ML20205S589

Documents Request for Discretionary Enforcement for Unit 1 TS LCOs 3.1.2.2,3.1.2.4 & 3.5.2 to Support Completion of Repairs & Testing for 1B-B Centrifugal Charging Pump (CCP)

ML20205S589
Person / Time
Site:	Sequoyah
Issue date:	04/17/1999
From:	Salas P TENNESSEE VALLEY AUTHORITY
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NUDOCS 9904260269
Download: ML20205S589 (7)

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l .  : yA Tennessee Vaney Authonty Post Offo Bov 2000 Soddy-Dasy Tennessee 37379 April 17, 1999 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555 Gentlemen:

In the Matter of ) Docket No. 50-327 Tennessee Valley Authority )

SEQUOYAH NUCLEAR PLANT (SON) - UNIT 1 - REQUEST FOR DISCRETIONARY ENFORCEMENT FOR TECHNICAL SPECIFICATION (TS)

LIMITING CONDITIONS FOR OPERATION (LCOs) 3.1.2.2, 3.1.2.4, AND 3.5.2 This letter documents our request for discretionary enforcement for Unit 1 TS LCOs 3.1.2.2, 3.1.2.4, and 3.5.2 to -

support completion of repairs and testing for the 1B-B ' '

centrifugal charging pump (CCP). This relief is needed as a ,

result of the 1B-B CCP failure that occurred on April 15, 1999.

We entered TS LCOs 3.1.2.2, 3.1.2.4, and 3.5.2 at 1619 Eastern daylight time (EDT) on April 15 as a 1 . ult of the inoperable 1B-B CCP and subsequent disassembly of the pump casing. As discussed with the NRC staff on April 16, we request discretionary enforcement for an additional 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> to allow completion of CCP repairs and return to operability testing. With the additional 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br />, TS LCOs 3.1.2.2, 3.1.2.4, and 3.5.2 will expire on April 20 at 1619 EDT if the 1B-B pump has not been repaired, at which time unit shutdown will be accomplished in accordance with the LCO action statement. Detailed justification for the discretionary enforcement is provided in the enclosure.

l This request for discretionary enforcement was verbally I O$b0 requested.and subsequently approved by NRC on April 17, 1999,

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9904260269 990417 PDR ADOCK 05000327 '

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U.S. Nuclear Regulatory Commission Page.2 April 17, 1999 Please direct questions concerning this issue to me at (423) 843-7170 or J. D. Smith at (423) 843-6672.

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as sing and Industry Affairs Manager l I

Enclosure cc (Enclosure):

Mr. R. W. Hernan, Project Manager U.S. Nuclear Regulatory Commission One White Flint, North 11555 Rockville Pike j Rockville, Maryland 20852-2739  ;

NRC Resident Inspector Sequoyah Nuclear Plant 2600 Igou Ferry Road Soddy-Daisy, Tennessee 37379-3624 Regional Administrator U.S. Nuclear Regulatory Commission Region II Atlanta Federal Center  !

61 Forsyth St., SW, Suite 23T85 Atlanta, Georgia 30323-3415 i

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ENCLOSURE TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT (SQN)

UNIT 1 DOCKET NO. 327 UNIT 1 - REQUEST FOR DISCRETIONARY ENFORCEMENT FOR TECHNICAL SPECIFICATION (TS) LIMITING CONDITIONS FOR OPERATION (LCOs) 3.1.2.2, 3.1.2.4 AND 3.5.2 I. BACKGROUND The centrifugal charging pumps (CCPs) are required by TSs to provide reactivity control of the reactor coolant system (RCS) and for emergency core cooling during accident conditions. During normal operation, the CCPs provide charging flow to the RCS to maintain inventory while cleaning and adjusting chemical concentrations. The CCPs also provide seal water to the reactor coolant pumps (RCPs). TS 3.1.2.4 requires that CCPs be available for reactivity control by providing boration flow to the RCS.

TS 3.1.2.2 requires the flowpath through the charging pumps to be operable for flow path boundary integrity.

These flow capabilities depend on the availability and redundancy of the two CCPs. TS 3.5.2 requires that emergency core cooling water be available for accident mitigation. The CCPs provide the high-head injection capabilities with adequate redundancy to ensure cooling water to the core during accidents. The 72-hour action to initiate shutdown for the loss of one CCP is provided ,

based on the low probability of an accident occurring during this time period that requires a CCP. The subsequent shutdown requirements are the result of the loss of CCP redundancy and consideration of single failure consequences.

