ML19162A419

01_04 Task 5 Risk Model

ML19162A419
Person / Time
Issue date:	06/13/2019
From:	Nick Melly NRC/RES/DRA
To:
T. Rivera
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ML19162A411	List: ML19162A412 ML19162A413 ML19162A414 ML19162A415 ML19162A416 ML19162A417 ML19162A418 ML19162A419 ML19162A420 ML19162A421
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NUREG/CR-6850 FIRE PRA METHODOLOGY Module 1 Internal Event, At-Power Probabilistic Risk Assessment Model for SNPP Task 5: Fire-Induced Risk Model Development Nicholas Melly - Nuclear Regulatory Commission Fire PRA Workshop June 24, 2019 - June 28, 2019 Rockville, MD U.S. NRC HQ

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 2 Fire PRA Risk Model Purpose (per 6850/1011989)

Purpose:

Describe the procedure for developing the Fire PRA model to calculate CDF, CCDP, LERF, and CLERP for fire ignition events Fire Risk Model Key input for Quantitative Screening (Task 7)

Used to quantify CDF/CCDP and LERF/CLERP Process is iterative to ensure appropriate agreement among fire PRA Component List, Fire PRA Model, cable identification, and quantitative screening

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 3 Fire PRA Risk Model Corresponding PRA Standard Element Primary match is to element PRM - Equipment Selection PRM Objectives (as stated in the PRA standard):

(a) to identify the initiating events that can be caused by a fire event and develop a related accident sequence model. (b) to depict the logical relationships among equipment failures (both random and fire induced) and human failure events (HFEs) for CDF and LERF assessment when combined with the initiating event frequencies

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 4 Fire PRA Risk Model HLRs (per the PRA Standard)

HLR-PRM-A: The Fire PRA shall include the Fire PRA plant response model capable of supporting the HLR requirements of FQ HLR-PRM-B: The Fire PRA plant response model shall include fire-induced initiating events, both fire induced and random failures of equipment, fire-specific as well as non-fire-related human failures associated with safe shutdown, accident progression events (e.g., containment failure modes), and the supporting probability data (including uncertainty) based on the SRs provided under this HLR that parallel, as appropriate, Part 2 of this Standard, for Internal Events PRA HLR-PRM-C: The Fire PRA shall document the Fire PRA plant response model in a manner that facilitates Fire PRA applications, upgrades, and peer review

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 5 Fire PRA Risk Model Scope (per 6850/1011989)

Task 5: Fire-Induced Risk Model Development Constructing the PRA Model Step 1-Develop the Fire PRA CDF/CCDP Model Step 2-Develop the Fire PRA LERF/CLERP Model

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 6 Fire PRA Risk Model General Comment/Observation Task 5 does not represent any changes from past practice, but what is modeled is largely based on Task 2 with HRA input from Task 12 Bottom line - Just tweaking your Internal Events PRA is probably NOT sufficient

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 7 Task 5: Fire Risk Model Development General Objectives

Purpose:

Configure the Internal Events PRA to provide fire risk metrics of interest (primarily CDF and LERF)

Based on standard state-of-the-art PRA practices Intended to be applicable for any PRA methodology or software Allows user to quantify CDF and LERF, or conditional metrics CCDP and CLERP Conceptually, nothing new here - Need to build the PRA model reflecting fire induced initiators, equipment and failure modes, and human actions of interest

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 8 Task 5: Fire Risk Model Development Inputs/Outputs Task inputs and outputs:

Inputs from other tasks: (Note: Inclusion of spatial information requires cable locations from Task 3)

Sequence considerations, initiating event considerations, and components from Task 2 (Fire PRA Component Selection)

Unscreened fire compartments from Task 4 (Qualitative Screening)

HRA events from Task 12 (Post-Fire HRA)

Output to Task 7 (Quantitative Screening) which will further modify the model development Can always iterate back to refine aspects of the model

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 9 Task 5: Fire Risk Model Development Steps in Procedure Two major steps:

Step 1: Develop CDF/CCDP model Step 2: Develop LERF/CLERP model

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 10 Task 5: Fire Risk Model Development Steps in Procedure/Details Step 1 (2): Develop CDF/CCDP (LERF/CLERP) models Step 1.1 (2.1): Select fire-induced initiators and sequences and incorporate into the model Corresponding SRs: PRM-A1, A2, A3, B1-B15 Fire initiators are generally defined in terms of compartment fires or fire scenarios Each fire initiator is mapped to one or more internal event initiators to mimic the fire-induced impact to the plant Initiating events previously screened in the internal events analysis may have to be reconsidered for the Fire PRA Final mapping of fire initiator to internal events initiators is based on cable routing information (Task 3)

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 11 Task 5: Fire Risk Model Development Steps in Procedure/Details (Cont.)

Step 1.1 (2.1) - (Cont.)

The structure of Internal Events PRA should be reviewed to determine proper mapping of fire initiators The Internal Events PRA should have the capability to quantify CDF and LERF sequences Internal events sequences form bulk of sequences for Fire PRA, but a search for new sequences should be made (see Task 2). Some new sequences may require new logic to be added to the PRA model Plants that use fire emergency procedures (FEPs) may need special models to address unique fire-related actions (e.g., pre-defined fire response actions and MCR abandonment)

Some human actions may induce new sequences not covered in Internal Events PRA and can fail components

Example: SISBO, or partial SISBO

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 12 Task 5: Fire Risk Model Development Steps in Procedure/Details (Cont.)

