Mario Kostan, an international PhD student undertaking his research work with Brunel Innovation Centre alongside TWI and NSIRC; has developed a novel ultrasonic transducer in response to the industry’s need for inspection and condition monitoring of high-temperature pipelines in ageing nuclear power plants.
High-temperature pipe cracks are at the root of steam power failures in Europe. According to IAEA’s Reference Technology Database, such an event on a nuclear power plant has an average cost of £120 million, including outage costs, emergency repair costs, insurance and legal costs. Since only one growing crack can cause a major failure, they have to be inspected and monitored regularly.
Regular maintenance of the plants is carried out during planned outages at ambient temperature. This involves the erection of scaffolding and removal of the insulation to gain access to the pipes, making inspection a costly process. Also, in situations when defects such as creep, corrosion or fatigue are detected, there is always a question of whether to replace the defective part. If the defect is not yet severe enough to warrant replacement, it will be earmarked for close inspection and reassessment during the next outage. However, uncertainties in the calculation of the time period until the next inspection can lead to failure of the defective part between shutdowns, with potentially fatal consequences. Thus, in-situ condition monitoring technologies and techniques need to be developed.
Together with the support of Dr Channa Nageswaran and Dr Abbas Mohimi from TWI, Mario Kostan has developed a novel ultrasonic transducer that utilises an advanced piezoelectric single crystal for generation and reception of ultrasound at up to 580°C. Professors Tat-Hean Gan and Luiz Wrobel (supervisors of Mario) were excited with the achievement as this development will change the future of NDT inspection at high temperature. This new type of transducer will decrease the shutdown time required for inspection purposes, eliminate catastrophic accidents resulting from superheated pipe failures and ultimately increase safety in nuclear power plants.
Mario’s approach in the development of the novel transducer has been to stay close to the design of a conventional ambient-temperature transducer but to replace each of its components with appropriate high-temperature substitutes. All the components are integrated within a stainless steel housing, together comprising a novel high-temperature ultrasonic transducer. Successful initial testing of the transducer in the lab environment has showed its applicability for thickness gauging and defect detection at up to 580°C. As an NSIRC student, Mario also gets the opportunity to validate the transducers in a real-world working environment, ie a power plant.
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