II. TS OR OTHER LICENSE CONDITION THAT WILL BE VIOLATED On April 15, 1999, a control room operator noticed, while monitoring the control board, that a spray valve had gone closed. This directed his attention to pressurizer pressure and level indication. He observed a decrease in both pressure and level and promptly notified the Unit Senior Reactor Operator. The crew observed that charging flow had dropped from 85 gallons per minute (gpm) to ,

71 gpm; the charging flow control valve was indicating j full open; the RCP seal flows had dropped to 7 gpm; the volume control tank level was increasing; and that the 1B-B CCP motor current had increased from 36 to 43 amps.

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t The shift manager was promptly notified and an assistant unit operator (AUO) was dispatched to the pump.

, The AUO promptly reported that the pump had excessive seal {

l leakage. At this time, within 15 minutes of the time that j 1B-B CCP began to degrade, the 1A-A CCP was started prior to receipt of any main control room alarms. This resulted in a charging flow increase to 110 gpm; RCP seal flows increased to 11 gpm each; and 1A-A CCP current remained stable at 36 amps. The 1B-B CCP was stopped at this time.

l The operators adjusted the seal flow to 8 gpm per RCP and i decreased the charging flow to 95 gpm. Pressurizer level increased to normal level.

The operators subsequently declared the 1B-B CCP inoperable and entered the 72-hour allowed outage time (AOT) for TS LCOs 3.1.2.2, 3.1.2.4, and 3.5.2 as of 1619 EDT.

I III. CIRCUMSTANCES SURROUNDING THE SITUATION l Our inspection of the 1B-B CCP revealed that there was no visible damage.to the pump casing or shaft. However, the locknut that secures the balance drum in place was loose. q Also, increased pump vibration and balance drum flow were '

observed prior to taking the pump out of service. These observations are indicative of symptoms previously observed by SON and the industry associated with shaft .

failures. Our investigation of the 1B-B CCP failure is I continuing.

IV. SAFETY SIGNIFICANCE The loss of one CCP reduces the redundancy provided in the SON design basis for reactivity control boration flow and emergency core cooling high-head flow. We previously requested Westinghouse Electric Company to perform an .

I evaluation based on a probabilistic risk analysis (PRA) on the acceptability of increasing the LCO action requirements for loss of one CCP from 3 days (72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />) to 7 days. This evaluation was included as Enclosure 4 to TVA's letter to NRC dated August 28, 1991, "Sequoyah Nuclear Plant (SQN) - Technical Specification (TS) Change j 91-03." This evaluation supported our TS change request l to permanently change the action requirements for TSs l 3.1.2.4 and 3.5.2 from 3 days to 7 days for one CCP being inoperable. NRC denied the TS change request in a letter to TVA dated April 20, 1993, " Denial of Amendment Request (TAC Nos. M81382 and M81383) (TS 91-03) . " This was based on the request being inconsistent with standard TSs, historical evidence that pump shaft failures are rare and l usually unexpected, and no basis for the change, such as a L proven need or safety benefit other than the PRA. NRC E2 L

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[ went on to say that such cases of CCP shaft failures could be handled better by a request for discretionary

, . enforcement to increase the AOT.

Subsequent to the Westinghouse analysis discussed above,

.we revised our individual plant examination (IPE) analysis (reference TVA letter to NRC dated February 20, 1998). A

, calculation has been performed using the zero-maintenance l model developed from Revision 1 of the IPE. This l calculation shows that with one train of CCP out of I

service the change in core damage frequency (CDF) is 9.541E-8/ day. The Incremental Conditional Core Damage t

Probability (ICCDP) for a 5-day AOT is 4.77E-7. This l value is considered small for a single TS AOT change as

! discussed in Section 2.4 of Regulatory Guide (RG) 1.177 (the CDF from Revision 1 of the IPE is 3.77E-5/ year) .

l Table 1-14 of the SQN IPE, Revision 1 Report lists the 1 major contributors to Large Early Release Frequency I (LERF). The event in the table, which is potentially l effected by the increase in unavailability of one train of charging, is the High-Pressure Melt Ejection / Hydrogen Burns at Vessel Breach. High-Pressure Melt Ejection is I usually associated with an Anticipated Transient Without l Scram (ATWS) event, so the ability to mitigate this event i by boron injection via the charging pumps potentially I would effect the contribution of this event to LERF.

