Operated from 1972 to 1996 and produced 119 billion kilowatt hours of energy
Dry cask storage is a method for safely storing spent nuclear fuel after it has cooled for several years in water pools. Once the fuel rods are no longer producing extreme heat, they are sealed inside massive steel and concrete casks that provide both radiation shielding and passive cooling through natural air circulation—no water is needed. Each cask can weigh over 100 tons and is engineered to resist earthquakes, floods, fire, and even missile strikes. This makes it a robust interim solution until permanent deep geological repositories are available. The casks are expected to last 50–100 years, though the fuel inside remains radioactive for thousands. Dry cask storage reduces reliance on crowded spent fuel pools, provides a secure above-ground option, and buys time for nations to develop long-term disposal strategies. In essence, it’s a durable, self-contained “vault” for nuclear waste
Dump it in water, heat it up, use the heat for heating. You don't need it to be the most efficient, you only need to not waste it.