ML17279A431

LER 87-018-00:on 870626,reactor Automatically Scrammed by Reactor Protection Sys Actuation Due to Normal Auxiliary Power Transformer Sudden Pressure Relay Actuation.Caused by Opening of Test Valve.Transformers inspected.W/870727 Ltr

ML17279A431
Person / Time
Site:	Columbia
Issue date:	07/27/1987
From:	Arbuckle J, Powers C WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
LER-87-018, LER-87-18, NUDOCS 8708040316
Download: ML17279A431 (10)

Text

ULA 'Y I NFORNAT lON D ISTR JT I YSTEI'1 ( R IDS )

1 ACCESSION NBP.; 870804031c'D DOC. DATE. 87/07/27 NOTARIZED: NO DOCKET FAC IL: 50-397 WPPSS Nuclear ProJect. Unit 2> Washington Public Poee 05000397 AUTH. MANE AUTHOR AFFILIATION ARBUCKEL> J, D. I>ashington Public PoUjer Supply System POWERS> C., N. Washington Public Poeer Supply System PECIP. NA >8 F! EC I P I ENT AFFILIATION SUBJECT*. LEP. 87-018-00 on 87062a> reactor automaticalg scrammed bg reactcr p"otection sos due to actuation of sudden pressure relau on normal a'uxiliarg power transformer. Caused bg opening of test valve. Transformers inspected. W/870727 ltr.

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~ UPPI.SMSNTAL htfONT SXPtCTSD nel MONTH DAY tXP SCTSD 5UsMlsaoN OATS llSI YSS Ilfyw, caooNN tÃSSCSCD SUSNISSION DATtl A05TNAcT Ichor Io to00 MoeeA ca, ~ooeeelf Itheoo sks~eee IHNoeIINo Need n a On June 26, 1987 at 1541 hours0.0178 days <br />0.428 hours <br />0.00255 weeks <br />5.863505e-4 months <br />, the reactor automatically scrammed by Reactor Protection System (RPS) actuation due to Turbine Control Valve (TCV) Fast Closure.

The TCV fast closure was in response to a unit lockout signal resulting from the actuation of a sudden pressure relay on Normal Auxiliary Power Transformer TR-Nl.

On June 27, 1987 at 1813 hours0.021 days <br />0.504 hours <br />0.003 weeks <br />6.898465e-4 months <br />, a similar event occurred involving the sudden pressure relay on Normal Auxiliary Power Transformer TR-N2.

The cause of both sudden pressure relay actuations was determined to be the unexpected opening of a test (poppet) valve associated with the relays (the valves are used to test the relays). When the valve opened, a differential pressure developed across the bellows of the sudden pressure relays. The relays responded as designed by causing a generator trip, a turbine trip and, because reactor power was above 30Ã, a reactor scram. In both instances, plant post-trip response was normal in all aspects.

There is no safety significance associated with either event in that plant protection systems and electrical distribution realignments functioned as designed. These events posed no threat to the health and safety of either the public or plant personnel.

87080403i6 870727 PDR ADOCK 05000397 I< 2.Z 8 PDR Iy NNC Socio 544 1505 I

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NRC Form 355A UA. NUCLEAR REOULATORY COMM1551ON (043(

UCENSEE EVENT REPORT ILER) TEXT CONTINUATION APPROVED OMS NO. 3150-0(04 EX( (RES: e(31/85 PAClLITY NAME (11 OOC((ET NUIIEKR (2) LER NUMEER (5( PACE (S W'5OVKNTIAL Ar NtVdlON

%>ct lt naia/. vtt Plant Conditions

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1. June 26, 1987 a) Power Level - 42K b) Plant Mode - 1 (Power Operation)

2. June 27, 1987 a) Power Level - 58%

b) Plant Mode - 1 (Power Operation)

On June 26, 1987,'he Plant was ascending in power on a return to operations following a maintenance and refueling outage. Both Reactor Recirculation (RRC) pumps were operating in slow speed; and two condensate pumps, two booster pumps, two circulation water pumps and both feedwater pumps were in operation.

At 1541 hours, the reactor automatically scrammed by Reactor Protection System (RPS)'ctuation due to Turbine Control Valve (TCY) Fast Closure.

The TCY fast closure was the result of a turbine trip caused by the tripping of Unit Lockouts 86XU, 86XUOA, 86X1U and 86X1UOA. The Unit Lockouts were tripped by the actuation of a sudden pressure relay on Normal Auxiliary Power Transformer TR-Nl. The Post-scram response of the Plant was normal in all aspects.

