Creatures with backbones have ovaries.
Reactor-grade plutonium is found in spent nuclear fuel that a nuclear reactor has irradiated -LRB- burnup / burnt up -RRB- for years before removal from the reactor , in contrast to the low burnup of weeks or months that is commonly required to produce weapons-grade plutonium , with the high time in the reactor -LRB- high burnup -RRB- of reactor-grade plutonium leading to transmutation of much of the fissile , relatively long half-life isotope 239Pu into a number of other isotopes of plutonium that are less fissile or more radioactive .. spent nuclear fuel. spent nuclear fuel. nuclear reactor. nuclear reactor. burnup. burnup. weapons-grade plutonium. weapons-grade plutonium. transmutation. nuclear transmutation. fissile. fissile. half-life. half-life. isotopes of plutonium. isotopes of plutonium. Thermal-neutron reactors -LRB- today 's nuclear power stations -RRB- can reuse reactor-grade plutonium only to a limited degree as MOX fuel , and only for a second cycle ; fast-neutron reactors , of which there is less than a handful operating today , can use reactor-grade plutonium fuel as a means to reduce the transuranium content of spent nuclear fuel / nuclear waste .. spent nuclear fuel. spent nuclear fuel. MOX fuel. MOX fuel. transuranium. transuranium