南理工_new energy technology_Research and development of controlled nuclear fusion.doc

1INTRODUCTION Energy and life are closely related We have to admit that we are facing an unprecedented energy crisis It is an urgent task that we develop and use new energy At present nuclear energy is an important leading role in the development of new energy Nuclear energy comes from fission and fusion Fission has been widely used in the field of power generation The nuclear power station has more than 400 As the nuclear fusion reaction requires a very high temperature so the realization of nuclear fusion is very complicated and very difficult But there are two major advantages of nuclear fusion One is that nuclear fusion does not produce long term and high levels of nuclear radiation the other one is the nuclear fusion materials more than nuclear fission materials on the earth According to the current world energy consumption it can let the human use for 10 billions years that the earth has the nuclear fusion energy Now we are faced with how to control the process of nuclear fusion and how to use the heat to generate electricity Once these complex technical problems are solved the entire world s energy problem will be solved thoroughly The developed countries continue to invest a lot of manpower material resources and financial resources to study and develop it because of the long term significance of nuclear fusion 2 DEVELOPMENT BACKGROUND OF CONTROLLED NUCLEAR FUSION Nuclear fusion released a great energy and people did not stop it from the beginning of the 50 s in twentieth Century The ultimate goal of nuclear fusion is not to make a hydrogen bomb The long term goal is the peaceful use of nuclear fusion 2 1 Nuclear fusion reaction The nuclear fusion fuel is light atoms such as hydrogen isotope deuterium and tritium Under certain conditions such as high temperature and high pressure the nuclear of atoms interact with each other and form a new reaction of heavy nuclei There is loss of mass So there is a release of energy in the reaction As shown in figure 1 Fig 1 nuclear fusion reaction It describes the fusion reaction The equation reaction is as follows when deuterium and tritium has fusion reaction MeVnHeTD 6 17 1 0 4 2 The mass of the reactants is more than the mass of the product from this reaction equation And the reaction takes place with a mass loss which is converted to 17 6MeV energy in the middle of the process The content of deuterium is very rich on the earth 1L of water contains 0 03 grams of deuterium Our earth has 1 3 billion and 86 million cubic kilometers of water It contains energy These energies are enough for us to J 31 1047 11 use ten billion years 2 2 Controlled nuclear fusion The explosion of a hydrogen bomb is primarily nuclear fusion But it is the high temperature and high pressure environment produced by the atomic bomb explosive Then the deuterium and tritium had a nuclear fusion reaction and released a great energy But the explosive energy of this moment is not controlled If we can control the energy released by the fusion and use it to social Research and development of controlled nuclear fusion E mail Abstract This paper tells the development of controlled nuclear fusion energy at the first Then it analyzes the definition and the main research methods and the problems of controlled nuclear fusion Magnetic confinement fusion and inertial confinement fusion are two main research approaches in the study of controlled nuclear fusion This paper explains the principle of magnetic confinement fusion firstly Then it analysis the working principle of tokamak It also analyzes the development of magnetic confinement nuclear fusion in China In the inertial confinement fusion the paper firstly explains the basic principle of the method Then this paper introduces the development of the NIF device in American and SG engineering in nuclear fusion research in China People still insist on the study of nuclear fusion people will be able to achieve controlled nuclear fusion in the future Key Words Controlled nuclear fusion Magnetic confinement fusion Inertial confinement fusion production and human life Then we achieve controlled nuclear fusion In Spider Man 2 the energy used by Dr octopus is controlled nuclear fusion 2 3 Research way of controlled nuclear fusion From the last century 50 s to now people poured a lot of energy to study nuclear fusion We still believe that there is still a long way to go before we achieve controlled nuclear fusion Scientists estimate that we have to wait for more than 30 years before building nuclear fusion power station In this study people put forward various ideas and the construction of the device is also various But from the current point of view the way to controlling nuclear fusion is divided into two major categories magnetic confinement fusion MCF and inertial confinement fusion ICF This paper will introduce and analyze them in the third and fourth sections However both MCF and ICF they are just the experimental device It is quite a long distance away from the real economy And there are also a variety of technical problems to solve 2 4 The problem of controlled nuclear fusion Deuterons and tritons are positively charged under normal conditions And they are mutually exclusive So if we want to put them aggregate We need to use a lot of energy to enable them to overcome the repulsion The deuteron and Triton have a large enough kinetic energy when the nuclear fusion material is heated to a high temperature one hundred million degrees But it only provides the speed of the collision we should also restrict the nuclear material so that they reach a high enough density This would make it possible for the fusion of deuterium