Energized for the future
The recognised adaptability and reliability of BBR Prestressing Systems for the post-tensioning of nuclear power plant pressure and containment vessels has made them some of the best known internationally. The BBR team has now completed more then 60 nuclear energy projects in 15 countries.
Pioneering high capacity tendons
BBR engineers were pioneers in the development of high capacity tendons for nuclear applications. As early as the 1960s, they constructed a special facility at the tendon assembly plant in Switzerland to test the first generation of large tendons for nuclear power plants.
Contemporary nuclear vessel design
The basic structural design is generally a cylindrical vessel with flat end slabs or a convex dome. Practically all recent nuclear structures consist typically of two shells, the inner and the outer containment. Three types of BBR post-tensioning tendons are typically used in the inner containment and consist of three types:
- Vertical tendons for wall post-tensioning
- Horizontally looped tendons (hoop tendons)
- Cane shaped tendons.
Inspection and improvement work
For the continuous safety of service of large tendons, accurate measurement of the stressing force and regular controls are of great importance. For many years now, BBR Network Members have been carrying out lift-off tests.
All types of BBR VT CONA CMI anchorages can be equipped with the BBR WIGAring ELASTO force measuring system which allows for long term tensile force measurements with digital control, memory, Windows compatible data files and printing facilities.
Powerful and trusted technology
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Upgrading nuclear plants
BBR Network Member, KB Spennteknikk, has assisted with the replacement of steam generators at a nuclear plant in Sweden. This work required a large hole to be cut in the one meter thick secondary containment wall.
The BBR team removed both horizontal and vertical tendons before the cutting process – and destressed the wall on the opposite side to avoid unexpected forces developing in the wall – keeping it in balance – during the replacement work.
BBR corrosion protection
During the entire lifetime of the pressure vessels, the greatest attention must be paid to the protection of the prestressing steel from corrosion. The BBR Network uses three different types of corrosion protection for nuclear tendons:
- Cement grouted tendons
- Grease or wax grouted tendons
- Tendons protected with circulating dry air