Task Groups

"Ring of Five" Task Group

[ Chair: Olivier Masson - olivier.masson@irsn.fr ]

Overall context

The "Ring of Five" (Ro5) is an informal club based in Europe with the purpose of exchanging data on occasional concentrations of man-made radionuclides in the atmosphere.

Back in the 1970s and early 1980s only few countries ran surveillance programs for low concentrations of man-made radionuclides in ground level air. With the emergence of germanium detector spectroscopy, however, cost-effective access to such measurements became more readily accessible. Sweden was one country that pursued these techniques, mainly with the goal to demonstrate that a comprehensive nuclear test ban would be verifiable. The last atmospheric nuclear explosion took place in China in October 1980, and in the following years the background of bomb debris came down to levels where other radionuclide emissions could be more easily detected. In 1983 and in the following two years, man-made radionuclides, both fission and activation products, occurred occasionally in Northern Europe, and a co-operation started between Sweden and the Federal Republic of Germany attempting to pinpoint the sources of these emissions. Finland, Norway and later Denmark, were soon drawn into these efforts. Sometimes the events caught the interest of the Press and it started to become clear that an "early warning" system would be highly desirable.

It was then decided that upon any unusual detection seen in one country, then the others should be informed through telephone calls to people located in the other countries’ laboratories. A list was maintained including business, as well as home, telephone numbers. "The Ring of Five" was born. "Ring" because in such an event, we used to call each other in a circle and "Five" because we were initially representing only the five previously mentioned countries. This was, and still remains, a totally informal arrangement independent from any governmental or international authority.

As communications techniques developed the “Ring of Five” went next through a phase based on using fax, and has now reached full use of e-mails (the ancient techniques of phone and fax will, however, always stay as a backup). This simplest and convenient way of exchange information on detection matches perfectly the aim to rapidly inform all members involved and has to be kept as it is. Beside this tool, it is now desirable to move on an internet-phase making use of internet capabilities and to widen the network. This is why the “Ring of Five” is now to be launched as an IUR new Task Group.

Especially after Chernobyl and a couple of meetings on low-level radiation measurements in Poland, the club expanded to some 20 countries represented by about 70 persons. But it kept the same name, as a mean to recall its origin, and because we found this name to be somehow mysterious, therefore capable of exciting interest …

The “Ring of Five” is fairly dormant most of the time. But when something special happens, like in May 1998 when a smelter in southern Spain emitted 137Cs, or more recently when 131I was detected on several occasions across Europe (2011-2012), this network was quickly triggered. After the Fukushima accident, most of the airborne data on the European scale were reported from laboratories participating in the Ro5. The “Ring of Five” laboratories were actually the first to detect the plume in Europe.


The Ro5 Task Group is being set up with the overall objective of widening the network and promoting it with more activity and more visibility based on exploiting the IUR web site. The TG shall assess in particular the following more detailed and provisional objectives:

  • First, the Ro5 Task Group will work on detection of airborne radionuclides and inform partners of any significant and abnormal rising level.

  • Second, upon any detection, the Ro5 Task Group will gather any document related to the origin, cause, possible reasons, release date, meteorological data, trajectories and all existing information (videos, newspaper, …) that makes possible to explain the level rise. This will be performed based on exploiting a restricted space on the IUR website exclusively dedicated and accessible to Ro5 members (ID and passwords required).

  • Third, the Ro5 will consider technical aspects, and particularly exchange all relevant information about technological novelties and upgraded methodologies that would allow to trap airborne radionuclides in a more efficient way and to measure them using the best available measuring equipment. This will be done in the framework of restricted web-pages to which Ro5 members could access via the IUR website.

  • Finally, the last objective is to propose a collaborative approach to solve current questions related to numerous fairly unknown processes involved in atmospheric transfers and leading to deposition and residual airborne levels. Regarding the radioecological aspects, airborne radionuclide levels depend on meteorological conditions, and their persistence in the atmosphere is related both to the previous deposition level and to the initial stock or released amount. Washout, rainout and dry deposition processes, wind-driven re-suspension and re-emission of radionuclides by biomass burning, gas to particle transfers, size distribution of airborne radionuclides, residual airborne level in the high altitude, are some examples of the current topics of interest.


The Task Group will make all possible efforts to produce recommendations about technical subjects, to initiate result comparisons, to test equipments and promote collaboration on subjects of common interest. It will also consider studying nation-wide data or times series on the European-wide scale since airborne radionuclides and radionuclide labelled air masses do not know borders!

As they become available, after some years of operation of this TG, its output results, recommendations and findings will be published within the IUR report series, with a collective authorship duly mentioned.  

