There are a number of special sensors used in sodium — cooled power reactors. These are discussed in Vol. 2, Chap. 17. Most of the sensors are associated with monitor­ing sodium purity, e. g., the “plugging meter” that senses when impurities in the sodium have reached specific concentration levels, the electrochemical oxygen meter that monitors the activity of oxygen in the sodium coolant, the carbon meter that measures the carburizing potential in liquid sodium, etc. These are discussed in Chap. 17, Sec. 17-5.3, rather than in this chapter because of their rather specialized association with sodium-cooled reactors.

4-9.3 Special Sensors for Gas-Cooled Reactors

Gas-cooled reactors also require a number of specialized sensors. Sonic and acoustic thermometry have been noted elsewhere m this chapter. The critical importance of minimizing moisture in the primary gas coolant (analogous to the minimizing of oxygen in the sodium coolant in sodium-cooled reactors) has led to the development of moisture-sensing systems. These are discussed in Vol 2, Chap 18, Sec 18-3 3 In addition to moisture, coolant purity is also required This has led to the development of gas analyzing systems m the high temperature gas-cooled reactors These are also discussed in Sec 18-3 3