A finding of very low safety significance was self -revealed on November 19, 2011, when a reactor
scram occurred during planned turbine-generator testing, as a result of the sites failure to effectively monitor and control turbine
lube oil (
TLO) tank vacuum and perform turbine shaft voltage monitoring in accordance with vendor recommendations. The mismanagement of the ability to monitor and control
TLO tank vacuum led to the fouling of turbine shaft grounding braids and subsequent degradation of the turbine speed governor drive gears through electrolysis. The degradation of the front standard components ultimately resulted in control oil pressure oscillations during speed load changer testing, which activated the load rejection pressure switches and scrammed the plant. Corrective actions taken by the licensee to address this issue included repairing the speed governor gear drive and main shaft oil pump components; installing a more robust shaft grounding strap; improving the instrumentation on the
TLO tank and adjusting the control bands on the operator logs; and developing a revised testing methodology for generator electrical checks to include vendor recommendations. The inspectors determined that the licensees failure to effectively monitor and control
TLO tank vacuum and perform turbine shaft voltage monitoring in accordance with vendor recommendations was a performance deficiency because it was the result of the failure to meet a requirement or standard; the cause was reasonably within the licensees ability to foresee and correct; and should have been prevented. The inspectors screened the performance deficiency per
IMC 0612, Power Reactor Inspection Reports, Appendix B, and determined that the issue was more than minor because it impacted the procedure adequacy attribute of the
Initiating Events Cornerstones objective to limit the likelihood of those events that upset plant stability and challenge critical safety functions during shutdown as well as power operations. The inspectors applied
IMC 0609, Attachment 4, Phase 1 Initial Screening and Characterization of Findings, to this finding. The inspectors evaluated the issue under the
Initiating Events Cornerstone, and utilized Column 1 of the Table 4a worksheet to screen the finding. For
transient initiators, the inspectors answered No to the question, Does the finding contribute to both the likelihood of a
reactor trip AND the likelihood that mitigation equipment or functions will not be available? and determined the finding to be of very low safety significance. The inspectors determined that the most significant causal factor associated with the performance deficiency was associated with the cross-cutting area of Human Performance, having resources components, and involving aspects associated with procedures are available and adequate to assure nuclear safety
