Uniper completes dismantling of two RPVs in parallel

23 March 2022

Germany's Uniper Anlagenservice GmbH has become the first company to complete the dismantling, segmentation and packaging of two reactor pressure vessels (RPVs) in parallel within one year. In December 2021, the company successfully completed the dismantling of the vessels of both Sweden's Barsebäck unit 1 and Germany's Neckarwestheim I.

Uniper's remotely-operated thermal cutting station with robot being used at Barsebäck 1 (Image: Uniper)

Uniper Anlagenservice - a decommissioning subsidiary of the utility Uniper - acted as consortium leader in both projects. For the Barsebäck project, the consortium partner was Nukem Technologies Engineering Services GmbH. At Neckarwestheim, it worked with GNS Gesellschaft für Nuklear-Service mbH and Westinghouse Electric Germany GmbH.

In Sweden, Uniper Anlagenservice has been contracted to dismantle the RPVs of four pressurised water reactors: Barsebäck units 1 and 2 and Oskarshamn units 1 and 2.

In December last year, the company completed the dismantling and packaging of the RPV of Barsebäck 1 within one year.

The robot cutting a section of Barsebäck 1's RPV (Image: Uniper)

Barsebäck 1's cylindrical pressure vessel was initially thermally cut into 13 rings between 0.9 and 1.8 metres high, by Nukem Technologies. A customised robot system with a high-load capacity turntable inside a steel enclosure was then used to remotely cut these large pieces into smaller sizes of about 1-metre-square. Starting with the RPV lid, proceeding to the 500mm-thick RPV flange ring and the 140mm-thick RPV ring segments and finishing with the vessel bottom head, the remotely-operated robot cutting system demonstrated flexibility to cut any complex-shaped parts. In total, 430 tons of steel were segmented and packaged into 64 waste containers of 2-cubic-metre capacity each.

The same technique will be used at Barsebäck 2 as well as Oskarshamn 1 and 2.

Neckarwestheim project

At Neckarwestheim I, once the internals of the RPV had been disassembled by consortium partners GNS and Westinghouse, Uniper Anlagenservice and GNS installed the equipment for the segmentation and packaging of the vessel. This equipment included a ventilated enclosure, an auxiliary crane, a CCTV system, a thermal cutting system, a packaging station and other special tools and installations.

Lifting of the Neckarwestheim I RPV from its installation position (Image: Uniper)

Subsequently, after the segmentation and packaging equipment was installed and all necessary tests were successfully performed together with the client, an independent expert and the authorities, the RPV - with a mass of 235 tons, a height of 8.3 metres and a diameter of 5 metres - was removed from its installation position and lifted into the ventilated enclosure. Inside the enclosure, the flange ring was separated from the rest of the RPV by thermal cutting and transported to a segmentation area, which was equipped with a wire saw. In parallel to the wire sawing, the flange ring (with a wall thickness of up to 473mm at the segmentation area) and the RPV (with a wall thickness of up to 216mm) were thermally cut into segments inside the ventilated enclosure. In total, the RPV was cut into 102 segments with an individual mass of up to 8.2 tons each.

Lifting of the RPV into the cutting enclosure at Neckarwestheim I (Image: Uniper)

The RPV segments were transferred by a newly-erected auxiliary crane to a packaging station where the individual elements were placed into standardised steel sheet containers, which meet the requirement of the German Konrad repository.

The cutting process of the RPV at Neckarwestheim I (Image: Uniper)

As with the project in Sweden, the dismantling and packaging of the RPV at Neckarwestheim I was also successfully completed in December 2021.

A section of Neckarwestheim I's RPV is removed (Image: Uniper)

Researched and written by World Nuclear News