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A self-revealing Green NCV of 10 CFR 50, A … A self-revealing Green NCV of 10 CFR 50, Appendix B, Criterion III, Design Control, was identified because Exelon failed to control the proper design configuration of installed plant equipment in Unit 1. Specifically, a fitting used in the safety-related primary containment instrument gas (PCIG) tubing supplying the 1C inboard main steam isolation valve (MSIV) was not installed in accordance with the specified quality standard and this deviation was not controlled. Subsequently, the fitting failed due to high cycle fatigue and caused a reactor trip. Exelons corrective actions included initiating condition report IR 2458005, installing approved tubing and fittings on February 24, 2015, on the 1C inboard MSIV which maintained wall thicknesses greater than original specifications, and verifying that current maintenance practice, training, and knowledge would preclude substitution of a different style fitting without further evaluation. This finding is more than minor because it is associated with the design control attribute of the initiating events cornerstone and affected the objective to limit the likelihood of events that upset plant stability during power operations. Specifically, the inadvertent closure of the 1C inboard MSIV resulted in a reactor trip. Using IMC 0609, Significance Determination Process, Appendix A, Exhibit 1, Initiating Events Screening Questions, the inspectors determined that this finding was of very low safety significance (Green) because the finding did not cause a reactor trip and the loss of mitigation equipment relied upon to transition the plant from the onset of the trip to a stable shutdown condition (e.g. loss of condenser, loss of feedwater). Specifically, the finding caused the loss of one steam line to the main condenser but three steam lines remained available. The inspectors determined that the finding did not have cross-cutting aspect because the installation of the fitting that failed did not occur within the last three years, and the inspectors did not conclude that the causal factors represented present Exelon performance.rs represented present Exelon performance.
23:59:59, 30 June 2015 +
23:59:59, 30 June 2015 +
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12:57:36, 25 September 2017 +
23:59:59, 30 June 2015 +