ML20062J772
| ML20062J772 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 08/06/1982 |
| From: | Oprea G HOUSTON LIGHTING & POWER CO. |
| To: | Jay Collins NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, ST-HL-AE-866, NUDOCS 8208160460 | |
| Download: ML20062J772 (5) | |
Text
_.
The Light company ii_,> ue,s.,m_ m sx noo ii_,,.wxesmoi aimmeii August 6, 1982 ST-HL-AE-866 File Number: G12.95 SFN: V-0530 Mr. John T. Collins fmM Regional Administrator, Region IV
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idjlq r ny Nuclear Regulatory Commission 9 g hj/
9 611 Ryan Plaza Dr., Suite 1000 Arlington, Texas 76012 i
Alf
Dear Mr. Collins:
4 South Texas Project J
Units 1 & 2 Docket Nos. STN 50-498, STN 50-499 Fifth 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 & Power Company (HL&P) notified your office of an item concerning the use of fail open isolation dampers in the heating, ventilation and air conditioning (HVAC) design. There is a concern that the use of fail open isolation dampers had l
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 item be included under the envelope of the existing deficiency concerning the HVAC design. 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 the concern and confinning that the item will be included within the envelope of the existing HVAC item.
The attached report addresses those concerns regarding the use of fail open isolation dampers that have been identified to date. Any future similar concerns will be addressed in future reports regarding the overall HVAC design..The next report regarding the overall HVAC design concern is scheduled to be submitted to your office by l
October 18, 1982.
If you should have any questions concerning this matter, please contact Mr. Michael E. Powell at (713) 877-3281.
Ver truly,yours,
//6p'h./
l
-d Executive Vice President MEP/kr Attachment 17 l
8208160460 820806 PDR ADOCK 05000498 3
W 1.
Ilouston 1.ighting & Power Company cc:
G. W. Oprea, Jr.
August 6, 1982 J. H. Goldberg ST-HL-AE-866 J. G. Dewease File Number: G12.95 J. D. Parsons SFN: V-0530 D. G. Barker Page 2 C. G. Robertson R. A. Frazar J. W. Williams J. W. Briskin J. E. Geiger R. L. Ul rey S. M. Dew J. 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 RMS Director, Office of Inspection & Enforcenent Nuclear Regulatory Commission Washington, D. C. 20555 G. W. Muench/R. L. Range Charles Bechhoefer, Esquire Central Power & Light Company Chairman, Atomic Safety & Licensing Board P. O. Box 2121 U. S. Nuclear Regulatory Commission Corpus Christi, Texas 78403 Washington, D. C.
20555 H. L. Peterson/G. Pokorny Dr. James C. Lamb, III City of Austin 313 Woodhaven Road P. O. Box 1088 Chapel Hill, North Carolina 27514 Austin, Texas 78767 J. B. Poston/A. vonRosenberg Mr. Ernest E. Hill City Public Service Board Lawrence Livermore Laboratory l
P. O. Box 1771 University of California l
San Antonio, Texas 78296 P. O. Box 808, L-46 Livermore, California 94550 Brian E. Berwick, Esquire William S. Jordan, III Assistant Attorney General Harnon & Weiss for the State of Texas 1725 I Street, N. W.
P. O. Box 12548 Suite 506 Capitol Station Washington, D. C.
20006 Austin, Texas 78711 Lanny Sinkin Citizens for Equitable Utilities, Inc.
Citizens Concerned About Nuclear Power c/o Ms. Peggy Buchorn 5106 Casa Oro Route 1, Box 1684 San Antonio, Texas 78233 Brazoria, Texas 77422 Jay Gutierrez, Esquire Hearing Attorney Office of the Executive Legal Director U. S. Nuclear Regulatory Commission Washington, D. C.
20555 Revision Date 04-19-82
Fifth Interim Report Concerning the Heating, Ventilation and Air Conditioning Design - The Use of Fail Open Isolation Dampers I.
