FAST BREEDER PROGRAMME :

AN INEVITABLE OPTION FOR ENERGY SECURITY

Dr. Baldev Raj

Director, Indira Gandhi Centre for Atomic Research

“Let us celebrate the success of our nuclear power development scientists and engineers and their partners in the industry for making the dream of fast breeder reactor a reality for the nation, which will lead the country towards total energy security within the next two decades. Let us empower the nation with quality power.”

Dr. A. P. J. Abdul Kalam

2004-Technology Day Speech, AIR

Vision of a 3-stage Nuclear Power Programme enunciated by Dr. Homi Jehangir Bhabha was indeed the beginning of a dream for energy security in the country. The vision took cognizance of the limited uranium and vast thorium resources within the country. The first stage, namely Pressurised Heavy Water Reactor Programme (PHWR) has now matured into a robust technology with the capacity factors touching 90% consistently. These reactors use natural uranium as the fuel which contains only 0.7% of fissionable Uranium-235. Hence, the PHWR programme cannot be taken beyond a power level of ~10,000 MWe based on the presently known and exploitable indigenous resources of natural uranium. In a fast neutron spectrum that exists in Fast Breeder Reactors (FBR) beside fission of Uranium 235, there is gainful conversion of the 99.3% Uranium-238 to Plutonium-239, which in turn is a fissionable material. When the fissile material produced is more than that consumed, the reactors are referred to as Breeder Reactors.The effective utilization of the indigenous uranium resources is therefore possible only through the FBR route, by which India can achieve a power capacity of 300,000 MWe. It was Dr. Vikram Sarabhai, who recognized the inevitability and complexity of FBR’s in India and put into action the second stage of country’s Nuclear Power Programme. For this purpose, he created a road map for a truly interdisciplinary research in reactor engineering, materials, chemistry, reprocessing, safety, instrumentation and other allied disciplines, which finally led to the establishment of the Reactor Research Centre, later renamed as Indira Gandhi Centre for Atomic Research (IGCAR).

Fast Breeder Test Reactor

The story of Fast Breeder Test Reactor (FBTR) is itself a proof of the strength and resilience of the Department. It is exemplified by landmark achievements in all facets right from design to commissioning and finally achieving the objectives. The agreement with CEA, France in 1971 was only for the transfer of the design of Rapsodie type reactor, training of personnel and transfer of manufacturing technology. The responsibility for construction was totally with India. FBTR includes the steam generator and associated steam system which was absent in Rapsodie. Except for the grid plate, one control rod drive mechanism, one sodium pump and raw materials for critical nuclear components, which were imported from France, all the other components were manufactured in India. Sodium purification rig was set up at this Centre and 150 tonnes of reactor grade sodium coolant for Fast Breeder Test Reactor was prepared from commercially available grade. The total indigenous content of FBTR is more than 80%, considered quite high in the light of the standards of Indian industries in the seventies and eighties./p>

New Fuel

The original design of MOX fuel with plutonium oxide (PuO2) and / uranium oxide (UO2) (with the latter enriched to 85%) was reviewed in the light of the embargo due to the Peaceful Nuclear Explosion (PNE) by India in 1974, denying supply of enriched uranium. It was a challenge to the start of the second stage programme of nuclear energy in India. It was also an opportunity to develop advanced fuels. The DAE took a bold decision to develop mixed carbide fuel with high Pu content. Being a unique fuel of its kind without any irradiation data, it was decided to use the reactor itself as the test bed for this driver fuel. The synergism between the different units of the department like BARC, IGCAR and NFC, has resulted in success of this bold initiative.

The reactor has been operated up to a maximum power 17.4 MWt. Eleven irradiation campaigns have so far been completed. The fuel has seen a burnup of 123.5 GWd/t (energy generated in the fuel multiplied by days of operation per tonne of fuel consumed) without failure. This has been possible by the encouraging results obtained from Post Irradiation Examination studies conducted on fuel subassemblies discharged at intermediate stages (25,50,75&100GWd/t). Based on extensive work done by multidisciplinary team, the burnup of level of 150 GWd/t is now a reality. In addition to its use as a self-driven irradiation facility for the Pu-rich monocarbide fuel, FBTR is being utilized as a irradiation facility for fuels and materials. Currently, FBTR is being used to irradiate the MOX fuel (29 % PUO2) chosen for PFBR (500MWe) to the target burnup of 100 GWd/t . These are truly international landmarks made possible due to interorganizational and interdisciplinary collaborative work.

