Kakrapar-4 nuclear reactor attains criticality

Subject :Science and Tech

Section: Nuclear technology

Context:

The fourth unit of the Kakrapar Atomic Power Project (KAPP-4) in Gujarat, with 700 MWe capacity, started a controlled fission chain reaction and thus became critical. Kakrapar is situated about 80 km from Surat.

Details:

NPCIL, part of India’s Department of Atomic Energy, indigenously built 700 MWe pressurised heavy water reactors (PHWRs), the largest of their kind in India.
These reactors use natural uranium as fuel and heavy water as coolant and moderator, similar to other indigenous PHWRs operated by NPCIL.
Unit-3 of KAPP started producing commercial electricity from August 30.
The reactors met Atomic Energy Regulatory Board conditions and achieved criticality, signifying safety and functionality.
- Criticality is the normal operating condition of a nuclear reactor, in which nuclear fuel sustains a fission chain reaction.
- A reactor achieves criticality (and is said to be critical) when each fission releases a sufficient number of neutrons to sustain an ongoing series of nuclear reactions.
Indian industries supplied equipment for the reactors, which boast advanced safety features like steel lining and a passive decay heat removal system.
NPCIL currently operates 23 nuclear reactors with 7,480 MWe capacity, with nine units under construction and plans for 10 more reactors in the pre-project phase, totalling 7,000 MWe.

India’s Three-Stage Nuclear Power Programme:

India’s three-stage nuclear power programme was formulated by Homi Bhabha in the 1950s to secure the country’s long term energy independence, through the use of uranium and thorium reserves found in the monazite sands of coastal regions of South India.

Stage 1- Pressurized heavy water reactor (PHWR): The first stage involved using natural uranium to fuel PHWR to produce electricity and Plutonium-239 as a byproduct.
- Also the byproduct plutonium-293 would be used in the second stage.
Stage 2- Fast breeder reactor (FBR): The second stage involves using plutonium-239 to produce fuel, which would be used in Fast Breeder Reactors. Plutonium 239 undergoes fission to produce energy. Once a sufficient amount of plutonium-239 is built up, thorium will be used in the reactor, to produce Uranium-233. This uranium is crucial for the third stage.
Stage 3- Advanced Heavy Water Reactor (AHWR): The main purpose of stage-3 is to achieve a sustainable nuclear fuel cycle.
- The advance nuclear system would be used a combination of Uranium-233 and Thorium.
- Thorium absorbs the neutrons, which can more efficiently produce more Plutonium in Fast Breeder Reactor for a faster growth.
Thus, the ultimate objective of the above programme is to create capacity to use Thorium for sustainable production of nuclear energy and make India energy independent.