Canadian inter-laboratory organically bound tritium (OBT) analysis exercise.

Area of Science:

• Nuclear Science and Engineering
• Environmental Monitoring
• Analytical Chemistry

Background:

• Tritium emissions from CANDU reactors are a significant safety concern.
• Standardized methods for measuring organically bound tritium (OBT) in environmental samples are lacking.
• The Fukushima accident highlighted the need for data-driven risk assessments.

Purpose of the Study:

• To evaluate current OBT analysis methods used by CANDU Owners Group (COG) members.
• To assess the variability and uncertainty in OBT measurements in environmental samples.
• To identify areas for improvement in OBT analysis methodology.

Main Methods:

• An inter-laboratory comparison study was conducted.
• Three dried environmental samples (fish, Swiss chard, potato) were analyzed for OBT.
• Standard OBT analysis techniques including combustion, distillation, and counting were employed.

Main Results:

• Variations in measured OBT activity concentrations between laboratories were less than 20%.
• Total uncertainty in OBT measurements ranged from 11% to 17%.
• Current OBT analysis methods for combustion, distillation, and counting are generally acceptable for dried samples.

Conclusions:

• Existing OBT analysis methods are largely suitable for dried environmental samples.
• A complete, consensus OBT analysis methodology is required, encompassing all steps from sample preparation to counting.
• Further studies with low-level tritium samples are recommended to fully validate current methods.