Corrosion Tests of Zircaloy Hull Waste to Confirm Applicability of Corrosion Model and to Evaluate Influence Factors on
- PDF / 288,359 Bytes
- 8 Pages / 432 x 648 pts Page_size
- 76 Downloads / 151 Views
Corrosion Tests of Zircaloy Hull Waste to Confirm Applicability of Corrosion Model and to Evaluate Influence Factors on Corrosion Rate under Geological Disposal Conditions Osamu Kato1, Hiromi Tanabe2, Tomofumi Sakuragi2, Tsutomu Nishimura1, and Tsuyoshi Tateishi3 1 Kobe Steel, LTD., JAPAN 2 Radioactive Waste Management Funding and Research Center, JAPAN 3 Kobelco Research Institute Inc., JAPAN ABSTRACT Corrosion behavior is a key issue in the assessment of disposal performance for activated waste such as spent fuel assemblies (i.e., hulls and end-pieces) because corrosion is expected to initiate radionuclide (e.g., C-14) leaching from such waste. Because the anticipated corrosion rate is extremely low, understanding and modeling Zircaloy (Zry) corrosion behavior under geological disposal conditions is important in predicting very long-term corrosion. Corrosion models applicable in the higher temperature ranges of nuclear reactors have been proposed based on considerable testing in the 523633 K temperature range. In this study, corrosion tests were carried out to confirm the applicability of such existing models to the low temperature range of geological disposal, and to examine the influence of material, environmental, and other factors on corrosion rates under geological disposal conditions. A characterization analysis of the generated oxide film was also performed. To confirm applicability, the corrosion rate of Zry-4 in pure water with a temperature change from 303 K to 433 K was obtained using a hydrogen measuring technique, giving a corrosion rate for 180 days of 8 × 10-3 μm/y at 303 K. To investigate the influence of various factors, corrosion tests were carried out. The corrosion rates for Zry-2 and Zry-4 were almost same, and increased with a temperature increase from 303 K to 353 K. The influence of pH (12.5) compared with pure water was about 1.4 at 180 days at 303 K. INTRODUCTION The development of a corrosion model to evaluate long-term Zry corrosion under disposal conditions has been discussed in [1], which proposed a corrosion model using corrosion correlations obtained in the higher temperature range of 523 to 633 K. In this study, to confirm the applicability of high-temperature corrosion models to the lower temperature range of geological disposal, and to examine the influence of various factors on corrosion rates, corrosion tests were carried out to evaluate the following issues: 1) Applicability of high-temperature corrosion equations to low-temperature corrosion a) Zry corrosion rate in pure water and changes over time in lower temperature range b) Influence of differences in corrosion rate measurement methods (hydrogen measurement technique at low temperatures, weight gain measurement technique at high temperatures) c) Influence of annealing condition differences in actual Zry tube and test specimen d) Influence of composition differences in actual Zry tube and test specimen
195
e) Properties of the oxide film forming at low temperatures 2) Key parameters possibly affecting corrosion ra
Data Loading...