Site selection for a nuclear power plant is governed first by safety: the site must allow an exclusion zone of at least 1 km around each reactor, a 5 km natural growth zone and a 16 km emergency planning zone, with no active geological fault within 5 km and protection against floods and tsunamis. Only after a site passes these tests do the usual engineering questions of cooling water and grid connection come in. In India the rules are set by the Atomic Energy Regulatory Board (AERB) in its safety code AERB/NF/SC/S (Rev.1), “Site Evaluation of Nuclear Facilities”, approved in July 2014.
How nuclear site suitability is judged
A coal plant is sited to minimise the cost of moving coal, water and ash. A nuclear plant is sited so that, even in a serious accident, radiation doses to the public stay within limits. The AERB code turns that aim into three tests:
- Can the site affect the plant? Earthquakes, surface faulting, floods, cyclones, tsunamis, nearby industries, airports.
- Can the plant affect the people? How radioactivity would spread through air, river, sea and groundwater, and how many people live along those paths.
- Can an emergency plan work? Roads, communication and population numbers that allow sheltering or evacuation if needed.
If a weakness cannot be fixed by design features, site protection works or administrative controls, the code says the site is unsuitable for that type and size of plant.
Exclusion zone, natural growth zone and emergency planning zone
The zones are the part of nuclear siting that has no equivalent in any other power plant. Under the 2014 AERB code they are measured from the centre of each reactor:
| Zone | Radius | What it means |
|---|---|---|
| Exclusion zone (EZ) | Not less than 1.0 km | Controlled by the operator; no public residence. Its size must keep doses at the boundary within limits during normal operation and the design basis accident |
| Natural growth zone | Up to 5 km | Only natural growth of existing population is allowed, controlled administratively; no new large settlements or industries. Also called the sterilised zone in older texts |
| Emergency planning zone (EPZ) | 16 km | Roads, transport and communication must be kept ready so that protective actions can be carried out |
| Radiological surveillance zone | 30 km | Baseline and continuous environmental monitoring; population data collected up to this radius |
The dose targets behind the zones are specific. In normal operation, all facilities on a site together must keep the dose to any member of the public below 1 mSv per year. For a design basis accident, the design target is below 20 mSv, with no need for sheltering, evacuation, food control or iodine tablets for anyone beyond the exclusion zone.
Zone sizes are not frozen. In 2026 there were public reports of proposals to allow smaller exclusion zones for new designs such as small modular reactors, which critics opposed. Always quote the zone sizes from the code in force.
Seismic hazard and geology
An earthquake is the external event most likely to damage every safety system at once, so geology is studied in more detail than for any other plant type.
- Active faults: an active (capable) fault within 5 km makes the site unacceptable for a nuclear power plant. A fault that cannot be shown to be inactive is treated as active.
- Design ground motion: site-specific earthquake levels are derived from the seismotectonics of the region, including earthquakes that could be triggered by nearby dams and reservoirs.
- Foundations: the ground is checked for liquefaction, subsidence, slope failure and cavities, because the reactor building must sit on competent rock or treated soil.
A site in a higher seismic zone is not automatically rejected; the plant is designed for the higher shaking. What cannot be engineered away is a fault that could shear the ground under the plant.
Flooding and tsunami: lessons from Kalpakkam and Fukushima
Because nuclear plants need so much cooling water, most sit beside a sea, river or reservoir, which puts them next to their biggest flood risk. The AERB code requires a design basis flood level for every site, considering river floods, dam breaks, extreme rainfall, storm surge, wind waves and tsunamis. When the flood level is worked out by probability, it must correspond to an annual exceedance frequency of 10-4, that is, a flood expected about once in 10,000 years.
Two events shaped Indian practice:
- Kalpakkam, 26 December 2004: the Indian Ocean tsunami sent sea water into the pump house of Unit 2 of the Madras Atomic Power Station. The reactor was tripped and brought to safe shutdown, cooling was maintained, no radioactivity was released, and the unit restarted on 1 January 2005. The event was rated 0 on the International Nuclear Event Scale, but it showed that a coastal site’s tsunami height must be designed for, not assumed away.
- Fukushima, March 2011: a tsunami beyond the design basis knocked out power and cooling at a Japanese coastal plant. After it, Indian plants were reviewed against extreme floods and prolonged loss of power, and siting now looks harder at events beyond the historical record.
Cooling water: why a nuclear plant needs more than a coal plant
Water-cooled reactors produce steam at below about 300 °C, while a supercritical coal boiler delivers steam at well over 500 °C. Lower steam temperature means lower cycle efficiency, roughly 33% for a nuclear plant against about 40% for a modern coal plant (see the Carnot cycle for why temperature limits efficiency).
