Heat extracted from nuclear fuel costs by a factor of 3 to 7 less than heat from conventional fossile fuel. So, nuclear fuel per se has an economical advantage, decreased however partly by higher nuclear plant investment costs. The standard LWR design does not allow all the fission energy stored in the fuel during on cycle to be used. It is therefore the most natural approach to separate fissionable species from fission products and consume them by fissioning. Whether this is economically justified as opposed by storing them indefinitely with spent fuel has widely been debated. The paper outlines the different approaches taken by nuclear communities worldwide and their perceived or proven rational arguments. It will balance economic and other factors for the near and distant future including advanced reactor concepts. The specific solution within the German nuclear programme will be explained, including foreseeable future trends. (orig.).