Baffle bolt inspection and emergent clevis repair provide comprehensive support

As part of the nuclear industry’s rigorous attention to safety, nuclear plant equipment is continuously monitored, inspected and repaired or upgraded when necessary. Safety-related stainless steel baffle bolts are regularly inspected as they secure the removable liner plates around pressurized water reactor core. During these inspections, reactor internals degradation and baffle bolt indications began to show. Recent industry events have led to a heightened awareness and the need for a solution if indications are found.

 

Framatome offers nuclear plant operators a roadmap for baffle-to-former bolt evaluation that includes risk-based modeling, award-winning inspection capabilities and extensive replacement experience. We provide comprehensive support for reactor internals inspection, analysis and repair. This allows plant operators to proactively plan examination intervals, replacement patterns and outage duration — all to control costs.

 

In the spring of 2020, we were at a customer site for a first-of-a-kind 2-Loop MRP 227 inspection of the plant’s reactor vessel internals which included inspection of the baffle-former bolts. The team provided comprehensive support that included inspection of the reactor vessel internals, probabilistic analysis and solutions for emergent repair scenarios, and contingency repair personnel on standby to support emergent repairs.

 

Success for baffle bolt analysis methodology

Throughout the outage, while NDE team members performed the ultrasonic inspection (UT) of the baffle-to-former bolts, our engineering team was ready to assess any scenario that the inspection might uncover. Using the UT data, the team utilized our newly-patented probabilistic analysis methodology to evaluate the baffle bolts in real-time. This allows the team to predict the remaining bolt life and provide replacement solutions for emergent repair scenarios. We were able to determine the acceptability of the assembly within several hours of completing the exam, avoiding an emergent repair.

Our new probabilistic methodology for baffle bolt analysis served as a key differentiator in winning the work to support the customer during the plant’s spring outage. The successful deployment of this new methodology clearly demonstrates that we’re innovating to develop safe and competitive solutions that help us meet our customers’ needs, and our research and development efforts are paying off.

Innovative tooling developed for emergent clevis repair

When an emergent issue arose for the customer, our team was ready to spring into action. During remote visual inspection, the team discovered that a lower radial support system (LRSS) clevis insert had separated from the clevis, possibly preventing proper installation of the lower internals. Normally, this insert is held in place by an interference fit, eight bolts, and a dowel pin. Inspection revealed that the bolt heads and dowel pin were captured within the recessed portions of the insert with welds intact but the clevis was out of position.

Knowing our contingency repair team was on standby, the customer reached out to Framatome for help in developing a solution to address the displaced LRSS clevis inserts. The repair team designed and fabricated an innovative push-and-lift tool to reseat the clevis insert in its proper location — and the tool performed flawlessly. The utility customer’s project manager shared that “The pusher tool was developed, delivered and implemented in very short time — the tool performed its function as promised.”

The customer, concerned with what the inspection team might find and if they would run into any significant challenges for the baffle bolts, shared that they were pleased with our performance. We demonstrated that we know how to perform baffle bolt work — and we did it as a unified team performing with excellence. With the team’s expertise, diligence and hard work, this project was successful both for us and the customer.