In the early morning workshop, a steel behemoth weighing dozens of tons stood quietly, and the silver gray shielded motor casing shone coldly under the light. The workers are conducting their final inspection - this is not an ordinary industrial motor, it is the heart of a nuclear power plant and the only power source for circulating coolant in the reactor. Once it stops running, the consequences would be unimaginable. At this moment, it is about to depart from the workshop of Harbin Electric Power Group's dynamic installation company and head to Lianjiang, Guangdong.

The completion of the world's first domestically produced CAP1000 50Hz shielded motor main pump is the result of a decade long pursuit and breakthrough.

Crossing from 60Hz to 50Hz

The standard frequency of China's power grid is 50 Hz, while the CAP1000 nuclear power technology introduced earlier originated from the United States, with a design frequency of 60 Hz for its main pump motor. This is like installing an American engine into a domestic car - the speed is mismatched, the hydraulic performance is biased, the idle flow rate is not up to standard, and the entire system always has adaptation shortcomings.

Previously, the AP1000/CAP1000 units such as Sanmen and Haiyang that had been built in China relied on imported or imported technology for the production of their main pumps, all of which were 60 Hz versions. After completing the development of CAP1000 60Hz shielded motor and CAP1400 shielded motor, Harbin Electric Power Group's dynamic installation company has decided to start from scratch and actively develop a 50Hz version exclusively for the Chinese power grid.

The R&D team has reconstructed a complete set of electromagnetic design solutions, matching the 50 Hz rated speed from the root, and synchronously optimizing hydraulic performance and idle flow parameters. This breakthrough fills the gap both domestically and internationally, and also means that China's third-generation nuclear power main pump motors have truly achieved seamless integration with the Chinese power grid.

Breaking through the limit of insulation system

The working environment of shielded motors can be considered extreme. It is directly immersed in the reactor coolant, and the interior of the cavity is subjected to high temperature, high pressure, and high radiation conditions for a long time. The insulation material of ordinary motors will rapidly age and fail in such an environment.

The Harbin Electric team has developed a new high radiation tolerance and high temperature resistant 6 kV nuclear grade insulation system. This system can withstand the high temperature and radiation test inside the motor cavity for a long time, building an invisible defense line for the safe operation of nuclear power plants. At the same time, the team has finely optimized the internal flow field structure of the motor, effectively reducing hydraulic friction losses and synchronously improving motor efficiency - for every one percentage point increase in efficiency, the amount of electricity saved during the 60 year operation cycle of the nuclear power plant is extremely significant.

Step by step upgrade of precision control

One of the core components of shielded motors is water lubricated bearings. Its dimensional accuracy directly determines the operational stability of the motor rotor, and at a speed of thousands of revolutions per minute, even a slight deviation can cause vibration or even malfunction.

The Harbin Electric team has comprehensively refined and controlled the processing process, and specially added process internal control standards for key dimensions of water lubricated bearings, greatly improving the accuracy and dimensional consistency of components. In the assembly process of the upper thrust bearing, the team designed a brand new positioning fixture, which completely eliminates the deviation caused by traditional assembly methods and avoids the collision and damage of the guide bearing during the assembly process. The upgrading of each process ultimately leads to a steady improvement in the overall assembly quality of the machine.

The Guangdong Lianjiang Nuclear Power Phase I Project plans to construct two domestically produced CAP1000 third-generation passive pressurized water reactor units with a single capacity of 1.25 million kilowatts. The innovative use of seawater secondary circulation cooling scheme is committed to creating a new model of coordinated development between nuclear power development and coastal ecological protection. As an important demonstration project for China's third-generation nuclear power independent innovation and industrial chain upgrading, this project will inject strong momentum into the green, low-carbon and high-quality development of the Guangdong Hong Kong Macao Greater Bay Area.keywords:New energy information network

Next, Harbin Electric Power Group will focus on the strategic deployment of actively developing nuclear power in a safe and orderly manner, steadily promote the mass delivery of nuclear power equipment, and continue to upgrade the quality of China's nuclear power industry, laying a solid foundation for the construction of a new power system. The completion of this main pump, from catching up to running parallel, to leading in key areas, is another milestone on the road to China's nuclear power equipment self-reliance.Editor/Yang Meiling