History of CANDU Nuclear Reactor in India

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CANDU Reactor Technology

The CANDU (Canada Deuterium Uranium) is a Canadian pressurized heavy-water reactor design used to generate electric power. The acronym refers to its deuterium oxide (heavy water) moderator and its use of (originally, natural) uranium fuel. CANDU reactors were first developed in the late 1950s and 1960s by a partnership between Atomic Energy of Canada Limited (AECL), the Hydro-Electric Power Commission of Ontario, Canadian General Electric, and other companies.

There have been two major types of CANDU reactors, the original design of around 500 MWe that was intended to be used in multi-reactor installations in large plants, and the rationalized CANDU 6 in the 600 MWe class that is designed to be used in single stand-alone units or in small multi-unit plants. CANDU 6 units were built in Quebec and New Brunswick, as well as Pakistan, Argentina, South Korea, Romania, and China. A single example of a non-CANDU 6 design was sold to India.

In February 1960, it was decided the first power plant would be erected in Western India, with locations in Rajasthan, near Delhi and near Madras noted for future commercial reactors. In September, the Punjab government requested a nuclear power station for their state. On 11 October 1960, the Indian government issued a tender for India’s first nuclear power station near Tarapur, Maharashtra and consisting of two reactors, each generating around 150 MW of electricity and to be commissioned in 1965. In August 1961, the Indian and Canadian governments agreed to conduct a joint study on building a Canada-India nuclear power plant in Rajasthan; the reactor would be based on the CANDU reactor at Douglas Point and would generate 200 MW of energy. By this time, seven responses to India’s global tender for the Tarapur power station had been received: three from the United States, two from the UK and one each from France and Canada.

The agreement for India’s first nuclear power plant at Rajasthan, RAPP-1, was signed in 1963, followed by RAPP-2 in 1966. These reactors contained rigid safeguards to ensure they would not be used for a military programme. RAPP-1 began operation in 1972. Due to technical problems the reactor had to be downrated from 200 MW to 100 MW. The technical and design information were given free of charge by Atomic Energy of Canada Limited(AECL) to India. The United States and Canada terminated their assistance after the detonation of India’s first nuclear explosion in 1974.


CANDU & India’ Indigenous PHWR

With the launching of the RAPP-1 project, the Indians wished to proceed quickly with a second unit, RAPP-2. Agreement was eventually reached between AECL and the DAE to proceed with RAPP-2 despite further difficulties regarding the non-proliferation safeguards issue, a topic of intense international negotiations at the time. The design of RAPP-2 was basically a copy of RAPP-I but incorporated some lessons of experience and certain changes to permit an even greater participation by Indian manufacturers. RAPP-1 was completed in 1973; however, the detonation, in 1974, by India of a nuclear “device” overtook completion of RAPP-2. As a result of the detonation, Canada ceased to provide India with any support of its nuclear power program. The DAE eventually completed RAPP-2 in 1981 without further Canadian support.

A heavy-water design can sustain a chain reaction with a lower concentration of fissile atoms than light-water reactors, allowing it to use some alternative fuels; for example, “recovered uranium” (RU) from used LWR fuel. CANDU was designed for natural uranium with only 0.7% 235U, so RU with 0.9% 235U is a rich fuel. This extracts a further 30–40% energy from the uranium. The DUPIC (Direct Use of spent PWR fuel in CANDU) process under development can recycle it even without reprocessing. The fuel is sintered in air (oxidized), then in hydrogen (reduced) to break it into a powder, which is then formed into CANDU fuel pellets. CANDU can also breed fuel from the more abundant thorium. This is being investigated by India to take advantage of its natural thorium reserves.

Most of India’s nuclear reactors are of the pressurized heavy water reactor (PHWR) type with horizontal pressure tubes, just like the Canadian designed CANDU. In fact, the first PHWR (not the first nuclear reactor) in India was the Rajasthan Atomic Power Project (RAPP) unit and was a CANDU designed by Atomic Energy of Canada Limited (AECL) that used the Douglas Point unit in Ontario as reference design but modified to aid localization. RAPP-1 entered commercial operation 1973 December. While RAPP-1 was being constructed the design of RAPP-2 was started (Author’s note: I know because I was part of design team). However, the detonation of a nuclear device by India in 1974 curtailed completion of the design by AECL and India was on its own as far as nuclear technology was concerned. The design was completed by India and RAPP-2 eventually entered commercial operation in 1981 April. Since those early days India has developed its own indigenous designs of PHWRs with net electrical outputs of 202 MW, 490 MW, and 630 MW. All 17 PHWR units operating in 2015 (excludes RAPP-1 which has been shut down since 2004) were 202 MW (220 MW gross) except for two 490 MW (540 MW gross) units. There were four 630 MW (700 MW gross) units under construction with none in operation. All PHWR power units, except for RAPP-1, are designed, owned, and operated by Nuclear Power Corporation of India Ltd. Several of the country’s PHWRs have been refurbished for extended life operation.

Indo-Canada Nuclear Cooperation


Canada was among the first countries to participate in India’s nuclear power program. Not only was CIRUS the first research reactor to be built in India with outside help; it was also Canada’s first reactor export and marked a breakthrough for its nuclear industry.

The export of CANDU reactors commenced relatively early in the history of the CANDU program. Following the successful completion of the Canadian-supplied CIR research reactor at a site near Bombay in India, the Indian Department of Atomic Energy (DAE) was anxious to take the next step towards an indigenous Indian nuclear power program, based on the natural uranium, heavy water moderated type of reactor. India was attracted to this type of reactor because, like Canada, it did not possess its own uranium enrichment capability. Furthermore, India has very large reserves of thorium which could be utilized in this type of reactor to provide it with long-term fuel supply independence. In November of 1960, Homi Bhabha, Chairman of the Indian DAE, visited Canada to discuss possible arrangements for power reactor cooperation. At that time, he became interested in the Douglas Point reactor design, despite the fact that the detailed design program was still in its early stages. Following this visit, an extended series of negotiations commenced between AECL and the DAE with issues of financing and nonproliferation safeguards proving particularly difficult. Finally, with the approval of the Canadian and Indian governments, an agreement was signed between AECL and the DAE in December of 1963, permitting the Rajastan Atomic Power Plant (RAPP) project to proceed. The agreement called for the design to be closely patterned on that of Douglas Point but modified, as appropriate, to maximize possible participation by Indian manufacturers in the supply of equipment since India saw this first unit as the prototype of a series of indigenously supplied reactors.

The Prime Ministers of India and Canada signed a civil nuclear cooperation agreement in Toronto on 28 June 2010 which when all steps are taken, will provide access for Canada’s nuclear industry to India’s expanding nuclear market and also fuel for India’s reactors. Canada is one of the world’s largest exporters of uranium and Canada’s heavy water nuclear technology is marketed abroad with CANDU-type units operating in India, Pakistan, Argentina, South Korea, Romania and China. On 6 November 2012, India and Canada finalised their 2010 nuclear export agreement, opening the way for Canada to begin uranium exports to India.

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Author: Vincent Xu (APAC Account Manager), Nuclear Business Platform. 

By |2019-10-04T14:50:48+08:00October 2nd, 2019|industry-insights, nuclear-industry|0 Comments