1. 1 Overview of nuclear power principle: fission chain reaction generates energy and steam drives steam turbines to generate electricity.
Nuclear energy releases energy from the nucleus through nuclear fission, nuclear fusion and nuclear decay, in which nuclear fission chain reaction is the principle of nuclear power generation.
Nuclear power generation mainly uses the nuclei of larger atoms (such as uranium, thorium and plutonium) to split into multiple smaller nuclei after absorbing a neutron, and at the same time release two or three neutrons and huge energy. The released neutrons and energy will cause nuclear fission of other atoms, so that the process of releasing energy will continue. This series of reactions is called nuclear fission chain reaction. Nuclear fission chain reaction is the energy source of nuclear power generation.
Nuclear power plant makes the energy generated by nuclear fission chain reaction complete the transformation of nuclear energy, thermal energy, mechanical energy and electrical energy, thus achieving the purpose of generating electricity.
Nuclear power plants can be roughly divided into nuclear island part (NI) and conventional island part (CI):
Nuclear island part: The nuclear island part includes reactor device and primary system, which is mainly used for nuclear fission reaction and steam generation.
The function of nuclear island reactor is to produce nuclear fission and convert the energy released during fission into heat energy of water; After absorbing heat energy, water enters the U-shaped tube of the steam generator along the pipeline in the form of high temperature and high pressure, and transfers heat to the water outside the U-shaped tube, so that the water outside becomes saturated steam; The cooled water will be pumped back to the reactor by the main pump for reheating, forming a closed heat-absorbing and heat-releasing circulation loop with water as the carrier, which is called the primary loop, also known as the "steam supply system".
Conventional island part: The conventional island part includes a steam turbine generator system and a secondary loop system, and its main function is to use steam to drive the steam turbine unit to generate electricity.
The steam generated by partial heat transfer in the nuclear island will enter the steam turbine in the conventional island, and the thermal energy of the steam will be converted into mechanical energy of the steam turbine, and then the mechanical energy will be converted into electrical energy through the rotor connected to the generator, thus completing the power generation process.
At the same time, the steam (exhaust steam) doing work is discharged into the condenser, cooled by circulating cooling water, condensed into water, then sent to the heater for preheating by the condensate pump, and finally sent to the steam generator by the feed pump, forming another closed circulation system with water as the carrier, which is called "secondary loop".
In principle, the secondary loop system is basically the same as the steam power loop of conventional thermal power plants.
1.2 nuclear power business model: asset-heavy model+cash cow in operation period.
The business model of nuclear power presents the characteristics of "asset-oriented model+cash cow in operation period";
Construction period: the construction period is long and the investment is large.
Due to the general delay, the actual construction period of the nuclear power plant is about 5- 10 years. The design cycle of nuclear power plants is usually five years, but due to lack of construction experience, design changes, time-consuming testing and other reasons, the delay of the first reactor of nuclear power units is widespread in China, which leads to the increase of interest expenses and power generation costs during construction.
Mass production is conducive to shortening the construction period and reducing the cost of nuclear power units. After batch construction, the construction period of m 3 10/ CPR equivalent vehicle series can be gradually stabilized at about 5 years.
The investment per kilowatt of the third generation nuclear power in China is about 15000 yuan.
On the basis of AP 1000, the construction cost of the third generation nuclear power technology CAP 1000 is 14000 yuan /kW, and the construction cost of Hualong No.1, which belongs to the third generation nuclear power technology, is 17390 yuan /kW. Based on this calculation, the corresponding investment of million kilowatt nuclear power units is about 654.38+0.5 billion yuan, showing the characteristics of large investment.
Operation period: a stable cash cow
Similar to the hydropower industry, the nuclear power industry has the characteristics of a stable cash cow during the operation period.
The nuclear power plant follows the split formula of operating income = electricity price * on-grid power = electricity price * installed capacity * utilization hours *( 1- auxiliary power consumption rate), and the operating income is highly certain. At the same time, due to the large investment in the early stage of the project, the depreciation cost of fixed assets is high (accounting for 30-40% of the main business cost), and the non-cash cost (depreciation) accounts for a relatively high proportion in the cost of nuclear power plants.
