I have talked about temporary storage of spent fuel rods in dry casks of steel and concrete in previous posts. It is estimated that all the spent fuel pools at all the U.S. reactors will be full in five years unless another storage/disposal method is found. The U.S. DOE now says that it will take at least thirty years to site and build a permanent geological repository for spent fuel. So it is obvious that dry casks are going to be very important for the nuclear industry in the short term.
The U.S. Nuclear Regulatory Commission licensed the first dry cask storage facility in the United States in 1986 at the Surry Nuclear Power Plant in Virginia. During the 1990s, the NRC had to deal with numerous problems in dry cask construction including defective welds that caused cracks. In some of the casks, helium had leaked out of the fuel rods and into the outer shell of the cask. This increased temperatures and speeded up corrosion in the casks. In 2008, the NRC issued new guidelines that required spent fuel rods to be stored in a spent fuel pool to cool off for at least five years before being placed in dry casks.
Although the nuclear industry has doubled the potency of fuel rods since 1970, the design of dry casks has not kept pace with the increasing potency. There have been warnings about the increasing radioactivity of what are referred to as high-burn up fuel rods for years. Recently, Argonne National Laboratory has been pointing out that they have research that indicates that the new fuel rods may become brittle over time while they are stored in the casks. Since the casks are intended to be a temporary storage option until a permanent geological repository can be built, the rods would have to be removed from the casks at some future time for transportation. If the rods are brittle, they might disintegrate when removed from the casks increasing the risk of radioactive material entering the environment.
. Spurred by concern that no one knows exactly what is happening inside the dry casks that currently exist, the Department of Energy and the nuclear industry’s Energy Power Research Institute are launching a new project to deal with this problem. The project will develop new lids with built in instrumentation for new dry casks. Sixteen million dollars and four years have been allocated for the project. The new lids will take samples of gas for analysis and will monitor temperatures in the casks as well as other conditions. The new lid systems will have to be able to withstand high temperatures and high levels of radiation, have some way of removing energy from the casks, operate on battery power for over ten years and transmit information wireless to outside receivers. It is hoped that there will be a prototype of a new cask with the advanced lid available for tests by 2017.
Since the soonest that we will have permanent storage in the U.S. is thirty years out, it is very important that the spent fuel rods and the dry casks that they are stored in maintain their structural integrity for decades. It may be a little late but the new lid project is a welcome change.
