Development of continuous measurement method for tritium in water based on CaF₂(Eu) particles and wavelength shift fibers

Abstract This paper proposes a continuous measurement method for tritium in water based on CaF 2 (Eu) particles and wavelength shift fibers, which was used as fluorescence collection passageway. The obtained results indicated that the efficiency of internal fluorescence collection decreased gradually with increasing stacked thickness of particles of 50 μm size. Once the stacked thickness exceeded 4 mm, this decrease in efficiency had a crucial effect on the measurement results, leading to a decrease, instead of an increase, in the count rate. This conclusion was further supported by changes observed in the distributions of the signal amplitude spectrum and time difference of the coincidence signal. The use of the wavelength shift fiber could greatly improve this situation. The continuous measurement result of tritiated water of flow cell, comprising fiber array and particles, indicated that the lower detection limit was 600 Bq/L under 60 min, which was significantly better than 1135 Bq/L under the same measurement min obtained by simply using particle, and had great space for optimization. Moreover, there was a good linear relation between the count rate and tritium concentration. However, the uniformity in the distribution of the liquid flow field during the continuous measurement still required further optimization.