Therefore, once the nuclear power plant enters the operation period, it will show the characteristics of obtaining stable and abundant operating net cash flow.
1.3 low-carbon and high-efficiency base-load power supply is of great significance under the goal of "double carbon"
Nuclear power has the characteristics of low carbon and high efficiency, and the proportion of nuclear power in China is obviously lower than the global level.
Compared with other power generation methods, nuclear power has the characteristics of high utilization hours, low power cost, low carbon, stability and high efficiency, and is suitable for development as a high-quality base load power supply.
From the perspective of power supply structure, the proportion of nuclear power in China is only 4.80% in 2020, which is not only lower than the 64.53% of France, a big country in nuclear energy utilization, but also significantly lower than the global average of 9.52%. There is still much room for improvement in the proportion of nuclear power in China.
Under the goal of "double carbon", the proportion of non-fossil energy has increased, and the importance of nuclear energy has become prominent.
June 5438+February 2020 Climate Ambition Summit: By 2030, carbon dioxide emissions per unit of GDP will be reduced by more than 65% compared with 2005, and non-fossil energy will account for about 25% of primary energy.
202 1, 10 year124 October, the Opinions of the Central Committee of the State Council on Comprehensively, Accurately and Comprehensively Implementing the New Development Concept and Doing a Good Job of Carbon Neutralization in the Peak Carbon Dioxide Emission put forward that it is necessary to "actively develop non-fossil energy", "implement renewable energy substitution action", "continuously increase the proportion of non-fossil energy consumption" and "actively, safely and orderly develop nuclear power".
202 1 10/October 26th, the State Council officially released the action plan for peak carbon dioxide emission before 2030, which pointed out that "nuclear power should be actively, safely and orderly developed.
Reasonably determine the layout and development order of nuclear power plants, develop nuclear power in an orderly manner under the premise of ensuring safety, and maintain a stable pace of construction.
Actively promote advanced reactor demonstration projects such as high-temperature gas-cooled reactors, fast reactors, modular small reactors and offshore floating reactors, and carry out demonstrations on comprehensive utilization of nuclear energy.
Strengthen the standardization and autonomy of nuclear power, accelerate the research on key technologies and equipment, and cultivate high-end nuclear power equipment manufacturing industrial clusters.
Implement the strictest safety standards and the strictest supervision, and constantly improve the ability of nuclear safety supervision. Comparing the changes of energy structure in China in recent 10 years, the proportion of non-fossil energy increased from 8.40% in 20 1 1 to 15.90% in 2020. From the perspective of power supply structure, according to the data of China Electric Power Enterprise Association, the proportion of nuclear power has increased from 1.85% and 438+0 in 2065 to 4.86% in 2026, and the importance of nuclear energy has become increasingly prominent.
2. 1 nuclear power technology evolution: economy and safety promote the development of nuclear power technology.
Economy and safety are the core goals to promote the development of nuclear power.
The development of nuclear power plants began in 1950s, and the energy crisis triggered by the rising oil price in 1970s promoted the development of nuclear power. At present, most of the more than 400 nuclear power units in commercial operation in the world were built during this period.
In the 1990s, in order to solve the negative impact of the serious accidents at Three Mile Island and Chernobyl nuclear power plants, the United States and Europe successively issued the documents "User Requirements for Advanced Light Water Reactors" and "User Requirements for European Light Water Reactors Nuclear Power Plants", and the nuclear power units that meet one of the two documents are called the third generation nuclear power units.
265438+At the beginning of the 20th century, GIF proposed that six reactor types, namely sodium-cooled fast reactor, lead-cooled fast reactor, gas-cooled fast reactor, supercritical water-cooled reactor, ultra-high temperature gas-cooled reactor and molten salt reactor, were identified as the key research and development targets of the fourth generation nuclear power plant. The fourth generation of nuclear power technology strengthens the requirement of preventing nuclear proliferation. At present, the embryonic form of relevant industrial chains has basically taken shape, and the commercialization process is expected to begin in 2030.
