Masaru Yasumoto

Effect of sweep gas chemistry on vaporization of Li4SiO4

Abstract Gas/solid equilibria in the system Li 4 SiO 4 D 2 D 2 O were studied by means of Knudsen effusion mass spectrometry. A Knudsen effusion mass spectrometer was modified to enable studies of reactions of hydrogen and/or water vapor with ceramic breeder materials. A gas inlet system was constructed to allow the introduction of gases into a platinum Knudsen cell, from which the equilibrated gaseous reaction products effuse. From the experimental results, it has been deduced that the equilibrium constants of vaporization reactions differ correspondingly to the nonstoichiometry of lithium orthosilicate.

Thermodynamics of vaporization of cesium molybdate by means of mass spectrometry

Abstract The vaporization behavior of cesium molybdate (Cs2MoO4) has been studied by using the Knudsen effusion mass spectrometry. A combination of a molybdenum outer cell and an alumina inner Knudsen cell was utilized in the Nuclide 12–90 HT high temperature mass spectrometer. The obtained vapor pressure P(Pa) of Cs2MoO4(g) is as follows: logP = −1.21 × 104 / T + 9.80 for temperatures higher than the melting point of Cs2MoO4, 1229.5 K, and, logP = −1.36 × 104T + 11.02 for temperatures lower than 1229.5 K, where T is in K.

Investigation of the vaporization of BaUO3 by means of mass spectrometry

An investigation of the vaporization of BaUO3 has been carried out for the first time by means of Knudsen effusion mass spectrometry in the temperature range of 1770–1920 K. The main vapor species over BaUO3 were BaO(g), Ba(g) and UO2(g) in decreasing order of their pressures. The standard enthalpy of formation of BaUO3 was evaluated by the second law and the third law treatments, in which the estimatedH0(T) − H0(298.15) andgef(T) values were employed on account of the absence of published data. Considering the compounds ofBaMO3 with the same perovskite structure whereM stands for metallic cations with the valence of four, a comparison of their standard enthalpies of formation was made in relation to the ionic radius ofM4+.

Investigation of vaporization thermodynamics of SrUO3 by means of mass spectrometry

Abstract The vaporization properties of SrUO 3 have been studied for the first time by means of Knudsen effusion mass spectrometry over a temperature range of 1534 to 1917 K. The sample used was a mixture of SrUO 3 and 23 wt% UO 2 . The main vapor species over the mixture were Sr(g), UO 2 (g) and SrO(g) in decreasing order of their partial pressures. The standard enthalpy of formation of SrUO 3 was evaluated by using the second law and the third law treatments, in which estimated values of H °( T ) − H °(298.15) and gef( T ) were employed on account of absence of published data. The standard enthalpies of the formation of SrMO 3 with pseudo-cubic perovskite structure, where M stands for metallic cations with the valence of four, were also discussed based on the relationship between the ionic radii of M 4+ of the compounds and their enthalpy values.

Study on the sweep gas chemistry effect on vaporization behavior of Li2TiO3 by means of HT mass spectrometry

Abstract The vapor pressures in the Li 2 TiO 3 D 2 D 2 O system were measured by means of atmosphere controllable high temperature Knudsen effusion mass spectrometry. The effect of D 2 and D 2 O on vaporization behavior was investigated. The enthalpies of the reactions, Li 2 TiO 3 ⇌ 2Li+1/2O 2 +TiO 2 and Li 2 TiO 3 + D 2 O ⇌ 2LiOD + TiO 2 were calculated to be 1000.9 ± 32.4 and 449.6 ± 53.5 kJ/mol, respectively. From the results of this study, the maximum allowable temperature with respect to Li transport through the sweep gas in fusion reactor blanket was estimated.

Sweep gas chemistry effect on lithium transport from ceramic breeder blanket materials

Abstract An ‘atmosphere controllable high temperature mass spectrometer’ was developed in order to investigate the effect of D 2 and/or D 2 O on vaporization behavior of ceramic breeder blanket materials. The measurements were made on Li 4 SiO 4 , LiAlO 2 and Li 2 TiO 3 . The enhancement of Li vaporization and the formation of LiOD caused by D 2 and D 2 O introduction, respectively, were confirmed quantitatively. From the resulting thermodynamic data, an discussion on Li loss from the breeder ceramic materials was made. The maximum allowable temperature with respect to lithium transport through the sweep gas in fusion reactor blanket was estimated.

Vaporization properties of SrUO3 and BaUO3 in atmospheres simulating accident conditions

Effects of various environments on vaporization characteristics of BaUO3 and SrUO3 have been studied by means of the Knudsen effusion mass spectrometry. Three kinds of Knudsen cells were employed for simulating different accident atmospheres over temperature ranges from 1470 to 1920 K. The vapor pressures obtained in a platinum Knudsen cell were used as the standard values, with which those obtained in other conditions were compared. A graphite Knudsen cell was utilized to simulate the graphite environment of high temperature gas-cooled reactors (HTGR). On the other hand, a specially designed Knudsen cell with a gas inlet system attached to its bottom was employed in order to introduce reactive gases such as D2(g) or D2O(g) from the outside of the mass spectrometer into the cell. In this way, the effects of hydrogen or water vapor on the vaporization of fission products barium and strontium were examined.

Sweep gas chemistry effect on vaporization of LiAlO2

The equilibrium vapor pressures in the D2D2OLiAlO2 system were measured by means of an atmosphere-controllable high temperature mass spectrometer in the temperature range 1573–1773 K. Based on the reaction, 5LiAlO2(s) + 2D2O(g) = 4LiOD(g) + LiAl5O8(s), the heat of formation of LiAl5O8 was evaluated to be −4553.9 kJ/mol, which is in good agreement with the data in previous studies based on the reaction, 5LiAlO2(s) = 4Li(g) + O2(g) + LiAl5O8(s). The results of this study enabled estimation of the maximum allowable temperature with respect to lithium transport by the sweep gas in fusion reactor blanket.

Sweep gas chemistry effect on vaporization property of Li2ZrO3

Abstract The equilibrium vapor pressures in the system of Li 2 ZrO 3 –D 2 were measured by means of atmosphere controlled high temperature mass spectrometry. The effect of D 2 on vaporization of lithium containing species was investigated quantitatively. The sum of the partial pressures of lithium containing species was estimated to be approximately 0.002 Pa at 1000 K under the condition of 0.1% hydrogen addition into the helium purge gas. The standard enthalpies of the reactions in this system were calculated from the experimental data, which suggested a possibility of non-stoichiometric composition in the surface region of Li 2 ZrO 3 .

Thermochemical study of vaporization of ceramic breeding materials by Knudsen effusion mass spectrometry

In order to evaluate the applicability of Li2SnO3 as a tritium breeding blanket material of a fusion reactor, a thermodynamic study of the vaporization of solid Li2SnO3 was performed by Knudsen effusion mass spectrometry. Partial vapor pressures of Li(g), O2(g), LiO(g), Li2O(g) and SnO(g) were determined over Li2SnO3. The measured partial pressure of Li(g) over Li2SnO3 is relatively high and ranks between those of Li2SiO3 and Li2TiO3. The Gibbs energy of formation of Li2SnO3 was obtained in the temperature range of 1455 to 1590 K. Computer calculations by use of the SOLGASMIX code proved that Li2SnO3 can show excellent performance as a breeder material with regard to tritium recovery and compatibility with stainless steel.