UMS Technology: NAC’s First Universal Spent Fuel Storage and Transport Solution


When DOE terminated its Multi-Purpose Canister (MPC) program in late 1995, the time was right to move forward with a private sector initiative. NAC launched a program to design and license a system that could handle virtually all types of PWR and BWR fuel used in U.S. and international commercial plants. NAC based the UMS on the licensed NAC-STC basket and transport overpack designs, enabling it to push forward quickly with system development. Given the familiarity of the evolutionary design, NAC set licensing targets that would allow the UMS to meet utilities' urgent spent fuel needs before 2000.

The UMS™ provided a single system that embodies the low cost of a storage-only system, the transportability of a dual-purpose canister-based system, and the canister benefits envisioned in the former DOE MPC program. The UMS was the first U.S. system designed to meet the requirements of virtually every U.S. utility, with ongoing hands-on involvement by U.S. utilities and worldwide fabrication team members.
The UMS was engineered to simply provide an excellent and safe system for storing and transporting nuclear fuel. The UMS has four primary components: the transportable storage canister, the vertical concrete cask storage overpack, the technologically proven universal transport cask overpack and auxiliary equipment, including the transfer cask. A transfer cask will move the transportable storage canister from the pool to the vertical concrete cask for storage, where it remains in the vertical concrete cask until it is transferred to the universal transport cask overpack at the time of shipment off site.

Superior design and technology are only as good as the supplier's ability to fabricate and deliver the system on time. For the UMS, NAC implemented a comprehensive fabrication program that has led to uniformly reliable deliveries with the requisite high quality level for more than 240 systems.

NAC also incorporated other key features in its UMS design and development program:
  • A licensed impact limiter design that uses results from comprehensive drop tests on a quarter-scale model of the NAC-STC
  • Multiple basket configurations to accommodate a full range of BWR and PWR fuels
  • A hands-on transport and operations-based design perspective
  • A comprehensive design review by engineers and manufacturers to ensure that system component designs are easily and efficiently fabricated
  • An integrated quality assurance program from start to finish.

The UMS has a capacity of 24 PWR or 56 BWR fuel assemblies. Based on its experience developing other spent fuel transport and storage systems, NAC established a capacity for the UMS that was large enough to economically meet utility needs, but within a reasonable licensing envelope to allow early deployment, a strategy that proved to be quite successful.