While reprocessing offers the potential recovery of up to 95% of the remaining uranium and plutonium fuel, in spent nuclear fuel and a reduction in long term radioactivity within the remaining waste. Reprocessing has been politically controversial because of the potential to contribute to nuclear proliferation and varied perceptions of increasing the vulnerability to nuclear terrorism and because of its higher fuel cost, compared to the once-through fuel cycle. Similarly, while reprocessing reduces the volume of high-level waste, it does not reduce the fission products that are the primary residual heat generating and radioactive substances for the first few centuries outside the reactor, thus still requiring an almost identical container-spacing for the initial first few hundred years, within proposed geological waste isolation facilities. However much of the opposition to the Yucca Mountain project and those similar to it, primarily center not around fission products but the plutonium mine concern that placed in the underground, un-reprocessed spent fuel, will eventually become.