ML20209A411
| ML20209A411 | |
| Person / Time | |
|---|---|
| Issue date: | 07/27/2020 |
| From: | Stephen Dinsmore NRC/NRR/DRA/APLA |
| To: | |
| Dinsmore, Stephen | |
| References | |
| Download: ML20209A411 (7) | |
Text
FLEX in Risk-Informed licensing action Stephen Dinsmore Senior Reliability and Risk Analyst NRR/DRA/APLA 1
Documents related to submittal and review guidelines for FLEX Equipment
- NEI 16-06, Crediting Mitigating Strategies in Risk-Informed Decision Making, August 26, 2016
- Assessment of the Nuclear Energy Institute 16-06, Crediting Mitigating Strategies in Risk-Informed Decision Making, Guidance for Risk-Informed Changes to Plants Licensing basis May 30, 2017 (ML17031A269)
- Human Reliability Analysis (HRA) for Diverse and Flexible Mitigation Strategies (FLEX) and Use of Portable Equipment, EPRI-3002013018, November 2018
- NRC Regulatory Audit summary, Operational data, June 10, 2020 (ML20155K827) 2
- becoming more frequent and with greater credit
- the staff has started always asking how FLEX is credited 3
Identified FLEX Modelling Issues -
Human Errors
- Human Error Probabilities for Deployment (identifying, locating, transporting, and installing)
- Permanently installed equipment - not an issue
- Portable equipment - human actions may be outside of current HEP methodologies
- Human Error Probabilities for Execution (alignment, activation, and operation)
- Permanently installed equipment - assumed to be similar to alternative uses of current equipment (e.g., align fire fighting systems to LPSI)
- Portable equipment - currently assumed to be similar to alternative uses of current equipment 4
Identified FLEX Modelling Issues -
Equipment Failure Data
- Failure rates/demand probabilities of portable equipment is not believed to be the same as current equipment, most likely greater
- Observed data - far less observed data available and the data which is available may be difficult to interpret
- Factor increase method - use of factors to increase failure parameters is simple but generally appears to be used to avoid technical defensible justification 5
- If fixed FLEX equipment is credited, limited additional evaluation
- If deployable FLEX equipment is credited (key source of uncertainty)
- RAIs about impact on the decision
- If important may request details of equipment and deployment
- If important usually request sensitivity studies on both HEPs and equipment failure parameters
- If sensitivity studies confirms importance, may request the sensitivity studies become part of the application implementation
- Generally accepted guidance needed to replace RAIs 6
Next Steps
- Equipment Failure Data
- PWROG issued a draft report on FLEX equipment failure rates
- NRC audited the draft report and issued an audit report with observations and concerns
- Final PWROG report expected this summer
- IDHEAS-ECA evaluation and data reports will be issued in August.
- FLEX Summit (first 2 weeks of September)
- Opportunity to discuss resolution of open items related to crediting FLEX 7