STUDY OF THE SUBLIMATION AND VAPORIZATION OF ALKALI METAL PERTECHNETATES, MTcO 4 (M = Na,K, Cs) Institute of Physical Chemistry Russian Academy of Sciences German K., Peretroukhin V.

Main reasons for the accumulation of volatility data on 99 Tc(VII) compounds ¶ understanding of Tc behavior in the procedures of radioactive wastes vitrification · basis for estimating of possible environmental contamination during accidental nuclear reactors. ¸ basis for estimating conditions of high - temperature technology procedures (conversion of white inclusions, reprocessing in molten salts) ¹ basis for estimating conditions for high temperature analytical procedures (decarbonization, …)

State of knowledge of volatile Tc species ¶ At < picogram level - TcO 3 (Eichler, Domanov, 1975, JINR Steffen, Bachman, 1978), HTcO 4 · At micro and macro level Tc 2 O 7, MTcO 4 (Boyd, …) (MTcO 4 ) 2, (Kuranov,1986) Tc 2 O 5, Gibbson,1993) ¸ Fusion temperatures l NaTcO K l KTcO K l CsTcO K ¹ Considerable information is found on volatility of Tc during radioactive wastes vitrification º Evaporation rate for NaTcO 4 was reported to be 0.37 mg * cm -2 * min -1 at 700 о С and increased to 3.2 mg * cm -2 * min -1 at 1050 о С (German, Peretrukhin, 1990) » Tc - Carbonyls (Suglobov) ¼ Tc - acetate-chloride (German) ¼ Tc - fluorides

Experimental l Chemically pure compounds MTcO 4 (M= Na, K, Cs) were synthesized in our Laboratory l The high-temperature evaporation/sublimation was studied by thermogravimetry analyses (TGA) l Instrumentation : Q-1500D derivatograph (system F.Paulik-J.Paulik-L.Erday) l 300 – 1300 K temperature region l Dynamic and quasi-isothermal modes were used

Experimental thermogramms for CsTcO4 and CsI under identical conditions - Starting sample mass 200 mg - Controlled evaporation surface - Nuclearised instrument

Sublimation/Evaporation rates for CsTcO4 and CsI as F(T)

Evaporation rate linearization for fused salt sample of CsI and CsTcO 4 in dynamic TGA mode - pre-fused samples - temperature increase rate 10 deg/min - sample evaporating surface 1 cm 2 - initial sample mass 200 mg