Good news or bad news? -- Why do you want to develop nuclear power

1. Composition and classification of nuclear power plants

Whenever talking about nuclear power plants, whether it is news reports, knowledge questions, popular science articles or even grapevine news, there are a lot of "xx pile" such nouns. Sometimes it seems that there are such numbers as "second-generation reactors" or "third-generation reactors" (not second-generation and third-generation reactors), and sometimes there are "parallel goods" such as "pressurized water reactors" or "boiling water reactors", which the average person will be confused by. In fact, the classification of nuclear power roughly has two routes, the first route is divided according to the age, the second route is divided according to the type of pile. Reactor type refers to the type of reactor design in a nuclear power plant, which refers to a difference in principle rather than a technical adjustment. In fact, it is easy to see that the first type of way is artificial classification, and the second type of way is divided from the technical objective point of view. In order to see this more clearly, I have drawn the following diagram to help you understand the relationship.

From the division of time, it can now be divided into a generation of piles to four generations of piles. There is no clear definition of the generation reactor, according to the author's information, probably refers to the world's first reactor in 1942 to around 1960, in the experimental stage of the reactor. The author defines a category called the experimental reactor, but the term is my definition. Since the 1940s, nuclear reactors have been highly classified, so basically each country's reactor is its own system, and it is difficult to have anything in common. But what the first generation reactor and the experimental reactor have in common is that in the experimental stage, the data was highly confidential at the time, and now there is very little information. Even if there were grid-connected ones (like Obninsk, the first nuclear power plant in the Soviet Union), they didn't last very long.

As time entered the 1960s and 1970s of the last century, the technology of nuclear power plants gradually began to finalize, which is the so-called second-generation reactor. There are three main types of reactors in the second generation, which are light water reactor, heavy water reactor and gas cooled reactor. The classification of reactor types comes from the design of the reactor. In a reactor, fissile material (mainly uranium and plutonium) emits neutrons, but these neutrons are distributed at different energy levels (which can simply be understood as having different speeds). And the neutrons that are released can cause other fissile materials to continue fission and that's called a chain reaction, which is what we're looking for in a sustained nuclear reaction. This chain reaction requires a slower neutron, called a thermal neutron. But a lot of the neutrons that are released are going very fast, so we need something called a moderator to slow down the neutrons and keep the chain reaction going. In the Chernobyl game, there is a lot of mention of graphite blocks, which are the moderators used in the reactor. In addition to graphite, high-purity light water (that is, ordinary H2O) and heavy water (D2O) are both considered ideal moderators. In addition to the moderator, there is a basic parameter for the differentiation of the stack type is the coolant. The fission reaction continues to release a lot of heat, and we need coolant to move this part of the heat away, and then use it to generate electricity. The coolant mainly uses high-purity light water (that is, ordinary H2O) and heavy water (D2O), as well as high-purity inert gases (CO2 is generally used in second-generation reactors). We can see that light water and heavy water can act as both moderator and coolant, great! And light water is ordinary water, we can easily get (of course, this water refers to high purity deionized water, can not use tap water ah), this is simply perfect! Therefore, the largest proportion of second-generation reactors is light water reactors, which account for more than 95% of current reactors. However, the moderating effect of light water is not good enough, so a certain concentration of nuclear fuel is required (about 4-5% of U235 Fengdu), and natural uranium ore cannot be used (0.7% of U235 Fengdu). However, if heavy water is used, natural uranium ore can be directly used as fuel, which greatly reduces the preparation cost of raw materials, so that there is a heavy water reactor. But whether it is light water or heavy water, it is easy to vaporize, even at a certain pressure, their boiling point is relatively low. Therefore, light water and heavy water can carry relatively less heat as coolants, and the core outlet temperature is low. However, the use of gas as a coolant does not have this problem, you can get a much higher exit temperature, but CO2 can not be used as a moderator, so generally speaking, gas cooled reactors use graphite as a moderator, usually known as graphite gas cooled reactors. These are the three main types of second-generation reactors.

In the official report of China's nuclear power, one can often hear a word "three generations of reactors", which is a sign of advanced nuclear power in China. So what is a three-generation pile? In fact, the third generation reactor is exactly the same as the second generation reactor, which is also a light water reactor, a heavy water reactor and a gas cooled reactor. After the Chernobyl incident, the United States and Europe respectively issued the "Advanced light water reactor user requirements" documents, namely the URD document (utility requirements document) and the "European User Requirements for light water reactor nuclear power plants". The European utility requirements document (EUR) further defines the requirements for preventing and mitigating serious accidents, improving safety and reliability, and improving human factors engineering. Internationally, nuclear power units that meet the URD file or EUR file are usually called third-generation nuclear power units. So in fact, the third-generation reactor is just a safer second-generation reactor, and there is no revolutionary change from a technical point of view.

