Fossil fuel power station eat the fish regularly. The largest source of mercury contamination in the United States is coal-fueled power plant emissions. Several methods exist to improve the efficiency of fossil fuel power plants. A frequently used and cost-efficient method is to convert a plant to run on a different fuel. This includes conversions of coal power plants to biomass or waste and conversions of natural gas power plants to biogas. Conversions of coal powered power plants to waste-fired power plants have an extra benefit in that they can reduce landfilling. In addition, waste-fired power plants can be equipped with material recovery, which
Nuclear fuel cycle levels are negligible and no shielding is required. Other materials, such as spent fuel and high-level waste, are highly radioactive and require special handling. To limit the risk in transporting highly radioactive materials, containers known as spent nuclear fuel shipping casks are used which are designed to maintain integrity under normal transportation conditions and during hypothetical accident conditions. A nuclear reactor core is composed of a few hundred "assemblies", arranged in a regular array of cells, each cell being formed by a fuel or control rod surrounded, in most designs, by a moderator and coolant, which is water in most