05000368/LER-1999-001, :on 990108,TS Requirements for as-lift Settings of MSSV Were Not Met.Caused by Errors in Determination of Effective Seating Area by Vendor During Test Device Qualification.Replaced All Mssvs.With

:on 990108,TS Requirements for as-lift Settings of MSSV Were Not Met.Caused by Errors in Determination of Effective Seating Area by Vendor During Test Device Qualification.Replaced All Mssvs.With

ML20207M095
Person / Time
Site:	Arkansas Nuclear
Issue date:	03/09/1999
From:	Tracy Scott, Vandergrift J ENTERGY OPERATIONS, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
2CAN039902, 2CAN39902, LER-99-001, LER-99-1, NUDOCS 9903180380
Download: ML20207M095 (8)

LER-1999-001, on 990108,TS Requirements for as-lift Settings of MSSV Were Not Met.Caused by Errors in Determination of Effective Seating Area by Vendor During Test Device Qualification.Replaced All Mssvs.With

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv), System Actuation 10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(1) 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2)(x)
3681999001R00 - NRC Website

text

'

Entergy operations. inc.

1443 SR 333 RusseMe. AR 72801 5

Tel 50i 858-5000 March 9,1999 2CAN039902 U. S. Nuclear Regulatory Commission Document Control Desk Mail Station OPl-17 Washington, DC 20555 I

Subject:

Arkansas Nuclear One - Unit - 2 Docket No. 50-368 License No. NPF-6 Licensee Event Report 50-368/1999-001-01

{

Gentlemen:

1 In accordance with 10CFR50.73(aX2XiXB), enclosed is the subject report concerning 4

Main Steam Skiety Valves.

Very truly yours,

,g,

~

l Jimmy D. Vandergrift Director, Nuclear Safety JDV/tfs Q/

l enclosure 1.700@

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9903180380 990309 PDR ADOCK 05000368 PDR S

U. S. NRC March 9,1999 2CAN039902 PAGE 2 ccf Mr. Ellis W. Merschoff Regional Administrator U. S. Nuclear Regulatory Commission Region IV 611 Ryan Plaza Drive, Suite 400 l

Arlington, TX 76011-8064 NRC Senior Resident Inspector Arkansas Nuclear One P.O. Box 310 London, AR72847 l

Institute of Nuclear Power Operations 700 Galleria Parkway Atlanta, GA 30339-5957 l

1 l

m

NRC rusm 366 U.S. NUCLEAR REGULATORY C(NWilS$10N APPROVED BY CNet No. 3150-0104 (5;92)

EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH l

$y"F0""A $ j'

$ "gST g NR y

y LICENSEE EVENT REPORT (LER)

THE INFORMATION AIS RECr* I MANAGEMENT BRANCH (MNBB 7714), U.S. NUCLEAR JLATORY Copst!SSION, i

20555000)500104),

WASHINGTON, DC AND TO THE PAPERWORK REDUCTION PROJECT (31 OFFICE OF MANAGEMENT AND BUDGET. WASHINGTON, DC 20503.

I Arkansas Nuclear One - Unit 2 FACILITY NAME (1)

DOCKET NUMBER (2) l PAGE (3) 05000368 I

1 of 6 IErrorsInTheDeterminettonofEffectiveSeatingAreaByTheVendorDuring TITLE (4) Technical Specifications Requirements For As-Lef t Lif t settinBs of Nein Steam Safety Valves Were Not Met Due To l

EVENT DATE (5) l LER NUMBER (6)

REPORT DATE (7)

OTHER FACILITIES INVOLVED (8) l MONTH SEQUENTIAL REVISION DAY l YEAR l YEAR MONTH DAY YEAR InsqBER BRNEBER 01 08 1999 1999 001 01 03 09 1999 IOPERATING l l THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFRs (Check or,e or more) (11) i IquDE (9)

I 1 l 20.402(b) 20.405(c) 50.73(a)(2)(iv) 73.71(b)

