ML18100A655

LER 93-015-00:on 930913 & 16,BAST 12 Level Indicator Declared Inoperable Due to False Level Indications.Caused by Design of Bast Level Indication Sys.Design Change to Reduce Boron Concentration Will Be implemented.W/931007 Ltr

ML18100A655
Person / Time
Site:	Salem
Issue date:	10/07/1993
From:	Pastva M, Vondra C Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-015, LER-93-15, NUDOCS 9310180256
Download: ML18100A655 (6)

Text

e PS~G Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Generating Station October 7, 1993 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Dear Sir:

SALEM GENERATING STATION LICENSE NO. DPR-70 DOCKET NO. 50-272 UNIT NO. 1 LICENSEE EVENT REPORT 93-015-00 This Licensee Event Report is being submitted pursuant to the requirements of the Code of Federal Regulation 10CFR50.73(a) (2) (i) (B). This report is required to be issued within thirty (30) days of event discovery.

Sincerely yours,

c. A V ndra General Manager -

Salem Operations MJPJ:pc Distribution 150056 The power is in vour h:::i nrk 9310180256 6~588~72 PDR ADOC~ PDR 95-2189 REV 7-92 s

NRC FORM:;&& U.S. NUCLEAR REGULATORY COMMISSION 16-89) APPROVEO OMB NO. 3150-0104 EXPIRES: 4/30/92 ESTIMATED BURDEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARD LICENSEE EVENT REPORT (LERI COMMENTS REGARDING BURDEN ESTIMATE TO THE RECORDS AND REPORTS MANAGEMENT BRANCH IP-530). U.S. NUCLEAR REGULATORY COMMISSION. WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT 13150-01041, OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON. DC 20503.

FACILITY NAME 11) DOCKET NUMBER 12) I PAGE 13)

Salem TITLE 141 Generatin~ Station - Unit 1 0 I 5 I 0 I 0 I 0 I 2 17 I 2 1 OF 0 15 I T/S 3.0.3 Entries: Inooerability Of 12 BAST Level Indication With '

11 BAST Out Of Service.

EVENT DATE 151 LEA NUMBER 161 REPORT DATE 17) OTHER FACILITIES INVOLVED 181 MONTH DAY YEAR YEAR %t?SE~~~~~~L tt ~~~~~~ MONTH DAY YEAR FACILITY NAMES DOCKET NUMBERISI o19 113 9 3 9 I 3 - o I l Is - oIo 1 Io o I 1 91 3 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE R~QUIREMENTS OF 10 CFR §: (Ch*ck on* or mar* of th* following} 1111 POWER MODE 191 LEVEL 1101 I

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LICENSEE CONTACT FOR THIS LER 1121 60.73loll2llviiillBI 50.731*112llxl NAME TELEPHONE NUMBER AREA CODE M. J. Pastva. Jr. - LER Coordinator 6 I 0 Iq 3 I ~ I q I *I 'i I 11 61 'i COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT 1131 CAUSE SYSTEM COMPONENT MANUFAC-TURER I I I I I I I I I I I I I I 1 I I 1 I I I I I I I I I I SUPPLEMENTAL REPORT EXPECTED 114) MONTH DAY YEAR EXPECTED SUBMISSION n YES (If yos. complot* EXPECTED SUBMISSION DATE}

DATE 1151 I I I ABSTRACT (Limit to 1400 SfNICOS, i.a., approxim*t11ly fiftotJn singltJ*spactJ typewrittan lines} (16) on 9/13/93, at 0137 hours0.00159 days <br />0.0381 hours <br />2.265212e-4 weeks <br />5.21285e-5 months <br />, and 9/16/93, at 0935 hours0.0108 days <br />0.26 hours <br />0.00155 weeks <br />3.557675e-4 months <br />, the 12 Boric Acid storage Tank (BAST) level indicator was declared inoperable due_ to false level indications. In each case 11 BAST was unavailable, Technical Specification (TS) Table 3.3-11 could not be met, and action associate~

with TS 3.0.3 was entered *.

• Following each event, TS 3.0.3 was then exited (at 0210 hours0.00243 days <br />0.0583 hours <br />3.472222e-4 weeks <br />7.9905e-5 months <br /> on 9/13/93, and at 1015 hours0.0117 days <br />0.282 hours <br />0.00168 weeks <br />3.862075e-4 months <br /> on 9/16/93) upon restoration of 12 BAST level indicator to service. The root cause of each event is design of the BAST level indication system. BAST level indication failures have been a recurring problem at both Salem Units and result from bubbler tube blockage. Past corrective actions to this design problem have been marginally effective. Both events resulted from blockage of the 12 BAST level indicator bubbler tube. Following each event, the bubbler tube was blown down to remove blockage and level indication returned to normal. The recurring task for blowdown of the bubbler tubes on each unit will be revised to specify use of Control Air. A design change, which includes reducing the BAST boron concentration to 4% to help minimize boron precipitation in the tank level indicator bubbler tube, is scheduled to be implemented. A similar Unit 2 design change will also be implemented.

