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 3

Identify the dependency context Consequential dependency Resource-sharing dependency Cognitive dependency (HFE1, HFE2) in an event sequence Model the dependency context HFE2lHFE1 Are there changes to HFE2s:

Definition? Time required and time available?

Feasibility?

Additional CFMs?

Critical tasks? PIF attributes?

HFE1 and HFE2 are independent P(HFE1,HFE2)=

P(HFE1)*P(HFE2)

Calculate P(HFE2lHFE1) based on context changes to HFE2 and using same method as individual HFEs Any yes?

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.

All no Yes P(HFE1,HFE2) =

P(HFE1)*P(HFE2lHFE1)

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- Phase 2: The project team developed the draft guidance and the analysts piloted it with the examples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 Step 2 Screening analysis Graded screening dependent HEP No dependency Entry conditions met?

Yes No STOP HFE2HFE1 Complete dependency Step 1 Pre-determination Step 3 Detailed analysis IDHEAS-ECA calculated dependent HEP Pre-determination:

Assess the relationships between the HFEs for no dependency, complete dependency, or further analysis Screening analysis:

Assessing screening dependent HEPs without using IDHEAS-ECA (for HRA applications where detailed information is not available or the individual HEPs of the HFEs were not from IDHEAS-ECA)

Detailed analysis:

Analyze dependency factors and their impact on HEPs using IDEHAS-ECA

Preliminary insights on IDHEAS dependency guidance 6

• 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

Path forward with IDHEAS dependency 7

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