Development of Radiation Resilient Ultrasonic Sensors (RRUS)

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.

Objectives

The annual exposure limit for radiation workers is 10mSv[1]; 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.

Prototype radiation resilient transducer

Solution

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.

Conclusion

Ultimately, TWI was able to develop and manufacture an ultrasonic transducer that remained functional after a total radiation dose of ≈12MGy.

[1] The standard SI unit for radiation dose is Gray (Gy) and the factored for unit for biological interaction is Sieverts (Sv). For gamma radiation 1 Gy = 1 Sv.

Ultrasonic response post irradiation (≈12MGy) (76mm calibration block)

James Kern Senior Project Leader

James graduated from Sheffield University with a B.Eng and PhD in 1992. He worked as a metallurgist at Sandberg consultant engineers, a Senior Technologist at Rolls Royce and as Chief Materials Scientist at APPH (now Heroux Devtek), before joining TWI in 2014. He first specialised in hot forming and bonding processes before transferring to the NDT Group.

He has successfully lead numerous collaborative (Horizon 2020 and Innovate UK) and single client projects, leading research activities and developing manufacturing prototypes. Current areas of interest include radiation effects on materials and sensors, Geothermal Energy, ATEX, manufactured defects for calibration purposes and shearography.

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