HYDROGEN CONCENTRATION MEASUREMENT TECHNIQUE IN GASES CONTAINING OXYGEN BY PROTON CONDUCTIVE SOLID ELECTROLYTE

摘要

Gas measurement techniques of solid electrolyte type have an excellent environment resistance in high temperature and high pressure, and are utilized in various fields, such as the oxygen sensor for automobile exhaust gases. Particularly, the proton conductive solid electrolyte type hydrogen sensor system could have the excellent accident tolerant capability to measure hydrogen concentration under harsh environmental conditions such as severe accident (SA) in a pressurized water reactor (PWR) plant as well as a boiling water reactor (BWR) plant. The principle of a hydrogen concentration cell has been applied to this hydrogen sensor system. However, accurate hydrogen concentration measurement in oxygen coexistence atmosphere is difficult, since the hydrogen oxidation reaction makes a mixed potential on the platinum sensing electrode. In order to solve this problem, the materials of the sensing electrode have been improved by adding gold to the platinum alloy. This is done due to the binding energy of gold to oxygen being relatively weak (as compared to platinum). Furthermore, we have modified the sensing electrode surface to suppress oxygen adsorption, by adding a layer of siloxane. As a result, the modified platinum alloy electrode detected the value close to theoretical potential, even if under oxygen coexistence.