ML20096G556

Submits 60 Day Response to Insp Repts 50-373/95-09 & 50-374/95-09 Re Ventilation Plan.Schedule for Completion of Activities Encl

ML20096G556
Person / Time
Site:	LaSalle
Issue date:	01/18/1996
From:	Querio R COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9601250227
Download: ML20096G556 (6)

Text

__

Q)mmonwealth lxlison Company

, 125alle Generating Station 2Gil North 21st Road

,MarwillIcs. 11.61311-9757 Tel HI4357F'6I January 18,1996 United States Nuclear Regulatory Commission Washington, D.C. 20555 Attention: Document Control Desk

Subject:

LaSalla County Station Units 1 and 2 60 De Response to NRC on Ventilation Issues Inspection Report Nos. 50-373/95009; 50-374/95009 NRC Docket Numbers 50-373 and 50-374.

Reference:

1. W. L. Axelson letter to R.E. Querio, Dated November 29,1995, Transmitting NRC Inspection Report 50-373/95009, 50-374/95009 i

The enclosed attachment contains LaSalle County Station's 60 day response to the ventilation plan request that was transmitted with the Reference 1 letter.

If there are any que stions or comments concerning this letter, please refer them to me at (815) 357-6761, extension 3600.

l Respectfully, sh' R' E. Querio Site Vice President LaSalle County Station cc: H. J. Miller, Regional Administrator, Region III M. D. Lynch, Project Man:ger, NRR H. J. Simons, Acting Senior Resident Inspector, LaSalle D. L. Farrar, Nuclear Regulatory Services Manager, NORS Central file 9601250227 960118 f

PDR ADOCK 05000373 G

PDR

/

/

250040

'L 1\\

A 1:nicom Compan)-

4 LaSalle Station Ventilation Action Plan During the summer of 1995, hot weather raised many concerns with performance of the ventilation systems at LaSalle Station. The most important of these concerns was the August 16,1995 scram / Main i

Steam Isolation Valve (MSIV) isolation that was caused by the Leak Detection (LD) Group One isolation setpoint being exceeded after Reactor Building Ventilation (VR) isolated because of the loss of the 'B' Reactor Protection System (RPS) bus. As a result, the System and Site Engineering Departments have developed the following strategy to resolve the ventilation problems at LaSalle Station.

J Our current ellorts to improve ventilation system performance are addressing three significant problems as follows:

4

1) Resolve the operator workaround associated with Main Steam Tunnel (MST) LD,

2) Improve Turbine Building Ventilation (VT) such that sufficient cooling is provided to i

critical turbine building equipment and the turbine bailding meets the original design parameter of being negative with respect to outside air, and

3) Resolve performance weaknesses with the control room and auxiliary building ventilation systems.

)

The following sections describe our actions to address these three areas of concern. LaSalle Station j

believes this action plan v.ill improve the performance of the ventilation systems and is committed to its implementation.

Main Steam Tunnel (MST) Leak Detection (LD) Operator Workaround i

A loss of Reactor Protection System (RPS) power isolates the Reactor Building Ventilation (VR) by de-energizing the logic which closes the secondary contalmrent dampers on both units. Since the Reactor Building Ventilation system cools the MST, a loss of this system results in a rapid increase in the temperatures in the upper portion of the MST. This increase in temperature will exceed the leak detection system isolatioa setpoint within a few minutes.n the surnmer and cause the MSIV's to close. To prevent this isolation, the operators have been trained to very quickly determine if the VR isolation was valid. If the isolation is determined not to be valid, the operators jumper out the MST leak detection isolation l

logic.

Since this isolation occurred, the highest priority of the LaSalle Station System / Site Engineering departments has been to climinate this operator workaround. This will be completed by providing the l

engineering basis and design modifications necessary to eliminate spurious isolation of the MSIVs by the MST leak detection system. Our proposed plan will require NRC support in the form of a technical specification change which is planned to be submit'.ed January 19,1996. We are asking for expedited NRC review of the technical specification changes, so that modifications to the T/dT logic can be implemented during LIR07. We also plan to change the power supply associated with the VR isolation l

logic. This change will affect many different system interfaces. Due to its complexity this modification will be installed during L2R07/LIR08.

The following is a description of the actions LaSalle Station has taken, or plans to take, and a planned schedule for the actions required to correct this opera'.or workaround.

2

1 i

j l

ACTIVITY COMPLETION DATE

1) Calculate a critical crack length which will provide Completed 12/5/95 the bases for a 100 GPM leak used in the MST ventilation model.

2) 10CFR20 evaluation of a bounding 200 GPM leak.

Completed 12/8/95

3) Technical Review Committee approval for the following Completed 12/18/95 design changes associated with Temperature (T) and delta Temperature (dT) fogic changes based on ventilation model.

a) Relocate temperature detectors b)T/dT logic changes

4) Develop a MST Ventilation model, draR report Completed 12/22/95 will provide bases for new LD setpionts.

5) Determine appropriate number and content of ECN's Completed 1/2/96 for each DCP to allow for contingency planning in case NRC approvalis not received in time.

6) Develop detailed installation schedule for Completed 1/11/96 design changes associated with LIR07

7) Prepare Tech Spec change submittal.

Completed 1/12/96

8) Issue final MST ventilation model results.

Completed 1/16/96

9) Submit Tech Spec change a the NRC.

1/19/96

10) Issue Unit i Design Chang Packages (DCP) for:

1/25/%

a) Relocate temperature detectors b)T/dT logic changes

11) Install design changes a) Relocate temperature detectors LlR07/L2R07 b) T/dTlogic changes L1R07/L2R07 c) VR logic power change to DC L2R07/LIR08 s

i 3

=

l Turbine Building Ventilation The Turbine Building Ventilation (VT) system has two major problems which LaSalle Station is resolving. These are original design deficiencies that the station has lived with since plant construction.

