05000423/LER-1996-028, :on 960916,potential Overcooling of Charging Pump Lube Oil Sys Occurred Due to Failure of air-operated Temperature Control Valves.Temporary Mod to Limit Failure Position of Three Way Cce Temp Control Valve,Installed

:on 960916,potential Overcooling of Charging Pump Lube Oil Sys Occurred Due to Failure of air-operated Temperature Control Valves.Temporary Mod to Limit Failure Position of Three Way Cce Temp Control Valve,Installed

ML20132G151
Person / Time
Site:	Millstone
Issue date:	12/13/1996
From:	Peschel J NORTHEAST NUCLEAR ENERGY CO.
To:
Shared Package
ML20132G113	List: 05000423/LER-1996-028, :on 960916,potential Overcooling of Charging Pump Lube Oil Sys Occurred Due to Failure of air-operated Temperature Control Valves.Temporary Mod to Limit Failure Position of Three Way Cce Temp Control Valve,Installed
References
LER-96-028, LER-96-28, NUDOCS 9612260189
Download: ML20132G151 (4)

LER-1996-028, on 960916,potential Overcooling of Charging Pump Lube Oil Sys Occurred Due to Failure of air-operated Temperature Control Valves.Temporary Mod to Limit Failure Position of Three Way Cce Temp Control Valve,Installed

Event date:
Report date:
4231996028R00 - NRC Website

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• NRC FORM 366 U.s. NUCLE AR REGULATORY CoMMisSloN APPROVED BY OMB NO.3160 0104 (4 9$)

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digits / Characters for eaCh block) i FACILITY NAME (1)

DOCKET NUMBER (2)

PAGE (3)

Millstone Nuclear Power Station Unit 3 05000423 1 of 4 TITLE 44)

Potential Overcooling of Charging Pump Lube Oil System Due to Failure of Air-Operated Temperature Control Valves EVENT DATE (5)

LER NUMBER (6)

REPORT DATE (7) oTHER rACILITIES INVOLVED (8) q MONTH DAY YEAR YEAR SEQUENTIAL REVISloN MONTH DAY YEAR F ACIUTY NAME DOCKET NUMBER NUMBER 09 16 96 96 028 01 12 13 96 1

OPERATING THIS REPORT IS SUBMITTED PURSUANT To THE REQUIREMENTS OF 10 CFR 5: (Check one or rnore) (11) s MODE m 5

20.2201(b) 20.2203(aH2)(v) 50.73(aH2Hi>

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LICENSEE CONTACT FOR THis LER (12)

NAME TELEPHONE NUMBER IInclude Area Code) i J.M. Peschel, MP3 Nuclear Licensinp Manager (860)437-5840 I

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

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CAUSE

SYSTEM COMPONENT MANUF ACTURER REPORTABLE l

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SUPPLEMENTAL REPORT EXPECTED (14)

EXPECTED MONTH DAY YEAR sUBMISSloN f

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(If yes, complete EXPECTED SUBMisSloN DATE).

j ABSTRACT (Limii to 1400 spaces, i.e., approximately 15 single-spaced typewritten hnes) (16) f f

On August 22,1996, with the plant in Mode 5 at 0-percent power, an engineering evaluation identified a failure scenario in j

which a loss of instrument Air (IAS) to temperature control valves in the Charging Pump Cooling (CCE) system serving the 4

chirging pump lube oil coolers, coincident with 33 degrees i ahrenheit ('F) Service Water (SWP) temperature could potentially result in an overcooling of both trains of the charging pump lube oil system and challenge charging pump j

cperability. On September 16,1996 it was determined that this condition alone could have prevented the fulfillment of the i

safety function of the system. An immediate notification was made at 1144 hours0.0132 days <br />0.318 hours <br />0.00189 weeks <br />4.35292e-4 months <br /> on September 16,1996, pursuant to

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10CFR50.72(b)(2)(iii)(D).

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The cause of charging pump inoperability is inadequate initial design. This condition would result from overcooling of the lube oil system following a failure of the non-QA lAS system coincident with worst case minimum SWP temperature i

End maximum flow and heat exchanger cleanliness. Under these conditions, the air-operated CCE valve (s) would fail open j

and excessive cooling of the tube oil system would occur. This particular combination of conditions was not considered in l

tha initial design. Further evaluation by the pump vendor and by NNECO deterr ned that the charging pumps are operable with 45 degrees Fahrenheit ( F) CCE water which corresponds to a SW temperature of 39 F. Compensatory cction is required to maintain CCE temperature greater than or equal to 45 F when SW temperature decreases below 39 F i

until conective actions are implemented or operability is established at a lower temperature. Corrective actions to resolve i

th3 design issues to qualify the pumps for this scenario are being evaluated and will be implemented prior to plant startup.

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NT.C FORM 366 (4 95) 9612260189 961213 PDR ADOCK 05000423 i

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• U.S. NUCLEAR REGULATORY COMMISSloN (4 95)

UCENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACILITY NAME (1)

DOCKET NUMBER (2)

LER NUMBER (6)

PAGE (3) j YEAR SEQUENTIAL REVISloN i

Millstone Nuclear Power Station Unit 3 05000423 NUMBER NUMBER 2 of 4 i

96 028 01 t

TEXT (11more space is required, use additionalcopies of NRC Form 366A) l17)

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Description of Event

On August 22,1996, with the plant in Mode 5 at 0-percent power, an engineering evaluation identified a failure

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scenario in which a loss of instrument Air (IAS) to temperature control valves in the Charging Pump Cooling (CCE) system serving the charging pump lube oil coolers, coincident with 33 degrees Fahrenheit ( F) Service Water (SWP) l 1:mperature could result in overcooling of both trains of the charging pump lube oil system and challenge charging pump operability. Failure of the air-operated CCE valves to the full open position due to a loss of the non-safety rziated IAS system would adversely affect both trains of the charging pumps by allowing excessive cooling of the l

CCE system which cools the lube oil system. On September 16,1996 it was determined that this condition alone i

could have prevented the fulfillment of the safety function of the system. An immediate notification was made at i

1144 hours0.0132 days <br />0.318 hours <br />0.00189 weeks <br />4.35292e-4 months <br /> on September 16,1996, pursuant to 10CFR50.72(b)(2)(iii)(D) for a condition that alone could have pr: vented the fulfillment of the safety function of the system.