Table 3.4-2 of the SQN IPE, Revision 1 Report shows that l ATWS events are not binned to this event. Therefore, the increase in LERF due to a five-day uvavailability of one train of charging is proportional to the increase in CDF.

The LERF, as discussed in Revision 1 of the SQN IPE, is l predicted to be 1.6 percent of CDF. Therefore, the

! expected Incremental Conditional Large Early Release L Probability is 1.6 percent of the ICCDP or 7.63E-9. This l increase in LERF is considered small for a single TS AOT l change as discussed in Section 2.4 of RG 1.177. ,

V. SIGNIFICANT HAZARDS AND PUBLIC HEALTH / SAFETY CONSIDERATIONS f

r The requested extension of time was determined to have no l- safety significance because core damage frequency will i increase a negligible amount as shown by the evaluation

( above. Additionally, the operability of the operating CCP will be monitored closely as a means of detecting any potential problems that could impact safety functions.

Therefore, the requested discretionary enforcement will not result in a significant increase in the consequences of an accident. The probability of an accident or i possibility of a new accident is not affected because the CCPs and their associated TS requirements provide for E3

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l normal operation and accident mitigation functions, but i are not considered to be the source of an accident. A

. .significant reduction in the margin of safety will not

occur because plant parameters will continue to be maintained consistent with the safety analysis assumptions and the risk analysis, which shows an insignificant increase in risk. Therefore, the requested discretionary enforcement will not adversely impact nuclear safety and will prevent an unnecessary unit shutdown.

VI. ENVIRONMENTAL CONSIDERATIONS This action does not involve an unreviewed environmental question because it does not increase any adverse environmental impacts, change effluents or power level, or result in unreviewed environmental matters.

VII. COMPENSATORY MEASURES Unit 1 is presently operating at 100 percent reactor thermal power with no other reactivity control systems or emergency core cooling systems inoperable. The 1A-A CCP is in service providing RCS charging and seal flow, and is available to provide accident mitigation functions. While the 1B-B CCP is being repaired and returned to service, we are monitoring the 1A-A CCP vibration levels as a means to provide an early warning of potential pump problems. The lA-A CCP vibration levels at this time are acceptable and match'the last vibration readings for this pump.

Operations personnel are monitoring the 1A-A CCP locally at least twice each shift for any abnormal indications (e.g., leakage, noise). In addition, work activities that could adversely impact operation of the 1A-A CCP have been suspended until the 1B-B CCP is returned to operable status. If the capability of the 1A-A CCP is determined I to be adversely affected, we will enter the actions for TS 3.0.3 and place the unit in a safe condition. We will also limit access to the 1A-A CCP and its associated shutdown board, as well as protecting the boration flow path associated with the lA-A CCP. We have also assessed the impact on risk for other maintenance activities and have adjusted the schedule outside the increased AOT timeframe for any significant or sensitive activities.

VIII. JUSTIFICATION FOR DURATION OF THE NONCOMPLIANCE We request discretionary enforcement to extend the action l time for TS LCOs 3.1.2.2, 3.1.2.4, and 3.5.2.a by l

~48 hours. This extension will allow up to 120 hours0.00139 days <br />0.0333 hours <br />1.984127e-4 weeks <br />4.566e-5 months <br /> j (1619 EDT on April 20) to complete repairs and return the IB-B CCP to service. Present estimates show pump shaft l replacement, system alignment, and testing for operability I i to be complete on April 19. This extension contains E4

additional time in consideration of potential difficulties encountered during the remaining reinstallation activities

. .that could delay the present scheduled final alignment activities. Without the requested extension, Unit 1 would be required to shutdown at 1619 EDT on April 18.

IX. PORC REVIEW This. request has been reviewed and approved by PORC.

X. NOTICE OF ENFORCEMENT DISCRETION (NOED) CRITERIA

! This request satisfies NOED criteria given in Section B, Paragraph 2.0, Item 1. (a) in Attachment 1 of AL-95-05, Revision 1. This criteria is satisfied in that Unit 1 is

. online at 100 percent power and the potential additional

( risk of transients while bringing.this unit down is l considered undesirable given the minimal increase in risk associated with the AOT extension.

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