PriscillaNair10 at 00:00, 12 April 2026

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{{short description|Indian nuclear reactor design}}
[[File:PHWR under Construction at Kakrapar Gujarat India.jpg|thumb|[[Kakrapar Atomic Power Station]] with two [[IPHWR-700]] units under construction in the Indian state of [[Gujarat]]]]
The '''IPHWR''' ('''Indian Pressurized Heavy Water Reactor''') is a class of Indian [[pressurized heavy-water reactor]]s designed by the [[Bhabha Atomic Research Centre]].<ref>{{cite web |title=ANU SHAKTI: Atomic Energy In India |url=http://www.barc.gov.in/about/anushakti_phwr.html |publisher=BARC |access-date=2021-03-21 |archive-date=2020-06-26 |archive-url=https://web.archive.org/web/20200626114224/http://www.barc.gov.in/about/anushakti_phwr.html |url-status=dead }}</ref> The baseline [[IPHWR-220|220 MWe]] design was developed from the [[CANDU reactor|CANDU]] based [[Rajastan Atomic Power Project|RAPS-1]] and [[Rajastan Atomic Power Project|RAPS-2]] reactors built at [[Rawatbhata]], Rajasthan. Later the design was indigenised and scaled to 540 MWe and [[IPHWR-700|700 MWe]]. Currently there are 19 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.

== IPHWR-220 ==
{{Main|IPHWR-220}}

The first PHWR units built in India [[Rajasthan Atomic Power Station|(RAPS-1 and RAPS-2)]] are of Canadian [[CANDU]] design similar to the first full-scale Canadian reactor built at [[Douglas Point Nuclear Generating Station|Douglas 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 by [[Atomic Energy of Canada Limited|AECL]], 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 of [[Operation Smiling Buddha]] the RAPS-2 commissioning could only be completed by 1981. Later on higher capacity derivatives were developed by [[Bhabha Atomic Research Centre]] in partnership with Indian manufacturers [[Larsen & Toubro]] and [[Bharat Heavy Electricals Limited]]. Successively, a totally Indian design of 220 MWe power capacity was designed and two units were built at [[Kalpakkam]] in [[Tamil 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 under [[loss 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.<ref name=aris_220/>

With experience of design and operation of earlier units and indigenous R&D efforts, major modifications were introduced in [[Narora Atomic Power Station|NAPS-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.

== IPHWR-540 ==

Upon completion of the design of IPHWR-220, a larger 540 MWe design was started {{circa|1984}} under the aegis of the [[Bhabha Atomic Research Centre]] (BARC) in partnership with the [[Nuclear Power Corporation of India Limited]] (NPCIL).<ref name=baitej/> Two reactors of this design were built in [[Tarapur Atomic Power Station|Tarapur, 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.

== IPHWR-700 ==
{{Main|IPHWR-700}}

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 incorporate [[Generation III reactor#First reactors|Generation 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.<ref name=aris_700/>

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.<ref>{{Cite web |date=2024-02-25 |title=India to add 18 more nuclear power reactors with total capacity of 13,800 MWe by 2032: NPCIL |url=https://indianexpress.com/article/india/nuclear-power-reactors-total-capacity-npcil-9180403/ |access-date=2024-03-04 |website=The Indian Express |language=en}}</ref>

==Reactor fleet ==

'''IPHWR-220 '''

2 at [[Narora Atomic Power Station]]

2 at [[Kakrapar Atomic Power Station]]

4 at [[Kaiga Atomic Power Station]]

2 at [[Madras Atomic Power Station]]

4 at [[Rajastan Atomic Power Project]]

'''IPHWR-540 '''

2 at [[Tarapur Atomic Power Station]]

'''IPHWR-700 '''

2 at Kakrapar Atomic Power Station

2 at Kaiga Atomic Power Station

2 at [[Gorakhpur Nuclear Power Plant]]

2 at Rajastan Atomic Power Project

4 planned at [[Mahi Banswara Atomic Power Plant]]

==Design ==

[[File:Pressurized heavy water reactor.png|thumb|PRESSURIZED HEAVY WATER REACTOR DIAGRAM]]
The IPHWR reactor is a horizontal pressure tube type. It is derived from the [[CANDU]] 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 [[carbon dioxide]] 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 coupled to a AC synchronous generator producing 11kV or 20kV 50 Hz AC current. This steam is then 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.{{cn|date=March 2025}}

