Super module in place at Lufeng unit 1

With a hoisting weight of almost 990 tonnes and measuring more than 26 metres long, 29 metres wide and 23 metres high, the concrete and steel CA01 module - composed of 47 sub-modules - sits inside the unit's containment module where it will house the plant's reactor pressure vessel, steam generators and other components.

The installation of the CA01 module on 16 September marks "the entry of the unit into a new stage of structural construction and equipment installation", Shanghai Nuclear Engineering Research and Design Institute (SNERDI) said.

The CAP1000 reactor design - the Chinese version of Westinghouse's AP1000 - uses modular construction techniques, enabling large structural modules to be built at factories and then installed at the site. The CA01 module is referred to as a super module because it is too large to be transported by road and rail, and was constructed on site.

SNERDI - a subsidiary of State Power Investment Corporation - said the project team were faced with four major challenges in hoisting the CA01 module, which it describes as "the largest, heaviest, and most complex structural module in the nuclear island". These challenges were its complex structure, heavy weight, centre of gravity deviation, and millimetre-level positioning accuracy.

(Image: SNERDI)

"The project team achieved these breakthroughs through technological innovation and refined control," the company said. "Using laser scanning technology, the team created a full-scale digital replica of the module, accurately calculating the actual centre of gravity coordinates. Based on this information, they designed a dedicated multi-point hoisting system, equipped with a three-stage balance beam, to address the centre of gravity deviation caused by the module's T-shaped structure.

"By combining traditional contour line layout checks with 3D scanning collision checks, they were able to overcome the challenges of a confined installation area and minimal clearance from surrounding embedded components."

The first safety-related concrete was poured for the nuclear island of unit 1 at the Lufeng plant on 24 February this year. It is the third unit to begin construction at the site, which will eventually house six reactors.

The proposed construction of four 1250 MWe CAP1000 reactors (units 1-4) at the Lufeng site was approved by China's National Development and Reform Commission in September 2014. However, the construction of units 1 and 2 did not receive State Council approval until 19 August last year. Approval for units 3 and 4 is still pending.

In April 2022 the State Council approved construction of two Hualong One units at Lufeng as units 5 and 6. First concrete was poured for unit 5 on 8 September 2022 and that for unit 6 on 26 August 2023.