IN-SITU IRRADIATION ACCELERATED OXIDATION OF ZIRCALOY-4 UNDER PROTON OR ELECTRON IRRADIATION IN PWR PRIMARY WATER

摘要

Corrosion experiments on Zircaloy-4 were conducted in-situ in simulated PWR primary water (320°C water with 3 wt. ppm H_2 without Li and B addition) during irradiation with 3.2 MeV protons or with 1.5 MeV electrons to isolate the effect of displacement damage. The Zircaloy-4 foil acted as a "window" to allow protons/electrons to fully penetrate and deposit their energy in water to induce radiolysis. The area of the samples exposed to the proton beam experienced both displacement damage and radiolysis, while the sample exposed to electron beam was only affected by radiolyzed water. The aim of the study is to characterize the effect of radiation on the kinetics and character of oxidation caused by accelerated waterside corrosion under irradiation. Samples irradiated with protons for total displacement damage of 0.14 dpa (damage rate at 4.4× 10~(-7) dpa/s in metal, and 400 kGy/s in the water) at an exposure time of 24 h in water was compared with electron-irradiated samples (~400 kGy/s in water) in the same condition, and with unirradiated corrosion samples. Results show that the sample area exposed to proton irradiation had an oxidation rate about 10 times that of the unirradiated area, whereas electron irradiated sample had no apparent enhanced corrosion area. Oxide morphology and phase structure were investigated using TEM and Raman spectroscopy. The unirradiated oxide consisted mainly of larger columnar monoclinic ZrO_2 grains, while the proton irradiated oxide exhibited a smaller equiaxed monoclinic ZrO_2 grain structure. The electron irradiated oxide maintains its columnar monoclinic ZrO_2 grain structure.