Axial Variations of Oxide Layer Growth and Hydrogen Uptake of BWR Fuel Claddings under Steam Starvation Conditions Available to Purchase

Steam oxidation tests under steam-starved and non-steam-starved conditions were conducted up to 1,573 K using a prototypic BWR fuel assembly (four fuel pins and fuel channel box) with a length of approximately 750 mm. Significant suppression of oxide layer growth and enhancement of hydrogen uptake were found at the downstream positions under the steam-starved conditions. To understand the results obtained in the tests using the prototypic BWR fuel assembly, three separate-effects tests were conducted to obtain a fundamental understanding of the mechanism of oxygen and hydrogen uptake and its axial variations and evaluation of hydrogen solubility in oxygen-dissolved Zircaloy-2. The fuel channel box was found to contribute to the axial variations of oxide layer growth and hydrogen uptake of the fuel pins by acting as a source of hydrogen and a sink of oxygen. The evaluation of hydrogen uptake and release requires a detailed estimation of steam oxidation with time at each elevation.