Alloy 690 has excellent resistance to intergranular corrosion and intergranular stress corrosion cracking, and is mainly used for heat transfer tube materials of steam generators in pressurized water reactor nuclear power plants. The materials for heat transfer tubes of steam generators in pressurized water reactor nuclear power plants have undergone a development process, including 304 austenitic stainless steel, 600 alloy, 800 alloy and 690 alloy. The study of corrosion failure of 600 alloy in service shows that intergranular corrosion and intergranular stress corrosion cracking are the main problems. As a heat transfer tube material for steam generators in pressurized water reactor nuclear power plants, no reports of damage have been found since Alloy 690 was put into use in the 1990s.
Main applications
Among the pressurized water reactor nuclear power plant units that have been in operation in my country, only Qinshan Phase I uses Alloy 800, while Qinshan Phase II, Daya Bay and Ling’ao Nuclear Power Plants all use Alloy 690 as steam generator heat transfer tube materials. Most of the pressurized water reactor nuclear power plants under construction and planning also use Alloy 690 as steam generator heat transfer tube materials. However, the 690 alloy tubes used in the pressurized water reactor nuclear power plants that have been in operation in China are basically purchased from abroad. The main foreign companies that produce 690 alloy tubes are Valinox of France, Sandvik of Sweden and Sumitomo of Japan. The domestic companies that intend to produce and have already produced 690 alloy tubes are Jiuli Special Materials and Baoyin Special Steel Pipe Co., Ltd.
On the morning of September 25, in the general assembly workshop of Dongfang Electric (Guangzhou) Heavy Machinery Co., Ltd. in Huangge Town, Nansha District, Guangzhou, as Dongfang Heavy Machinery technicians slowly inserted Baosteel’s domestically made 690 alloy U-shaped tubes into the “heart” of the No. 1 steam generator of Fangchenggang Nuclear Power Unit 1, the first successful installation and application of nuclear power 690 alloy U-shaped tubes on Chinese nuclear power units since the localization of nuclear power. It marks the first time that the core of China’s nuclear power steam generators has appeared “made in China”.
