The upper section of the steel containment shell of China’s ACP100 (Linglong One) small modular reactor (SMR) demonstration project has been installed – 70 days ahead of schedule – at the Changjiang NPP the island province of Hainan, China National Nuclear Corporation (CNNC) said. The steel containment comprises a top head, an upper cylinder, a lower cylinder and a bottom head. It is an important safety barrier for the reactor ensuring the integrity and sealing of the reactor building.

The containment vessel bottom head was assembled on-site from 50 pre-fabricated steel plates and was lifted into place by crane onto the plant's concrete foundation plate in October 2021. The 450-ton lower section of the containment shell (15 metres high) was lowered onto the vessel bottom head in February, 46 days ahead of schedule. The 720-ton upper cylinder of the containment shell (also 15 metres high) is now in place on the lower cylinder.

CNN said that during the construction process, the installation of the ring-mounted rail-bearing beam on the upper cylinder of the steel containment was the most difficult part of the assembly. The ring-mounted rail-bearing beam was divided into 12 pieces, with a total weight of more than 120 tons, which required high precision and was difficult to weld. “The Hainan nuclear power small reactor project team optimised the welding logic, adopted measures such as supplying cold air to optimise the on-site welding environment, strengthened the welding quality process control, successfully completed the welding of the ring bearing beam.”

CNNC said the site uses an advanced construction method of factory manufacture and modular construction, which effectively reduces the site construction period. The project officially started in July 2021, with a planned total construction period of 58 months. “At present, the construction work of nuclear island and conventional island has been fully rolled out, and it is at the peak of civil construction. Five first-level milestone nodes have been completed, and the project construction is progressing smoothly,” CNN noted.

CNNC announced the launch of the SMR project at Changjiang in 2019. It had been under development since 2010 and the ACP100 preliminary design was completed in 2014. The major components of integrated pressurised water reactor’s (PWR’s) primary coolant circuit are installed within the reactor pressure vessel. In 2016, the design became the first SMR to pass a safety review by the International Atomic Energy Agency. The site already has two operating CNP600 PWRs and construction of the two Hualong One units began in March and December last year for commercial operation by the end of 2026. 

Image: The upper containment cylinder being hoisted into place at China’s ACP100 (Linglong One) SMR demonstration project (photo courtesy of CNNC)