Title: STUDY OF THE SUBLIMATION AND VAPORIZATION OF ALKALI METAL PERTECHNETATES, MTcO4 (M = Na,K, Cs)
1 STUDY OF THE SUBLIMATION AND VAPORIZATION OF
ALKALI METAL PERTECHNETATES, MTcO4 (M Na,K,
Cs)
- Institute of Physical Chemistry Russian Academy
of Sciences - German K., Peretroukhin V.
2Main reasons for the accumulation of volatility
data on 99Tc(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) - basis for estimating conditions for high
temperature analytical procedures
(decarbonization, )
3State of knowledge of volatile Tc species
- At lt picogram level - TcO3 (Eichler, Domanov,
1975, JINR Steffen, Bachman, 1978), HTcO4 - At micro and macro level
- Tc2O7, MTcO4 (Boyd, )
- (MTcO4)2, (Kuranov,1986)
- Tc2O5, Gibbson,1993)
- Fusion temperatures
- NaTcO4 - 1063 K
- KTcO4 - 803 K
- CsTcO4 - 863 K
- Considerable information is found on volatility
of Tc during radioactive wastes vitrification - Evaporation rate for NaTcO4 was reported to be
0.37 mgcm-2min-1 at 700 ?? and increased to 3.2
mgcm-2min-1 at 1050 ?? (German, Peretrukhin,
1990) - Tc - Carbonyls (Suglobov)
- Tc - acetate-chloride (German)
- Tc - fluorides
-
4Experimental
- Chemically pure compounds MTcO4 (M Na, K, Cs)
were synthesized in our Laboratory - The high-temperature evaporation/sublimation was
studied by thermogravimetry analyses (TGA) - Instrumentation Q-1500D derivatograph (system
F.Paulik-J.Paulik-L.Erday) - 300 1300 K temperature region
- Dynamic and quasi-isothermal modes were used
5Experimental thermogramms for CsTcO4 and CsI
under identical conditions
- - Starting
- sample mass
- 200 mg
- - Controlled
- evaporation
- surface
- - Nuclearised
- instrument
6Sublimation/Evaporation rates for CsTcO4 and CsI
as F(T)
7Evaporation rate linearization for fused salt
sample of CsI and CsTcO4 in dynamic TGA mode
- pre-fused samples - temperature increase
rate 10 deg/min - sample evaporating
surface 1 cm2 - initial sample mass 200 mg