Conductivity:

Conductivity of reactor facility water is measured to give an indication of dissolved ionic substances within the coolant. The Conductivity measurements give quantitative rather than qualitative information since it is probable to determine the total conductivity of the ions present, other than not the specific categories of ions present.  Since several ions like as iron (Fe⁺⁺⁺), copper (Cu⁺⁺) chromium (Cr⁺⁺⁺), and aluminum (Al⁺⁺⁺) are susceptible to building oxides and plating out as scale on heat transfer surfaces, reactor coolant conductivity is generally controlled at a level as low as practicable and consistent along with pH.  Through monitoring conductivity levels within the reactor facility systems, an operator is able to cross check the chemistry of these systems, by achieving a higher confidence level within the parameters measured.

Regardless of the operating limits specified for a given reactor facility, operating relationships could be established among pH and conductivity levels of the coolant.  Figure displays a classical relationship of the pH and conductivity of a reactor coolant system using high pH and ammonium hydroxide chemistry control as a function of the ammonia (NH₃) concentration.

Figure: pH and Conductivity as a Function of NH₃ Concentration

Above figure displays the theoretical relationship of pH versus conductivity within a solution containing pure water.  A second curve is added to the graph that described the relationship which exists while nitric acid (HNO₃) is used as a pH control agent (like as might be utilized in facilities along with aluminum components).