ML20265A242
| ML20265A242 | |
| Person / Time | |
|---|---|
| Issue date: | 09/22/2020 |
| From: | Jacqueline Thompson NRC/NRR/DEX/EXHB |
| To: | Nuclear Energy Institute |
| Jenise Thompson 415-7000 | |
| References | |
| Download: ML20265A242 (9) | |
Text
NRC Staff Discussion of Supplemental Information for DG-4028 Volcanic Hazards Assessment for Proposed Nuclear Power Reactor Sites September 22, 2020 Public Meeting with NEI
Topics for Discussion
- Initial screening of volcanic hazards.
- Effects of potential volcanic hazards on the design and operation of proposed nuclear power plants.
- Use of risk insights in the volcanic hazards analysis (VHA).
Initial Screening
- Site characterization [Part 100.23(c)] information in region (320 km) and vicinity (40 km) of site.
- Proximal hazards appear restricted to <40 km of a volcano:
- Debris avalanche, landslide, slope failure
- Volcano-generated missiles
- Gases and aerosols
- Atmospheric phenomena (e.g. lightning),
- Ground deformation
- Hydrothermal systems and groundwater effects
Initial Screening
- Should proximal hazards be screened from the VHA if a site is >40 km from a potential volcanic vent (i.e., new or existing)?
- If deposits from distant (>320 km) Quaternary volcanoes are not present in the site vicinity
(<40 km), is it reasonable to conclude that future deposits from such volcanoes can be screened from the VHA?
Effects of Volcanic Hazards
- Information gap: What levels of volcanic hazards affect the design and operation of a proposed facility?
- Some hazards might be within existing design basis, but many structures, systems, and components (SSCs) have not been evaluated for performance with volcanic hazard demands.
- Some SSCs might be unaffected by some volcanic hazards, but this performance has not been evaluated directly.
Effects of Volcanic Hazards
- Example - what thickness and duration of ash fall affects:
- Plant operations?
- Performance of air and water filtration and circulation systems?
- Electrical systems?
- Other systems?
- Information needed to support screening criteria for significance in a VHA, need for design basis or operator actions.
Risk Insights
- For evaluating risk insights and significance in the VHA, should NRC consider applying event-sequence criteria in NEI 18-04 to volcanic hazards as initiating events:
2 to 10-4 as Design Basis Event (DBE) 4 to 5x10-7 as Beyond Design Basis Event (BDBE)
Risk Insights
- What level of information would be needed to establish the mean frequency of a volcanic hazard early in the VHA?
- In the early stages of a VHA, would information besides a probabilistic risk assessment be available to provide risk insights and screen hazards from a VHA?
Next Steps
- NRC staff will consider supplemental information to better inform revisions in these topical areas
- NRC staff can revise DG-4028 without additional information
- Information might provide more specific criteria in the guidance