Authors & Affiliations
Blokhin V.A., Borisov V.V., Kamaev A.A., Levin O.E., Stroyev V.A., Trufanov A.A.
A.I. Leypunsky Institute for Physics and Power Engineering, Obninsk, Russia
Borisov V.V. – Deputy Head of Laboratory, A.I. Leypunsky Institute for Physics and Power Engineering.
Kamaev A.A. – Division, ?and. Sci. (Tech.), A.I. Leypunsky Institute for Physics and Power Engineering.
Levin O.E. – Head of Laboratory, A.I. Leypunsky Institute for Physics and Power Engineering.
Stroyev V.A. – Researcher, A.I. Leypunsky Institute for Physics and Power Engineering.
Trufanov A.A. – Deputy Director General-Director of the Safety of NPP, A.I. Leypunsky Institute for Physics and Power Engineering.
For fast neutron reactors of high power with a sodium coolant, continuous monitoring of the oxygen content in sodium is required, starting at a temperature of 300°C and an oxygen concentration in the range of 0.1 to 10 ppm. Continuous oxygen control in sodium with this content can only be provided by oxygen sensors developed on the basis of the EMF method using a solid oxide electrolyte corrosion-resistant in sodium.
In addition, the performance of electrochemical sensors on solid electrolytes depends on the electrophysical properties of the solid electrolyte itself, which is usually checked in the composition of galvanic concentration elements with electrodes, the thermodynamic properties of which are known, well studied and able to simulate the working conditions for oxygen in a controlled environment.
As an electrode measuring electrode, an electrode is chosen which simulates the lower limit of oxygen concentration in the controlled medium, since with decreasing oxygen concentration in the heat carrier, the electronic conductivity of the electrolyte increases, which leads to an increase in the lower temperature of the oxygen sensor's applicability. The lower boundary for the oxygen content in sodium is well modeled by an electrode from Na-Cr-NaCrO2. Chromium sodium is formed as a result of the interaction of sodium with chromium and oxygen contained in sodium.
To check the thermodynamic potential of oxygen deoxidized with chromium, a GCE with a reference electrode made of indium saturated with oxygen and a device was developed. A schematic diagram of the installation is given. The conditions for determining the thermodynamic potential of oxygen in sodium, chromium-depleted, are described. The amount of chromium per gram of sodium in the plant was 0.00216 g. The solubility of chromium in sodium at 500°C is 4.94·103 ppm.
The thermodynamic potential of oxygen in sodium, deoxidized by chromium, is determined by the EMF method using a solid oxide electrolyte based on hafnium stabilized gadolinium oxide in the temperature range from 300°C to 500°C. It is shown that the thermodynamic potential of oxygen in sodium, chromium-depleted is: ΔG(CAL/g-At oxygen)=119000+32,13 T(K). The errors of a single EMF measurement (±80.7 cal/g-at) are given, the error of the coefficients of the equation (±60.7 cal/g-at and ±0.1475 cal/degrees g-at). The obtained data are compared with the literature data.
sodium, chromium, sodium chromite, thermodynamic potential of oxygen, EMF method, solid oxide electrolyte
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