May-June 2018 NPJ

44 NuclearPlantJournal.com Nuclear Plant Journal, May-June 2018 Water Pump... ( Continued from page 43) addition, personnel were working on scaffolds. There were no safety or human performance events for FOAK tasks that spanned two different deployments – over 8 weeks. Until the valve disc was stabilized, the valve could open at any time due to the backpressure placed on the valve disc, diverting cooling water from the plant back to the Mississippi River. The impact on the plant would challenge operations and the ability to maintain 100% power. The risk of CW-103C opening was eliminated when the stabilization pins were inserted. Cost Savings When CW-103C was restored and the 4th Circulating Water Pump was restored, the need to de-rate the unit during the summer was eliminated, and the cost associated with down power - ~$5.4M. The completion of the on-line repair eliminated the need for an approximate 10 day forced outage to replace CW-103C which eliminated the associated cost. When the repair pin was inserted, connecting the valve disc and stem together, the ability for 4 Circulating Water Pump operation was restored. Restoration of the CWPump C eliminated the potential to de-rate the unit based on Mississippi River temperatures as well as performance of additional waterbox cleaning. The project team implemented a solution that ultimately:  Eliminated potential for forced shutdown.  Saved Waterford ~$5.4M.  Improved plant reliability.  Reduced enterprise risk.  Ensured reliable 100% power production during the peak summer season. Vision and Leadership Framatome worked with Entergy to develop a solution on an accelerated schedule when no other vendor was willing to take on the challenges associated with this project. The Project team developed an innovative solution that kept the plant online with no safety or quality issues. Entergy invested time and resources on a high risk project with a well defined schedule established to drive it to success. Gate reviews were established along the way – a scoping study was done to launch the project with demonstrations, independent reviews, design reviews, analytical reviews, third party reviews, and status reviews to follow, in preparation for execution. Productivity/Efficiency The team met an accelerated / emergent schedule for the stabilization phase. Stabilization was scheduled for May – Framatome met an accelerated schedule by delivering in April. The use of mockups improved productivity and efficiency by uncovering potential challenges and therefore giving an opportunity to remove those challenges prior to project execution. During the mockup phase, the team decided to design two different size pins for a solution to potential challenges incurred throughout the drilling process that could cause slight variances with pin fitment. Although various cameras were in place to support the process, we knew that water clarity of the Mississippi River would provide vision challenges. The 84" mockup valve allowed us to validate that we could continue to work blind, using only measurements to accurately verify drill depths, positions, and pin installation. Before taking the repair to the field, we were able to use a specialized drill bit to allow the process to be more predictable on site in removing chips and allowing the drilling operation to continue once started, minimizing interruptions. The use of gauges along with the ability to observe the process on the mockup, proved to be invaluable in regards to safety and efficiency both technically and with schedule. Transferability This unique approach is applicable at all plants that experience this type of failure on an 84" or 96" butterfly valve. The isolation valve has a history of pin failures, and the innovative repair approach offers utilities a way to handle this situation without having to shut down. The solution is not limited to the nuclear industry – it can also be used in fossil fuel units and transferred to the general industry as well. Contact: Dan Frey, Entergy, telephone: (504) 464-3490, email: Dfrey@entergy.com .