POWER l

20.405(a)(1)(1) 50.36(c)(1) 50.73(a)(2)(v) 73.71(c)

EVEL (10 20.405(a)(1)(lt) 50.36(c)(P) 50.73(a)(2)(vil)

OTHER 20.405(a)(1)(iff)

X 50.73(a)(2)(1) 50.73(a)(2)(vill)(A)

Specify in 20.405(e)(1)(Iv) 50.73(a)(2)(if) 50.73(a)(2)(viii)(B)

Abstract Below 20.405(a)(1)(v) 50.73(a)(2)(fil) 50.73(a)(2)(x) and in Text j

LICENSEE CONTACT FOR TM18 LER (12) lNAME TELEPHONE NUMBER (Include Area Code) i Thames F. Scott, Nuclear Safety and Licensing Specialist 501 858-4623 l

CCNW8LETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE

SYSTEM COMPollENT MAllUFACTURER SYSTEM COMPONENT MANUFACTURER SUPPLEMENTAL REPORT EXPECTED (14)

EXPECTED MollTH DAY YEAR I

YES NO SUBMISSION (If yes, complete EXPECTED SUBM!$$10N DATE)

X DATE (15)

ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 sinBle-spaced typewritten lines) (16)

Prior to a scheduled refueling outage, in situ testing revealed that four of ten Main Steam Safety Valves (MSSVs) had as-found lift settings greater than three percent above their setpoints. Each valve was left with a lift setting within an indicated plus or minus one percent of the required setpoint before testing another valve. A Crosby Set Pressure Verification Device (SPVD) was being used for the first time at ANO for MSSV testing. The root cause evaluation determined that errors in the determination of the effective seating area by the vendor during qualification of the SPVD on ANO-2 MSSVs resulted in the indicated lift settings being higher than the actual values.

The corrected as-found lift setting was out of tolerance for only one MSSV.

The test device error resulted in the final as-left lift settings of four MSSVs being outside the as-left Technical Specifications (TS) limit of plus or minus one percent of the specified setpoint. Two of those valves were in that condition for slightly longer than allowed by the TS Action requirement. All MSSVs were subsequently replaced with valves that had been inspected and certified on steam at an off-site facility. Other factors contributing to lift point reliability were also determined during the root cause evaluation.

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.a LICENSEE EVENT REPORT (LER)

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(""es m ), u.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555-0001, AND TO THE PAPERWDRK REDUCTION PROJECT (3150-0104),

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FACILITY NAME (1)

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PAGE (3)

YEAR SEQUENTIAL REVISION NUMBER NUMSER Arkansas Nuclear One - Unit 2 05000368 2 0F 6 TEXT fff =nr..aer.

In renutrad um maatttonal ennt nf une rare u s (17) l A.

Plant Status i

At the time Main Steam Safety Valve (MSSV) [SB] testing was initially conducted, Arkansas Nuclear One Unit 2 (ANO-2) was operating at approximately 75 percent power in coast-down for scheduled refueling outage 2R13. The root cause evaluation was completed during the outage.

B.

Event Description

Two of ten MSSVs had as-left lift settings outside plus or minus one percent of specified setpoint for longer than allowed by Technical Specifications (TS).

l i

ANO-2 has five MSSVs per header.

During Modes 1, 2, and 3, TS 3.7.1.1 requires the valves to have lift settings within plus or minus three percent of the specified setpoints. Additionally, if lift settings are found outside a plus or minus one percent tolerance band,.sey are required by TS to be reset to within that tolerance. On January 7 and 8, 1999, all of the valves were tested in situ just prior to the start of a scheduled refueling outage.

Four were found with indicated initial lift settings exceeding three percent of the lift setting specified by TS.

Results of the initial as-found tests are provided below. All pressures are in psig.

