Friday, March 03, 2017

How To Design A Nuclear Power Reactor, the A, B, C, Ds

Some Guru-gyaan from the, then, Chairman of India's Atomic Energy Commission [AEC].

FACT: Fissioning 1 gram of Uranium-235 facilitates as much electricity generation as burning 3 Metric Tonnes [3,000,000 grams] of Coal. For a country, whose per capita electricity consumption, today, barely breaches the 1000 mark, at 1075 kWh, against the world average of 3104 kWh, speaking nothing of Iceland's 54799 kWh, it needs no elucidation, therefore, that India must generate electricity, on gargantuan scales, to pull its prodigious, "unwashed masses" out of the literal darkness, it dwells in. Against this backdrop, bearing testament to the acute historical foresight of its policy-planners, India embarked on the Nuclear way from the onset, supplementing the Greenhouse Gas emitting Coal-fired Power Plants.

Advanced Heavy Water Reactor - AHWR - Block Diagram - India

Elaborating on India's game-plan towards achieving 100% electrification, is this exceptionally informative presentation titled, How the design of an advanced Nuclear Reactor evolves, delivered by Dr. Srikumar Banerjee, who, then, headed the Atomic Commission [AEC] of India, the nodal agency of all things Nuclear. Recommend that you watch it from the start, though if you jump to 15 mins 40 secs, you'd be able to skip some of the mathematical talk at the beginning.

Recorded in 2011, at the Indian Institute of Science [IISc], in Bengaluru, this free-wheeling talk throws light on design evolutions & factors influencing Specification of India's Reactors. One example, in the 1960s India lacked indigenous know-how for fuel enrichment. To retain program autonomy it, therefore, decided to use Natural Uranium [NU], as fuel, in its Pressurised Heavy Water Reactor [PHWR]#. NU, however, containing only 0.7% fissile Uranium-235, needed a larger proportion of Neutrons, to optimise burning.  Heavy Water, with its lower Neutron absorption, thus, came to be used as Moderator & Coolant  in the PHWR, as well as the successor, the Advanced Heavy Water Reactor [AHWR] [Moderator only]. The AHWR, critically, typifies the, aforementioned, design evolution - while the older PHWR have horizontally positioned coolant tubes, necessitating an external Pump for operation, the vertical pipes in the AHWR allow for the Light Water coolant to flow through the Reactor under the physical effect of convection, requiring no external assistance.
Perhaps, since it coincided with the mishap at TEPCO's Fukushima Nuclear park, he talked at length about passive safety features in its Reactors, like the AHWR. For more details about this aspect of the AHWR, the paper, titled, Role of Passive Safety Features In Prevention And Mitigation Of Severe Plant Condition In Indian Advanced Heavy Water Reactor, throws a lot of light.

Amongst nations with established atom splitting street creds, India helms the Thorium reserves list - given that it would be "capable of feeding 500 years  of  nuclear  power  generation", India can, quite rightly, be called the Saudi Arabia of Thorium, minus the kingdom's regressive social mores, of course. While Thorium itself is fertile, it can be transmuted into fissile Uranium-233, for use in future Reactors. Towards this end, India has embarked on a one-of-a-kind 3-Stage Nuclear Power programme. Highlighting this undertaking are its Fast Breeder Reactors [FBR]. They are an interesting concept for generating more fuel than consumed - think of a bike that burns a litre of Petrol to transports you &, additionally, produces more than a litre of a comparable fuel. That, my friend, is the underlying philosophy of what a FBR does.
With the Prototype Fast Breeder Reactor [PFBR] expected to go online in October, this year, it has set its sight on the the larger capacity 600 MWe Commercial Fast Breeder Reactor [CFBR], also known as FBR-600, 2 of which will be co-located alongside the PFBR in Kalpakkam, Tamil Nadu.
Some personal satisfaction to be derived here - while public mention of the 600 MWe Reactor began appearing circa 2015, the Blog noted it, first, 2 years earlier, in 2013.

The Nuclear energy programme, has factored in Indian Manufacturing Companies' drive to "up their game", to demonstrate competency in utilising newer processes like Narrow Gap Welding & Pull-out technology to fabricate Steam Drum nozzles, as well as acquiring greater capabilities, such as manufacturing of large-sized Reactor Pressure Vessels [1000+ MWe] - L&T, at its plant at Hazira, will embark on what is, currently the preserve of a handful of companies globally.
Designing a Nuclear Reactor demands a multi-disciplinary approach, encompassing Reactor Physics, Thermal Hydraulics, Stress Analysis, Material Science & Technology, Control & Instrumentation, followed by uncompromising testing & validation. As Dr. Banerjee so matter-of-factly put it out, a Reactor design is work of "maybe, a couple of 100 people, working for 20 years". A handful of people, spending nearly half their professional lives to realise a system, that would enlighten many millions for a 100 years to come.
# - Today, however, indigenous enrichment technology, allows for use of Highly Enriched Uranium [HEU] [around 40% enrichment], as fuel in India's Nuclear-powered/capable Arihant-class submarine.