ML20151E722
| ML20151E722 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 07/15/1988 |
| From: | Sailer W GILBERT/COMMONWEALTH, INC. (FORMERLY GILBERT ASSOCIAT |
| To: | Murley T Office of Nuclear Reactor Regulation |
| References | |
| REF-PT21-88-085-000 PT21-88-085-000, PT21-88-85, NUDOCS 8807260183 | |
| Download: ML20151E722 (3) | |
Text
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( Gilbert / Commonwealth, Inc. engineers andconsuitants V
P.O. Box 1498, Reading, PA 196031498/ Telephone 215-775-2600. Cable Gilasoc/ Telex 836-431 W.F. SAILER Vice President & General Manager Quality Assurance Division July 15,1988
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- United States Nuclear Regulatory Commission Office of Nuclear Reactor Regulation Washington, l'C 20555 Attn: Dr. T. E. Murley, Director Re: Reportable Event Steam Propagation Path Affecting Unqualified Equipment
Dear Mr. Murley:
This letter documents a report by telephone on July 13, 1988, at approximately 4:30 pm to Mr. C. Gould, under the provisions of 10CFR21.
l dividual Who Reported (i) a The call was made by Mr. R. C. Holzwarth, Corporate QA Program Manager, for Mr. W. F. Saller, Vice President and General Manager, Quality Assurance Division, who was out of the country.
(ii)
Faellitv/ Activity / Basic Component The activity / basic component is design related. it involves the analysis of the effect of a main steam line pipe rupture on the environment and safe shutdown equipment in Switchgear Room No. IB 63-01 at the V. C. Summer Nuclear Station, owned and operated by South Carolina Electric & Gas Company (SCE&G).
(ill) Identification of Firm Gilbert / Commonwealth, Inc., (G/C, Inc.) the engineer of record, performed the design.
(iv) Nature of Defect / Safety Hazard Created n
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During a review to provide revised characterization of area temperatures and i
humidity for accident events for equipment qualification purposes, G/C, Inc.
mn discovered an oversight in the original design. An unsealed steam propagation path was discovered which could potentially affect safety related equipment in the event of a postulated steam break outside containment.
NO The applicable scenario involved a main steamline break (modes 3 through 5) p which occurs on the 436' elevation (room IB 36-02) of the Intermediate Building ox (IB) upstream of the main steam isolation valves. The steam from this break
@@m was postulated to go directly to room IB 63-01 via non pressure rated floor penetrations. The steam flow was also pcstulated to go through a non-safety I
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3 gg Page 2 fire door leading into a stairwell. Steam fills this stairwell and proceeds through another fire door (IB 407) at the 463' elevation of the IB leading to a corridor -
(room IB 63-03). From here steam can leak into the "A" Train Switchgear room.
(IB 63-01) through heavy, bullet resistent, but not pressure' tight, double doors (IB 408). Room IB 36-01, which is below IB 63-01, also centains electrical equipment required to achieve and maintain safe shutdown ("B" Train Switchgear) and communicates with IB 63-01 through floor penetrations. From corridor IB 63-03 steam can also enter, through double doors similar to IB 408, room IB 63-02. Though IB 63-02 does not contain equipment required to shutdown the plant and maintain its shutdown, it is in direct communication, again through floor penetrations, with rooms IB 36-03, A, B, IB 36-04, IB 36-05, and IB 36-06 which do contain safe shutdown equipment. (Control room evacuation panels and electrical equipment for all three component cooling water pumps.) Therefore, rooms IB 36-01, IB 36-03, A, B, IB 36-04, 36-05, 36-06, and IB 63-01 are all subject to steam intrusion.
In addition a steam break (reheat steam jet) in the Turbine Building (TB)
(modes 5 thru 2 with main steam Isolation valves open) could enter IB 63-03 through door IB 409 and subsequently enter rooms IB 63-02 and IB 63-01 with the same results as described above.
(v)
Date Information was Obtained The Mechanical Department Manager determined on July 12,1989 that the design oversight i? reportable by G/C, and notified responsible company -
management.
(vi) Number and Location of Defects I
The design oversight described above is an isolated case for the V. C. Summer Plant. No other Gilbert / Commonwealth designed plants are affected.
(vil) Corrective Action i
Upon notification by G/C of the stean propagation path scenario, operations persor.nel initiated a plant shutdown from Mode O to Mode 4. The plant was maintained in Mode 4 subsequent to the initiation of the immediate corrective actions of opening doors to IB 63-03 to limit pressure buildups and sealing IB 408 to prevent moisture intrusion to IB 63-01.
As a temporary measure to limit potential pressure buildups in the event of a steam break the following doors were blocked opem IB 405 from corridor 63-03 to the IB roof, IB 409 from corridor 63-03 to the TB, IB 403 from room 63-02 to the TB, and IB 313 from the stairwell to the TB. Appilcable roving fire watches were also established. To limit moisture intrusion through IB 408 from corridor 63-03 to room 63-01 (switchgear room), all edges of the door were sealed with duct tape. In addition the main steam isolation valves were required to be closed in mode 3 as long as the doors between the Turbine and Intermediate Buildings were blocked upon. Door IB 407 (from the stairwell into corridor IB 63-03) was reinforced to ensure it would remain closed in the event of the postulated brenks and was also scaled with a neoprene seal to ensure it remained leak tight.
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, 19 Page 3 To mitigate the consequences of the postulated steam breaks the following additional actions were completed by the Owners (1)
Door IB 407 was reinforced and sealed to ensure it remained closed and prevent steam leakage in the event of a steam break.. This temporary modification impacted the fire rating capability of tha door and therefore a 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> roving fire watch was established for the door.
(2)
Door IB 408 remained sealed to prevent moisture intrusion into IB 63-01.
(3)
Applicable silicone foam fire seals between the rooms in question were verified to be capable of withstanding pressures which would be experienced in the event of a postulated steam break.
(4)
Door IB 409 was reinforced to enable it to withstand a steam jet origina*.ing in the Turbine Building.
(5)
The latch on door IB 405 was removed to allow the door to open and relieve any pressure buildup in corridor IB 63-03 in the event of a Turbine Building steam break and the resulting leakage under door IB 409.
A review of the plant outside containment was performed to identify other possible scenarios. Eight scenarios have been found which do not create a substantial safety hazard. Four other scenarios are still being evaluated. This evaluation is expected to be completed within four weeks.
Long term corrective actions are currently being evaluated by Gilbert / Commonwealth.
(vill) Advice to Licensee None.
If you require any further information, please call me at (215) 775-2009.
Very truly yours, d
. F. Sailer Vice Prcsident and General Manager Quality Assurance Division WFS:mvh ec:
T. E. Murley - NRC (2)
J. C. Stone - NRC - Vendor inspection Branch Document Management Branch - NRC R. B. Clary - SCE&G A. R. Koon, Jr. - SCE&G C. D. Williams W. K. Burkhart W. E. Meek K. E. Nodland
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