The hard "core" force behind zero-carbon heating

In November 2021, the second phase of the "Warm Nuclear No. 1" project was put into operation, allowing Haiyang urban area to achieve a "seamless switch" from traditional coal-fired heating to nuclear clean heating, becoming the first city in China to achieve "zero carbon" heating. Haiyang Nuclear Power Unit 1 has become the world's largest cogeneration unit, and "warm core No. 1" has become one of the projects that earlier realized the requirements of the national "14th Five-Year Plan" on "carrying out demonstration of comprehensive utilization of nuclear energy such as Haiyang in Shandong Province".

According to reports, in July this year, the "warm core No. 1" 900 MW long-distance trans-regional nuclear energy heating project officially started, is expected to be put into operation in 2023. By then, the heating area can reach Yantai and Weihai areas, which can meet the heating needs of 1 million people.

Only heat transfer, no medium exchange

The multi-loop isolation design makes nuclear heating safer

In fact, at the beginning when I heard that the heating source of the community would change from burning coal to nuclear energy of the nuclear power plant, many local residents also had concerns. However, after looking deeper, they were reassured.

"Nuclear heating is not nuclear heating." Zhang Zhen told reporters that the heat extracted from the nuclear power unit is only a heat source, and it is necessary to pass a number of "boiling water" links in order to transfer the heat to the user through the municipal heating pipe network.

He and his colleagues often use the term "self-heating hotpot" to explain how nuclear heating works. "Self-heating hot pot" below is the heating layer, above is the food layer, after physical isolation, the following as the inedible part of the heating material, only play a heating role, and will not be in contact with the above ingredients.

"The key here is that there is only heat transfer, no medium exchange, nuclear heating is the same." Zhang Zhen introduced that the entire process of Haiyang nuclear heating is actually achieved through five physically isolated circuits.

The reporter learned that the primary circuit is completely closed in the reactor building. In the reactor, more than 150 fuel assemblies undergo nuclear fission reactions, releasing a large amount of heat, which will heat the high-pressure water in the primary circuit to more than 300 degrees Celsius.

Through the steam generator, the water in the second circuit absorbs the heat of the high pressure and high temperature water in the primary circuit, becomes saturated steam, and pushes the turbine to do work and generate electricity. Nuclear heating is to extract part of the overpowered steam from the second circuit of the nuclear power unit as a heat source, and heat the water in the third circuit through the first station of heat exchange in the plant.

"It's the equivalent of heating water with high-temperature steam in physical isolation." Zhang Zhen explained that the hot water of the three circuits heats the water of the four circuits in the heat exchange station of the heating enterprise outside the plant, completing the heat exchange of "water and water", and such an operation can continue to the five circuits or even more. The final output of water becomes the "heating water" that is transmitted to the residents' homes.

"In simple terms, nuclear heating is the transfer of heat through water. There are only two modes of heating water with steam or heating cold water with hot water." Zhang Zhen said that a number of circuits are set up between the nuclear power plant and the user for physical isolation, each loop only the transfer of heat, no water exchange, and at the user end, the hot water is only closed in the cell cycle, "very safe."

The data speaks for itself. The Shandong nuclear power plant provided the reporter with the radiation protection engineer's previous detection data on the radiation level of each circuit: The heat exchange station located in the nuclear power plant, where the steam is the first heat exchange, the measuring instrument showed the radiation dose of about 0.23 microsieverts per hour; In the office building of a nuclear power plant that uses nuclear heating, the measuring instrument shows 0.18 microsieverts per hour; The first nuclear heating station of the thermal company, the measuring instrument shows 0.18 microsieverts per hour; In a residential home with nuclear heating, the measuring instrument shows 0.20 microsieverts per hour...

"Radiation is everywhere in nature. Cosmic rays, soil, rocks, etc., all have a certain level of radioactivity, indoor tiles, marble, etc., will also produce radiation, through data testing, we can see that nuclear heating will not introduce additional radiation. According to statistics, the annual dose of natural radiation received by the average person in the world is 2,400 microsieverts, which is called the natural background level." According to professionals in the field of environmental monitoring, whether it is natural background radiation, or the radiation we are exposed to in our daily life, as long as it is controlled within a certain amount, it will not affect our health.