I The first issue involves turbine building difTerential pressure (dP). The turbine building has been typically i

at a positive pressure compared to the outside which raises a concern about unmonitored releases.

UFSAR sections 9.4.4.1 and 9.4.4.2.f state that the VT system would keep the turbine building at a negative pressure relative to the outside to prevent unmonitored releases. A simple solution to correct building dP would be to reduce the building supply air flow. Steps have been taken to reduce supply air flow to make the building negative. However, this is not a final solution because reducing the supply air flow will worsen the temperature problems in the turbine building when outside air temperatures are higher.

The second issue is turbine building temperature. Temperatures in the Condensate / Condensate Booster (CD/CB) pump, Heater Drain (HD) pump, and Feedwater (FW) pump rooms are too high for people to work in during the summer and the temperature limits for the equipment are consistently challenged. The design temperature for the CD/CB pump room is 104 degrees F and the design temperature for the HD and FW pump rooms is 122 degrees F with an outside air temperature of 95 degrees F. A maximum ambient outside air temperature of 95 degrees F was assumed in the design of the VT system. These original design temperatures are too low. A new design will assume a maximum outside air temperature of 100 degrees F while attempting to reduce the temperature to the 90-95 degree F range in the CB/CD, HD, and FW pump rooms.

A VT system action plan was developed to permanently restore the turbine building to a negative pressure.

In addition, the temperatures in the CD/CB, HD and FW pump rooms will be reduced such that personnel can perform their function in those rooms safely and the equipment will not be forced to operate at its temperature limitations. The plans to deal with this problem include modifications to reduce supply / exhaust differential pressure and a major modification to provide a chilled water system for the turbine building. LaSalle Station is committed to bringing the tmbine building dP to a negative value, cooling it and maintaining it for the life of the plant.

The following is a description of the actions LaSa e Station has taken, or plan to take,9.d a planned u

schedule for the actions required to correct the problems with the VT system.

ACTIVITY COMPI ETION DATE

1) Complete turbine building thermal model.

Completed 11/1/95

2) Adjusted Station Heat Temperature Control Valves Completed 11/15/95

3) Imtiate Engineering Request (ER) for the addition Completed 11/17/95 of turning vanes in the VT exhaust stack to help reduce the VT exhaust pressure drop.

4) Complete walkdown of CD/CB, HD and FW pump Completed 12/18/95 rooms to determine insulation opportunities to reduce the room heat gains.

4

ACTIVITY COMPLETION DAIM (cont.)

5) Technical Review Committee (TRC)/ Business Completed 12/18/95 Resiew Committee (BRC) approval of the VT exhaust turning vane modification.

6) Prepare a LaSalle Special Test (LST) to reduce the VT Completed 12/19/95 supply air flow to make the turbine building dP negative I

while the outside air temperatures are low enough to maintain adequate cooling.

j

7) Implement LST to reduce VT supply air flow.

Completed 12/20/95 i

i

\\

8) Proside recommendations and engineering details for Completed 1/12/96 installation ofinsulation.

9) Develop project plan for VT Chiller modification.

Completed 1/15/%

10) Complete installation of filter bypass modification.

LIR07/L2R07 g

(This modification will result in increased cooling flow)

11) Install VT exhaust turning vanes to reduce the VT LIR07/L2R07 exhaust pressure drop.

12) Engineer the VT exhaust turning vane modification.

1/31/%

13) Install temporary evaporative coolers in a Unit 2 1/31/96 CD/CB room.

14) Set VT supply temperature to 60 degrees F to verify 1/31/96 chilled water solution will meet expectations.

15) Take data to determine affect of temporary evaporative 2/2F/96 coolers.

16) VT Chiller modification installation a) Temporary chillers 6/7/96 b) Permanent chillers 6/6/97 5

Control Room (VC) and Auxiliary Electric Eauipment Room (VE) Ventilation The VC/VE systems have had several problems identified including compressor trips and damper cctuator failures. Also, the inadequate cooling of the control room by the 'B' VC compressor is a concern. Most of the VC/VE system problems have resulted from insufficient preventive maintenance and performance monitoring. Thus our actions are mostly aimed at resohing these differences. Station management recognized this inadequate system performance this past surmner and increased emphasis on identifying problems, root causes, and implementing corrective actions.

We believe VC/VE performance has improved as a result of these actions but we are still not yet satisfied that the system is performing to our standards. LaSalle Station is committed to maximizing the performance of the VC/VE systems. Through system performance monitoring System Engineering is confident that the problerns with the VC/VE systems will be corrected in a timely manner.

The following is a description of the actions LaSalle Station has taken, or plan to take, and a planned schedule for the actions required to correct the problems with the VC/VE systems.

ACTIVITY COMPLETION DATE

1) Monitor performance parameters and Began 10/2/95 determine the need to instrument other HVAC compressors. Tune compressors, as required, to maximize system performance.

2) Install instrumentation on the OB VC Completed 12/15/95 refrigeration subsystem in order to accurately assess operating performance data.

3) Investigate whether the Temperature 2/16/96 Control Valves (TXV's) are the proper size and type for our application. The

(

TXV's should hold steady. Our data shows they hunt.

4) Use temperature data to determine the 2/16/96 need for an oil cooler. Vendor recommends an oil cooler when discharge oil temperatures exceed 120 degrees F.

5) Determine the root cause for the major oil 3/22/96 level changes seen in the HVAC compressors.

6) Determine the root cause of the ITT actuator 4/19/96 failures.

)

7) Develop a preventative maintenance program 5/3/96 for the ITT actuators based on the root cause j

analysis.

6 L.