justify your decisions with the exception of structural elements maintained as rated fire barriers
-In the end, your partitioning decisions should not affect the risk results, but . .
-Don't go crazy
-there are disadvantages to over
-partitioning
-General guideline: try to minimize the need to develop and analyze multi-compartment scenariosCorresponding PRA Standard SR: PP
-B1 20Task 1: Plant PartitioningPlant Partitioning into Fire PAUsIt is not recommended to partition based on:
-Radiant energy shields
-Beam pockets
-Equipment obstructions (e.g., pipes)
-Per the PRA Standard: raceway wraps and other localized fire barriers may not be creditedin partitioningSpatial separation credited as partitioning scheme requires justification
-e.g., significant separation distances with no ignition sources, very limited fuel loadsCorresponding PRA Standard SRs: PP
-B2, B3, B4 and B5 21Task 1: Plant PartitioningPlant Partitioning into Fire PAUsFinal Point: You need a system to identify/name your PAUs
-Something both consistent and logical
-but whatever works for your application and plant
-Often makes sense to use Fire Area designations in naming schemesExample: Fire Area 42 might become PAUs 42A, 42B-
-Use your naming scheme consistently throughout the Fire PRADocumentation, equipment/cable routing database, etc.
22Task 1: Plant PartitioningStep 3: PAU Information GatheringLater tasks need certain information about each PAU. They include, but are not limited to the following:
-PAU boundary characteristics
-Ventilation features, and connections
-Fire protection features
-Identification of all adjacent PAUs
-Access routes to the fire PAU 23Task 1: Plant PartitioningPAU Information GatheringA thorough plant walkdownis needed to confirm and gather information about each fire PAUIt is unlikely that all information will be collected and documented during the first passAs work on fire PRA progresses, additional information, as needed, is collected and documentedThis task, similar to other later tasks, is expected to be revisited and PAU definitions modified as additional information is obtained 24Task 1: Plant PartitioningSummaryPlant Partitioning is the first task of the fire PRATask is done in three steps:
1.Define global plant analysis boundaries to include all those area that will be addressed by the fire PRA 2.Define fire PAUs in such a way that all the areas identified in the preceding step are covered, there are no overlaps and there is a balance between size and number of PAUs selected 3.Confirm the selected PAUs through a walkdownand record important information that will be used later.
25Mapping HLRs & SRs for the PP Technical Element to NUREG/CR-6850, EPRI 1011989Technical Elem e n t HLR SR 6850 Sections Comments The Fire PRA shall define global boundaries of the analysis so as to include all plant locations relevant to the plant
-wide Fire PRA A 1 1.5.1 The Fire PRA shall perform a plant partitioning analysis to identify and define the physical analysis units to be considered in the Fire PRA 1 1.5.2 2 1.3.2 and 1.5.2 3 1.3.2 and 1.5.2 4 1.3.2 and 1.5.2 Cable raceway fire barriers are not explicitly addressed in 6850 5 1.3.2 and 1.5.2 6 1.5.2 B 7 1.4.3, 1.5.2 and 1.5.3 The fire PRA shall document the results of the plant partitioning analysis in a manner that facilitates Fire PRA applications, upgrades, and peer review 1 n/a 2 n/a The requirements within these SRs are not specifically addressed in Section 1.5.4 of 6850.
3 1.5.4 PP C 4 1.5.2