[en] Energy is an essential element for human species; in developing countries it derives the country's economic growth, while in developed countries improves the quality of lives of people. As the world more economically developing in the future, more energy demand is expected, but this accompanies two inherent limitations: 1) the fossil fuels are limited resources and not able to supply worlds energy demands indefinitely and 2) the use of fossil fuels generates a large amount of greenhouse gas emissions harmful to the environment. 'Nuclear energy' seems to be an answer to solve these problems; increasing interests have recently shown over 'nuclear energy' as an alternative energy source to fossil fuels. Although it is a more technology-intensive energy source compared to others, however, it still needs a raw material uranium to produce electricity. Uranium is also a limited resource. For this reason, for a government to craft its long term energy policy, it needs to know how much uranium is preserved and how long it will support the country's nuclear power generation. Although many analysts so far speculate that the existing known uranium resource would be sufficient to support the nuclear power plants of the world at least until mid-century, most of those analyses assume a small rise in nuclear electricity generation in the short-term, and then a gradual decline in the long-term. Recently rising expectations and a possible renaissance for nuclear power, however, call for new analyses on this issue. This paper projects the future contribution of nuclear power to the world energy mix reflecting such a change of the atmosphere. Based on that projection, this paper analyzes how long uranium will be available for nuclear power generation