Development of a real-time tritium-in-water monitor

TL;DR

This paper presents the development of a modular, real-time tritium-in-water monitor capable of detecting activity levels at the EU regulatory limit, suitable for environmental surveillance and nuclear plant pre-alert systems.

Contribution

It introduces a novel modular detector system designed for real-time tritium monitoring in water, achieving a detection sensitivity compatible with regulatory standards.

Findings

Achieved a minimum detectable activity of 3.6 kBq/L for a single module.

Successfully installed and characterized a detector module at a nuclear power plant site.

Demonstrated the system's potential for real-time environmental surveillance and pre-alert applications.

Abstract

In this paper, we report the development and performance of a detector module envisaging a tritium-in-water real-time activity monitor. The monitor is based on modular detection units whose number can be chosen according to the required sensitivity. The full system is being designed to achieve a \emph{Minimum Detectable Activity} (\emph{MDA}) of 100\,Bq/L of tritium-in-water activity which is the limit established by the E.U. Council Directive 2013/51/Euratom for water intended for human consumption. The same system can be used as a real-time pre-alert system for nuclear power plant regarding tritium-in water environmental surveillance. The first detector module was characterized, commissioned and installed immediately after the discharge channel of the Arrocampo dam (Almaraz nuclear power plant, Spain) on the Tagus river. Due to the high sensitivity of the single detection modules, the system requires radioactive background mitigation techniques through the use of active and passive shielding. We have extrapolated a \emph{MDA} of 3.6\,kBq/L for a single module being this value limited by the cosmic background. The obtained value for a single module is already compatible with a real-time environmental surveillance and pre-alert system. Further optimization of the single-module sensitivity will imply the reduction of the number of modules and the cost of the detector system.