Why is the core-loading event of the Prototype Fast Breeder Reactor being hailed as a milestone?
The PFBR is a machine that produces more nuclear fuel than it consumes.
Its core-loading event is being hailed as a “milestone”.
PFBR will mark the start of stage II of India’s three-stage nuclear power programme.
In the first, India used Pressurised Heavy Water Reactors (PHWRs) and natural uranium-238 (U-238), which contains minuscule amounts of U-235, as the fissile material.
In nuclear fission, the nucleus of an atom absorbs a neutron, destabilises, and breaks into two while releasing some energy.
If the destabilised nucleus releases more neutrons, the reactor’s facilities will attempt to use them to instigate more fission reactions.
The heavy water in PHWR — water molecules containing the deuterium isotope of hydrogen — slows neutrons released by one fission reaction enough to be captured by other U-238 and U-235 nuclei and cause new fission.
The heavy water is pressurised to keep it from boiling.
The reactions produce plutonium-239 (Pu-239) and energy.
Only U-235, not U-238, can sustain a chain reaction but it is consumed fully in stage I.
In stage II, India will use Pu-239 together with U-238 in the PFBR to produce energy, U-233, and more Pu-239.
The Department of Atomic Energy (DAE) set up a special-purpose vehicle in 2003 called Bharatiya Nabhikiya Vidyut Nigam, Ltd. (BHAVINI) to implement stage II.
In stage III, Pu-239 will be combined with thorium-232 (Th-232) in reactors to produce energy and U-233.
Homi J. Bhabha designed the three-stage programme because India hosts roughly a quarter of the world’s thorium.
The three stages are expected to make the country completely self-sufficient in nuclear energy.
What does the reactor do?
PHWRs use natural or low-enriched U-238 as the fissile material and produce Pu-239 as a byproduct.
This Pu-239 is combined with more U-238 into a mixed oxide and loaded into the core of a new reactor together with a breeder blanket.
This is a material the fission products in the core react with to produce more Pu-239.
A breeder reactor is a nuclear reactor that produces more fissile material than it consumes.
In a ‘fast’ breeder reactor, the neutrons aren’t slowed, allowing them to trigger specific fission reactions.
The PFBR is designed to produce more Pu-239 than it consumes.
It uses liquid sodium, a highly reactive substance, as coolant in two circuits.
Coolant in the first circuit enters the reactor and leaves with (heat) energy and radioactivity.
Via heat-exchangers, it transfers only the heat to the coolant in a secondary circuit.
The latter transfers the heat to generators to produce electricity.
In a 2020 paper, former IGCAR scientist R.D. Kale wrote about several issues with getting this system to work as expected.
For example, according to him, personnel working with the PFBR had expected the reactor vessel could be preheated to 150 degrees Celsius in about a month based on theoretical calculations and tests with a mock-up.
But the process took more than a year in reality.
Why has the event taken so long to materialise?
The PFBR saga in India has been associated with numerous delays, cost overruns, and broken promises, and has accrued many critics.
The fast breeder test reactor (FBTR) at Kalpakkam is a testing ground for PFBR technologies.
It was built by 1977 but sanctions against India’s ‘Smiling Buddha’ nuclear test forced the use of a mixed carbide fuel over enriched uranium (which France was to deliver).
The former lowered the power output and changed operating conditions.
By the time the Indian government green-lit the PFBR in 2003, most people who worked on the FBTR were also nearing or had completed retirement.
What led to the delays?
The Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam, designed the PFBR.
Its original cost was ₹3,492 crore and the original deadline, 2010.
Six years later, the DAE sought more funds and an extended deadline, which the government granted in 2012 — ₹5,677 crore and commercial operations by March 2015.
The nuclear power establishment further pushed the deadline to the next year, then the year after that, and so on until by March 2020, the new deadline to commercialise was October 2022.
Even by 2019, its cost had ballooned to ₹6,800 crore.
In a 2014 audit, the Comptroller and Auditor General found BHAVINI had fumbled the procurement of some PFBR components by becoming inordinately dependent on the Nuclear Power Corporation of India, Ltd.
The result: the placement of a hundred purchase orders had a “median delay” of 158 days per order.
Other causes of delay included technical difficulties with the reactor coolant.
What are small modular reactors?
The delays brooked another potential complication in the form of Small Modular Reactors (SMRs).
These reactor designs have a maximum capacity of 300 MW, require less land, and accommodate more safety features.
Several countries are developing SMRs to complement conventional [facilities] since SMRs can be installed at reduced cost and time by repurposing.
According to National Institute of Advanced Studies, increasing SMRs’ contribution would require, among other things, amendments to the Atomic Energy Act (1962) “and other related statutes.
This to allow private sector participation “under the oversight of the Atomic Energy Regulatory Body (AERB), with both nuclear fuel and waste controlled by the DAE” according to international safeguards.
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