Oxidation rate of intentionally punctured dummy fuel element. Study on the behavior of punctured fuel element for Calder Hall type reactor, (2)

Following the previous report on the oxidation behavior of intentionally punctured dummy fuel element, this paper presents the oxidation rate of the dummy, uranium rod clad in the punctured Magnox, by carbon dioxide, air and their equi-volume mixture at 450° and 550℃. Effects, on the oxidation rate, of the presence of water vapor in the oxidizing atmospheres, of the pinhole diameter of the cladding and of chemical additives in the uranium are also presented. Weight gains by carbon dioxide oxidation were 100 mg/day and 7 mg/day at 550° and 450℃ respectively for a specimen with a pinhole of 1.0 or 0.5 mm dia., and 5 w/o of water vapor increased the weight gains remarkably. Heating the specimen in carbon dioxide at 550℃ caused only a slight swelling within a day. Whereas weight gain by air oxidation was approximately 1,000 mg at 550℃ for a specimen with a pinhole of 1.0 mm dia. and effect of the pinhole diameter was not negligible at the beginning of the oxidation. Log-log plot of weight gain as a function of oxidation time was a straight line with one break point which was not observed in the case of carbon dioxide oxidation. (author)