ML21098A128

1D - Modeling Overview

ML21098A128
Person / Time
Issue date:	04/06/2021
From:	Gabe Taylor Office of Nuclear Regulatory Research
To:
Kenneth Hamburger
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ML21098A124	List: ML21098A125 ML21098A126 ML21098A128 ML21098A129 ML21098A131
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Download: ML21098A128 (7)

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Modeling Overview Gabriel Taylor, P.E.

Office of Nuclear Regulatory Research

Overview of ZOI development Current Duration Scenario Equipment Config.

Material Modeling + Fragility = ZOI Tables Incident Energy Target Vulnerability Zone of Influence (ZOI)

Heat Flux Threshold HEAF Research Working Group Update - April 6th, 2021 2

Flashback : April 2018 Merging with incorporation of CFD modeling insights HEAF Research Working Group Update - April 6th, 2021 3

Modeling Approaches

• SNL SIERRA Suite

- Multi-physics coupled model

- Focus on modeling arc (source term)

• NIST FDS

- CFD modeling

- Focus on modeling thermal transport to target

• Empirical

- Data fit

- Focus on specific phenomena; enclosure breach, arc voltage HEAF Research Working Group Update - April 6th, 2021 4

Modeling Scenarios

• Medium Voltage, Non-segregated phase bus duct

Enclosure:

Steel or Aluminum

- Conductors: Aluminum or Copper

• Medium Voltage Switchgear

- Configuration: Supply, Main, Load

- Energy Profile: Stiff, Decay, or Stiff + Decay

- Conductors: Aluminum or Copper

• Low Voltage Switchgear

- Conductors: Aluminum or Copper HEAF Research Working Group Update - April 6th, 2021 5

Scenario Consolidation

• PRA document covers over 300 scenarios for just aluminum

• Low energy scenarios are being removed from initial list using empirical correlations and slightly conservative fragility thresholds

• Reduces scenario list by 88%

• Some scenarios have similar or identical hazard and can be consolidated even further HEAF Research Working Group Update - April 6th, 2021 6

Summary

• Overall approach to decouple modeling and fragility efforts remains intact

• Modeling approach has evolved into a hybrid between category and dynamic

• PRA guidance document supports defining model scenarios

• Modeling appears to provide reasonable estimates to inform the working groups ZOI determination. However, areas for uncertainty reduction exist.

HEAF Research Working Group Update - April 6th, 2021 7