Rajasthan Atomic Power Station :

The Rajasthan Atomic Power Station (RAPS; also Rajasthan Atomic Power Project - RAPP) is located at Rawatbhata in the state of Rajasthan, India.

History :

The construction of the Douglas Point Nuclear Generating Station Canada began in 1961 with a CANDU (CANada Deuterium Uranium) pressurised heavy water reactor (PHWR) capable of producing 220 MW of electricity. Two years after construction of the Rajasthan Power Project (RAPP) commenced, with two similar reactors built in the state of Rajasthan. Ten years later, in 1973 RAPS-1 was put into service. In 1974 after India conducted Smiling Buddha, its first nuclear weapons test Canada stopped their support of the project, delaying the commissioning of RAPS-2 until 1981.

In the context of the Indian atomic program, two more PHWR with an output of 220 MW each were built. They cost around 570 million dollars. RAPS-3 became critical on 24 December 1999, RAPS-4 became critical on 3 November 2000. Commercial operations began on 1 June 2000 for unit 3, and on 23 December 2000 for unit 4.

Two more reactors (RAPS-5 and RAPS-6) with 220 MWe have also been built, with unit 5 beginning commercial operation on 4 February 2010, and unit 6 on 31 March 2010.

Two of the new Indian-designed 700 MWe series of reactor (RAPP-7 and RAPP-8) are under construction at Rajasthan. In November 2012, the International Atomic Energy Agency (IAEA) intensively audited over several weeks two reactors at the Rajasthan Atomic Power Station for safety. It has concluded that the reactors are among the best in the world, the indigenously made 220 MW atomic plants can withstand a Fukushima type of accident, even suggesting that the "safety culture is strong in India" and that India emerged a winner with a high global safety rank.

First concrete for unit 7 was poured on 18 July 2011, with commercial operation expected by 2016. The two reactors will cost an estimated Rs 123.2 billion (US$2.6 billion).

Background :

After India built it's first nuclear reactor in 1957, Prime Minister Jawarlal Nehru stated that the atomic revolution was inevitable, and India had to either go ahead with it, or fall back and fall behind. The nuclear power program had the political and financial backing of leaders in India. Today, India has an expanding and largely indigenous nuclear power program and expects to have 14.6 GWe nuclear capacity by 2024 and supply 25% of electricity from nuclear power by 2050.

The Indian nuclear program was developed to reprocess spent fuel to manage the back end of the fuel cycle. Nuclear waste has been a contentious aspect of nuclear power programs around the world. In India, the nuclear fuel cycle begins with mining and milling uranium and processing uranium into U3O8. The resulting spent fuel is reprocessed to recover uranium and plutonium. At each end stage of each cycle, different kinds of nuclear waste are produced. While the management of nuclear waste depends on the properties of the waste—radioactivity and other physical and chemical compounds—the guidelines for managing these aspects categorizes waste into four categories. India’s categories include Low-Level Waste, Intermediate-Level Waste, and High-Level Waste. The only PHWRs operating prior to 1982 have been RAPS-I and RAPS-II, which produced 1,59,079 MWeD of electricity from 1978 to 1982, and therefore would have produced 75.6 tons of spent fuel.

India started building nuclear power plants in the 1960s and continued to add more units progressively to meet the growing demand for electricity. Today, India has 14 operating nuclear power units with a total installed capacity of 2770 MWe. Starting the first unit in Tarapur in 1969, to commissioning of four units at Kaiga and Rajasthan in the year 2000, India has made significant advancements in this arena. The Rajasthan Atomic Power Station, or RAPS, is located in the Northern grid and has the country's largest nuclear power plant. It has six nuclear power reactors at present with the total installed capacity of 1,180 MW. Located in Rawatbhata, a remote village in the Chittorgarh district, RAPS I and RAPS I are the first two Indian Pressurized Heavy Water Reactors (PHWR).

