Contamination of helium cover gas system with air

In this report helium cover gas system for different period for the Karachi Nuclear power Plant has been given. The pressurization of the dump space of the reactor, helium gas system is incorporated with the moderator to support heavy water in the calandria at the required level. The heavy water gets decomposed to free deuterium and oxygen under irradiation, these gases will tend to collect in the stagnant parts of the system. For keeping helium system free from contamination, it is necessary to make-up the losses of system by adding fresh helium through helium injection station and the oxygen is consumed in the process of corrosion formation of metal components. 7 figs. (A.B.)