Vaporization properties of Cs2U4O12 in LWR severe accident simulating conditions

Vaporization behaviors of Cs2U4O12 were studied by using the Knudsen effusi on mass spectrometric method at temperatures from 1273 to 1573 K. To clarif y vaporization properties of Cs2U4O12 in case of severe accident conditions of light water reactors, partial pressure measurements were made in D2O/D- 2 mixtures. The D2O/D-2 environments were established in the Knudsen cell b y introducing D-2(g) or D-2(g) + O-2(g) gas into the cell through a fine pl atinum tube attached to the bottom of the cell. Cesium vapor Cs(g) was foun d as the dominant vapor species over the compound either in vacuum or in th e simulated atmospheres. In this study, the average temperature applied was 1423 K, the pressure of Cs(g) over the specimen in vacuum was 1.97 Pa whil e the oxygen potential measured was - 148.2 kJ/mol. The pressure of Cs(g) i ncreased moderately to 2.26 Pa after the introduction of the D-2(g), and it decreased slightly to 1.56 Pa with the admission of D-2(g)+O-2(g). (C) 199 9 Elsevier Science Inc. All rights reserved.