Tag Number Setpoint As-Found Percent Deviation 2PSV-1002 1078 1106

+2.6 2PSV-1003 1105 1155

+4.5 2PSV-1004 1105 1142

+3.4 2PSV-1005 1132 1160

+2.5 2PSV-1006 1132 1159

+2.4 2PSV-1052 1078 1120

+3.9 2PSV-1053 1105 1147

+3.8 2PSV-1054 1105 1117

+1.1 2PSV-1055 1132 1137

+0.5 2PSV-1056 1132 1156

+2.2 All MSSVs were adjusted as necessary and re-tested until two consecutive lifts were within an indicated plus or ndnus one percent of the specified setpoint.

An Event Response Team was assembled to determine the root cause of the high initial indicated MSSV lift pressures and determine appropriate corrective l

actions. The team was composed of ANO personnel from System Engineering, j

Maintenance Engineering, Design Engineering, and In-House Events Analysis j

organizations.

Following plant vooldown, all MSSVs were removed from the steam headers.

Six valves were sent to NWS Technologies for testing, inspection, and refurbishment.

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PAGE (3)

YEAR SEQUENTIAL REVISION NUMBER NUMBER Arkansaa Nuclear One - Unit 2 05000368 3 0F 6 g

TEXT fif ere

a=e

in ranuirna on. maattinnat ennt.. n# use rar. U m (17)

At NWS, a modification, developed as a corrective action from the previous outage, was incorporated in each valve. This modification included increasing the guide bearing clearances and replacing the flat seat disc insert with a Flexi-Disc design.

Prior to being modified, two of the six valves were sent to Crosby, the valve manufacturer, for additional testing of the Set Pressure Verification Device (SPVD) test device and to determine if the MSSV effective seating area value was correct for the flat seat disc insert design. This area had been used in the determination of the 2R13 initial MSSV lift settings.

From this testing it was determined that the test device, a Crosby SPVD used at ANO for the first time for the January 1999 testing, was qualified using an incorrect value for the MSSV effective seating area. This resulted in indicated lift settings being 1.1 to 1.2 percent higher than actual pressures. The corrected percent deviations from setpoints were:

Tag Number As-Found As-Left 2PSV-1002

+1.6

- 1.1 2PSV-1003

+3.3

- 1.2 2PSV-1004

+2.2

- 0.1 2PSV-1005

+1.2

- 0.6 2PSV-1006

+1.2

- 0.7 2PSV-1052

+2.8

- 0.8 2PSV-1053

+2.6

- 0.2 2PSV-1054 0.0

- 1.9 2PSV-1055

- 0.7

- 1.2 2PSV-1056

+0.9

- 0.7 The as-left percent deviations are for the final lifts on January 7 and 8, 1999. The ANO practice is to require two consecutive lifts within plus or minus one percent for as-left lift points on MSSVs. The corrected lift settings resulted in deviations for two valves, 2PSV-1005 and 2PSV-1052, below minus one percent for the initial as-left lift. The second as-lift for these valves was within the plus or minus one percent tolerance. All six of the valves initially sent to NWS were certified on steam lifts at the testing facility.

Four spare MSSVs were also sent to NWS for re-certification. The Flexi-Disc modification had been installed in the four spare valves during the previous operating cycle. The as-left lift mettings at the completion of outage 2R13 were determined to meet TS requi aments using tests conducted on steam, not the SPVD, at the NWS test facility.

C.

Root Cause The SPVD was used at ANO for the first time in 2R13 as a corrective action from the previous refueling outage.

~t was intended to improve the accuracy of MSSV lift pressure determinations.

The SPVD is an auxiliary lift device that applies an upward force on the MSSV spindle. As force is applied, the downward force applied on the disc insert is reduced to the point where the valve begins to open. At this time, the SPVD tskes a snapshot of the load cell force and the steam header pressure. The SPVD uses the steam header pressure, along with the force and effective seating area, to determine valve lift pressure.

The MSSV effective seating area must be determined empirically at a test facility. The ANO-2 SPVD qualification testing was performed by a WRC FORM 366A (5 92)

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YEAR SEQUENTIAL REVISION NUMBER NUMBER i

Arkansas Nuclear One Unit 2 05000368 1999 001 01 I

TEXT ttf enen.a -- la ranutrad uma additional enntaa of sine rnem xAAas (17}

Crosby representative at NWS Technologies in September 1998 using two spare ANO-2 MSSVs.

