As today’s power industry grapples with the pressing need to extend the life of its operating nuclear plants, managers are learning that few elements of the plant infrastructure offer more opportunity for renewal than its cranes.
Jay Edmundson, P.E., P.Eng., Vice President of Engineering, Konecranes Nuclear Equipment & Services LLC
The nuclear power industry in the United States dates back to the late 1970s and early 1980s. By 2020, there were 92 working nuclear power plants in the U.S., with most operating for more than their initial 40-year license. Because of the massive potential consequences of a failure, cranes that handle nuclear material are required to include additional safety systems including single-failure-proof, pushing reliability to extreme levels. Those outside the industry may wonder, how is this feasible, operating with 40-year-old equipment?
Like many cranes of this era, the workhorse polar, reactor and fuel handling cranes in older nuclear power plants were over-engineered in a major way. Because they are mainly used during outages, even today these cranes still offer decades of useful life in their structural components. However, other critical parts are fast reaching the end of their economic service life. Obsolescence of early-era electrical controls is an enormous problem for plant managers, with unavailable parts and a shortage of craftsmen familiar with the aging equipment topping the list of issues. So today’s crane modernization experts must walk a fine line between optimizing equipment life and maintaining the levels of extreme reliability expected in a nuclear power plant.
Squeezing more out of less
With power needs increasing and the construction of new nuclear plants extremely expensive, current industry thinking is that existing nuclear plants need to remain in operation for at least 60 years. Crane modernization is a realistic avenue to extend equipment life while complying with stringent and evolving safety regulations.
Plant managers are also facing increasing production demands: when electrical turbines aren’t turning, plants aren’t making money. Downtime is costly, so planned maintenance outages when modernization can occur are often shorter than they used to be. A typical outage occurs every 18 months, lasting approximately 21 to 28 days. Whatever a professional modernization team can do to get the plant back on line within the expected time frame can save their customer $1.5 to $2.5 million per day.
Where opportunity lies
The key players in any nuclear crane modernization scenario are the polar crane and the fuel handlingequipment, both located near the reactor which designates highest-risk activity.
The polar crane or reactor crane is used for removal and replacement of the reactor head and upper components of the reactor. Moving on a circular or straight track runway, it also lifts and moves all components in and out of the containment building, so it is the workhorse of the outage. It has both a main and an auxiliary hoist, which perform typical plant maintenance and operational functions. The cranes may also have a maintenance jib crane for maintaining the crane itself, and/or a containment inspection man lift used for inspecting and maintaining the containment dome.
All of these lifting systems can benefit from increased reliability and productivity by upgrading the control system using AC variable frequency drives or other commercially available control systems. This upgrade eliminates the parts sourcing and labor problems associated with the original outdated controls and makes crane operation more cost-effective for the plant. In addition, plants can add another layer of safety with single-failure-proof trolleys and proprietary closed-loop software options that control the operational path of the crane and protect specific areas.