Team gains unprecedented access to Chornobyl's Reactor 4

Bristol and ISPNPP researchers, led by Professor Tom Scott and Dr Maxim Saveliev, walk down the 'Golden Corridor', which links Unit 4 with the other reactors at the Chernobyl Nuclear Power Plant.

The New Safe Confinement (NSC) zone and within it, the sarcophagus erected over the failed Reactor 4.

University of Bristol researchers inside the control room of Reactor 3.

The University of Bristol team was given privileged access to the now infamous control room of Reactor 4 where they deployed specially developed radiation mapping and scanning sensors. These were also deployed inside the New Safe Confinement (NSC), the protective structure erected to cover the remains of the failed reactor and the original Sarcophagus, which was hastily constructed in the aftermath of the 1986 accident.

The deployment, funded by the EPSRC-funded Robotics and AI in Nuclear (RAIN) research consortium, was the team's fourth visit to Chornobyl and follows the signing of a Memorandum of Understanding in early 2021 between the University of Bristol and the Institute for Safety Problems of Nuclear Power Plants (ISPNPP), Ukraine National Academy of Science. The aim of this visit, a joint initiative between Bristol and the ISPNPP, was to further explore the value of autonomous and semi-autonomous radiation mapping systems in high-radiation environments. By deploying these systems in the Exclusion Zone and at the ChNPP, researchers were able to better define the location and amount of residual radiological hazards.

This time, the team demonstrated several robotic systems, fitted with ground-breaking sensing equipment developed between the universities of Bristol and Oxford as part of the RAIN project. The aim of each system was to collect highly accurate 3D models of the facility, coincident with radiation data, to accurately define the distribution and severity of the radiological risks.

The deployment was a significant milestone for both the Bristol and ISPNPP teams, whose aim is to develop new technology for decreasing risk associated with decommissioning nuclear facilities. The high-end 3D visualisations achieved by the team's mapping technology will aid the Ukrainian Government's dismantling project and the decommissioning of the power station. This deployment coincides with the site gaining licencing permissions to begin remote dismantling of the sarcophagus, followed by retrievals and packaging of the vast volumes of reactor core debris. It is expected that during the decommissioning radioactivity levels and distributions will change on a very regular basis, necessitating a suite of rapid, robotically deployed, scanning technologies that can quickly define how the hazard is changing – all to keep workers safe.

Lead researcher, Professor Tom Scott, from the University of Bristol and Co-Director of RAIN, said it was an exceptionally challenging but successful exercise and that the results would prove invaluable to the safe dismantlement of the reactor, and would also inform decommissioning programmes here in the UK.

"To actually venture inside the control room of the failed reactor was a tense and yet exhilarating experience. The team did a fantastic job of deploying our systems quickly and in challenging conditions. It's a huge reward after months of hard work and planning to know our technology performs well in real nuclear environments.

"This high-profile deployment was the culmination of several years of hard development work as part of the RAIN project. We're so pleased to have successfully demonstrated a capability that is both useful for Chornobyl decommissioning but also for legacy nuclear sites in the UK and elsewhere in the world.

"We are now entering a phase of decommissioning here in the UK, at Sellafield and Magnox, therefore we are developing new sensing systems, robotic solutions and special types of detectors because that technology is needed now.

"Robots can make nuclear decommissioning faster, cheaper and more importantly, safer! We would only be able to develop this technology with the guidance and information from our Ukrainian partners," said Professor Scott.

In the twelve months since their last visit, the team has made significant technological advances. This time they used cutting-edge radiation sensing and laser mapping solution designed as part of the RAIN project by the Bristol team in collaboration with a research team at Oxford Robotics Institute (ORI) lead by Professor Maurice Fallon, to address the challenging environment inside the shelter.

Dr Dave Megson-Smith, Senior Research Associate at Bristol's Interface Analysis Centre (IAC), said: "With this type of multi-sensor system we can help our Ukrainian colleagues in conducting a diverse set of advanced characterisation and survey tasks in the most challenging of environments."

Dr Peter Martin, also from the IAC and a Royal Academy of Engineering Research Fellow, said: "Entering the Chornobyl Nuclear Power Plant is far from trivial and in order to practice for the deployments we were allowed to deploy the sensing technologies in Reactor Unit 3 and the control room of Unit 4, before venturing inside the New Safe Confinement. We were very pleased that the systems performed exactly as expected, recording excellent data that we can quickly construct 3D digital representations from."

Mr Leonid Yakovenko, Head of the Chornobyl Nuclear Power Plant Radiation Safety Shop, said: "The success of this important research owes itself to the effective collaboration between the scientists of ISPNPP, the University of Bristol, and the specialist engineers from the Chernobyl Nuclear Power Plant. Together we have been able to carry out novel experiments using pioneering technology to assess the radiation situation at the Chernobyl NPP and, particularly, inside the new safe confinement zone.

"The Bristol team demonstrated the effectiveness of their scanning systems in high radiation conditions, producing detailed data within the facility and paving the way for more advanced remote robotic radiation mapping."

Dr Maxim Saveliev, Senior Researcher at the Institute for Safety Problems of Nuclear Power Plants (ISPNPP) in Ukraine, said: "Importantly, this scientific data will inform future planning for the eventual removal of fuel-containing material from the Shelter facility and will ultimately aid Chernobyl's transformation – and the area surrounding it - into an environmentally safe place.

"This is the second time we have worked with the Bristol team here at the Chornobyl nuclear power plant and the results of this most recent visit provide fresh impetus for continuing and strengthening our cooperation into the future."

Now back in the UK, the pioneering research team will further analyse the data collected at the site and provide the Ukrainian authorities with previously unavailable, highly detailed, and accurate maps of the distribution of radiation levels surrounding the condemned reactor.