The fourth generation reactor is also called the advanced reactor, which is a new generation of reactors that is truly changed from the reactor type. At present, the four generations of reactors are basically staying in the design drawings, the original prototype and even the experimental reactor level, the fastest progress is to enter the construction of commercial demonstration reactors, and there is still a distance from practical application. (Specifically, this refers to civilian, not military applications.) At present, there are mainly six types of fourth-generation reactors that are considered to have the most potential, which are high-temperature gas-cooled reactors (using He gas as a coolant), supercritical pressurized water reactors, molten salt reactors (before the Chinese Academy of Sciences invited Taoist monks to open light foundation ceremony in Gansu is this), gas-cooled fast reactors, lead-cooled fast reactors and sodium-cooled fast reactors. You can see that there are three types of reactors called fast reactors, fast neutron reactors, that don't need moderators. Among them, the sodium-cooled fast reactor is a relatively mature technology, and the Beijing Experimental Fast Reactor in Beijing Fangshan and the demonstration fast reactor started in Fujian Xiapu are of this type. Most of the fourth-generation reactors have various advantages, such as high exit temperature, zero core meltdown risk and even fast neutron proliferation, but due to the limitations of technological development, there are still many difficulties to overcome.

2. Nuclear power development in the world and China

After introducing the basic types of nuclear power plants, the author will introduce the development of nuclear power in the world and China, especially to see if China is developing nuclear power throughout the country. According to the 2017 annual report of the IAEA (International Atomic Energy Organization), by the end of 2017, there were 448 nuclear power reactors in operation in the world, and the total number of reactors under construction reached 59. The pie chart below is the distribution of these 448 reactors, and China is included in the others in this statistics. Among them, there are 45 nuclear power reactors in operation in China, accounting for 10.04%; China has 11 reactors under construction, accounting for 18.64%. From this point of view, China is indeed focusing on the construction of nuclear power plants.

The number of reactors is one indicator, but more important is the share of nuclear power in the country's total electricity generation. France has always been a famous nuclear power country in the world, at the end of 2017, France's nuclear power generation accounted for 71.6%, South Korea was 31.7%, the United States and Russia are close to 20%, and China is less than 4%. The reason why China's nuclear power has been built at a high speed these years is largely due to the lack of nuclear power in our country in the past. And nuclear power is a high-input industry, when the economy is not developed enough, can not effectively develop. With the development of the economy in recent years, we have begun to build nuclear power plants of our own. Whether to develop nuclear power or not will be discussed in the next section.

There has been a rumor on the Internet that after the Fukushima nuclear power plant accident, most countries in Europe and the United States have taken an attitude of giving up nuclear power, and only China is in large-scale construction. There are even so-called public intellectuals who criticize China's local and even central governments for ignoring the lives of the people and the safety of future generations for the sake of political achievements. The rhetoric is generous, as if the Chinese government, which built the nuclear power plant, is evil and should be overthrown. But is this really the case? Has there really been a qualitative change in the way governments around the world view nuclear power before and after Fukushima?

The chart below shows the attitudes of governments around the world towards nuclear power as of 2017. The countries painted black are those whose national legislation prohibits the building of nuclear power plants, including Denmark, Italy and Hungary. It is worth pointing out that all of these countries enacted legislation in the last century, unrelated to Fukushima (Italy's legislative push is partly related to Chernobyl).

The countries and regions painted in red are those where the government has announced accelerated nuclear decommissioning, which means shutting down nuclear power plants before they expire. The countries and regions in the world that have so far made it clear that they will accelerate their nuclear abandonment are Germany and Taiwan, which have announced that they will establish a nuclear-free state by 2022 and 2025, respectively. In 2016, nuclear power generation accounted for 14.1% of Germany, and Germany has adopted a very systematic plan to shut down nuclear power, including personnel diversion, shutdown and decommissioning plans, the development of renewable energy, extend the life of hard coal power plants, increase the purchase of electricity from neighboring countries. Even so, Germany is the EU's worst carbon reduction country in the past five years, which is controversial. Due to Germany's dependence on the European grid, even temporary power shortages can be solved by purchasing power from the grid. In Taiwan, China, the slogan of a nuclear-free homeland was raised in order to win the votes of the people after Tsai Ing-wen took office as the regional leader. However, due to Taiwan's energy shortage and total dependence on imports, the distribution and development of renewable energy are poor. After the government forced the shutdown of Nuclear 2 and 3 and the suspension of nuclear 4 plants, the entire Taiwan's electricity reserves remained below the red line of 4%, meaning that small fluctuations can have big consequences. The Taiwan blackout on August 15, 2017 is the most true portrayal, just because a power plant operation error, so that several units off the grid, resulting in 6.68 million households in Taiwan, and caused three fire alarms, one death tragedy. At the same time, it caused chaos to people's lives, the fire department received 730 trapped elevator distress cases, and the most serious power outage in New Taipei City, more than 1,000 intersection traffic lights failed, and during the rush hour, resulting in traffic chaos. According to the estimates of the Ministry of Economic Affairs, manufacturers in the industrial zones under its management lost nearly NT $88 million, and the entire industry in Taiwan suffered heavy losses. Thus, a hasty decision to shut down nuclear power without a clear alternative would be reckless.

