The outer safety dome has been installed on the containment building of unit 2 at the Karachi nuclear power plant in Pakistan. The unit is the first of two Chinese-supplied Hualong One reactors being built at the site.

The outer dome in place at Karachi 2 (Image: CNNC)

The steel dome - measuring about 53 metres in diameter and over 23m in height, and weighing about 366 tonnes - was placed upon the top of the containment building walls at 8:06am yesterday, China National Nuclear Power (CNNP) has announced.

The Hualong One uses a double-layer safety shell design. Together with the inner protective dome, the outer dome protects the reactor and prevents the release of radioactive materials into the environment in the event of a serious accident.

"The successful hoisting of the outer safety dome has marked the end of the main structural project of the nuclear power plant, which has created favourable conditions for the overall test and thermal test of the subsequent containment," CNNP said.

Karachi 2 and 3 are the first export of China's Hualong One design, with construction of unit 2 beginning in 2015 and unit 3 in 2016. Installation of the reactor internals at unit 2 was completed in January this year. The units are scheduled for commercial operation in 2021 and 2022, respectively.

In addition to the two units under construction in Pakistan, four Hualong One units are being built in China. China National Nuclear Corporation is constructing two units at its Fuqing plant in Fujian province, while China General Nuclear (CGN) is building two at its Fangchenggang site in Guangxi province. All four units are expected to enter commercial operation in 2019-2020.

CGN proposes to use a UK version of its Hualong One design - the HPR1000 - at a prospective new nuclear power plant at Bradwell, England.