 Now, this accelerator driven systems or it is called accelerator driven subcritical reactor systems, they are of great importance to whole world in general and to India in particular. System was discussed briefly in lecture number 9, here I will give more details. Now, if you take the use of right now there are three main sources of energy, one is coal, other is oil and third one is gas. These are the three resources, results known at this moment and it is estimated that the coal will last only about 250 years, oil about 50 years and gas over 65 to 70 years in this range. That means we have to find a new source of energy because when these all three sources they are finished then there will be problem. So, use of solar and wind is picking up right now and of course nuclear power appears to be inevitable options as future energy source because that will be a safe as well as cheaper than the other ones. Of course, now solar energy cost is coming down. However, in this case disposal of nuclear waste in any reactor these radioactive nuclei are formed and they are called nuclear waste. One is plutonium, neptunium, amrysium and curium and that is an important issue in harnessing the energy from the critical reactor, they are more formed in the critical reactor. So, if we can find a system where these nuclear waste nuclei are not formed or they are made use of in some way or the other then the system will be acceptable to everybody. Now, in a conventional system how it works conventional reactor system normally we use uranium 235 and a thermal neutron interacts with it and that breaks into two nuclei plus because of fission process and in this process an energy of about 180 MBV to about 0.2 GeV is released and that is what is used for generation of electricity. Now, the problem comes here that uranium has several isotopes and only one of them for example uranium 235 has only 0.7 percent and which is fissile. So, uranium 235 percent is only 0.7 percent which and this uranium 35 is fissile. So, that means this fission can take place only with the uranium 235 while if you take that uranium 238 which is 99.3 percent roughly which is a fertile material and it is not a fissile material. So, it cannot be used for energy production in conventional reactors. So, this basically becomes a waste actually it has to be taken care of not only that not only these ones but even several minor actinides are produced as I mentioned in the earlier in this case and that minor actinides are produced with heavier isotopes of uranium like 238 and neutrons are absorbed not only minor actinides but also fission products are produced. So, they are some of them are listed here and their life half-lives are also mentioned and you can see that it will take a lot of time for them to reduce to other two safe elements or other two safe isotopes. In the case of this reaction in fission several fission products also are formed and they are also radioactive and there they are they have to be taken care of. For example, some of them are mentioned here Estonium cesium iodine. So, in conventional nuclear reactor taking care of nuclear waste which consists of minor actinides and fission products is a problem and that is why not many people are happy about it. So, to solve this problem in November 1993 Professor Carlo Rubia then Director General of Sun Geneva proposed a system which he called Thermal Neutron Energy Amplifier system based on Thorium cycle. So far we were using uranium cycle now he is proposing Thorium cycle and why it is very important to us that you will see in the next few slides. So, he proposed that you can use Thorium cycle for the energy production and that is called ADS why it is very important to India this can be seen here that although we have not much of uranium but we have highest amount of Thorium available in India and this is you can see here that India is having highest amount of Thorium and this is the latest report this is in thousands of tons. So, you can see almost like 1 million tons of that and these are the references for them. So, roughly almost like 16 to 17 percent of world's Thorium is in India and that is a very good quality. So, if we can use Thorium in our reactors then that is estimated that our fuel problem will be solved almost for 500 to 600 years. So, this is a very good and I think India should really work on it and then the system which why proposed by professor Carlo Rubia is called accelerator driven subcritical reactor system. Why it is important to have subcritical reactor because in conventional reactors producing power due to criticality safety issues are involved. While if it is subcritical then that problem will not come and it will be inherently safe. So, what he proposed was that you have a subcritical reactor and the external neutrons which are required they will be coming from outside and they are generated by the accelerator system. So, it is a new kind of fission reactor where nuclear power let us say just for example 500 to 1000 megawatt electrical can be generated in a neutron multiplying core and k effective here is less than 1. That means it is subcritical. So, this if k effective k effective is less than 1 it is subcritical if it is equal to 1 it is critical it is critical here it is subcritical and if it is more than 1 then it is supercritical. Now, this will be inherently safe if k effective