Updated seismic guidelines from the Nuclear Regulatory Commission resulted in spent nuclear fuel being staged underground to prevent casks from potentially tipping over during loading. This created the opportunity for Konecranes to approach the problem of dry cask storage in a totally new way.
"The stackup pad is a recessed below-ground area where the can is secured by walls so that it can't fall over," says Matt Nemet, regions sales manager for Konecranes Nuclear Equipment and Services.
"The biggest advantage of the new Konecranes design, with patent-pending concepts, is that we use quick-connecting single failure proof crane hoisting machinery to reach down and pick up the cask and canister. Older machines require workers to rig heavy slings to pick it up, which is time-consuming and labor-intensive and can potentially increase radiation 'dose' exposure," Nemet continued.
Nemet estimated that the crane-based equipment reduces loading time by as much as 50 percent, making the Konecranes solution substantially more efficient and aligned with facility ALARA exposure goals (As Low As Reasonably Achievable).
Konecranes single failure proof vertical cask transporter (VCT) also helps prevent damage to infrastructure. Plants using steel track transporters must spend money after each storage campaign to repair the concrete on roads and turning pads. In contrast, the Konecranes VCT cradles each 210-ton cask on 16 wheels with special foam-filled, high-end airplane tires that alleviate much of the road damage.
Konecranes new NOG-1 compliant design also has a number of redundant hydraulic and electrical safety features. Emergency hoist lowering is provided to safely lower a load during the unlikely event of a hoist system failure. The emergency lowering system is designed to safely lower the load at a controlled speed, even during a complete loss of crane power. An HMI interface gives the operator a stream of diagnostic feedback about how the machine is working, allowing him to check key crane control functions and simplify troubleshooting.
"After delivering the first of these machines we have been able to document a lot of benefits," says Nemet. "The customer's first cask loading operation had enormous success in keeping dose levels low, while maintaining the safety, efficiency and timetable of their storage campaign. It is now clear that Konecranes SUPERSAFE™ single failure proof technology was exactly what we needed to make the first NOG-1 compliant Vertical Cask Transporter a reality."