05000440/FIN-2010006-02
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Finding | |
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| Title | Diesel Generator Rooms Fire Protection System Concern |
| Description | The inspectors reviewed Engineering Change Package (ECP) 05-0229-01, Division 1, 2, and 3 Diesel Generator Room Carbon Dioxide (CO2) Fire Suppression System Upgrade. The results of that review showed that the licensee modified the DG rooms CO2 fire suppression system to utilize a cross-zoned heat detector layout. The DG rooms cross-zoned heat detector layout changed the actuation logic that discharges the DG rooms CO2 fire suppression system. The systems actuation logic was modified from requiring a single heat detector output that generated the CO2 suppression actuation signal to cross-zoned (e.g., multiple) heat detectors located in different heat detector circuits which required a heat detector output from each circuit to generate a CO2 suppression actuation signal. The CO2 suppression actuation signal is used to discharge the DG rooms CO2 fire suppression system. In addition, the setpoint for the heat detectors was changed from 190 degrees () Fahrenheit (F) to 275F. The inspectors reviewed the plants license bases and amendment documents to determine the as built configuration for the Division 1, 2 and 3 DG rooms CO2 fire suppression system. The inspectors review concluded that the cross-zoned heat detector installation was redesigned from the original heat detector installation that was reviewed and approved by the NRC (i.e., the authority having jurisdiction). Based on the inspectors review of the licensees fire protection codes of record, the National Fire Protection Association (NFPA) 12, Standard on Carbon Dioxide Extinguishing Systems, Revision 1974 and NFPA 72, National Fire Alarm and Signaling Code, Revision 1974), the inspectors determined that the NFPA codes of record provided no information regarding the use of cross-zoned heat detectors. The definition of Cross-zoning is the application of two detectors/sensors where one would usually suffice - in other words, the detection area of each smoke detector is degraded by 50 percent. In this application both detectors must discern a legitimate fire/smoke signature in order to set the system into alarm [/ actuation].6 The inspectors were concerned that the redesigned cross-zoned heat detector layout and subsequent CO2 fire suppression systems actuation logic change did not meet the licensees codes of record for detector spacing requirements and introduced design changes that required the NRCs review and approval prior to installation. This was based on the following inspectors concerns: The inspectors questioned the licensees detector spacing adherence to NFPA 72E - 1974, in that the NFPA codes spacing requirement for smooth ceilings read: All points on the ceiling shall have a detector within a distance equal to or less than 0.7 times the listed spacing (0.7S). With the redesigned cross-zoned heat detector layout and subsequent CO2 fire suppression systems actuation logic change, the cross-zoned heat detector layout required two heat detectors to take the place of one heat detector. Since the two heat detectors, which were located in different detector circuits, were required to take the place of one heat detector, not all points on the ceiling were covered by the two heat detectors (e.g., the inspectors initial interpretation of the licensees code of record indicated that there was a 30 percent reduction in the ceiling area coverage based on the heat detector spacing requirements specified by the NFPA code). The cross-zoned heat detector layout and subsequent CO2 fire suppression systems actuation logic change introduced an inherent heat detector time delay through the cross-zoned method that was not formally evaluated by the licensee. The licensee used engineering judgment in preference to appropriate fire modeling. The licensee did not believe that there was a significant delay introduced through the redesign cross-zoned heat detectors. The licensees design review did not include considerations for ceiling heights of 26 feet. The licensee did not evaluate the impact of higher temperature setpoints upon actuation of the heat detectors. The inspectors performed calculations to determine what size of fire would be required to activate the heat detectors for CO2 activation based on a floor fire located three feet from an east-west wall. The inspectors used the formula for Alperts correlation of ceiling jet temperatures 7 to calculate the impact using the higher temperature setpoints. The inspectors calculations also accounted for the additional distance required to actuate a second detector due to the cross-zoning. The inspectors determined that an approximate 2 megawatt (MW) fire was required to actuate the CO2 system under the original design. A 2 MW fire is roughly equivalent to a diesel fuel oil fire with an area of 12 square feet. With the revised design incorporating cross-zoning and higher detector setpoint temperatures, an approximate 10 MW fire was required to actuate the system. A 10 MW fire is roughly equivalent to a diesel fuel oil fire with an area of 54 square feet. Based on these calculations, the inspectors concluded that the redesign would require a fire that was five times larger than the licensed design to actuate the DG rooms CO2 fire suppression system. As a result, the inspectors were concerned that the cross-zoned heat detector redesign, with the higher temperature setpoint change, created an adverse affect on the DG rooms CO2 fire suppression systems actuation time and would have a potential adverse impact on the licensees fire protection program and/or post-fire safe shutdown analysis. The acceptance testing of the current system designed did not account for the actuation of the system. The inspectors questioned whether the testing approach used for the dual zone installation actually tested the system as-installed. The licensee currently puts a false alarm in for one of the detectors and then used a heat source to actuate another detector in the other zone. The inspectors felt that this was not an adequate means of verifying that the system would detect the heat produced across the zones of influence. The licensee did not obtain, for the redesigned cross-zoned heat detectors and the substantially raised setpoint, ...the approval of the authority having jurisdiction. as required by the NFPA code of record for Approval of Installations, which read: The completed system shall be tested by qualified personnel to meet the approval of the authority having jurisdiction. These tests shall be adequate to determine that the system has been properly installed and will function as intended. Only listed or approved equipment and devices shall be used in the systems. As a result of the redesigned cross-zoned logic, the lack of time delay evaluation, the substantial heat detector temperature increase and the adequacy of acceptance testing, the inspectors were concerned that the DG rooms CO2 fire detection and suppression systems modification (i.e., ECP 05-0229-01) created a potential adverse impact on the licensees fire protection program and/or post-fire safe shutdown analysis. Therefore, prior approval from the NRC as the authority having jurisdiction may be required. In response to the inspectors concerns, the licensee initiated CR 10-79208, NRC ID 50.59: Submittal of the DG Room Detector Changes to NRC for Review, dated July 1, 2010, and CR 10-79210, NRC ID 50.59. Cross-Zone Heat Detector Layout, dated July 1, 2010. This issue will be considered a URI to obtain a more thorough review of the suppression system design and the plants license basis to determine if prior NRC approval was necessary for installation of this system. |
| Site: | Perry  |
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| Report | IR 05000440/2010006 Section 4OA5 |
| Date counted | Sep 30, 2010 (2010Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | |
| Inspectors (proximate) | Z Falevits R Daley R Langstaff G Hausman L Jones |
| INPO aspect | |
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Finding - Perry - IR 05000440/2010006 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Perry) @ 2010Q3
Self-Identified List (Perry)
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