2.2 2065 438+09 nuclear power approval was restarted, and the third generation unit became the main model.
20 16-20 18 China nuclear power has been "zero approval" for three consecutive years, and the development of nuclear power is at a standstill.
20 1 1 year, the Fukushima nuclear power plant in Japan was hit by the tsunami caused by the earthquake and a serious nuclear accident occurred. Countries around the world are beginning to be cautious about building new nuclear power plants, which also slows down the approval speed of nuclear power plants in China.
In 20 15, China approved 8 nuclear power units, and then it entered a stagnant state from 20 16 to 20 18, with "zero approval" for three consecutive years.
20 19 nuclear power approval was restarted, and the third generation nuclear power unit is becoming the main model.
After 20 18, many third-generation nuclear power units in China have been put into commercial operation, and the safety and reliability of the third-generation units have been affirmed; In addition, on October 28th, 2065438+2008/KLOC-0, the first reactor of the third generation nuclear power unit "Hualong No.1" independently developed by China and the pressure vessel of the reactor of Fuqing Nuclear Power Unit 5 of China National Nuclear Corporation were successfully hoisted into the reactor, and the construction project progressed smoothly. Affected by this, nuclear power approval in China has been put on the agenda again.
2065438+July 2009, the National Energy Administration said that the nuclear power projects in Rongcheng, Shandong, Zhangzhou, Fujian and Taipingling, Guangdong were allowed to start, marking the official resumption of nuclear power approval.
In 2020, a total of four units of Hainan Changjiang Nuclear Power Phase II Project and Zhejiang Sanao Nuclear Power Phase I Project were approved;
202 1, Jiangsu Tianwan Nuclear Power Station 7&; Units 3-8 of Liaoning Xudabao Nuclear Power Plant; Unit 4 and Unit 5 of Hainan Changjiang Multi-purpose Modular Small Reactor Science and Technology Demonstration Project were approved, and the approval progress of nuclear power units in China is proceeding in an orderly manner.
Judging from the start-up of nuclear power units after 20 19, the third generation nuclear power units represented by "Hualong No.1" and "VVER" have become the main models.
The independent third-generation nuclear power is expected to advance steadily according to the approval rhythm of 6-8 units per year, and the "positive development" policy is gradually being fulfilled. In March, 20021year, the government work report mentioned "actively and orderly developing nuclear power on the premise of ensuring safety", which was the first time in1year that "actively" was used to express the policy of nuclear power.
According to the China Nuclear Energy Industry Association's "China Nuclear Energy Development and Prospect (202 1)", China's independent third-generation nuclear power is expected to advance steadily according to the approval rhythm of 6-8 units per year. In 20021year, 5 units were approved and started, and the policy of active and orderly development is gradually being fulfilled.
3. 1 The rapid development of the fourth generation nuclear power technology is expected to lead the nuclear power industry into a new era.
The fourth generation of nuclear power is expected to lead the nuclear power industry into a new era.
In recent years, with the support of "863", "973", nuclear energy development, major projects and the international cooperation framework of the fourth generation nuclear energy system, China has successively carried out the research and development of five types of reactors, namely, high temperature gas-cooled reactor, sodium-cooled fast reactor, supercritical water-cooled reactor, lead-cooled fast reactor and molten salt reactor reactor, and achieved a series of research results, which are basically synchronized with the international level. Among them, China's high-temperature gas-cooled reactor and sodium-cooled fast reactor rank among the top in the world.
High-temperature gas-cooled reactor uses its high-temperature characteristics to expand the application prospect of nuclear energy in industrial fields such as process heating, hydrogen production by nuclear energy and efficient power generation. Fast reactor is the only key reactor type that can realize fuel proliferation, which will obviously improve the utilization rate of uranium resources and minimize waste by transmutation.
China's R&D is in the forefront of the world in terms of high-temperature gas-cooled reactor and sodium-cooled fast reactor.