The minimum CCE inlet temperature to the oil cooler was specified as 55 F by the pump manufacturer to assure operability of the pump. Subsequent correspondence with the pump vendor and an Operability Determination (OD)

I performed by NNECO determined that the pumps are operable with 45 F CCE water to the oil cooler; however, a

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engineering evaluation indicates that the CCE inlet to the oil cooler could go below 45 F under worst case conditions.

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Cause of Event

The cause of the charging pump inoperability was inadequate original design. This condition would result from overcooling of the lube oil system from a failure of the non-safety related instrument Air system coincident with a worst case minimum SWP temperature and maximum flow and heat exchanger cleanliness. Under these conditions, tha air-operated CCE valves would fail open and excessive cooling of the lube oil system would occur. This particular combination of conditions was not considered in the initial design.

lil. Analysis of Event A review of the system, subsequently confirmed by engineering evaluation, indicated that the CCE temperature could be reduced to approximately 41 F when SW flow is at its maximum value, SW temperature at 33 F, and heat transfer surfaces clean. The pump vendor has provided assurance that the charging pumps are operable with 45 F CCE water to the inlet of the oil cooler. An Operability Determination performed by NNECO found no adverse effect on the CCE system piping or components due to the 45 F temperature. CCE temperature would remain above 45 F when SW temperature is 39 F or above. Compensatory Ection is therefore required to maintain CCE temperature cbove 45 F when SWP is below 39 Funtil corrective actions are implemented or operability is established at a lower 1:mperature.

IV. Corrective Action

The potential for charging pump lube oil overcooling exists when SW temperature is below 39 F. The short term corrective action is to install a temporary modification to limit the failure position of the three way CCE temperature control valve to ensure sufficient bypass flow around the SW heat exchanger to maintain CCE temperature above 45 F. This temporary modification will be installed before SW temperature reaches 39 F to maintain Charging Pump

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e, NRC FORM 316A U.S. NUCLEAR REGULATORY Commission (4-95) h LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION FACluTY NAME (1)

DOCKET NUMBER (2)

LER NUMBER (6)

PAGE (3)

YEAR SEQUENTIAL REVIStoN Millstone Nuclear Power Station Unit 3 05000423 NUMBER NUMBER 3 of 4 96 028 01 TEXT (If more space is required, use additional copies of NRC Form 366A) (11l Cooling (CCE) system operability until no longer required as the result of either permanent modification c establishment of operability at a lower temperature.

Two options are currently being evaluated for permanent corrective action to preclude overcooling of the charging pump lube oil system. One option is to lower the CCE system design temperature to a new value as determined by i

an ongoing engineering evaluation by the pump vendor. The other option is to perform a physical modification to control the minimum CCE temperature when SW temperature is below 39 F. The permanent corrective action selected will be implemented prior to plant restart.

V.

Additional Information

None

Similar Events

LER 96-013-00 Residual Heat Removal System Desian Deficiency Due to Non-conservative Oriainal Desian Assumption: An engineering evaluation determined that a design deficiency in the Residual Heat Removal System ( RHS ) was a condition that was outside the design basis of the plant. The Safety Grade Cold Shutdown (SGCS) design requirements specify that the unit be capable of being brought to Cold Shutdown with limited operator action outside the control room if RHS heat exchanger operation is initiated at a 350 F RCS temperature as currently assumed in the analysis, and if the RHS throttle control valves 3RHS*HCV606/607 were to fail open as the result of a loss of Control Air, the RHS heat exchanger Reactor Plant Component Cooling Water System (CCP) outlet

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temperature is estimated to be 250 F which is greater then the 125 F used in the system stress i

analysis. The original plant design did not consider that the RHS flow control valves failing open on a loss of air, could create unacceptably high RHS heat exchanger discharge temperatures. This would have created the potential for the CCP piping to not meet the ASME Appendix F stress criteria.

LER 96-006-00 Plant Shutdown Reauired by Technical Soecifications. for Auxiliary Feedwater Containment isolation Valves Declared Inocerable: This LER involved an original plant design discrepancy with a i

containment isolation valve not being capable of remaining closed against maximum accident i

rressure.

LER 96-007-00 Containment Recirculation Sorav and Quench Sorav System Outside Desian Basis due to Desian j

Errors: This LER involved an original plant design deficiency with piping and supports not being adequately designed for loads resulting from accident temperatures.

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• U.S. NUCLEAR REGULATORY COMMISSION l

(4 95) i UCENSEE EVENT REPORT (LER)

TEXT CONTINUATION i

FACILITY NAME (1)

DOCKET NUMBER (2)

LER NUMBER (6)

PAGE (3)

YEAR SEQUENTIAL REVISION l

Millstone Nuclear Power Station Unit 3 05000423 NUMBER NUMBER 4 Of 4 96 028 01 i

TEXT (If more space is required, use additional copies of NRC Form 366A) (17)

Manuf acturer Data Ells System Code:

Chemical & Volume Control System - Charging Pump Cooling System - CB i

Ells Component Code:

V:lve, Control, Temperature - TCV i

Fisher Controls Co., air-operated 3-way temperature control valve Model: 667NS-YS - Size: 2" i

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