ML18096B307

LER 93-003-00:on 930131,level Indicator of 21 Bast Declared Inoperable Due to False High Level Indications.Caused by Design Construction/Installation.Design Change Will Be Developed to Reduce Bast Boron concentration.W/930226 Ltr

ML18096B307
Person / Time
Site:	Salem
Issue date:	02/26/1993
From:	Pollack M, Vondra C Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-93-003-01, LER-93-3-1, NUDOCS 9303040157
Download: ML18096B307 (5)

Text

e OPS~G Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Generating Station February 26, 1993

u. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Dear Sir:

SALEM GENERATING STATION LICENSE NO. DPR-75 DOCKET NO. 50-311 UNIT NO. 2 LICENSEE EVENT REPORT 93-003-00 This Licensee Event Report is being submitted pursuant to the requirements of the Code of Federal Regulations 10CFR 50.73(a) (2) (i) (B). This report is required to be issued within thirty (30) days of event discovery.

Sincerely yours, 1/dt?

/&--- A. Vondra o-Lj-r-'

~ -General Manager -

Salem Operations MJP:pc Distribution 04f"Ol2

. f-The Energy People 9303040157 930226 PDR ADOCK 05000311

,jtJ I I

95-2189 ( 1OM) 12-89 S PDR

i

• NRC FQRM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 3150-0104 (6-89)

I 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 (P-530), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, DC 20555, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) I PAGE (3)

Salem Generating Station - Unit 2 o 15 I o Io I o I 31 111 1 loF 0 I 4 TITLE (4)

Tech. Spec. 3.0.3 Entry; Inoperability of Both Boric Acid Storage Tank's Level Indication EVENT DATE (5) LEA NUMBER (6) REPORT DATE (7) OTHER FACILITIES INVOLVED (8)

f~t~ ~t~t NUMBER SEQUENTIAL REVlSION FACILITY NAMES DOCKET NUMBER(S)

MONTH DAY YEAR YEAR MONTH DAY YEAR NUMBER 0 15 Io I o 1 o I I I 0 11 ~ 1 9: 3 913

- ala I 3 - a I a oj 2 216 913 o,s,o,o,o, I I OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE R~OUIREMENTS OF 10 CFR §: (Chock on* or mar* of th* following) (11) 1---~~~~~

MODE (9)

POWER L~~~L I 0 I 0 I 11--

2

.......~~~

20.402(b) 20.406(*)(1 )(i) 20.405(*)(1)(1i) 20.405(c) 50.38(c)(1) 50.38(c)(2) 50.73(*)(2)(iv) 50.73(*)(2)(v) 50.73(*)(2)(vii) r--

73.71(b) 73.71(c)

OTHER IS~cify in Abstroct

- x r-- below and in Text. NRC Form 20.4061*111 Hill) 50.73(*)(2)(i) 50.73(*)(2)(viii)(A) 366A) 20.406(*)(1)(iv) 50.73(*)(2)(ii) 50.73(*112Hviii)(B) 20.406l*ll1lM 50.7:il*H2Hiii) 50.73(*11211*)

LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER AREA CODE M. J. Pollack - LER Coordinator 6 I 0 I 9 3 I 3 I 9 I- I 2 I 0 12 I 2 COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

MANUFAC- MANUFAC*

CAUSE SYSTEM COMPONENT TURER TUR ER I I I I I I I I I I I I I I I I I I I I I I I I I I I I SUPPLEMENTAL REPORT EXPECTED (14) MONTH DAY YEAR EXPECTED n YES (If YBS. compl*t* EXPECTED SUBMISSION DATE)

ABSTRACT (Limit to 1400 spaces, i.e., approximately fiftaen single-space typewritten lines} (16)

SUBMISSION DATE 1151 I I I On 1/31/93, at 2220 hours0.0257 days <br />0.617 hours <br />0.00367 weeks <br />8.4471e-4 months <br />, the level indicator of 21 BAST was declared inoperable due to false high level indications. 22 BAST was undergoing batching operation at the time. Therefore, Action 3 of Technical Specification Table 3.3-11 was not met, and the action associated with Technical Specification 3.0.3 was entered. Technical Specification 3.0.3 was exited on 1/31/93, at 2242 hours0.0259 days <br />0.623 hours <br />0.00371 weeks <br />8.53081e-4 months <br />, upon restoration of 21 BAST level indication to service. The root cause of this event is "Design, Manufacturing, Construction/Installation" of the BAST level indication system. BAST level indication failures have been a recurring problem at both Salem Units. They have been determined to be due to bubbler tube blockage. The Unit 2 21 BAST bubbler is scheduled for cleaning. The Unit 2 22 BAST bubbler has been cleaned. The corresponding Unit 1 11 and 12 BAST's and the bubbler tubes of each tank have been inspected and cleaned. In addition, the bubbler tube nitrogen flow rates of both Salem Units have been readjusted to 3 scfh, to minimize boric acid precipitation. A design change is being developed which includes reducing BAST boron concentration. This will help minimize boron precipitation in the level indicator bubbler tubes. System Engineering is continuing to monitor BAST level indication failures to determine adequacy of current corrective action.

