ML20212L114

Safety Evaluation Granting Request for Exemption from Technical Requirements of 10CFR50,App R,Section III.G.2.c

ML20212L114
Person / Time
Site:	Arkansas Nuclear
Issue date:	10/01/1999
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20212L066	List: ML20212L062 ML20212L084 ML20212L114
References
NUDOCS 9910070162
Download: ML20212L114 (4)

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• NUCLEAR REGULATORY COMMISSION A" WASHINGTON, D.C. 20555-0001 l

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO APPENDIX R EXEMPTION REQUEST FOR ENTERGY OPERATIONS. INC.

ARKANSAS NUCLEAR ONE. UNIT 2 DOCKET NO. 50-368

1.0 INTRODUCTION

Appendix R," Fire Protection Program for Nuclear Power Facilities Operating Prior to January 1,1979, " to Title 10 of the Code of FederalRegulations (10 CFR), Part 50, establishes fire protection features required to satisfy General Design Criterion 3,' Fire protection," of Appendix A to 10 CFR Part 50 with respect to certain generic issues for nuclear power plants licensed to operate prior to January 1,1979. By letter dated March 22,1983, the staff issued

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an exemption from the technical requirements of Section Ill.G.2 of Appendix R to the extent that it requires an automatic fire suppression system for the area below the 354-foot elevation of the Arkansas Nuclear One, Unit 2 (ANO-2), intake structure. By letter dated October 8,1997, as supplemented by letter dated February 25,1999, Entergy Operations, Inc. (the licensee), for ANO-2, submitted a revised exemption request for this area.

2.0 EXEMPTION REQUESTED The licensee requested an exemption from the technical requirements of Section Ill.G.2 of Appendix R to the extent that it requires an automatic fire suppression system and an automatic fire detection system for the area below the 354 foot elevation of the ANO-2 intake structure.

3.0 DISCUSSION The ANO-2 intake structure is about 32 feet by 26 feet on three levels. There are no rated fire barriers between the three levels. Below the 354-foot elevation there are three intake bays, which contain service water (SW) piping and conduits. The bays are about 7 feet by 32 feet and are separated from one another by 2-foot thick, non-rated concrete walls. The bays are separated from ground level by an 18-inch thick, non-rated concrete slab on metal decking.

The intake bays are typically flooded with water to a depth of about 16 feet. The water is normally provided through a sluice gate. The ceiling height is about 30 feet above the bottom of the bay and about 14 feet above the normal pool level. Access to the intake bays is restricted and is obtained through hatches at the 354 foot elevation.

Redundant post-fire safe shutdown equipment on all levels of the intake structure is limited to equipment associated with the SW system. SW is required to be available to supply cooling water for various safe shutdown components including the diesel generators and the shutdown cooling heat exchangers. In addition, SW can be aligned to the emergency feedwater system if the desired condensate sources become depleted. One flow path is needed to support 9910070162 991001 PDR ADOCK 05000368 l P PM l

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N 2 post-fire safe shutdown. The SW system consists of two independent seismic category I flow paths, which furnish water to two independent trains of 100 percent capacity emergency safety feature equipment, and two nonseismic category I flow paths. The SW system is provided with two dedicated SW pumps (2P4A and 2P4C) and a swing SW pump (2P48) that can be aligned to either of the two flow paths. Each pump provides 100 percent of the required flow for the ,

respective flow path. During plant operations (Modes 1 through 5), the ANO-2 technical specification requires that two SW trains be operable. The possible SW pump alignments are ]

j SW pumps 2P4A and 2P48, SW pumps 2P4A and 2P4C, or SW pumps 2P4C and 2P4B. The power cable arrangements are as follows: conduit EA 1007 contains the red train power supply cable to SW pump 2P4A; conduit EA2036 contains the green train power supply cable to swing  !

SW pump 2P4B; and conduit EA2007 contains the green train power supply cable for SW pump 2P4C. Conduits EA1007 and EA2036 are protected by separate 1-hour fire-rated Hemyc

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fire barriers. Below the 354-foot elevation, these conduits are also encapsulated in a common -

galvanized sheet metal moisture barrier. Conduit EA2007, which is located about 6 feet from the moisture barrier containing conduits EA1007 and EA2036, is covered by a Thermo-Lag barrier. The licensee stated that it does not take credit for the Thermo-Lag barrier to meet the requirements of Appendix R. Conduit EA1008, which contains the red train power supply to swing SW pump 2P48, is embedded in the concrete slab at the elevation of 354 feet and does not enter the bay.

SW bay "A" contains redundant cables required to support post-fire safe shutdown. The licensee stated that the 2P4C/2P48 SW pump combination with SW pump 2P4B aligned to the red train power is the only pump alignment that would be utilized during normal operations in Modes 1 through 5 with SW bay "A" isolated and drained. During the recovery from a fire, the time critical function is to supply cooling water to the diesel generators. The licensee stated that, on the basis of its calculations, the diesel generators (and therefore the SW system components) are not required to be operated during the first 30 minutes of a fire event. The licensee allows the operators to manually align the SW system because sufficient time is available to complete the alignment.

