Total Gas:

Total gas concentration within the reactor coolant system is another parameter of concern. It is the sum of all gases contained within the coolant system and is made up primarily of nitrogen (N₂), hydrogen (H₂), argon (Ar), and oxygen (O₂). The little amounts of fission gases (Kr and Xe) generally present in the system might also contribute to the total gas concentration; therefore, under normal conditions these are essentially undetectable. Total gas is of concern since high concentrations could output in the configuration of gas pockets in areas which are high points of the system whereas low or stagnant flow conditions exist. Of particular concern in PWR facilities are the erosion and corrosion which might occur on the impellers of the basic coolant pumps.  Since the concentration of gas is raised, the probability of the gas coming out of solution in important amounts in areas of low pressure is also raised.  This low pressure condition exists at the inlet to the basic coolant pump impeller (whereas centrifugal pumps are utilized).  As these gas bubbles are forced back within solution on the high pressure side of the impeller, erosion could occur as an output of the gas bubble impinging on the impeller. Within extreme concentrations of total gas, reduction of pump priming and cavitation can occur along with resultant mechanical pump damage.