What kind of toxic wastes are produced by nuclear energy?

Nuclear energy produces wastes in the form of spent nuclear fuels, this is normally a mixture of radioactive isotopes and heavy metals, both of which are toxic and pose a great danger to the environment. Additionally, irradiated materials surrounding the reactor which become radioactive from exposure to the radiation produced by the reactor and which should be disposed off at the end of the life of the reactor and processes involved. Also the breeder reactors convert unusable radioactive isotopes into fissionable isotopes, thus allowing more of the fuel to be used and reducing amount of fuel rod waste. 

Answer is to avoid experimental error

Only one reactant yields 2 or more products. meaning you will only have 1 product and it will break down into 2 or more products. eg. h2o -> h2 + o2