ML20045D919

LER 93-006-00:on 930527,both Core Spray Sys Trains a & B Declared Inoperable When Calibr Procedure Error Resulted in Setpoint Set Nonconservatively.Caused by Failure to Apply Head Correction Factor.Procedure corrected.W/930624 Ltr

ML20045D919
Person / Time
Site:	Vermont Yankee
Issue date:	06/24/1993
From:	Wanczyk R VERMONT YANKEE NUCLEAR POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-006, LER-93-6, NUDOCS 9306300221
Download: ML20045D919 (6)

Text

'

MERMONT YANKEE NUCLEAR POWER CORPORATION

(f 9 - ~ P.O. Box 157, Governor Hunt Road

[W p Vernon, Vermont 05354-0157 O V, - .

~~. (802) 257-7711

,J.v*n,"

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June 24, 1993 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555

REFERENCE:

Operating License DPR-28 Docket No. 50-271 Reportable Occurrence No. LER 93-006 Dear Sirst As defined by 10 CFR 50.73, we are reporting the attached Reportable Occurrence as LER 93-006.

Very truly yours, VERMONT YANKEE NUCLEAR POWER CORPORATION M

Robert J. W czyk Plant Manager cc: Regional Administrator USNRC Region I 475 Allendale Road King of Prussia, PA 19406 e

9306300221 930624 q\

PDR .ADOCK 05000271 S- PDR

- . - - . . - _ .~

NRC Form 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED OM8 NO. 3150-0104 .

(6-89) EXPIRE 8 4/30/92

. ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUESTS 50.0 HR8. FORWARD COMMENTS REOARDINO BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAOEMENT ,

LICENSEE EVENT REPORT (LER) BRANCH (P-530), U.S. NUCLEAR REOULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3160-0104), OFFICE OF MANAOEMENT AND BUDOET, WASHINOTON, DC 20603.

FACILITY NAME (1) DOCKET NO. (2) PACE (3)

VERMONT YANKEE NUCLEAR POWER STATION O l5 l0 l0 l0 l2 l7 l1 0 l1-lOF l 0l 4 TITLE (4) CORE SPRAY SYSTEMS A AND B DECLARED INOPERABLE DUE TO CALIBRATION PROCEDURE ERROR.

EVENT DATE (5) LER NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YEAR SEQ # REVN MONTH DAY YEAR FACI ITY NAMES DOFK1:T No. 8 0 5 0 0 0 0 5 2 7 9 3 9 3 - 0 0 6 - 0 0 0 6 2 4 9 3 0 5 0 0 0 OPERATING THIS REPORT IB SUBMITTED PURSUANT TO REQ'MTS OF 10 CFR $3 CHECK ONE OR MORE (11)

MODE (9) N 20.402(b) 20.405(c) 50.73(a)(2)(iv) 73.71(b)

POWER 20.405(a)(1)(1) 50.36(c)(1) 50.73(a)(2)(v) -

73.71(c)

LEVEL (10) 1 0 0 - - -

20.405(a)(1)(ii) 50.36(c)(2) X 50.73(a)(2)(Vii) OTHER:

.... .. .. 20.405(a)(1)(iii) X 50.73(a)(2)(2) 50.73(a)(2)(viii)(A)

..... ... . . 20.405(a)(1)(iv) 50.73(a)(2)(ii) 50.73(a)(2)(viii)(B)

... .... . 20.405(a)(1)(v) 50.73(a)(2)(iii) 50.73(a)(2)(x)

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NO.

AREA CODE ROBERT J. WANCZYK, PLANT MANAOER Bl0l2 2l5l7l-l7l7l1l1 COMPLETE ONE LINE FOR E ACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYST COMPONENT MTR REPORTABLE CAUSE SYST COMPONENT MFR REPORTABLE TO NPRDS . . . TO NPRDS ...

D B O P D I B B O 8 0 YES .... ...

SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MO DAY YR SUBMISSION DATE (15)

YES (If yea, complete EXPECTED SUBMISSION DATE) XX NO NA ABSTRACI (Limit to 1400 spaces, i.e., approx. fif teen single-space typewritten lines) (16) .

At approximately 2030 on 5/27/93, with the plant operating at 100% steady state power, both the A and B Core Spray System trains were declared inoperable based upon the identification of a calibration procedure error which resulted in the setpoint of the differential pressure indicating svitches (DPIS-14-43A/B) for Core Spray Sparger Break Detection being set non-conservatively. The procedure was revised, instruments recalibrated, and the A and B Core Spray Systems vere returned to service. The decision by plant management to declare both A and B trains of the Core Spray System inoperable was based upon a Technical Specification requirement, integrity of the Core Spray Sparger was not in question.

Due to dynamic forces acting on the pressure switch during plant operation, a head correction is factored into the calibration of the pressure indicator. However, when the procedure instructed the technician to set the switch setpoint, it did not incorporate the offset into the value to be read from the measuring and test equipment (H&TE).

