It is necessary to investigate the effect of the denitration with formic acid on the precipitation behaviors of Ru and Tc from a simulated high-level liquid wastes, and the effect of the heat-treatments on the volatility behaviors of them from the sludges. The experiments were carried out using radiotracer techniques. Nitrosylruthenium ion was quantitatively converted into RuNO(OH)
3 by the denitration at the initial molar ratio of (HCOOH) /(CNO
3-) from 1.2 to 1.3, and the precipitation rate decreased drastically at the molar ratio over 1.5. Ferric ion was reduced to Fe
2+ ion by the denitration. Pertechnetate ion was reduced to Tc0
2 by Fe
2+ ion, and the quantitative yield of coprecipitation was achieved at the (HCOOH)/(NO
3-) ratio above 1.8. The volatilities of Ru and Tc from the sludges increased with heating times and temperatures, however, decreased with an increase in the (HCOOH)/[NO
3-] ratios. The denitration lowered the volatilization rate of Ru less than 4% at 1, 000°C for 3 h in an air flow. The volatilization rate of Tc was about 5% at 1, 000°C for 2h under conditions of the denitration of the (HC00H)/(NO
3-) ratio over 1.8 and the heattreatment in an Ar flow.
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