NRC Form 366 16-89)

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 93-015-00 2 of 5 PLANT AND SYSTEM IDENTIFICATION:

Westinghouse - Pressurized Water Reactor Energy Industry Identification System (EIIS) codes and Institute of Electrical and Electronics Engineers (IEEE) function identifiers are shown in the text as {xx/xx}

IDENTIFICATION OF OCCURRENCE:

Technical Specification 3.0.3 Entries; Inoperability of 12 Boric Acid Storage Tank (BAST) Level Indication With 11 BAST Out of Service Event Dates: 9/13/93 and 9/16/93 Report Date: 10/7/93 This report was initiated by Incident Report Nos.93-374 and 93-378.

These events are reportable to the NRC per 10CFR 50.73(a) (2) (i) (B) due to entering Technical Specification (TS) 3.0.3.

CONDITIONS PRIOR TO OCCURRENCE:

9/13/93: Mode 1 Reactor Power 100% - Unit Load 1110 MWe 9/16/93: Mode 1 Reactor Power 100% - Unit Load 1095 MWe In each case, 11 BAST was cleared and tagged for maintenance.

DESCRIPTION OF OCCURRENCE:

At 0137 hours0.00159 days <br />0.0381 hours <br />2.265212e-4 weeks <br />5.21285e-5 months <br /> on September 13, 1993, following recurring (weekly) blowdown of the tank level transmitter bubbler tube, and again at 0935 hours0.0108 days <br />0.26 hours <br />0.00155 weeks <br />3.557675e-4 months <br /> on September 16, 1993, the 12 BAST level indicator {CA/LI}

was declared inoperable due to false high level indications. In each case, required level was maintained in 12 BAST; however, because the 11 BAST was unavailable, Action 3 of TS Table 3.3-11 could not be met, and action associated with Technical Specification 3.0.3 was entered.

Following each event, TS 3.0.3 was then subsequently exited (at 0210 hours0.00243 days <br />0.0583 hours <br />3.472222e-4 weeks <br />7.9905e-5 months <br /> on September 13, 1993, and at 1015 hours0.0117 days <br />0.282 hours <br />0.00168 weeks <br />3.862075e-4 months <br /> on September 16, 1993) upon restoration of the 12 BAST level indicator to service.

In MODES 1, 2, AND 3, TS 3.3.3.7 requires two (2) OPERABLE BAST solution level indicators (one/tank). With one level indicator inoperable, Action 3 of TS Table 3.3-11 applies:

"With the number of OPERABLE channels one less than the Required Number of Channels shown in TS Table 3.3-11, operation may

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 93-015-00 3 of 5 DESCRIPTION OF OCCURRENCE: (cont'd) proceed provided that the Boric Acid Tank associated with the remaining OPERABLE channel satisfies all requirements of TS 3.1.2.8.a."

TS 3.1.2.8 states:

"Each of the following borated water sources shall be OPERABLE:

a. A boric acid storage system and at least one associated heat tracing system with:

1. A minimum contained volume of 5106 gallons,

2. Between 20,000 and 22,500 ppm of boron, and,

3. A minimum solution temperature of 145°F.

b. The refueling water storage tank with: "

TS 3.0.3 states:

"When a Limiting Condition for Operation is not met except as provided in the associated ACTION requirements, within one hour action shall be initiated to place the unit in a MODE in which the specification does not apply by placing it, as applicable, in:

1. At least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />,

2. At least HOT SHUTDOWN within the following 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, and

3. At least COLD SHUTDOWN within the subsequent 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.

Where corrective measures are completed that permit operation under the ACTION requirements, the ACTION may be taken in accordance with the specified time limits as measured from the time of failure to meet the Limiting Condition of Operation.

Exceptions to these requirements are stated in the individual specifications."

ANALYSIS OF OCCURRENCE:

The BAST (with the transfer pumps) are part of the boration subsystem of the Chemical and Volume Control System (CVCS). This subsystem ensures negative reactivity control during each mode of facility operation. Required components include two (2) borated water sources, two (2) BASTs and the Refueling Water Storage Tank (RWST).

