Search the Community
Showing results for tags 'evil radiation'.
One of the most commons objections to the use of nuclear power is the waste produced. While nuclear energy produces much less waste by volume than other forms of energy such as coal, the unique properties of the waste mean that there are special challenges associated with disposing of it. In this topic, I'll be talking about high level waste, low level waste has far less challenges associated with its disposal. As not all fissile materials within a fuel element will be used up in a reactor, "spent fuel" (especially that which hasn't been reprocessed) still contains significant quantities of U-235. More importantly, large amounts of fission products with varying half-lives are contained in the fuel. The decay of these fission products generates significant waste heat, which provides the main short-term challenge associated with spent fuel disposal. This site; http://large.stanford.edu/courses/2012/ph241/tilghman1/ gives the following equation for the waste heat produced by spent fuel; P/P0 = 0.066 × [ (t-ts)-0.2 - t-0.2 ] By messing about with various numbers in that equation, you can see that a year after shutdown, waste heat will be about 1/1000 of reactor output. This seems trivial, but for a 1000 MW reactor, that is still 1 MW of waste heat, more than enough to melt a fuel element with no cooling mechanism. (Just as a simple calculation, a fuel element producing 50 kW of waste heat and a .5 m2 surface area in a vacuum would have an equilibrium temperature of about 1150 K). For this reason, spent fuel is usually stored underwater after removal from the reactor; this allows for convective heat transfer and for the mass of water in the pools to act as a heat sink. The water also provides the additional benefit of being a very effective radiation shield. To do list: Long term storage (WIPP, Yucca Mountain) Medium term storage (NRF, dry storage) Safety concerns associated with storage Answer any other questions as much as possible