Intercomparison of Nordic therapy level exposure secondary standards for 60Co gamma radiation.

An intercomparison of therapy level exposure secondary standards from the Nordic countries was made at 60Co gamma radiation at the secondary standard dosimetry laboratory in Helsinki . One standard seemed to be in error by about one per cent and another was found to be unreliable. From the analysis it was concluded that inter-comparisons of secondary standards can be made with an overall uncertainty of about 0.2 per cent. This uncertainty is of the same size as the difference between primary standards, which may therefore play a role in the evaluation of differences between secondary exposure standards.