Although they provide us with clean electricity, nuclear power plants are often criticized, among others, for their residues after the primary radioactive material is spent. Normally, they are buried in depleted uranium mines, and thus their impact is minimized, but there are lots of situations when things could get dangerous as the radioactive material could infiltrate deep inside the earth, and pollute the underground springs. Chances for that to happen are minimal, but it’s imperative that maximum precautions are to be taken.
For example, Sweden’s standard depleted nuclear storage will be protected by three methods. A doctoral dissertation from Chalmers University of Technology in Sweden says that even if all three of them would be damaged, the nuclear residues would not dissolve into the groundwater.
The protection system relies on the “hydrogen effect“, discovered in 2000. Since then, it has not been used by standard radioactive storage plans, but now Patrik Fors, the creator of the dissertation, says “now I have shown that it’s even more powerful than was previously thought.”
The hydrogen effect relies on the existence of large quantities of iron connected with the nuclear residue. The first barrier consists of a copper capsule reinforced with iron. The second barrier is made of bentonite clay, and the third layer is made of 500 meters of granite. Microorganisms and fissure minerals in the rock will consume all the oxygen in the groundwater.
In the unlikely case that all three barriers would be damaged, the iron capsule will be anaerobically corroded by water, producing hydrogen in large quantities and at high pressures – it would reach 5 megapascals (50 bar), at 500 meters below the surface. For a comparison, the pressure in your car’s tires is of about 2.5 bar.
That hydrogen will protect the fuel from being dissolved into water, even though the radioactive material creates a corrosive environment in the water as a result of their radiation. Hydrogen keeps the uranium from oxidizing and converting to liquid form. In fact, tests have shown that the hydrogen makes the already existing uranium in the water in liquid form turn into solid, cleaning the water, which becomes less radioactive than natural levels present in the groundwaters of Sweden.
“The hydrogen effect will prevent the dissolution of nuclear fuel until the fuel’s radioactivity is so low that it need no longer be considered a hazard,” says Patrik Fors. The large quantities of iron in the capsules would produce enough hydrogen to protect the radioactive fuel for tens of thousands of years, making it harmless.
Let’s just hope our followers won’t lose the trace of the spots that the uranium has been buried, and future civilizations will try to dig the place. Let’s hope they’ll evolve differently than we did. Except that, Sweden has nice blonde girls, it would be a pity to make them (more) radioactive! 🙂