The cause of the TR-Nl sudden pressure relay actuation was initially believed to be a fault internal to the transformer. This conclusion was based on the fol lowing:

o The sudden pressure relay was found to be functioning properly as verified by tests specified by the vendor.

o The initial report from the Bonneville Power Administration (BPA) on taken from TR-Nl indicated a change in combustible gas oil'amples concentration which could indicate an internal fault leading to a valid

.sudden pressure signal. TR-Nl had previously demonstrated some measurable internal changes due to a transient in 1985.

Accordingly, TR-Nl was isolated from the Plant Electrical Distribution System.

Inspections of the Plant and Normal Auxiliary Power Transformer.TR-N2 showed no abnormalities and, at 2200 hours0.0255 days <br />0.611 hours <br />0.00364 weeks <br />8.371e-4 months <br />, the Plant was restarted. Investigation of the problems associated with TR-Nl continued.

NRC >ORM 550A

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)D D D NRC Form 3ttA 0 0 US. NUCLEAR RE4ULATORY COMMISSION (043 I UCENSEE EVENT REPORT ILER) TEXT CONTINUATION APPROVED OMS NO. 3(50-Ol(H EXPIRES: Sfl(NS FACILITY NAME (ll DOCRET NUMEER (31 LER NUMEER (Sl PA4E 131 YEAR QW tt4vtrrTIAL ol~'. rltvIS IO rr VM II NVM trI Washington Nuclear P lant - Unit 2 o s o o o 8 7 0 18 000 3 OF .0 TEXT RY moro rrroco ls rpprrrrL rrto adttrorW NIIC Arm 393A'rl (171 On June 27, 1987 the Plant was ascending in power on a return to operations following the scram on the previous day. Both RRC pumps were operating in fast speed; and three condensate pumps, two booster pumps, two circulation water pumps and both feedwater pumps were in operation. The electrical distribution lineup was abnormal in that TR-Nl was tagged out and isolated from the Electrical Distribution System.

At 1813 hours0.021 days <br />0.504 hours <br />0.003 weeks <br />6.898465e-4 months <br />, the reactor automatically scrammed by'RPS actuation due to TCY Fast Closure. The TCY fast closure was the result "of a turbine trip caused by the tripping of Unit'ockouts 86XU, 86XUOA, 86XlU and 86X1UOA. The Unit Lockouts were tripped by the actuation of a sudden pressure relay on TR-N2.

The post-scram response of the Plant was normal in all aspects.

The cause of both sudden pressure relay actuations was the unexpected opening of a test valve installed on the relays. The valves were designed to open to atmosphere at nominally 10 psig and were installed by the manufacturer of the transformers. The purpose of the valves is to facilitate testing of the. sudden pressure relays. These valves serve no function during normal operation and were not shown on the transformer manufacturer drawings. When the valves opened, a differential pressure developed across the bellows of the sudden pressure relays. The relays responded as designed by causing a generator trip, a turbine trip and, because reactor power was above 30%, a reactor scram.

~D The root cause of the June 26 trip is inadequate design configuration control in that the installation of the poppet valve was not controlled and, as a result, the relationship of the sudden pressure relay and cover gas system operation was not fully understood.

The root cause of the June 27 trip is inadequate root cause determination of the previous (June 26) scram. Transformer oil sample analysis results were compared with data taken in March, 1986 rather than with the most recent data from January, 1987. Further data regarding the condition of TR-Nl were not sufficiently evaluated. While oil samples seemed to indicate a faulted condition, local and remote indications of oil and winding temperatures were all within normal limits. Insufficient data was used to conclude that a problem existed on TR-Nl and that further investigation into the actuation of the sudden pressure relay was not immediately required.

Immediate Corrective Action

1. June 26, 1987 TR-Nl was isolated from the Plant Electrical Distribution System and oil samples were obtained and analyzed. Inspections of the Plant and TR-N2 were performed and the Plant was restarted. Investigation of the problems associated with TR-Nl continued.

