Installation has begun of the domed part of the inner containment (VZO) at unit 2 of the Rooppur NPP under construction in Bangladesh. Installation of the first of the three tiers of the inner containment dome has been completed, general contractor ASE said. Large-sized structure weighing 195 tons and with a diameter of 42.8 metres was installed at a height of 44.1 metres.

“Installation of the VZO dome is not only technologically complex, but also one of the most spectacular stages in the construction of the reactor unit. When all three tiers of the dome are installed, this will pave the way for installation of the reactor pressure vessel,” said Alexei Deriy, Vice President of JSC ASE and Director of the project for the construction of Rooppur NPP.

The assembly and installation of the VZO dome is carried out by specialists from Trest RosSEM (part of the Engineering Division of Rosatom). The lifting was carried out using a Liebherr LR11350 crane (capacity – 1350 tons) and took about 4.5 hours. Pre-assembly of all three tiers of the VZO dome lasted 151 days, from the end of September to the beginning of March. For comparison, the same process at unit 1 took 207 days. It was possible to reduce the time by almost two months by using the experience gained.

The Rooppur plant is being built by Rosatom on the eastern bank of the Ganges River in Bangladesh’s Pabna district about 160 km northwest of the capital city of Dhaka. It will comprise two VVER-1200 reactors: Rooppur 1 is scheduled to start operating 2023, followed by Rooppur 2 in 2024.

Also at Rooppur 2, specialists from Energospetsmontazh (part of the Engineering Division of Rosatom) completed the installation of an emergency core cooling system (ECCS). “The installation of all four ECCS tanks in their regular places is a large-scale and labour-intensive process that requires the highest professionalism from specialists,” said Deriy. The hydraulic tank is a high-pressure vessel located vertically. The weight of each is about 80 tons, and the volume is 60 cubic metres.”

The ECCS consists of passive and active parts. Hydraulic tanks are passive NPP safety systems that operate without the involvement of personnel and the use of external power supply sources. During the operation of the power unit, these tanks store an aqueous solution of boric acid (neutron absorber), intended for emergency flooding of the reactor core in case of emergency situations associated with loss of coolant, in order to prevent damage to fuel elements and fuel melt.

Image: Installation of the inner containment dome at Rooppur 2 (photo courtesy of Rosatom)