INTERCOMPARISON OF MEASUREMENT OF TRITIATED-WATER BY INTERNAL PROPORTIONAL GAS COUNTING

An international intercomparison of measurements of tritiated water by means of internal proportional gas counting has been carried out unde r the auspices of EUROMET, a European collaboration in measurement sta ndards. The measurements were made at the Physikalisch-Technische Bund esanstalt (PTB), Braunschweig (Germany), the National Institute for St andards and Technology (NIST), Gaithersburg (USA) and the National Phy sical Laboratory (NPL), Teddington (UK). The current work follows an i ntercomparison reported at ICRM'93 [J.L. Makepeace et al., Nucl. Instr . and Meth. A 339 (1994) 343], between NPL, PTB, NIST and the Laborato ire Primaire de Metrologie des Rayonnements Ionisants (LPRI), Saclay ( France), of measurements of tritium gas contained in a cylinder, in wh ich agreement within the stated uncertainties had been achieved. Sampl es of the same tritiated water were distributed to the participating l aboratories for measurement. The methods used to reduce the water to t ritium gas and its subsequent measurement by internal proportional gas counting are described, together with the results obtained and the ex perimental uncertainties associated with the measurements.