Cold test is not "cold" nuclear power plant "physical examination" first

Recently, the cold functional test of Fuqing No.5 unit, the world's first demonstration project of Hualong No.1, was successful once. As China's third generation nuclear power plant with completely independent intellectual property rights, "hualong-1" withstood the "high pressure" and passed a "big test" to test the unit performance. This indicates that the unit has broken the "Curse" of the first reactor, moved to the commissioning stage ahead of time and won the first step.




What is a cold test? Why did hualong-1 have a cold test? The reporter of science and technology daily interviewed relevant people.



Withstanding "high pressure", reactor performance withstanding "big test"



If the power station is compared to a huge power bank, "hualong-1" is a huge nuclear fuel power bank - "nuclear power bank".



Considering a nuclear power plant, one of the most important indicators is safety and reliability.



Cold test, short for cold functional test, is a large-scale comprehensive special commissioning test of nuclear power plant. Its main purpose is to verify the performance of primary system, equipment and auxiliary piping under high pressure, and carry out relevant tests of main system and auxiliary system under various pressure platforms. It is the first comprehensive "physical examination" of the whole reactor performance.



It is also considered as the first step to test this "nuclear power treasure", which can verify the integrity of each system, verify whether it can maintain pressure normally when it exceeds the design basis, and test its performance and compression resistance ability when it exceeds the design basis.



Whether the first reactor can advance on schedule, the "physical examination" report is very important.



Pressure is one of the first indexes to be examined in cold test. Our daily atmospheric pressure is 0.1 MPa, while the working pressure of the primary circuit of the nuclear power plant is 15.5 MPa. According to the design scheme, the design pressure of the primary circuit is about 17 MPa. But the peak value of this cold test is 22.3 MPa, which is equivalent to carrying the weight of 10 fully loaded cars on a large area of palm.



Relevant people of China Nuclear Power Group Fuqing nuclear power Co., Ltd. (hereinafter referred to as Fuqing nuclear power) explained that the so-called peak pressure can be understood as the value of 200 kilometers per hour displayed on the dashboard of some cars, taking the driving we usually contact as an example. The design pressure is like the car we usually drive, with the highest speed of 160 kilometers per hour. The working pressure of the primary circuit is 15.5 MPa, which is like the usual speed of driving, such as 120 kilometers per hour.



It is worth mentioning that the cold test pressure does not rise to 22.3 MPa in one step. From 10 a.m. to 2 a.m. the next day, after 16 hours of step-by-step pressure rise, the main system pressure of Fuqing No.5 unit of Hualong No.1 reached 22.3 MPa and stabilized for 10 minutes before it passed the test.



After the cold test, there will be a long hot test



From the literal understanding, some people will think that the cold test is cold. In fact, the temperature of the primary circuit in the cold test is 35-70 ℃.



How is water heated without nuclear fuel? According to relevant people, through blade stirring, the main pump rotates in the confined space, and the kinetic energy is converted into heat energy, which drives the primary circuit to heat up.



The construction of a nuclear power station has to go through several stages: preliminary preparation, civil construction, equipment installation and commissioning. After the cold test, there are hot test, critical test, power platform test and performance test.



The so-called cold test is relative to the hot performance test (referred to as hot test), it is also considered as the warm-up of hot test. After the cold test, the nuclear power plant is about to carry out the hot test.



Compared with the cold test temperature of 35-70 ℃, the hot test temperature is as high as 300 ℃.



Different from the cold test, during the hot test, the staff will simulate the actual operating conditions of the nuclear power plant as much as possible to verify whether the system performance is consistent with the design requirements, and further verify the reliability of the nuclear power plant, including ensuring that the equipment can not leak at room temperature and even more at high temperature. In addition, it is necessary to verify the reliability of instruments and equipment under high temperature, and check whether the measurement parameters such as temperature, pressure, flow, vibration and clearance meet the design value requirements.



In short, all those that may be affected by temperature should be checked, including normal temperature and high temperature. In addition, many functions and safety of the nuclear power plant should be verified, including the natural circulation capacity of the passive core cooling system and the heat exchange capacity of the passive preheating and discharging heat exchanger



Because of this, compared with the cold test, the subsequent hot test will be a relatively long process, it is not a test, but the sum of a series of tests.



It is understood that according to the different units, the hot test is less than a few days, more than a few months. During the hot test, the operation procedures of the nuclear power plant will be fully verified, the functions of the nuclear power plant will be fully checked, and the personnel engaged in the operation of the nuclear power plant will also be trained.



According to the plan, No. 5 unit of Fuqing nuclear power, the world's first reactor of hualong-1, will be loaded for the first time by the end of this year. According to the 62 month construction period, unit 5 is planned to be officially connected to the grid in July next year.



Big data and sand table deduction to realize risk control in advance



When the world's third-generation nuclear power units under construction fall into the "quagmire" of delay, since the commencement of May 7, 2015, "hualong-1" global first reactor demonstration project has been progressing smoothly, and it has become an important label to carry out the construction according to the planned schedule.



"Hualong-1 is a complex system engineering and an innovation process from scratch." Xing Ji, chief designer of CNNC's hualong-1 project, said that one of the key tasks of the demonstration project is to complete the construction drawing design of the first reactor project on schedule.



Through continuous promotion of "Internet plus", the CNNC has integrated the design and application software integration of nuclear power with the Internet technology, and established a remote integrated collaborative design platform. Many design units across the country have carried out collaborative design work on different platforms through network connection and various terminal devices. The number of collaborative design platform terminals reaches 500, and can be expanded according to the needs.



On this platform, nearly 1000 on-site engineers and designers of "hualong-1" have realized the timely communication and sharing of information, accelerated the transmission of design data, reduced the repetition of design exchange process, and effectively improved the design efficiency.



While carrying out the design work, CNNC makes full use of the efficient and convenient characteristics of the design information platform to timely summarize the technical problems encountered in the construction of the demonstration project to form big data in the design field, which not only feeds back to the equipment manufacturer and the engineering construction party, but also transmits to the follow-up nuclear power projects.



"This has laid a technical foundation for the standardized design and mass construction of hualong-1 nuclear power project, and improved the economy of construction and operation." Xing Ji said.



Starting from 300000 kW, "hualong-1" is the product of China's nuclear power R & D from introduction, absorption and re innovation. The design life of "hualong-1" is 60 years. The reactor adopts 177 core design, and the core adopts 18 months of refuelling. The utilization rate of the power plant can reach more than 90%. Among them, the independent intellectual property rights cover the design, fuel, equipment, construction, operation, maintenance and other fields, and have independently developed special software for nuclear power, forming a complete intellectual property system. It is the only third-generation model that can be independently exported in China at present. As the world's first demonstration project, the localization rate of Fuqing nuclear power unit 5 construction equipment is not less than 85%, and more than 100 sets of "three new" equipment are purchased and installed.



Chen Guocai, general manager of Fuqing nuclear power, told reporters that the continuously optimized project management mode and innovative project management mode ensured the steady progress of the demonstration project construction, and also provided valuable practical experience and reference basis for the subsequent batch construction of "hualong-1".



During the construction of the first reactor, the construction team used sand table for simulation for the first time in China. For example, six types of typical design organization and management tasks, such as power plant DCS funding planning, are selected in the design field for sand table deduction.



Chen Guocai said that by summarizing the basic facts, testing the management team's management knowledge, experience and problem-solving ability, and analyzing and predicting the phased development trend of the project, we can achieve the goal of prior management and risk control.