Nuclear Wastes Storage
There is an increasing emphasis within the United States on the need to mitigate the risks posed by all types of nuclear wastes, including spent nuclear fuel, high-level wastes, transuranic wastes, low-level wastes, and mixed wastes. Radioactive contaminants pose a threat to public health and safety at many sites across the country, and adequate technologies to enable treatment of all types of nuclear waste are not currently available.
As a result, the development of technologies to characterize, retrieve, pretreat, stabilize, and store nuclear wastes is critical. In general, the strategy for "treatment" of radioactive waste first requires identification of what contaminants are present. Pretreatment technologies are then used to minimize the volumes of more dangerous wastes (longer half-lives, more highly radioactive), usually by separating nuclear wastes into smaller volumes of more concentrated high-level wastes and larger volumes of low-level wastes. Each of these types of waste will then be stabilized as appropriate, possibly by vitrification for high-level wastes, and by immobilization in cement or grout for low-level wastes. The stabilized waste will be stored in appropriate repositories: geologic repositories for spent fuels, high-level and transuranic wastes; and approved "disposal" facilities (usually burial sites) for low-level wastes. Although some vitrification plants have been built and are currently at various stages of being brought on-line, more reliable and more cost-effective technologies are still needed for most stages of this process.
The efforts to stabilize and store radioactive wastes are expected to continue for many years. Most estimates indicate that substantial nuclear waste treatment activities can be expected to continue into the second or third decade of the next century. For example, DOE has a stated goal of having its continuing operations in compliance by the year 2019, and of having its surplus or inactive sites either posing, or proceeding safely and smoothly towards posing, no unacceptable risk to public health and safety, or to the environment. Thus impacts (primarily costs) to the U.S. economy will continue well into the foreseeable future.
Nuclear materials storage and disposal technologies contribute to increased security of weapons-grade materials, and to national security of the United States.
Europe is slightly ahead of the United States in technologies for decontamination and decommissioning of nuclear reactors. European firms have worked on decontamination methods such as using fogs or foams containing chemical reagents and in-situ hard chemical decontamination of the tube bundle from a pressurized water reactor steam generator. Methods have been developed for separating radioactive constituents of concrete including active pilot-level testing and recycling of contaminated aluminum, copper, and steel with alpha, beta, and gamma decontamination. Japanese firms are at about the same technology level as U.S. firms. No prototypical facility has yet been decommissioned but work has been done on remodeling, maintenance, and repair. Japanese firms also have experience in decontamination of the sodium removal facility and hot cell maintenance on fast breeder reactors.