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.

2
Main 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, )

3
State 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

4
Experimental

• 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

5
Experimental thermogramms for CsTcO4 and CsI
under identical conditions

• - Starting
• sample mass
• 200 mg
• - Controlled
• evaporation
• surface
• - Nuclearised
• instrument

6
Sublimation/Evaporation rates for CsTcO4 and CsI
as F(T)
7
Evaporation 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