05000369/LER-2010-002

LER-2010-002,

Docket Number
Event date:	05-12-2010
Report date:	06-30-2010
3692010002R00 - NRC Website

BACKGROUND

The following information is provided to assist readers in understanding the event described in this LER. Applicable Energy Industry' Identification [EIIS] system and component codes are enclosed within brackets. McGuire unique system and component identifiers are contained within parentheses.

The Containment Spray System (NS) [BE] provides containment atmosphere cooling to limit post accident pressure and temperature in containment to less than the design values. Reduction of containment pressure and the iodine removal capability of the spray reduce the release of fission product radioactivity from containment to the environment, in the event of a Design Basis Accident (DBA).

Technical Specification (TS) 3.6.6 "Containment Spray. System" specifies that two NS [BE] trains shall be operable in MODES 1, 2, 3, and 4. TS 3.6.6 Condition A allows one NS [BE] train to be inoperable for up to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.

TS 3.6.6 Condition B applies when an inoperable train exceeds the 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> completion time (72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />) before required actions to restore the train to operable are complete. Condition B requires that the unit to be placed in MODE 3 in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and MODE 5 in 84 hours9.722222e-4 days <br />0.0233 hours <br />1.388889e-4 weeks <br />3.1962e-5 months <br />.

The pump motor oil sight glass.provides a visual means to monitor oil levels and in the case of the NS [BE] pump motor bearing, the sight glass provides a means of maintaining the oil level. The acceptable oil level isi,marked on the sight glass which is routinely monitored by station operators. For Systems, Structure, and Components (SSC) accessible during all plant conditions, oil addition is assured and provides reasonable assurance of operability. Conversely, oil addition to SSCs that cannot be accessed under all plant conditions may not provide a reasonable assurance of operability.

In these cases, the oil leak rate must not deplete the oil volume necessary to sustain SSC operability for the duration of the SSC mission time. The mission time is the duration of SSC operation that is credited in the design basis for the SSC to perform its specified safety function. The specified mission time for NS [BE] system is 30 days.

Repeated oil addition can indicate degradation requiring immediate repair and is entered into the site's corrective action program to evaluate the degraded condition and determine if additional action or maintenance is required.

The oil leaking from the NS [BE] pump motor was entered into the site's corrective action program on April 29, 2010. The 1A NS [BE] pump motor is not accessible for all postulated plant conditions and an engineering evaluation was required to determine how the past several oil additions affected the past operability of 1A NS [BE] pump motor.

Based upon measurements of the sight glass, amount of oil added, time period the oil was added, operating, environmental and radiological conditions, an engineering evaluation determined the leak rate would have resulted in exceeding the oil volume necessary to maintain 1A NS [BE] pump motor operability for the duration of the mission time. Reasonable assurance of past operability (i.e., ability to meet the 30 day specified mission time) could not be justified for a period of 14 days (April 15 - April 29, 2010).

At the time of the event, Unit 1 was operating in MODE .1 at 100% power.

During the 14 day period where operability was impacted, Unit 1 was in Modes 1-4 followinga refueling outage.

The unit's Technical Specification (TS) 3.6.6 allows for an inoperable NS was operated in a condition prohibited by TS and reportable under 10 CFR 50.73 (a)(2)(i)(B). Additionally, a surveillance .test pe'rformed during the fourteen day period rendered Unit 1 "B" Train NS [BE] pump inoperable resulting in two trains being simultaneous inoperable and is reported as an event or condition that could have prevented the fulfillment of a safety

• function per 10 CFR 50.73 (a) (2) (v) (C).

EVENT DESCRIPTION

On April 29, 2010 at approximately 11:00 hours an oil leak of 24 drips per hour coming from the sight glass for the lower bearing oil reservoir on the "A" Train Containment Spray (NS) pump was declared inoperable, Technical Specification 3.6.6 was entered, and the condition was entered into the Technical Specification Action Item Log and documented in the site's corrective action program. The oil leak was subsequently corrected and the site exited TS 3.6.6 on April 29, 2010 at 16:16 hours.

An engineering evaluation, completed and approved on May 12, 2010, concluded that reasonable assurance of past operability (i.e., the oil leak rate could have exceeded the oil volume necessary to sustain pump operation for the 30 day mission time) could not be justified for a period of fourteen days (April 15 - April 29, 2010).

The duration that 1A NS Train was past inoperable would have exceeded the allowable completion time specified in the Unit's TS for approximately 11 days. Unit 1 was in a TS Mode of Applicability during this time period; therefore, Unit 1 had operated in a condition prohibited by the site's Technical Specifications and met the reporting criteria specified in 10 CFR 50.73 (a) (2) (i) (B). Additionally, the Unit 1 "B" Train NS was declared inoperable during this period (4/22/2010 @ 2014 hours0.0233 days <br />0.559 hours <br />0.00333 weeks <br />7.66327e-4 months <br /> until 4/22/2010 @ 2123 hours0.0246 days <br />0.59 hours <br />0.00351 weeks <br />8.078015e-4 months <br />) to perform surveillance. Therefore, this condition resulted in two NS Trains being simultaneously inoperable which, in addition to reporting as an operation prohibited by the unit's TS under 10 CFR 50.73 (a)(2)(i)(B)is reported as a condition that could have prevented fulfillment of a safety function per 50.73(a)(2)(v)(C).

