ML13170A130

Public Slide - NFPA 805 Transient Combustible Controls

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

VCSNS Transient Controls

• 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)

VCS Transient Controls

• 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