Nuclear decommissioning challenges exist the world over and require innovative approaches to ensure safe and cost effective dismantling of high hazard nuclear facilities. One of the most contaminated and complex components of a nuclear power plant is the reactor vessel, which needs to be safely and securely size reduced to manageable sizes for safe storage. Traditional mechanical and thermal cutting methods, such as reciprocating saw and plasma arc, pose significant challenges for remote deployment platforms. This includes the loss haptic feedback, difficulty dealing with reaction forces while maintaining uniform force and constant standoff distance between tool and the material surface. The second issue arising with current cutting techniques is the generation of high level secondary wastes and increased maintenance requirements. This is associated with frequent replacement of damaged tool components, which become highly contaminated, and the release of large volumes of debris and fumes from the cutting process. This results in increased operating costs and nuclear hazards to the workers.
Laser cutting is an alternative remote thermal size reduction technology, which minimises the complexity of deployment and secondary waste rising from the cutting process. TWI has been investigating the use of lasers for remote nuclear decommissioning work and has successfully deployed the technology on two separate nuclear sites in the UK, with clear tangible cost and safety benefits. The technology is now being considered for size reduction of an active research reactor on a Magnox site.
This work is representative of the thickness and geometry of the proposed reactor pressure vessel considered for laser size reduction on a Magnox site. The laser was able to cut through the demonstration reactor ring in around 7 minutes, as compared to the 40 minutes the work would have taken using a saw.
Once cut into smaller sections, the internal reactor ring can be encapsulated in appropriate containment canisters and stored for an extended period, allowing radiation levels to decay to an acceptable level and the reduction in time for this work to be done, as well as the remote use of laser technology, have evident safety benefits for industry.
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