Routine Standardization of Radionuclides in the UK

Standards of radionuclides, whose activity has been measured either directly by a primary method, or by comparison with a primary standard, are available from the NPL and the AERE. Measurements of standards are carried on also at other laboratories such as RCC and AWRE. Some estimate of the number of staff employed and of standards issued will be given. An advisory committee, of those directly interested in this work at the institutions named and one or two others, has promoted the interchange of information and measurements. For routine issues, NPL uses mainly 4 l π β counting in its various forms, linked with coincidence counting, and reference ionization chamber methods. To deal with a wider variety of nuclides, AERE uses gas and scintillation counting for special purposes. The apparatus employed will be described and the internal consistency, and agreement with the results of other laboratories, which has been attained over the past few years, will be discussed, for a number of the more important nuclides. At the original suggestion of the Committee, a combined β-γ reference ionization chamber has been designed and is now commercially available; many of these chambers have been calibrated at NPL, and their performance and consistency will be discussed. (author)