China National Nuclear Corporation (CNNC) says the steel containment dome has been installed at the ACP-100 small modular reactor (SMR) demonstration project at the Changjiang NPP in Hainan Province. The multi-purpose, 125 MWe SMR (also known as Linglong One) is a pressurised water reactor designed for electricity generation, urban heating, urban cooling, industrial steam production, or seawater desalination.

The ACP100 reactor building comprises three parts: the internal structure, the steel containment shell and the outer concrete shielding shell. The steel containment shell consists of four parts: the bottom head, the lower cylinder, the upper cylinder and the top head. CNNC described it as “like an upright capsule that contains the internal structure of the reactor building”.

The containment vessel bottom head – which supports the steel containment shell – was assembled on-site from 50 pre-fabricated steel plates. This was installed on the plant’s concrete foundation plate in October 2021. The lower section of the 450-tonne containment shell – some 15 metres in height – was installed in February 2022, 46 days ahead of schedule. The following July the 720-tonne upper cylinder of the containment shell was installed.

“The key structures are now capped and the main period of internal installation has begun,” CNNC said. “This installation completed the final step of forming the steel containment vessel as a whole, providing a more complete and reliable protective barrier for the reactor core modules, internal components, voltage regulators and other important equipment that had been introduced in advance.”

CNNC noted that the modular and open-top construction method adopted for the Linglong One reduces construction costs and the construction cycle “through standardised design and batch manufacturing of individual modules”.

CNNC began development of the Linglong One in 2010, and it was the first SMR project to pass an independent safety assessment by International Atomic Energy Agency experts in 2016. Its integrated pressurised water reactor (PWR) design was completed in 2014 and it was identified as a key project in China’s 12th Five-Year Plan. The design, which has 57 fuel assemblies and integral steam generators, was developed from the larger ACP1000 PWR. It incorporates passive safety features and could be installed underground.

China’s state council approved the ACP100 Science & Technology Demonstration Project in 2021 and first concrete was poured in July that year. The lower section of the containment shell of was hoisted into place on in February 2022 and the last tank of concrete for the nuclear island’s underground retaining walls was poured the following August.

The project is owned by CNNC Hainan Nuclear Power Company, a subsidiary of China National Nuclear Power (CNNP – itself a subsidiary of CNNC). The projected start-up date is May 2025. Once completed, the project will produce enough power to meet the needs of 526,000 households, CNNC said.

There are already two operating CNP600 power units at the Changjiang site, and construction of the two Hualong One power units began in March and December 2021 for operation by the end of 2026.

Image: The dome being hoisted into place at Linglong One (courtesy of CNNC)