CTU scientists, PhD student Jana Matoušková and Dr Lubomír Sklenka, have performed the first three-dimensional computed tomography of a technical object at the near-zero power training reactor of CTU, which had previously only been possible at high-power research reactors.

Neutron imaging is a non-destructive method used to examine the internal structures and material composition of optically opaque objects. This method is similar to X-ray imaging, for example. Unlike X-rays, low-energy neutrons from a research reactor can penetrate several centimeters of metals while sensitively detecting even small amounts of hydrogen, like in water or plastics.

Neutron radiography has been performed since the 1950s but has suffered from low sensitivity detectors and films. With sensitive electronic cameras looking at detection screens that emit light on the capture of neutrons, neutron radiography and even neutron computed tomography (consisting of several hundred views under different angles that are computed into a 3D model) has seen a steep rise at large research reactors all over the world.

Recently, low-price astronomical cameras have become available that are sensitive enough that Burkhard Schillinger of the FRM II reactor at Heinz Maier-Leibnitz Zentrum (MLZ) of Technische Universität München (TUM) downscaled the ANTARES imaging system at FRM II to a small portable detector that could be used at other facilities.

While the FRM II reactor is operated at 20 MW, the school reactor VR-1 has almost zero power, only 100 watts. Previously, it was not considered feasible to take neutron images on such low power reactors. The system was adapted to the needs of the VR-1 reactor, and the production, assembly of individual parts of the detector and testing of the detector, control system, and software took place at home during the COVID-19 lockdown.

In the spring of this year, the system was successfully tested, and the first digital neutron radiography was performed on the VR-1 reactor. In autumn, Ms. Matouskova and Dr Sklenka measured the worldwide first computed neutron tomography at a low power reactor at slightly increased reactor power at 500 Watts. A historical object, a Tibetan lock, from the private collection of Dr Sklenka was used as a sample for this measurement.

The neutron imaging system will be further characterized and improved in the framework of Ms. Matouskova’s PhD thesis, and together with MLZ/TUM, it may be copied for other low power reactors in the world. The results to date have shown that although neutron imaging in low power reactors is associated with several challenges, it is possible to operate a neutron imaging system there successfully. In the future, the facility should be used not only for the education of students at CTU but also for other research activities.

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