How do they put 740 tons of "iron hats" on top of the nuclear island?, The Story of Chinese People: The Dome of the No. 3 Nuclear Power Unit in Xudabao is Hoisted and Placed in Xudabao | Nuclear Power | Dome
On July 25th at 05:06, the nuclear island dome of Unit 3 of the Xudabao Nuclear Power Project was successfully lifted into place. The steel safety shell is an important barrier for the reactor building, and its dome is an important component to ensure the integrity and sealing of the reactor building, which can prevent radioactive substances from escaping into the atmosphere under accident conditions. As a milestone node, the dome lifting marks the complete transition of the unit from the civil construction stage to the installation and commissioning stage. On site, the builders cheered and cheered for the moment of coronation. They had already forgotten to eat and slept, and worked together for hundreds of days and nights.
Dome hoisting site of Xudabao No.3 nuclear power unit. Provided by China National Nuclear Corporation
Through repeated trials and tribulations, overcome complex problems
It's easy to sew the lid tightly onto the mouth of the cup, but what kind of behemoth would it be if the lid were enlarged more than 400 times?
The lifting of the No. 3 nuclear island dome in the Xudabao nuclear power project has been optimized from the original design of lifting the ball belt and crown separately to a one-time lifting as a whole. The dome steel lining is a hemispherical structure with a diameter of 44 meters, equivalent to the length of 1.5 standard basketball courts, with a total height of 22 meters and a weight of approximately 240 tons. The dome lifting this time presents the characteristics of overall lifting, multiple items, total weight, and high accuracy, including steel lining structure and support cage, some steel bars and prestressed conduits, all penetrations, reinforcement plates, internal steel structures, equipment supports and hangers, sprinkler systems, lighting systems, hydrogen dissipation devices, heat exchanger equipment, detection equipment, and other equipment. At the same time, the platform and channels required for the construction of the dome lifting are set up in advance outside the dome, providing favorable conditions for continuous construction after lifting. The overall weight is as high as 740 tons, equivalent to lifting 490 cars.
"The process of lifting the dome is like putting a lid on a cup, ultimately ensuring its airtightness. However, as weight, volume, and height increase, the difficulty of covering the 'lid' also increases." said Wang Nan, Deputy Manager of the Engineering Management Department of the Xudabao Project Department of CNNC. Moreover, due to the proximity of the project to the seaside, during the lifting process, it is also necessary to consider the complex climate conditions at the seaside. "One week before lifting, we will combine weather forecasts and wind speed monitoring to compare the patterns of weather changes and choose the most suitable lifting time. A slight breeze can bring unpredictable changes to the lifting work," said Wang Nan.
Three days before the official lifting, the first trial lifting of the nuclear island dome of Unit 3 of the Xudabao Nuclear Power Project was carried out. According to the safety configuration and system design requirements of nuclear power plants, a large number of safety facilities such as HVAC equipment, electrical and instrumentation equipment, process pipelines, and corresponding supports are usually arranged on the inside of the dome. For safety configuration purposes, these safety facilities are not evenly distributed on the inside of the dome. Therefore, it is crucial to complete the counterweight and adjust the center of gravity of the entire dome lifting unit before lifting the dome. The first trial lifting requires checking whether the counterweight is appropriate and providing experience preparation for formal lifting.
"We carried out the counterweight according to the pre planned plan, and during the first trial lifting, we found that the side with the counterweight added had a larger deviation than the one we had calculated beforehand. We need to remove the counterweight and try lifting again," said Song Zhiyong, Deputy Director of the Civil Engineering Department of Liaoning Nuclear Power Engineering Management Office.
During the process of dismantling the counterweight, heaven is not beautiful. On July 22, Xingcheng City, Huludao City, Liaoning Province issued a red warning for rainstorm, and the precipitation in Xudabao Town within one hour reached 75.9mm, breaking the historical peak. In the memory of Yang Lidong, the captain of the Nuclear Island First Team of the Xudabao Project Department of China National Nuclear Corporation, this was the biggest rain in Xingcheng in recent years.
As the overall commander of the on-site engineering team, Yang Lidong was very anxious in his heart. According to meteorological predictions and expert analysis, the best weather conditions were in the early morning of the 25th, making it the best time for hoisting. To reverse the progress, it is necessary to complete the trial lifting work step by step a few days before lifting, and eliminate all possible problems.
The accumulated water on site needs to be drained into the sea, and the dome needs to be re discussed, calculated, and adjusted with technical experts. Many problems need to be solved before the rain stops. It is already late at night, but everyone's hearts are hanging on the project site.
Finally, on the afternoon of July 23rd, the rain stopped. At this time, Yang Lidong stayed up all night, but the trial lifting work was not yet finished. He raced against time to organize the workers of the nuclear island team and steel structure team to dismantle the counterweight, learn from experience, and prepare for the second trial lifting.
