ABSTRACT

Aggregates of acicular RuO₂ occur in high-level waste glass. Large aggregates may settle rapidly in the glass, providing a more efficient electrical path on the melter bottom and interfering with the Joule heating of the glass. To clarify the formation mechanism of aggregates and to develop countermeasures to such formation, chemical reactions between RuO₂ and NaNO₃ with/without borosilicate glass were observed. Sodium ruthenates were formed from a RuO₂–NaNO₃ mixture heated without the glass or on a flat glass. On the flat glass, aggregates of acicular crystals of RuO₂ appeared with a decreasing amount of sodium ruthenates at high temperature. Neither sodium ruthenates nor acicular crystals of RuO₂ were formed from the RuO₂–NaNO₃ mixture well mixed with powdery glass and heated. Results of a series of experiments suggest that acicular crystals of RuO₂ and their aggregates formed through the formation and decomposition of sodium ruthenate when the dissolution of sodium into the glass was slower than its reaction with RuO₂. Promoting the dissolution of sodium into a glass or reducing the amount of sodium in liquid waste is expected to suppress the formation of aggregates and their sedimentation.

摘要

针状RuO ₂聚集体出现在高放废玻璃中。大的聚集体可能会在玻璃中迅速沉淀，从而在熔炉底部提供更有效的电气路径并干扰玻璃的焦耳加热。为了阐明聚集体的形成机制并制定针对这种形成的对策，观察了有/无硼硅玻璃的RuO ₂和NaNO ₃之间的化学反应。钌酸钠是由 RuO ₂ -NaNO ₃混合物在没有玻璃的情况下或在平板玻璃上加热形成的。在平板玻璃上，RuO ₂针状晶体的聚集体在高温下随着钌酸钠的量减少而出现。将 RuO ₂ -NaNO ₃混合物与玻璃粉充分混合并加热，既没有形成钌酸钠，也没有形成RuO _{2 的}针状晶体。一系列实验的结果表明，二氧化钌的针状晶体₂和它们的聚集体通过钌钠的形成和分解时形成的钠溶解到玻璃是慢于它的用RuO反应₂。促进钠溶解到玻璃中或减少液体废物中的钠含量有望抑制聚集体的形成及其沉淀。