Reality capture workflows raise the bar for safety in nuclear decommissioning

The process of decommissioning a power plant that contains nuclear materials is both complex and uniquely hazardous. In any plant there can be areas that have higher levels of radiation exposure than others – and the overarching principle for working in those areas is to perform the work in as little time as possible while keeping distance and shielding from radiation sources (ALARA–principle, ‘As Low As Reasonably Achievable’). The principle of maintaining exposure time “as low as reasonably achievable” is a cornerstone of safety in nuclear industry : the less time you spend in controlled areas, the better – from cost and safety perspective.

With new build projects, doing this complex planning with detailed 3D models is easier, but for the older plants which are being shut down across Europe, no such 3D models exist. For an environment in which time is a critical element, the traditional terrestrial laser scanning process has clear disadvantages – the field work is slow and during it you make contact with the plant structures. The scanning experts may not have clearance or training to enter critical areas, and they are also adding to their own personal risk of exposure.

Founded in 2019 as a service unit of Fortum, eSite is an industrial Virtual Reality solution provider who are no strangers to complex environments of plants, factories and construction sites. For example Fortum Nuclear Services is using eSite in the first nuclear decommissioning project in Finland, decommissioning of the FiR 1 nuclear research reactor. Working safely in the nuclear industry is a key concern, for obvious reasons, and nuclear safety in Finland has been improved continuously for more than 40 years.

By creating realistic 3D point cloud models from reality capture of areas due to be decommissioned next, an extra layer of safety can be created. Because the time spent by field operators performing decommissioning tasks at the field needs to be minimized, it is paramount that the work procedures they follow are both efficient and correct – something that can have an increased likelihood to succeed if rehearsed in virtual reality created through reality capture, says Miko Olkkonen, head of eSite.

“Having a room or an area that needs to be decommissioned in a nuclear plant means that you need to go in there, cut some pipes that once had radioactive water, and you need to do it safely. This also means that you need to do everything to make it as fast as possible and as safe as possible with the lowest radiation dose.”

When planning the work procedures virtually it is possible to refine them to be completed quickly and accurately, avoiding radiation hot spots. Every action taken in the controlled area of the facility means time spent being exposed to radiation. The principle, “as low as reasonably achievable” drives each of these choices. When combined with other sensors that can also map radiation, an overlay of radiation hotspots can be augmented into the visualizations – helping to identify risky areas ahead of time.

“We can do the reality capture in the morning, process it for the afternoon, put the scan into virtual reality glasses, and the field operators can practice the work they need to do for a 15 minute cut of the pipe. In virtual reality, you can practice where you walk, what you do, where you keep your equipment. You can practice to do to it faster, with fewer steps, avoiding hot spots. Of course the environment changes during the decommissioning and the advantage is that you can discard the initial reality capture, and the next time you need to perform work in that location you take a new reality capture of that moment,” says Olkkonen.

Inside Finnish nuclear power plants, where Fortum Nuclear Services and eSite operate, there are radioactive areas and rooms that are accessible to people only for few days per year during the nuclear power plant’s annual outage. During these few days, hundreds of maintenance tasks are performed with a minute accurate schedule.

The best practice for a decade has been to go in to these areas and perform stationary laser scanning. This has enabled planning for next year’s outage tasks during the operating phase of the plant, though the areas are not physically accessible. Even with 10’s of hours of scanning work, we have been able to capture only limited sections.