Part 3 of 3 Parts (Please read Part 1 and Part 2 first)
     One of the leading companies that manufactures dry casks for the storage of spent nuclear fuel is Orano. They have been researching, developing and constructing dry casks for four decades. Orano is the first manufacturer of dry casks to work with the U.S. Nuclear Regulatory Commission.
      The company has designed and certified both metal storage casks and canister-based storage systems. They have recently developed their NUHOMS system of individually stored and welded canisters. These are horizontally positioned inside heavily shielded square concrete modules on spent fuel storage pads onsite at nuclear power plants.
      Orano’s most advanced high-capacity extended optimization storage canisters are now licensed to store spent nuclear fuel with high burnup characteristics of up to fifty kilowatts high heat load. The highest heat load that the canister industry could handle before the latest Orano canisters was thirty-four kilowatts. Interim dry storage of spent fuel at reactor sites has been extended beyond the initial twenty-year license period. Now Orano has managed to extend the licensing period for their NUHOMS onsite dry storage system to sixty years. Orano has also reduced the space required by their onsite dry storage pads by forty five percent for the same amount of fuel. In order to accomplish this, they developed the two-tiered MATRIX dry storage modules, which allow utility customers to not have to expand their dry storage facilities. This, of course, reduces costs.
     Dry canister storage availability does not remove the need for storing spent fuel in cooling pools at operating commercial nuclear power plants. However, the inclusion of dry storage does provide a further intermediate storage stage prior to permanent disposal which could be much cheaper.
     Wet storage is known to require a significant amount of energy. Comparative research has been published in the journal Annals of Nuclear Energy with the title “Cost comparisons of wet and dry interim storage facilities for PWR spent nuclear fuel in Korea”. The research report stated that wet storage was the most expensive solution for decommissioning spent fuel from a pressurized water reactor when compared to three different dry storage systems. This indicated that if the additional stage of dry storage was added to the decommissioning process, companies could benefit from substantially reduced maintenance costs.
      Prakas Narayanan is the chief technical officer for Orano. He pointed out another significant advantage of dry storage is the fact that it is expandable. He said, “Wet storage capacity at nuclear power plants is limited and cannot be significantly increased. Dry storage offers an important advantage with modular, expandable storage to support the continued, long-term operation of the nuclear energy facility. Transferring quantities of spent fuel assemblies from wet storage in the reactor building pool into large capacity, sealed dry storage canisters and then placing the canisters into dry storage modules in a separate dry storage facility provides many benefits to the energy company and surrounding community.”
     Opponents of dry storage have shared concerns about the dangers of transporting volatile nuclear waste for dry storage. They are also concerned about the level of radioactivity that nuclear plant workers may be exposed to. They point out that wet storage does not require that the spent nuclear fuel be moved because it stays in the cooling pool long term. This means that workers have easier access to the spent fuel that allows them to detect problems quickly.
      Proponents of dry storage reply to opponents concerns by insisting that the spent fuel is not very volatile, the canisters are welded shut, and advanced ageing management tools are being developed for the safe inspection of the canisters in dry storage.
      Narayanan says that “For greater economic efficiencies, fuel assembly designs are becoming more robust and less prone to fuel failure, [in order to] to provide increased operating power with increased initial enrichment and higher burnups.” Although this could create new challenges for those managing spent fuel assemblies, he is confident that the new dry storage systems are already capable of dealing with this future need of the nuclear industry.
     Whether or not dry storage will gain enough recognition to become as popular as wet storage around the globe remains to be seen. In either case, handling the spent fuel disposal problem is already one of the most important steps toward the desired clear energy future and it will require substantial effort, regulation and financing.