ST-HL-AE-2307, Part 21 & Deficiency Rept Re ESF Actuation Signal Reset. Initially Reported on 870708.Control Circuits for Components Receiving ESF Actuation Signal Reviewed for Conformance Criteria.Affected Circuits Modified

Part 21 & Deficiency Rept Re ESF Actuation Signal Reset. Initially Reported on 870708.Control Circuits for Components Receiving ESF Actuation Signal Reviewed for Conformance Criteria.Affected Circuits Modified

ML20236N328
Person / Time
Site:	South Texas
Issue date:	08/04/1987
From:	Goldberg J HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
REF-PT21-87, REF-PT21-87-149-000 IEB-80-06, IEB-80-6, PT21-87-149, PT21-87-149-000, ST-HL-AE-2307, NUDOCS 8708110456
Download: ML20236N328 (5)

Text

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f The Light company Houston Lighting & Power _ P. O. Uox },700 I psustyin, Tcxas 77g_1_~(71gy8;q11 August 4, 1987 ST-HL-AE-2307 File No.: G12.395, G2.2 10CFR50.55(e) 4 10CFR21 I

U. S. Nuclear Regulatory Commission Attention: Document Control Desk Eashington, DC 20555 South Texas Project Units 1 and 2 Docket Nos. ETN 50-498, STN 50-499 Final Report Concerning Engineered Safety Features Actuation Signal Reset (IE Bulletin 80-06)

On July 8,1987, Houston Lighting & Power Company notified your office, pursuant to 10CFR50.55(e), of an item concerning Engineered Safety Features (ESF) Actuation Signal Reset at the South Texas Project. Enclosed is the Final Report on this item. We have determined that this item is reportable pursuant to 10CFR50.55(e) and 10CFR21.

If you should have any questions on this matter, please contact Mr.

S. M. Head at (512) 972-8392.

• Y J. H. Goldberg Group Vice President, Nuclear THC/ma

Attachment:

Final Report Concerning ESF Actuation Signal Reset 8708110456 870004 PDR ADOCK 05000498 S PDR

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L1/NRC/cc/hg-1 A Division ofIlouston Industries Incorporated

Houston Lighdng & Power Company ST-HL-AE-2307 File No.: G12.395, C2.2 Page 2 cc:

Regional Administrator, Region IV M.B. Lee /J.E. Malaski Nuclear Regulatory Commission City of Austin 611 Ryan Plaza Drive, Suite 1000 P.O. Box 1088 Arlington, TX 76011 Austin, TX 78767-8814

. N. Prasad Kadambi, Project Manager - A. von Rosenberg/M.T. Hardt U.S. Nuclear Regulatory Commission City Public Service Board 7920 Norfolk Avenue P.O. Box 1771 Bethesda, MD 20814 San Antonio, TX 78296 Robert L. Perch, Project Manager Advisory Committee on Reactor Safeguards U.S. Nuclear Regulatory Commission U.S. Nuclear Regulatory Commission 7920 Norfolk Avenue 1717 H Street Bethesda, MD 20814 Washington, DC 20555 Dan R. Carpenter .

Senior Resident Inspector / Operations l c/o U.S. Nuclear Regulatory Commission P.O. Box 910 Bay City, TX 77414 Claude E. Johnson Senior Resident Inspector / Construction c/o U.S. Nuclear Regulatory Commission P.O. Box 910 Bay City, TX 77414 M.D. Schwarz, Jr., Esquire Baker & Botts One Shell Plaza Houston, TX 77002 J.R. Newman, tire Newman & Holtz1uger, P.C.

1615 L Street, N.W.

Washington, DC 20036

• R.L. Range /R. P. Verret Central Power & Light Company P. O. Box 2121 Corpus Christi, TX 78403 l

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L1/NRC/cc/hg-1 Revised 6/23/87 j

6 Attachment ST-HL-AE-2307 9 . File No.:G12.395, G2.2'  ;

Page 1 of 3 '

South Texas Project  ;

Units 1 and 2 l

, -Docket Nos. STN 50-498, STN 50-499  !

Final Report Concerning ESF Actuation Signal Reset l l

I.. Summary l ,

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'During startup testing, several valves which receive ESF actuation  !

signals were found to return to their pre-ESF positions upon reset of the 1 ESF signal. This. situation represents a safety concern relative to the j steam generator blowdown isolation valves if a single failure of one ESF actuation train is postulated.

1. 1 This. item has'been determined to be reportable pursuant to 10CFR50.55(e) i and 10CFR21.

II Description of Deficiency LSTP's design commitment in response to NRC IE Bulletin 80-06 requires that once the equipment is actuated by an ESF signal, the equipment must remain in its emergency mode following reset of the actuation signal.  ;

During testing several-valves'and two Electrical Auxiliary Building (EAB) j

.HVAC reheat coils were found to return to their pre-ESF actuation.  ;

conditions following reset of the ESF actuation signal which is contrary {

to this commitment. 1 The valves affected were: 1.) the steam generator blowdown valves, 2.)

the steam generator sample valves, 3.) the feedwater control valves, and .

