Hydrogen Protects Stored Uranium

This bit is an unexpected gift to the nuclear industry. It means that uranium storage can be designed in such a way that failure modes actually strengthen the protection. The concern with uranium is that it does become wonderfully mobile in normal geological conditions.

In fact it is precisely this behavior that created the extraordinary high grade deposits around the world. Literally ground water migration along the floor of a geological basin will carry free uranium ions until that ion encounters an electromagnetic field generated by a sulphide vein or more commonly a graphite vein where it then precipitates. If it can do that then it is pretty obvious that safe containment is a very special concern.

Now we know that by maintaining inevitable proximity to iron and the natural production of hydrogen to suppress any activity, it becomes much easier to engineer a secure containment. Maybe even the engineers will be able to sleep soundly at night.

Hydrogen Protects Nuclear Fuel In Final Storage

Stockholm, Sweden (SPX) Apr 28, 2009


http://www.nuclearpowerdaily.com/reports/Hydrogen_Protects_Nuclear_Fuel_In_Final_Storage_999.html

Patrik Fors has now created these conditions in the laboratory and examined three different types of spent nuclear fuel. All of the trials showed that the hydrogen protects the fuel from being dissolved in the water, even though the highly radioactive fuels create a corrosive environment in the water as a result of their radiation. The reason for the protective effect is that the hydrogen prevents the uranium from oxidizing and converting to liquid form.


*****

When Sweden's spent nuclear fuel is to be permanently stored, it will be protected by three different barriers. Even if all three barriers are damaged, the nuclear fuel will not dissolve into the groundwater, according to a new doctoral dissertation from Chalmers University of Technology in Sweden.

By Midsummer it will be announced where Sweden's spent nuclear fuel will be permanently stored. Ahead of the decision a debate is underway regarding how safe the method for final storage is, primarily in terms of the three barriers that are intended to keep radioactive material from leaking into the surrounding groundwater.

But according to the new doctoral dissertation, uranium would not be dissolved by the water even if all three barriers were compromised.

"This is a result of what we call the hydrogen effect," says Patrik Fors, who will defend his thesis in nuclear chemistry at Chalmers on Friday. "The hydrogen effect was discovered in 2000. It's a powerful effect that was not factored in when plans for permanent storage began to be forged, and now I have shown that it's even more powerful than was previously thought."

The hydrogen effect is predicated on the existence of large amounts of iron in connection with the nuclear fuel. In the Swedish method for final storage, the first barrier consists of a copper capsule that is reinforced with iron. The second barrier is a buffer of bentonite clay, and the third is 500 meters of granite bedrock. Some other countries have chosen to make the first barrier entirely of iron.

It is known that microorganisms and fissure minerals in the rock will consume all the oxygen in the groundwater. If all three barriers were to be damaged, the iron in the capsule would therefore be anaerobically corroded by the water, producing large amounts of hydrogen. In final storage at a depth of 500 meters, a pressure of at least 5 megapascals of hydrogen would be created.

Patrik Fors has now created these conditions in the laboratory and examined three different types of spent nuclear fuel. All of the trials showed that the hydrogen protects the fuel from being dissolved in the water, even though the highly radioactive fuels create a corrosive environment in the water as a result of their radiation. The reason for the protective effect is that the hydrogen prevents the uranium from oxidizing and converting to liquid form.

Furthermore, the hydrogen makes the oxidized uranium that already exists as a liquid in the water shift to a solid state. The outcome was that the amount of uranium found dissolved in the water, after experiments lasting several years, was lower than the natural levels in Swedish groundwater.

"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 amount of iron in the capsules is so great that it would produce sufficient hydrogen to protect the fuel for tens of thousands of years.