NUCLEAR ENERGY FOR COMMERCIAL USE
S.K ANSARI, SEEMA ANSARI
Oct 18 - 24, 2010
In 2002 nuclear power - which is used almost exclusively to produce electricity in the commercial application ñ generated some 2700 TWh (terawatt hours) of electricity power, representing about 17 per cent of the world's electricity consumption.
Today, some 440 commercial nuclear reactors are operating in 30 countries with over 360,000 megawatt of total production capacity. Currently, the United States has 104 commercial nuclear power plants accounting for 20 per cent of the electricity generation. In Western Europe, nuclear energy generates around 35 per cent of the electricity; more than from any other source. France and Belgium, for example, produce 78 per cent and 55 per cent apiece of electricity through nuclear power. Other industrialised countries with limited or no fossil fuel resources such as Japan and South Korea also rely heavily on nuclear energy for meeting their electricity needs.
WORLD'S NUCLEAR ENERGY SHARES
All commercial nuclear plants presently use uranium as fuel. Uranium is a slightly radioactive metal that occurs naturally throughout the earth's crust. It is about 500 times more abundant than gold, and as common as tin, tungsten, or molybdenum. Uranium is originally formed in stars, which at the end of their life exploded with some of their shattered dust aggregating together to form our planet. Uranium is present in most rocks in concentrations of 2 to 4 parts per million (ppm). In phosphate rocks used as fertilisers, its concentration can be as high as 400 ppm, while some coal deposits have uranium concentrations in excess of 100 ppm. Uranium is also discovered in seawater at a concentration of 3 to 4 ppm. There are, however a number of areas where the concentration of uranium is much higher and economically exploitable. These deposits are particularly important in Australia and Canada, which are therefore currently the largest uranium producers in the world. Some Canadian deposits contain more than 100 kg of uranium per ton of raw ore. Like coal, uranium has to be mined in underground or surface mine depending on the depth at which the deposit is located. It is then sent to the mill where the ore is crushed to powder and leached with a strong acidic or alkaline solution to extract the uranium from the rock. By precipitation from this solution, uranium oxide (U2O3) power referred to as "Yellow cake" (because of the color) is obtained. Natural uranium consists of a mixture of two isotopes: uranium 235 (235U) and uranium 238 (238U). Only the isotopes 235U, which represents merely 0.7 per cent of the natural uranium, is capable of undergoing fission, the process by which energy is generated in nuclear reactors. Even if some reactors are available to use natural uranium to produce energy, the vast majority of them require a higher concentration in 235U. Thus, it is necessary to enrich uranium from its original concentration in 235U of 0.7 per cent to typically 3 - 5 per cent.
For this enrichment process to occur, the uranium must be in gaseous form, and this is carried out by conversion into uranium hexafluoride (UF6), which is a gas at relatively modest temperature (solid UF6 sublimes at 56∞C).
MILESTONES IN THE HISTORY OF NUCLEAR ENERGY
The world's first commercial-scale nuclear power plant was opened in 1956 in the United Kingdom. It was equipped with Magnox reactor using graphite as moderator and Co2 gas as coolant. It used, like Fermi's reactor, non-enriched natural uranium containing only 0.7 per cent 235U. In the United States, the first commercial nuclear power began operation in 1957 in shipping port, Pennsylvania. It was a so-called pressurised water reactor (PWR), which is still the technology used in 60 per cent of the plants currently in operation worldwide. The heat generated by the fission reaction is used to heat water in which the fuel rods are immersed. Reaching temperatures of around 300∞C, the water, however, does not boil because it is kept under high pressure. The pressurised water serves both as a moderator and coolant. Via a heat exchanger, it is used to boil water in a secondary loop, producing steam to propel a turbine which in turn spins a generator to produce electric power.
The second most common type of nuclear reactor is the boiling water reactor (BWR), with more than 90 units operating worldwide. The design of the BWR has many similarities with PWR, except that the water cooling the core is allowed to boil and steam generated is used directly to drive turbines. After condensation, the water is returned to the reactor to close the cycle. This system has a simple design than the PWR, but as the water around the core is contaminated with trace of radioactive material, although generally with a short half-life the turbine must be shielded in order to avoid the escape of radiation. For safety reasons, PWRs are thus the preferred reactors in the Western World. In France, for example, all 58 reactors in operation are of the PWR type.
Both the PWR and BWR, representing together more than 80 per cent of the commercial nuclear reactors worldwide, are light water (H2O) moderated and use uranium enriched at 3 ñ 5 per cent in fissile 235U isotopes. The commercial reactors used today are PWR and BWR, which were considered as the second generation technology during the era from 1970s to 2000.
