🗞️ Why in News The Nuclear Power Corporation of India Limited (NPCIL) began Initial Fuel Loading (IFL) at Unit 8 of the Rajasthan Atomic Power Project (RAPP-8) at Rawatbhata at 15:18 hours on 19 September 2026, after permission from the Atomic Energy Regulatory Board (AERB). RAPP-8 is the fourth of 16 indigenous 700 MWe Pressurised Heavy Water Reactors (PHWRs) being built in India. The same day, geotechnical investigations began for Units 9 and 10 at the site.
Where RAPP-8 Stands
| Stage | Status |
|---|---|
| AERB permission for fuel loading | Granted after safety evaluations, system integrity audits and site readiness reviews |
| Initial Fuel Loading | Began 19 September 2026 |
| First Approach to Criticality (FAC) | Next major step: the start of a controlled fission chain reaction |
| Grid synchronisation and power generation | After criticality |
| Commercial operation | NPCIL expects it during the current financial year (2026-27) |
The 700 MWe PHWR Fleet
The 700 MWe PHWR is the largest indigenously designed reactor in India. In 2017 the Union Cabinet approved ten such reactors to be built in fleet mode, a standardised design built in series to cut cost and construction time.
| Unit | Location | Status |
|---|---|---|
| KAPP-3 | Kakrapar, Gujarat | Commercial operation in 2023-24 |
| KAPP-4 | Kakrapar, Gujarat | Commercial operation in 2023-24 |
| RAPP-7 | Rawatbhata, Rajasthan | Commercial operation in April 2025 |
| RAPP-8 | Rawatbhata, Rajasthan | Fuel loading began 19 September 2026 |
| GHAVP 1 and 2 | Gorakhpur, Haryana | Under construction |
| Kaiga 5 and 6 | Kaiga, Karnataka | Under construction |
| RAPP-9 and 10 | Rawatbhata, Rajasthan | Geotechnical investigations began 19 September 2026 |
Besides RAPP-8, NPCIL has eight other reactors under construction: two at Gorakhpur (Haryana), two at Kaiga (Karnataka) and four at Kudankulam (Tamil Nadu), the last being Russian-designed VVER units.
How a PHWR Works, and Where It Fits
A Pressurised Heavy Water Reactor uses natural uranium as fuel and heavy water (deuterium oxide) as both moderator and coolant. Because heavy water absorbs very few neutrons, the reactor can sustain a chain reaction without enriched uranium, which is why India, with limited access to enrichment for most of its history, built its programme on PHWRs.
India’s three-stage nuclear programme, conceived by Homi J. Bhabha:
| Stage | Reactor | Fuel | Purpose |
|---|---|---|---|
| Stage 1 | PHWR | Natural uranium | Power, and plutonium in spent fuel |
| Stage 2 | Fast Breeder Reactor | Plutonium-based fuel | Breeds more fissile material; can convert thorium to uranium-233 |
| Stage 3 | Thorium-based reactors | Thorium and uranium-233 | Uses India’s large thorium reserves |
Rawatbhata is in Chittorgarh district, Rajasthan, on the Chambal river. The first unit at the site, RAPP-1, was built with Canadian collaboration and began operating in 1973.
Why It Matters
Energy transition. Nuclear power is firm, low-carbon electricity that can run round the clock, complementing variable solar and wind. The government’s Nuclear Energy Mission targets 100 GW of nuclear capacity by 2047, against installed capacity of under 9 GW today, and the SHANTI Act, 2025 opened the sector to wider participation.
Indigenisation. Every 700 MWe unit that reaches operation validates a design, supply chain and construction capability built in India. Fleet mode is meant to turn one-off projects into a standard product.
The constraints. Long construction periods, cost overruns, dependence on imported uranium for a larger fleet, heavy water supply, and land and public-acceptance questions remain the main limits on how fast the fleet can grow.
UPSC Relevance
GS Paper 3. Infrastructure: energy; science and technology: indigenisation of technology; nuclear energy.
A question worth preparing. Assess the role of the indigenous 700 MWe PHWR fleet in India’s energy transition, and the constraints on scaling it towards the 2047 nuclear target. (250 words)
The Mains framing. Begin with the three-stage programme and the logic of PHWRs (natural uranium, heavy water). Show the fleet’s progress (KAPP-3 and 4, RAPP-7, RAPP-8) and the fleet-mode approach. Weigh strengths (firm low-carbon power, indigenous design) against constraints (time, cost, fuel, acceptance). Conclude with enablers: standardisation, private participation under the 2025 law, and fuel security.
📌 Facts Corner, Knowledgepedia
Prelims, statement-ready facts:
- NPCIL began Initial Fuel Loading at RAPP-8, Rawatbhata, on 19 September 2026, after AERB permission.
- RAPP-8 is the fourth of 16 indigenous 700 MWe PHWRs.
- The first two, KAPP-3 and KAPP-4 (Kakrapar, Gujarat), began commercial operation in 2023-24.
- RAPP-7 began commercial operation in April 2025.
- Next step for RAPP-8: First Approach to Criticality; commercial operation is expected in 2026-27.
- A PHWR uses natural uranium fuel with heavy water as moderator and coolant.
- Rawatbhata is in Chittorgarh district, Rajasthan, on the Chambal.
- In 2017 the Cabinet approved 10 PHWRs of 700 MWe in fleet mode.
- NPCIL has eight other reactors under construction: 2 Gorakhpur (Haryana), 2 Kaiga, 4 Kudankulam.
Prelims, the traps:
- Gorakhpur nuclear project is in Haryana, not Uttar Pradesh.
- PHWRs use natural, not enriched, uranium; Kudankulam VVERs use enriched uranium.
- Fuel loading is not criticality; the First Approach to Criticality comes after it.
- PHWRs belong to Stage 1 of the three-stage programme; fast breeders are Stage 2.
Mains, arguments and keywords:
- Fleet mode turns one-off projects into a standard, repeatable design.
- Nuclear power offers firm low-carbon supply alongside variable renewables.
- Constraints: construction time, cost, fuel supply, heavy water, public acceptance.
- Keywords: PHWR, 700 MWe, fleet mode, AERB, three-stage programme, Nuclear Energy Mission, SHANTI Act.
Interview, be ready for:
- “Why did India choose PHWRs?” Natural uranium fuel avoided the need for enrichment and fitted the three-stage plan to use thorium.
- “Can India reach 100 GW of nuclear by 2047?” Only with much faster construction, private and foreign participation, and assured fuel; the 700 MWe fleet is the base, not the whole answer.
Source: RAPP-8: Fuel Loading Begins at India's Fourth Indigenous 700 MWe Reactor — Ujiyari.com | Free UPSC & State PCS Current Affairs
