ML20282A278
| ML20282A278 | |
| Person / Time | |
|---|---|
| Issue date: | 10/08/2020 |
| From: | O'Brien K NRC/RGN-III |
| To: | |
| Govan T | |
| References | |
| Download: ML20282A278 (13) | |
Text
Nuclear Energy Institutes Proposals to Apply Risk-Insights to 10 CFR 50.59 Kenneth OBrien Deputy Regional Administrator, Region III Nuclear Regulatory Commission October 8, 2020
Purpose & Agenda
- NRC - Provide feedback on the Nuclear Energy Institute's (NEIs)
August 5, 2020 public meeting presentation
- NEI - Present Focus Area #3
- Agenda
- 12:00pm - 12:10pm Opening Comments/Introductions
- 12:10pm - 12:20pm NRC Presentation
- 12:20pm - 12:45pm NRC Working Group (WG) & NEI/Industry Discussion
- 12:45pm - 1:00pm NEI Presentation
- 1:00pm - 1:40pm NRC WG & NEI/Industry Discussion
- 1:40pm - 1:50pm Stakeholder Participation
- 1:50pm - 2:00pm Actions Documented/Closing Remarks 2
Focus Area #1 More than Minimal Concept
- NRC agrees with NEIs assessment:
- Opportunities exist to clarify how to apply risk insights to criteria (i) and (ii);
and
- A change from one frequency category to a more frequent category is an example of a change that results in more than a minimal increase 3
Focus Area #1 (Contd)
- NRC staff believes that:
- Core damage frequency (CDF) and large early release frequency (LERF) cannot alone be an acceptable measure to determine if a proposed change to a facility represents a more than minimal increase 4
Focus Area #1 (Contd)
- In the 1999 Statement of Considerations, the Commission stated that the use of probabilistic risk assessment (PRA) (e.g., CDF and LERF alone) in 50.59 requires further rulemaking
- Staff position:
- Changes, tests, or experiments may prompt changes to PRA inputs;
- The resultant PRA inputs may offset each other; and
- The resultant CDF and/or LERF may not reflect all changes being made which does not meet the requirements of 50.59.
5
Focus Area #1 (Contd)
- Staff agrees with NEI - there are certain PRA techniques that are aligned with the 1999 Statement of Considerations
- PRA techniques can be used to inform criteria (i) and (ii) evaluations.
- Examples may include:
- Failure Modes and Effects Analysis;
- Fault Trees;
- Event Trees;
- Dose Assessment Methods; and
- Consequence Analysis Methods.
6
Focus Area #1 (Contd)
- NRC staff has the following question for NEI:
- What is meant by "Other criteria based upon risk insights..."?
- Slide 20 of NEI's August 5, 2020 presentation 7
Focus Area #2 General Design Criteria (GDC) Language
- NEI stated on August 5, 2020:
- PRA tools [techniques] may be appropriately used to justify acceptance of proposed changes while remaining consistent with the GDCs
- NRC staff has the following questions for NEI:
- How would the use of PRA tools [techniques] ensure continued alignment with the licensing bases?
- What criteria would be used to ensure changes to structures, systems, and components (SSCs),
processes, and procedures remain consistent with the licensing bases?
8
Focus Area #2 (contd)
- NEI stated on August 5, 2020:
- Some GDCs have absolute requirements (e.g. GDC-19) whereas others have flexibility in their requirements (e.g.
designed with appropriate margin, appropriate controls, high probability)
- NRC staff has the following questions:
- What measures would be used to preserve the design aspects of the licensing bases, such as ASME codes, vendor design standard, etc.?
- What criteria would be used to define the terminology presented in the licensing bases associated with some of the GDCs, such as:
- appropriate margin or sufficient margin;
- extremely low probability; and
- acceptably low levels?
9
Focus Area #2 (contd)
- In Example 1, NEI stated on August 5, 2020:
- GDC-2 discusses the design basis for the specified SSCs shall reflect the importance of the safety functions to be performed
- Risk values may be appropriate to quantify the importance of the safety functions to be performed.
- NRC notes:
- The Vogtle Tornado Missile Risk Evaluator (TMRE) methodology was a LAR reviewed and approved by NRC;
- NRC validated the licensees PRA acceptability as part of the LAR approval;
- Methodology applies to as found, legacy conditions; and
- Methodology used RG 1.174, with CDF & LERF as risk metrics.
- Question:
- How does this example demonstrate the ability to use risk values to satisfy compliance with the licensing bases (GDCs) without prior NRC approval?
10
Focus Area #2 (contd)
- Staff agrees with NEIs assessment that risk insights cannot be applied for some GDCs as shown in Example #2 for GDC-19 (Control Room: personnel dose limit) 11
Inspection Manual Chapter (IMC) 0335 Development
- Staff currently drafting a 10 CFR 50.59-related IMC
- Regional comments will be solicited, per standard process
- Draft will be presented in future public meeting to solicit external stakeholder comments
- Implementation, followed by NRC Regional/Headquarter staff training, to occur in 1st Calendar Quarter 2021 12
Path Forward
- NRC and NEI/Industry to continue engaging to resolve issues
- Staff anticipates the next public meeting in November 2020
- NRC to provide feedback on NEIs 10/8 presentation (Focus Area #3 - Methods of Evaluation)
- NEI response to items raised during this meeting
- Presentation of draft IMC 13