Contents lists available at ScienceDirect Applied Radiation and Isotopes journal homepage: www.elsevier.com/locate/apradiso A review of the TAEA proficiency test on natural and anthropogenic radionuclides activities in black tea E. Yeltepe a, ⁎ , N.K. Şahin a , N. Aslan a , M. Hult b , G. Özçayan a , H. Wershofen c , Ü. Yücel a a Turkish Atomic Energy Authority, Sarayköy Nuclear Research and Training Center (TAEA-SNRTC), Atom C, 06983 Ankara, Turkey b European Commission, Joint Research Centre, Directorate for nuclear safety and security, JRC-Geel, Retieseweg 111, B-2440 Geel, Belgium c Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany HIGHLIGHTS • TAEA organized the second proficiency test on radioactivity measurement in Turkey. • Massic activities of 137 Cs, 90 Sr and 40 K in black tea had to be measured. • 19 participant laboratories reported 41 results with 49% acceptable scores. • Only 5 participants could report 90 Sr-results but they were all acceptable. • labs were identified as in need of support to improve their gamma spectrometry. ARTICLE INFO Keywords: Radioactivity in tea powder Radioactivity proficiency test Environmental gamma ray spectrometry 137 Cs 40 K 90 Sr ABSTRACT A proficiency test amongst 15 Turkish laboratories with participation of 5 non-Turkish laboratories was orga- nized to determine the 137 Cs, 40 K and 90 Sr massic activities in black tea powder samples. The bulk material, consisting of tea produced in 2014, was mixed with contaminated tea that was withdrawn from the market after the Chernobyl accident. Nineteen laboratories reported 41 results. The evaluation of the results was based on the accuracy and precision criteria adopted by the IAEA Proficiency Testing Group and resulted in 49% acceptable results, 19% acceptable with warning and 32% were found to be not acceptable. 1. Introduction 137 Cs and 90 Sr are two of the main indicative radionuclides in nu- clear emergency cases and for environmental radioactivity monitoring due to their high abundance as fission products and relatively long half- lives. These radionuclides also pose significant health risks after a nu- clear incident due to both external radiation exposure (gamma rays emitted by 137 Cs) and internal exposure. Tea leaves, widely consumed in Turkey and in the world, accumulate 137 Cs and 90 Sr in large amounts. During and after a nuclear fall-out event, 137 Cs and 90 Sr that are de- posited on the ground enter the soil and are assimilated by the plants. These fission products may also be taken up directly by deposits on the leaves. Because of the dynamics of cesium and strontium and physical characteristics of the tea plant, 137 Cs and 90 Sr are retained in tea leaves for long times (Gökmen et al., 1995). To efficiently handle the aftermath of nuclear power reactor in- cidents like Chernobyl and Fukushima and other radiological emer- gency situations it is important that there are efficient networks of laboratories that perform radioactivity measurements. As contributors to such a network, the university and institute laboratories in Turkey rely on proficiency tests (PTs) to demonstrate the reliability of their analyses. It is desirable for Turkish laboratories to participate more often in PTs, but radioactivity measurement PTs organized by institutes in other countries often limit the number of participants due to limited supply of reference materials. Furthermore, importation/exportation procedures may hamper distribution of samples. The Turkish Atomic Energy Authority (TAEA), being the designated institute of Turkey in the European Association of Metrology Institutes (EURAMET) for io- nizing radiation metrology, is dedicated to organizing PTs on a regular basis to enable Turkey's national laboratories to check their analysis methods and help them in their accreditation processes. This paper describes the second PT organized by SNTRC (Sarayköy Nuclear Research and Training Center) of TAEA in the radioactivity field. It concerned the determination of massic activities (Bq/kg, dry mass) of 137 Cs, 40 K and 90 Sr in black tea leaves. A total of 65 test samples were prepared, and 20 of them were distributed in November http://dx.doi.org/10.1016/j.apradiso.2017.10.011 Received 6 March 2017; Received in revised form 2 October 2017; Accepted 5 October 2017 ⁎ Corresponding author. E-mail address: emin.yeltepe@taek.gov.tr (E. Yeltepe). Applied Radiation and Isotopes xxx (xxxx) xxx–xxx 0969-8043/ © 2017 Elsevier Ltd. All rights reserved. Please cite this article as: Yeltepe, E., Applied Radiation and Isotopes (2017), http://dx.doi.org/10.1016/j.apradiso.2017.10.011