ML13170A130
| ML13170A130 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 06/18/2013 |
| From: | South Carolina Electric & Gas Co |
| To: | Ellen Brown Plant Licensing Branch II |
| Brown E NRR/DORL/LPL2-1 | |
| References | |
| TAC ME7586 | |
| Download: ML13170A130 (18) | |
Text
NFPA 805 Transient Combustible Controls V. C. Summer Nuclear Tom Keckeisen, Operations-Fire Protection
PURPOSE
- Provide an Overview of the Executive Summary
- Describe the Process for the Control of Transient Combustibles and Ignition Sources
- Specifically address Controls in Areas with Performance-Based Fire Modeling
Objective
- Goal is to maintain a program consistent with NFPA 805 requirements and its supporting documentation and calculations
- NFPA 805 Section 3.3.1.2, Control of Combustible Materials
- NFPA 805 Section 3.3.1.3, Control of Ignition Sources
- Controls to be based on risk by assigning combustible control levels based on the Fire PRA and performance based insights.
- Developing an Engineering calculation to define fire zone PRA CDF sensitivity to transients.
- Controls levels defined by consensus between Fire Protection and PRA engineers.
- Industry is developing a white paper on the general transient combustible/ignition source process.
Assignment of Control Levels
- Level of controls will range from Low (Level 4) to High (Level 1)
- Level 4: Fire Zones with low risk contribution. Fire PRA assumes full compartment burn and zones are not sensitive to higher transient influence factors
(~130 Fire Zones)
- Level 3: Level 4 Fire Zones (low risk) which contain specific areas with deterministic fire barriers and /or separation features (i.e. ERFBS or 20 ft separation) (~15 Fire Zones)
Assignment of Control Levels
- Level 2: Fire Zones with higher risk contribution or zones which are sensitive to higher transient factors. Primarily AC/DC distribution and electrical cable chases (~30 Fire Zones).
- Level 1: Fire Zones governed by Performance-Based Fire Modeling or zones where failure to follow transient controls are impacting (6 Fire Zones).
Risk Insights from the Fire PRA
- Full Compartment Burn
-Low Risk Contribution
-No credit for any fire protection feature
-Assigned as Level IV
-Several exceptions to this general assignment of this level
Risk Insights from the Fire PRA
- Fire Size and Location
- Peak Heat Release Rate (HRR) - 317kW
- If Quantity / Type can cause a Peak HRR > 317kW. May not be analyzed in Fire PRA.
- Scenarios governed by limiting fire size to 317kW need to be controlled
Risk Insights from the Fire PRA
- Transient Influence Factors
- Weighting Factors for Transient Ignition Frequencies
- Maintenance / Occupancy / Storage (1-Low, 3-Medium, 10-High)
- Sensitivity Calculation: All factors increased to 10-High
- Fire Zones with Significant Impact (CDF increase >1E-06) are more sensitive to increases in Transient Influence Factors
- Assigned as Level II
Risk Insights from the Fire PRA
- Probability of Failing to Follow Controls
-Fire PRA analyzed two (2) of the Risk Significant Zones assuming a probability of failing to follow combustible controls
-Risk Significant Zones with Low Transient Influence Factors
-Assigned as Level I
Risk Insights from the Fire PRA
- Fire Scenarios with Structural Steel
-Structural Steel Bounding Analysis: Potential fire scenarios involving structural collapse due to thermal damage
-3 Fire Zones meet criteria: Unprotected steel / high in-situ fire source.
- No transient combustible impact -Low Risk
Other NFPA 805 Elements
- Spatial Separation (20 ft.) per NFPA 805, 4.2.3.3 (a)
- Electrical Raceway Fire Barrier Systems (ERFBS) per 4.2.2.2 (c)
- Fire Protection Equivalency Evaluations (FPEEE) - Adequate for the Hazard
VCS Performance Based Fire Modeling
- NFPA 805 4.2.4.1 permits the use of fire modeling for addressing variances from deterministic requirements (VFDRs)
- Applied to Four (4) Fire Areas which have cable tray targets close to the floor
- Fire model specifies administrative controls to be designed and implemented so that fire damage to the targets within the fire zone is prevented.
VCS Performance Based Fire Modeling
- The Four (4) Fire Areas where Performance Based Fire Modeling was used will be considered Level I Areas and have the highest level of control.
- These areas will be treated as restricted areas (i.e. no transient combustibles allowed without FP approval and elevated compensatory actions)
- Level 4: General Housekeeping Controls Apply
- Level 3: General Housekeeping Controls Apply with additional controls for areas with deterministic requirements.
- Level 2: Designated by Fire PRA as Risk Significant.
Controls on quantities, duration, Class B combustibles.
- Level 1: Restricted Area - No Transient Combustibles Allowed without additional evaluation / approval required to ensure fire damage is prevented as documented in fire model.
Implementation
- Transient Combustible Control Procedure
- Plant Housekeeping / Staging / Storage Procedure
- Maintenance Work Area Procedure /
Instruction
- Fire Prevention Inspection Procedures
- Plant Area Designation / Physical Controls
Summary
- Goal is to maintain a program consistent with NFPA 805 requirements and its supporting documentation and calculations
- Provides a Risk Approach to the control of Transient Combustibles and Ignition Sources
- Allows for a more focused controls, inspections, observations in higher risk areas.
- Provides site specific information to support additional risk considerations
Questions or Comments