Knudsen Effusion Mass Spectrometry: Technique for Obtaining Useful Thermodynamic Information and for Studying Interesting Vaporization Chemistry

Knudsen effusion mass spectrometry (KEMS) is a very powerful technique for studying the vaporization thermodynamics of inorganic systems at high temperatures. Although primarily one examines the vapor phase, information about condensed phases are also obtained through careful measurements and analysis of the results in accordance with the phase rule. In this paper, we have shown the capability of KEMS to yield information of practical importance and fundamental interest essentially by drawing examples from the vaporization studies on some systems of tellurium, conducted in our laboratory for over two decades. The KEMS studies on M-Te (M = Fe, Cr, Ni, Mo, and Mn, the major components of stainless steel) and Mn-Te-O systems provided the pertinent information as to under what conditions the fission product Te can cause the chemical attack of 316 stainless steel cladding material used in fast breeder nuclear reactors. The study of Mn-Te and Mn-Te-O systems also reveal the effects of condensed phase transitions on the vaporization behavior. Results of such studies are discussed in detail so that KEMS studies of this type will be undertaken more often in the future.