An alternative approach to tritium-in-water monitoring

Abstract

A paradigm shift in the approach to tritium-in-water monitoring is considered and its viability demonstrated through a series of proof-of-principle experiments. The fundamental difference in the proposed detection system consists of changing the state of the tritiated water from the liquid phase to the gas phase and subsequently using any one of a variety of detection methods to detect tritium in the water vapour. Proof-of-principle experiments using an un-optimized heated ionization chamber illustrate the viability of the proposed method. Operation of the experiment as a continuous in-line detection system shows a detection limit of ∼20 μCi/l, a detection time constant of 10 s, and simplicity and effectiveness of the overall system. It is projected that an optimized heated ionization chamber system using state-of-the-art current measuring circuitry, could yield a detection limit of ∼0.2 μCi/l. Furthermore, application of a more sensitive detection system (for example, the gas electron multiplier) is expected to result in additional gain in sensitivity. The advantages of the proposed tritium-in-water monitoring system are: high sensitivity with a detection limit beginning to approach current day batch liquid scintillation detection systems; a truly continuous, on-line tritium-in-water monitor with response time of less than tens of seconds; a detection system potentially applicable for multiple stream monitoring; a system that does not generate any waste; and, a system that overcomes the fouling issues associated with current day on-line LSC systems.