For all States with a Comprehensive Safeguards Agreement in force, the IAEA seeks to verify that all nuclear material remains in peaceful activities. It achieves this through the application of technical measures known as safeguards. The new Passive Gamma Emission Tomography (PGET) tool, which utilizes a technique known as passive gamma emission tomography, will enable the IAEA to verify the number of fuel rods – or pins – in spent nuclear fuel assemblies.
Unlike other tools used for verifying the content of spent nuclear fuel, such as the Digital Cherenkov Viewing Device and the Spent Fuel Attribute Tester, the PGET tool can also confirm the absence of missing pins from a spent fuel assembly in a closed container. This is very useful for applying safeguards at nuclear power plants, underwater storage facilities and encapsulation plants at geological repositories. According to Tim White, an IAEA technology expert, the use of passive gamma emission tomography to verify nuclear material will be a “very valuable addition to the IAEA safeguards toolkit”.
At the end of their useful lives in a reactor, fuel rods are stored and eventually disposed of or, in some cases, reprocessed. Verifying that the nuclear material in the rods is not diverted from peaceful use is a crucial part of assuring the international community that States are honouring their non-proliferation obligations.
To detect the presence of uranium or plutonium, the PGET tool takes three simultaneous measurements – of gross neutron and gamma ray counts, gamma ray spectrometry and tomographic imaging of spent fuel pin positions. It takes the tool only five minutes to take these measurements and an additional minute to process and analyse the data. In this way PGET “offers inspectors an additional data point,” said White. “It allows for a more complete picture of activities and increases the robustness of the verification process.”
The IAEA is still in the early stages of integrating PGET into its safeguards activities. It has been tested in spent fuel ponds at three nuclear power plants and is now ready for deployment in safeguards verification practices and for use in the field by safeguards inspectors. The European Atomic Energy Community (Euratom) has also expressed an interest in utilizing this technology for verification activities, and a number of countries may follow suit.