Operation Experience

All the sodium pumps have been giving trouble-free service for more than 1,20,000 hrs. Sodium purity has been well maintained. Corrosion is so negligible that the engraved identification numbers on the fuel pins resident in the reactor for 18 years could be easily read in the hot cells during post-irradiation examination. The once-through serpentine steam generators have operated without any tube leak. The Steam Generator Leak Detection System has given trouble-free and continuous service. This success demonstrates our strengths in the areas of manufacturing technology, sensor development and reactor instrumentation.

Safety Experience

Several safety related engineering and reactor physics tests have been conducted in FBTR to validate the data and the codes used in design and safety analysis of the reactor. The completed physics tests include measurement of the various feed back coefficients of reactivity, effect of sodium voiding of the reactor, flux measurement above sodium and evaluation of performance of the failed fuel detection system. The completed engineering tests include study of the evolution of various reactor parameters during postulated incidents of high and low probabilities. A major low probability event was tested to assess the capability for removal of decay heat from the reactor by natural convection in the primary and secondary loops under conditions of non-availability of all the sodium pumps. All the tests have proven that the reactor is quite safe under all postulated incidental scenarios. The maximum annual activity released to atmosphere so far is 128 Ci. Cumulative occupational exposure so far is only 50 man-mSv (5 manrem). During the operation of FBTR, there has been no significant event of abnormal radioactivity release, personnel or area contamination thus confirming our conviction that the sodium cooled reactors give low radiation doses to operating personnel and low releases to environment.

Our Strength

The experiences in construction, commissioning and satisfactory operation for the past 18 years have demonstrated the mastering of the multi-disciplinary technology for energy production using a fast reactor and provided sufficient feedback to enable the launch of PFBR. Further, India has gained maturity in the design, operation and maintenance of FBR system. Most important, it has created a pool of specialists in the various disciplines related to complex technology of fast reactors.

PFBR

The preliminary design of the PFBR reactor was prepared in the early eighties. The choice of plant capacity 500 MWe was decided as the steam conditions of PFBR were close to 500 MWe thermal station. The higher plant capacity also meant taking advantage of economy of scale reducing cost of generation. The initial design had four heat transport loops feeding a total of 36 steam generators, 9 in each loop. There were four primary pumps and equal number of secondary sodium pumps with 8 sodium to sodium heat exchangers (IHXs) to transfer heat from primary circuit to secondary circuit before steam could be raised in the steam generators of the secondary circuit. A large part of the 1990s saw the design and engineering research & development groups going through the optimization phase, when a detailed look at reducing the number of loops and components was taken to produce a techno-economic design to demonstrate viability of such large plants without compromising availability and safety. The design that evolved had only two primary pumps, four intermediate heat exchangers (IHXs), two secondary heat transport loops and eight steam generators in all, making a substantial reduction of components from the earlier design.

In retrospect, there was a lot of advantage of the optimization process both for the designers and development engineers who got better insight in the design. In the area of sodium pump, a new hydraulic design has been developed based on extensive tests. Electomagnetic pumps and flow meters have been designed, built and tested in-sodium. With several sodium facilities for components testing, instrumentation qualification, sodium technology has reached a level of maturity at IGCAR. Starting from a 500 kW sodium test facility, the Centre now has the 5.5 MW steam Generator Test Facility. To understand the hydraulics within the primary pool of the reactor, a large test facility at 1/4 scale ( SAMRAT ) of the primary circuit, has been commissioned at this centre. Specialised thermal hydraulics and structural mechanics investigations have been carried through computer codes developed inhouse and validated through in house experiments carried out in sodium and water and also International Benchmark problems. All design basis events including off normal and accidental situations have been analyzed with these codes. Complex failure modes under thermo- mechanical, vibration, seismic and accidental loadings have been analyzed and structural integrity demonstrated for safe operation for a design plant life of 40 years. A boron enrichment facility has been operated to develop the process flow sheet for obtaining enriched boron for control rods for FBR. A flowsheet for obtaining enriched boron, extraction of elemental Boron-10 and manufacturing compact pellets for PFBR has been finalized and an inter-organizational team from the department of atomic energy (BARC, IGCAR, HWB) is working on the project.

In the area of Control and Instrumentation, the fault tolerant real time computer systems have been developed and commissioned successfully in FBTR and new improved systems are in the pipeline for PFBR. Capabilities to simulate and test the different instruments and system have been developed inhouse. A full scope Training Simulator is being built for operator training.

