The ACP100 (Linglong One) SMR at the Changjiang Nuclear Power Plant in Hainan Province is the world's first land-based commercial SMR to progress to commissioning. Construction began July 13, 2021, with a planned 58-month construction period. Key 2025 milestones: all four main reactor coolant pumps installed (spring 2025); outer containment dome hoisted (February 2025); cold functional tests completed October 2025 (WNN October 16); non-nuclear turbine steam start-up test passed first attempt on December 23, 2025 (WNN January 8, 2026). CNNC is targeting commercial operation in the first half of 2026. The ACP100 is a 125 MWe integrated pressurised water reactor that became the first SMR to pass an IAEA safety review in 2016. The plant will produce enough power for 526,000 households and reduce CO2 by 880,000 tonnes annually. The Changjiang site already hosts two operating CNP600 PWRs and two Hualong One units under construction. Schedule update (October 2026): the H1 2026 commercial-operation target was missed. As of September 8, 2026 (World Nuclear News) the unit was still in pre-commissioning tests with no fuel load, criticality or grid connection reported, hot functional testing having been under way since March 2026. A project tracker cites early 2027 for commercial operation, which CNNC has not confirmed, and the projected date is set to mid-2027 accordingly. The neighbouring Changjiang unit 3 (a Hualong One, not the SMR) reached criticality on July 10, 2026 and connected to the grid on August 1, 2026. Update (October 7, 2026): NucNet reports, citing unconfirmed local media (China News Service) after a media visit to the Changjiang site by project company Hainan Nuclear Power, that hot functional testing is under way and that workers are aiming for fuel loading and grid connection before the end of 2026. Cold functional testing was completed in October 2025, and a CNNC official said in December 2025 that commercial operation was expected in the first half of 2026, which has not happened.