is less than 1 k effective is shown here that means the production of neutrons is less than the absorption plus leakage. So, that means it will never become critical. Now, if it does not become critical then power generation will not take place. So, how to make it critical that means you have to provide extra neutrons from outside and that makes it critical, but now the control will become on the system which you are using from outside and that is what is ADS. So, the external neutrons come from the accelerator part. So, accelerator has to be driven by external neutron source. This is very important and that is what is done by the accelerator. So, neutron source requirement for ADS is given here. So, let us take one GEV a proton beam interactive with the heavy nuclei produces about 25 to 30 neutrons. Now, it is not a fission reaction it is a spallation reaction. So, each proton will generate about 25 to 30 and why it has to be about one GEV you will see next in the next slide. So, suppose for the sake of calculations you take 10 milli ampere beam current or 10 milli ampere one GEV becomes 10 megawatt. So, that is a beam power. So, this reaction can yield about 10 power 18 neutrons per second because each proton is creating 25 to 30 neutrons and these neutrons per second you will see here can generate the nuclear power of 500 to 1000 megawatt. So, if you take fission energy liberated in a neutron multiplying core k now it is a subcritical core then it is given by this formula 180 mvb is the energy released in each fission reaction. So, if you take k effective less than 1 and but of the order of 0.95 to 0.98 then the thermal fission power in the range of this would require driving neutron source of that and this is already there you have seen it can be generated there. So, that means with this one GEV proton beam of 10 milli ampere you can generate a nuclear power of about 1000 megawatt from where the 30 25 to 30 neutrons per proton comes it comes from here based on the calculations as well the experiment. So, you can see this figure where the number of neutrons generated per proton in a normalized manner as a function of proton energy you can see that around one GEV this is one GEV is about it saturates and it is around 25 to 30 in that range with other this is on the lead target but if you have other target it can be slightly more or less. So, you can see the on the average in a spallation process when the one at one GEV proton beam interacts with a heavy target like lead or bismuth then it will it will generate about 25 to 30 neutrons of course having a full spectrum. So, you have to moderate it and if you have that and these calculations were done at Fermilab and I have taken from this figure from invited talk given by Chanseh Khan Mishra in the impact 2005. Now in BRC also initiated this program as I said that for India it is absolutely of great importance to have an ideas program and there this is the accelerator of you can see here it will go about one GEV one GEV 30 milliampere in that proton beam will fall on a spallation target for the region to take away the heat it will be a liquid target. So, this is a spallation target here the spallation target and neutrons are produced and it is surrounded by a core of thorium and where the energy will be generated. So, you can see that detailed studies have been done on high current accelerator spallation target and reactor system and this program has started here. So, this accelerator will be developed at BRC in three phases first one will be 20 MBV low energy high intensity proton accelerator, second will be up to 200 MBV and at 200 MBV itself you can you can have a demo ADS for physics studies. However, the power can be generated with the one GEV accelerator. So, you can see that here this even the smallest this 20 MBV labor consists of several components and I am happy to tell you that this has been is almost about to be commissioned. However, this is this development of one GEV 30 milliampere current accelerator is difficult because higher currents there will be a lot of processes formed like is very difficult to contain that beam because of the space charge effect repulsive accelerator repulsive space charge effects and also the because of beam halo problems. But those problems can be solved and we are going ahead with that. Now, you can see here that why 30 I am talking about 30 milliampere so far and how that 30 milliampere comes whether can we reduce that because getting accelerators of that energy and the current are difficult as of now there is no high current accelerator operating in CW mode. So, you can see if you calculate that power thermal power generated using this current can see that for 1000 megawatt you need about 30 milliampere if you have k effective of 0.95. However, if you have 0.98 then it reduces to about 10 milliampere current. Similarly, if you want to generate in power of 3000 megawatts thermal then you need about 90 milliampere current with k effective of 0.95. But if you go to 98.98 then it reduces to about 30 milliampere current. So, if you want to have this kind of power generation which will be almost like about 1000 megawatt electrical then you need at least 30 milliampere currents. So, this comes from this formula for the power thermal power and the parameters which have been taken into account is that proton energy is 1 GV