=4.) the feedwater bypass control valves. In the case of the sample' valves, isolation is accomplished through the use of two solenoid valves i in series in the sample line. Each of these valves receives an isolation 2

signal from a different ESF actuation train. For the other valves, two solenoid valves are placed in series in the air line of the positioner of each valve to vent air and. ensure closure of the valve. In each case, the two solenoid valves are actuated by different ESF trains.

In the case of the steam generator sample and blowdown valves, one of  :

each pair of solenoids currently requires a separate manual reset action 1 following reset of the ESF signal, while one solenoid in each pair will automatically reopen as soon as the ESF signal is reset. This design maintains steam generator blowdown and sample isolation following ESF signal reset if all three ESF actuation trains function properly. Should a failure of one ESF actuation train occur however, some of the process lines would be unisolated upon reset of the ESF signal.

The feedwater control and bypass control valves could return to their previous positions upon reset of the ESF signal. No separate manual reset la required to. reposition these control valves.

The EAB HVAC reheat coils are deenergized on a Safety Injection (SI)

. signal to minimize the heatload in the EAB. The control circuits are designed such that normal operation is restored upon reset of SI for the 1 associated train.

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Attachment ST-HL-AE-2307 File No.:G12.395, G2.2 Page 2.of 3 III.' Corrective Action The' control circuits for components receiving an ESF actuation signal have.been reviewed for conformance to the STP criteria. The control circuits for those valves identified as not meeting the criteria will be modified such that, each valve will remain in its ESF actuation position upon reset of the ESF signal. This action will be completed prior to entering Mode 4 operation. Actions for Unit 2 vill be completed prior to system turn over for Start-Up testing.  ;

The heat loads imposed on the HVAC system by the two reheat coils have been determined to be insignificant. Therefore, no corrective action is required in this case.

IV. Recurrence Control This problem has been determined to be an isolated incident and no special recurrence control measures are necessary. Review of ESF component control circuits for conformance to IE Bulletin 80-06 took e

place during 1985 and 1986. The components identified in this report had

.also been identified during the design reviews, but design modifications were not. implemented. The design for other equipment potentially affected by IE Bulletin 80-06 was properly implemented.

The required design modifications were not implemented because of a failure by the architect / engineer to implement follow-up action in response to an interdiscipline action item. A review of similar interdiscipline action items was performed to verify that this failure was an isolated occurrence. The project action item register was reviewed back through 1985 to identify interdiscipline action items which required a response. Of the items identified, a sampling was performed to verify that required actions and any subsequent design changes had been completed or properly dispositioned. This review did not identify any' additional deficiencies.

V. Safety Analysis Feedwater Valves:

For the feedwater control and bypass control valves, the ESF logic is such that a feedwater isolation signal may be generated as a result of an SI signal, a high-high water level signal in any steam generator, an excessive cooldown protection signal, or a low T-avg signal coincident with a reactor trip signal. Each of these signals would close the feedwater control and bypass control valves.

When an SI signal is actuated. Icedwater isolation is initiated and the reactor is tripped. When the T signal is reset, the feedwater isolation signal is not automatically reset since it is memorized in the Solid State Protection System (SSPS). The SSPS therefore maintains the feedwater isolation signal, and the feedwater control and bypass control valves will not reopen until the feedwater isolation signal is also reset.

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Attachment ST-HL-AE-2307 File No.: G12.395, G2.2 Page 3 of 3

_For'the high-high steam generator water level' signal and the excessive y .cooldown. protection signal, the reset of the feedwater. isolation' signal

. would reopen the control valves. However, these signals also trip'the feedwater pumpsLand close_the feedwater isolation valves. Therefore,-the feedwater lines could not be returned to service without a separate I action to. restart the feedwater' pumps and reopen the feedwater isolation L- ' valves.

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For the' case of a feedwater isolation signal. caused.by a low T-avg signal concurrent with a reactor trip signal,' reset of the isolation signal-

, would reopen the control valves. llowever, the feedwater isolation' valves also close upon receipt of the feedwater isolation signal and, upon reset' of that signal,. remain closed (in accordance with IEB 80-06). Therefore, the feedwater lines could not be returned to service without a separate manual reopening of the isolation valves.

, Given that the feedwater lines would remain isolated when the feedwater.

control valves open following ESF actuation signal reset, failure of the o

feedwater control and bypass control valves to meet the requirements of IEB 80-06 would not have an adverse affect upon the safety of operations.

Blowdown Valves:

The steam generator' blowdown valves and sample isolation valves are isolated in response to an SI signal in the event of a steam' generator tube rupture. Reopening of the isolation valves because of a reset of the SI signal and a single failure of an ESF train would result in blowdown through the steam generator blowdown and sample isolation valves, which is not bounded by existing safety analyses.

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Conclusion:

Had the deficiency related to the reopening of the steam generator l blowdown valves and the steam generator sample isolation valves on reset of an'SI actuation signal remained uncorrected, a steam generator tube rupture coupled with a single failure of an ESF actuation train would result in a radioactivity release pathway which is not bounded by existing safety analyses. Therefore, this deficiency is reportable pursuant to 10CFR50.55(e) and 10CFR21.

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