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Title:
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NVN 5694 intralaboratorium-validatie: haalbaarheidsstudie voor interlaboratorium-validatie
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Author(s):
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Published by:
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Publication date:
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ECN
NUC
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1-11-1998
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ECN report number:
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Document type:
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ECN-C--98-091
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ECN publication
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Number of pages:
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Full text:
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100
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Download PDF
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Abstract:
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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