Dealing with radioactive waste is one of the most controversial issues associated with nuclear power. The IFR concept addresss the most difficult problem with nuclear waste --- how to isolate it from human contact until it can decay to a level of minimal biological risk.

Radioactive isotopes resulting from production of nuclear power fall into two categories: fission products and transuranium elements, also known as transuranics, actinides, or TRU. The distinction is important, because the relative biological hazard of the two groups is quite different. Fission products are the result of nuclear power production. Transuranics are the heavier "man-made" elements -- plutonium, americium, neptunium, curium, etc.-- that are created by other nuclear reactions in the fuel.

Fission products consist of literally hundreds of isotopes, many of them radioactive. They represent a major short-term hazard, but after only a few hundred years, pose less risk than the natural uranium ore from which the fuel material was originally extracted. Transuranics consist of relatively few isotopes, but they are radioactive on a geological time scale-- up to several million years.

Many public buildings and cathedrals around the world have lasted for several hundred years, so construction of a safe storage repository for fission products should be highly credible. However, with present U.S. technology, transuranics and fission products remain mixed together, and the goal is to ensure safe storage for 10,000 years or more. Many scientists and engineers are convinced that such long-term-storage is feasible. However, because the entire history of civilized man is less than ten thousand years, many people remain skeptical.

In the IFR concept, plutonium will be recycled with uranium back into the reactor. In the process which separates the unused fuel from most of the fission products, the transuranics stay with the fuel. Transuranics readily fission in the IFR core, so they actually become a useful constituent of the fuel. Present day "light water" reactors (LWRs) operate on a once-through cycle. As transuranium elements build up, plutonium fission produces 40% of the total energy over the life of the fuel. Nevertheless, most of the plutonium and other transuranics are discharged for storage in the spent fuel, representing not only a long-term radiation hazard, but also a potential nuclear proliferation concern. Some plutonium is recycled for LWR use in Europe and Japan, but continuous recycling is not possible because not all the transuranic isotopes can be efficiently fissioned in these reactors

IFRs can be designed to consume transuranics from external sources such as spent LWR fuel or dismantled nuclear weapons, or to maintain an equilibrium between fission and production of transuranium elements. For any of these designs, the nuclear waste leaving the facility would contain just fission products, essentially free of transuranics.

It will be several decades before IFR technology could supplant current-- light water reactor (LWR) --- technology in the United States. In the interim, a large inventory of spent LWR fuel will accumulate. Without introduction of the IFR, thisspent fuel represents a long-term radioactive waste burden. However, with the introduction of the IFR, the remaining uranium and transuranics in the spent LWR fuel, together with discarded uranium-238 from current LWR technology. At some point in the future, the decision could be made to separate the transuranics and uranium from the spent LWR fuel, and use them in the IFR fuel cycle.

Regardless of the ultimate disposition of spent LWR fuel, the IFR offers the potential for making nuclear power a nearly unlimited resource. The benefits of the IFR can be realized without any build up of transuranic waste. When the final IFR is decommissioned, the waste legacy of the era would be accumulated fission products-- few transuranics would remain. Within a few hundred years the biological risk from radioisotopes generated in IFRs would drop below that of uranium ore in 1938, before fission was discovered. Without IFR-type technology, nuclear power will only benefit a few generations of the world's population, while the care and isolation of nuclear waste will continue for eons.

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