05000530/FIN-2016001-02
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Finding | |
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| Title | Fatigue failure of pneumatic fitting due to excessive vibrations |
| Description | The inspectors documented a self-revealing non-cited violation of Technical Specification 3.7.2 Condition A for exceeding the allowed outage time of seven days. Specifically Unit 3s MSIV-181 actuator B was found to be inoperable from May 1, 2015 until August 15, 2015 when a design change installed a new swivel type fitting on an air-line without taking into account vibrational forces, as required by the stations procedure. This eventually resulted in the fatigue failure of the fitting, depressurizing the actuator B to less than 5000 psig. The licensee entered this condition in their corrective action program and performed a Level 2 cause evaluation under Condition Report 15-02686. The inspectors concluded that the failure to take into account excessive vibrational stresses as required by procedure 81DP-0EE10, Design Change Process Step J.2.9.1, when implementing the design change was a performance deficiency. The performance deficiency was more than minor because it affected the equipment performance attribute of the Mitigating Cornerstone to ensure the availability, reliability, and the capability of systems that respond to initiating events to prevent undesirable consequences. Specifically the failure to account for the vibrational stresses resulted in the fatigue failure of the air-line fitting which depressurized one of two hydraulic accumulators thereby reducing the reliability of the system to initiate a fast closure of MSIV-181 upon receipt of a Main Steam Isolation Signal. The inspectors performed the initial significance determination using NRC Inspection Manual 0609, Appendix A, Exhibit 2, Mitigating Systems Screening Questions, Issue Date: 06/19/12. The finding screened as Green since the MSIV remained capable of performing its safety function with the alternate accumulator. The finding has a cross-cutting aspect in the area of human performance associated with the avoid complacency component. Specifically the licensee assumed there were no factors affecting the mechanical design requirements beyond the performance requirements. As a result the licensee failed to perform a thorough review of the mechanical conditions (such as vibrations) the air-line was subjected. |
| Site: | Palo Verde  |
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| Report | IR 05000530/2016001 Section 4OA3 |
| Date counted | Mar 31, 2016 (2016Q1) |
| Type: | NCV: Green |
| cornerstone | Mitigating Systems |
| Identified by: | Self-revealing |
| Inspection Procedure: | IP 71153 |
| Inspectors (proximate) | C Peabody D Reinert D You J Josey L Carson N Greene |
| Violation of: | Technical Specification - Procedures Technical Specification |
| CCA | H.12, Avoid Complacency |
| INPO aspect | QA.4 |
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Finding - Palo Verde - IR 05000530/2016001 | ||||||||||||||||||||||||||||||||||||
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Finding List (Palo Verde) @ 2016Q1
Self-Identified List (Palo Verde)
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