ML19354D906

LER 89-033-00:on 891216,refueling Water Storage Tank Level Transmitters Failed High Due to Freezing from Extremely Cold Weather & Inappropriate Use of Calculations.Engineering Procedures Revised & Heating Installed in encl.W/900116 Ltr

ML19354D906
Person / Time
Site:	Sequoyah
Issue date:	01/16/1990
From:	Bynum J, Spencer S TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-033, NUDOCS 9001240078
Download: ML19354D906 (9)

Text

. .

S TENNESSEE VALLEY AUTHORITY 6N 38A Lookout Place January 16, 1990 U.S. Nuclear Regulatory Commission ATTN Document Control Desk Washington, D.C. 20555 Gentlemen:

TENNESSEE VALLEY AUTHORITY - SEQUOYAH NUCLEAR PLANT UNIT 1 - DOCKET NO.

50-327 - FACILITY OPERATING LICENSE DPR LICENSEE EVENT REPORT (LER) 50-327/89033 The enclosed LER provides details concerning an entry into Limiting Condition for Operation 3.0.3 when the refueling water storage tank level channels failed and were declared inoperable because of freezing from the cold weather. This event is reported in accordance with 10 CFR 50.73, paragraph a.2.1.b.

Very truly yours.

TENNESSEE VALLEY AUTHORITY

. R. Byn esident Nuclear Power Production Enclosure cc (Enclosure):

Regional Administration U.S. Nuclear Regulatory Commission Office of Inspection and Enforcement Region II 101 Marietta Street, Suite 2900 Atlanta, Georgia 30323 INPO Records Center Institute of Nuclear Power Operations 1100 circle 75 Parkway, Suite 1500 Atlanta, Georgia 30339 NRC Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379 9001240078 900116 d PDR ADOCK 05000327 g PDC i ,

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"' Limiting Condition for Operation 3.0.3 entered when the refueling water storage tank level transmitters failed because of freezing during cold weather EVENT DATE (Si LER NUMSER (Si REPORT DAff 17) OTHE R S ACILITit$ INVOLVED (Si MONTH DAY YEAR vtAR OM L QL*y MONTH Day vEAR eacetifvhaMes DOCKET NUMBERI5 Sequoyah, Unit 2 01510 l 0 l 0 l3 l 2 l 8

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Sydney W. Spencer, Compliance Licensing Engineer 6 1115 8l4l3l-t 7 l 51 4l C COMPLEf t ONE LINE poR E ACM COMPONENT F AtLURE DESCRitED IN THIS REPORT 113)

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• e , soprose ensey fifteen senere spece typewrerfen tsaesi titi At 0357 Eastern standard time (EST) on December 16, 1989, with Unit 1 in Mode 1, the refueling water storage tank (RWST) Level Transmitters 1-LT-63-50 and 51 had failed high. At 0828 EST with Unit 2 in Mode 1, RWST Level Transmitters-2-LT-63-50, 52 had failed high. As a result, both Units entered Limiting Condition for Operation (LCO) 3.0.3 at 0357 and 0828 respectively. The failures were because of freezing from extreme cold weather. Additional transmitter failures occurred in the east main steam valve vault and outside the auxiliary building. The root cause of the freezing of the RWST sense lines was prior removal of power to heaters and thermostats installed in the transmitter enclosures due to an inappropriate use of calculations. The root cause of the freezing sense lines in the main steam valve vault was inadequate concideration of freeze protection requirements during design changes to increase ventilation flow. The root cause of transmitter sense lines freezing on the outside of the auxiliary building was insulation not in accordance with design requirements. Immediate corrective actions ,

consisted of obtaining discretionary enforcement to extend operation in LCO 3.0.3, issuing night orders to ensure adequate RWST water levels existed, providing guidance to l 4

operators for performing RWST to containment sump swapover with the level transmitters inoperable / unreliable, erecting enclosures, installing heating within enclosures, reenergizing heat tracing, and recalibrating the RWST level transmitters. Longer-term corrective action consists of (1) revision of NE's drawings and installation of qualified IE thermostats, (2) rerouting or insulation of sense lines in the valve vaults, (3) revision of engineering procedures to require documented concurrence of cross discipline review and (4) disciplining appropriate personnel.

