MOVING MASS | DECOMMISSIONING
Far left: At Lingen the steam converters had to be tilted before they could be lifted from the building
Left:
Specialist lifting tools like strand jacks are required for the nuclear sector
checks before being brought into the control area. This considerable time factor had to be taken into account in the planning so that the overall deadline could still be met. Prior to execution, all core components including the support strap, temporary lifting device and the skidding beam for the transverse skidding operation were subjected to a thorough load test. After successful acceptance by the authorities, work could begin in the control area. First, the support strap had to be installed onto the first
steam converter. Due to its installation position in a narrow housing, the upright-positioned component was difficult to access and first had to be jacked up with hydraulic climbing jacks and moved laterally. After the support strap was attached, the temporary lifting device took over the steam converter. It was pushed out of the housing centimetre by centimetre with a skidding device and finally placed precisely onto a skidding track. The now horizontal steam converter was then rotated by 90 degrees and lowered. After removal, the steam converter was lifted from this
portal gantry in a tandem operation, with a 1200-tonne and a 750-tonne mobile crane, and loaded for transport on the power plant site. The second steam converter followed the same procedure.
In this position, the large component could be removed
from the control area to a gantry built several stories high against the building exterior. Due to interfering edges and the narrow diameter of the opening, only a few centimetres of clearance were available to perform the operation.
Bringing new, more efficient thinking Although the nuclear industry has its own specific demands and stringent standards that must be respected, it is also important to remember that many of the logistical challenges this sector faces are in many ways similar to those found in the wider energy sector or in civil engineering projects. The danger to the nuclear industry is if a wide variety of opinion is not sought. This approach limits the range of potential experience available. In that case there will be a lower chance of finding new, more efficient solutions that may have been developed in other industries and can be adapted to meet the specialist demands of the nuclear sector. There might be a potential for cross-application, for example, in sectors where a particular methodology or piece of equipment may not be the norm.
A good example of this comes from the installation of the new sarcophagus at Chornobyl, where the original emergency shelter covering the reactor needed to be replaced with a more permanent solution. The scale of this task was huge – requiring the construction and installation of a shelter weighing nearly 35,000 tonnes, which would be the largest land-based movable structure ever built. Putting this into perspective, at 165 metres long, 260 metres wide, and 110 metres tall the structure is big enough to completely house Notre Dame Cathedral in Paris. An innovative approach and tailor-made equipment were needed to deal with such size and weight and deliver it with millimetre precision. To provide a clean and safe working area, the
construction site was located some 330 meters from the reactor and a new foundation was laid. It allowed personnel to work continuously and save construction time. To complete the project as safely and efficiently as possible a lifting system and software to control up to 60 strand jacks simultaneously and a skidding system consisting of 116 skid shoes with a capacity of 703 tonnes each was developed. With both sides of the skidding system 260 metres apart, the movement was fully monitored, controlled, and synchronised. Each half of the arch was lifted in three stages, allowing the crew to work at lower heights. At each stage, elements were added before raising the arch further. Once the first half was raised, it was skidded away to make room for the assembly of the second half. Upon completion, the first one was skidded back to the construction area where both halves were connected to finalise the construction. This approach had many advantages. Alongside the efficiency and safety benefits of reduced working at height, only half the jacking capacity was needed compared to raising the arch in one piece, greatly reducing costs. Last, but not least, remotely-operated equipment prevented the crew from having to work in the contaminated area, making this project a textbook example of safe, efficient, and out- of-the-box engineering. The nuclear industry is facing a time of change as
it scales up to play an even bigger role in the energy transition. With decommissioning and maintenance work on the increase, it’s important that we make the most of the expertise – in both engineered heavy lifting and across other disciplines – to ensure these challenging projects can be completed as safely and promptly as possible. ■
www.neimagazine.com | May 2023 | 35
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49
