AERB Licenses India’s First Indigenously Developed 700 MWe PHWRs at Kakrapar

India’s nuclear regulator, the Atomic Energy Regulatory Board (AERB), has granted an operation license for two indigenously developed 700 MWe Pressurised Heavy Water Reactors (PHWRs) at the Kakrapar Atomic Power Station (KAPS) in Gujarat. The KAPS-3 reactor was commissioned at full power in August 2023, with the KAPS-4 unit following suit in August of the subsequent year.

Rigorous Licensing Process for New PHWR Design

The 700 MWe reactor represents a new scale for India’s PHWR technology, making its licensing process particularly stringent. It involved rigorous multi-tiered safety reviews and assessment of the reactor design, covering its entire life cycle across multiple stages, from siting and construction to commissioning at full power. The Nuclear Power Corporation of India Limited (NPCIL) received the License for Operation for KAPS 3&4 from the AERB for a period of five years on July 3.

India’s PHWR Fleet and Technological Advancement

India has a significant operational fleet of PHWRs:

• 15 PHWRs of 220 MWe capacity.
• Two PHWRs of 540 MWe capacity.

The 540 MWe PHWR design was successfully upgraded to 700 MWe, and the first pair of these advanced reactors are now operational at Kakrapar. Furthermore, a similar 700 MWe reactor at Rawatbhata in Rajasthan began commercial operations in March of this year.

Understanding Pressurised Heavy Water Reactors (PHWRs)

A PHWR is a nuclear power reactor that:

• Commonly uses unenriched natural uranium as its fuel.
• Employs heavy water (deuterium oxide, D2​O) as both its coolant and moderator.
• Keeps the heavy water coolant under pressure, allowing it to be heated to higher temperatures without boiling, similar to a typical pressurized water reactor (PWR).

The primary advantage of using heavy water, despite its higher cost, is its enhanced neutron economy. This allows the reactor to operate without the need for expensive fuel enrichment facilities, thereby mitigating the additional capital cost of the heavy water and generally enhancing the reactor’s ability to efficiently utilize alternate fuel cycles.

History of PHWR Development in India

India’s PHWR technology program began in the late 1960s with the construction of the first 220 MWe reactor, Rajasthan Atomic Power Station (RAPS-1). This initial project was based on a design similar to Canada’s Douglas Point reactor, developed under joint Indo-Canadian nuclear cooperation.

A significant design advantage of PHWRs is their use of thin-walled pressure tubes instead of the large pressure vessels found in other reactor types. This design distributes pressure boundaries across a large number of small-diameter pressure tubes, meaning that an accidental rupture would have much less severity compared to a large pressure vessel failure.