High temperature gas-cooled reactor Huaneng Shidaowan high temperature gas-cooled reactor, the world's first reactor, was successfully connected to the grid for power generation on February 20th, 20021year, and two high temperature gas-cooled reactors are planned to be built in Shandong Haiyang Xin 'an nuclear power project.
In terms of sodium-cooled fast reactor, the CNNC Xiapu 600MW demonstration fast reactor project started at the end of 20 17, and it is planned to be completed and put into operation in 2023.
High temperature gas-cooled reactor: an advanced reactor type with inherent safety and potential economic competitiveness.
Intrinsic safety: that is, in the case of serious accidents, including the loss of all cooling capacity, nuclear power plants can only rely on the material's own ability to ensure that the reactor radioactivity will not melt and leak a lot.
The specific performance is as follows:
(1) Prevent power from growing out of control.
Taking Shidaowan demonstration project in China as an example, the mobile pebble bed reactor core is formed by continuous on-line fuel loading and unloading without stopping the reactor. Moreover, the demonstration reactor uses graphite as moderator, and the core structure material contains no metal, which has high stability, large core heat capacity and low power density.
(2) Waste heat recovery.
High temperature gas-cooled reactor uses helium as primary coolant, which has good thermal conductivity. In the case of failure of the main conduction system, the core residual heat can be led out by natural mechanisms such as heat conduction, and then discharged through the passive residual heat discharge system, and the residual heat is not enough to melt the core.
③ Containment of radioactive materials.
The demonstration reactor uses all-ceramic coated granular fuel elements and four layers of shielding materials to wrap the fuel core. As long as the ambient temperature does not exceed 1650, the silicon carbide spherical shell can remain intact and lock radioactive fission products. After testing, the normal operating temperature of the demonstration reactor is as high as 1620, and the radioactivity reaches the best level in the world.
Potential economic competitiveness: Take Shidaowan demonstration project as an example, it can be achieved through ① highly independent equipment (the localization rate of demonstration project is 93.4%) and ② "multi-integration" (under the condition that the main system remains unchanged, the two modules are combined into one, that is, the nuclear island is driven by two pebble bed reactor modules and two steam generators, and the power is generated by a steam turbine.
This modular construction shortens the construction period, greatly reduces the engineering quantity and improves the economy) to control the cost.
At the same time, if the construction cost is compared, although the cost of HTR-PM in the reactor (mainly PRV and internals) is much higher than that of the PWR nuclear power plant of the same scale, according to the relevant literature research of Zhang et al., in the total construction cost of a PWR nuclear power plant, the proportion of the reactor (PRV and internals) is very limited, about 2%, so it is influential.
Compared with the PWR nuclear power plant of the same scale, even if the cost of the reactor body of HTR-PM demonstration power plant is increased to 10 times, the increase of the total cost of the whole power plant can be controlled within 20%.
Sodium-cooled fast reactor: In addition to its inherent safety, it also has the advantages of nuclear fuel proliferation, improved utilization rate and minimized nuclear waste.
Improve the utilization rate of nuclear fuel: The fast reactor technology adopts mixed oxide of uranium and plutonium (MOX). In the fast reactor, the fuel area of the core is fissile plutonium 239, and uranium 238 is placed in the peripheral regeneration area of the fuel area.
Plutonium -239 will release more fast neutrons during nuclear fission reaction. These fast neutrons will not only maintain the chain reaction of plutonium -239 nuclear fission, but also be absorbed by uranium -238 in the peripheral regeneration area.
Uranium -238 absorbs fast neutrons and becomes uranium -239, but uranium -239 is very unstable, and it becomes plutonium -239 after two beta decays.
Therefore, when the fast reactor is running, the newly produced fission nuclear fuel is more than the consumed nuclear fuel, and the fuel is burned more and more, which is called proliferation reaction.
The proliferation reaction makes full use of uranium resources, and the environmental pollution caused by nuclear waste is expected to be solved, thus making the fourth generation nuclear power a nuclear energy utilization system with superior safety and economy, less waste, no off-site emergency and nuclear proliferation prevention ability.
