ML21096A183

Item 5 IDHEAS Dependency Model and Guidance by J Xing - 2021-04-08 Public Meeting

ML21096A183
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Issue date:	04/08/2021
From:	Chang Y, Michelle Kichline, Jing Xing NRC/RES/DRA/HFRB
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Xing, Jang - 301 415 2410
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IDHEAS dependency model and guidance (IDHEAS-DEP)

Jing Xing, Michelle Kichline, Y. James Chang,,

U.S. Nuclear Regulatory Commission Presented by Jing Xing to the public meeting on IDHEAS April-08-2021

Overview

1. IDHEAS Dependency Model

2. NRC 2021 HRA Dependency Workgroup

3. Guidance for using IDHEAS Dependency Model in HRA

4. Path forward with IDHEAS dependency 2

IDHEAS-G Dependency Model Identify the dependency context (HFE1, HFE2)

• Consequential dependency in an event sequence

• Resource-sharing dependency

• Cognitive dependency HFE1 and HFE2 are Model the dependency context HFE2lHFE1 independent All no Any Are there changes to HFE2s:

Definition? Time required and time available?

P(HFE1,HFE2)= yes?

Feasibility? Additional CFMs?

P(HFE1)*P(HFE2) Critical tasks? PIF attributes?

Yes Calculate P(HFE2lHFE1) based on P(HFE1,HFE2) =

context changes to HFE2 and using P(HFE1)*P(HFE2lHFE1) same method as individual HFEs HFE2lHFE1 means the occurrence of event HFE2 given the occurrence of event HFE1, where HFE1 is the first event and HFE2 is the second event. 3

NRC HRA Dependency Workgroup (Nov. 2020 - March 2021)

Purpose:

Understand HRA dependency and develop guidance for using IDHEAS Dependency Model

• Activities:

- Phase 1: Six analysts each performed dependency analysis of an example event (from SDP or PRA models) using IDHEAS-ECA and IDHEAS Dependency Model

- Phase 2: The project team developed the draft guidance and the analysts piloted it with the examples

- Phase 3: The workgroup will review and comment on the fully written guidance

• Workgroup members:

- A. Brown, C. Hunter, J. DeJesus, M. Pohida, and K. Tetter, Reliability And Risk Analysts, NRR and RES

- A. Rosebrook, Sr. Reactor Analyst, Region II

- K. Gunter, Lead Engineer, Jensen Hughes Company

- M. Presley, Principal Technical Leader, EPRI 4

IDHEAS dependency guidance framework HFE2HFE1 Pre-determination:

Assess the relationships between Entry conditions No STOP met?

the HFEs for no dependency, complete dependency, or further Yes No dependency analysis Step 1 Pre-determination Complete Screening analysis:

dependency Assessing screening dependent HEPs without using IDHEAS-ECA (for HRA applications where detailed information is not Step 2 Step 3 available or the individual HEPs of Screening analysis Detailed analysis the HFEs were not from IDHEAS-ECA)

Graded screening IDHEAS-ECA calculated Detailed analysis: dependent HEP dependent HEP Analyze dependency factors and their impact on HEPs using IDEHAS-ECA

Preliminary insights on IDHEAS dependency guidance

• IDHEAS dependency analysis is based on IDHEAS-G and IDHEAS-DATA

- THERP dependency: Each relationship deems a multiplier

- IDHEAS dependency: The context of each relationship is analyzed for its impact on the dependent HEP

• The assessed dependency is explainable on why the dependency occurs and how it impacts HEPs

- Enhanced HRA traceability and documentation

- Explicit identification of dependency mechanisms for reducing dependency

• Preliminary piloting of the draft dependency guidance dependency shows promise

- that the dependent HEPs calculated from IDHEAS dependency model were more consistent with analysts assessment, not overly conservative 6

Path forward with IDHEAS dependency

• IDHEAS Dependency Model in IDHEAS-G report (NUREG-2198)

Appendix K, in publication, 2021

• Publish The guidance for using IDHEAS Dependency Model (IDHEAS-DEP) as a NRC Research Information Letter and collect public comments

- summer 2021

• Document and publish the dependency analysis examples from the NRC Dependency Workgroup - summer 2021

• Update IDHEAS-ECA report and software tool by incorporating IDHEAS dependency guidance - winter 2021 7