Skilled in every inch, helping to successfully "crown"
The project team ultimately chose to lift the dome during the formal lifting phase at a speed of 0.4 meters per second. "To ensure overall safety and controllability, the slower the speed, the more stable it becomes," said Wang Nan. The heavy "big hat" has changed the previous method of lifting the crown and belt separately, challenging the overall one-time lifting, and the hook position requires an angle deviation of ± 3 millimeters. Wang Nan told reporters, "It is necessary to overcome the problem of slight deformation of the dome during the lifting and lowering process. In order to ensure accurate radial and horizontal alignment, we have arranged 36 support columns and jacks in a circular shape below the dome. Multiple workers distributed in various directions below the dome measure and slowly adjust the jacks in real-time, until the bottom of the dome completely fits the jacks."
At the Xu Dabao Nuclear Power Project site, there stands a blue "big guy", which is the 2600T crawler crane known as the "Blue Giant" by workers. This big guy looks bulky, and it's not an easy task to operate. Lifting the dome with the "Blue Giant" requires three operators to work together.
Dome hoisting site of Xudabao No.3 nuclear power unit. Provided by China National Nuclear Corporation
Wang Long is the commander of the 2600T crawler crane in the Xudabao Nuclear Power Lifting Project Department of CNNC Machinery Engineering. On the early morning of July 25th, before lifting, Wang Long arrived early in the operation room and checked the equipment over and over again. Under the command of the on-site commander, a 2600 ton crawler crane slowly lifted the dome off the ground. In the control room, Wang Long stared closely at the display screen and operated the lever with both hands. The 2600 ton "Steel Giant" slowly lifted the 740 ton dome dome crown off the ground, and after a series of difficult actions such as lifting, lifting, variable amplitude, rotation, walking, lowering, and lowering the hook, the dome slowly and steadily dropped onto the safety shell, ensuring safety, order, and controllability. "Every lifting is like going to the battlefield, it's a test of oneself. Don't underestimate this operating rod. It lifts more than just a piece of equipment or a module, and every successful lifting and precise hook drop carries the common expectations of all builders of the Xudabao Nuclear Power Project," said Wang Long.
Jiang Qian, the lifting engineer who cooperated with Wang Long, also breathed a sigh of relief. From participating in the global first reactor demonstration project of "Hualong 1" to rushing to the site of the Xudabao nuclear power project, in order to better devote himself to work, he moved with his wife and children from his hometown to Fuqing, and then traveled to Xudabao. In the process of promoting modular innovation in the construction of Xudabao Nuclear Power Project, Jiang Qian will analyze the positioning points of the large crane, equipment assembly site layout, and the lifting work plan of the large crane together with everyone in each construction plan review meeting. At the lifting operation site, he always actively organizes team members to measure wind speed, establish lifting warning areas, and inspect equipment lifting positions. "To laypeople, lifting operations may seem like a rough job, but for lifting engineers, the essence of this job lies in the 'coarse to fine' approach." Jiang Qian said.
The nearly three-hour lifting operation requires the coordination of hands, eyes, and brain, requiring a high level of mental concentration. After the lifting was completed, Wang Long walked out of the control room and moved his hands, which were somewhat stiff from maintaining the same position for a long time. He watched the crane drive to the designated location, watched the staff clean up the scene, and breathed a long sigh of relief as the team members left. "Today's lifting task has been safely completed," he said.
"At the moment when the lifting was completed and the crane sounded its horn, the sound of the horn seemed to hit my heart," Yang Lidong said. "Everyone in the team was fully committed and everyone put in a lot of effort."
On the way back to the rest room from the project site, Shi Zhiyan, the director of the technical department of the Xudabao project at CNNC Er'er, met Jiang Qian. The two passersby were still discussing the lifting process and how to refine the lifting plan in the future. "It's amazing, everyone stayed up all night, but everyone was in a very excited state, as if the work was not over yet. Hoisting is just an iconic milestone, and there are even more challenging tasks waiting for us to do our best," said Shi Zhiyan.
Overcoming severe cold and building the highest latitude nuclear power plant in China
As the northernmost nuclear power plant in China, due to its location in extremely cold areas, the temperature can drop to minus 20 degrees Celsius during winter. Since the start of construction for two years, the winter construction period has reached 221 days. In order to overcome the dual challenges of quality and progress brought by winter construction, all parties involved in the construction have braved severe cold and wind and snow, and have been competing with adverse weather since the beginning of the project construction. They have organized winter construction seminars and drills multiple times.
"On the one hand, we have innovatively carried out research and application of winter construction techniques, methods, and tools, compiled the" Winter Construction Standard Atlas of Nuclear Power Engineering ", and achieved standardization of winter construction. On the other hand, we have promoted the automation application, factory prefabrication, assembly application, and modular construction of engineering construction. For example, in terms of automation, for the first time, friction welding and other technologies have been widely used, successfully solving the problems of large welding volume, low efficiency, and high human quality risks. In modular construction, we promote the" model to model "approach, reduce cross operations, reduce safety risks, and improve installation quality." Shi Zhiyan said.
After the completion of Units 3 and 4 of the Xudabao Nuclear Power Project, it is expected to provide over 16 billion kilowatt hours of clean electricity annually, which is equivalent to saving 5.7 million tons of coal annually and reducing carbon dioxide emissions by 16.8 million tons annually. This has a positive effect on ensuring energy security and optimizing energy structure in China.