Power and control cables for the sluice gates, which are routed in conduits EB1008, EC1140, EB2008, and EC2132, are also located in the SW intake bays. Sluice gate valves 2CV1470-1, 2CV1472-5, and 2CV1474-2 are normally open, which corresponds to the safe shutdown position. The redundant control cables are separated horizontally by about 8 feet. As stated previously, the time critical function of the SW system is to provide cooling to the diesel generators. The licensee stated that if a fire were to cause the sluice gates to spuriously close, adequate time would be available before service water was required to manually realign any affected component.

The in situ combustible loading below elevation 354 feet of the intake structure is limited to PVC pip!ng and Thermo-Lag fire barrier material. There are no cable trays or exposed cables in the SW bays. The licensee administratively controls access to the bays as confined spaces and foreign material exclusion areas, thus limiting access by personnel durng routine operations and reducing the likelihood that uncontrolled transient combustibles will be introduced into or accumulate in the bays. In addition, the licensee's administrative procedures limit the transient combustibles to 5 pounds unless personnel are conthuously present in the area. In such cases, the personnel could be either the craft personnel responsible for using the combustible

! materials or a continuous fire watch.

r The two upper levels (elevations 354 feet and 366 feet) of the intake structure have flame detectors or ionization smoke detectors and a preaction fire suppression system. Fire protection in SW bay "A" consists of the 1-hour fire-rated Hemyc barriers for conduits EA1007 l and EA2036. Portable fire extinguishers and a fire hose station are available for manual fire fighting.

4.0 EVALUATION l l

i The area below the 354-foot elevation of the ANO-2 intake structure does not meet the technical requirements of Section Ill.G.2.c of Appendix R to 10 CFR Part 50 because, although a 1-hour-rated fire barrier is provided as discussed below, fire detectors and an automatic fire l suppression system are not provided. l The in-situ combustibles in SW bay "A" and the administratively allowed quantity of transient l combustibles (5 pounds) do not pcse a credible fire threat to the SW pump cables. In the staff's view, a fire involving transient combustibles in excess of the administratively allowed i quantity is the only type of fire that could damage redundant SW pump power cables. The l licensee has addressed this threat by protecting both the red train power supply cable for GW pump 2P4A and the green train power supply cable for swing SW pump 2P4B with 1-hour i fire rated barriers, by embedding the red train power supp;y cable for SW swing pump 2P4B in concrete which provides an equivalent 1-hour-rated fire barrier, and by administratively requiring the presence of craft personnel or a fire watch, if the administrative transient combustible limit is exceeded.

A fire involving transient combustibles could be extinguished by the craft personnel or the fire watch during its incipient stage, in the event the fire grows beyond the incipient stage before it is extinguished, the craft personnel or the fire watch could summon the plant fire brigade. In addition, the smoke and hot gases would be directed upwards into the higher elevations of the intake structure, which are equipped with an automatic fire detection system. Therefore,in the event that a fire in the intake bay is not discovered by the craft personral or the fire watch, it would be detected by the automatic fire detection system and the plant t;e brigade would be dispatched. If the fire exposes the redundant conduits, the 1-hour fire-rated barriers and the concrete embedding would provide fire resistive protection, with margin, for the expected fire hazards and, therefore, provide reasonable assurance that the power cables would not be damaged before the fire either burns itself out or is extinguished by the craft personnel, the fire watch, or the fire brigade. On this basis, the staff concludes that the existing fire protection design features, coupled with the administrative controls, provide reasonable assurance that a fire in SW bay "A" would not damage the redundant SW pump power cables and, therefore, would not adversely affect the ability to achieve and maintain post-fire safe shutdown. The staff also concludes that the installation of fire detectors and an automatic fire suppression system in the area below the 354-foot elevation of the ANO-2.nta. ./.. cu:c ',ou;d not result in a significant increase in the level of fire safety for the redundant SW pumps.

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5.0 CONCLUSION

The underlying purpose of Section lil.G.2 of Appendix R is to provide reasonable assurance that at least'one means of achieving and maintaining safe shutdown conditions will remain

. available during and after any postulated fire in the plant. On the basis of its review ano

! evaluation, the staff concludes that fire detectors and an automatic fire suppression system are not needed to satisfy the underlying purpose of Section Ill.G.2.c of Appendix R to 10 CFR Part 50 for the area below the 354-foot elevation of the ANO-2 intake structure, and that there I

would be no undue risk to public health and safety. The licensee's request for an exemption from the technical requirements of Section Ill G.2.c of Appendix R for this area should, therefore, be granted.

l L Principal Contributor: J. A. Holmes Date: October 1, 1999 l

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