Inner dome installed at Zhangzhou 2

The steel dome - measuring 45 metres in diameter and almost 14 metres in height, and weighing about 260 tonnes - was raised by crane and placed on top of the walls of the double containment structure. An outer dome will subsequently be installed over the inner one.

CNNC said the dome has been installed ahead of scheduled. It noted that it achieved a 24-day reduction in the construction period for the hoisting of the inner dome Zhangzhou 2, compared with unit 1.

"The new record with the shortest construction period for the dome hoisting marks that the unit has fully shifted from the civil construction stage to the equipment installation stage, and the batch construction of Hualong One has taken a solid step," the company said.

The inner steel dome in place at Zhangzhou 2 (Image: CNNC)

CNNC said the installation of the dome is an important milestone in the construction of nuclear power projects. The dome is located on top of the nuclear island. Its main function is to ensure the integrity and leak tightness of the reactor building, and it plays a key role in the containment of radioactive substances.

Construction of Zhangzhou 1 began in October 2019, with that of unit 2 starting in September 2020.

CNNC has adopted the "open roof" method of construction for both Zhangzhou units 1 and 2, where a large crawler crane is used to lower the main equipment into the reactor building before the containment dome has been installed, rather than the traditional way of completing civil construction prior to installing the major components.

All three steam generators for Zhangzhou 2 were installed over a record five-day period, between 29 July and 2 August this year. The reactor pressure vessel was installed within the reactor building on 9 August.