IGCAR scientists will soon realise their dream of designing and building a 500mw prototype fast breeder reactor. It's not a mean achievement
Kalpakkam: The mood is jubilant and gung-ho at the Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam, 80 kms off Chennai. Why? IGCAR scientists are in the process of realising their dream of designing and building the 500mw prototype fast breeder reactor (PFBR).
Not many even dreamed that PFBR would ever become a reality. The eighties saw India joining the select club of nations (sixth in the world) to possess a fast reactor when it commissioned the 13mw fast breeder test reactor (FBTR) with French assistance at Kalpakkam. But it was the graduation from the test reactor to a commercial one that delayed the process.
For nearly 20 years the PFBR project just remained on paper. But the last two years saw the paper project gaining momentum and early this year the pre-project work started at Kalpakkam. With that IGCAR is actualising the second stage of India's three-phase nuclear power programme.
"Even before FBTR went operational we tried to get Plan funds for PFBR but didn't succeed," says Dr S M Lee, director, safety research, health physics, information services, instrumentation and electronics group. At that time the government wanted to see the test reactor's performance before committing funds as India was kept under the 'atomic sanctions' list by the West.
Nevertheless, the delay and the denial of technology by the West propelled the IGCAR scientists to go in for fail-proof research, component testing and getting their design validated by the Atomic Energy Regulatory Board (AERB). It is also true that the IGCAR scientists, for a brief period, waltzed with other research activities till the present director, Dr S B Bhoje, provided direction to the organisation.
"It is taxpayers' money and should be used judiciously towards achieving the organisation's goals," he says. The atomic research centre as on March 2002 incurred a cumulative expenditure of around Rs 1,220 crore. As PFBR is the forerunner for the fast breeder reactors to be built in the future IGCAR is all set to generate handsome royalty revenues.
Unlike other atomic power plants, which are owned by the Nuclear Power Corporation (NPC) and the Department of Atomic Energy (DAE), the Rs 2,800-crore PFBR project will be executed by a separate company - likely to be called as Fast Breeder Reactor Corporation - to be funded through a mix of equity and market borrowing.
Says Bhoje: "The government wanted us to meet the project cost partly from the market, hence a funding mix of 75 per cent from the government, 5 per cent from NPC and the balance from market borrowings towards the fag end of the construction."
According to him the responsibility for research and development (R&D) and design will rest with the IGCAR scientists while NPC officials will bring in the management expertise. The nine-member board of the new corporation will have representatives from IGCAR and NPC.
Given this background, it is but natural that the IGCAR scientists' chests swell with pride while talking about their fast reactor, while officials like Y C Manjunatha, associate director, engineering services group, is all charged up to take care of the logistical issues in PFBR construction.
A Hanuman jump
The PFBR project showcases the IGCAR scientists' capabilities in several aspects. The first one would be the 38-time capacity scaling up from the French Rapsodie-Fortissimo reactor.
"It is really a Hanuman jump," agrees Bhoje. Even Western countries have not scaled up their test reactor to such an extent. This should be viewed in the context that PFBR is not just a replication of FBTR on a larger scale, as both the reactors are different in several aspects.
For instance, the seventies vintage FBTR is a sodium-cooled loop-type reactor, whereas PFBR is a liquid sodium cooled-pool type. (A loop-type reactor will have the primary pumps and sodium to sodium-heat exchangers outside the reactor vessel whereas in the pool-type reactor they will be housed inside, which is safer.)
Secondly, FBTR is fired by plutonium-uranium carbide fuel (India's own innovation) whereas PFBR will be fired by the globally known plutonium-uranium oxide fuel. From the safety point of view PFBR has two shutdown systems against one in FBTR though the number of trip parameters have been brought down in the former.
Reasons Lee: "As a matter of caution we had incorporated many automatic reactor tripping parameters in FBTR that were not there in the original Rapsodie design. But it turned out to be a nuisance, as the number of spurious tripping became high-affecting the power plant availability."
"Without experience from a test reactor, it is impossible to launch the PFBR project as an indigenous design," adds S C Chetal, director, reactor engineering group.
The run-up to the jump
But it was really a marathon run-up for the IGCAR scientists to reach the jump pit. For, it took them nearly 20 years of research, lab tests, applying the FBTR and other fast-reactor experience in designing PFBR.
Says Bhoje, an authority on fast-breeder reactors: "Being the first indigenously designed reactor, it required considerable theoretical and experimental R&D to ensure satisfactory performance of reactor components during their lifetime."
The experimental research he talks about is nearly building a mini-prototype for the prototype fast reactor as the scientists not only wanted to be sure of their design but also get AERB's approval smoothly.
Blessed with a sizeable research kitty IGCAR went about building testing systems like the steam generator test facility (outlay: Rs 32 crore), a structural mechanics lab with a shake table to qualify components against earthquake-like events. Further, all the crucial components and welding joints were subjected to creep-and-fatigue damage, dictating their life and hence the reactor life.
"The four areas that complicates the fast breeder reactor technology are: handling of liquid sodium (its purity and controlling any kind of ingress into sodium), controlling oxygen, steam generation and equipment handling," says R P Kapoor, associate director, reactor operations and maintenance group and the operational head for FBTR and the Kamini reactor.
The learning from operating the FBTR enabled Kapoor and his team to give the necessary inputs for the PFBR design, AERB's licensing procedures, commissioning programme, operation and maintenance issues, training of men and personnel planning.
Furthermore, the experience of handling 75kg sodium leakage last year also came in handy. The leakage was contained to the inner chamber and the reactor was brought back into operation in three months' time.
