Worldwide Open Proficiency Test: Determination of ... - Nucleus - IAEA

1. INTRODUCTION
A reliable determination of artificial and naturally occurring radionuclides in environmental
samples such as moss-soil is necessary to comply with the radiation protection and
environmental regulations.
Mosses are small, soft plants, they are found mainly in areas of dampness and low light.
Mosses are common in wooded areas and at the edges of streams. They are also found in
cracks between paving stones in damp city streets and in abandoned stone mines. In this
proficiency test, the IAEA-447 reference material prepared from a terrestrial moss-soil, i.e.
the mosses with the adhered eroded soil to the plant, was used as a proficiency test material as
it is considered an excellent radioactivity bio-monitor.
This proficiency test (PT) is one of the series of the world wide proficiency tests organised
every year by the IAEA Terrestrial Environment Laboratory. This series of PTs is designed to
identify analytical problems, to support Member State laboratories to maintain their
accreditation and to provide a forum for discussions regarding the analysis of naturally
occurring radionuclides. The range of sample types available for analysis has been mainly at
environmental levels.
In this PT, the test item set consisted of four samples: one moss-soil (the IAEA-447 reference
material and three tap water samples spiked with gamma emitting radionuclides. The main
task of the participating laboratories was to identify and traceably quantify the activity levels
of radionuclides present in these matrices. The tasks of the IAEA were to prepare and
distribute the samples to the participating laboratories, to collect and interpret analysis results
and to compile a comprehensive report.
The certified massic activity values of all radionuclides used in this PT were traceable to the
International standards of radioactivity.
In this PT, 1200 test items (reference materials) were prepared and distributed to 300
laboratories from 69 countries in November 2009. The deadline for receiving the results from
the participants was set at 15 May 2010.
The participating laboratories were requested to analyse K-40, Co-60, Zn-65, Cs-134, Cs-137,
Tl-208, Pb-210, Pb-214, Bi-214, Ra-226, Ac-228, Th-234, Am-241, Sr-90, Po-210, U-234,
U-238, Pu-238 and Pu-239+240 in the moss-soil samples 01, and Mn-54, Co-57, Co-60, Zn-
65, Cs-134, Cs-137, Ba-133 and Eu-152 in water samples 02, 03 and 04.
The participants were informed that not all radionuclides were present in the samples and they
had to report on those radionuclides which could be measured with reliably. The analytical
results of the participating laboratories were compared with the reference values assigned to
the reference materials, and a rating system was applied.
The laboratories which responded to this proficiency test and contributed their efforts to the
present work are highly appreciated and acknowledged.
The summary evaluation of this proficiency test demonstrated that 66% of the overall reported
analytical results resulted in acceptable performance and fulfilled the evaluation criteria
applied in this PT.
Final Darft, page 3