This blog is written by Vera Uushona, a radiation physicist at the National Radiation Protection Authority of Namibia. Vera studied radiation science at the Centre of Applied Radiation Science and Technology (CARST), North West University (Mafikeng Campus) focusing on nuclear forensics.
Why do we need Nuclear Forensics?
Nuclear energy is a controversial topic, with some concerned at the potential safety issues it creates. However, it is an important source of low-carbon electricity, which provided 10% of global electricity supply in 2018. Many countries see nuclear power as a critical part of their energy transition from oil and gas. The International Energy Agency predicts that electrical generation from nuclear will increase by almost 55% by 2040.
Nuclear material and radioactive sources are toxic and poisonous to people and the environment, and strict measures are required to ensure that they remain used for peaceful purpose. This is why the field of Nuclear Forensics is so important.
Where does nuclear material come from?
The main ingredient in nuclear energy production is uranium, a naturally occurring radioactive material that is widely distributed within the Earth’s crust and extracted from every continent on the planet except Antarctica. The main uranium-producing countries are Australia, Canada, China, Kazakhstan, Namibia, Niger, the Russian Federation, South Africa, the USA and Uzbekistan.
The Nuclear Fuel Cycle (WNA, 2019). [U3O8 = Yellow cake, UF6=Uranium hexafluoride; explained in text]
Nuclear energy is produced from a series of processes known as the nuclear fuel cycle. The process starts with mining, which results in the production of a substance known as ‘yellow cake’. The yellow cake is concentrated into uranium hexafluoride, and enriched to increase concentration of the isotope uranium-235 (a particular form of uranium). The enriched material is converted into uranium oxide or uranium metal alloys for use as fuel for nuclear reactors. Used fuel can be reused in the cycle or disposed of in a safe manner.
Uranium yellow cake (Wikipedia)
The Birth of Nuclear Forensics
Incidents of illegal possession, transfer and unauthorized acts involving nuclear material were first reported in the early 1990s, mainly from Europe due to the breakup of the Soviet Union. The scientific community therefore needed to find a way to characterise nuclear and other radioactive materials found outside of regulatory control, to determine their processing history, origin and potential illicit trafficking route. This gave rise to the discipline of nuclear forensics.
Seeking clues in nuclear ‘fingerprints’
Nuclear forensics is a branch of forensic science that requires the ability to measure characteristics, or ‘signatures’, of nuclear and other radioactive materials. All radioactive material carries a signature, like a fingerprint. The signature describes characteristics of the material, such as which chemical elements the material contains, how heavy or light these elements are (‘isotopic abundance’) and other physical and chemical properties. Crucially, the signature can be used to link nuclear material back to the original radioactive minerals from which the material was made, and can also reveal links to locations, individuals, chemical and physical processes, production dates and even intended use.
Conceptual diagram of forensic signatures, showing that many characteristics may have a range, but by investigating a variety of these characteristics we can pin-point an a individual signature. (Credit: IAEA, Introduction to nuclear forensic course, Ghana, 1-4 October 2019).
National Nuclear Forensics Library
The ultimate goal of nuclear forensics is to build up a National Nuclear Forensics Library (NNFL) that can be used to compare sample data to both measured and modeled nuclear material characteristics. The NNFL is a national system of expertise and information (not a database) that can be used to identify nuclear or radioactive material found out of regulatory control. It is important that each country producing nuclear material has a NNFL.
How to develop a National Nuclear Forensics Library – a step by step guide:
1) Get the go-ahead to develop a library – this may be an agreement (‘memorandum of understanding’) between different institutions, or a Government’s commitment;
2) Coordinate the collection of information for the library with subject matter experts, regulatory authorities, law enforcement, etc.;
3) Find existing nuclear materials data for inclusion in the library; this includes the type, the production process, impurities present. This information can be obtained from the producers of the material;
4) Study the characteristics of the nuclear forensics signatures needed for comparative analysis;
5) Identify and fill any gaps in data (see which signatures are not available).
6) Develop or modify databases;
7) Modify the different analytical tools used to determine and compare the signatures as required
The development and maintenance of a Nuclear Forensics Library is a continual process of surveying, collecting, organizing, and interpreting information about nuclear and other radioactive material produced and used.
How does it work in practice?
To explain how the process works, let’s consider an example from Namibia. Namibia is the 4th largest producer of uranium in the world, generating 10% of global uranium in 2018. It is therefore important to understand the signatures of different uranium deposits from Namibia, to add to the Nuclear Library to be used in case of illicit trafficking.
Vera in the nuclear forensic laboratory at CARST, during preparation of samples for analysis.
Radioactive materials including uranium ore, uranium ore concentrate, uranium tailings (mine waste) and tailings water from Namibia’s uranium mines were analysed. To carry out the analysis, we used various scientific tools (such as Induced Coupled Plasma Mass Spectrometry, Gamma spectrometry and Scanning Electron Microscopy-Electron Dispersion Spectrometry). These tools allow us to understand a range of characteristic signatures for each material, including elemental concentration, morphology, lead and uranium isotopic ratios, and an estimation of how old the uranium mineralisation is. We can then use this information to tell the difference between uranium bearing materials from different mines.
Nuclear forensics is just one aspect of Radiation Science, a broad field that deals with the application of a range of radiation and nuclear science and technology and brings together geoscience, physics, chemistry and biology. It is applicable in energy, agriculture and water resource management, biology and medicine, environmental management and nuclear security, and will continue to be important long into the future.
Wow, a first for Namibia, indeed excellent. Well done, now other Nuclear scientists should follow suit.