Krypton-85 for the detection of plutonium production
The Atom Trap Trace Analysis (ATTA)-group of the ZNF is working to develop a method to discover clandestine plutonium production, and to prove the viability of their approach. The method is based on experimental ultra-trace analysis using a magneto-optical trap, which should make the source of a trace isotope, krypton-85, detectable when coupled with meteorological methods. Krypton-85 is a fission product that is produced by the breeding of plutonium, and for which there are very few natural sources outside of anthropogenic production.
One of the biggest challenges for the Nuclear Non-Proliferation Treaty (NPT) is the exposure of clandestine activities related to the production of fission material for non-civilian projects. The Non-Proliferation Treaty allows and actively supports each member state in building up civil nuclear capabilities. An extensive search for clandestine activities was not intended. The lack of this facet of the treaty was only made clear by the discovery of the Iraqi nuclear weapons program. The political solution consists of additional protocols for the NPT, which provide the International Atomic Energy Agency with means to discover clandestine activities. Our goal is to develop a physical method for this purpose.
The types of measurements that would have to be undertaken to validate meteorological models was discussed with the meteorologists at the university. This led to the development of a specific sampling device, which takes samples in three-hour intervals. The device operates in parallel with the northern measuring site for krypton-85, which takes air samples on a weekly basis, and is operated by the ZNF in cooperation with the Federal Office for Radiation Protection. These samples are to be measured with ATTA, in order create a good basis of data to aid in discovering the precise locations of possible sources. Furthermore, the first simulations of the possible discoverability of unknown sources have already been conducted with the Zentralanstalt für Meteorologie und Geodynamik (ZMAG) in Vienna.
In cooperation with European and American geoscientists, a system was planned which would be able to automatically separate krypton from air samples within a volume of up to 5 liters of air. This system was designed in such a way that it could also be modified for use in the analysis of a gas sample that was taken from the groundwater, and not from the air. This is important, because krypton-81, which can also be analysed with ATTA, is of interest to geoscientists because it allows them to make age determinations of closed systems on a timescale of a million years.
Concurrently with all these other activities, the work on the ATTA-experiment itself pushed forward, and was completed. Specific vacuum-UV-lamps (first successfully development in 2011) have been integrated into the experimental design. The first trial runs showed that the design worked as expected, and the final adjustments and the first tests with stable krypton isotopes are to be undertaken. Once these are successfully completed, the design will be converted for use with rare krypton isotopes and first calibration measurements will be conducted. The system for the separation of krypton from air samples will be constructed presumably in the upcoming year. Once this is completed, a whole device for the trace analysis will be available. Given that the mere availability of a measurement device is not necessarily sufficient to convince the IAEA that the method presents a practicable technology for safeguards, further steps will be necessary to prove its worth.
Besides the meteorological studies, which are currently undertaken in order to better the understanding of the source-receptor-connection, the political and legal impacts of measurements and possible discoveries have to be further studied. This should include the possibility that the analyses at the ZNF point to an authentic unknown source.