The regular monitoring of air and water samples in and around civil nuclear sites (both active and during the process of decommissioning) and waste repositories is of key importance, both in terms of ensuring that any possible contamination resulting from leaks or spills is detected in a timely fashion and to satisfy the regulatory and environmental demands of government bodies and regulators. Currently, the periodic manual sampling, analysis and reporting process is resource heavy in terms of both the cost and time (sometime weeks) required to obtain, analyse and collate the data arising from measurements of manually acquired samples.

In order to improve monitoring schemes at these sites and move towards a supplemental ‘on-line’ measurement approach, LabLogic Systems have been engaged with the design, development  and evaluation of an innovative radioactivity monitoring system, which was developed in conjunction with the US EPA originally and is known as ‘Wilma’. The system combines a low-level, liquid scintillation-based radioactivity detector and an automated fluid handling system that enables small samples (ml volumes) to be collected from a sampling or supply point and mixed with scintillation cocktail. The mixed sample is analysed in a measurement chamber, where the radioactive count rate of the water sample is obtained, along with an emission spectrum, to determine the elemental origin of any possible contamination. Following automated flushing and washing cycles, the complete measurement cycle can then be repeated to give up to four analyses per hour, over periods in excess of 30 days. If the count rate for a particular sample exceeds a pre-determined threshold limit, an alarm is raised by the system that results in an e-mail being sent to an operative who can then investigate the issue further. The potentially contaminated sample is diverted to a separate container automatically, which can be removed for further analysis.

The first MetroDecom project saw an extension to the Wilma development programme through the integration of the fluid handling and LSC modules with an automated air sampler and bubbler system for ³H and ¹⁴C analysis in air samples to create a portable air monitoring station (Figure 1). The development of the system in MetroDecomII will entail two main strands: characterisation and calibration testing using a gas calibration rig at the National Physical Laboratory in the United Kingdom and field-based evaluation studies at waste repository sites in the UK and Europe.