The countries painted yellow on the map are those whose governments have announced a time-by-time phase-out, that is, they have not shut down their active nuclear plants in advance, nor have they approved the extension of their service. These include Spain, Belgium, Switzerland and possibly South Korea. Spain's nuclear decommissioning time is 2021, and in 2016, nuclear power accounted for 20.3%. Spain has plenty of sunshine, the British people go to Spain in the winter to bask in the sun, so Spain is vigorously developing photovoltaic power generation and has achieved quite outstanding results. In addition, Spain is also backed by France, a nuclear power country, which can effectively buy low-carbon electricity, so the prospect of Spain's nuclear abandonment is very good. Switzerland is expected to complete nuclear abandonment in 2034, although the proportion of nuclear power in 2016 as high as 33.5%, but Switzerland's small size, small electricity consumption. Although the development of photovoltaic and wind power in Switzerland is extremely slow, the time until 2034 is still a long time, and the Swiss government has plenty of time to adjust its policy. At the same time, by around 2030, the vast array of offshore wind turbines in the North Sea in Britain, Denmark, Germany and Norway should be operational, by which time a large proportion of Europe's electricity will be obtained through this area, Switzerland is no exception. Belgium's nuclear abandonment schedule is set in 2025, but the high proportion of 55.2% of nuclear power, and the shortage of renewable energy alternatives can not be smoothly developed, Belgium's nuclear abandonment journey is difficult. After taking office, President Moon Jae-in announced his intention to build a nuclear-free homeland, but he has not given an actual timetable or roadmap for nuclear abandonment.

As can be seen from the above, there are only six countries and regions in the world where the government has determined to abandon nuclear weapons, of which only Germany and Spain are relatively smooth on the road to abandon nuclear weapons, Switzerland and South Korea are in a wait-and-see state, and Belgium and Taiwan are extremely hard to go. In fact, this shows that when there is no reasonable road map and alternative, it is very unwise to choose to abandon nuclear weapons only from a political perspective.

Apart from the above six countries and regions, there are many more countries and regions that have been colored on the map. The countries in dark blue are those that already have and are building new nuclear power plants, including the five permanent members of the UN Security Council (the US had a long moratorium on nuclear power after Three Mile Island, but restarted its construction and approval during the Obama administration, and the first post-Three Mile Island US nuclear power plant was connected to the grid in 2016). In addition to South Africa, the remaining three BRIC countries are Ukraine, Pakistan, the Netherlands, Slovakia, and Argentina, which were devastated by Chernobyl. You can see that these countries actually account for the majority of the world's population, land and GDP. Holding and developing nuclear power is still the mainstream of the world. The countries painted in light blue on the map are those that already have nuclear power but are not building any, including Canada, Iran, Mexico, South Africa and the European countries of Sweden, the Czech Republic, Romania, Bulgaria and Hungary. Most of these countries do not need to build new nuclear plants because they are already self-sufficient in electricity and their economies are either growing slowly or at a pace commensurate with renewable energy.

Highlighted in dark green on the map are countries that are building their first nuclear power plants, including Belarus, also affected by Chernobyl; Turkey, which has long hoped to become the hegemon of the Middle East; Egypt, which has suffered power outages after several coups; and the United Arab Emirates, which has more oil than it can use. The UAE, in particular, as a pure oil exporter, could have used oil-fired power stations for cheap electricity. But the UAE is not only actively developing photovoltaic and solar thermal power generation, it has also invested in the construction of its first nuclear power plant. This suggests that, at least in the eyes of the UAE government, nuclear power is one of the alternatives to thermal power.

Many of the countries in light green are building their first nuclear power plants, not to mention one example. In turn, let's talk about why these countries, which have not been colored, are indifferent to nuclear power. A closer look at the map shows that countries with no interest in nuclear power include countries in central Africa that are still struggling to feed themselves; countries in the Middle East that are at war; countries in Central Asia; the Philippines, Laos, and Myanmar in Southeast Asia; the dismembered states of the former Yugoslavia; Greece, whose government is on the brink of bankruptcy; and small countries in the Caribbean. These countries simply do not have the capacity to build nuclear power, or the world will not allow them to do so (such as Syria and Iraq).