Ever since the first atomic bomb was exploded during World War II’s Manhattan Project, and ever since the first nuclear power plant opened in Obninsk, Russia, radioactive waste has been accumulating. As the number of nuclear power plants and nuclear weapon plants increased, the question of what to do with all that waste has become one of the biggest issues facing science today.
The primary issue is what to do with radioactive waste after the uranium and plutonium have been recovered from spent nuclear fuel using standard reprocessing methods such as Plutonium Uranium Redox Extraction (PUREX).
Up until now, the most viable option for disposal of nuclear waste has been burying it deep underground. Other solutions such as partitioning and transmuting, which involve separating nuclear fuel into minor actinides such as neptunium, americium, and curium, have proven to be costly and cumbersome because of the need to separate isotopes before they can undergo transmutation. But now, a team of researchers at Tokyo Institute of Technology may have come up with a solution to the radioactive waste problem.
The team discovered a method of dramatically reducing the effective half-life of long-lived fission products (LLFPs) such as selenium-79, zirconium-93, technetium-99, palladium-107, iodine-129, and caesium-135. That method involves transmuting these isotopes in fast-spectrum reactors, which don’t need isotope separation like other methods do.
By adding a moderator (slowing-down material) called Yttrium deuteride (YD2), the team found that LLFP transmutation efficiency increased in the radial blanket and shield regions of the reactor. The researchers say this increased effectiveness is due to the moderator’s ability “to soften the neutron spectrum leaking from the core.”
Using this method, the researchers say, the 17,000 tons of LLFPs in Japan could potentially be disposed of by using 10 fast spectrum reactors. This method also has the advantage of contributing to electricity generation and supporting efforts toward nuclear non-proliferation.
Although ultimately, the best solution to the nuclear waste problem is to invest in non-toxic energy sources like solar and wind power, it’s a good thing these researchers came up with a way to decrease the toxicity of radioactive waste and give its by-products a new life—and a much shorter half-life.