Uranium nitride fuels in superheated steam

• Uranium mononitride (UN) pellets of different densities were subjected to a superheatedsteam/argon mixture at atmospheric pressure to evaluate their resistance to hydrolysis. Completedegradation of pure UN pellets was obtained within 1 hour in 0.50 bar steam at 500 °C. Theidentified reaction products were uranium dioxide, ammonia and hydrogen gas, with no detectableamounts of nitrogen oxides formed. However, the reaction could not be carried to completion, andthe presence of uranium sesquinitride and higher uranium oxides or uranium oxynitrides in the solidresidue is indicated. Evolution of elemental nitrogen was seen in connection with very high reactionrates. The porosity of the pellets was identified as the most important factor determining reactionrates at 400 – 425 °C, and it is suggested that in dense pellets, cracking due to internal volumeincrease initiates a transition from slow surface corrosion to pellet disintegration. The implicationsfor the use of nitride fuels in light water reactors are discussed, with some observations concerninghydrolysis as a method for 15N recovery from isotopically enriched spent nitride fuel.

Ämnesord

NATURVETENSKAP  -- Fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences (hsv//eng)

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Energy Technology

Energiteknik

Teknisk materialvetenskap

Materials Science and Engineering

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