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Winning Entries to IAEA Tomography Reconstruction and Analysis Challenge to Aid Safeguards Activities


A submerged spent nuclear fuel assembly is analyzed by the Passive Gamma Emission Tomography system in a spent fuel pool. (Photo: IAEA)

Researchers from Italy, Finland and Austria have won the latest IAEA safeguards technology online competition – the ‘IAEA Tomography Reconstruction and Analysis Challenge’. By taking radiation measurements from 360 degrees, tomography allows for the production of 3D images of spent nuclear fuel stored in closed containers, aiding nuclear material verification.

“In my work, I focus on how tomography can be used in nuclear medicine, including in oncology, cardiology, and neurology,” said the first prize winner of the technology challenge, Luca Presotto from the Nuclear Medicine Unit, IRCCS Ospedale San Raffaele, Italy. “Before seeing the announcement for this challenge, I had no idea that my experience and knowledge could also contribute to international peace and security.”

The IAEA regularly holds technology challenges – online competitions open to all – to improve the effectiveness and efficiency of safeguards activities. This third challenge focused on ways to enhance the verification of the peaceful use of nuclear material. Participants were tasked with developing algorithms to analyze data collected as part of safeguarding spent nuclear fuel.

The verification of spent nuclear fuel – irradiated fuel discharged from a nuclear reactor core – is a significant part of the IAEA nuclear safeguards mission. Nuclear safeguards are applied to spent fuel because spent fuel contains plutonium, a possible ingredient in nuclear weapons. The IAEA applies safeguards to around 260 facilities around the world that have spent nuclear fuel ponds onsite.

Participants in the technology challenge were provided with data taken by the recently developed Passive Gamma Emission Tomography (PGET) system. Authorized for use by safeguards inspectors in 2017, the PGET system is the most sensitive system in the inspector’s toolkit for the inspection of irradiated material. The PGET system records radiation measurements that are subsequently used to produce cross-sectional images of the gamma radiation emitted by spent nuclear fuel assemblies and material in closed containers. With these images, nuclear safeguards inspectors can more effectively and efficiently verify that spent fuel assemblies contain the spent fuel declared by national and regional authorities. With the new methods for image reconstruction developed by the challenge winners, clearer images can be produced to allow safeguards inspectors to not only to check if spent fuel is missing, but also verify that the nuclear material held in the container is the same as declared.

All entries to the technology challenge were evaluated by IAEA experts and had to meet a comprehensive set of criteria: quality of image, accuracy of processing, computational speed, complexity of setup, the need for information in advance and the originality of the approach. The algorithms developed will continue to be refined and reviewed to meet the IAEA’s requirements. “Future improvements can be found in this area going forward,” said the second prize winner Rasmus Backholm from the Helsinki Institute of Physics, University of Helsinki, Finland. “We plan to continue the work on the problem to further refine the reconstruction of PGET images via the algorithm.”

Verifying spent nuclear fuel within closed containers presents various challenges, and this has led to different types of solutions proposed. “The three winners have different but complementary approaches,” said third prize winner Christian Thomay, an independent researcher from Austria. “Each of our solutions analyses the data from the PGET system using different methods.”

The IAEA will now look at how the different approaches could be used and how the solutions can improve current methods of PGET image reconstruction. “In reality, for some irradiated material in closed containers, the geometry is not well known,” said Racquel Lovelace, Associate Instrumentation Engineer at the IAEA. “We have three practical solutions that can help us in such cases.”

The first IAEA technology challenge for nuclear safeguards, launched in 2016, looked at enhanced image processing techniques for an existing safeguards instrument, the Improved Cherenkov viewing Device (ICVD). The ICVD allows safeguards inspectors to confirm that the declared number of spent fuel assemblies are present in spent fuel ponds. The second challenge, in 2017, focused on robotics to aid nuclear material verification. Opened in January 2019, the ‘IAEA Tomography Reconstruction and Analysis Challenge’ attracted entries from across the world during its six-month duration.

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