Antinuclear

Nuclear power plant? Or storage dump for hot radioactive waste?, Bulletin of the Atomic Scientists Robert Alvarez, 11 AUGUST 2016  In addition to generating electricity, US nuclear power plants are now major radioactive waste management operations, storing concentrations of radioactivity that dwarf those generated by the country’s nuclear weapons program. Because the proposed Yucca Mountain nuclear waste repository remains in limbo, and other permanent storage plans are in their infancy, these wastes are likely to remain in interim storage at commercial reactor sites for the indefinite future. This reality raises one issue of particular concern—how to store the high-burnup nuclear fuel used by most US utilities. An Energy Department expert panel has raised questions that suggest neither government regulators nor the utilities operating commercial nuclear power plants understand the potential impact of used high-burnup fuel on storage and transport of used nuclear fuel, and, ultimately, on the cost of nuclear waste management.

Spent nuclear power fuel accumulated over the past 50 years is bound up in more than 241,000 long rectangular assemblies containing tens of millions of fuel rods. The rods, in turn, contain trillions of small, irradiated uranium pellets. After bombardment with neutrons in the reactor core, about 5 to 6 percent of the pellets are converted to amyriad of radioactive elements with half-lives ranging from seconds to millions of years. Standing within a meter of a typical spent nuclear fuel assembly guarantees a lethal radiation dose in minutes.

Heat from the radioactive decay in spent nuclear fuel is also a principal safety concern. Several hours after a full reactor core is offloaded, it can initially give off enough heat from radioactive decay to match the energy capacity of a steel mill furnace. This is hot enough to melt and ignite the fuel’s reactive zirconium cladding and destabilize a geological disposal site it is placed in. By 100 years, decay heat and radioactivity drop substantially but still remain dangerous. For these reasons, the US Government Accountability Office (GAO) informed the Congress in 2013 that spent nuclear fuel is “considered one of the most hazardous substances on Earth.”……..

The impacts of decay heat from high-burnup spent fuel on the internal environment of commercial dry casks are virtually impossible to monitor, according to a 2014 NRC-sponsored study, “because of high temperatures, radiation, and accessibility difficulty.” The uncertainties of storing a mix of high- and low-burnup spent fuel in a canister are compounded by the lack of data on the long-term behavior of high-burnup spent fuel. This problem was highlighted by the Nuclear Waste Technical Review Board, an expert panel that provides scientific oversight for the Energy Department on spent fuel disposal……

Down the road, it is likely that spent nuclear fuel will have to be repackaged to mitigate decay heat into smaller containers ahead of final disposal. High-burnup fuel will only complicate the process, and increase costs, currently estimated in the tens of billions of dollars. Depending on the geologic medium, a maximum of four assemblies for high burnup, as opposed to the dozens in current storage casks, would be permitted after 100 years of decay; larger packages containing no more than 21 assemblies might have to be disposed if there is forced ventilation for 50 to 250 years—driving up repository costs.

The basic approach undertaken in this country for the storage and disposal of spent nuclear fuel needs to be fundamentally revamped. Instead of waiting for problems to arise, the NRC and the Energy Department need to develop a transparent and comprehensive road map identifying the key elements of—and especially the unknowns associated with—interim storage, transportation, repackaging, and final disposal of all nuclear fuel, including the high-burnup variety. Otherwise, the United States will remain dependent on leaps of faith in regard to nuclear waste storage—leaps that are setting the stage for large, unfunded radioactive waste “balloon mortgage” payments in the future. waste? http://thebulletin.org/nuclear-power-plant-or-storage-dump-hot-radioactive-waste9775