September-October 2018 NPJ

Nuclear Plant Journal, September-October 2018 NuclearPlantJournal.com 37 inoperable. Wear beyond the criteria limit could potentially cause the control rods to not insert. The rodlets are thin, and if one moved slightly off course rather than passing smoothly through the intended space of the guide card, it could potentially plastically deform or buckle. After investigating the best interim solution for the plant in Spain, Westinghouse ultimately selected a particular guide plate, called the special guide plate, as ideal for replacement. Importantly, the special guide plate’s location within the guide tube makes it one of the limiting six consecutive guide cards, allowing its replacement to extend the affected guide tubes’ operability. Also, in Westinghouse 17x17 A, AS or AXLR style guide tubes, the special guide plate is bolted to the guide tube, allowing for easier removal and replacement, unlike the other guide cards within the tubes, which are either pinned or welded. Inspired by the AP1000 ® nuclear power plant’s guide tube design, which incorporates thicker special guide plates throughout, Westinghouse devised similar plates for the plant and alleviated the option of immediately replacing the guide tubes. Westinghouse began replacing worn special guide plates with new, thicker special guide plates at the plant in Spain in 2013 and has, over the course of four outages, replaced 55 to successfully extend the operating service of the affected guide tubes. To do so, the company designed specialized tooling for both replacing the worn special guide plates and for performing profile inspections once the thicker special guide plates were installed. Inspecting the profiles of the thicker special guide plates helps ensure that the specification limit for rod drop time will be met during rod drop testing and if needed due to an event. The feedback and support from plant personnel have been crucial to the successful implementation of this contingency by Westinghouse. While the thicker special guide plate contingency provides short-term relief, that is, an expected two to three additional fuel cycles of operation, plant personnel expressed interest in a longer term solution to avoid frequent replacements and inspections. In 2015, Westinghouse began working on an innovative component to meet that goal, which resulted in the continuous special guide. Westinghouse finalized the continuous special guide design following several design iterations based on plant personnel’s input and feedback, and on feasibility assessments. The continuous special guide design is inspired by the continuous section design of the guide tube itself. Westinghouse’s goal with the new continuous special guide design was to maximize volume for the holes most susceptible to wear to extend operability. The analytical qualification of the continuous special guide has been completed. A full-scale pressure, temperature and flow rod drop time Continuous Special Guide. qualification test, which will complete the qualification effort for the continuous special guide, is planned to commence in November 2018. Upon qualification, the Westinghouse continuous special guide will be available for manufacture and subsequent implementation. With an expected guide tube wear life benefit of six to nine refueling cycles for the Spanish plant, the continuous special guide promises to be a much longer term solution as compared to the thicker special guide plate or the original special guide plate. Contact: Donna Ruff, Westinghouse Electric Company, telephone: (412) 374- 4705, email: ruffdl@westinghouse.com. Highly Worn Guide Card. Unworn Guide Card.