Nuclear Energy and Why We Need It

Energy Today in India Nuclear Energy and Why We Need It Vinay B Kamble vinaybkamble@gmail.com India occupies 2 per cent of the world s land mass and currently generates about 2 per cent of the global electricity; and yet has a share of 16 per cent of the world s population. Our annual per capita consumption of electrical energy is only about 787 kwh! For China it is 3,107 kwh, while for USA it is 14,218 kwh! Incidentally, 1 kilowatt hour (kwh) is also called 1 unit of electrical energy on which are based our monthly electricity consumption bills. India s total installed capacity as of today is 2,25,800 megawatts of electricity. However, to achieve even a modestly high level of economic growth, the domestic generation capacity will need to be increased at least tenfold in the coming few decades, say, by 2051. At present, thermal sources (coal, gas and oil) provide nearly 68 per cent of electricity, while hydroelectric sources provide 18 per cent of our energy requirements. About 12 per cent of our electrical energy comes from renewable energy sources, while nuclear sources provide for only about 2 per cent of our requirements. Although the contribution of nuclear energy to power sector today is quite modest, it is destined to play a crucial role in meeting India s energy requirement in coming decades. Increased availability of electricity is necessary for the progress of any developing country like India. However, mere availability alone is not a sufficient criterion. It also must provide for a long term energy security, should be sustainable and based on diverse fuel sources and technologies. We must, therefore, examine all fuel resources in the country and tap them keeping short, medium and long term scenarios in perspective. Surely, hydro and renewable sources and technologies must be exploited to the maximum. These, together with coal would meet our short and medium-term requirements. Long-Term Requirement But, even with full utilization of all existing commercially exploitable domestic hydrocarbon, hydroelectric and nonconventional resources, an increased level of generation capacity cannot be sustained for more than a few decades. How do we meet our long-term energy requirements, then? It is the nuclear resources we shall need to tap. True, our uranium resources are modest, but thorium resources are vast. This is a situation unique to India. Hence, our energy programme has to be on different lines as compared to other countries, where uranium resources are relatively large or readily accessible from different parts of the world. For sure, India s three-stage nuclear power programme (to be described later) takes cognizance of the nuclear resource profile of our country. Nuclear Energy How it is produced Nuclear energy is released when nuclei of heavy atoms like uranium absorb a neutron and break up into smaller fragments. This process is known as fission. During the process, 1

some mass disappears and turns into energy given by Einstein s famous formula E= mc 2, where E is the energy produced, m is the mass that is converted into energy and c is the velocity of light. If all atoms of 1 kg of uranium undergo fission, they would produce energy equivalent to that produced by burning 3,000 tonnes of coal! When one uranium nucleus is split, two or three neutrons are liberated, which in turn split more uranium nuclei and liberate more neutrons, and so on. This is what is called a chain reaction. In nuclear bombs like the ones that destroyed Hiroshima and Nagasaki, this chain reaction goes uncontrolled, resulting in a huge explosion. In a nuclear reactor used for power generation the chain reaction is controlled by absorbing most of the released neutrons, and allowing only some neutrons to cause fission. The energy generated in a fission reaction in the form of heat can be used to produce steam and run turbines to generate electricity. The Catch But, here lies the catch! Not all atoms of uranium can be split by neutrons! In nature, we find uranium atoms of two types - lighter uranium isotope with 92 protons and 143 neutrons (denoted by symbol U 235 ) and heavier uranium isotope with 92 protons and 146 neutrons (denoted by symbol U 238 ). Only the U 235, present to the extent of about 0.7 per cent by weight in ordinary uranium, is fissile (that is, it can undergo fission), and hence, for use in a nuclear reactor, uranium needs to be enriched so that it contains a higher percentage of U 235 isotope to sustain chain reaction. Enrichment, however, is a complex and an expensive process. In such reactors, however, we need to use boiling water or graphite as moderators to slow down the speeds of the neutrons so that they can hit the U 235 isotopes and split them. When ordinary water (H 2 O) is used as moderator, the reactor is called Light Water Reactor (LWR). Protons in the light water molecule, however, have a tendency to absorb the neutron, and thereby decrease the rate of the chain reaction. Enriching uranium with U 235 isotope helps overcome this disadvantage by making more U 235 isotopes available for fission reaction. Using Natural Uranium To get around the complex and expensive process of uranium enrichment, Canada developed CANDU reactors that use natural uranium (containing both U 235 and U 238 isotopes), but use pressurized heavy water as moderator. Incidentally heavy water has hydrogen atoms with one proton and one neutron in the nucleus of hydrogen atom (denoted by D 2 O), while ordinary water has hydrogen atoms with only a proton as its nucleus (denoted by H 2 O). There is one distinct advantage in using Pressurized Heavy Water Reactors (PHWRs). Heavy water reacts dynamically with the neutrons in a similar fashion to light water (albeit with less energy transfer on average, given that heavy hydrogen, or deuterium is about twice the mass of hydrogen), it already has the extra neutron that light water would normally tend to absorb. Energy is, of course, produced by the fission of U 235 nuclei, but some of the U 238 nuclei are converted to plutonium nuclei with 90 protons and 149 neutrons (denoted by Pu 239 ), which is fissile. Hence, the spent fuel from PHWR can be reprocessed and Pu 239 separated which can be utilized as fuel in the second stage reactor. Surely, a few of U 238 nuclei do get converted to Pu 239 in LWRs as well that use enriched uranium as fuel. As of December 2013, India had 21 nuclear reactors in operation producing 5,780 megawatts of electricity, two of which are LWR type using enriched uranium while the rest are PHWRs based on CANDU design using natural uranium as fuel. The Latest has been the Kudankulam 2

