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: |
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| Download: ML18213A080 (25) | |
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Module III - Fire Analysis Task 1 - Plant Partitioning Joint EPRI/NRC-RES Fire PRA Workshop August 6-10, 2018 A Collaboration of the Electric Power Research Institute (EPRI) & U.S. NRC Office of Nuclear Regulatory Research (RES)
Plant Partitioning Scope (per 6850/1011989)
Task 1 covers the following topics:
Plant Partitioning Analysis
- Define Global Analysis Boundary
- Partition into physical analysis units (PAUs) 2
Corresponding PRA Standard Element Task 1 maps to element PP - Plant Partitioning
- PP Objectives (per the PRA Standard):
To define the global analysis boundary To define physical analysis units 3
PP 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) 4
Support Task A: Plant Walkdowns Just a Quick Note.
You cannot complete a Fire PRA without walkdowns Expect to conduct a number of walkdowns, especially for key areas (e.g., those analyzed in detail)
Walkdowns can 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 HRA Walkdowns are generally a team activity so coordinate them to optimize personnel time and resources Take a camera and/or tablet if you can, keep good records Corresponding PRA Standard SR: PP-B7 5
Plant Partitioning General Comment/Observation The recommended practice for Task 1 has changed little from prior methods.
- That means you can likely benefit from a previous analysis e.g., your IPEEE fire analysis
- However: watch out for new equipment/cables, new initiators when screening May 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 6
Task 1: Plant Partitioning Key Definitions: PAU vs. Fire Area/Zone PAUs are defined in the context of the Fire PRA only
- They become the basis for analysis management Fire Areas are defined in the context of your regulatory compliance fire protection program Fire 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 term BTW
- PAU is standard-speak
- 6850/1011989 used the term compartments
- Well use Compartments and PAUs interchangeably 7
Task 1: Plant Partitioning Task Objectives and Output There are two main objectives to Task 1:
- 1. Define the Global Analysis Boundary The maximum physical extent of the plant that will be considered in the Fire PRA
- 2. Divide the areas within the Global Analysis Boundary into analysis Physical Analysis Units The basic physical units that will be analyzed and for which risk results will be reported Task output is the definition of these two aspects of the analysis 8
Internal vs. external in PRA space and the implications of the Global Analysis Boundary The 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 internal or external to 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 event The PRA standard used a different split:
- Internal Hazards
- External Hazards Under the standard:
- Internal fires are an internal hazard
- External fires are an external hazard 9
Internal vs. external in PRA space and the implications of the Global Analysis Boundary Key notion: The global analysis boundary defines the split between internal and external fires
- This notion has now been accepted as a part of the standard at least in the context of fire So going forward
- We are talking about internal fires
- Which are part of the internal hazard group Be careful - folks will still refer to fires as an external event
- Not a big deal, but dont be surprised 10
Task 1: Plant Partitioning Task Input No 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 tracking What do you need to support this Task?
- Layout drawings that identify major structures, walls, openings Drawings that identify Fire Areas are especially helpful
- Plan and elevation drawings are helpful
- You will need to do a walkdown to support/verify decisions 11
Task 1: Plant Partitioning Task Breakdown in Steps Task 1 has four steps:
Step 1: Selection of Global Plant Analysis Boundary Step 2: Plant Partitioning Step 3: Compartment Information Gathering and Characterization Step 4: Documentation 12
Task 1: Plant Partitioning Step 1:Selection of Global Plant Analysis Boundary We generally recommend a liberal definition of the global analysis boundary
- Its OK to include obviously unimportant areas, well drop them quickly, but better to do this formally
- Alternative is to explain choices/exclusions in your documentation Encompass all areas of the plant associated with both normal and emergency reactor operating including support systems and power production Sister units should be included unless they are physically and functionally separated
- Separated means: no shared areas, no shared systems, no shared components and associated cables, no conjoined areas (e.g., shared walls) 13
Task 1: Plant Partitioning Selection of Global Plant Analysis Boundary Begin 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 locations If 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 it Corresponding PRA Standard SR: PP-A1 14
Task 1: Plant Partitioning Selection of Global Plant Analysis Boundary By 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 will be quantified in detail
- Bottom line - all locations need some resolution 15
Task 1: Plant Partitioning Step 2: Plant Partitioning (into PAUs)
We divide the Global Analysis Boundary into smaller pieces (PAUs) for the purpose of tracking and reporting risk results A 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 16
Task 1: Plant Partitioning Plant Partitioning into Fire Compartments This task is often subjective - judgment is required Ideally: PAU = Room
- Locations that are fully defined by physical partitioning features such as walls, floors, and ceilings But the ideal is not the only solution - other features and elements may be credited in partitioning
- Thats 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 17
Task 1: Plant Partitioning Plant Partitioning into Fire Compartments A good starting point is your Fire Areas, but you are by no means limited to 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 PAU In the end: { PAUs } { Global Analysis Bnd. }
- No omissions
- No overlap Corresponding PRA Standard SR: PP-B6 18
Task 1: Plant Partitioning Plant Partitioning into Fire PAUs So what can you credit as a partitioning feature:
- Bottom line: anything you can justify - see text for examples You 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 . .
- Dont go crazy - there are disadvantages to over-partitioning
- General guideline: try to minimize the need to develop and analyze multi-compartment scenarios Corresponding PRA Standard SR: PP-B1 19
Task 1: Plant Partitioning Plant Partitioning into Fire PAUs It 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 credited in partitioning Spatial separation credited as partitioning scheme requires justification
- e.g., significant separation distances with no ignition sources, very limited fuel loads Corresponding PRA Standard SRs: PP-B2, B3, B4 and B5 20
Task 1: Plant Partitioning Plant Partitioning into Fire PAUs Final 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 schemes Example: Fire Area 42 might become PAUs 42A, 42B
- Use your naming scheme consistently throughout the Fire PRA Documentation, equipment/cable routing database, etc.
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Task 1: Plant Partitioning Step 3: PAU Information Gathering Later 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 22
Task 1: Plant Partitioning PAU Information Gathering A thorough plant walkdown is needed to confirm and gather information about each fire PAU It is unlikely that all information will be collected and documented during the first pass As work on fire PRA progresses, additional information, as needed, is collected and documented This task, similar to other later tasks, is expected to be revisited and PAU definitions modified as additional information is obtained 23
Task 1: Plant Partitioning Summary Plant Partitioning is the first task of the fire PRA Task 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 walkdown and record important information that will be used later.
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Mapping HLRs & SRs for the PP Technical Element to NUREG/CR-6850, EPRI 1011989 Technical HLR SR 6850 Sections Comments Element 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 1.5.1 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 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 7 1.4.3, 1.5.2 and 1.5.3 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 1 n/a The requirements within these SRs are not 2 n/a specifically addressed in Section 1.5.4 of 6850.
3 1.5.4 4 1.5.2 25