Proton exchange membrane based hydrogen sensor for sodium cleaning application

Sodium is used as coolant in fast reactors. Sodium adhering to the reactor components is required to be removed before commencement of maintenance activities. In water vapour–carbon dioxide process, sodium is removed from the components by reacting it with water vapour carried by gaseous carbon dioxide. Hydrogen is formed during the above process. Since hydrogen forms an explosive mixture with air beyond explosion limit of 4%, monitoring hydrogen in carbon dioxide is required before being let out to the atmosphere. Quantification of hydrogen also gives an estimate on the progress of the cleaning process. A fuel cell based amperometric hydrogen sensor, H2/Pt//Nafion//Pt/O2, has been developed and applied for the purpose. The paper discusses the details of the sensor, its response behavior for hydrogen in carbon dioxide and its application for hydrogen monitoring in a simulated lab scale sodium cleaning experiment. The paper also illustrates the application of the sensor to hydrogen monitoring in mock up studies on sodium cleaning of a major component of Prototype Fast Breeder reactor (PFBR) namely Failed Fuel Location Module (FFLM).