Environmental Applications Of ³H And ¹⁴C

¹⁴C and ³H are important environmental isotopes because they are incorporated in the air we breathe and in the foodstuffs we eat. Periodic (sometimes continuous) monitoring in the environs of any nuclear based facility is an essential requirement for their safe operation. RCD provides services for air sampling for ³H (Please see Sampling Equipment) and for the testing of foodstuffs, grass, milk, fish, vegetables etc.

Measurements in foodstuffs include:

• Tritium as freewater - water that can be readily extracted from the fresh foodstuff by vacuum distillation.
• Tritium as OBT (Organically Bound Tritium) - extracted from dried material after high-pressure chamber combustion in pure oxygen to from water, followed by vacuum distillation
• Carbon-14 as carbon dioxide following drying and high pressure combustion in pure oxygen. Determination of the ¹⁴C content is then carried out by conversion of the carbon dioxide to benzene and liquid scintillation counting the product.

Please note the tritium OBT measurement and the carbon-14 employ high pressure (bomb) combustion techniques. This process enables quantitative analysis of the carbon )and/or OBT) content of the combusted sample which, with known dry/wet ratios, can be directly linked to the content of the frsh foodstuff (ie Bq/kg wet weight).

In the case of tritium (OBT), please note that the result is obtained as an independent determination (unquenched, distilled water), not by subtraction from a total tritium measurement.