ML19134A239
| ML19134A239 | |
| Person / Time | |
|---|---|
| Issue date: | 05/20/2019 |
| From: | Michael Benson, Sara Lyons, Robert Tregoning Office of Nuclear Regulatory Research |
| To: | |
| Shared Package | |
| ML19136A264 | List: |
| References | |
| Download: ML19134A239 (8) | |
Text
High Energy Line Break (HELB)
Michael Benson, Sara Lyons, Robert Tregoning Office of Nuclear Regulatory Research U.S. Nuclear Regulatory Commission NRC/Industry Materials Programs Technical Information Exchange May 21-22, 2019
High Energy Line Break Issue
- Some plants may have difficulty meeting this limit for subsequent license renewal
- Identified as a possible issue for new plants
- EPRI proposed a risk-informed alternative for establishing postulated break locations (EPRI 1022873, 2011) 2
Branch Technical Position 3-4
- Safety-related components must be designed to accommodate the effects of and to be compatible with the environmental conditions associated with postulated accidents
- SRP 3.6.2
- Describes methods acceptable to the staff for complying with GDC 4
- Provides guidance for jet force modeling
- References Branch Technical Position 3-4 (BTP 3-4)
- Branch Technical Position 3-4
- Includes criteria for selecting postulated break locations
- Stress-based criteria
- CUF criterion 3
History of CUF Criterion
- First record - 1972 Giambusso letter (Appendix B of BTP 3-3, ML070800027)
- Early BTP versions only consider CUF criterion when the maximum stress range exceeds a certain value; provision eliminated in later versions
- January 2012 public meeting on fatigue issues (ML120120028)
- EPRI presented risk-informed approach to postulated break locations (Report 1022873)
- If environmental effects were accounted for, staff demonstrated willingness to accept 0.4
- Staff was not aware of a compelling reason to update the criterion at that time
- Economic Simplified Boiling Water Reactor Design Certification
- Staff permitted a relaxed CUF criterion if environmental effects considered
- BTP3-4 updated to state CUF limit of 0.4 when environmental effects considered
- Recently, staff has developed a draft technical letter report describing the history of BTP 3-4, with a focus on the CUF criterion 4
HELB/CUF Issue Timeline at NRC 2010 NRR/NRO User Need Request (UNR) included investigation of CUF criterion 2012
- January 5th Environmentally Assisted Fatigue (EAF) public meeting (meeting summary: ML120120028)
- Industry identified no need to address until 2020s
- NRC delayed work associated with 2010 UNR until completion of xLPR 2014 NRO escalated HELB issue for new reactors 2015 Second NRR/NRO UNR included investigation of CUF criterion 2018 September 25th EAF public meeting (meeting summary:
ML18289A322) 5
Technical Letter Report
- Discusses current stress and fatigue criteria in BTP 3-4
- Summarizes historical background of BTP 3-4 development
- Describes existing proposed alternatives to the current CUF criterion 6
Current Status
- Technical Letter Report documenting background and known bases for CUF criteria for existing and new reactors is being finalized for public release
- June 11, 2019 - NRC public meeting to discuss HELB and potential drivers warranting further work 7
Public Meeting Draft Agenda
- Introductions and meeting objective
- Background
- Overview of EPRI 1022873 report
- Overview of NRC comments on EPRI 1022873 report
- Design certification for new reactors
- Discussion of next steps to:
- identify a regulatory path forward
- develop the technical basis supporting proposed changes 8