Crosby analytically determined an effective seating area value as a starting point for SPVD certification. Testing results from one valve that were close to the analytically determined value were accepted for l

certification.

Results from tests on the other valve were discounted by l

Crosby Engineering due to several changes that occurred during testing.

l Differences in test results from the two valves were not adequately l

investigated and a low, inaccurate effective seating area value was selected.

l Subsequently, a report was received from Crosby on February 15, 1999, documenting that an incorrect seating area had been previously determined that caused errors in SPVD indication of 2R13 MSSV lift pressures. The root cause of this condition is attributed to human performance errors by Crosby during test device certification.

Two contributing factors were determined for 2PSV-1003 having a high initial as-found lift setting. The first is that the MSSV valve design provides for a j

relatively large area for foreign material to enter the valve internals at the

]

guide bearing area.

Thia valve was found to have a significant amount of j

foreign material in the guide bearing area. The second is that the design provides tight guide bearing clearance. These factors combined to cause friction between the spindle and guide bearing. The foreign material is believed to have originated from welding and grinding activities in the vicinity during the previous refueling outage. This was the only MSSV that remained on the header during the last refueling outage. A minor additional contribution to the high lift pressure could have resulted from excessive seat leakage that caused lower body temperatures.

I As part of the root cause investigation, disc inserts and nozzles from two MSSVs were sent to Southwest Research Institute for metallurgical evaluation

'i of the seating surfaces.

The evaluation concluded that use of stainless steel (SA 182 Grade F316) for both the disc insert and nozzle could contribute to high initial lift values because the materials are prone to galling.

Slight movement of the parts in contact can result in adhesion wear known as " micro-welding" that can be an impediment to separation of the seating surfaces.

Evidence of galling was observed on he seating surfaces due to a small amount I

of relative motion (approximately 0.001 inch) between the seating surfa:es.

l This factor is believed to be a minor contribution to the as-found lift pressures being high.

Conversion of the MSSVs to the Flexi-Disc design j

provides a change in material of the disc insert to ASME SB-637 Grade 718 I

which should improve the resistance to galling.

D.

Corrective Actions

All ten MSSVs installed at the completion of outage 2R13 had lift settings verified to be within Technical Specifications requirements by lifts on steam 1

)

at the NWS test facility rather than the SPVD.

All ten MSSVs installed at the completion of outage 2R13 received several inspections. The guides and guide bearings were inspected for wear, corrosion, scratches, galling, or other indications of binding.

Inspections i'

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YEAR SEQUENTIAL REVISION NUMBER WUMBFR Arkanses Nucteer One - Unit 2 05000368 5 0F 6 g

TEXT fff mar

=a=*a in raautrad na. Mitinnat enntaa nf unta rnen m (17) for evidence of wear or binding were also performed on bearing adapters, upper spring washers, discs, nozzle seats, and the spindle / adjusting bolt area. The clearances between spindles and guide bearings were measured.

Parts were replaced or refurbished, as necessary.

During these activities, guide bearing clearances were increased and Flexi-Disc conversions were installed on each valve.

The two MSSVs tested at Crosby in January 1999 were modified and re-tested with the Flexi-Dise design to determine a corrected effective seating area appropriate for the valves currently installed in ANO-2.

E.

Safety Significance

Following the initial as-found tests, an evaluation of events of interest analyzed in the Safety Analysis Report (SAR) wa.s conducted.

These events are Feedwater Line Break (FWLB), Loss of Condenser Vacuum (LOCV), and Small Break Loss of Coolant Accident (SBLOCA). The evaluation concluded that, with the indicated as-found lift pressures, sufficient relief capacity was available to ensure that the primary and secondary design limits as well as the Emergency Core Cooling System performance criteria were not violated.

