ML20127K091

Forwards Followup to 930114 Request for Waiver of Compliance W/Ts 3.7.6(a), Control Room Area Ventilation Sys

ML20127K091
Person / Time
Site:	Catawba
Issue date:	01/15/1993
From:	Mccollum W DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9301260036
Download: ML20127K091 (8)

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q$4q DUKEPOWER January 15, 1993 U. S. Nuclear Regulatory 71mmission A1Td: Document Contmi Desk Washington, DC 20555

Subject:

Catawba Nuclear Station Docket Nos. 50-413 and 50-414 <

W'aiver Of Compliance ,

Technical Specification 3,7.6 " Control Room Area Ventilation' System" This letter constitutes written follow-up to the telephone call between Catawba Nuclear Station and NRC pensonnel on January 14, 1993. The purpose of this telephone call was to request a waiver of compliance from Technical Specification (TS) 3.7.6 (a), Control-Room Area Ventilation System.

All written information related to this waiver of ec,mpliance is attached.

The Catawba Nuclear Station Site Management Team reviewed and approved this request for a waiver of compliance on Janua,f 14, 1993.

Very truly yours, flf/f *I W. R. McCollum Catawba Station Manager CRUWAIV.YC

-Attachment 253057 9301260036 930115 PDR ADOCK 05000413 i P PDR

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11. S. Nuclear Regulatory Commission January 15, 1993 j Page 2

xc: S. D. Ebneter Regional Administrator, Region II

! American Nuclear Insurers M & M Nuclear Consultants INPO Records Center W. T. Orders Senior Resident Inspector l

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R. E. Martin, ONRR 1

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1 CATAWBA NUCLEAR STATION

! Request for a Waiver of Compliance

Technical Specification 3.7.6 " Control Room Area Ventilation System" i

l Requirement From Which ReliefIs Sought I - Catawba Nuclear Station is requesting relief from Technical Specification (TS) 3.7.6 (a)..

l This TS requires that two independent Control Reom Area Ventilation Systems be OPERABLE at all times. The associated ACTION statement for Modes 1 through .4 requires that with one Control Room Area Ventilation System inoperable for reasons other j than the filter train heaters, the inoperable system must be mstored to OPERABLE status l within 7 days or be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD .

! SHUTDOWN within the following-30 hours. Catawba is requesting that the 7 days to

! return the inoperable' system be extended by an additional 3 days (for a total of 10 days) from January 18,1993 at 0130 through January 21,1993 at 0130 to allow sufficient time i to repair the B Train Contml Room Area Ventilation System Chiller.

l l Discussion Of Circumstances And Need For Prompt Action I The Control Room Area Ventilation and Air Conditioning Systems (VC/YC) am designed i to maintain the environment in the control room, control room area, and switchgear rooms,

as indicated in Final Safety Analysis Report (FSAR) Figures 9-108 through 9-117, within acceptable limits for the operation of unit controls, for maintenance and testing of the l controir, as requir:d, and for uninterrupted safe occupancy of the control mom during post--

accident shutdown. The control room, and other support areas as shown in FSAR Figures -

9-108 through 9-111 are designed to maintain approximately 74 F and 50- percent l maximum n:lative humidity. The Technical SpeciGcation maximum control mom

! tempemture is 90'F (TS 4.7.6 (a)).

Continuous pressurization of the control room proper is provided to pmvent entry of dust, 4

dirt, smoke, and radioactivity originating outside the precsurized zones. Pressurization is -

maintained slightly positive relative to the pressure outdoors and in surrounding areas.-

The Control Room Area Vendlation System subsystems are each provided with two 100

! -percent caprity trains (Trains A and B). Each meets the single failure criterion. These two trains are shared between Units 1 and 2. If one train fails, indication is provided in 4

the control room. Switchover is accomplished manually by the operator.

