Nuclear fuel element, core for nuclear reactor, nuclear fuel material

The nuclear fuel material includes up to 1% of plutonium and the remainder enriched uranium of an enrichment necessary to achieve a desired fissile content. A typical nuclear fuel material includes 0.160% fissile plutonium or 0.216% total plutonium and 784 uranium of 3.171 enrichment in uranium 235. This mat replaces 100% uranium of 3.30 enrichment. There is also disclosed a nuclear fuel element with the above-described fuel material and a nuclear reactor fueled by such elements. There is further disclosed wet methods of treating spent nuclear fuel wherein the appropriate quantity of enriched uranium to achieve the desired fissile content is added to the solution of uranium and plutonium after separation from the fission products or to the solution of plutonium alone after separation of the plutonium from the uranium