TheIPHWR (Indian Pressurized Heavy Water Reactor) is a class of Indianpressurized heavy-water reactors designed by theBhabha Atomic Research Centre.^[1] The baseline220 MWe design was developed from theCANDU basedRAPS-1 andRAPS-2 reactors built atRawatbhata, Rajasthan. Later the design was indigenised based onVVER technology which was scaled to 540 MWe and700 MWe designs. Currently there are 18 units of various types operational at various locations in India (14 IPHWR-220, 2 IPHWR - 540 and 3 IPHWR-700) and 13 more IPHWR-700 reactors under construction/planned.

The first PHWR units built in India(RAPS-1 and RAPS-2) are of CanadianCANDU design similar to the first full-scale Canadian reactor built atDouglas point, Ontario. The reactors were set up in collaboration with Government of Canada. Starting in 1963, 100 MWe RAPS-1 was mostly built with equipment and technology supplied byAECL, Canada. RAPS-1 was commissioned in 1973 but the cessation of Canadian cooperation in light of successful development of nuclear weapons by India as part ofOperation Smiling Buddha the RAPS-2 commissioning could only be completed by 1981. India took help ofSoviet Union whoseVVER (Pressurised Water Reactor type) technology was used as a design for indigenization byBhabha Atomic Research Centre in partnership with Indian manufacturersLarsen & Toubro andBharat Heavy Electricals Limited. Successively, a totally Indian design of 220 MWe power capacity was designed and two units were built atKalpakkam inTamil Nadu state christened MAPS-1 and MAPS-2. MAPS-1&2 design was evolved from RAPS-1&2, with modifications carried out to suit the coastal location and also introduction of suppression pool to limit containment peak pressure underloss of coolant accident (LOCA) in lieu of dousing tanks in RAPS-1&2. In addition, MAPS-1&2 have partial double containment. This design was further improved and all subsequent PHWR units in India have double containment.^[2]

With experience of design and operation of earlier units and indigenous R&D efforts, major modifications were introduced inNAPS-1&2. These units are the basis of standardized Indian PHWR units later designated as IPHWR-220.

The design of subsequent units i.e. KGS-1, KGS-2, RAPS-3, RAPS-4, RAPS-5, RAPS-6, KGS-3 and KGS-4 is of standard Indian PHWR design. The major improvements in these designs include valve-less primary heat transport system and a unitized control room concept. In addition, the design of these units included improvements in Control and Instrumentation system and incorporation of computer based systems to match with the advancement in technology.

Upon completion of the design of IPHWR-220, a larger 540 MWe design was startedc. 1984 under the aegis ofBARC in partnership with NPCIL.^[3] Two reactors of this design were built inTarapur, Maharashtra starting in the year 2000 and the first was commissioned on 12 September 2005. Only two such reactors i.e. Tarapur-3 & Tarapur-4 were built. The design was later upgraded to a 700 MWe design

The IPHWR-540 design was later upgraded to 700 MWe with the main objective to improve fuel efficiency and develop a standardized design to be installed at many locations across India as a fleet-mode effort. The design was also upgraded to incorporateGeneration III+ features.

The 700 MWe PHWR design includes some features, which are introduced for the first time in Indian PHWRs which include partial boiling at the coolant channel outlet, interleaving of primary heat transport system feeders, passive decay heat removal system, regional over power protection, containment spray system, mobile fuel transfer machine, and a steel liner on the inner containment wall.^[4]

By 2031–2032, NPCIL plans to construct 18 more nuclear power reactors, which together have the potential to produce 13,800 MWe of electricity. This will bring the total amount of atomic power in the energy mix to 22,480 MWe.^[5]

IPHWR-220

2 atNarora Atomic Power Station

2 atKakrapar Atomic Power Station

4 atKaiga Atomic Power Station

2 atMadras Atomic Power Station

4 atRajastan Atomic Power Project

IPHWR-540

2 atTarapur Atomic Power Station

IPHWR-700

2 at Kakrapar Atomic Power Station

2 at Kaiga Atomic Power Station

2 atGorakhpur Nuclear Power Plant

2 at Rajastan Atomic Power Project

The IPHWR reactor is a horizontal pressure tube type. It is derived from theCANDU reactor. These tubes are housed in a horizontal vessel called Calandria. It is filled with heavy water moderator. The each independent tubes are in tubes with circulating CO2 gas. The tubes contain 12 fuel assemblies each and circulating pressurized heavy water coolant. This coolant collects heat from the fuel (natural uranium dioxide) and transfers it to the secondary coolant water to generate steam in the steam generators. This steam turns the turbine. This steam is condensed, reheated, deaerated and pumped back to the reactor. The moderator heavy water is kept circulating and is maintained at around 70 degrees Celsius. The fission chain reaction is controlled using control rods of cadmium or boron. There is a scram system to inject a poison called gadolinium nitrate in the moderator. The reactors can be refuelled while on full power giving additional advantages. The reactor has a efficiency of around 29 to 30 % gross. These reactors are highly safe. They have many innovative safety systems. They form the first stage of India's three stage nuclear power program.^{[citation needed]}

• IPHWR-220, first version of the IPHWR class of recators
• IPHWR-700, Generation III+ successor to the IPHWR-220 design
• CANDU, predecessor to Indian PHWR designs
• AHWR-300, thorium fuelled PHWR design for the Indian Three stage nuclear power programme
• India's three-stage nuclear power programme
• Nuclear power in India

• Nuclear power reactor types
• Indian inventions
• Nuclear power in India
• Pressurized water reactors

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