Nuclear waste management

Fig.1 Radioactivity over time of each major isotope in spent fuel from a nuclear reactor

Worry about nuclear waste management is one of the barriers to reconsidering nuclear power. How much waste is produced compared to other sources of energy? How will it be contained, and what are the dangers to people and the environment? Like questions on safety, public perception of the dangers of nuclear waste is much worse than historical data shows. The volume of waste per per terawatt-hour is 100,000 times less than coal. Even if we look only at radioactivity released to the environment, watt-for-watt nuclear power is 100 times less than coal.

Much of the worry about nuclear waste centers around the long life of some low-level isotopes in the waste (See Figure 1). There is concern about leakage into the environment decades or even centuries from now. Billion-dollar efforts to bury the waste deep under a mountain have only heightened public fears. Dry-cask storage at the power plants has proven to be a safe but temporary solution. This interim storage has the advantage of being able to recover the "waste" and use it in newer reactors that can use the remaining 97% of available energy.

Transportation of wastes from reactors to storage or reprocessing sites must be done safely. Leakage into groundwater and ocean water near shore is a special concern. New reactor designs must address these concerns, even though they go beyond the design of the reactor itself. Will the waste be solid or liquid? Will it require special casks, or even special vehicles for transportation on public roads? (See Figure 2)

© Photo: Nuclear Fuel Transport Ltd.
Fig.2 Transport of Nuclear Fuel in Japan.

Other worries include the possibility of sabotage or theft of waste material that might be useful in a "dirty bomb". We should evaluate specific plans by considering likely scenarios. Is the storage facility away from any population center and not a target for an airplane crash, a truck bomb, or even a short-range missile? Is there a secure perimeter with intrusion detectors? If there is an intrusion, is cutting through the concrete and steel difficult enough that there will be plenty of time for a response from local law enforcement, or even a nearby military base? (See Figure 3)

© Image: Holtec International
Fig.3 Dry underground storage in the desert, safe but still recoverable.

In evaluating a new reactor design, we must look at the complete fuel cycle, not just the waste from the reactor itself. Are there any problems with the mining, processing, or transportation of the fuel, or with the reprocessing of spent fuel?

Interim Storage

It is important that we make a distinction between spent fuel from nuclear power, and the waste from bomb production, which was often done in a rush with little concern for pollution. Spent fuel rods can be stored safely. Weapons waste poses a much bigger problem due to the large variety and sometimes unexpected characteristics of the waste material. Spent fuel rods contain 97% of the energy in new rods (See Figure 4) and this energy can be used in advanced reactors. Weapons waste has nothing worth saving.

Fig.4 Spent fuel from older reactors should not be treated as waste.

Fig.5 Deep geological disposal is necessary for nuclear weapons waste, a much bigger challenge than spent fuel rods.

Reprocessing

(c) Photo: World Nuclear Association
Fig.6 A well-managed nuclear fuel cycle results in very little high-level waste. This waste may be melted into borosilicate glass and cast into stainless steel canisters for permanent disposal.

• Processing of Used Nuclear Fuel World Nuclear Association
• Recycling used nuclear fuel - Orano la Hague video on the French recycling process
  
  • 4000 employees, reprocessing Spent Nuclear Fuel for France and other countries
  • Spent Nuclear Fuel (SNF): 95% U, 1% Pu, 4% fission products
  • Vitrified waste volume 20% of original SNF volume, melted into stainless steel canisters. (See Figure 6)

The vitrification process is currently being used in France, Japan, Russia, UK, and USA. The capacity of western European vitrification plants is about 2,500 canisters (1000 tonnes) a year, and some have been operating for three decades. So far, about 400,000 tonnes of used fuel has been discharged from commercial power reactors, of which about 30% has been reprocessed.

Permanent Disposal

After recovery of all the valuable isotopes in spent fuel, there will still be a small remainder of high-level waste. This waste can be permanently disposed in deep geological repositories already in use for bomb production waste. See Figure 5. The canister in Figure 6 holds 175 liters of solid glass waste with ___ kg of highly-radioactive fission products. Waste from a typical 1000 MWe Pressurized Water Reactor will fill ___ of these canisters in a full year of operation.

Further Reading

• World Nuclear Association articles on the Nucldear Fuel Cycle including Fuel Recycling and Nuclear Waste Management.