ML20203B445
| ML20203B445 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 02/06/1998 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20203B421 | List: |
| References | |
| NUDOCS 9802240288 | |
| Download: ML20203B445 (5) | |
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UNITED STATES y*
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NUCLEAR REGULATORY COMMISSION WAWHINGToN, D.C. 30u6-0001 o%
m SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION i
RELATED TO AMENDMENT NO 191 TO FAQlLITY OPERATING LICENSE NO. DPR 71 AND AMENDMENT NO 222 TO FACILITY OPERATING LICENSE NO. DPR-82 CAROLINA POWER & LIGHT COMPANY BRUNSWICK STEAM ELECTRIC PLANT. UNITS 1 AND 2 DOCKET NOS. 50-325 AND 50-324
1.0 INTRODUCTION
In a letter dated November 6,1997, as supplemented by letter dated January 28,1998, Carolina Power and Light Company (CPL), the licensee for the Brunswick Steam Electric Plant (BSEP) Units 1 and 2, submitted a request for license amendrnents. Based upon use of certain compensatory actions to assure accomplishment of design basis functions, the proposed amendments revise, for a limited period of time, the design basis qualification for the Control Room Emm -icy Ventilation System (CREVS) and CREV3 instrumentation. The proposed changes were requested to support modifications to upgrade the Control Room Air Conditioning (AC) equipment and some supporting components. The Control Room AC system !s required to prevent the failure of safety-related equipment and to ensure Control Room habhability following certain design basis events. The planned modifications will affect the seismic integ-ity of the Control Room envelape and cannot be completed within the allowed outage times specified in the Technical Specifications (TS). Without approval of the proposed license amendments, implementation of the Control Room upgrades would require shutting down both BSEP units. The amendment provides for the use of temporary AC equipment and ductwork barriers which do not fully meet the design basis for CREVS for certain external events (e.g.,
earthquakes, tomadoes and hurricanes, radiologier/ sabotage and missile hazards),
Compensatory actions will be taken to minimize the risk under the temporary amendment and assure necessary functions can be accomplished. The change to the TS for the CREVS is for one-time use and will not be used aftc May 1,1998, 2.0 DISCUSSION AND EVALUATION During a selfJnitiated safety system functionalinspection of the Control Building heating and ventilation and AC system, the licensee determined that the analysis which served as the basis for the non-safety-related, seismic classification for the Control Room AC system contained some assumptions that could not be supported by the current plant configuration. Analysis demonstrated that the operation of the Control Room AC system is requireo to prevent failure of safety-related equipment following certain design basis events in combination with credible single failures and should be classified as safety related. CP&L decided to replace the AC system condensing units with new units and to make modifications stemming from the 90022^0288 900206 ADOCK0500g4 DR
2 Unresolved Safety issur,'USI) A 46 program (" Seismic Adequacy of Machanical and Electrical Equipment"). The Control Room AC system consists of a large volume recirculation system, which discharges air from the Control Room, filters the air, adds a small percentage of outdoor air, cools or heats the air, and returns the air to the Control Room. The motive force for the recirculation is provided by three fans, two of which are normally in operation and one of which is a standby. There are three evaporative coils in the ductwork on the suction side of the fans and three condensing units. A fan, evaporative coll. and condensing unit constitute a set and there is no cross over capability between sets.
When the CREVS is to be used for a radiation release or a smoke emergency, the normal air intake isolates and the CREVS provides a source of outdoor air that passes through particulate and charcoal filters. In the event of a toxic gas (chlorine) release only the recirculation system is in service. The CREVS shuts down and all the outdoor air intake terminates.
The supply fans and the ductwork containing the evaporative coils form part of the pressure boundary for the Control Room envelope during radiation, smoke, or toxic gas events. The ductwork that forms part of the Control Room pressure boundary is designed and constructed to seismic criteria. The ductwork is housed in a seismically designed, tornado-proof structure with engineered features for protection from natural phenomena.
Breaching the ductwork is required as part of the Control Room AC system upgrade and for the USl A-46 work. A temporary non seismically qualified barrier will be constructed to preserve the leakage characteristics of the Control Room pressure boundarf. Thit. portion of the work will require up to 16 days to complete.
While the condensing units are out of service, temporary condensing units located on the roof, outside the Vital Area but inside the Protected Area, will be used. During this time the Control Room AC system will not be protected from certain external events, as specified by the system design and licensing bases. The temporary condensing units will be required for up to nine weeks.
