All wastes are distinguished by their harmful effects: radioactivity in the case of radioactive waste. An advantage of this type of waste is that the harmful effects diminish in time. Pending this radioactive decay, the materials must be contained to avoid human exposure to radiation, which is not difficult; assurance mlust also be provided, however, that the containment is effective for very long durations, consistent with the half-lives of the radionuclides involved.