Coolant quantity monitoring device

Purpose: To accurately obtain the quantity of coolant in a pressure vessel of a BWR type reactor. Constitution: Measuring mechanisms provided in a reactor isolation time cooling system, a condenses water supplying system and a core spraying system are used as an inflow quantity measuring mechanism for measuring the total inflow quantity to a reactor pressure vessel, and the measured values are inputted to an arithmetic unit. On the other hand, measuring mechanisms provided in an escape pipe, a drain pipe, and a steam drain pipe are used as an outflow quantity measuring mechanism for measuring the total outflow quantity, and the measured values are inputted as the outflow quantity data to the arithmetic unit. This arithmetic unit calculates the balance between the total inflow quantity and the total outflow quantity, thereby accurately obtaining the quantity of coolant in the pressure vessel. (Seki, T.)