nuclear power plant commissioned in October 2013, which is of Russian design, and is a water-cooled-water-moderated light water reactor. Breeding Nuclear Fuel India has only about 61,000 tonnes of uranium. But thorium (90 protons and 142 neutrons denoted by Th 232 ) resources are vast - some 2,25,000 tonnes. Although Th 232 by itself is not fissile, it can be converted to a uranium isotope U 233 by bombarding with neutrons in a nuclear reactor. Now, U 233 is fissile, and can be used as fuel in another reactor that predominantly uses this isotope of uranium. Surely, the long-term goal of India s nuclear program is to develop an advanced heavy-water thorium cycle. India s 3-stage nuclear programme employs in its first stage the PHWRs fuelled by natural uranium, and light water reactors, to produce plutonium along with power. Stage 2 uses fast neutron reactors, also called Fast Breeder Reactors (FBRs), burning the plutonium to breed U 233 from thorium. The blanket around the core will have uranium as well as thorium, so that further high-fissile plutonium is produced as well as the U 233. Then in stage 3, Advanced Heavy Water Reactors (AHWRs) would burn the U 233. India - A World Leader in Thorium Technology India s civil nuclear programme has progressed at a relatively slow pace as it is not a signatory to the Non-Proliferation Treaty (NPT). Incidentally, NPT is a treaty to limit the spread of nuclear weapons. There are currently 189 countries party to the treaty, five of which have nuclear weapons. India did not sign the treaty as it considered it was biased towards the five nuclear weapon states (USA, UK, France, Russia, and China). As a result, India did not have access to nuclear resources or technology available elsewhere in the world. But, this has proved to be a blessing in disguise. Today, India is considered a world leader as regards thorium technology which is still under development. The nuclear weapons capability of India has arisen independently of its civil nuclear fuel cycle and uses indigenous uranium. Because of its relative isolation in international trade and lack of indigenous uranium, India has uniquely been developing a nuclear fuel cycle to exploit its reserves of thorium. Flourishing Nuclear Programme India has a flourishing and largely indigenous nuclear power programme and expects to have a nuclear capacity to produce 20,000 megawatts of electricity by 2020, subject to an opening of international trade. India is already in the process of constructing 6 power reactors, 4 of which are PHWRs and 2 pressurized water reactors through an agreement with Russia. Incidentally, Unit-1 of the Kudankulam nuclear power plant in Tamil Nadu, India s first 1000 MW pressurized water reactor, attained criticality on 13 July 2013; and is the 21st nuclear power reactor in the country. Another 6 are under construction and 27 planned. According to a study by the Department of Atomic Energy, if we import nuclear reactors / fuel that would allow us to produce additional 20,000 megawatts of electricity by 2020 (that is, a total of 40,000 megawatts of electricity), the reprocessed plutonium to be used in FBRs would allow India to be self-sufficient in energy by 2050. Our 3-stage nuclear programme, however, would forge ahead unhindered. Riding the Nuclear Tiger 3

