Seismic Fire Interactions (Task 13)

Task Overview

Background

This task is a qualitative approach to help identify the risk from any potential interactions between an earthquake and fire.

Purpose

The Fire Risk Scoping Study [13.1] identified the following four seismic-fire interaction issues:

• Seismically induced fires
• Degradation of fire suppression systems and features
• Spurious actuation of suppression and/or detection systems
• Degradation of manual firefighting effectiveness

It is recommended that a Fire PRA include a qualitative assessment of these issues. In this procedure, a recommended approach is given.

This procedure does not provide a methodology for developing models and quantifying risk associated with fires caused by a severe seismic event. This is due to a combination of limitations in the state of the art, and the perceived low level of risk from these fires. The low risk is based on the low frequency of an earthquake that can initiate a challenging fire and degrade various plant fire protection defense-in-depth elements, and the general seismic ruggedness of the NPPs as part of their design basis. This procedure outlines a series of steps intended to verify this premise. If the verification steps outlined in this procedure do not preclude the risk significance, either a quantitative assessment or consideration of physical or procedural changes may follow.

Scope

Consistent with the recommendations of Reference 13.1 and those outlined in the EPRI FIVE [TR-100370 (no longer available on epri.com)] and EPRI's Fire PRA Implementation Guide [TR-105928 (no longer available on epri.com)], recommended practice in the seismic fire interactions assessment utilizes a qualitative, walkdown-based approach, rather than quantitative methods to estimated associated risk. This task provides a stand-alone study of the effects of a fire due to an earthquake. This task is not intended to develop quantitative estimates of the risk associated with seismic-fire interactions.

Related Element of ASME/ANS PRA Standard

Seismic Fire (SF)

Related EPRI 1011989 NUREG/CR-6850 Appendices

None

Supplemental Guidance

Although there are no requirements to quantify seismic fire risk in Part 4 (Fire) of the ASME/ANS PRA Standard, Part 5 of the ASME/ANS PRA Standard (Seismic) does require that seismically induced initiating events caused by secondary hazards (including seismic induced internal fires) are identified, that fragilities are estimated for credible seismic induced fire sources, and that seismic induced fire scenarios are included in the seismic PRA model as necessary. EPRI 3002012980 provides a methodology to treat seismically induced internal fires (and internal floods) in a seismic PRA.

References

1. Fire Risk Scoping Study: Investigation of Nuclear Power Plant Fire Risk, Including Previously Unaddressed Issues, NUREG/CR-5088)