The Radiation Tolerance and Development of Robotic Platforms for Nuclear Decommissioning

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Abstract

There is an increasing desire to deploy low-cost robotic systems in nuclear decommissioning environments. These environments include long-standing nuclear fuel storage ponds such as those at the Sellafield site in Cumbria, UK as well as areas affected by expulsion of radioactive material from sites such as the Fukushima accident in Japan 2011. An area of concern for the successful deployment of robotic platforms in a radioactive field is their radiation tolerance. It is necessary to understand how the low-cost components used within robotic platforms react to radiation exposure in a nuclear decommissioning environment. This thesis discusses the radiation tolerance of multiple commercial-off-the-shelf (COTS) components that are commonly used within a robotic platform up to an expected yearly total dose of 5 kGy(Si). It was found that COTS voltage regulators are susceptible to gamma exposure, however, development of a discrete voltage regulator showed an increased tolerance to radiation under certain load and temperature conditions. Inertial measurement units were also investigated and found to be susceptible to a total ionising dose <1 kGy(Si). Applying experimental results gathered from the radiation tolerance of COTS components should allow the development of low-cost robotic platforms that are capable of characterising nuclear decommissioning environments increasing efficiency and safety. Two robotic platforms were designed as part of this research study with the nuclear decommissioning environments prioritised for characterisation the internal state of submerged nuclear facilities and the surrounding geology of nuclear fuel storage ponds. Over-used facilities such as the Sellafield legacy ponds, and hurriedly contained radioactive leaks from the Fukushima accident have created environments that require characterisation. In both instances, the exact location of spent fuel is not fully understood, with the likelihood that leaks into the surrounding geology have formed and remain uncharacterised. An underground burrower capable of characterising the radiological environment of the geology underneath and surrounding spent nuclear fuel storage ponds has been researched and prototyped. Experimentation has suggested the use of a hammering mechanism device may be capable of deployment with future work required to develop the device further. A second robotic platform entitled AVEXIS was also developed to characterise the unknown physical and radiological submerged environment. Work undertaken included development of the robotic platform to increase robustness and allow the deployment of multiple sensing technologies. Technical demonstrations of the submersibles' abilities were conducted in Japan to confirm the capability of the platform to characterise the Fukushima Nuclear Power Plant.

Keyword(s)

Nuclear Decommissioning; Nuclear robotics; Radiation tolerance; Robotics

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