Fortnightly speaks with William Johnson, CEO of the Tennessee Valley Authority, about managing the country’s biggest government-owned power supplier.
Is Yucca Enough?
Scenarios depict possible nuclear waste futures.
spent. It is then placed into a cooling pool for storage. Regarded as short-term storage, the spent fuel will reside as little as one, but mostly likely five-to-ten years, in the cooling pool, losing a significant portion of its radioactivity and thermal energy. At this point, the fuel may be placed into dry-cask storage. Each dry cask contains approximately 10 tons 1 of HLW in a cement and steel structure on-site at the nuclear plant. Spent fuel usually is transferred to dry casks after cooling for five-to-ten years in storage pools. Considered a stable and safe option, it is believed that the HLW can remain in dry-cask storage for 50 or more years.
In a closed cycle, spent fuel similarly follows the front-end and operational steps, including pool storage. However, at this point, the spent fuel may be reprocessed to recover primarily the plutonium. This has the attraction of providing greater use of the raw uranium by cycling the fuel and yielding much lower amounts of HLW than does the once-through cycle. Disadvantages include the creation of plutonium that, if stolen, could be used to develop nuclear weapons. Another disadvantage is the additional capital and operating costs associated with reprocessing. If a nuclear fleet isn’t designed with reprocessing in mind, then significant investment is required to recapture the plutonium.
For both open and closed fuel cycles there is a need to permanently dispose of various forms of nuclear waste. There is wide agreement that permanent waste disposal facilities should be sited in highly stable, deep geologic structures. Permanent disposal of nuclear waste is set to a high bar: No nuclear waste may leach into the surrounding biosphere for 10,000 or more years. It also requires transport infrastructure, containment facilities and insulating materials to backfill after burying the waste.
Different countries have focused on alternative types of nuclear-fuel cycles. Principally, these reflect differing views on the perceived advantages of reprocessing nuclear fuel versus relying on mined and enriched nuclear fuel for power generation. The future availability of nuclear fuel doesn’t seem in doubt; however, nuclear fuel prices have risen and appear to be more volatile.
U.S. Storage and Disposal
The United States has not allowed reprocessing of nuclear fuel since the mid-1970s due to concern over weapons proliferation from plutonium produced during nuclear reprocessing. This prompted the U.S. nuclear fleet to accumulate HLW by utilizing the once-through fuel cycle for the last 30 years. In the absence of a Yucca Mountain-like permanent disposal facility, most of this nation’s spent fuel is resting in cooling pools, often 40 or more feet deep, located at the nuclear plant sites. As spent fuel fills the cooling pools over time, operators have moved an increasing quantity of spent fuel to dry-storage casks. Scattered throughout the nation are about 56,000 total metric tons of HLW with about 2,000 additional metric tons created per year.
At this rate, the United States easily will exceed the original legislated HLW total allowed storage capacity of 70,000 metric tons at Yucca Mountain years before the 2017 cut-off date; however, the current 70,000