ML19161A107
| ML19161A107 | |
| Person / Time | |
|---|---|
| Issue date: | 06/10/2019 |
| From: | Michael Benson, Robert Tregoning Office of Nuclear Regulatory Research |
| To: | |
| Robert Tregoning | |
| Shared Package | |
| ML19161A105 | List: |
| References | |
| Download: ML19161A107 (10) | |
Text
Introduction and Background Michael Benson and Robert Tregoning Office of Nuclear Regulatory Research U.S. Nuclear Regulatory Commission Public Meeting to Discuss BTP 3-4 Criteria for Postulating Pipe Rupture Locations June 11, 2019
Branch Technical Position (BTP) 3-4
- Methods acceptable to the staff for postulating break locations
- Standard Review Plan (SRP) 3.6.2
- General Design Criterion 4, Environmental and Dynamic Effects Design Basis 2
Cumulative Usage Factor Criterion
- Variety of guidance related to postulating break locations
- Separation of components, stress-based criteria, design of pipe restraints
- B 1. (ii) (b) has attracted stakeholder interest (similar sections, as well)
- Cumulative usage factor (CUF) criterion
- Recommends break postulation when CUF 0.1
- Stakeholder feedback regarding CUF criterion
- May be overly conservative
- Lacking a documented technical basis
- Undue regulatory burden?
- Proposed alternative: EPRI report 1022873 risk-informed approach Publicly available 3
History of Stakeholder Feedback
- Environmentally-assisted fatigue public meeting on January 2012
- Meeting summary available at ML120120028
- EPRI presented on Technical Report 1022873
- NRC staff stated that revising the criterion was not necessary
- User Need Request on HELB
- Examine or develop a technical basis for the CUF criterion
- Delayed, looking forward to completion of Extremely Low Probability of Rupture (xLPR) code
- NRO/NRR wrote a second joint user need on this issue
- Examine technical basis for the CUF criterion; perhaps, update the criterion
- Examine technical basis of jet force models in SRP 3.6.2 4
HELB Technical Letter Report
- Office of Research drafted a technical letter report on BTP 3-4
- Work on the report was assigned a low priority by NRC management in 2017
- Environmentally-assisted fatigue public meeting in September 2018
- Meeting summary available at ML18289A322
- EPRI again requested that NRC re-examine the CUF criterion
- NRC agreed to publish the technical letter report
- Todays public meeting 5
Current Status
- NRC technical letter report on BTP 3-4
- Draft completed
- In concurrence for publication
- Likely published by the end of July
- Todays discussion
- Summary of the NRC technical letter report
- Summary of EPRI Technical Report
- Discussion of NRC comments on the report
- Discussion of industry impacts and next steps 6
Summary of Technical Letter Report
- Summarizes current guidelines 7
Section of BTP 3-4 Criteria Notes Class 1 Piping B.1.(ii)(1)(a)
If Sn > 2.4Sm, then Se > 2.4Sm or Sn >
2.4Sm See Equations 2, 3, and 4.
B.1.(ii)(1)(b)
Cumulative Usage Factor (CUF) 0.1 In 2016, the NRC staff added, For new reactor design certification reviews, the staff has considered a CUF limit of 0.4 to be acceptable when the effects of environmental assited fatigue (EAF) are considered in the piping design.
B.1.(ii)(1)(c)
S > 2.25Sm or S > 1.8Sy BTP 3-4 provides exceptions to these criteria for the loads associated with pipe failure outside containment.
See Equation 1.
Class 2 Piping B.1.(ii)(1)(d)
S + Sn > 0.8(1.8Sh + SA)
Sh and SA are allowable stresses defined in ASME Section III, paragraph NC-3600 [11].
See Equations 1 and 2.
B.1.(ii)(1)(e)
S > 2.25Sh or S>1.8Sy See Equation 1.
The same exceptions discussed in B.1.(ii)(1)(c) apply here.
Summary of Technical Letter Report
- Summarizes historical development of BTP 3-4
- 1972 Giambusso Letter (see BTP 3-3)
- 1973 OLeary Letter (see BTP 3-3)
- Revision history 8
Summary of Technical Letter Report
- Summarizes historical development of BTP 3-4 9
Section in BTP 3-4, Rev. 3 MEB 3-1, Rev. 0 MEB 3-1, Rev. 1 MEB 3-1, Rev. 2 BTP 3-4, Rev. 2 BTP 3-4, Rev. 3 Section A: Background Relatively short introduction Expanded Background section Added a discussion of pipe failures occurring at high stress and fatigue locations No change No change No change B.1(ii)(1)(a)-(b) if 2.4Sm < Sn 3Sm, then CUF 0.1 if Sn > 3Sm, then Se > 2.4Sm and Sn >2.4Sm and CUF 0.1 if Sn > 2.4Sm, then Se > 2.4Sm and Sn >2.4Sm CUF 0.1 No change No change Added statement concerning CUF when EAF is considered in design certification applications B.1(ii)(1)(c)
S > 2.25Sm No change S > min(2.25Sm, 1.8Sy)
S > 2.25Sm and S > 1.8Sy No change B.1(ii)(1)(d)
S+Sn > 0.8(1.2Sh + SA)
No change S+Sn > 0.8(1.8Sh+SA)
No change No change B.1(ii)(1)(e)
S > 1.8Sh No change S > min(2.25Sh, 1.8Sy)
S > 2.25Sh and S > 1.8Sy No change B.1(iii)(1)(a)
B.1(iii)(2)(a)
At terminal ends for Class 2 and 3 piping and non-Class piping enclosed in protective structures or located adjacent to protective structures Extended to Class 1 piping Removed caveat on protective structures Essentially, no changes were made.
Recommendations for non-Class piping now refer to Class 2 and 3 recommendations Clarified the discussion of non-Class piping to apply to seismically analyzed non-ASME Class piping.
No change
Summary of Technical Letter Report
- Discussion of the CUF criterion itself
- What is known about the basis?
- What alternative approaches are out there?
- Rodabaugh letter (see ML18284A024)
- EPRI Technical Report
- Gosselin and Simonen (International Conference on Nuclear Engineering 20-54534)
- Recommendation to develop and document a technical basis for the CUF criterion, including revising if appropriate 10