NIIC FOIIM tooA (9tLll

NIIC Form 0SSA US. NUCLEAR IIEOULATOIIYCOMMISSION IMSI LICENSEE EVENT REPORT (LER) TEXT CONTINUATION APPAOVEO OMS NO. SI 50-0104 EKPIIIES: 8/01/85 FACILITY NAME ill DOCKET NUMSEII ISI LEII NUSNIth W PACE lSI YEAN SSOVSNTIAI II% V IS IO N NVM %ll N M Sll Washington Nuclear Plant - Unit 2 o s o o o 3 9 7 8 70 8 000 4 OF 0 5 TEXT /I/INSIP e>>Oe N /N/NPNS VM //I/Sns/H/IC An/I 0/t/Al/ LIT/

2. June 27, 1987 The test valves on the sudden pressure relays for TR-Nl and TR-N2 were removed and plugged, and oil samples were obtained and sent to BPA for analysis.

Further Evaluation Corrective Action Further Evaluation (a) Operating procedures require the internal pressure of TR-Nl and TR-N2 to be maintained between -3 and +8 psig. However, this range was incompatible with the as-found test valve TR-Nl and 6 psig for TR-N2). When the internal pressures of TR-Nl lift pressure (4.5 psig for and TR-N2 (which were still within the specified normal operating range) exceeded the test valve lift pressure, the valves lifted and caused the differential pressure across the bellows of the sudden pressure relays.

(b) Oil samples from both TR-Nl and TR-N2 were obtained and sent to BPA for anlaysis. The results of these analyses support the final conclusion that no internal faults occurred that would have caused a true sudden pressure relay actuation. This information was available before the transformers were again placed in service.

2. ~ Further Corrective Action (a) The Backup Transformers were inspected for similar sudden pressure relay configurations and no problems were identified. (The Hain and Startup transformer sudden pressure protection is of a different design and does not have an installed test valve).

(b) A formal engineering interface will be established between the Supply System and BPA to coordinate maintenance of the Transformer Yard and other equipment of mutual interest, to improve understanding of the maintenance tests and schedules required, and to establish conf iguration control responsibilities.

(c) The procedure for testing sudden pressure relays will be reviewed to ensure that test valve installation, use and removal is properly addressed.

(d) Transformer oil-sample trending will be established (within the Supply System) to preclude using outdated information during future analysis of oil condition.

NIIC FOIIM SSSA IS@3)

NRC Form 3&A UA. NUCI.EAR REOULATORY COMMISSION I0431 UCENSEE EVENT REPORT (LER) TEXT CONTINUATION APPROVEO OMS NO. SISOMIOl EXPIRES: EISIISS FACILITY NAME ill OOCKET NUMEER Ill LER NUMEER ISI PACE ISI SEOVENIIAL mEVISICN NVM Em NVM

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Washington Nuclear Plant - Unit An HIIC Forrri ~'eI 1171 engineering evaluation 2 o s o will be o o 8 7 0 18 performed on the cover gas system 000 5 OF configuration and operation.

(f) Steps have been taken to strengthen the post-trip review and root cause assessment process. Specifically, Plant Procedure 1.3.5, "Reactor Trip and Recovery," has been evaluated and will be revised to incorporate several planned improvements. In addition, a Management letter has been issued which directs Plant personnel to follow the intent of the changes until such time that the procedure is revised.

~Safet Significance There is no safety significance associated with this event in that Plant protection systems and electrical distribution realignments functioned as design'ed. These events posed no threat to the health and safety of either the public or plant personnel.

Similar Events Hone EIIS Information Text Reference EIIS Reference System ~Com onent Reactor Protection System (RPS) JC Transformer (TR-Hl and TR-H2) EA XFMR Unit Lockouts (86XU, 86XUOA, 86X1U, and 86XlUOA) EA RLY Turbine Control Valve (TCV) JJ V NIIC POIIM SoeA IE441

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WASHINGTON PUBLIC POWER SUPPLY SYSTEM P.O. Box 968 ~ 3000 George N'ashington Way ~ Richland, Washinglon 99352 Docket No. 50-397 July 27, 1987 Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555

. Sub ject: NUCLEAR PLANT NO. 2 LICENSEE EVENT REPORT NO.87-018

Dear Sir:

Transmitted herewith is Licensee Event Report No.87-018 for the WNP-2 Plant.

This report is submitted in response to the report requirements of 10CFR50.73 and discusses the items of reportability, corrective action taken, and action taken to preclude recurrence.

Very truly yours, C.t<. Powers (M/D 927th)

WNP-2 Plant Manager CHP:ac Enclosure Licensee Event Report No.87-018 cc: Hr. John B. Martin, NRC - Region V Hr. R. T. Dodds, NRC Site (H/D 901A)

INPO Records Center - Atlanta, GA Hs. Dottie Sherman, ANI.

ter. D. L. Williams, BPA (H/D 399)