Therefore, the MSSVs would have adequately performed their required safety functions during the previous cycle if they did not lift until the indicated pressures.

The corrected as-found values resulted in only one MSSV lift point not meeting the plus or minus three percent tolerance allowed by Technical Specifications.

The impact of the actual as-found condition of the MSSV lift pressures is bounded by the evaluation performed for the indicated values. NUREG-1432 Revision 1, " Standard Technical Specifications - Combustion Engineering Plants," states that the purpose of resetting the MSSVs to within plus or minus one percent during the surveillance is to allow for drift.

Even though some MSSV lift points were outside the required as-left tolerance, they would have been capable of fulfilling their required safety functions for the duration of the condition. As described below, two MSSVs on one Steam Generator (SG) outside the specified as-left tolerance (but within three percent of the setpoint) exceeded the TS allowable time to place the plant in Mode 3 by approximately two and one half hours. This condition is judged to have had minimal safety significance.

F.

Basis for Reportability Technical Specification 3.7.1.1 requires that all MSSVs have lift settings as specified in Table 3.7-5.

The footnote to Table 3.7-5 requires that if lift settings are found outside of plus or minue one percent of the specified setpoint the setting shall be adjusted to within plus or minus one percent of the setpoint shown in the table. Action (a) of TS 3.7.1.1 allows for continued operation in Mode 1 with one or more inoperable MSSVs provided that, within four hours either the inoperable valve is restored to an operable status or the Linear Power Level - High trip setpoint is reduced per Table 3.7-1; otherwise, the plant must be in at least Hot Standby (Mode 3) within4 l

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~

NLMBER NLMBER Arkansas Nuclear One Unit 2 05000368 6 0F 6 g

TEXT fff unre =ae=

la rarmite.d um maattinnat ennt.a nf une rne m s (17) the next six hours. Table 3.7-1 lists the maximum allowable Linear Power Level - High trip setpoint for one inoperable MSSV on any SG as 91.0 percent.

For two inoperable MSSVs on any SG, the maximum allowable trip setpoint is 67.7 percent.

Prior to commencement of MSSV testing, the Linear Power Level - High trip setpoint was reduced to below 91 percent, a value allowing continuous operation with one MSSV per header inoperable.

During testing on January 8, 1999, valve 2PSV-1054 was left lower than the minus one percent tolerance at 1119 hours0.013 days <br />0.311 hours <br />0.00185 weeks <br />4.257795e-4 months <br />. Another valve for that SG, 2PSV-1055, was inoperable for testing at 1135 hours0.0131 days <br />0.315 hours <br />0.00188 weeks <br />4.318675e-4 months <br /> and was left out of tolerance low at the completion of testing.

The two valves not being reset in accordance with the footnote of Table 3.7-5 can be interpreted to cause entry into TS 3.7.1.1 Action (a).

The lift pressures were thought to be within tolerance, and trip setpoints were not reduced below the maximum allowable value for two MSSVs inoperable on the same SG in accordance with Table 3.7-1.

The action required the plant to be in Mode 3 by 2135 hours0.0247 days <br />0.593 hours <br />0.00353 weeks <br />8.123675e-4 months <br /> on January 8, 1999. The plant entered Mode 3 at 0004 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> on January 9, 1999.

Since the allowable outage time was exceeded, this condition constituted operation prohibited by Technical Specifications. The testing sequence resulted in the two MSSVs on the other header that were left out of tolerance (2PSV-1002 and 2PSV-1003) not both being inoperable for longer than the allowable outage time. This report is being submitted in accordance with 10CFR50.73(a) (2) (1) (B).

G.

Additional Information

The ANO-2 MSSVs are model HA-65-FN, size 8T10x10, manufactured by Crosby Valve and Gage Company (Manufacturer Code C710).

There have been no previous timilar events reported by ANO as Licensee Event Reports.

Since this supplement is a major revision that affected every section, revision marks in the margin provide no useful information and have not been included.

Energy Industry Identification System (EIIS) codes are identified in the text as [XX).

i i

i

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