Discussion with Dr.Anil Kakodkar Part-3

Q: How can we calculate the power output or the efficiency of a nuclear reactor?

A:  Well, it is the other way around. You design a nuclear reactor to generate a given power. You can design a nuclear reactor for any amount of power. Here one important part is that you must assign a critical mass, because you have to sustain chain reaction and only then the energy production can be continuous. Otherwise it will be like a pulse; you create a condition, it will generate some energy but then it will not sustain. So, you must have a chain reaction and to sustain chain reaction you must have critical mass. Hence, you must configure the fissile material, the moderator and the cooling systems in a manner that you have a critical mass. Once you have assembled a critical mass, then you decide how much power you want to extract. And depending on how much power you want to extract you have to incorporate the heat removal systems. These can be the heat exchanger will require a certain surface area, or a heat removal pump or other heat transfer equipment or mass transfer equipment; similarly there are design principles for nuclear thermal hydraulics. 

I’ll not go into details there. One factor being critical mass and the second being the capability to extract heat decides the energy density or the power density. There are techniques of extracting very large power from very small volume. And that’s one technology. There are also to extract as much heat as you can remove using the standard modes of heat removal. But, that will again decide how much volume you want and then you assemble that critical mass. Then you have to worry about the controllability. 

There are some PHW reactors that we use in our country which are on power refueling, wherein you keep on feeding the fuel and it keeps burning. There are other reactors where you carry out refueling of power. It sense that you shut down the reactor; you put in new fuel and then again run for 1 year or 2 years depending on the design. But, then depending on how much extra fuel you have put, you have to keep it exactly at criticality, so you have to have control elements; you have to calculate the controllability of the reactor. So, you design it to extract a given power for which you want to build the reactor

Q: Sir, we now know that Solar Energy is efficient enough to run airplanes, can you tell us more about it in detail?

A: You have rightly spoken. As I was earlier talking about nuclear waste, I also told you why we need nuclear energy. But, I also mentioned that re-cycling is an important aspect of sustainability. Now, renewable energy is a source that we don’t recycle, but nature recycles. For example, Hydro-energy, the water cycle continues all you have to do is build dams and manage it to get energy. Solar Energy works in a similar manner. The sun shines and if you can absorb that energy and use it later, it gives you a lasting source of energy. Fortunately we have the availability of Solar Energy in India is appreciable. So the thought is to use renewable energy to solve our energy requirement.

 To encourage the use of Solar Energy the government established a company and it was named Solar Energy Corporation and I was asked to join it because we had achieved considerable success in achieving self reliance in nuclear energy sector. It is very necessary to attain technological self-reliance for solar energy as well. Because of encouragement solar energy has received huge acceptance in India and especially in Gujarat there is some great work done and is being done. But, if you take a close look you will find that most of the technology used is foreign. 

Now one may wonder that what the problem be if the technology is foreign. The reason is that if solar energy is to become a large part of our energy production, and if the technology & the resources are made in the country itself, the wealth of the nation remains within the nation. It would employ our people and boost our economy. The basic material of a solar cell itself is made outside India. Currently we bring the solar cells from abroad and assemble it here, even which is not entirely done here. Now, it so happens that it might be expensive to make it here and cheaper to import it from, say China, where it is produces in bulk. So, this is the challenge we face between these two decisions. I believe that on one hand that we should encourage R & D for solar energy, so that we can attain self-reliance. Now, we import both solar thermal & photovoltaic from abroad. But, solar thermal is more expensive and hence is less popular. But, I believe that we can attain domestic self-reliance in solar thermal quicker as compared to photovoltaic. But, if we want to do that, we have to design a proper strategy. In case of photovoltaic, the efficiency does not increase with the scale whereas in solar thermal the efficiency increases at least by 2 times. 

This means that capital costs per MW becomes half. And this technology is well within our reach. I believe that we have to make people understand, including the decision makers that we create demonstrations where people actually see, that what I am saying is true and encourage sentiment for investment in solar thermal. And if we invest there, the objective of retaining and growing wealth within the country on the basis of solar energy can be much easily reached. That’s what we should do in my view. 

That does not mean that photovoltaic should be ignored, I think makes a good economic case and we should continue that development because that is obviously economically more beneficial. I find that in the R & D community also we are more driven by the so called fashionable approaches. So we if we see that US is trying to get the efficiency of solar cells to 30% we also get into that, which is not bad. But, our 100% attention is on following, we will be followers of the world. If you copy somebody’s work, theoretically at best you can be a good number 2. 

If we have to be number 1 we have to think originally, don’t get driven by what others are doing. Co-operating with others understanding what they are doing is a good thing, we should not close our minds. But, this copying tendency has to stop. I think a very large number of us, we suffer from it.