The Pressurized Heavy Water Reactor (PHWR) Structure :

The common benefits of a PHWR include the use of natural uranium as fuel, which circumvents the need for developing fuel enrichment facilities. A country that has neutron rich economy by use of heavy water can benefit from building PHWR reactors due to low requirements of natural uranium both for initial core as well as for subsequent refueling. Additionally, in PHWRs, fissile plutonium production is higher than alternative reactors like Light Water Reactors.

The pressurized heavy water reactor is a horizontal pressure tube reactor using natural uranium dioxide fuel. Heavy water is the moderator and coolant which is maintained at low-pressure and temperature. Heat energy is then extracted by the coolant from the fuel, and is transferred to the secondary side light water to produce steam. Utilizing margin in the fuel linear heat rating and further flux flattening enhances the power output of the reactor. Extraction of additional heat is achieved by allowing boiling of coolant near the channel exit. In fact, the same reactor assembly and primary coolant loop are capable of delivering thermal energy equivalent to 700 MWe.

Safety Issues :

Safety and reliability of a nuclear power plant are of utmost importance requiring constant vigilance by all the concerned agencies. Most of the structures, systems and components of nuclear power plants in India are continuously under varying influence of material degradation due to neutron irradiation, dynamic stresses, thermal fatigue, creep, corrosion, erosion, wear, vibration, and more. The maintenance of these systems, structures and components in Rajasthan plays an important role in assuring their safe and reliable operation. In PHWRs, the liquid wastes originate mainly at the following points: personnel showers, active laundry; heavy water upgrading plant, reactor building sump, heavy water cleanup rooms (tritiated waste); laboratories and decontamination center as active chemical waste. Liquid waste generated at the plant is collected in tanks at the Liquid Effluent Segregation System, which is located in the service building. Subsequently, the waste is pumped to the Treatment and Disposal System of the Waste Treatment Plant, which is equipped with facilities for chemical treatment, purification by ion exchange, evaporation, and more. After treatment of liquid waste, sampling and monitoring is diluted with condenser cooling water/blow down water and discharged to the environment water body through a single point.

RAPS I and II PHWRs have had various safety issues. Turbine blade has been one common issue. In 1981, RAPS I was shut down twice because of oil leakage in the turbine building. This leakage led to high levels of sparking in the generator exciters; after the initial shut down, it was later found that large amounts of oil had leaked form the turbine governing system. Later after reopening, it was discovered that there were high vibrations of the turbine bearings and the blades were failing; the ensuing shutdown and repair of the plant took another five months. In 1983 it was discovered that the temperatures were too high in the turbine bearing, and two plates in the second stage of the high-pressure rotor had sheered off at the root. RAPS I was further shut down in 1985, 1989, and 1990. In May 1998, titriated heavy water with levels of tritium above levels set by the AERB (Atomic Energy Regulatory Board) was released from RAPS II into the Rana Pratap Sagar Lake; the release was due to a leak in the moderator heat exchanger. However, the public did not know about this occurrence until December 1999. Yet, some upgrades have occurred in recent years. As part of the replacement of the pressure tubes in RAPS II, significant upgrades were performed to bring the safety systems to current standards. These include changing the containment dousing system with a fixed dousing flow rate, an enhanced Emergency Core Cooling System, the addition of a supplementary control room, a modification to the air flow valve system to minimize instrument air in-leakage in containment, and improvements to the station electric power supplies with a third diesel generator.

Incidents :

By 2003 RAPS-1 had experienced numerous problems due to leaks, cracks in the end-shield and turbine blade failures, had undergone repairs and appeared to be generating 100 MW electricity, with RAPS-2 reportedly generating 200 MW.

On 29 August 2006, a 90% iron meteorite weighing 6.8 kilograms fell in Kanvarpura village, near the power station. The Deputy Director-General (western region) of the Geological Survey of India, reported that devastation on an "unimaginable scale" would have ensued had the object struck the station.

In June 2012, 38 workers were exposed to tritium when a welding operation went wrong inside the protected environment of the reactor.