NPCIL Begins Fuel Loading at RAPP-8 as India’s Fourth Indigenous 700 MWe PHWR Moves Towards Commissioning

Nuclear Power Corporation of India Limited has begun initial fuel loading at Unit 8 of the Rajasthan Atomic Power Project at Rawatbhata, bringing India’s fourth indigenous 700 MWe Pressurised Heavy Water Reactor into one of the final major stages before criticality and power generation.

Initial Fuel Loading began at 15:18 hrs on 19 September 2026 after NPCIL received permission from the Atomic Energy Regulatory Board and completed the prescribed commissioning prerequisites. The regulator granted clearance following safety evaluations, major system-integrity audits and site-readiness reviews carried out as part of the regulatory process.

RAPP-8 forms part of the RAPP-7&8 project, comprising two indigenous 700 MWe PHWRs at Rawatbhata in Rajasthan. The start of fuel loading means Unit 8 has now moved from construction and system commissioning into the stage that precedes the reactor’s first controlled nuclear chain reaction.

First Approach to Criticality Comes Next

The next major milestone for RAPP-8 will be the First Approach to Criticality, when a controlled and self-sustaining nuclear fission chain reaction is established in the reactor core for the first time.

This will be followed by progressive commissioning tests and the commencement of power generation. NPCIL has stated that the unit is expected to enter commercial operation during the current financial year.

The progression from initial fuel loading to criticality is closely regulated. Each stage requires the completion of prescribed testing and safety procedures before permission is granted to proceed further.

Fourth Reactor in India’s 700 MWe PHWR Series

RAPP-8 is the fourth reactor in a planned series of 16 indigenous 700 MWe PHWRs being developed across India.

The first two reactors in this series, Kakrapar Atomic Power Station Units 3 and 4 in Gujarat, entered commercial operation during 2023–24. They were followed by RAPP-7 at Rawatbhata, which began commercial operation in April 2025.

The fourth unit brings India further into the standardised deployment phase of the 700 MWe PHWR programme. Rather than building each reactor around a substantially different design, NPCIL is progressively deploying a common indigenous reactor design across multiple sites.

This fleet approach allows engineering experience, manufacturing processes, procurement arrangements and construction practices to be carried forward from one project to the next.

Indigenous 700 MWe PHWR Becomes India’s Standard Large Reactor

India’s 700 MWe PHWR is the largest domestically developed pressurised heavy-water reactor design currently being deployed in the country.

The reactor represents an evolution of India’s earlier 220 MWe and 540 MWe PHWR designs and incorporates advanced safety systems while retaining the heavy-water reactor technology that has formed the backbone of India’s indigenous nuclear programme.

The PHWR design uses heavy water as moderator and coolant and is capable of operating with natural uranium fuel. The larger 700 MWe configuration provides greater electricity output while retaining the technological foundation developed through several decades of Indian reactor design and operation.

NPCIL says RAPP-8 incorporates advanced safety features and has reached the fuel-loading stage in accordance with all applicable AERB requirements.

Rawatbhata Nuclear Complex Continues to Expand

Rawatbhata has become one of the country’s largest nuclear-power centres, hosting multiple generations of Indian PHWRs.

The commissioning of RAPP-7 and the movement of RAPP-8 towards criticality are being followed by preparations for another pair of reactors at the site. NPCIL has confirmed that geotechnical investigations for RAPP-9 and RAPP-10 began on 19 September 2026.

Those investigations include borehole drilling, geophysical surveys and laboratory testing of the site’s soil and rock strata. The results will provide the engineering baseline for civil structures and foundations associated with the future reactors.

The parallel progress of RAPP-8 and preparatory work for Units 9 and 10 underlines the growing importance of Rawatbhata within India’s long-term nuclear expansion programme.

NPCIL Operates 24 Nuclear Reactors

NPCIL currently operates 24 nuclear power reactors with a combined capacity of 8.78 GWe. Another 17 reactors, representing around 13 GWe, are at different stages of implementation.

The corporation is also preparing for a much larger expansion as India works towards the government’s goal of 100 GWe of nuclear power capacity by 2047.

NPCIL has stated that it aims to contribute more than half of that target through its own projects. Standardised deployment of the indigenous 700 MWe PHWR will form a major part of that expansion.

RAPP-8 Moves From Construction Towards Operation

The start of initial fuel loading does not mean RAPP-8 has begun generating electricity. It marks the transition into the final commissioning sequence leading towards reactor criticality and power production.

The unit must still complete First Approach to Criticality, progressive power-raising tests, grid synchronisation and other commissioning requirements before entering commercial operation.

With fuel now entering the core, however, RAPP-8 has crossed one of the most important milestones in that process. Its progress also gives India four successive reactors built around the same indigenous 700 MWe PHWR platform, strengthening the technological and industrial base required for the much larger fleet that follows.

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References

Nuclear Power Corporation of India Limited — 19 September 2026: Official statement announcing commencement of Initial Fuel Loading at RAPP-8 at 15:18 hrs following AERB permission.

Nuclear Power Corporation of India Limited — RAPP-9&10 Update: Official announcement confirming commencement of geotechnical investigations for the next pair of reactors at Rawatbhata on 19 September 2026.

Atomic Energy Regulatory Board: Regulatory authority responsible for safety review and permission for commissioning stages of nuclear power reactors in India.

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