Intercomparison of measurement of tritiated water by internal proportional gas counting

Project Description

Measurements of the specific activity of samples of tritiated water, from a single batch, will be made at NPL(GB), PTE(DE) and NIST(US). The measurement relies on the total reduction of a sample of tritiated water to produce a mixture of tritium and hydrogen gas. This may be achieved by reacting the water with either zinc or magnesium. The specific activity of the HT/H2 mixture may be measured by internal proportional gas counting und relates directly to the specific activity of the tritiated water. The techniques to be employed at the three laboratories differ in a number of ways including method of reduction of water, method of collection of the gas and gas counting method.

The samples to be measured will be prepared at NPL. Each sample will consist of approximately 1.5 ml of water, sealed in a break-seal ampoule, at a level of activity of approximately 370 kBq.ml-1 (10 µ Ci.ml-1). Each participant will receive 10 ampoules.