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The Lightcompany ii_,> ue,s.,m_ m sx noo ii_,,.wxesmoi aimmeii

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August 6, 1982ST-HL- AE-866File Number: G12.95SFN: V-0530

Mr. John T. CollinsfmMRegional Administrator, Region IV ;/'~- idj|qr

nyNuclear Regulatory Commission

9 g hj/9611 Ryan Plaza Dr. , Suite 1000 ,

Arlington, Texas 76012 i AlfDear Mr. Collins: 4

South Texas Project JUnits 1 & 2

Docket Nos. STN 50-498, STN 50-499Fifth Interim Report Concerning the Heating, Ventilation and Air

Conditioning Design - The Use of Fail Open Isolation Dampers

On July 6,1982, pursuant to 10CFR50.55(e), Houston Lighting & PowerCompany (HL&P) notified your office of an item concerning the use of fail openisolation dampers in the heating, ventilation and air conditioning (HVAC)design. There is a concern that the use of fail open isolation dampers had|

' not been adequately assessed by Brown & Root, Inc. (B&R) in the HVAC design.In our initial notification, Mr. M. E. Powell of HL&P requested that this itembe included under the envelope of the existing deficiency concerning the HVACdesign. Mr. W. A. Crossman of your staff indicated that this was acceptable;

! however, he requested that HL&P submit a letter identifying the scope of theconcern and confinning that the item will be included within the envelope ofthe existing HVAC item. The attached report addresses those concernsregarding the use of fail open isolation dampers that have been identified todate. Any future similar concerns will be addressed in future reportsregarding the overall HVAC design. .The next report regarding the overall HVACdesign concern is scheduled to be submitted to your office by

| October 18, 1982.

If you should have any questions concerning this matter, please contactMr. Michael E. Powell at (713) 877-3281.

Ver truly,yours ,

//6p'h ./| -d'

Executive Vice President

MEP/krAttachment 17

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8208160460 820806PDR ADOCK 050004983 PDR

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Ilouston 1.ighting & Power Company

cc: G. W. Oprea , Jr. August 6, 1982J. H. Goldberg ST-HL- AE-866J. G. Dewease File Number: G12.95J. D. Parsons SFN: V-0530D. G. Barker Page 2C. G. RobertsonR. A. FrazarJ. W. WilliamsJ. W. BriskinJ. E. GeigerR. L. Ul reyS. M. DewJ. T. Collins (NRC)D. E. Sells (NRC)W. M. Hill , Jr. (NRC)M. D. Schwarz (Baker &Botts)R. Gordon Gooch (Baker &Botts)J. R. Newman (Lowenstein, Newman, Reis, & Axelrad)STP RMSDirector, Office of Inspection & Enforcenent

Nuclear Regulatory CommissionWashington, D. C. 20555

G. W. Muench/R. L. Range Charles Bechhoefer, EsquireCentral Power & Light Company Chairman, Atomic Safety & Licensing BoardP. O. Box 2121 U. S. Nuclear Regulatory CommissionCorpus Christi, Texas 78403 Washington, D. C. 20555

H. L. Peterson/G. Pokorny Dr. James C. Lamb, IIICity of Austin 313 Woodhaven RoadP. O. Box 1088 Chapel Hill, North Carolina 27514Austin, Texas 78767

J. B. Poston/A. vonRosenberg Mr. Ernest E. HillCity Public Service Board Lawrence Livermore Laboratory,

| P. O. Box 1771 University of California| San Antonio, Texas 78296 P. O. Box 808, L-46

Livermore, California 94550

Brian E. Berwick, Esquire William S. Jordan, IIIAssistant Attorney General Harnon & Weiss

for the State of Texas 1725 I Street, N. W.P. O. Box 12548 Suite 506Capitol Station Washington, D. C. 20006Austin, Texas 78711

Lanny Sinkin Citizens for Equitable Utilities, Inc.Citizens Concerned About Nuclear Power c/o Ms. Peggy Buchorn5106 Casa Oro Route 1, Box 1684San Antonio, Texas 78233 Brazoria, Texas 77422

Jay Gutierrez, EsquireHearing AttorneyOffice of the Executive Legal DirectorU. S. Nuclear Regulatory CommissionWashington, D. C. 20555 Revision Date 04-19-82

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Fifth Interim Report Concerning the Heating, Ventilation andAir Conditioning Design - The Use of Fail Open Isolation Dampers

I. Sumary

On July 6,1982, pursuant to 10CFR50.55(e), Houston Lighting & PowerCompany (HL&P) notified the Nuclear Regulatory Commission (NRC) of two(2) items regarding the use of fail open dampers at the discharge ofredundant supply fans in the Electrical Auxiliary Building (EAB) andIsolation Valve Cubicle (IVC). HL&P's Incident Review Committee (IRC)determined that both the items should be considered as part of a genericconcern regarding the use, by Brown & Root, Inc. (B&R) of nonsafetyrelated pneumatic air controllers in safety related HVAC systems.Subsequent to the July 6,1982 notification, Bechtel Power Corporation(BPC) performed an initial review of the overall HVAC design, includingconsultants' reports, which identified several additional discrepanciesunder the above generic concern and another related item regarding singlefailure of the supply air mixing box and associated pneumatic dampers inthe EAB.