On January 11,1993, during a swapover from Train A to Train B of the VC/YC system, the Train B chiller would not start. Troubleshooting' efforts identified anL"x" phase to ground fault in the B Train Chiller compassor motor, i

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@ j f . Work efforts began immediately and work continued around the clock to disassemble and 1 l- remove the compressor motor in order to detennine the cause of the failure. .Once the

, compressor motor was disassembled, it was discovered that a piece of the windage baffle i plate had broken off and shoit circuited the stator. Rotor damage was also observed and j j required replacement. j i

This unforseen failure resuhcd in significant troubleshooting efforts. The motor housing

[ for this chiller functions as the chiller pressure boundary. Because the motor is internal j: to the housing, major disassembly is mquired to conduct the repair effort. A substantial ,

amount of work remains to be completed. ' Also, thomugh post-maintenance testing will

! be required to return the chiller to service. As a result,_it is possible that the remaining

! work will not be completed within the.7 day action statement of Technical Specification

3.7.6 (a). ,

! Discussion Of Why This Situation Could Not Have Been Avoided I The ground fault on the YC Chiller could not_have been avoided. Since declaring YC:

l. Train B inoperable, Catawba has continuously pursued efforts to' identify and repair the

cause of the failure. Failure of a YC chiller motor has not been experienced previously j at Catawba. . Discussion with the chiller manufacturer indicated that the industry has i experienced some cmcking of the windage baffle, but has never experienced complete

! failure of the windage baffle as has occurred at Catawba for this baffle design.

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[ Due to the design of the chiller, it would be extremely difficult to complete a repair effort

[ of this magnitude within 7 days under any circumstance. Had this been a planned mpair l effon, preparatory work could have been completed in advance such that the to.tal scope -

p of work may have been completed within 7 days. In summary, the magnitude of the entire l repair process could not have been auticipated and may not be completed within the 7 days

( allowed by TS 3.7.6.

i Discussion Of Compensatory Actions l -During normal operation _(non-accident conditions), Train A of VC/YC;will _be _ fully L operable and able to maintain the required control area environment and meet the design L basis requirements. If for some reason, Train A of VC/YC were to fail, both Catawba

[ units will enter Technical Specification 3.0.3. If the cause of the failure could not be-L detennined and the train could not be mturned to operation,--both units will be shut down-f and brought to Mode 5 and all applicable Technical Specifications pertaining to having two '

inoperable VC/YC trains will be complied with.

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- In_ addition, the following measures would be implemented, as determined by the Shift

[ Supervisor, to mitigate the effects of the loss of both trains of VC/YC:

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• Opening instrument cabinet doors in the control room to provide increased air flow / cooling inside the cabinets

• Utilizing temporary fans to cool the interior of the cabinets e Maintaining the control room doors in the open position with temporary fans in place (with appropriate security measures) to utilize the computer ama ventilation / chilled water system for control room cooling. The control room doors will be closed in the event of a LOCA or blackout.

• Deenergizing the filter heaters in the VC/YC filter trains

• Utilizing portable coolers to help cool hot spots in the control room, if necessary s

During the period of time that the waiver of compliance is in effect, preparations will be taken so that any temporary equipment required is readily available. This will ensure that the above compensatory measures can be enacted as quickly as possible. Empirical data shows that the control room can be expected to heat up at a mte of appmximately 4

'F/ hour without cooling from VC/YC; therefore, adequate time exists to establish the above compensatory actions.

For accident conditions, the operating train (Train A) of VC/YC would be expected to be fully operable and capable of meeting design basis requirements. If this train wem to fail, the Train B pressurizing filter train and air handling unit would be available to pressurize and filter the control room envimnment. Therefore, the ability to pressurize the control room area would be assured, although normal cooling of the control room would not be available from the VC/YC system. In addition, portions of Train A VC/YC equipment may .still be available for cooling or pressurization of the control room, depending upon

, which Tmin A components were to fail. During LOCA/ Blackout conditions, procedures exist which enable the operators to minimize the heat input into the control room. Also, a procedure exists for swapping the emergency power supply of the operating VC/YC train to the non-blacked out unit's associated train D/G during blackout conditions where the D/G of the blacked out unit does not start. If any control room doors are being maintained open prior to accident conditions, a compensatory action will be invoked to close these doors. All of the other compensatory actions listed above would remain available to mitigate the effects of a control room temperature excursion.