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0 l8 TexTin A, = . ann.,wmc r annun DESCRIPTION.OF EVENT At 0357 Eastern standard time (EST) on December.16, 1989, with Unit 1 in Mode 1 (100 percent power, 578 degrees Fahrenheit (F] and 2,235 pounds per square-inch gauge

[psig]) refueling water storage tank (RWST) (EIIS Code BQ) Level Transmitters 1-LT-63-50 and 51 failed high. By 0828 EST with Unit 2 in Mode 1 (80 percent power.L571 degrees F. '

end 2,235 p-ig) RWST level Transmitters 2-LT-63-50 and 52 had also failed high. As a result of the extremely cold temperatures (Chattanooga and surrounding areas were experiencing approximately 8 degrees F-with wind chill temperatures'approximately minus ,

20 degrees F). multiple transmitter failures were occurring because of freezing of.

l- associated sense lines. As a result, Units 1 and.2 entered Limiting Condition for l Operation (LCO) 3.0.'3.at 0357 and 0828 respectively.. e In addition.to the RWST level transmitters, Flow Transmitters 2-FT-3-90A"and Pressure Transmitter 1-PT-1-9A failed high due to freezing. Transmitter.2-FT-3-90A sense line is routed on the exterior wall of the auxiliary building and provides.feedwater flow input to determine steam flow greater than feed flow coincident with' low S/0 level to initiate a reactor trip. Pressure Transmitter 1-PT-1-9A -located in the main steam valve vault, monitors low steam pressure coincident with high steam flow to initiate steam line

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isolation and safety injection.

Listed below is a chronology of instrument failures, and LCO entries / exits,that' occurred- j' because of freezing conditions.

Unit 1

1. At'0357,'l-LT-63-50 and 51 failed high. LCOs 3.3.2.1,'3.3.3.7 and 3.0.3 were entered.

2. At 0406, 1-LT-63-52 failed high.

3. At 0555, 1-PT-1-9A and 1-FT-1-10A failed high. LCOs 3.3.2.1 and 3.3.3.7 were entered.

l 4. At 0649, 1-LT-63-53 failed high.

l S. On December 17, 1989, at 1845, the action statements of LCOs 3.0.3, 3.3.3.7, and 3.3.2.1 were exited.

Unit-2 -

1. At 0127, 2-FT-3-90A failed high. ,

-2. At 0521, 2-LT-63-52 failed high. LCO 3.3.2 was entered.

3. At 0828, 2-LT-63-50 failed high. LCO 3.0.3 was entered.

4. At 0935, 2-LT-63-51 failed high.

5. On December 17, 1989, at 1056, the action statements of LCOs 3.3.2, and 3.0.3 were l exited.

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• DESCRIPTION OF EVENT (Continued]

, Site Licensing personnel were notified at approximately 0400 on December 16. 1989,,of the status of'the plant concerning the RWST level-transmitters, that the condition had '

placed Unit 1 in LCO 3.0.3, and the possibility existed that both units at SQN could be placed in LC0 3.0.3. The senior NRC resident inspector was notified at 0404.regarding this, problem, and the need to request NRC discretionary enforcement to. allow time to.

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thaw and return the transmitters operable was discussed.. Licensing personnel requested plant personnel to.obtain pertinent data on this situation in preparation for a telephone conference call with NRC. 'NRC's verbal approval of the 48-hour discretionary .

enforcement for Unit I was provided to TVA by NRC at 0615 EST on December 16', 1989. ,

Unit 2 was subsequently discussed with NRC, and the verbal 48-hour discretionary -

anforcement period to coincide with Unit 1 was granted at 1155 EST on fecember 16, 1989. The letter from TVA requesting discretionary. enforcement was submitted to NRC on December 17, 1989. NRC's formal acknowledgement of the' discretionary enforcement was received on December 18, 1989.

