A UK manufacturer of components for civil nuclear power has completed manufacturing, research and consultancy work to allow the world’s oldest working nuclear reactor to restart.
Sheffield Forgemasters International Ltd (SFIL) was contracted by plant operator, AXPO, to investigate the origin of ultrasonic indications which were detected in the Reactor Pressure Vessel (RPV) of Unit 1 of the Beznau nuclear power plant (KKB) in Switzerland, which was taken offline for two years until confirmed to be safe by the Swiss Federal Nuclear Safety Inspectorate (ENSI).
Forgemasters manufactured a large cylindrical forging, identical to the body of the RPV, using techniques employed in the original 1960s manufacture and also acted as engineering and metallurgical consultants, establishing a root cause analysis and delivering detailed reports to support the safety case which permitted the reactor to restart.
Prof Jesus Talamantes-Silva, group design and technology director at Sheffield Forgemasters International, said: “This detailed body of work provided both AXPO and ENSI with critical pieces of information, allowing them to assess the current and on-going safety of the RPV.
“Fundamental to the project was the recreation of the ultrasonic indications in the full-scale replica; this was only possible by mimicking the original manufacturing route as faithfully as possible. Using material from the replica, the response to ultrasonic inspection – which was almost identical in both forgings, was attributed to non-metallic inclusions.
“This finding then allowed the replica to act as a surrogate for the Beznau RPV, permitting destructive and non-destructive tests to be carried out, which are impossible to do on the irradiated RPV. This testing established that the non-metallic inclusions were aluminium oxide and their presence did not have a negative influence on the mechanical properties and therefore safety of the RPV.”
As an engineering consultant for the project, Sheffield Forgemasters was responsible for the entire process of recreating the RPV section, conducting materials testing and establishing a root cause analysis.
The root cause analysis ruled out a significant number of potential origins of the ultrasonic indications – many of these could have curtailed/ended the operating life of the reactor. This, coupled with the replica, provided compelling evidence to ENSI and AXPO that the reactor was safe to restart.
Prof Talamantes-Silva added: “There are few companies in the world with our capacity to deliver this kind of civil nuclear materials consultancy, which is crucially relevant to the inaccessible RPVs of older power plants and offers the chance to identify manufacturing and age issues before they become critical.
“This project has enabled the Beznau reactor to restart after a very costly two-year hiatus and ensures that the operational requirements of the power plant are met for the future of the reactor’s life.”
The Beznau nuclear power plant is a Westinghouse designed Pressurised Water Reactor operated by the Swiss energy utility Axpo, located on an artificial island in the Aar river in Döttingen, Canton of Aargau, Switzerland. It has produced energy since September 1969 and is the world’s oldest nuclear power plant still in commercial operation.
Sheffield Forgemasters is a global supplier of components for civil nuclear power and specialises in the casting and forging of ultra-large components required in the heart of a nuclear power plant.
The company is now a world leader in the delivery of technology enabling it to tap into markets including Small Modular Reactor and pressure vessel development and has recently partnered with a Canadian company on the design of one of the world’s first fusion nuclear reactors.