During the period of time that the waiver of compliance is in effect, the following additional measures will be taken:

• Diesel G:nerators l A and 2A will not be removed from service for preplanned maintenance 1

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e Increased monitoring of the A Train of VC/YC will be performed by operations shift personnel

• " Tailgate" meetings will be held with all new shift personnel that come on duty during the waiver period to explain the circumstances that exist regarding VC/YC and the ,

compensatory measures that may be required. The discussion will cover additional measures taken during the waiver period and actions necessary " , Train VC/YC becomes inopemble.

Finally, it should be noted that as a last resort, the auxiliary shutdown panels are available to shut down and control the plant in the event that any vital controls or instmmentation are lost as a msult of unacceptable envimnmental conditions in the control room. Also, the Standby Shutdown Facility (SSF) is available should shutdown from that location be necessary.

Technical Justification As stated in the above discussion of compensatory actions, implementation of the measures described will result in reasonable assurance that adequate envimamental conditions will be maintained in the control mom area following the loss of the remaining train of VC/YC.

This is true for both non-accident and accident conditions. Plant personnel will be fuliy briefed regarding the condition of the VC/YC system and the compensatory actions that

will be taken should the operating train of VC/YC fail. Equipment will be made available so that these compensatory actions can be implemented as quickly as possible.

The Catawba Probabilistic Risk Assessment (PRA) was reviewed to determine the effect of adding 3 days to the allowable outage time for a single VC/YC tmin. The two mort probable unmitigatable design basis events (1dgh energy line break and SBLOCA) wem examined. It was assumed that each of these events were to occur during the 7 or 10 day period while one train of VC/YC is out of service, and further, that the other train of VC/YC were to fail. The incremental difference in the risk between a 7 day exposure to the degraded VC/YC conditions and a 10 day exposure to inese same conditions was determined to be approximately 6E-8 for the high energy line break scenario and approximately SE-8 for the SBLOCA scenario By comparison, the annual com damage frequency for Catawba is on the order of IE-4 per year. Compamd to this value, risks on the order of those predicted for the events postulated above are considered negligible.

No Significant Hazards Analysis T'm change requested under this waiver of compliance does not involve a significant hazards consideration. The following analysis is based on the requirements provided in 10 4

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CFR 50.92 which states that a proposed change involves no significant hazards

! consideration if operation of the facility in accordance with the proposed change would not:

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l) Involve a significant increase in the probability or consequences of an accident l pn

viously evaluated; I

! 2) Create the possibility of a new or different kind' of accident from any accident

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1 l_ 3) Involve a sigrn0 cant r: duction in a margin of safety.

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i This proposed change will not involve a significant; increase .in the probability or i consequences of an accident previously evaluated in the FSAR. A 3 day extension in the j action statement for having one train of VC/YC inoperable will not cause an increase in j the probability of an accident-which has been previously-evaluated because the VC/YC -

system is not an accident initiator.

The consequences of an accident which has been previously evaluated Mill not be

significantly increased by the granting of this waiver. The waiver will have no impact on .

. the dose to members of the public. - Also, the dose to control room area operators will not j- be significantly affected b'y- this waiver, The compensatorj actions available in the event i- _ that the operating train of VC/YC is lost will ensure that at least one train or filtration is

-available to minimize doses in the control room area. No effect on.other plant systems' l requirec. for accident mM lon will occur as a result of this waiver, so no other accident j consequences will bc impei

! - This proposed eh&nge will not create the possibility of a new or different kind of accident-

! from any accident;previously evaluated. As discussed above, extending the allowable 1 l outage time from 7 to 10 days w;11 not create any new or different accidents from those

_ previously evaluated.

I This proposed change will not involve'a signincant reduction in a margin of safety. - No operating parameter, setpoint, or design limit is affceted. -No fission product barrier is l- degradedL therefore, no margin of safety as defined in the basis for any Technical

Specification will be reduced.

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{ Environmental Impact Statement-

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l - The proposed waiver of compliance has been reviewed against the criteria of 10 CFR 51.22 i- _ for environmental considerations. As shown above, the proposed change 'does not involve

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any significant hazards consideration, nor increase the types and amounts of effluents that

{ may be released offsite, nor increase the individual or cumulative occupational radiation p

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t exposun:s. Based on this, the proposed waiver of compliance meets the criteria given in 10 CFR 51.22 (c) (9) for categorical exclusion from the requirement for an Environmental Impact Statement.

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