Worked example: 1000 MWe from each plant
| Quantity | Nuclear, 33% | Coal, 40% |
|---|---|---|
| Heat input = 1,000 / efficiency | 1,000 / 0.33 = 3,030 MW | 1,000 / 0.40 = 2,500 MW |
| Waste heat = input – 1,000 | 2,030 MW | 1,500 MW |
| Heat lost up the chimney (about 10% of input for coal) | None, no combustion | About 250 MW |
| Heat to the condenser cooling water | About 2,030 MW | About 1,250 MW |
| Once-through flow for a 10 °C rise (Q / 4.18 x 10) | About 48.6 m3/s | About 29.9 m3/s |
| Cooling-tower evaporation (Q / 2,400 kJ/kg) | About 3,050 m3/h | About 1,880 m3/h |
On waste heat alone the nuclear plant rejects 2,030 / 1,500 = 1.35 times as much. Because a coal plant sends part of its waste heat up the chimney and a reactor sends almost all of it to the condenser, the cooling-water load is about 2,030 / 1,250 = 1.6 times that of the coal plant. This is why most nuclear sites are on the coast or beside a large reservoir, and why inland sites need very large, assured supplies. The AERB code also asks for an assured supply of cooling water, a study of whether warm discharge could recirculate into the intake, and outfall temperatures that meet pollution-control-board limits.
Population density and emergency planning
India is densely populated, so finding land with a thinly populated 5 km ring is often the hardest part of nuclear siting. The code requires existing and projected population, including seasonal and floating population, to be mapped up to 30 km, together with schools, hospitals, prisons and population centres. The site must allow a workable emergency plan across the 16 km zone.
AERB also gives screening distances. A candidate site is readily acceptable if it is at least 16 km from airports (including military airfields), military installations storing ammunition, and industries handling explosives or hazardous chemicals, and at least 5 km from monuments, pilgrimage and tourist spots that draw large crowds. A site that falls short can still be accepted if engineering measures cover the hazard.
Fuel transport, waste and grid
Fuel transport is a minor siting factor. A 1000 MW coal plant on Indian coal needs about 15,000 tonnes of coal a day. A 1000 MWe light-water reactor needs of the order of 25 tonnes of fresh fuel a year, delivered in a few shipments. Spent fuel is stored on site, in pools and later in dry storage, so the site needs space and a safe route for fuel casks, but not a railway siding running trains every few hours.
Grid connection matters for two reasons: to evacuate the power, and because off-site power supply is itself a safety feature for cooling the reactor after shutdown. A site on a weak grid, prone to frequent disturbances, is a poorer choice even if everything else is right.
How this differs from a thermal plant
For a coal station, the order of factors is coal, water, ash and land, and a pithead location is often best (see site selection for a thermal power plant). For a nuclear station, fuel logistics hardly matter and there is no ash, but the site must satisfy exclusion and planning zones, fault and flood criteria, and dose limits before cost is even discussed. A nuclear plant can be far from any mine; it cannot be close to a city or an active fault.
Indian nuclear sites as examples
| Site | State | Reactors | Cooling water source and siting point |
|---|---|---|---|
| Tarapur | Maharashtra | India’s first plant (1969), BWRs and PHWRs | Arabian Sea; coastal site |
| Kalpakkam (Madras) | Tamil Nadu | PHWRs | Bay of Bengal; tsunami of 2004 tested the flood design |
| Kudankulam | Tamil Nadu | VVER-1000 pressurised water reactors built with Russia | Sea water; coastal site on the southern tip |
| Kaiga | Karnataka | PHWRs | Kadra reservoir on the Kali river; inland, forested site |
| Kakrapar | Gujarat | PHWRs, including India’s first 700 MWe units | Moticher lake fed from the Kakrapar weir on the Tapi; inland site with cooling towers |
| Gorakhpur (GHAVP) | Haryana | Four 700 MWe PHWRs under construction | Bhakra canal water; an inland site in the plains of north India, first units expected around 2031 |
FAQs
What is the exclusion zone of a nuclear power plant in India?
Under AERB code AERB/NF/SC/S (Rev.1), the exclusion zone must be at least 1.0 km from the centre of each reactor. No public residence is allowed inside it, and its size must keep radiation doses at the boundary within the limits for normal operation and design basis accidents.
What is the emergency planning zone around an Indian nuclear plant?
16 km from the reactor. Within it, roads, transport and communication must be maintained so that sheltering or evacuation can be carried out if an accident required it.
Why do nuclear power plants need more cooling water than coal plants?
They run at lower steam temperatures, so efficiency is about 33% against about 40% for a modern coal plant, and almost all their waste heat goes to the condenser. For 1000 MWe, a reactor rejects about 2,030 MW to cooling water against about 1,250 MW for a coal plant.
Can a nuclear plant be built in an earthquake zone?
Yes, if the plant is designed for the site-specific earthquake. What AERB does not allow is an active fault within 5 km of the site, because ground rupture cannot be designed against.
Which organisation approves nuclear power plant sites in India?
The Atomic Energy Regulatory Board (AERB) reviews and approves sites against its siting code; the plants are built and run by NPCIL and other operators under the Department of Atomic Energy.