The plans were shelved because thorium does not produce plutonium for bombs. At least according to wikipedia the MSR produce 233U which could be used to making

The plans were shelved because thorium does not produce plutonium for bombs. At least according to wikipedia the MSR produce 233U which could be used to making nuclear weapons (see Operation Teapot http://nuclearweaponarchive.org/Usa/Tests/Teapot.html http://nuclearweaponarchive.org/Usa/Tests/Teapot.html)