Results of HTO analysis from the laboratories are summarized in Table 22. Figure 83 presents a summary of the results for HTO from all participants and for each sample. The nominal value is presented as the red bar with the error of 5% as an uncertainty of the secondary standard. The errors in results as reported by the authors were presented in error bars as 3o. Figure 84 compares the results for each laboratory with the nominal values for HTO concentration in radar plots with a logarithmic scale.

Discussion

• All HTO analytical data are acceptable in terms of consistency and are relatively close to the nominal values, except for the results from China, which show high values in comparison with the nominal ones. In general, the overall uncertainty of analytical results of tracer laboratories matches the requirement of field works as well.

• The results for HTO reported by China are generally higher than the nominal values. This may possibly be due to contamination of samples.

• The inconsistency of the Indonesian results on samples with low concentration could be due to high background from liquid scintillation counting or the luminescence effect.