Jiangsu Nuclear Power Corporation said the 1,000-MW pressurised water reactor achieved first criticality at 08:20 local time on 27 July.
The milestone marked “the completion of the commissioning of the overall system and equipment of the unit, and the unit has officially entered a continuous and controllable nuclear operation state,” the company said.
Fuel loading at Tianwan-5 took place on 9 July, marking the first nuclear power unit under construction in China to accomplish fuel loading period this year.
Tianwan-5 is a domestically developed CNP-1000 design. It is seen as a Generation II+ design and a precursor to Generation III designs.
Another unit of the same design, Tianwan-6, is also under construction at the site.
Construction of Tianwan-5 began in December and of Tianwan-6 in September 2016.
There are also four Russia-procured VVER-1000 nuclear units in commercial operation at Tianwan.
Jiangsu Nuclear Power Corporation is a joint venture between China National Nuclear Corporation (50%), China Power Investment Corporation (30%) and Jiangsu Guoxin Group (20%).