A first and short proceeding will be produced after the forthcoming workshop

1st Ro5 Workshop - Barcelona - 7 Sept 2014

As a side event of the last ICRER Conference in Barcelona, the Ring of five (Ro5) network has held its first enlarged international workshop on Sunday 7 September, 2014. This workshop was organized by the French Institute for Radiological Protection and Nuclear Safety (IRSN) under the aegis of the International Union of Radioecology (IUR) and with the support of the Norwegian Radiation Protection Authority (NRPA). Download the program

Fifty five attendees participated to this first edition with 18 oral communications and 8 posters. Findings related to recent trace events characterization, methodologies, organizations and a special focus on iodine were presented. Beside technical and scientific discussions it has been proposed to create sub-groups based on prior identification of on-going and future R&D priorities established in the framework of the FORUM initiative. Download here a short report


Provisional TG membership (based on the list of Ro5 members)

  • Wolfgang Ringer AGES, Linz, Austria

  • Christian Katzlberger AGES, Wien, Austria

  • Ilia Penev INRNE, Sofia, Bulgaria

  • Petr Rulík, Helena Malá, Jan Skrkal: NRPI, Prague, Czech Republic

  • Sven Poul Nielsen Risoe National Laboratory, Roskilde, Denmark

  • Aleksi Mattila, Ari-Pekka Lepänen, Seppo Klemola, STUK, Helsinki, Finland

  • Thomas Taffary, Gilbert Le Petit, Xavier Blanchard : CEA/DAM, Bruyères le Chatel, France

  • Olivier Masson, Rodolfo Gurriaran: IRSN-PRP-Env, Cadarache, France,

  • Jacqueline Bieringer, Clemens Schlosser, U. Stöhlker, Matias Zähringer, H. Sartorius BFS, Freiburg, Germany,

  • Thomas Steinkopff, DWD, Offenbach, Germany,

  • Jochen Tschiersch, GSF, ISS, Helmoltz Zentrum, Neuherberg, Germany,

  • Herbert Wershofen, PTB, Braunschweig, Germany,

  • Horst Keller, University of Mainz, Germany,

  • Péter Zombori, AEKI, Budapest, Hungary,

  • Sigurdur Emil Pallson, IRPI, Reykjavik, Iceland,

  • Sergio Mancioppi, ANPA, Rome, Italia,

  • Gintautas Berlinskas, JRC/RL, Vilnius, Lithuania,

  • Marielle Lecomte, MS, DIV. RADIOPROT, Luxembourg, Luxembourg,

  • Antoine Kies, LPR, CU, Luxembourg, Luxembourg,

  • Pieter Kwakman, RIVM, Bilthoven, The Netherlands,

  • Finn Ugletveit, NRPA, Osteras, Norway,

  • Izabela Kwiatkowska, Krzysztof Isajenko, CLRP, Warsaw, Poland,

  • Jerzy Wojciech Mietelski, ifJ, Kracow, Poland,

  • Andrzej Miecznikowski, Technical University, Wroclaw, Poland,

  • Milagros Pozuelo Cuervo, Lourdes Romero, CIEMAT, Madrid, Spain

  • Fernando Legarda, UBC, University of the Basque Country, Bilbao, Spain,

  • Isabel Valles, Arturo Vargas, INTE/UPC, Barcelona, Spain,

  • Catharina Söderström, Lars-Erik De Geer, Anders Ringbom, Torbjörn Nylen, Stefan Ban, Neda Tooloutalaie, Klas Elmgren, FOI, Stockholm, Sweden,

  • Sybille Estier, Giovanni Ferreri, SFOPH / VS, URA, Bern, Switzerland,

  • Hansruedi Völkle, Dept.de Physique / Université de Fribourg, Switzerland,

  • Derek Hammond, George Etherington, HPA, CRCE, Chilton, United Kingdom,

Many other colleagues involved in the atmospheric field are welcome in the Ro5 Task Group. Preference is granted to potential members running stations or networks for surveying atmospheric radionuclides with a capacity to measure concentrations in the micro- or tens of micro-Bequerel per cubic meter range. Having a common culture will facilitate the information exchange and discussion. Others members active in the field can also join as long as the group remains within a reasonable and manageable size.

How to become a member of the Ro5 Task Group  

You are interested or involved in trace determination of airborne radionuclides and want to join the Ro5 Task Group ?  

1st step : you are invited to register as an IUR member by filling the registration form https://www.iur-uir.org/en/connexion/inscription The secretariat will validate your registration.  

2nd step: Then, to get the maximum benefit of this registration  (access to the restricted web pages of the Ro5 TG or of the IUR web site in general, access to the online version of the Journal of environmental Radioactivity  or IUR co-sponsored conference at a privileged rate), please proceed with your IUR subscription (annual fee payment) and become an active IUR member https://www.iur-uir.org/en/join-the-union Please specify at the same time your wish to join the Ro5 Task Group by email to contact@iur-uir.org and the secretariat will open access for you to the group's restricted area on the web site. When you will log in, you will be able to access the following dedicated space on the right of the website in the section “Task groups”

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