and number of newtons per proton is 25 and fission. In fission we are taken that there will be each fission there will be 2.5 newtons produced and we know that it is in the range of 2.2 to 3 newtons are produced per fission. To give you some numbers for reactors that is converting into electrical power with 40 percent efficiency to 280 megawatt. Then how it will be useful using aquarium you can take that this consists of three sub components which Karl Ruvia gave actually this is what he gave. You have an accelerator let us say it is about 1 GV 30 milliampere then it will be 30 milliampere 1 GV will be 30 megawatt and accelerator efficiency is about 50 percent you can call it. So, that means whatever power you are giving as input beam energy will be power will be about 50 percent of that. So, you have an accelerator where you are feeding about 60 megawatt power. So, you get 30 megawatt here and this is what you want the corresponding. So, when this beam falls on a target heavy target and that gives you about 25 times gain roughly that is because you are getting the. So, if you have 30 megawatt and roughly 20 gain you will get 600 megawatt that goes into the reactor and which has a conversion factor of about 40 percent from thermal to electrical. So, you get about 240 megawatt of electrical power out of that 60 will go to the accelerator and this system and 180 megawatt can be can go to grid. So, you will see that initially you have to feed power from outside later on it becomes like a self-sufficient independent system where power is generated and you can whole system can be given power from this and extra power. For example, in this case about 180 megawatt power is available to the grid. So, after sometime it becomes a self-sustainable system. Now also giving that what is the physics behind it and if it is a subcritical system you can see that multiplying multiplication in the subcritical reactor is given by this and the gain is given by this. This is for the subcritical system and if you take a typical value of G naught which is about in the range of 2.1 to 2.4 then you can see that K effective for 0.9 the gain will be 20 and for K effective 0.97 it will be 70 and so on and then the K effective 0.997 which is close to the critical one and which we should avoid then it will be 700. So, that means even little bit of fluctuation in parameters can make it unsafe. So, we should not use K effective of the order of 0.997. However, in this case which we are considering we are considering 1g proton energy on the lead target producing about 20 neutrons. We have seen it 20 to 30 in that range mid grid. So, typically let us say 40 percent of these neutrons will create fission reaction will have fission reaction that means out of these 8 neutrons will generate fission and each fission roughly gives about 0.2 GeV energy 180 MVV. So, roughly I am taking it about 0.2 then it will give it will generate 1.8 GeV. So, that means we started with a 1 GeV proton and it is giving energy of about 1.6 GeV. So, we have to keep these parameters in mind. So, with this order of magnitude calculation. So, with K effective of 0.98 the multiplication which becomes about 50 with all the parameters put in and it produces about 80 GeV energy. So, 1.6 into 50 becomes 80 GeV. So, the energy multiplication effectively in a subcritical reactor system based on the 1 GeV accelerator becomes about 80. Now, the beam power was 30 megawatt here and it is multiplied by 80. So, you can see that ADS power which is giving is about 2410 megawatt. So, this is order of magnitude these will exact calculations will involve the lot of other parameters. The biggest advantage of this is reduction in the minor actinides and see for example, for us it is very important to use thorium because it is a high abundance and it is the it is available in India in Plenty. So, therefore, at particularly it is 3 to 4 times abundant than the uranium right now all our reactors are using uranium and it is 3 to 4 times available. So, that means we have a lot of better fuel performance characteristics which are listed here you can see higher melting point, better thermal conductivity this is very important parameter and lower fission gas release. But most important is this parameter which is comparison of minor actinides produced in this thorium uranium cycle is that is much less as compared to this this cycle which is used in many reactors and that is shown here in this slide that the minor actinides production in thorium based cycle is you can relative values you can see here for example, in this one you can see that naptonium 237 which was produced in uranium fuels the uranium plutonium cycle 4.6 here it is only 0.06 is much less. Similarly, emerycium which was 4 here is minus 7 so it is almost like 0 and so therefore and these were the minor actinides which were responsible for that naptonium, emerycium, chemerium so these are the and these are not even produced so these are some of the very big advantage that means your problem of waste management is automatically solved. So, safety is taken care of that means the ADS systems are inherently safe because the reactor is subcritical, minor actinides are not produced and India it is abundantly available so this has tremendous advantage for all. So, thank you very much for this so this is the end of this course and I wish you good luck.