Currently, the transitions to the third generation of reactors are under way. Two units have already been completed in Japan, and several others are under construction or planned in countries such as Taiwan, France, or Korea. They are an evolution from the second-generation reactors, but feature enhanced safety systems are less expensive to build, maintain, and operate. At the same time, revolutionary designs known as generation IV systems, which have new and innovative reactor or fuel cycle systems are well under development.
Most of the commercial reactors currently in operation use enriched uranium in a once-through cycle. This means that the uranium is used only once and must be disposed of. This cycle is the most uranium reserve-intensive, as only 235U contributes by fission to the production of energy. 235U, which constitutes up to 97 per cent of the fuel, and 99.7 per cent of natural uranium is left almost untouched. The solution to limit this waste of resources is to use a different fuel cycle. In the typical reactor, fast neutron are slowed down by moderators to increase the probability of collision between these slow neutrons and the fissile 235U nucleus, and thus increase the amount of energy generated by fission.
Even more intriguing is the possibility of actually producing more fuel than is consumed, using the breeder reactor. In this reactor, which is based on fast neutrons, more fissile material is produced through the conversion of 238U into 239Pu than is consumed through fission. As fast neutrons are desired, no moderator is necessary in this type of reactor. Several fast breeder reactors have been constructed over the years in the number of countries. The best known are France's "Phenix" and "Superphenix" reactors. Phenix is an experimental reactor with a power capacity of 250 MW. Its successor, Superphenix, was a commercial scale reactor that was connected to the grid and had a capacity of 1300 MW, but it was closed down in 1997, after some technical problems, but mainly for administrative and political concerns.
In Russia, Japan, and India, breeder reactors are well under development with several units under construction. The United States, which pioneered this field with construction of the first breeder reactor in 1951, is now reconsidering this technology for future power plants.
In fact, the United States initiated in 2000 the Generation IV along with nine other countries aimed to determining and developing the most promising generation IV reactor designs that can provide future worldwide needs for electricity, and also produce hydrogen and other products. Among the six selected systems, three are fast-neutron reactors, which are all operated in a close fuel cycle, meaning that the fuel is recycled.
NUKE POWER PLANT IN PAKISTAN
In Pakistan, nuclear power makes a small contribution to total energy production and requirements, supplying only 2.34 per cent of the country's electricity.
The Pakistan Atomic Energy Commission (PAEC) is responsible for all nuclear energy and research applications in the country. Its first nuclear power reactor is a small (125 MW) Canadian pressurised heavy water reactor (PHWR) which started up in 1971 and which is under international safeguards - Kanupp near Karachi, which is operated at reduced power.
The second unit is Chashma-1 in Punjab, a 325 MW (300 MW) pressurised water reactor (PWR) supplied by China's CNNC under safeguards. Shanghai Nuclear Engineering Research and Design Institute (SNERDI), based on Qinshan-1, designed the main part of the plant. It started up in May 2000 and is also known as Chasnupp-1.
Construction of its twin, Chashma-2, started in December 2005. It is reported to cost Rs51.46 billion (US$ 860 million, with $350 million financed by China). A safeguards agreement with International Atomic Energy Agency (IAEA) was signed in 2006 and grid connection is expected in 2011.
PAKISTAN NUCLEAR POWER REACTORS
REACTOR TYPE MW NET CONSTRUCTION START COMMERCIAL OPERATION Karachi PHWR 125 1966 12/1972 Chashma 1 PWR 300 1993 6/2000 Chashma 2 PWR 300 2005 expected 2011 Total 425 operating . . .
INDIA NUCLEAR POWER
India has a flourishing and largely indigenous nuclear power program and expects to have 20,000 MW nuclear capacity on line by 2020 and 63,000 MW by 2032. It aims to supply 25 per cent of electricity from nuclear power by 2050.
INDIA'S OPERATING NUCLEAR POWER REACTORS
REACTOR STATE TYPE MW NET COMMERCIAL OPERATION SAFEGUARDS STATUS Tarapur 1 & 2 Maharashtra BWR 150 1969 item-specific Kaiga 1 & 2 Karnataka PHWR 202 1999-2000 . Kaiga 3 Karnataka PHWR 202 2007 . Kakrapar 1 & 2 Gujarat PHWR 202 1993-95 in 2012 under new agreement Kalpakkam 1 & 2 (MAPS) Tamil Nadu PHWR 202 1984-86 . Narora 1 & 2 Uttar Pradesh PHWR 202 1991-92 in 2014 under new agreement Rajasthan 1 Rajasthan PHWR 90 1973 item-specific Rajasthan 2 Rajasthan PHWR 187 1981 item-specific Rajasthan 3 & 4 Rajasthan PHWR 202 1999-2000 early 2010 under new agreement Rajasthan 5 & 6 Rajasthan PHWR 202 Feb & April 2010 Oct 2009 under new agreement Tarapur 3 & 4 Maharashtra PHWR 490 2006, 05 . Total (19) . . 4183 MW . .