Reprocessing

Closing the fuel cycle is a key element of the FBR programme, without which it is not possible to realise growth in nuclear power. Reprocessing activities started with processing of irradiated thorium rods for separating U-233.This U-233 has been used for fabrication of Mixed Oxide fuel test assembly for irradiation in FBTR, before use in PFBR. A pilot plant scale reprocessing facility has been commissioned and reprocessing of FBTR fuel has commenced successfully. The flowsheet, as well as equipment development was based on extensive numerical and experimental simulation, carried out indigenously. The reliable and trouble-free operation of the equipment has given the confidence to take up the challenge of large reprocessing plant matching throughputs of fuel from PFBR.

Manufacturing Technology Development

Manufacturing technology development for full size components for PFBR was thought to be crucial for successful construction of the reactor without cost and time over-runs. In the light of this realisation, a programme of manufacturing development of components like the main vessel, inner vessel and the roof slab of the reactor, so also the full scale control and safety rod mechanism, the invessel fuel transfer machine, steam generator etc. were taken up with selected Indian industries. These components and several others have undergone or undergoing various tests including those in liquid sodium. A comprehensive programme to address problems related to inservice inspection of reactor components has resulted in development of non- destructive tests (NDT) using ultrasonic, eddy current, magnetic particle testing, thermography etc..

Materials Development

The development of indigenous materials for core structures, steam generator and other components of the reactor is vital for the FBR programme and comprehensive range of facilities for studies of metallurgical properties have been set up. This development was undertaken to assure availability of indigenous sources in case of embargo. All the materials (SS304,316,316 LN, Modified 9 Cr-1 Mo) have been produced and have undergone tests for carbon transfer, corrosion etc. in sodium. Also the mechanical behaviour of these materials have been measured in sodium at high temperatures and have certified their performance. Weld ability of steels is another important area where extensive R&D has been carried out and mechanical behavior of welds under monotonic and cyclic loading conditions established. Welding consumables have also been developed indigenously.

PFBR Launched

The above approach of development has led to a competitive design backed by vast amount of tests and mastering of the manufacturing technology. For the R&D, many collaborative works were carried out with educational institutes, R&D labs. and public and private sector companies. The Centre also has more than 100 research scholars at any time to support the programme. The review of design by two eminent expert groups, has led credence to design maturity. By 2000 AD, the Department felt that the time to launch construction had come. The exercise of getting clearances from the Ministry of Environment, Planning Commission, Ministry of Finance, Power etc. was started. The financial sanction for the project was given by the Cabinet in September 2003. The total project cost sanctioned is Rs.3492 crore and the expected unit cost would be about Rs.3.25 in the year 2010 when the plant is commissioned. The PFBR plant is being constructed by a newly formed company called BHAVINI (Bharatiya Nabhikiya Vidyut Nigam Limited) which comprises experts in project management and construction drawn from NPCIL and the technological expertise from IGCAR, BARC and other DAE units. This is indeed an example of optimizing and synergising the resources to meet the challenging assignment in a cost-effective manner. We are confident of completing the project with less than sanctioned cost and stipulated time thus holding the potential to reduce cost of energy production by PFBR.

Beyond PFBR

Vision 2020 of the Department envisages a series of four 500 MWe FBRs after PFBR.

The cost studies indicate that a series construction of four at a given site would reduce the cost by about 25% compared to PFBR and construction time could be brought down to 5 years from 7 years. Constant improvements in design, operation and material development would certainly result in better capacity factors of the plants. Future plans are to go in for 1000 MWe FBRs with improved design features and optimisation at all stages. All efforts are focused on developing high burn-up and high breeding fuel, advanced structural materials for longer life of FBR’s upto 60 years, development of better shielding materials, etc. Closing the fuel cycle with high efficiency in an environmentally benign manner is the priority in the programme. The challenges ahead are exciting and highly rewarding to realise dreams of Dr. Bhabha through the courageous path shown by Dr. Sarabhai. Interdisciplinary Colloboration, Interorganisational synergy, multitasking by experts and the mobility of personnel from one type of activity to another, have undoubtedly provided the impetus for growth of FBR’s in this centre.

Currently, international community has identified liquid sodium cooled Fast Breeder Reactor as one of the five advanced and innovative types of reactors to meet the future energy needs in safe and cost-effective manner. However, India had unwavering faith in FBRs and pursued the path with courage and conviction since 1970s. It can be said with confidence that energy security for India, in the next few decades, would be realized through FBRs.

Mud mat filling at Prototype Fast Breeder Reactor excavation site June 2004