ECN publication
NVN 5694 intralaboratorium-validatie: haalbaarheidsstudie voor interlaboratorium-validatie
Published by: Publication date:
ECN NUC 1-11-1998
ECN report number: Document type:
ECN-C--98-091 ECN publication
Number of pages: Full text:
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Within the project NORMSTAR 2 a number of Dutch prenormative protocolshave been defined for radioactivity measurements. Some of these protocols, e.g. the Dutch prenormative protocol NVN 5694, titled Methods for radiochemical determination of polonium-210 and lead-210, have not been validated, neither by intralaboratory nor interlaboratory studies. Validation studies are conducted within the framework of the programme 'Normalisatie and Validatie van Milieumethoden 1993-1997' (Standardization and Validation of test methods for environmental parameters) of the Dutch Ministry of Housing, Physical Planning and the Environment (VROM). The aims of this study were (a) a critical evaluation of the protocol, (b) investigation on the feasibility of an interlaboratory study, and (c) the interlaboratory validation of NVN 5694. The evaluation of the protocol resulted in a list of deficiencies varying from missing references to incorrect formulae. From the survey by interview it appeared that for each type of material, there are 4 to 7 laboratories willing to participate in a interlaboratory validation study. This reflects the situation in 1997. Consequently, if 4 or 6 (the minimal number) laboratories are participating and each laboratory analyses 3 subsamples, the uncertainty in the repeatability standard deviation is 49 or 40 %, respectively. If the ratio of reproducibility standard deviation to the repeatability standard deviation is equal to 1 or 2, then the uncertainty in the reproducibility standard deviation increases from 42 to 67 % and from 34 to 52 % for 4 or 6 laboratories, respectively. The intralaboratory validation was established on four different types of materials. Three types of materials (milkpowder condensate and filter) were prepared in the laboratory using the raw material and certified Pb-210 solutions, and one (sediment) was obtained from the IAEA. The ECN-prepared reference materials were used after testing on homogeneity. The pre-normative protocol can be used for different kind of materials with activity concentrations of Pb-210 or Po-210 ranging from 2.10"-2 Bq/g to 150 Bq/g. The ratio of reproducibility standard deviation to the repeatability standard deviation varies from 1.00 to 1.34 for Pb-210 and from 1.01 to 1.08 for Po-210. This shows that the contribution of the operator to the total uncertainty is small. 13 refs.

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