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Precautions for Hydrogen in a Radioactive Tank

The accumulation of radioactive waste is the major drawback of nuclear energy. Hydrogen gas generates during the nuclear process, and is kept in radioactive storage tanks under a regulated pressure. The gas is associated with causing corrosive damage to tanks, particularly those made from low carbon steel. This is a major concern considering the risk of radioactive waste leakage. Thus precaution is needed when dealing with the hydrogen by-product.

  1. Hydrogen Formation

    • The hydrogen produced during nuclear energy generation is collected from the chemical and volume control system tank and the air ejector exhaust. Hydrogen is also produced as a by-product of the decomposition of organic chemical ethlenediaminetetraacetic acid, which is a complexing agent added to radioactive waste in an attempt to reduce the volume. This occurs as radiation emitted from stored waste bombard the chemical, producing free radical hydrogen atoms in the process.

    Corrosion Process

    • Older radioactive tanks were manufactured using carbon steel, which is susceptible to corrosion by hydrogen. Under stressful conditions, hydrogen free radicals degrade the carbon steel alloy, causing it to become brittle. This is exacerbated by the radiation emitted, which not only induces free radical generation, but increases its ability to permeate the carbon steel and further contribute to cracking. Permeability is also affected by the gamma ray and beta particle field emitted by waste fission products.

    Cause for Concern

    • Since 1944, the U.S. Department of Energy had 165 single-shelled underground radioactive tanks made from low carbon steel. By 1993, 75 of tanks were identified with corrosive cracks and drained of their radioactive waste to prevent further leaking. There is concern that the same fate will befall the remaining tanks. Also, as heaps of hydrogen gas builds up in tanks currently stored, its potential overflow increases the risk of explosions, which would release radioactive waste into the environment.

    Precautionary Measures

    • In 1993, the U.S. Department of Energy commissioned the construction of a large pump in attempts to lower hydrogen levels. Yet in time it was observed that hydrogen was still accumulating despite no waste additions to the tank. The use of hydrogen recombiners was adopted to achieve the same effect. Hydrogen recombiners operate by initiating reactions between hydrogen and oxygen to produce water. This is done using a platinum catalyst and under temperatures between 800 and 1000 degrees Fahrenheit.

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