and tritium This is the realization method of deuteron and triton polymerization From the above conditions for the occurrence of fusion it can be found that controlled nuclear fusion is very difficult This paper will discuss the problem of controlled nuclear fusion 1 Constraint problem of plasma Fusion nuclear material format plasma after high temperature and high pressure treatment Due to the plasma is a highly complex multibody system which has the electromagnetic interaction various wave particle interactions and nonlinear turbulent flow problems Figure 2 shows the complexity of the internal structure of the plasma If we want to master the laws of these plasmas we must need a lot of manpower material resources and financial resources Fig 2 Four states of matter 2 Ignition problem and material problem It requires 100 millions degrees of high temperature environment to start the fusion reaction After the occurrence of nuclear fusion its own energy can be maintained by the control First it is a very difficult technical problem how to produce 100 millions degrees of high temperature Another is the material problem what material can withstand the temperature of 100 millions degrees A strong magnetic field is required in the confinement of the plasma The strong magnetic field is produced by high current which requires the conductor to be superconducting material and it has not solved the problem of high temperature superconducting materials Fig 3 lists the high temperature superconductor materials The highest critical temperature of high temperature superconductor material is 165K It is still very low FIG 3 Development of high temperature superconducting materials It shows the critical temperature of high temperature superconductor material 3 Neutron radiation problem A large number of neutrons will be produced when deuterium and tritium occur fusion The radiation problem is produced when the material is irradiated by neutron And these neutrons will damage the reactor material This is a problem that must be considered There are 3 major challenges controlled nuclear fusion the technology problem of controlled nuclear fusion is still more than these 3 MCF Magnetic confinement fusion process is generally as follows First deuterium and tritium and their free electron format aplasma in the ultra high temperature Then we use the magnetic field of the special shape to constrain and compress the plasma so that they can achieve the ignition condition of controlled nuclear fusion Ignition condition is 1 Reactor temperature is higher than 100 millions degrees 2 The density of the plasma is greater than 1020 per cubic metre 3 The time of the constraint should be more than 1s So far MCF is a nuclear fusion approach which people spend most research and money on it Tokamak device is one of the important roles of magnetic confinement nuclear fusion 3 1 Tokamak Tokamark was invented in the 50 s of last century It is a circular container for controlled nuclear fusion by magnetic confinement Its name is made up of the first 2 letters of 4 words They are toroidal kamera magnet and kotushka It is feasible that uses Tokamak to start nuclear fusion But its related results are generated in the form of a broken pulse which is still a big gap in the real life Now the superconducting technology has been used in the Tokar Mark coil This is a major breakthrough of controlled nuclear fusion At present the study of the Tokamak has become a hot international craze 3 2 Working principle of Tokamak Fig 4 Schematic diagram of Tokamak device it shows the principle of Tokamak Fig 5 Physical structure of Tokamak it shows the vacuum chamber of the Tokamak From Fig4 and fig 5 it can be seen that the main body of the Tokamak device is composed of 2 parts namely the magnetic field system and the vacuum system Magnetic field system has 2 main functions The main effect of the longitudinal field coil is used to produce a strong longitudinal magnetic field And then the plasma is confined in a vacuum tube So they maybe start to react The first step is to make the material become the plasma state Plasma state is the fourth state of matter The material is a fully ionized in this state Its whole is electrically neutral And due to the high temperature it has enough kinetic energy to get rid of the shackles of the atomic nucleus At this time the atomic nucleus is completely exposed and prepare for the conditions for the collision of the nucleus When the plasma is heated to tens or hundreds of millions of degrees nuclei can get rid of repulsion gather together and form a fusion reaction If there is enough density and enough heat to restrain them the reaction will be able to run steadily Common heating systems are as follows 1 Ohmic heating The change of the magnetic field generates an electric potential which generates an electric current in the plasma The plasma has a resistance which can be heated by ohmic heating It is such as resistance element 2 Microwave heating We use electromagnetic waves to heat plasma The principle is same as the electromagnetic microwave 3 Neutral beam heating Neutral beam heating is actually an energy transfer process The energy of the particles is passed to the plasma after injecting the energetic particles into the Tokamak And the heating is realized We need to speed up the particles with the accelerator so the cost is relatively high Vacuum system The vacuum chamber is the ring The wall of the vacuum chamber is made of stainless steel We must consider the mechanical strength The wall must have a certain gap in order to ensure the penetration of magnetic field Gas pumping system generally is a turbo molecular pump This device can make the vacuum chamber pressure less than