Petrozavodsk branch of AEM-Technologies, JSC (a member of Atomenergomash, machine engineering division of Rosatom State Corporation, and Karelian Regional Branch of the Russian Engineering Union) has started to assemble pipe spools of reactor coolant pipeline (RCP) for power unit No. 7 of Tianwan NPS under construction in China.
A cladding coating was preliminarily applied to the inner surface of the forged pipes by electroslag welding. 36 pipe blanks to be afterwards assembled into 16 RCP spools, as well as sets of rings for welding procedure and welders qualification on site are overlaid for one power unit.
The pipe spools are both straight sections of the pipeline, and couplings of straight pipes with elbowed bends. The first pipe-to-bend circular welds have been performed for RCP components for the seventh unit of Tianwan NPS. The weld joints have successfully passed the required inspection operations, including radiographic test.
Besides, Petrozavodskmash has completed the manufacture of RCP clad pipe blanks for another Chinese nuclear power station - Xudapu NPS, power unit No. 3. The blanks have also been transferred for further assembly of pipe spools.
With an internal diameter of 850 mm and a total length of 146 meters, RCP connects the main equipment of the NPP primary circuit: the reactor, steam generators and reactor coolant pumps. It is designed for circulation of the primary coolant at temperatures up to 330 degrees Celsius under high pressure - 160 atmospheres. In order to protect the pipeline from the aggressive effects of the coolant, an anti-corrosive coating is applied to the inner surface of the forged blanks. It bears reminding that Petrozavodskmash was the first in Russia to master the manufacturing process of seamless clad pipes for nuclear power plants.
Tianwan NPS is located in Jiangsu Province, PRC. The first power units No. 1 and No. 2 with VVER-1000 reactors were accepted by the customer and put into warranty period operation in 2007. Units No. 3 and No. 4 were put into warranty period operation in 2018. In the same year, the intergovernmental protocol and framework contract for the construction of power units No. 7 and No. 8 of Tianwan NPS with VVER-1200 reactors relating to the latest generation “3+” were signed.
Xudapu NPS is located in Liaoning Province, Northeast China. Power units No. 3 and No. 4 are being built according to NPP-2006 project and comply with the current safety requirements of IAEA. Design and construction of the main equipment is carried out by the Engineering Division of Rosatom State Corporation.