Mammoet closes Chernobyl containment

Mammoet, working on behalf of Novarka, has successfully connected the two halves of the New Safe Confinement (NSC) structure at the Chernobyl Nuclear Power Plant in Ukraine.

The east and west halves of the arch were built in a decontaminated area away from reactor unit 4. With the two sections joined, the arch-shaped structure is now whole, ready to be placed over the existing sarcophagus which was built as emergency protection in the immediate aftermath and has a limited life span. Once the arch is placed over the reactor building it will provide a controlled, weatherproof environment and confinement for the solid radioactive remains of unit 4 for the next 100 years. This will allow a partial deconstruction of the old plant to be carried out in the future.

The east arch section, weighing 19,000t, was skidded to a waiting area in November 2014 to await completion of the second half of the arch. The east arch has a span of 260m, length of 80m and a height of 110m. While construction of the west arch neared completion, Mammoet started to prepare the east arch for connection.

In order to move and join the two halves of the arch, Mammoet developed and built a specially designed skidding system using a Teflon surface to slide the sections on. A total of 56 skidshoes, with a minimum capacity of 703t each, were used to move the east arch towards the west arch, which is currently on temporary supports.

The system was designed to be fully remote controlled. This is necessary in order for the operator to control the procedure to lift, shift and move the immense load into place over the sarcophagus from outside the contaminated location. The operation was executed on 23 July 2015 and was witnessed by the Dutch Ambassador in the Ukraine and his wife. It took no more than six hours to join both halves of the arch. The operation required extreme precision, with alignment tolerances of only 3mm.

The client, Novarka JV, is currently working on the tightening of approximately 1000 bolts to connect the two halves of the arch. When securely joined, the NSC will have a span of 260m, a height of 110m, a length of 165m and will weigh more than 35,000t.

The skidding of the NSC to its final position, over the original sarcophagus, is planned for Q4 2016. For this operation a total of 116 skidshoes will be required. It is estimated it will take about one week to skid the arch over a distance of 330m to cover Reactor Unit 4, completing this exceptional piece of engineering work.