Simulation results on a real-time in water tritium monitor

The low energy beta emission resulting from the tritium decay is a concern from the health and governmental entities in order to keep the As Low As Reasonably Achievable (ALARA) principle. Several legislation and regulation directives have been published defining the maximum concentration in water for human consumption, for example, 100 Bq/L by European directive 2013/51/Euratom and 740 Bq/L by the U.S. Environmental Protection Agency. The challenge of the tritium decay detection is due to its weak emission requiring high sensitive devices or the most used technique, laboratory analysis using Liquid Scintillation Counting, which can take up to 4 days to achieve the low level sensitivity required by the legislation. In this work we present the simulation studies and ideas for an in-water Tritium real-time monitor based on optical scintillation fibbers. Conservative calculations allows to preview a 100 Bq/L sensitivity with 40 Bq/L of activity resolution by using a modular detector composed by 5 detection "cells" containing around 350 fibers each but passive/active shielding against natural/cosmic background as also a water purifying system is mandatory to reach such sensitivity.