Electricity was first generated from a nuclear plant in 1951 at Idaho, USA. Today there are 437 nuclear power plants in the world producing about 375,000 MW of electric power in 31 countries, equivalent of nearly 20 million barrels of oil per day! Yet, nuclear energy needs to be handled carefully. Otherwise, breakdowns could occur putting large populations at risk. In March 1979, failures in its cooling system disabled one of the reactors in Three Mile Island in Pennsylvania, USA, and a certain amount of radioactive material escaped. This incident made it clear that the hazards associated with nuclear energy are real. In April 1986, a severe accident destroyed a 1000 MW reactor at Chernobyl in Ukraine, then part of the Soviet Union. This was the worst environmental disaster of technological origin in history and contributed to the collapse of the Soviet Union. Over 50 tonnes of radioactive material escaped and was carried around the world by winds. The radiation released was about 200 times the total given off by the Hiroshima and Nagasaki atomic bombs in 1945. A number of people engaged with reactor, rescue and clean-up operations died soon after as a result of exposure to radiation, and thousands more became ill. Contamination with radionuclides, particularly with food and water, raised the total number of people affected manifold. The Fukushima Daiichi nuclear disaster in Japan was an accident at the Fukushima I nuclear power plant, initiated by the great tsunami of the Tohoku earthquake on 11 March 2011. The damage caused by the tsunami produced equipment failures. As a result, there was loss of coolant, which caused nuclear meltdown; and then release of radioactive materials. It is the largest nuclear disaster since the Chernobyl disaster releasing 10 to 30 per cent of the radiation of the Chernobyl accident. As a result, public anxiety over the safety of nuclear reactor programmes grew all over the world. Some countries, for instance Germany, abandoned plans for new reactors and have even started phasing out the existing ones. Even in India, there have been massive protests for construction of nuclear reactors at Jaitapur in Maharashtra and Kudankulam in Tamil Nadu. The plants in Kudankulam have built in safety measures and are considered quite safe even in the event of a great tsunami, or possible technical failures. Handling nuclear energy is like riding a tiger! We shall need to learn it! We do not have much choice, anyway! Nuclear Waste: Where to Dump? Apart from the safety of the nuclear reactors themselves, there is an issue of what to do with the waste they produce. Even if old fuel rods are processed to separate out the uranium and plutonium they contain, what is left is still radioactive. Some of the radionuclides have half-lives in millions of years. Burying nuclear waste deep underground currently seems to be the best long-term solution to dispose of them. Only problem is the right location! It is easy to specify but difficult to find! It should be geologically stable, with no earthquakes likely, no nearby population centres, a type of rock that does not disintegrate in the presence of heat and radiation, but easy to drill into, and not near groundwater that could become contaminated! A Strong Case for Nuclear Energy 4

Despite the hazards associated with atomic energy, it has important advantages that need to be appreciated. It does not produce the air pollution that burning of fossil fuel does, nor the huge quantities of carbon dioxide that are major contributors to global warming as a result of the greenhouse effect. With the rising cost of fossil fuels and increasing demand for electricity, these factors seem likely to lead to the construction of new nuclear reactors. Indeed, this makes a strong case for nuclear energy in our country. Innumerable Applications Nuclear energy does not imply nuclear reactors and nuclear weapons alone! It is safe, environmental-friendly, and has innumerable applications in fields as diverse as health and medicine, industry, hydrology, food preservation, and agriculture. We may note that in the field of nuclear agriculture, the mutant groundnut seed developed at the Bhabha Atomic Research Centre (BARC), contributes to nearly 25 per cent of total ground-nut cultivation in the country. Similarly, the BARC developed mutant seeds of black gram (urad) contribute to 22 per cent of the national cultivation. In the state of Maharashtra, this percentage is as high as 95 per cent. In particular, so far as the future energy needs and economic development of our country are concerned, nuclear energy is bound to prove extremely beneficial to our country in the decades to come. Surely, we have come a long way since the discovery of the nucleus by Ernest Rutherford in 1911 and the discovery of the atomic structure by Niels Bohr in 1913. ****** 5