NRC Form 366 (6-89)

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 2 5000311 93-003-00 2 of 4 PLANT AND SYSTEM IDENTIFICATION:

Westinghouse - Pressurized Water Reactor Energy Industry Identification System (EIIS) codes are identified in the text as {xx}

IDENTIFICATION OF OCCURRENCE:

Technical Specification 3.0.3 entry; Inoperability of Both Boric Acid Storage Tanks' Level Indication Event Dates: 1/31/93 Report Date: 2/26/93 This report was initiated by Incident Report No.93-093.

CONDITIONS PRIOR TO OCCURRENCE:

Mode 2 Reactor Power 1.5% - Unit Load O MWe 22 Boric Acid Storage Tank (BAST) was out of service in support of batching operations DESCRIPTION OF OCCURRENCES:

At 2220 hours0.0257 days <br />0.617 hours <br />0.00367 weeks <br />8.4471e-4 months <br />, on January 31, 1993, the level indicator of 21 BAST

{CB} was declared inop~rable due to false high level indications. 22 BAST was undergoing batching operation at the time. Therefore, Action 3 of Technical Specification Table 3.3-11 was not met, and the action associated with Technical Specification 3.0.3 was entered.

Technical Specification 3.0.3 was exited on January 31, 1993, at 2242 hours0.0259 days <br />0.623 hours <br />0.00371 weeks <br />8.53081e-4 months <br />, upon restoration of 21 BAST level indication to service.

In Modes 1, 2, and 3, Technical Specification 3.3.3.7 requires two (2)

OPERABLE BAST solution level indicators (one/tank). With one level indicator inoperable, Technical Specification Table 3.3-11 Action 3 applies:

"With the number of OPERABLE channels one less than the Required Number of Channels shown in Table 3.3-11, operation may proceed provided that the Boric Acid Tank associated with the remaining OPERABLE channel satisfies all requirements of Specification 3.1.2.8.a."

Technical Specification 3.1.2.6 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:

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 2 5000311 93-003-00 3 of 4 DESCRIPTION OF OCCURRENCE: (cont'd)

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: 11 Technical Specification 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."

APPARENT CAUSE OF OCCURRENCE:

The root cause of this event is "Design, Manufacturing, Construction/

Installation" (per NUREG 1022, "Licensee Event Report System") of the BAST level indication system. BAST level indication failures have been a recurring problem at both Salem Units.

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 used to determine level.

The recurrent failures result from bubbler tube blockage. Several past corrective actions have been unsuccessful. These included increasing the nitrogen purge flow rate from 6 to 8 standard cubic feet per hour (scfh), increasing the frequency of system blowdown from every 92 days to once every seven days, and snaking out and brush cleaning the bubbler tube.

As addressed by LER 272/93-003-00, visual inspection and cleaning of Unit 1 12 BAST revealed boron slug accumulation in the bubbler tube bottom two inches. A pinhole passage through the slug had permitted sufficient nitrogen purge flow through the tube which allowed the indicator to function until complete blockage. Precipitation occurs when 22,000 ppm boron solution temperature decreases below 145° F.

As such, it has been determined that lower nitrogen flow rates (i.e. less than 6 scfh) are desirable in the bubbler tube.

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 2 5000311 93-003-00 4 of 4 ANALYSIS OF OCCURRENCE:

This event did not affect the health and safety to the public. The boron injection system ensures that negative reactivity control is available during each mode of facility operation. Required components include two (2) borated water sources, the two (2) BASTS and the Refueling Water Storage Tank. 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.

During the events reported in this LER, the Refueling Water Storage Tank remained available. Also, although its level indication had failed, required level was maintained in No. 21 BAST. This event is reportable to the NRC per 10CFR 50.73(a) (2) (i) (B) due to entering Technical Specification 3.0.3.

CORRECTIVE ACTION:

The 21 BAST level indicator bubbler tube was blown down to remove blockage. The indicator was then determined "OPERABLE" and returned to service.

The Unit 2 22 BAST bubbler has been cleaned. The Unit 2 21 BAST bubbler is scheduled for cleaning. The corresponding Unit 1 11 and 12 BAST's and the bubbler tubes of each tank have been inspected and cleaned. In addition, the bubbler tube nitrogen flow rates of both Salem Units have been readjusted to 3 scfh, to minimize boric acid precipitation.

A design change is being developed which includes reducing BAST boron concentration. This will help minimize boron precipitation in the level indicator bubbler tubes.

System Engineering is continuing to monitor BAST level indication failures to determine adequacy of current corrective action and to determine additional actions, such as periodic steam cleaning, until implementation of the design change.

_1/d-t/c.L??

~eneral Manager -

~ --Salem Operations MJP:pc SORC Mtg.93-019