3.2 Under the new nuclear power technology, the comprehensive application of nuclear energy becomes possible.
According to the research status and prospect of comprehensive utilization of nuclear energy announced by Chinese Academy of Sciences, from the perspective of energy efficiency, direct utilization of thermal energy is an ideal way, and power generation is only a form of nuclear energy utilization.
With the development of technology, especially the gradual maturity and application of the fourth generation nuclear energy system technology, nuclear energy is expected to surpass the role of providing electricity only, and play a huge role in ensuring the sustainable development of global energy and water security through various comprehensive utilization forms such as hydrogen production by nuclear energy, high-temperature process heat, nuclear heating and seawater desalination.
Hydrogen production by nuclear energy: Hydrogen production by nuclear energy is to use the heat generated by nuclear reactors as primary energy to prepare hydrogen from hydrogen-containing water or fossil fuels. At present, the mainstream technologies of hydrogen production from nuclear energy include thermochemical iodine-sulfur cycle, mixed sulfur cycle and high-temperature steam electrolysis, which realize the efficient conversion from nuclear energy to hydrogen energy and effectively reduce the efficiency loss in the process of thermoelectric conversion. High temperature gas-cooled reactor (outlet temperature 700 ~ 950℃) and ultra-high temperature gas-cooled reactor (outlet temperature above 950℃) are the most ideal nuclear reactors for hydrogen production by high temperature electrolysis because of their inherent safety, high outlet temperature and appropriate power.
1) High temperature ceramic coated fuel has high safety.
2) Coupled with thermochemical cycle process. At 800℃, the theoretical hydrogen production efficiency of high temperature electrolysis is higher than 50%, and the efficiency will be further improved with the increase of temperature.
3) Nuclear heat-assisted hydrocarbon reforming uses the process heat of high-temperature gas-cooled reactor to replace the heat source in the conventional technology, which can partially reduce the use of fossil fuels and correspondingly reduce CO2 emissions.
4) It can be coupled with a gas turbine to generate electricity with an efficiency of 48%.
At present, CNNC, Tsinghua University and Baowu Group, etc. We have jointly carried out preliminary cooperation in the combination of hydrogen production from nuclear energy and hydrogen metallurgy, and plan to carry out pilot verification during the Tenth Five-Year Plan period and demonstration of hydrogen production from nuclear energy in high-temperature reactors during the Tenth Five-Year Plan period.
Compared with different hydrogen production methods, high temperature gas-cooled reactor has cost advantage.
The U.S. Department of Energy conducted an economic evaluation of hydrogen production from nuclear energy under the Nuclear Hydrogen Innovation Program, and the obtained hydrogen cost was 2.94-4.40 USD/kg. In addition, the International Atomic Energy Agency has formulated a hydrogen economic evaluation plan, and the participating countries have made a scenario analysis of the cost of hydrogen production by nuclear energy. The cost of hydrogen obtained in different scenarios is 2.45-4.34 USD/kg.
Nuclear heating: nuclear heating takes the steam extracted from the secondary circuit of nuclear power unit as the heat source, carries out multi-stage heat exchange through the first heat exchange station in the plant and the heat exchange station of the off-site heating enterprise, and finally transfers the heat to the end users through the municipal heating pipe network.
From the safety point of view, during the whole heating process, there are multiple loops between the nuclear power plant and the heating users, and only heat is transferred between each loop, and hot water only circulates in the residential area, which is relatively safe. From the perspective of carbon emissions, nuclear energy, as a zero-carbon energy source, is much better than traditional coal-fired thermal power plants.
2021115 The second phase of the National Energy Nuclear Heating Commercial Demonstration Project was officially put into production in Haiyang, Shandong Province; 202165438+On February 3rd, Zhejiang Haiyan Nuclear Energy Heating Demonstration Project (Phase I) was officially put into production in Haiyan, Zhejiang. In the long run, nuclear heating, as a zero-carbon clean heating method, has the potential of replication and promotion, and also contributes to the realization of China's "two-carbon" goal.