Pa 6 10 3 3 Development of magnetic confinement nuclear fusion in China From the last century 50 s China began the research of nuclear fusion mainly concentrated in the Southwest Institute of physics and the Institute of plasma physics in Chinese Academy of sciences HL 1 was on operation in 1984 China developed a HT 7 superconducting Tokamak marking China become the world s fourth superconducting Tokamark in 1994 In 2005 China completed the first non circular cross section Tokamak device EAST Then in 2006 China s first EAST achieved the first ignition which is an unprecedented achievement Fig 6 EAST The graph shows its shape EAST has a first set of neutral beam injection NBI in 2012 This marks the EAST upgrade to EAST NBI 3 4 ITER The International Thermonuclear Experimental Reactor program called ITER The proposal originated in 1985 It was designed to work in 1988 The design of the project was completed in 2001 and it has cost 1 5 billion Our government insists on participating in the ITER program for the sake of our country s energy In 2003 our country decided to formally participate in ITER negotiations Now ITER has 7 member countries China the EU South Korea Russia Japan India and the United States Scientists assess the construction of ITER will cost 5billions in 1998 Fig 7 Schematic diagram of ITER It is actually a nuclear fusion power station As shown in Figure 7 the reactor unit in the ITER project is a large Tokamak device ITER device not only reflects the latest achievements in the field of fusion energy research but also the world s top technology such as high current accelerator technology superconducting technology complex control technology and so on 4 ICF Inertial confinement fusion is proposed in the 60 s of the last century This fusion technique utilizes a laser So as to achieve the conditions of ignition we first use a laser to heat the deuterium and tritium fuel to reach the temperature of the reaction and let it be compressed Then we will get the energy gain 4 1 Principle of inertial confinement fusion Figure 8 Inertial confinement nuclear fusion It describes the basic principles of ICF As shown in Figure 8 the fuel ball is the main component of the inertia constraint Spherical shell material can be metal or glass etc The ball is equipped with deuterium and tritium gas The principle of inertia is as follows 1 With the laser irradiation The surface of the shell will absorb energy and evaporation 2 According to Newton s third law the inner layer of the sphere will be squeezed because of the effect of reaction force At this time the pressure increases in the gas the temperature is also rising 3 With the continuous irradiation of the laser the fuel is constantly squeezed into the center If the radius of the ball is R1 and the compression ratio is R2 So the compression ratio is R1 R2 4 When R1 R2 can reach about 30 So the temperature can be reached very high When the temperature reaches the ignition temperature the mixture of the small ball will explode The process is very short There are more than three such explosions per second and can continue to go on The energy is equivalent to a million kilowatt class of power stations 4 2 Technical difficulties of inertial confinement nuclear fusion Why don t we still use this technology to build power stations today This paper will analyze the causes 1 No matter whether the laser beam or the particle beam their power has not yet reached the power to build power stations 2 Irradiation problems Laser irradiation must be uniform And fuel balls must also be clean Once the technical problems occur it will lead to the compression is not uniform the explosion rate is not high 3 Improvement of explosive method The method of center explosion is not necessarily the best solution Whether there are better and more economical plan Many countries are trying to study and explore the optimal method of ignition 4 3 NIF devices in the United States U S National Ignition Facility began to construct in 1997 Because of a lot of power and serious over budget so that it was originally planned for 5 years to complete the project Thus it was completed in February 2009 Figure 9 for the construction of NIF From the picture we can see a lot of holes for the laser meter Figure 9 NIF The whole set of NIF device has 6000 different kinds of high tech equipment And the construction of the plant is as long as a kilometer In Fig 9 the device is designed to allow the 192 laser device to launch a laser at the same time in 10 9 seconds and focus on the size of a pencil head As shown in Figure 10 it is the fuel ball in the NIF device Allowable error can not be greater than 30ps In order to achieve such a high precision manufacturing and installation of 6000 kinds of equipment is very important All of the equipment is nearly perfect According to the official announcement NIF has cost 3 5billion Fig 10 Installation of fuel balls The United States NIF successfully realized the ignition Its output is greater than the input of energy in July 5 2012 This is a landmark breakthrough in controlled nuclear fusion But unfortunately due to various external factors the study of NIF turned to the study of nuclear weapons 4 4 SG project The device belongs to the Nd glass laser system It ranks fourth in the world s laser device We get the result of a lot of physical experiments in our country from it SG II provides an irreplaceable means of experiment in inertial confinement fusion X laser and other high tech fields It is an important experimental platform in this field SG has successfully completed the construction It can reach the level of 8 beams of light pulse 10000J These achievements mark our country to become the third country to master high po