Nuclear fusion produces waste

Nuclear Fusion - A “Clean” Energy?

Fusion as the energy of the future should be safe and clean - at least that's what fusion researchers and advocates of the new technology emphasize. But is that really the case?

At least as far as the really big safety problems are concerned, this is certainly true: Although a fusion reactor with a radioactive fuel, tritium, is also running, it cannot get out of control for physical reasons. There is no such quick chain reaction to build up. If the cooling of the reactor fails, the fusion reaction comes to a standstill by itself. A worst-case scenario or an accident like the one in Chernobyl would therefore be impossible. Another advantage is the significantly shorter half-life of radioactive fuels: while it takes hundreds or thousands of years for plutonium or uranium to reduce their radiation by half, tritium has a half-life of just 12.3 years.

However, a fusion reactor is not harmless or completely risk-free: The hydrogen isotope tritium is extremely light and can escape through minor leaks and become embedded in metals or other materials. The beta radiation emanating from it can be easily shielded, but if it gets into the body through inhalation or ingestion with food, it can damage living cells. The tritium is incorporated into water molecules and only excreted after an average of 20 to 550 days.

The neutrons produced during the fusion can also indirectly become a source of radioactive radiation: If they hit the walls of the combustion chamber wall, they activate their material and can thus make them radioactive. The same applies to coils, feed and discharge lines and the entire support structure of the reactor. Under the influence of the neutron radiation, long-lived radioactive substances are formed, especially in the metallic components. Since these components would have to be replaced and renewed relatively frequently when the reactor was in operation, contaminated waste is regularly generated.

It is planned to store all radioactive waste temporarily in the reactor building itself for decades. Theoretically, the majority of the tritium could be removed from the waste by reprocessing and thus the radiation intensity could be reduced, but this would require an in-house reprocessing plant. After all, in 90 percent of the waste, the radioactivity would have subsided enough after 50 years that it could be released into the environment without concern. The remaining ten percent would have to be stored in underground repositories for at least 100 years.

Overall, a fusion reactor would produce 16,000 tons of waste over a period of 30 years, and if it were demolished, more than twice that amount would be added. In terms of the amount of waste generated, a fusion reactor does not differ from a nuclear power plant, a study by the European Commission came to this conclusion in 1995.

Even if a fusion reactor were certainly the “lesser evil” in comparison with a nuclear power plant, it cannot do without risks and radioactive waste either. The supposedly “clean” energy has a few stains.

Status: 03/26/2000

March 26, 2000