Studies of zirconium alloy corrosion and hydrogen uptake during irradiation

The in-reactor corrosion and hydrogen pickup of Zircaloy-2 and Zr-2.5Nb pressure tube materials are being studied in two test loop: a light water loop in the NRU research reactor and a new heavy water loop in the Halden reactor. The complimentary Lest programs examine the corrosion behavior of small specimens as a function of fast neutron flux and fluence, temperature, water chemistry, and specimen pre-oxidation. In NRU rests conducted over a range of reducing conditions (20 to 60 cm(3) H-2 . kg(-1)) 568 K, Zr-2.5Nb specimens bearing "thin" prefilm oxides (less than or equal to 6 mu m) experience a reduction in oxidation rate influx. However, samples with thick prefilm oxides exhibit higher rates, suggesting that, like Zircaloy-2, rates, for Zr-2.5Nb may increase as the oxide film continues to thicken. Initial results from the Halden program (5 to 7 cm(3) D-2 . kg(-1) ) show that prefilmed specimens from tubes made of beta-quenched material exhibit lower oxidation and deuterium pickup rates than tubes made from non-beta-quenched materials. Prefilmed tubes made from beta-quenched material also pickup a lower percentage Of the D generated by the corrosion reaction. At high flux levels, prefilmed specimens from tube made of both materials exhibit a narrow range of percentage pickup values (4 ro 5%). irrespective of temperature. A pr preliminary examination of activation energies over the range 523 to 598 K suggests significant differences in the temperature dependencies for oxidation and di deuterium pickup of prefilmed specimens of tubes made from beta and non-beta-quenched Zr-2.5Nb. The differences are correlated with fast flux level.