Interim actions established were to initiate night orders that included actions to monitor the RWST volumes by reading the narrow-range level transmitters, to remove the-manway on top of the tank once each shift to visually verify level, and to provide continuous fire watches at RWST level transmitters (this. fire watch ensured no fire dranage resulted from temporary enclosures built around the RWST level transmit'.er as the tamporary enclosures contained portable heating equipment), and to provide guidance to operators for performing RWST to containment sump swarover with the level transmitters inoperable / unreliable under. Emergency Procedure ES-1.2, " Transfer to RHR Containment Sump." Both of the referenced night orders were required'to be reviewed at each shift turnover meeting until the RWST level transmitters were returned operable.

Inunediate actions were taken by TVA to thaw the f rozen instrument sense lines and .

l prevent additional freezing from occurring. A temporary alteration control-form-(TACF) was initiated to reenergize power to the enclosure heaters and thermostats for the RWST level transmitters. A TACF 0-89-70-400 was issued-to install plastic. sheeting over the k blow-out panels in the east and west main steam valve vaults to preclude the loss of internal heating. Periodic temperature monitoring was' initiated for the main steam valve vaults. Work Request B793481 was issued to repair..the insulation, install a plastic sheeting tent and heater around Transmitter 2-FT-3-90A, and to blowdown the transmitter. When these actions began to be effective and the sense lines were thawed, the transmitters.were recalibrated and returned to service.

On December 17, l'989, the RWST level transmitter senso lines were thawed, the instruments were recalibrated, and LCO 3.0.3 was exited at 1845 and 1056 for Units 1 '

and.2 respectively.

The events leading to this event are as follows:

.A2 a result of several occurrences of RWST level transmitter and sense line freezing, Design Change Request 1399 was initiated in December 1981 requesting that adequate ,

freeze protection be provided.

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In July 1982, Engineering Change Notice'(ECN) 5653 (Work Plan 10095) was_ approved to  !

install strip heaters and control thermostats inside the RWST level transmitter anclosures (1,.2-LT-63-50, 51, 52,.and 53). In addition, heat tracing and insulation was upgraded for the sense lines and enclosures.

On March 17, 1988, Condition Adverse to Quality Report (CAQR) SQP 880260 was written to

-document two problems associated with ECN 5653.' Problem it Based on Quality

• Information Release NEB 87276, which reported th'e results of the analysis that was documented in calculation SQN-APS2-039, the temperature inside the level transmitter cnclosure could reach as high as 315 degrees F should the thermostats / heaters fail to da-energize. This exceeded the 140 degrees F maximum ambient temperature rating of the 1svel transmitters. Problem 2 No documentation had been found'to indicate that this equipment was qualified for applications involving Class 1E equipment. These problems ware also documented as Design Baseline Verification Program Punchlist Items 8885 .i and 9684. l 1

To resolve the CAQR, Design Change Notices (DCNs) M01138A and M01139A were issued on I Ssptember 21, 1989, to remove electrical power to the thermostats and heaters installed i under ECN 5653. The DCNs also qualified the thermostats and heaters to position  !

retention requirements because they were not removed as part of the DCNs. Because the hsaters and thermostats were no longer a heat source and seismic qualification was demonstrated, both of the problems stated above were resolved. Calculation SQN-APS2-039 l was referenced in these DCNs to provide' assurance that the level transmitters would '

function at low temperatures.

During the independent qualified reviewer (IQR) review of the workplan for DCNs M01138A and M01139A, questions were again raised concerning the potential.for freezing of the sense lines. NE resolved this comment with the IQR, and the DON was implemented; however, NE agreed to later perform calculation SQN-SQS2-0101, which confirmed that sense line freezing would occur. Calculation SQN-SQS2-0101 was completed on November 13, 1989, and an action item was placed on the Plan of the Day (POD) meeting agenda to procure and install qualified 1E thermostats._ The purchase request was to be initiated by December 15, 1989, with installation anticipated for mid-January. These e proposed dates were considered acceptable by personnel who anticipated that extreme weather would not occur until the ' late January or early February time frame. Therefore,

. low temperature protection was not provided, and, as a result, the level transmitters began to fail at 0357 on December 16, 1989, l i

CAUSE OF EVENT RWST' (

The root cause of this event is attributed to NE misapplying the results of calculation SQN-APS2-039. The conditions _and assumptions in this calculation were to determine the maximum internal enclosure temperature (based on varying outside temperatures), rather than the minimum. However, the information was incorrectly interpreted by personnel utilizing the calculation.

