eo standards are included in each batch of samples sent through our own facility and other laboratories. other laboratories. Our We also cross count several of the samples sent to quality-control program requires that blind duplicates be within 10% of each other and that the standards be within 10% of the Known value. If such is not the case, the problem must be ascertained and reanalysis completed if necessary; reanalysis has only rarely been necessary. Most of the wet chemistry analyses for 905r, 239+240py, and 24am are done by outside contractor laboratories. To assure analytical reliability of the data produced by the outside laboratories, we have established three criteria governing the accountability of the results. 1. errors. The . first criterion places limits of acceptability on counting Because radioactive decay is a statistical process, sufficient counts must be collected to provide a level of confidence that the number reported is a true measure of the radioactivity of the sample. Until this criterion is met it is difficult, if not impossible, to evaluate the data for the remaining two criteria. Consequently, we have established a set of acceptable counting errors (Table 1}. The requirements are scaled to the total radioactivity of the sample, which is the product of the amount of sample available and its Specific activity (activity per unit weight of sample). Compliance can be checked easily by the individual analyst because it is based on information available to him: received. the measured specific activity and weight of the sample This criterion was developed to estimate the amount of sample required by any competent laboratory to measure worldwide fallout. sufficient size with higher activity are thus well detection of the contracting laboratories. Samples of above the limits of As a result, the data that are reported are not machine limits, which would provide only upper limits to the radionuclide concentrations in the overestimate of of the amount samples. radioactivity Such data would cause an actually present in the environment when used as real values. 2. ‘The second criterion requires that the laboratories reproduce their resuits on replicate analyses. A set of blind duplicate samples is included With each group of roughly 100 samples (called DCD for the accompanying Delivery Control Document) and results of the pair of analyses are considered acceptable if they vary by less than twice the measurement accuracy required in Table 1. JOC03 14 Satisfactory performance on duplicates requires acceptability on