== Technical specifications ==
{| class="wikitable"
|+
!Specifications
!IPHWR-220<ref name=aris_220>{{Cite news|date=2011-04-04|title=Status report 74 - Indian 220 MWe PHWR (IPHWR-220)|work=International Automic Energy Agency|url=https://aris.iaea.org/PDF/IPHWR-220.pdf|access-date=2021-03-21|archive-date=2022-05-17|archive-url=https://web.archive.org/web/20220517195913/https://aris.iaea.org/PDF/IPHWR-220.pdf|url-status=dead}}</ref>
!IPHWR-540<ref>{{Cite news|last1=Soni|first1=Rakesh|last2=Prasad|first2=PN|others=S. Vijayakumar, A.G. Chhatre, K.P.Dwivedi|title=Fuel technology evolution for Indian PHWRs|work=International Atomic Energy Agency|url=https://inis.iaea.org/collection/NCLCollectionStore/_Public/37/098/37098316.pdf}}</ref><ref>{{Cite journal|last=Muktibodh|first=U.C|date=2011|title=Design, Safety and Operability performances of 220 MWe, 540 MWe and 700 MWe PHWRs in India|journal=Inter-Regional Workshop on Advanced Nuclear Reactor Technology for Near-term Deployment}}</ref><ref>{{Cite journal|last1=Bajaj|first1=S.S|last2=Gore|first2=A.R|date=2006|title=The Indian PHWR|journal=Nuclear Engineering and Design|volume=236|issue=7–8|pages=701–722|doi=10.1016/j.nucengdes.2005.09.028}}</ref><ref name=baitej>{{Cite journal|last=Singh|first=Baitej|date=July 2006|title=Physics design and Safety assessment of 540 MWe PHWR|url=http://barc.gov.in/publications/nl/2006/200607-2.pdf|journal=BARC Newsletter|volume=270|access-date=2021-03-21|archive-date=2013-05-22|archive-url=https://web.archive.org/web/20130522215947/http://barc.gov.in/publications/nl/2006/200607-2.pdf|url-status=dead}}</ref>
!IPHWR-700<ref name=aris_700>{{Cite news|date=2011-08-01|title=Status report 105 - Indian 700 MWe PHWR (IPHWR-700)|work=International Atomic Energy Agency|url=https://aris.iaea.org/PDF/IPHWR-700.pdf|access-date=2021-03-20|archive-date=2023-04-17|archive-url=https://web.archive.org/web/20230417041219/https://aris.iaea.org/PDF/IPHWR-700.pdf|url-status=dead}}</ref>
|-
|Thermal output, MWth
|754.5
|1730
|2166/2177
|-
|Active power, MWe
|220
|540
|700
|-
|[[Electrical efficiency|Efficiency]], net %
|27.8
|28.08
|29.08
|-
|Coolant temperature, °C:
|
|
|
|-
| core coolant inlet
|249
|266
|266
|-
| core coolant outlet
|293.4
|310
|310
|-
|Primary coolant material
| colspan="3" |Heavy Water
|-
|Secondary coolant material
| colspan="3" |Light Water
|-
|Moderator material
| colspan="3" |Heavy Water
|-
|Reactor operating pressure, kg/cm2 (g)
|87
|100
|100
|-
|Active core height, cm
|508.5
|594
|594
|-
|Equivalent core diameter, cm
|451
| -
|638.4
|-
|Average fuel power density
|9.24 KW/KgU
| -
|235 MW/m3
|-
|Average core power density, MW/m3
|10.13
| -
|12.1
|-
|Fuel
| colspan="3" |Sintered Natural UO2 pellets
|-
|Cladding tube material
|Zircaloy-2
| colspan="2" |Zircaloy-4
|-
|Fuel assemblies
|3672
|5096
|4704 fuel bundles in 392 channels
|-
|Number of fuel rods in assembly
|19 elements in 3 rings
|37
|37 elements in 4 rings
|-
|Enrichment of reload fuel
| colspan="3" |0.7% U-235
|-
|Fuel cycle length, Months
|24
|12
|12
|-
|Average fuel [[burnup]], MW · day / ton
|6700
|7500
|7050
|-
|Control rods
|SS/Co
| colspan="2" |Cadmium/SS
|-
|Neutron absorber
|Boric Anhydride
| colspan="2" |Boron
|-
|[[Residual heat removal system]]
|Active: Shutdown cooling system
Passive: Natural circulation through steam generators
| colspan="2" |Active: Shutdown cooling system
Passive: Natural circulation through steam generators

and Passive Decay heat removal system
|-
|Safety injection system
| colspan="3" |Emergency core cooling system
|}

==Further development==
NPCIL is developing the Bharat small modular reactor (BSMR) and has asked for orders from private companies for construction of BSR at their manufacturing sites to which till now six companies have responded. It is a 220MWe compact PHWR [[Small modular reactor]] derived from the larger IPHWR-220.<ref>[https://www.world-nuclear-news.org/articles/deadline-extended-to-allow-wider-participation-in-indian-small-reactor-rfp Deadline extended to allow wider participation in Indian small reactor RFP], World Nuclear News, 8 October 2025.</ref>

==See also==
* [[IPHWR-220]], first version of the IPHWR class of reactors
* [[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]]

== References ==
{{reflist}}
{{Nuclear power in India}}
{{Nuclear fission reactors}}

[[Category:Nuclear power reactor types]]
[[Category:Nuclear power in India]]
[[Category:Pressurized water reactors]]

IPHWR - Revision history

PriscillaNair10 at 00:00, 12 April 2026