The "discovery time" for the purpose of reporting this event is considered the time at which the engineering evaluation necessary to determine the impact to past operability was completed and approved (May 12, 2010).

CAUSAL FACTORS

The primary reason the oil level degraded to the point where the 1A NS pump motor's ability to meet the specified mission time was compromised was failure to recognize or determine the existing condition correctly. The low oil level was observed and assessed by several different people and disciplines. Therefore, individual assessments and conclusions were based on single data points rather than collective information. A root cause evaluation of the event indicated a process weakness regarding how each incidence of low oil level is tracked and trended and included several factors leading up to the organizations' failure to detect and correct the degraded condition before the mission time of a safety related component was adversely affected. Specifically:

• Maintenance procedures for oil sampling and oil additions are generic in nature and did not address the uniqueness of the sight glass design and the potential effect on the sight glass assembly configuration during maintenance activities.

• Insufficient program guidance and expectations to address mission time requirements (i.e. assurance of future operability under design basis event). Although, licensed operators have received training on Mission Time and its importance relative to operability, NUclear Equipment Operators were not included in the training population. Consequently, NEO response to low oil level indication was to replenish oil to ensure current operability and did not include any action to address the mission time of the SSC. or its future operability due to continuous oil additions.

• There was a lack of information for trending- equipment performance issues related to the frequency of oil addition to restore oil levels.

The requitement to submit oil addition data is required in the maintenance procedure for oil addition but the step did not specify hbw soon this needed to be accomplished. As a result, the information from completed procedures was sent in batches after all oil additions scheduled for the week were completed. Als6, the. enclosures did not provide the WR or WO number and dates for oil addition which could 1-ive facilitated trending.

CORRECTIVE ACTIONS

Immediate:

1. The 1A NS pump motor oil sight glass was repaired and pump motors using the same sight glass design were chetked to ensure correct oil levels and no leaks from sight glasses.

Subsequent:

1. Procedures controlling oil additions were placed on Technical Hold.

(Technical Hold ensures any additional guidance or restrictions are reviewed prior to executing the procedure).

Planned:

1. Revise applicable procedures to provide additional information on potential vulnerabilities when making oil additions via sight glasses based on sight glass design and sealing characteristics. Directions for proper tightening of applicable components on all sight glass designs will be included.

2.Revise Operations Management Procedure 5-5, Surveillance Monitoring, to list actions required when low oil level is identified. The actions will include guidance to detect possible leaks that may not be apparent based on the oil leak rate.

3.Revise Surveillance Rounds checklist, for components bound by mission time requirements, to list the mission time requirement and acceptable oil leak rate.

4.Revise applicable Mechanical Maintenance procedure steps to clarify the need to submit completed enclosures (oil additions) to engineering immediately.

SAFETY ANALYSIS

Duke Energy used a risk-informed approach to determine the risk significance associated with the Technical Specification violation associated with the oil leak on Unit 1 "A" Train NS pump motor.

The Conditional Core Damage Probability (CCDP) and the Conditional Large Early Release Probability (CLERP) of this event were evaluated by considering the following:

• The simplifying assumption that both the "A" NS [BE] Train and "B" NS [BE] Train are unavailable.

• The duration of the Limiting Condition for Operation non-compliance.

• The use of the average maintenance Probabilistic Risk Assessment (PRA) model to represent plant configuration, equipment unavailability, and maintenance activities during this violation.

The CCDP associated with this event was determined to be less than 1.0E­ 06. The CLERP associated with this event is non-limiting with respect to the CCDP and was determined to be less than 1.0E-7.

Furthermore, after the 1A NS [BE] pump was declared inoperable maintenance repaired the leak. There is currently no oil leaking from this motor and it is now operable.

Therefore, this event is considered to be of no significance to the health and safety of the public.

ADDITIONAL INFORMATION

a search of the McGuire Problem Investigation Process (PIP)d To determine if a recurring or similar event exists,d database was conducted for a time period covering 7 years prior to the date of this event. Based on Duke's definition of a recurring event, similar significant event with the same cause code, no recurring events were identified.

Nuclear Energy Institute (NEI) 99-02, "Regulatory Assessment Performance Indicator Guideline", defines a Safety System Function Failure identical to 10 CFR 50.73(a) (2) (v) criteria. Consequently, reporting an event as an event or condition that could have prevented the fulfillment of the safety function of a structures, systems and components constitutes a Safety System Function Failure for the same basis used to deem the reporting criteria was met. This event is being reported under 10 CFR50.73 (a) (2) (v) because the NS [BE] "B" Train was declared inoperable to perform a channel test within the period of time the "A" Train NS [BE] was inoperable for an oil leak. This condition existed for a period of one hour and nine minutes; therefore, the safety system function failure existed for the same time. Although the condition unknowingly existed for a very short time, the safety evaluation assumed "B" Train NS [BE] was inoperable for the duration of time "A" Train NS [BE] was inoperable (14 days) to bound the significance of the condition. The safety analysis determined the condition to "be of no significance to the health and safety of the public.