Corrective actions include: a review the Technical Specification setpoint for Core Spray Sparger High Pressure; consideration of a replacement for the existing Barton 288 instrument;

, review of other procedures for a similar situation.

+ -

r s-_w - _ _ _ . _ _ _ _ _ .

~ _ , _

e NRC Form 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED OM8 NO. 3150-0104 (6-89) EXPIRE 8 4/30/92

. ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUESTS 50.0 HR8. FORWARD COMMENTS REGARDING BURDEN' ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT LICENSEE EVENT REPORT (LER) BRANCH (P-530), U.S. NUCLEAR REOULATORY TEXT CONTINUATION COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3160-0104), OPrICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20603.

FACILITY NAME (1) DOCKET NO (2) LER NUMBER (6) PAGE (3)

YEAR SEQ # REV #

VERMONT YANKEE NUCLEAR POWER STATION O 5 0 0 0 2 7 1 9l3 -

0l0l6 -

0l0 0 2 Cr 0 4 TEXT (If more space is required, use additional NRC Form 366A) (17)

DESCRIPTION At approximately 2030 on 5/27/93, with the plant operating at 100% steady state power, both the A and B Core Spray System (BG*) trains vere declared inoperable based upon the identification of a calibration procedure (OP 4347) error which resulted in the setpoint of the differential pressure indicating switches (DPIS-14-43A/B)(PDIS*) for Core Spray Sparger Break Detection being set non conservatively. The procedural error was identified following the discovery of DPIS-14-43A reading < 0 psid by an auxiliary. operator on 5/25/93 and the subsequent Work Order scoping effort. The procedure was revised to correct the non-conservative condition and the B Core Spray DPIS was recalibrated and returned to operable status at 2342, the A Core Spray DPIS was recalibrated and returned to service at approximately 1325 on 5/28/93. The decision by plant management to declare both A and B trains of the Core Spray System inoperable was based upon the Technical Specification requirements of Table 3.2.1, integrity of the Core Spray Sparger was not in question.

The Core Spray Sparger Break Detection System includes one Barton 288 differential pressure switch for each train. The DPIS low pressure side is connected to the Core Spray Piping inside the dryvell and monitors pressure inside the Core Spray Sparger (refer to Figure 1). The high pressure side is connected to the Standby Liquid Control (SLC)(BR*) above core plate piping.

Normally, the DPIS senses differential pressure (dP) across the reactor core, at VY this correlates to approximately -1.9 psid near rated pover/ flow. The system is designed such that if a break occurs in the Core Spray Sparger Piping between the reactor vessel vall and the core ,

shroud, pressure is no longer being sensed across the core but across the_ core shroud. Since this pressure differential is greater, the pressure switch can be set to actuate at an increasing value and provide an alarm in the Main Control Room.

Technical Specifications Table 3.2.1 lists a Core Spray Sparger High Pressure Setpoint of I 5 psid. Due to dynamic forces encountered during plant operation, the calibration procedure requires an offset of -1.9 psid to be included in the calibration of the dPIS scale. When the procedure instructed the technician to set the switch setpoint, it did not incorporate the of fset into the value to be read from the measuring and test equipment (H&TE). The result was that instead of setting the alarm switch at 4 +/-0.3 psid, the switch was being set at approximately 5.9 psid (+/-0.3). This was outside of the 1 5 psid Technical Specification setpoint.

A concern was raised during the review of this event relative to the appropriateness of'the Technical Specification Setpoint of f 5 psid. GE SIL 300 (September 1979) was issued to utilities who had expressed a concern about the downscale reading on the Core Spray Sparger Break Detection differential pressure indicating switches near full power operation. The concern being that it was not a good practice to have an instrument normally pegged downscale.

The SIL provided recommendations to utilities on how to respond to the unexpected downscale j condition (original plant specific documentation shows +4 psid would be normal operating pressure), which Vermont Yankee did address. Included in the SIL was a table that indicated the calculated maximum expected change in differential pressure across the core shroud to be 4 psid at VY. Since this is the pressure that the sparger break detection system would experience during a break, the appropriateness of the Technical Specification value of I 5

,- psid is being questioned.

• Energy Industry Identification System (EIIS) Identifier

a NRC Form 366A U.S. NUCLEAR REOULATORY COMMISSION APPROV2D OM8 NO. 3150-0104 (G-89) EXPIRE 8 4/30/92

, ESTIMATED BURDEN PER RESPON8E TO COMPLY WITH THIS INFORMATION COLLECTION REQUESTS 50.0 HR8. FORWARD COMMENTS REOARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT LICENBEE EVENT REPORT (LER) BRANCH (P-530), U.S. NUCLEAR REGULATORY TEXT CONTINUATION COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3160-0104), OrrICE OF MANAGEMENT AND BUDOET, WASHINGTON, DC 20603.

