The outer safety dome has been installed on the containment building of unit 6 at the Fuqing nuclear power plant in China's Fujian province. The unit is the second of two demonstration Hualong One reactors under construction at the site.

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 inner steel dome - measuring almost 47 metres in diameter and over 23m in height, and weighing about 340 tonnes - was installed on the containment building of Fuqing 6 on 21 March 2018.

On 25 July, the outer steel dome - measuring about 53m in diameter and 13m in height, and weighing about 420 tonnes - was installed using a 3200-tonne crawler crane. The steel dome will now be covered with a concrete shell.

The Hualong One double-layer containment shell can withstand the impact of large aircraft, according to China National Nuclear Corporation (CNNC). The outer dome is "currently the largest shell structure of nuclear power plants under construction in the world", the company said. It has the characteristics of a large structural span, dense steel bars and high-strength concrete.

In November 2014, CNNC announced that the fifth and sixth units at Fuqing will use the domestically-developed Hualong One pressurised water reactor design, marking its first deployment. The company had previously expected to use the ACP1000 design for those units, but plans were revised in line with a re-organisation of the Chinese nuclear industry. China's State Council gave final approval for construction of Fuqing units 5 and 6 in April 2015.

The pouring of first concrete for Fuqing 5 began in May that year, marking the official start of construction of the unit. Construction of unit 6 began in December the same year. The inner dome of unit 5 was installed on the containment building in May 2017, with the outer dome installed in January 2018. Hot testing at Fuqing 5 was completed in March this year. Fuqing 5 and 6 are scheduled to be completed in 2020 and 2021, respectively.

Construction of two Hualong One (HPR1000) units is also under way at China General Nuclear's Fangchenggang plant in the Guangxi Autonomous Region. Those units are also expected to start up in 2022. Two HPR1000 units are under construction at Pakistan's Karachi nuclear power plant. Construction began on Karachi unit 2 in 2015 and unit 3 in 2016; the units are planned to enter commercial operation in 2021 and 2022. The HPR1000 has also been proposed for construction at Bradwell in the UK, where it is undergoing Generic Design Assessment.

"At present, China National Nuclear Corporation's five Hualong One units under construction at home and abroad are progressing in an orderly manner, and the safety and quality of the construction project are under good control," CNNC said.