4. 1 Spent nuclear fuel needs to be properly disposed of, and China has determined the closed-loop route.
Spent fuel refers to nuclear fuel produced by nuclear power plant reactors after irradiation and use.
Nuclear fuel reacts in the reactor by neutron bombardment and is discharged from the reactor within a certain period of time.
Spent fuel contains low uranium, which can not continue to maintain nuclear reaction, but it still contains a lot of radioactive elements and needs to be properly disposed of.
Spent fuel treatment methods are divided into "open nuclear fuel cycle" and "closed nuclear fuel cycle". The difference is that "open type" directly cools and packages spent fuel and sends it to deep geological stratum for disposal or long-term storage, while "closed type" sends spent fuel to reprocessing plant to recover uranium, plutonium and other substances, and then solidifies the waste for deep address stratum disposal.
In 1980s, China established the "closed cycle" route of nuclear fuel to improve the utilization rate of resources, reduce the volume of radioactive waste and reduce its toxicity.
4.2 The scale of spent fuel emissions continues to grow, and the first set of 200 tons/year treatment facilities is under construction.
The scale of spent fuel emission is increasing, and the contradiction between supply and demand is becoming increasingly prominent.
In the summary of the reply to the proposal, the National Energy Administration, released at the Fourth Session of the 13th National People's Congress at 283 1 (index number: 00019705/2021-00408) on July 5th, 20265438, said that the million kilowatt nuclear power units emit 20% of spent fuel every year. According to the nuclear power installed capacity of 53.26 million kilowatts in China as of 202 1 and February, China will produce about 1065.2 tons-133 1.5 tons of spent fuel every year.
According to the statistics of China nuclear system Think Tank Series (Volume III), in 2020, China will produce 1 100 tons of spent fuel, and the accumulated amount of spent fuel has reached 8,300 tons. It is estimated that the cumulative quantity will reach 1 14500 tons by 2050.
With the continuous expansion and continuous operation of nuclear power, the scale of spent fuel emissions in China will continue to increase every year, and the sustainable development of nuclear power is bound to be inseparable from the related facilities for spent fuel reprocessing.
The first set of 200 tons/year treatment facilities is under construction, and there are certain development opportunities in the future under the urgent demand.
According to the introduction of Jiangsu Shentong's plan for non-public offering of A shares, the first set of closed spent fuel treatment facilities under construction in China has a treatment capacity of only 200 tons/year, while the capacity of the reactor storage pool used in the open nuclear fuel cycle has been overloaded, which is in sharp contrast to the relatively large annual output and accumulation of spent fuel.
In addition, as early as 20 16, the National Development and Reform Commission and the National Energy Administration clearly stated in the Action Plan for Energy Technology Revolution and Innovation (20 16-2030) that the spent fuel reprocessing technology should be developed, and it was proposed that China's first large-scale commercial spent fuel reprocessing plant of 800 tons should be basically built in 2030.
The development of China's nuclear power industry can not be separated from the synchronous improvement of production capacity related to "closed nuclear fuel cycle treatment", and the market demand is more urgent, so there are definite development opportunities in the future.
Benefiting from the gradual realization of the positive development of nuclear power, the prosperity of the entire nuclear power industry chain is expected to pick up.
Nuclear power is a typical heavy asset industry, which can obtain high-quality cash flow during the operation period. With the advantages of high hours, low power cost, low carbon stability and high efficiency, it is expected to usher in a period of development opportunities under the background of carbon neutrality.
(1) Risk that the construction progress of nuclear power plant is less than expected: the construction period of nuclear power project is long, and if the construction period is extended for various reasons, the construction cost will rise sharply;
(2) Policy risk: The nuclear power industry is highly regulated by the government, and relevant policy changes may have an impact on the development of nuclear power;
(3) Nuclear safety risk: If a nuclear accident occurs worldwide, it will adversely affect the pace of project promotion and the long-term development space of nuclear power.
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