Sumary On July 6,1982, pursuant to 10CFR50.55(e), Houston Lighting & Power Company (HL&P) notified the Nuclear Regulatory Commission (NRC) of two (2) items regarding the use of fail open dampers at the discharge of redundant supply fans in the Electrical Auxiliary Building (EAB) and Isolation Valve Cubicle (IVC). HL&P's Incident Review Committee (IRC) determined that both the items should be considered as part of a generic concern regarding the use, by Brown & Root, Inc. (B&R) of nonsafety related 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, including consultants' reports, which identified several additional discrepancies under the above generic concern and another related item regarding single failure of the supply air mixing box and associated pneumatic dampers in the EAB.
II.
Description of Incident A.
Nonsafety Pneumatic Air Controllers in Safety Related HVAC Systems All automatic dampers in safety related HVAC systems are operated pneumatically, and the instrument air system serving these dampers is nonsafety related.
Following an accident these dampers are not operable and the failure mode is not appropriate in some cases in that 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 redundant fans or air handling units fail open during an accident condition, thereby resulting in back flow / recirculation through the standby fan or unit.
This condition exists in the following cases:
1.
EAB main supply air handling units.
Impact on safety function is partial loss of cooling to safety related equipment and loss of control room pressurization.
2.
IVC supply fans.
Impact on safety function is partial loss of cooling to safety related equipment.
3.
Fuel Handling Building (FHB) exhaust fans.
Impact on safety function is reduction of exhaust flow with radiological release consequences in a post-LOCA condi tion.
4.
Electrical penetration area exhaust fans.
Impact on safety function is loss of negative pressure with potential radiological release consequences.._.
b)
The safety function control dampers have been provided with nonsafety related pneumatic instrument controls.
Consequently, during an accident condition without assumed loss of instrument air, these instrument controls could malfunction, resulting in erroneous operation of control dampers. This condition exists in the following cases:
1.
EAB mixing box dampers, resulting in loss of cooling to safety related equipment.
2.
EAB/ Control room pressurization dampers resulting in loss of pressurization.
3.
Electrical penetrat.on area and FHB pressure control dampers, resulting in loss of negative pressures.
4.
FHB exhaust air flow control dampers, resulting in reduction of exhaust air and radiological impact.
c)
The pneumatic isolation dampers for EAB outside air intakes fail open during accident conditions, and they do not have redundancy in series.
In the case of a toxic gas release condition concurrent with a loss of instrument air, this could result in loss of control room habitability.
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 for each room. The cooling for each room is controlled by pneumatic dampers (one in the hot duct and one in the cold duct, linked together) in the mi:,ing box, which are served by a nonsafety instrument air system.
During emergency operation with loss of instrument air, these dampers are designed to fail open in the cold duct such that cooling is assured.
The deficiency concern is that in certain areas with more than one train of safety-related equipment, there is no redundancy in the supply air mixing boxes. These areas have been identified as Cable Spreading room 0 El 60'0", Relay room 0 El 35'0" and HVAC rooms 0 El 86'0".
A failure associated with the mixing box in these areas would degrade cooling and result in higher than design room temperature, which would consequently jeopardize operation of two or more trains of equipment in these areas. A credible failure mode of the mixing box is that the mixing box damper remains stuck closed in the cold duct due to mechanical failure, thereby stopping cooling.
m Further description of this condition is given in the following table:
No.
Room Equipment No. of Mixing Impact of a single Trains in boxes serving mixing box damper the room the room failure 1
Cable Spreading B, C 1
No Cooling Room El 60'0" 2
Relay Room A,B,C 2
Cooling reduced by El 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 actions will be discussed in future reports.
IV.
Safety Analysis The potential safety impact of each item described in Section II above is identified with the item.
The cause of the incident is considered to be that the existing design concept utilizing nonsafety related pneumatic dampers and controllers did not adequately address the possible failure modes of these devices under accident conditions and the impact of single active failure of mixing boxes in EAB was not fully considered. The overall HVAC system design is currently under detailed evaluation by BPC as part of the Transition Program for the South Texas Project (STP).
Resolution of these and other previously identified HVAC problems is scheduled for completion prior to release of the affected portions of the systems for continued construction and installation at STP.