Case Study
Sheffield Forgemasters completed manufacturing, research and consultancy work to allow the restart of Unit 1 of the Beznau nuclear power plant in Switzerland, which was taken offline for two years until confirmed to be safe by the Swiss Federal Nuclear Safety Inspectorate (ENSI).
Sheffield Forgemasters 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.
As a result of the findings of the ultrasonic indications the reactor was taken offline for two years until it could be confirmed to be safe by the Swiss Federal Nuclear Safety Inspectorate (ENSI).
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.
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.
Using the same techniques employed in the original manufacturing in the 1960s Sheffield Forgemasters as faithfully as possible to produce a large cylindrical forging which was almost identical to the original RPV. Ultrasonic testing was conducted on the full-scale replica andand similar ultrasonic indications were discovered.
The replica RPV then provided an ideal platform for Non-Destructive and Destructive testing to be carried out which was not possible on the irradiated original RPV. Through this testing it was identified that the ultrasonic indications were due to non-metallic inclusions of aluminium oxide.Their presence was determined not to have a negative influence on the mechanical properties of the RPV.
The extensive root cause analysis, carried out by Sheffield Forgemasters, ruled out a significant number of potential origins of the ultrasonic indications. Many of these indications could have ended the life of the RPV. This, coupled with the almost exact replica, provided compelling evidence to ENSI and AXPO that the reactor was safe to restart.
The work carried out by Sheffield Forgemasters gave significant support to the overall safety case and allowed the reactor to be restarted after a significantly costly two year hiatus. It has also provided information which will help to assess the current and ongoing safety of the RPV and ensure the operation requirements of the whole power plant are met for the future of the reactors life.
This was a unique opportunity to be able to work on and preserve a piece of history.
Research Design & Technology Team
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