A breach of the ductwork at the suction side of the supply fans due to a seismic event will prohibit isolation from outside air sources, increasing the unfiltered in leakage to an amount in excess of that used in the analyses. There is no permanent isolation capability for this portion of the ductwork.
The Bases for the CREVS TS (TS 3.7.2) and the Updated Final Safety Analysis Report (UFSAR)in Section 6.4 require that the system ensure the habitability of the Control Room during normal operation and postulated natural phenomena, environmental and missile hazards and events requiring physical protection of vital equipment. While the modification is being implemer,ted in the ductwork, the seismic integrity of the ductwork will not be assured. Also, the temporary condensing units on the roof and piping which connect them to the evaporative coils will not be seismically qualified, protected from severe natural phenomena, or physically protected from radiological sabatoge.
CP&L has proposed modifying TS 3.7.2 by the addition of footnote *" which redefines the definition of Operability for the CREVS system. The definition states "The Control Room
3 Emergency Ventilation System (CREVS) ductwork may be considered OPERABLE, for one or moie periods totaling up to 16 days, using temporary ductwork barriers constructed to preserve the leakage characteristics of the control room pressure boundary under normal operational conditions, during the implementation of the Control Room Alr Conditioning System replacement modification. The chlorine tank car shall be removed from the exclusion area while temporary ductwork barriers are being used. The CREVS may also be considered OPERABLE up to nine weeks with temporary condensing units and associated piping and controls installed. Two of these units shall be functional dsring normal operational conditions.
This is applicable during the time period January 30 %
- o May 1,1998. In this configuration, the system is not considered to be in an ACTION stL
.9t for the purposes of Technical Specification 3.0.4."
CPL has proposed modifying TS 3.3.5.5, which addresses CREVS instrumentation, by the addition of footnote
- which r3 defines the definition of Operability for the CREVS instrumentation. The definition states 'The Control Room Emergency Ventilation System i
(CREVS) instrumentation may be considered OPERABLE, consistent with the conditions l
specified in footnote *" to Technical Specification 3.7.2, during the time period from January 30,1998, to May 1,1998. In this configuration the CREVS instrumentation is not considered to be in an ACTION statement for the purposes of Technical Specification 3.0.4.*
The licensee provided the following justifications for the temporary one time changes:
During the poltion of the modifications that affect the ductwork at the evaporative coils, the ductwork snd coils will not be seismically qualified, if the ductwork should fall during a seismic event, there will be a reduction in the cooling capacity of the system. Also, the temporary condensing units to be erected outside the Control Building will not be seismically qualified nor will they be protected from high winds or tornado missiles. This work is planned to take place in the Winter and early Spring, when reliance on the AC systam is minimal due to lower outdoor temperatures than at other times of the year. In the unlikely event of a Design Basis Earthquake (DBE) during the nine weeks that the temporary condensing units will tm used, the temperature of the Control Room would be maintained by opening doors and increasing the ventilation rate. Additional measures to provide temporary Control Room cooling will be established prior to beginning the upgrades to the Control Room AC system.
The timo during which the temporary barrier in the ductwork is required is relatively short (i.e., a total of 16 days). Since the existing barriers to release of significant amounts of radioactive material are saismically qualified, the probability of a seismic event and a significant radioactive material release occurring simultaneously is extremely small and is not part of the design basis for the BSEP, (Nonetheless) Radiation events or offsite fires [ producing smoke] resulting from a seismic event can be postulated as a hazard to Control Room personnel. If [sc;h) hazardous conditions exist, Control Room personnel would don self contained breathing apparatus (SCBA)
A temporary barrier will be erected in the duct upstream of the fan being worked. The leakage characteristics of the portion of the duct stillin service will be similar to the permanently erected duct. The temporary barriers will be constructed to provide m
4 integrity of the duct during design basis radiation release events.
In the tsvent of a radiation or toxic gas release or smoke emergency, not combined with severe natural phenomena, the habitability of the Control Room will be maintained. The erection of the barrier in esch duct will be accomplished within the 12 hour1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> allowed outage time currently provided by the TS for shutdown of BSEP, Units 1 and 2.
The only toxic gas threat to the habitability of the Control Room is fro:.1 the chlorine gas.
With tne cool sea water temperatures in February and March, chlorination can be interrupted for this period without extensive biofouling of the Service Water and Circulating Water systems. The chlorine tank car will be removed from the site while the temporary barriers are used.
