Cold hydraulic testing has been completed on the primary and secondary circuits of Unit 1 of the Sanao nuclear power station in the eastern Chinese province of Zhejiang, the China Nuclear Energy Association (CNEA) said.

During cold testing the reactor coolant system was filled with water and pressurised above normal operating conditions, then lowered to normal design pressure while inspections took place to verify systems met design standards. This included checking that welds, joint pipes and other components did not leak under pressure.

CNEA said the completion of cold testing marks the full transition of the nuclear power unit from the installation stage to the commissioning stage.

Sanao, also known as Sanaocun or Zhejiang Sanao, has two domestic 1,117-MW Hualong One units under construction. Construction of Sanaocun-1 began in December 2020 and Sanaocun-2 a year later.

The Hualong One, or HPR1000, is an indigenous pressurised water reactor unit that incorporates elements of China National Nuclear Corporation’s ACP1000 and China General Nuclear’s ACPR1000+ reactor designs.

It is Beijing’s domestic flagship reactor technology, with 17 of the 28 reactor units under construction in China being of the Hualong One design. There are also two Hualong One plants in operation outside China, both at the Kanupp nuclear station in in Pakistan.