Loss of raw water as initiator Fire in compartment A-1 Loss of raw water (internal)

Initiator Initiator Example of new logic with a fire-induced loss of raw water initiating event

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 13 Task 5: Fire Risk Model Development Steps in Procedure/Details (Cont.)

Step 1.2 (2.2): Incorporate fire-induced equipment failures Corresponding SRs: PRM-A4, B3, B6, B9 Fire PRA database documents list of potentially failed equipment for each fire compartment Basic events for fire-induced spurious operations are defined and added to the PRA model (FAQ 08-0047)

Inclusion of spatial information requires equipment and cable locations

May be an integral part of model logic or handled with manipulation of a cable location database, etc.

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 14 Task 5: Fire Risk Model Development Steps in Procedure/Details (Cont.)

Loss of high pressure injection Loss of train A Loss of train B Pump A fails to start Pump A fails to run Original logic Valve fails to open Suppose fire in compartment L1 or L2 could fail pump A because pump A is in L1 and cable for pump A is in L2 etc.

Loss of high pressure injection Loss of train A Loss of train B Possible temporary change to model to run CCDPs for L1 and L2 etc.

Set to TRUE Pump A fails to start Pump A fails to run Valve fails to open

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 15 Task 5: Fire Risk Model Development Steps in Procedure/Details (Cont.)

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 16 Task 5: Fire Risk Model Development Steps in Procedure/Details (Cont.)

Loss of high pressure injection Loss of train B etc.

Loss of train A Pump A fails to start Pump A fails to run Valve fails to open Fire in compartment L1 fails pump A Permanent change to model Initiator Fire in compartment L2 fails pump A Initiator Pump A fails to start

- hardware Pump A fails to start

- fire

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 17 Task 5: Fire Risk Model Development Steps in Procedure/Details (Cont.)

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 18 Task 5: Fire Risk Model Development Steps in Procedure/Details (Cont.)

Step 1.3 (2.3): Incorporate fire-induced human failures Corresponding SRs: PRM-B9, B11 New fire-specific HFEs may have to be added to the model to address actions specified in FEPs (Note: All HFEs will be set at screening values at first, using Task 12 guidance)

Successful operator actions may temporarily disable (fail) components

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 19 Task 5: Fire Risk Model Development Steps in Procedure/Details (Cont.)

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 20 Task 5: Fire Risk Model Development Steps in Procedure/Details (Cont.)

Suppose a proceduralized manual action carried out for fires in compartments AA & BB defeats Pump A operation by de-energizing the pump (opening its breaker drawer)

Pump A fails etc.

Pump A fails to start Pump A fails to run Operator action defeats pump operation Relevant fires Operator opens pump A breaker as directed Fire in compartment AA Fire in compartment BB Initiator Initiator

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 21 Sample Problem Exercise for Task 5 Distribute blank handout for Task 5, Steps 1 and 2 Distribute completed handout for Task 5, Steps 1 and 2 Question and Answer Session

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 22 Mapping HLRs & SRs for the PRM Technical Element to NUREG/CR-6850, EPRI TR 1011989 Technical element HLR SR 6850/1011989 sections that cover SR Comments PRM A

The Fire PRA shall include the Fire PRA plant response model capable of supporting the HLR requirements of FQ.

1 5.5.1.1, 5.5.2.1 2

5.5.1.1, 5.5.2.1 3

5.5.1.1, 5.5.2.1 4

5.5.1.1, 5.5.1.2, 5.5.2.1, 5.5.2.2

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 23 Mapping HLRs & SRs for the PRM Technical Element to NUREG/CR-6850, EPRI TR 1011989 Technical element HLR SR 6850/1011989 sections that cover SR Comments PRM B

The Fire PRA plant response model shall include fire-induced initiating events, both fire induced and random failures of equipment, fire-specific as well as non-fire-related human failures associated with safe shutdown, accident progression events (e.g., containment failure modes),

and the supporting probability data (including uncertainty) based on the SRs provided under this HLR that parallel, as appropriate, Part 2 of this Standard, for Internal Events PRA.

1 5.5.1.1, 5.5.2.1 2

5.5.1.1, 5.5.2.1 3

5.5.1.1, 5.5.1.2, 5.5.2.1, 5.5.2.2 4

5.5.1.1, 5.5.2.1 5

5.5.1.1, 5.5.2.1 6

5.5.1.1, 5.5.1.2, 5.5.2.1, 5.5.2.2 7

5.5.1.1, 5.5.2.1 8

5.5.1.1, 5.5.2.1 9

5.5.1.1, 5.5.1.2, 5.5.1.3, 5.5.2.1, 5.5.2.2, 5.5.2.3 10 5.5.1.1, 5.5.2.1 11 5.5.1.1, 5.5.1.3, 5.5.2.1, 5.5.2.3 12 5.5.1.1, 5.5.2.1 13 5.5.1.1, 5.5.2.1 14 5.5.1.1, 5.5.2.1 15 5.5.1.1, 5.5.2.1 12 5.5.1.1, 5.5.2.1 13 5.5.1.1, 5.5.2.1 14 5.5.1.1, 5.5.2.1 15 5.5.1.1, 5.5.2.1

Fire PRA Workshop 2019, Rockville, MD Module 1: Internal Event, At-Power PRA Model for SNPP Slide 24 Mapping HLRs & SRs for the PRM Technical Element to NUREG/CR-6850, EPRI TR 1011989 Technical element HLR SR 6850/1011989 sections that cover SR Comments C

The Fire PRA shall document the Fire PRA plant response model in a manner that facilitates Fire PRA applications, upgrades, and peer review.

1 n/a Documentation not covered in 6850/1011989