Glass beads also used for Teddy bear filling – a new reference material for radioactivity measurements

Glass beads © MBphotos - 

The scientific network, CELLAR (Collaboration of European Low-level underground Laboratories) in partnership with the JRC developed a new reference material (RM) for radionuclides measurements. This RM will assure the quality of low background radioactivity levels.

Low level radioactivity measurements are performed underground because they are not affected by the background noise created by the cosmic rays. Consequently, much lower levels of radioactivity can be analysed precisely underground, compared to when conducted above ground.  RMs play a fundamental role to assess the quality of data. However, those RMs available have been mostly developed for environmental radioactivity studies. No RM is available for radiopurity analysis of construction materials that are, e.g. due for large detector assemblies for detecting rare nuclear processes like double beta decays and neutrino interactions.  Therefore, scientists from the JRC-Institute for Reference Materials and Measurements (IRMM) contributed to the development of a suitable RM. It turned out that industrial glass beads used, for example, for fillings in toys such as teddy bears have several suitable properties as the glass is inert, can be stored at room temperature, can be filled easily into containers, and their level of natural radioactivity is very low. Ten expert laboratories – including the radionuclide laboratory of the JRC-IRMM – took part in the certification of the material through gamma-spectrometry analyses of radionuclides. The glass bead RM was certified for 7 radionuclides.

The reader should be reminded that natural radioactivity is present everywhere, including the human body. The level of radioactivity in these glass beads is quite low and there is, of course, no radiological danger associated with them. One drawback of the glass beads is that the activity is so low that they are not suitable for above ground measurements. However, the number of detectors located underground has increased linearly with time in the past 20 years.  There is, therefore, a need for specially designed reference materials for underground laboratories and this is the first of such reference materials.

Read more in: P.P. Povinec et al.: “Reference material for natural radionuclides in glass designed for underground experiments“, J. Radioanl. Nucl. Chem. 307 (2016) 619-626, doi:10.1007/s10967-015-4202-6