The temporary measures to cool the Control Room would violate the Control Room pressure boundary The analysis for the complete rupture of the chlorine car shows that the cloud, including tne liquid spill, dissipates to below levels of concern in less than three hours. The temporary cooling measures can be delayed by this amount of time without damage or affecting the operability of Cor. trol Room equipment. If a chlorine system break were to occur in conjunction with a seismic event and resulted in the need l
to use temporary measures for Control Room cooling, the Control Room operators could don SCBA.
l The temporary condensing units will be mounted on the roof of the Control Building in an area that is provideo with sufficient drainage such that flooding is not a concern. The condensing units will be elevated such that components whose operation may be affected by heavy rains will be a minimum of 6 inches above the roof surface. In the evant of snow or ice build-up at the temporary condenNg units there will be sufficient time available to take action to clear any blockage and restore the units.
While hot work is being conducted in the area of the condensing units, a continuous fire watch will be maintained. Periodic operator rounds will be used to monitor the temporary cooling units when hot work is not being performed.
The licensee has performed an analysis of the temperature rise in the control room, under 6pringtime temperature conditions, in the event of loss of the AC condensing units with CREVS Integrity remaining in tact. It shows that control room temperature would remain below 100'F for a period of 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br />. This would allow adequate time for dissipation of chlorine gas, plant shutdown (Hot Shutdown), and implementation of alternative cooling measures.
An adequate suppy of SCBAs is available to operators should CREVS integrity be lost due to a seismic event, potentially resultbg in a radiological releast or fires offsite, or coincident with a l
toxic gas re aase. The plant has an SCBA refill system and a procedure for operation of that system. Backup refill capability is available by means of compressors located at a nearby fire department. Operators are trained and qualified in the use of this equipment. Plant procedures require that ope,ators don SCBAs in the event chlorine is detected in the control room.
Procedures also require periodic inventory and inspections of SCBAs. Prior te the commencement of the subject CREVS modifications, one operations crew will participate in an
5 exercise scenario on the plant simulator while wearing SCBAs. Any lessons learned from that exercise will be provided to each operating crew.
2.8 Results Of Staff Review The BSEP licensee proposed license amendments to revise, for a limited period of time, the design basis qualification for the CREVS and the CREVS instrumentation. The proposed i
changes were requested to support modifications to upgrade the Control Room AC equipment and some supporting components. The Control Room AC system is required to prevent the failure of safety-related equipment and to ensure Contrcl Room habitability following certain design baals events. The planned modifications will affect the seismic integrity of the Control Room envelope and cannot be completed within the allowed outage times specified in the Technical Specifications (TS). Without approval of the proposed license amendments, implementation of the Control Room AC upgrade would require shutting down both of the BSEP j
units. The amendments provide for the use of temporary AC equipment and ductwork barriers which do ot fully meet the design basis for certain extemal events (e.g., earthquakes, tornadoes.nd hurricanes, radiological sabotage and missile hazards), Compensatory actions will be taken to minimize the risk under the temporary amendments and ensure design basis functions can be accomplished, and the change to the TS for the CREVS is for one-time use and will not be used after May 1,1998. The proposed temporary changes do not affect any component or any of the barriers to radiation release, any of the systems which protect the core from overheating, or any system used to shut down the reactor. The proposed changes do not affect the chlorination system piping or the tank car, which would be initiating components of a chlorine release event. The licensee has analyzed the acrease in risk due to the temporary modification of the CREVS and fosod that the increase it the probability of a radiological release would be insignificant.
The staff has reviewed the licensee's proposed temporary amendments and the proposed compensatory actions. The staff concludes that the proposed compensating actions provide reasonable assurance that these one time temporary arnendments will not affect the integrity of the reactor coolant pressure boundary, the capability to shut down the reactor and maintain it in a shutdown condition or the capabluty to prevent or mi'.igate the conrequences of accidents which could result in potential offsite exposures comparable to the exposures of 10 CFR Part 100 in the event of natural phenomena (General Denign Criterion 2) such as earthquakes, hurricanes, tornadoes, wind generated missiles or heavy rain. Additionally the staff concludes that, with the compensatory actions proposed by the licensee, adequate radiation protection will be provided to Control Room personnel under ace! dent conditions (General Design Criterion 19).
3.0 STATE CONSULTATION
in accordance with the Commission's reputations, the State of North Carolina official was notified of the proposed issuance of the ai andments. The State official had no comments.
4.0 ENVIRONMENTAL CONSIDERATION
These amendments involve a change in the installation or use of a facility component located
.