Unit 4 of the Tianwan nuclear power plant in China's Jiangsu province has entered commercial operation after completing demonstration operation at nominal capacity for 100 hours.

The control room of Tianwan 4, pictured at the very moment it entered commercial operation (Image: Rosatom)

Tianwan Phase I - units 1 and 2 - was constructed under a 1992 cooperation agreement between China and Russia. First concrete was poured in October 1999, and the units were commissioned in June 2007 and September 2007, respectively.

Tianwan Phase II - units 3 and 4 - are similar to the first stage of the Tianwan plant, comprising two AES-91 VVER-1000 units designed by Gidropress and supplied by Russian state nuclear corporation Rosatom. First concrete for unit 3 was poured in December 2012, while construction of the fourth unit began in September 2013. Unit 3 achieved first criticality on 29 September last year and was connected to the grid on 30 December. That unit entered commercial operation on 15 February.

The loading of a total of 163 fuel assemblies into the core of unit 4 was started on 25 August and completed on 2 September. The reactor achieved first criticality on 30 September. Dynamic tests have since been performed on the reactor at 25%, 50%, 75% and 100% of capacity.

The demonstration test run of the reactor at nominal capacity for 100 hours was completed at 3:17am on 22 December, China National Nuclear Corporation (CNNC) has announced. Rosatom said the commissioning stage of Tianwan 4's nuclear island had been successfully completed.

"All tests stipulated by the commissioning programme for Tianwan units 3 and 4 have been conducted," it noted. "The tests have proved the nuclear island complies with the technical specifications and safety requirements set forth in the contract."

The Russian company said electricity generated by the unit is now being supplied to the Chinese grid at a fixed price set by the authorities.

Rosatom said, "The near future will see the signing of a preliminary acceptance certificate for the Tianwan unit 4 nuclear island based on the conducted tests in accordance with the general contract for units 3 and 4 of the Tianwan plant made by and between AtomStroyExport (part of Rosatom's engineering division) as the Russian General Contractor and Jiangsu Nuclear Power Corporation."

Alexey Bannik, ASE Group's director of projects in China, noted: "This means that a two-year warranty period for the plant operation has commenced, and once expired the unit will ultimately be handed over to the Chinese party. We can confidently state that the second stage of the Tianwan nuclear power plant has been built fully on schedule and it is evidenced by this important event."

CNNC said it now has 21 nuclear power reactors in operation, with an installed generating capacity of 19.092 GWe. It expects power generation from those units to exceed 110 TWh by the end of this year. The company currently has a further four units under construction, which will add a further 4.496 GWe of capacity.

Construction of Tianwan Phase III - units 5 and 6 - was originally scheduled to start in early 2011. However, following the March 2011 accident at Japan's Fukushima Daiichi plant, the Chinese government suspended the approval of new nuclear power projects, including those two units.

The latest Five-Year Plan called for construction of Phase III of the Tianwan plant to be accelerated. China's State Council gave its approval for Tianwan units 5 and 6 - both featuring 1080 MWe ACPR1000 reactors - on 16 December 2015. First safety-related concrete was poured for unit 5 in December 2015, with that for unit 6 poured in September 2016. CNNC plans to put both units 5 and 6 into commercial operation by the end of 2021.

On 8 June, Russia and China signed four agreements, including for the construction of two VVER-1200 reactors as units 7 and 8 of the Tianwan plant. In addition, two VVER-1200 units are to be constructed at the new Xudabao site in Liaoning province. Contracts for Tianwan 7 and 8 were signed between CNNC and Rosatom in early November.