Improvement of Real-Time Tritium Monitor for Low-Level Measurement at HANARO

Two real-time tritium monitors are installed at the stack of HANARO, a 30 MW research reactor, to measure the tritium concentrations in the discharged air from the reactor hall and reactor concrete island region. The tritium monitor adopts coincidence and anticoincidence coupling to detect the very low energy beta particles from tritium. Since the tritium level in the air released from the reactor hall is very low during normal operation of HANARO, tritium concentration measurements are easily affected by the noble gas signal contribution and background. Thus, a method to remove the noble gas contribution and the tritium background is established. The noble gas contribution is verified and removed using reliable noble gas measurements by a third detection method. The tritium background is deduced using the bubbling method. The tritium concentration is determined using the newly established method, and it is compared with bubbling data. The two measurement methods produce mutually consistent data. Thus it can be concluded that our evaluation method provides useful data processing for the real-time measurement of extremely low tritium levels.