FACILITY NAME (1) DOCKET NO (2) LER WUMBER (6) PAGE (3)

YEAR SEQ R REV N I V2RMONT YANKEE NUCLEAR POWER STATION 0 5 0 0 0 2 7 1 9l3 -

0l0l6 -

0l0 0 3 Or 0 4 TEXT (If more space is required, use additional NRC Form 366A) (17)

DESCRIPTION fcontinued)

The dPIS switches were both reset to alarm at less than 4 psid. It currently appears that the significance of the value in the SIL 300 table was not recognized during the original SIL review.

[.A.USE OF EVENT The root cause of the A & B Core Spray Systems being declared inoperable is due to the procedural error that did not apply the head correction factor to the H&TE reading when setting the alarm point.

Contributing Causes:

The response of the instrumentation originally specified by GE was not as originally expected. Review of the original plant documentation shows that the expected indication during normal power / flow operation was +4 psid. Instead of the indicator reading approximately +4 psid at rated power, it read downscale (correspond ng to-approximately -1.9 psid). SIL 300 vas issued by GE to address and respond to this situation as utilities were concerned with the DPIS instrument constantly being pegged downscale during operation. VY responded to the SIL and included the appropriate offset to the indicator to compensate for the rated power conditions. However, the corresponding head correction was not applied to the H&TE reading used to set the instrument alarm point.

Relative to the potentially inappropriate Technical Specification Setpoint of 4 5 psid, further evaluation of SIL 300 Table 1 should have occurred following the SIL issuance to determine the implications that the maximum calculated shroud dP of 4 psid had on the VY Technical Specification. However, the focus of the SIL was the downscale pressure switch indication. j

.MALYSIS OF EVENT I The safety implication associated with the procedural error is that should a break in the Core Sb 'ay Sparger Piping have occurred, the instrument vould not have provided the alarm funct) a. The safety significance of this is considered to be minor since the Core Spray Sparger Piping is inspected each outage to verify physical integrity.

There vere negligible safety implications resulting from declaring both trains of Core Spray inoperable. The B Core Spray System was declared inoperable for approximately 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />, the A Core Spray for approximately 16.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />. All other Emergency Core Cooling Systems remained >

operable during this period. It should be noted that the inoperable declaration of both A and i B Core Spray Systems was based upon a Technical Specification requirement. Based upon the fact that neither of the DPIS switches indicated a positive increase in pressure, it is concluded that the Core Spray Sparger Piping was intact and both Core Spray Systems were capable of perforning their safety function, if required during the inoperable period.

• Energy Industry Identification System (EIIS) Identifier

,~ - - . -. __. .. - ._- . .

a NRO Form 366A U.S. NUCLEAP REOULATORY COMMISSION APPROVED OMS NO. 3150 0104 (4-89) EXPIRE 8 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUESTS 50.0 HRS. FORWARD COMMENTS REOARDINO BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAOEMENT LICENSEE EVENT REPORT (LER) BRANCH (P-530), U.S. NUCLEAR REOULATORY TEXT CONTINUATION COMMISSION, WASHINOTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3160-0104), OFFICE OF MANAOEMENT AND BUDCET, WASHINOTON, DC 20603.

FACILITY NAME (1) DOCKET NO (2) LER NUMBER (6) PAOE (3)

YEAR 82Q # REV N VERMONT YANKEE NUCLEAR POWER STATION O 5 0 0 0 2 7 1 9l3 -

0l0l6 -

0l0 0 4 OF 0 4 TEXT-(If more space is required, use additional NRC Form 366A) (17)

EORRECTIVE ACTIONSi Immediate:

1. Upon discovery of the procedural error, the procedure was immediately corrected, and the instruments were recalibrated. Additionally, following discussions with GE (G080*), the DPIS's vere set to alarm at a f 4 psid i.hange from the full power indication.

2. An independent engineering reviev was performed on the procedure changes.

Long-Term:

1. A review of the current Technical Specification setpoint of I 5 psid for Core Spray Sparger High Pressure vill be performed. A Technical Specification Amendment vill be submitted, if required. This review vill be completed by 8/31/93.

2. Consideration vill be given to replacement of the existing Barton 288, 0-20 psid instrument with an instrument better suited for the application. A recommendation and proposed implementation schedule vill be provided by 10/31/93.

3. Other procedures are in the process of being reviewed for a similar situation. This reviev vill be completed by 9/1/93.

4. The Core Spray Break Detection System design basis vill be reconstituted as part of the corrective action effort.

ADDITIONAL INFORMATJON:

No similar event, where a procedural error resulted in the declaration of both trains of an ESF System inoperable, has been reported to the Commission in the past five years.

• Energy Industry Identification System (EIIS) Identifier

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