A sodium leak detection system for a nuclear reactor vessel includes a recirculation loop having an inlet and an outlet in communication with the annular space between the nuclear reactor vessel and the guard vessel. The recirculation loop and the annulus are filled with an inert gas, such as argon. The inert gas is doped with a known trace quantity of oxygen, typically in the single-digit ppm range up to about 1%. A recirculator forces the inert gas and oxygen to mix and flow throughout the annulus. The recirculation loop further includes a trace oxygen sensor that determines the concentration of oxygen in the inert gas. Because sodium reacts with oxygen, the trace oxygen sensor is monitored for a reduction in the oxygen level, which indicates a sodium leak into the annulus.

A system and method for detecting leaks in nuclear fuel pool assemblies utilize ultrasonic technology to provide safety and integrity. The system includes an inner tube with cobalt slugs, surrounded by an outer tube, both submerged in water. Magnets align the slugs, while ultrasonic transducers transmit and receive waves to detect water presence. A pulse generator excites the transducers, and a control circuit analyzes signal changes to identify leaks. The system operates at frequencies between 50 kHz and 500 kHz, with pulse amplitudes from 50 to 500 volts. A spectrum analyzer enhances detection accuracy by evaluating power distribution across frequencies. The method involves aligning slugs, transmitting waves, and analyzing amplitude changes to confirm water ingress, optimizing detection through strategic transducer positioning and signal analysis.