II. Description of Incident

A. Nonsafety Pneumatic Air Controllers in Safety Related HVAC Systems ,

All automatic dampers in safety related HVAC systems are operatedpneumatically, and the instrument air system serving these dampersis nonsafety related. Following an accident these dampers are notoperable and the failure mode is not appropriate in some cases inthat it could result in degradation of the system safety functions.At present, concern for the following areas has been identified:

a) The pneumatic dampers at the discharge of parallel redundantfans or air handling units fail open during an accidentcondition, thereby resulting in back flow / recirculation throughthe standby fan or unit. This condition exists in thefollowing cases:

1. EAB main supply air handling units. Impact on safetyfunction is partial loss of cooling to safety relatedequipment and loss of control room pressurization.

2. IVC supply fans. Impact on safety function is partialloss of cooling to safety related equipment.

3. Fuel Handling Building (FHB) exhaust fans. Impact onsafety function is reduction of exhaust flow withradiological release consequences in a post-LOCAcondi tion.

4. Electrical penetration area exhaust fans. Impact onsafety function is loss of negative pressure withpotential radiological release consequences.

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b) The safety function control dampers have been providedwith nonsafety related pneumatic instrument controls.Consequently, during an accident condition without assumedloss of instrument air, these instrument controls couldmalfunction, resulting in erroneous operation of controldampers. This condition exists in the following cases:

1. EAB mixing box dampers, resulting in loss of coolingto safety related equipment.

2. EAB/ Control room pressurization dampers resulting inloss of pressurization.

3. Electrical penetrat.on area and FHB pressure controldampers, resulting in loss of negative pressures.

4. FHB exhaust air flow control dampers, resulting inreduction of exhaust air and radiological impact.

c) The pneumatic isolation dampers for EAB outside airintakes fail open during accident conditions, and they donot have redundancy in series. In the case of a toxic gasrelease condition concurrent with a loss of instrumentair, this could result in loss of control roomhabitability.

B. Single Failure of Supply Air Mixing Box in EAB

- The EAB HVAC system consists of a dual duct (hot and cold)supply air system with a mixing box at the supply tenninal foreach room. The cooling for each room is controlled bypneumatic dampers (one in the hot duct and one in the cold>

duct, linked together) in the mi:,ing box, which are served by anonsafety instrument air system. During emergency operationwith loss of instrument air, these dampers are designed to failopen in the cold duct such that cooling is assured.

The deficiency concern is that in certain areas with more thanone train of safety-related equipment, there is no redundancyin the supply air mixing boxes. These areas have beenidentified as Cable Spreading room 0 El 60'0", Relay room 0 El35'0" and HVAC rooms 0 El 86'0". A failure associated with themixing box in these areas would degrade cooling and result inhigher than design room temperature, which would consequentlyjeopardize operation of two or more trains of equipment inthese areas. A credible failure mode of the mixing box is thatthe mixing box damper remains stuck closed in the cold duct dueto mechanical failure, thereby stopping cooling.

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Further description of this condition is given in the following table:

No. Room Equipment No. of Mixing Impact of a singleTrains in boxes serving mixing box damperthe room the room failure

1 Cable Spreading B, C 1 No CoolingRoom El 60'0"

2 Relay Room A,B,C 2 Cooling reduced byEl 35'0" 50%

3 HVAC Rm El 86'0" A, B 1 No Cooling

III. Corrective Action

Modification of the design is under consideration. Corrective actionswill be discussed in future reports.

IV. Safety Analysis

The potential safety impact of each item described in Section II above isidentified with the item. The cause of the incident is considered to bethat the existing design concept utilizing nonsafety related pneumaticdampers and controllers did not adequately address the possible failuremodes of these devices under accident conditions and the impact of singleactive failure of mixing boxes in EAB was not fully considered. Theoverall HVAC system design is currently under detailed evaluation by BPCas part of the Transition Program for the South Texas Project (STP).Resolution of these and other previously identified HVAC problems isscheduled for completion prior to release of the affected portions of thesystems for continued construction and installation at STP.

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