Workers weld piping at the Hualong One project in Karachi of Pakistan. [Photo/CNNC]

The main steam piping nuclear island at the Hualong One (HPR 1000) project was successfully weld bonded on Aug 28 in Karachi of Pakistan, marking the completion of the weld bonding for Hualong One's main steam piping and main water feed piping, officials said.

Hualong One is a third-generation nuclear power technology with completely independent intellectual property right in China.

It is a major landmark achievement of China's nuclear power innovation and development. Experts say it is of great significance for China's historic leap from a nuclear power to a great nuclear power.

At present, the domestic and foreign four Hualong One demonstration projects by CNNC -- as well the China National Nuclear Corporation -- are progressing in an orderly manner, officials said.

It is the only third-generation pressurized water reactor nuclear power project in the world to be constructed according to planning process.

The Karachi K-2/K-3 nuclear power project in Pakistan is an overseas demonstration project of Hualong One.

As the carbon steel piping system with the highest safety levels in a nuclear power plant, the main steam and main water feed pipes are the "main arteries" of the secondary loop of the plant, officials said.

There are 53 welding joints for the installation of main steam piping and 76 welding joints for the installation of main water feed pipes.

Because of the large pipe diameter and the thick walls of the pipes, they all have to be welded by hand. During welding, preheating before welding, temperature controls between welding layers, post welding heat treatment and other steps are required.

In order to complete the installation and welding of the main steam and main water feed piping with quality and quantity, the K-2/K-3 project department at CNNC organized professional and technical personnel.

The technicians analyzed technical difficulties, successively overcame many problems and completed the welding within 48 days, providing a strong guarantee for the realization of the cold test nodes of the K-2 unit, officials said.