"Most of the failures in sodium-cooled fast-breeder reactor can be traced to the steam generator. Managing the steam on one side and sodium on the other is a critical task," says Dr Baldev Raj, director, materials, chemical and reprocessing groups.
About the new steam-generator facility, G Vaidyanathan, associate director, engineering development group, says: "The design and fabrication experience of the steam generator that is available with the FBTR reactor is not suitable for extrapolation to a large size. As this is a critical equipment we had to undertake a modest development and testing programme."
Innovative designs to cut capex
The cardinal rule followed by Bhoje and his team in designing PFBR was to cut costs so as to make the unit energy cost comparable with that of pressurised heavy water reactor (PHWR) power costs. One of the reasons thrown up against fast breeder reactors is its cost.
With the global experience in running fast reactors available, cost-competitive studies between thermal power plants and the former were made. The capex of fast reactor was reduced by design innovations without compromising safety aspects and making it more compact.
For example, the number of loops and primary pumps were reduced to two in the PFBR plant as against four in the earlier design. "We also reduced the number of steam generator units to eight from 36 and the tube thickness of heat exchangers were also reduced," says Chetal.
The other area of cost reduction is the choice of oxide fuel - under fabrication at the advanced fuel fabrication facility, Tarapur - instead of the carbide fuel that fires the existing test reactor.
The economics of a nuclear power plant depends on the residence period and the fuel rod burn-up in the reactor. "Higher the residence period and burn-up, better the returns," says Dr V S Raghunathan, associate director, materials characterisation group.
The use of carbide fuel in FBTR was a forced one as the French were not willing to supply fuel, post-Pokhran I. For the first time in the world plutonium-uranium carbide fuel was used to power a fast reactor.
Says Bhoje: "The high fuel burn-up will further reduce the fast breeder reactor's operational cost. While nuclear power would cost Rs 3.40 in 2010, the thermal power per unit will be Rs 4." Adds Chetal: "The minor and major design innovations would result in cost savings of around Rs 300 crore."
However any benefit of the economical design can be actualised only if there are capable vendors. And for the IGCAR scientists, vendor development was a major challenge as the demand of big reactors is different and the components should have high-tolerance levels.
Perforce they had to wear the vendor shoes to find out solutions as each rupee saved decides the project's economic viability (See: 'Medium-sized but efficient' ). As the heat level inside the reactor vessel will be more than 550 degree Celsius, the IGCAR scientists decided to look out for a different grade of high-radiation-resistant stainless steel.
Says Dr S L Mannan, associate director, materials development group: "To fabricate the 12.9m diameter reactor vessel (FBTR's size is 3m) with minimum welded joints, the stainless steel plate should be of 30mm thick and 2-3 metre wide and 8-10 metre long. But Indian steel mills do not normally roll out metal sheets of that size."
The problem was solved by sourcing the stainless sheets from Steel Authority of India's Durgapur unit and getting the rolling and finishing works done at the Rourkela plant. "The total steel that would be required for the PFBR project will be around 4, 000 tonnes," he says.
Similarly efforts were taken to successfully localise sodium suppliers as IGCAR has the capability to purify locally purchased sodium to the reactor grade. With other things tied down, the current focus is to reduce the construction time so that the payback period is improved and the overall project cost is cut. The next challenge for the IGCAR scientists is the reprocessing of the spent fuel at Kalpakkam, thereby closing the nuclear fuel cycle.
A proud Bhoje says IGCAR's plans and processes relating to PFBR were studied by French and Russian consultancy agencies, which have already given the green signal. "I am sure we are on the right track," he sums up.
PFBR in a nutshell
|Electric Output ||500 mw|
|Core height ||1000 mm|
|Core Diametre ||1900 mm|
|Fuel ||Plutonium-Uranium Mixed Oxide|
|Pins per fuel subassembly ||217|
|Fuel pin outer diameter ||6.6 mm|
|Reactor life ||40 years|
|Control rod material ||Boron Carbide|
|Sodium Inventory ||1100 ton|
|Containment Building ||RCC Rectangular|
Medium-sized but efficient
The fabrication ability and expertise of domestic engineering industries was the one aspect that decided PFBR's capacity. At a time when other countries are building fast reactors of a bigger size (600mw-plus) India's PFBR's capacity is 500mw.
Says Bhoje: "When PFBR was conceived in 1982, the biggest turbine in India then was the coal-fired 500mw one. We decided to stick to that size as the domestic component manufacturers like BHEL [Bharat Heavy Electricals] and others were conversant with that. Nevertheless, as per our design the unit energy cost of a 500mw reactor is comparable with that of other power-generation technologies."
Adds Chetal: "The other reason is to commercialise our design faster without losing more time. This will be the standard size for few more units to come. Later we may go for 1,000mw plants."
As per initial estimates the total project cost is put at Rs 2,800 crore and if one takes into account the escalations, the project should not exceed Rs 3, 400 crore. The 10th Plan has allocated Rs 1,800 crore for the PFBR project. The payback period is eight years at Rs 3.40 per unit, including three paise for decommissioning the plant after 40 years.
Though officials expect the PFBR plant to clock a plant load factor (PLF) on par with pressurised heavy water reactors (PHWR, more than 80 per cent), officially PLF is estimated at 62.8 per cent - much lower than the standard 68 per cent - as it is the first of its kind in India.
PFBR's success and the subsequent building of fast breeder reactors would make IGCAR one of the richest R&D organisation in India. According to Bhoje, IGCAR will charge all other fast breeder reactors a royalty of the three paise per unit generated.
also see : Why three-stage
nuclear power programme