URANIUM SUPPLY TO INDIA
The two Tarapur 150 MW BWRs built by General Electric on a turnkey contract before the advent of the nuclear non-proliferation treaty were originally 200 MW. They were down rated due to recurrent problems but have run well since then. They have been using imported enriched uranium and are under IAEA safeguards. However, late in 2004 Russia deferred to the nuclear suppliers' group and declined to supply further uranium for them. They underwent six months refurbishment over 2005-06, and in March 2006 Russia agreed to resume fuel supply. In December 2008, a $700 million contract with Rosatom was announced for continued uranium supply to them.
The two small Canadian (Candu) PHWRs at Rajasthan nuclear power plant started up in 1972 & 1980, and are also under safeguards. Rajasthan-1 was down-rated early in its life and has operated very little since 2002 due to ongoing problems and has been shut down since 2004. Rajasthan-2 was restarted in September 2009 after major refurbishment, and running on imported uranium at full rated power.
The new Tarapur 3&4 reactors of 540 MW gross (490 MW net) are developed indigenously from the 220 MW (gross) model PHWR.
The first - Tarapur 4 - started up in March 2005, was connected to the grid in June and started commercial operation in September. Tarapur-4's criticality came five years after pouring first concrete and seven months ahead of schedule. Its twin - unit 3 - was about a year behind it and criticality was achieved in May 2006, with grid connection in June and commercial operation in August, five months ahead of schedule.
Future indigenous PHWR reactors will be 700 MW gross (640 MW net). The first four will be built at Kakrapar and Rajasthan.
Russia is supplying all the enriched fuel, though India reprocesses it and keeps the plutonium.
INDIA'S NUCLEAR POWER REACTORS UNDER CONSTRUCTION REACTOR TYPE MW NET PROJECT CONTROL COMMERCIAL OPERATION DUE SAFEGUARDS STATUS Kaiga 4 PHWR 202 MW NPCIL 5/2010 . Kudankulam 1 PWR (VVER) 950 MW NPCIL 12/2010 Item-specific Kudankulam 2 PWR (VVER) 950 MW NPCIL mid 2011 Item-specific Kalpakkam PFBR FBR 470 MW Bhavini 9/2011, or 2012 - Total (4) . 2572 MW . . .
Following the nuclear suppliers' group agreement, which was achieved in September 2008, the scope for supply of both reactors and fuel from suppliers in other countries opened up. Civil nuclear cooperation agreements have been signed with the USA, Russia, France, UK and Canada, as well as Argentina, Kazakhstan, Mongolia and Namibia.
In US, the average capacity factor of nuclear power plants increased from 58 per cent in 1980 to 70 per cent in 1990, and close to 90 per cent in 2005. The increased capacity factor resulted in lower generation costs and an increased electricity production using nuclear power. The increase in electricity production from 1990 to 2005 was the equivalent of adding more than 20 new nuclear reactors.
ECONOMICS OF NUCLEAR ENERGY
Surprisingly, in some way anti-nuclear activism has also a positive long-range influence on nuclear energy. It forces energy companies and governments under much higher public scrutiny to make nuclear power plants even safer and more productive and reliable than almost any other industry.
SAFETY WITH NUCLEAR PLANT
Nuclear power plants are closely regulated by national and international agencies, which provide rigorous oversight of the operation and maintenance of these plants. The safety record of nuclear power plants has been exemplary over the years. This was achieved through improved plant design, high quality construction, regular staff training, safe operation, and carefully emergency planning. Diverse and redundant systems prevent accidents from occurring, and multiple safety barriers are placed to mitigate the effect of accidents in the highly unlikely event they occur. The safety of the nuclear industry has been significantly imposed since the Three Mile Island incident in 1979 which, although it was the most serious nuclear accident in the Western World, did not lead to any casualties.
Unstable atomic nuclei can split to form other particle, ejecting at the same time different types of radiation (alpha, gamma, beta and X-ray) in a process called radioactivity. These radiations are able to penetrate matter and can disrupt biological systems and thus essential processes in human body cells. The degree of penetration will depend on the energy of the radiation, with gamma and X-rays being the most energetic. Today, radioactivity is a part of our daily life, and is present every where from various natural sources: cosmic rays, uranium and thorium contained in the earth crust, granite used as a construction material, radon gas produced by the natural decay of uranium, potassium in fertilisers and food etc.
The cost of nuclear power in US is $0.03 kWh, which is equivalent to Pak Rs2.55/kWh. Here in Pakistan, electricity consumer an average pays Rs13/kWh that is increasing day by day. The cost of producing electricity from nuclear plants including fuel, operation, and maintenance has been declining over the past decade. Therefore, the government should start thinking on this line to develop and expedite developments of nuclear plants for some economic benefits.