Either BAST contains sufficient volume to support one.cold shutdown with the most reactive control rod withdrawn. These tanks contain 12 weight % boric acid maintained at a temperature of 175°F. The BAST level indicator sensing design employs a nitrogen flow bubbler tube, which opens near the tank bottom, and another tube which opens near the tank top. Resultant differential pressure between the tubes is

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 93-015-00 4 of 5 ANALYSIS OF OCCURRENCE: (cont'd}

used to determine level. As a preventative measure, in response to prior BAST level indication problems resulting from boron precipitation and blockage in the level indicator bubbler tubes, a periodic task was previously implemented to blowdown the level indicator bubbler tubes on a weekly basis.

At approximately 0135 hours0.00156 days <br />0.0375 hours <br />2.232143e-4 weeks <br />5.13675e-5 months <br /> on September 13, 1993, the level transmitter bubbler tube of 12 BAST was blown down as part of the recurring task to ensure operability of the BAST level indication.

At the time 11 BAST was cleared and tagged for maintenance. During this evolution level indication is momentarily lost; however, in this instance the tank level indication went high off scale following completion of the blowdown. Due to inoperability of 12 BAST level indication and pre-existing unavailability of the 11 BAST, TS 3.0.3 was entered. Investigation determined the false level indication resulted from blockage of the bubbler tube. The bubbler tube was blown down with control air and at 0210 hours0.00243 days <br />0.0583 hours <br />3.472222e-4 weeks <br />7.9905e-5 months <br /> (same day) operability of 12 BAST level indication was reestablished and TS 3.0.3 was exited.

At 0935 hours0.0108 days <br />0.26 hours <br />0.00155 weeks <br />3.557675e-4 months <br /> on September i6, 1993, the 12 BAST level indication showed greater than 95% following a prior indication of 89.3% at approximately 0800 hours0.00926 days <br />0.222 hours <br />0.00132 weeks <br />3.044e-4 months <br /> (same day) . Investigation determined the false level indication resulted from blockage of the bubbler tube.

At the time 11 BAST was cleared and tagged for maintenance. Due to inoperability of 12 BAST level indication and pre-existing unavailability of the 11 BAST, TS 3.0.3 was entered. The bubbler tube was blown down with control air and at 1015 hours0.0117 days <br />0.282 hours <br />0.00168 weeks <br />3.862075e-4 months <br /> (same day) operability of 12 BAST level indication was reestablished and TS 3.0.3 was exited.

APPARENT CAUSE OF OCCURRENCE:

The root cause of these events is "Design, Manufacturing, Construction/ Installation" (per NUREG 1022, "Licensee Event Report System") of the BAST level indication system. Both events resulted from boron precipitation in the 12 BAST level indicator bubbler tube. Use of a bubbler in a 12% boric acid solution results in the indication system failing high when boron precipitation within the bubbler blocks the flow of nitrogen. A contributing factor to the precipitation is lower than desirable temperature within the bubbler tube. Boron precipitation occurs when the 22,000 ppm boron solution temperature decreases below 145° F.

A possible contributor to the September 13, 1993 event may have been the periodic blowdown of the tank level transmitter bubbler tube.

This activity may have dislodged boric acid crystals at higher elevations in the tube, which then settled in an area of constriction.

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem.Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 93-015-00 5 of 5 APPARENT CAUSE OF OCCURRENCE: (cont'd)

Past corrective actions (addressed most recently by LER 272/93-009-00) have included adjustments to the nitrogen flow rate and increasing the frequency of system blowdown to once every seven days. In addition, the BASTs and respective bubbler tubes of both units have been inspected and cleaned as necessary. These actions have all proven to be only marginally effective. Communications with other utilities, regarding BAST level bubbler failures in a boron solution, indicate boron precipitation will be eliminated by using a 4% boric acid solution.

PREVIOUS OCCURRENCES The following LERs address TS 3.0.3 entries due to BAST level indication events: 272/92-023-00; 272/93-003-00; 272/93-009-00; and 311/93-003-00. The root cause of this most recent event is the same as identified in the referenced LERs.

SAFETY SIGNIFICANCE:

These events did not affect the health and safety of the public. In each case, although 12 BAST level indication had failed required tank level was maintained and the associated Boric Acid Transfer pumps and valves were maintained in normal alignment for use if required. In addition, during each event the Refueling Water Storage Tank (RWST) remained available.

CORRECTIVE ACTION:

Following each event, the 12 BAST level indicator bubbler tube was blown down with Control Air (approximately 100 PSIG) to remove blockage and level indication returned to its previous reading.

The recurring task for blowdown of the bubbler tubes on each unit 1

will be revised to specify use of Control Air.

A design change, which includes reducing the BAST boron concentration to 4% to help minimize boron precipitation in the tank level indicator bubbler tube, is scheduled to be implemented. A similar Unit 2 design change will also be implerne~~ ~

Gen~~~ge~tCi Salem Operations MJPJ:pc SORC Mtg.93-089