Waiting for the Fast Breeder Reactor

Enrico Fermi believed that whichever country mastered liquid metal fast breeder reactor (LMFBR) technology would end up leading the world. This view is still shared by many in the Indian nuclear establishment, although the journey to roll out the second stage of India’s three-stage nuclear programme (TNSP), which envisages the setting up of extensive LMFBR-based generation capacity has proved longer than initially envisaged.

The flagship effort for this stage, the 500 MWe Prototype Fast Breeder Reactor (PFBR) at Kalpakkam still hasn’t reached first criticality, though physical construction commenced in 2004 and was complete by 2015. Expectedly, engineering problems were encountered by BHAVINI, the special purpose vehicle set up by the Department of Atomic Energy (DAE) to implement the PFBR project, though it seems to have surmounted these for now. That is just as well, since the very growth of the second stage of TNSP depends on the successful completion of the PFBR project.

LMFBRs have long been the promised land for nuclear energy, given their potential to greatly reduce the radioactive waste management burden besides facilitating the extraction of a much greater quantum of energy from extant uranium resources by ‘breeding’ more fissile material (fuel) than they consume. In the Indian scheme of things, they are also the pathway to large-scale thorium utilization in the third stage.

The TNSP involves building reactors using natural and enriched uranium in the first stage, plutonium (Pu)-driven LMFBRs in the second and thorium-232/uranium-233 (Th-232/U-233) cycle based ‘thermal breeders’ in the third. LMFBRs of the second stage will be loaded with plutonium and reprocessed uranium from the first stage as fuel. It is only after adequate LMFBR capacity has been built up that Th-232 will be introduced in the blanket regions of these LMFBRs to breed U-233, which will serve as fuel for thorium-based breeders in the third stage.

But while the first stage of TNSP has been underway for decades, the second stage is yet to deliver a working LMFBR. That will only happen when PFBR overcomes commissioning issues and is synchronized with the grid. According to DAE, the delay “is primarily owing to the augmentation of certain additional assessments and checks on the installed equipment prior to commencement of their commissioning, which have essentially emanated owing to both increased regulatory requirements and as a matter of abundant caution”. That caution proved necessary with key sodium equipment showing deviations from expected performance during tests.

That is why the projected date for criticality has slipped to the mid-2019. First, problems had to be rectified with electro-magnetic pumps used in one of the secondary sodium loops, which took almost six months. Just as the loop was re-commissioned with modified pumps, the main secondary sodium pump started displaying certain deviations and was replaced with a spare. Worse, the Transfer Arm, which is a part of the fuelling machinery, also had to be modified after trials and has been re-installed since.

BHAVINI is currently working towards commissioning of the primary sodium system, which will be followed by fuel loading and then approach towards first criticality. Safety considerations will mean that even if first criticality is achieved by the middle of 2019, PFBR will only be slowly raised to full power. Grid synchronization may take a while longer, and that will have consequences of its own.

For one, it may delay work on the two 600 MWe Commercial FBRs (CBRs) projected to commence construction as ‘twin-units’ on a site next to PFBR by 2021. Detailed engineering for these reactors by the Indira Gandhi Centre for Atomic Research (IGCAR), the designer of PFBR, and BHAVINI can only be completed once adequate feedback from full power operation of PFBR is available and incorporated into the CBR design.

The CBR design is a significant modification over the baseline PFBR with a view to reducing capital costs and construction time, while increasing safety and plant life. In comparison to PFBR, the CBRs are envisioned to see a 25% reduction in material inventory, simplified fuel handling, optimal shielding, the use of a more economical grade of austenitic stainless steel, enhanced burn-up and a higher plant load factor throughout their operating lives.

Indeed, with PFBR, all that DAE really needs is to demonstrate safe full power operation. Neither power generation at competitive rates nor a high-breeding ratio is really a goal for PFBR. As such, BHAVINI has already begun construction of a site assembly workshop and electrical substation for the two CBRs.

Preliminary layout drawings are being studied by BHAVINI’s engineers who had earlier been involved in the erection and installation of PFBR. Work on the Fast Reactor Fuel Cycle Facility, which will close the fuel cycle for PFBR by reprocessing its spent fuel, is also proceeding apace. The only piece of the puzzle that needs to fall into place is the PFBR itself.

(The writer is Chief Editor, Delhi Defence Review)