The start of construction of the Kudankulam-1 nuclear power plant back in 2002 marked the beginning of India’s future operation of nuclear power plants equipped with Russian VVER-type nuclear reactors. The realities of the current day require a reasonable question to be asked: “To what extent Kudankulam 1-6 units meet modern requirements for safety and economic independence?”
The strategic vision adopted in December 2014 to strengthen cooperation in the peaceful use of atomic energy between Russia and India provides that at least 12 Russian-designed power units should be put into operation in India over the next 20 years. The Government of India has reiterated multiple times that it is actively looking for sites for the construction of new power plants.
However, the apprehensions about the safety of nuclear power plants continue to color the public perception regarding further development of nuclear energy, Fukushima incident has in particular bolstered those concerns. As such, it is important to outline the lessons learned from the incident that has been applied to ensure better safety mechanisms for nuclear power plants.
One of the largest accidents of the 21st century in the peaceful nuclear power industry occurred eleven years ago, in March 2011, at the Fukushima-1 nuclear power plant. The Fukushima-1 NPP is equipped with six BWR power units. As a result of the accident, nuclear power plants with units 5 and 6 were not damaged, however, enormous damage was caused to units 1, 2, 3 and 4.
Russian experts have divided the lessons of the accident at the Fukushima-1 NPP into two groups – technical and related to the human factor / organizational aspects. At the same time, they were considered as an integral part of a single system, and such a conclusion made it possible to implement all the “post-Fukushima” safety requirements at the Kudankulam units.
Currently, Kudankulam is the only nuclear power plant in India that operates Units 1 and 2 of the Pressurized Water Reactor (PWR). Kudankulam NPP is equipped with VVER-1000 PWR units of the third generation of AES-92 model of Russian design. VVER is an abbreviation for “Water Water Energy Reactor” which means a water-cooled water-moderated power reactor. Units 3 and 4 are at the final stage of construction. Additional security measures are being introduced at Units 3 and 4 at the request of India. These safety measures will make it possible to withstand even higher seismic, climatic and technical impacts. The construction of power units 5 and 6, belonging to generation 3 plus, has begun.
The key feature of the new power units is the implementation of a number of technical solutions based on a combination of both active and passive safety features (i.e. without human intervention and without the use of energy sources), including a passive heat removal system, hydrogen – combiners, core trap, hydraulic accumulators and fast boron injection system. These technical solutions, according to the generally accepted criterion “Total frequency of severe core damage”, bring the current project as close as possible to the parameters of fourth-generation projects in terms of safety.
The concept of defense in depth with four protective physical barriers – the fuel matrix, the fuel element cladding, the primary circuit with the reactor pressure vessel and the containment – is used to prevent the release of radioactive materials into the environment. There are five levels of technical and organizational measures to ensure the integrity and effectiveness of these barriers, so that in any critical situation, radioactive fission products can be contained inside the containment building.
Due to tsunami concerns, it is worth noting how a calamity similar to Fukushima is avoided there. In the project, the design basis flood level of 5.44 meters is used (for reference – tsunami in December of 2004 rose to a level below 3 meters). Every NPP equipment is located significantly at a higher altitude. For instance, the containment building is located at 8.7 meters and diesel generators (flooding of these in Fukushima was a key event of the accident) – at 9.3 meters. Thus, Kudankulam NPP is secured from severe earthquakes and tsunami as well as from the complete loss of power supply on the site.
TVEL Fuel Company of Rosatom and the Indian Nuclear Energy Corporation signed an additional agreement to the contract for the supply of fuel in December 2020. The agreement is aimed at the implementation of a comprehensive engineering project, including the introduction of a new nuclear fuel TVS-2M and an extension of the fuel cycle from 12 to 18 months for both operating VVER-1000 reactors of the Kudankulam NPP. One of the key advantages of TVS-2M, which makes them more reliable and economical: due to the welded frame, fuel assemblies in the core retain their geometry, spacer grids protect fuel claddings from fretting wear (preventing depressurization), and an additional spacer grid makes fuel units more vibration-resistant.
It should be noted that despite the current geopolitical situation and global economic slowdown, as of today, no deviations from the obligations and delivery schedule during the construction of the Kudankulam NPP are observed and are not expected. All emerging issues are resolved in close cooperation with the advising state authorities of India, to ensure timely compliance with the schedules for the supply of equipment and components.
A lot of useful experience was gained during the construction phase of blocks 1 and 2 Kudankulam, so the construction of units 3, 4, 5 and 6 was optimized together with the project partners. All deliveries from Rosatom were made right on time, even despite the impact of Covid-19. Units 5 and 6 are scheduled to be completed in 66 months and 75 months, respectively. According to this schedule, both units will be completed by 2027. Thus, when completed, the Kudankulam nuclear power plant will become not only the largest nuclear power plant in India, but also the largest enterprise for the production of clean energy in the South Asia region.
Views expressed above are the author’s own.
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