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The goal of the Innovate UK RRUS project, partnered with Precision Acoustic Ltd, University of Sheffield and InnoTec UK was to develop the construction techniques required to manufacture an ultrasonic (UT) sensor for use on nuclear waste containers. These sensors would be deployed and expected to operate continuously without human interaction for between 3 and 20 years, depending on radiation level.
The annual exposure limit for radiation workers is 10mSv; a full body dose of between 2.5Sv and 3.0Sv will result in a death rate of approximately 50% within 30 days, assuming no medical treatment.
Radioactive nuclear waste is categorised as high, intermediate and low level (HLW, ILW and LLW respectively). The contact dose rate for HLW and ILW containers is ≤3.5MGy/yr and 88Gy/yr respectively. For a radiation resilient sensor to operate for three years on a HLW container it must be capable of withstanding ≈10MGy equating to over 20 years on a ILW or LLW container.
TWI performed a literature review to identify radiation resilient piezo-ceramics together with methods of joining these crystals to a front wear plate. Trials were undertaken to assess the joining of the different material combinations identified, and the assemblies manufactured were tested in a gamma radiation environment to assess their radiation resilience.
The assemblies remained operational after exposure to ≈12MGy of radiation. Various design options and cabling solutions were investigated to develop an ultrasonic transducer; when the assemblies were incorporated into the prototype they were found to function well.
Ultimately, TWI was able to develop and manufacture an ultrasonic transducer that remained functional after a total radiation dose of ≈12MGy.
Dr Kern graduated from Sheffield University with a B.Eng (Hons) in Engineering Materials. He then stayed at Sheffield University and obtained a PH.D in ‘The processing and properties of amorphous alloy wire and its use in Tyre Reinforcement’.
Dr Kern joined TWI in 2014 and worked in the Specialist Materials and Joining group running research projects and industrial programs related to brazing (similar and dissimilar materials), diffusion bonding and joint characterisation. Then in 2017 he moved to the NDT group and has managed multi-disciplinary teams in both UK and EU funded collaborative projects such as TankRob, the manufacture of an ATEX zone 0 robotic probe for the ultrasonic inspection of large oil containers and RRUS the development of radiation resistance ultrasonic probes for nuclear applications.
Previously, Dr Kern worked as the Chief Material Scientist for APPH (now Heroux Devtech) overseeing the material requirements and developments for the manufacture of aircraft landing gear. Prior to this he was an advanced technologist at Rolls Royce and specialised in hot forming and diffusion bonding, controlling the hot forming process at Bankfield site. Later, he went on to support the RR Ghyll Brow site and specialised in non-destructive testing. All of these roles included the development of new products and equipment introduction. He has also worked as a fire investigator and site/lab based metallurgist and has, over a period of 20 years, visited over 600 sites, overseen multiple failure investigations and interpreted British and international standards to allow bespoke testing of materials and structures.
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