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In addition, personnel preparing DCNs 1138 and 1139 incorrectly assumed that the review performed by the personnel of the discipline that prepared the calculation for. the safety evaluation for these DCNs served as the inter-disciplinary technical interface review required in accordance with Nuclear Engineering Procedure (NEP)'5.2.

Although the problem of possible freezing of the-sense lines and transmitters was' identified _in the POD meeting on October 26, 1989, as an action item, it was not given proper management attention to prevent this occurrence. Site personnel involved with this issue failed to initiate a CAQR when it was confirmed that-an inadequate design change had been implemented because a calculation was misapplied.

1 Main Steam Valve Vaults The root cause of Pressure Transmitter 1-PT-1-9A freezing was inadequate consideration i of additional freeze protection requirements during design changes to increase l vsntilation flow. As a result of these design changes, freezing was considered and cddressed in procedure GOI-6H, but it was not anticipated that there would be freezing-problems in the main steam valve vaults during power operational _ modes.

Auxiliary Building (Exterior) l' The root cause of Flow Transmitter 2-FT-3-90A freezing is attributed to-insulation not k

~bsing in accordance with design drawings, i.e., wrong type of insulation. I ANALYSIS OF EVENT  !

L This event is being reported in accordance with 10 CFR 50.73, paragraph a.2.i.b. as an operation prohibited by the plant technical specifications.

RWST The primary function of the RWST is to provide a source of borated water to the cmergency core cooling system during a loss of_ reactor coolant condition. The purpose j of the-level transmitters is to provide RWST level indication and automatic transfer of stfety injection suction from RWST to the containment sump upon low RWST level-(with- j concurrent minimum sump level) after safety injection signal actuation. If these transmitter failures had occurred concurrent with a loss of coolant accident, the result could have been a failure of automatic transfer of safety injection auction from RWST to the containment sump and could result in a loss of flow and possible damage to pumps. .

Indication of the failure of these transmitters was inanediately noticed by the unit '

operators, and operators took appropriate actions.

Main Steam Valve Vault and Auxiliary Building (Exterior) '

The instrument failures, which occurred in the east main steam valve vault and the exterior of the auxiliary building, are part of the steam / feed flow regulating logic.

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-ANALYSIS OF EVENT (Continued),  ;

Failure of the main ~ steam pressure transmitter (1-PT-1-9A) in the high direction is away Co n the safety limits (low pressure) that would prevent sensing a requirement for a.  ;

d ly action. The' low pressure.is one of the two possible signals coincident with high steam flow delta P that initiates a steam line isolation and safety injection.

1-PT-1-9A provides an input signal to the 1-FT-1-10A flow transmitter. Operations tripped the appropriate bistables ensuring the operable Transmitter 1-PT-1-9B would datect and perform the required safety action. '

Failure of the main feed Flow Transmitter (2-FT-3-90A) high direction also moved the  !

indication away from safety limits. Feed flow is-used along with steam flow to  ;

determine mismatch (steam flow greater than. feed flow) coincident with low-steam gsnerator (S/G) level to initiate a reactor-trip. Operations tripped the appropriate bistables thus ensuring safety.- The transmitter was being used for Loop 3 S/G control. ,

Failure of the transmitter in the high direction caused the control system to reduce flow to Loop 3. Operator intervention save.d a S/G low-level reactor trip and recovered the S/G 1evel. Operations then placed control in a reliable. flow loop.

l CORRECTIVE ACTION l'

Immediate Corrective Action ,

Immediate corrective actions taken for the RWST consisted of obtaining discretionary  ;

enforcement to extend operating in LCO 3.0.3, erecting enclosures, installing heating within enclosures, issuing night orders containing provisions to ensure adequate RWST' water levels exist and to provide revised operational requirements for Emergency Procedure ES-1.2, and recalibrating the transmitters. TACF 0-89-69-063 was initiated to

l. rainstall power to the enclosure heaters and thermostats for the-level transmitters.

