05000250/FIN-2011008-02
From kanterella
Jump to navigation
Jump to search
Finding | |
|---|---|
| Title | Molded Case Circuit Breaker Testing |
| Description | The age range of approximately 511 safety-related MCCBs at Turkey Point is twenty to forty years - some are original plant equipment, some were installed in the 1980s, and the remainder in the early 1990s. With the exception of bench testing prior to installation, no testing/maintenance has been performed on the breakers. MCCBs are susceptible to age related failures such as, overheating due to loose connections and long term grease hardening. Overheating can exceed material temperature ratings, distort motor control center case and operating mechanism tolerances, and result in hardening/baking of grease. Long term grease hardening can result in the breaker failing to open or a delay in opening during a downstream electrical fault. NRC Information Notice (IN) 93-64, Periodic Testing and Preventive Maintenance of Molded Case Circuit Breakers, states, in part: MCCB preventive maintenance practices can mitigate the effects of aging and help ensure continued MCCB reliability, and that certain standard MCCB tests (such as individual pole resistance, 300 percent thermal overload and instantaneous magnetic trip tests) performed periodically were found effective along with the additional techniques of infrared temperature measurement and vibration testing. Also, EPRI NP-7410, Section 7.3.1, states, that ensuring that all MCBs are periodically exercised is considered a vital part of a maintenance program, applicable to all breakers regardless of their safety classification. In addition, EPRI/NMAC NP-7410-V3, Section 7.3.1, states that safety related MCCB cycling/trip testing should be performed on a 4 to 6 year frequency. In 2005 and 2006, during Turkey Points preventive maintenance optimization (PMO) project, the licensee identified the lack of a testing program for safety-related 120vac and 120vdc MCCBs which resulted in the creation of a preventative maintenance (PM) program for the breakers. The PMs for the 120Vac breakers were to include a periodic inspection and electrical test to verify functionality. The PMs for the 125Vdc breakers were to replace each individual breaker. However, the licensee suspended the PMs, in part, because of scheduling challenges associated with Technical Specification (TS) restrictions the TS has a two hour action statement associated with the deenergization of the ac or dc load centers. In 2008, in response to the cancelled PMs, CAR 08-069 was created and assigned as a Turkey Point Excellence (TPE) project. TPE considered several options, and decided on a one-time replacement of the vital 120Vac and 125Vdc breakers. In 2010, the licensee initiated AR 1649834 because the funding for the TPE project was terminated. This AR created a new long term asset management initiative to re-target the project in future years. In 2011, ECR 1657020 was created for a one-time replacement of the MCCBs and entered into the licensees long term asset management program (PTN-11-0177 [U3] and PTN -11-0179[U4]. The team identified that since 2005/2006 when the lack of periodic testing of the MCCBs was identified; no interim measures were taken to correct the nonconforming condition. Specifically, on multiple occasions since 2005, the licensee failed to take adequate actions to ensure the reliability and capability of the MCCBs to perform their design function while pursuing long term strategies. Additionally, the team identified that the licensee failed to scope the protective tripping function of the MCCBs in the Maintenance Rule program. These issues were entered into the licensees corrective action program as ARs 1675539 and 1676808 which include developing an interim strategy that is to consider visual inspections augmented by thermography, planned cycling, and testing of the MCCBs. |
| Site: | Turkey Point  |
|---|---|
| Report | IR 05000250/2011008 Section 1R21 |
| Date counted | Sep 30, 2011 (2011Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71111.21 |
| Inspectors (proximate) | D Jones G Skinner D Mas-Penaranda M Yeminy R Patterson B Desai E Stamm D Terri-Wardj Riverar Kellner W Pursley M Riley W Loo T Hoeg M Barillas D Mas-Penaranda D Rich C Fletcher |
| INPO aspect | |
| ' | |
Finding - Turkey Point - IR 05000250/2011008 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Finding List (Turkey Point) @ 2011Q3
Self-Identified List (Turkey Point)
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||