Operations Section Letters Administrative 99 was revised to require operator varification to detect potential failures every four hours.

• Immediate corrective actions taken for the main steam valve. vault consisted of issuing.

TACF 0-89-7L-400 to install plastic sheeting over the blow-out panels in the east and

' wast main steam valve vaults to prevent the loss of internal heating. Periodic-monitoring was initiated for. temperature verif f :ation' in the main steam valve . vaults (once each shift).

Immediate corrective actions taken for the auxiliary building (exterior) consisted of issuing Work Request B793481 to repair the insulation, install a plastic sheeting tent and heater around the transmitter, and to blowdown and recalibrate the transmitter.

Long-Term Corrective Action 1.- Immediate action was taken by the Work Control Group to revise the POD agenda to readily identify and prioritize items that may have an immediate or significant .!

affect on plant operability.

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0l0 0l7 0F 0 l8 text nr . e .as wmac r asnawim j CORRECTIVE ACTION (Continued) 2.- Field-DCNs 1858A and 1859A have been issued to add qualified 1E thermostats and to reconnect the heaters. The field implementation will be completed by January 31, 1990.

3. The insulation on the seven sense lines identical'to 2-FT-3-90A will be verf.fied.to be in accordance with the design drawings by January 26,~1990.

4. An investigation will be performed to determine how the improper insulation was installed on 2-FT-3-90A by March 15, 1990. ,

5. NE will revise the appropriate procedures by February 28, 1990, to require that-NE personnel utilizing existing design input (i.e., calculations) from another discipline to support the issuance of design output = documents shall obtain an inter-disciplinary technical interface review in accordance with NEP 5.2 and-'shall require their concurrence on the involved DCN cover sheet prior to issuing the 4 output.

6. To address the issue that a CAQR was not initiated when calculation SQN-SQS2-0101

( identified that the RWST sense. lines would freeze, each discipline lead engineer shall instruct their employees on the importance of identifying conditions adverse to quality when deficiencies are first noted so that proper and: timely corrective action can be taken. Appropriate disciplinary. action will be taken'for the individuals concerned with this event. .These actions will be completed by:

February 16, 1990.

7. Sense lines located close to the openings in the valve vaults shall.be evaluated for rerouting or installation of permanent insulation.- The-evaluation-results will be implemented by November 1 1990.

ADDITIONAL INFORMATION 1

There have been nine previous LERs reported as a result of freezing instrument lines (SQN 50-327/80-202,80-206, 81-003,81-004, 81-154,85-006, 50-328/82-101,82-013, and 83-006. Previous corrective actions were not effective because of the reasons identified in this report. There had been no LERs written after the heat-trace was added to the RWST instrument lines.

COMMITMENTS '

1. Field-DCNs 1858A and 1859A have been issued to add qualified 1E thermostats and reconnect the heaters. The field implementation will be completed by January 31,

• 1990.

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' COMMITMENTS (Continued)

2. NE will revise the appropriate procedures by February 28, 1990, to require that NE personnel utilizing existing design input (i.e., calculations) from another discipline to support the issuance of design output documents shall obtain an inter-disciplinary technical interf ace review in accordance with NEP 5.2 and shall require their concurrence on the involved DCN cover sheet prior to issuing the output.

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3. To address the issue-that a CAQR was not initiated when calculation SQN-SQS2-0101 identified that the RWST sense lines would freeze, each discipline lead engineer shall instruct.their employees on the importance of identifying conditions adverse to quality when deficiencies are first noted so .that proper and timely corrective, action can be taken. Appropriate disciplinary action will be taken foi the individuals concerned with this event. These actions will'be completed by February 16, 1990. ~

1 4 Sense lines located close to the openings in the-valve vaults shall be evaluated for rerouting or installation of permanent insulation. The evaluation results-will be implemented by November 1, 1990.

5. The insulation on the seven sense lines identical to 2-FT-3-90A will be verified to be in accordance with the design drawings by January 26.-1990.

6. An investigation will be performed to determine how the improper insulation was installed on 2-FT-3-90A by March 15, 1990.  ;

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