The nuclear power sector has demonstrated a resurgence owing to more and more Asian countries opting for it. Hence, zirconium alloy – a suitable metal for nuclear reactor that can withstand corrosion and sustain itself amidst intense radiation, will be much in demand in the coming years. At the moment, India is looking at becoming self-sufficient with respect to Zirconium Alloy required in its nuclear power plants. But, India should work towards exploiting the increasing global demand as well.
Keeping in mind India’s requirement for zirconium alloy a plant was established in the Nuclear Fuel Complex, Hyderabad. Presently, Australia is the leading producer of zirconium and another Asian country China is taking big strides in research and development of activities around this alloy. In many cases China has already shifted to the phase of industrial production from research phase. India too should try to compete with China in this field. India’s production capacity of zirconium as compared to that of China is low at the moment.
Nuclear energy has established itself as a viable source of power generation thus leading to increased demand for zirconium alloy. With industrialisation and development, global electricity demand is expected to rise further. At the same time, global environmental challenges have resulted in states opting for low carbon energy and nuclear power is the one of the major energy sources with low carbon footprint. The global nuclear power market is expected to reach a Compound Annual Growth Rate (CAGR) of 8.9 per cent.
The Asia-Pacific region has been driving the growth in the nuclear energy sector forestalling the impediment caused due to the Fukushima incident. China is already going big time to tap the potential of nuclear energy, whereas Japan also plans to utilise nuclear power in long term. India too has realised the importance of nuclear energy and have concentrated on reviving its nuclear energy sector especially after the Indo-US nuclear deal.
Hence, it is a given that the zirconium alloy market will grow in the Asia Pacific given the demand for zirconium alloy in China, India, Japan, Indonesia and Australia. In fact, excluding China, the Asia-Pacific zirconium market is expected to grow at CAGR of 5.7 per cent.
Zirconium – the silver lining of the nuclear reactor
The use of zirconium in nuclear reactor dates back to the 1970s, when a US Navy officer Admiral Rickover decided to use the material in nuclear reactor for nuclear propelled ships and submarines. These reactors were Pressurised Water Reactors (PWRs) that needed a material that could withstand corrosion at high temperatures for longer period. Zirconium could not only withstand corrosion, but could also sustain itself amid intense radiation without absorbing neutrons required for nuclear reaction. Since then, countries opting for nuclear energy programme have preferred zirconium alloy as a suitable metal for their nuclear reactor. The demand for this alloy in the market is huge and it is expected to continue to do so in the near future.
Zirconium is a silver grey material used to clad nuclear fuel rods that contain uranium meant for nuclear energy. Use of zirconium alloy enables the transfer of heat easily and hence, nuclear reactors become safer, reliable and efficient. They also have high melting point, high conductivity and fracture toughness; and are elastically rigid.
Nuclear reactors that use zirconium metal has one objective- either to slow the fission process or to hasten the fission process. When fission takes place, atoms are split creating heat and enables the production of electricity. Zirconium metal is extracted from zirconium ore through the process of carbochlorination of zircon or even plasma dissociation of zircon at high temperatures. Zircon has to be separated from hafnium which is an expensive technical process and given their similarity, separation is also technically challenging process.
Zirconium also has low absorption cross section of thermal electrons and is highly ductile, hard and corrosion resistant. The purer the zirconium alloy is, the more difficult it is for it to corrode. Zirconium is also used for structural applications like in reactor core that include pressure tubes and support grids, core structure material, positioning framework, plug, and also moderator. This is why with the growing demand in nuclear energy, there has also been an increase in demand in zirconium metal that is used in nuclear reactors as zirconium alloy. While other options like ceramics have been considered as an alternative time and again, zirconium has proved its mettle as a reliable metal. According to reports, the world zirconium market is expected to grow at CAGR of 6.91 per cent from 2016-2020. From 2018-2023, the market is expected to grow at CAGR of 6.21 per cent.
Zircon (ZrSiO4) is the only commercially relevant zirconium mineral. It occurs in plenty in the beach sand deposits in various parts of the world and is almost always recovered in beach sands minerals processing as a by-product of the titanium minerals. In India, there are vast deposits of zircon in the coastal beach sands of Kerala, Tamil Nadu and Orissa where it occurs to the extent of 5-9 per cent along with many other valuable minerals. Besides zirconium, zircon contains 2–2.5 per cent hafnium, which is altogether similar to zirconium in its chemical behaviour.
Some Hiccups
The cost of zirconium is reported to be somewhere around USD 60-80 per kg, but its price volatility is a major concern. The volatility was experienced when in 2010 China announced that it would reduce export of rare earth materials and zirconium alloy was one such material. This resulted in skyrocketing price of rare earth materials and it was only after the World Trade Organisation rule against the export restriction, did China go back to normalcy.
Zirconium alloy also has its disadvantages. They are often exposed to irradiation-induced damage. During service in nuclear reactors, these alloys are exposed to neutron irradiation that can affect their micro-structural evolution, and the mechanical and corrosion properties of zirconium alloys that adversely affects the lifetime of zirconium alloy components in reactors. There are also concerns of management of additional fission gas inventory, and how zirconium alloy property changes and increased fission gas inventory would affect the fuel behaviour in reactors in case of Reactivity Initiated Accidents and Loss of Coolant Accidents.
During the Fukushima incident in Japan in 2011, it was seen, that the hydrogen built up was due to the hot steam that came into contact with overheated nuclear fuel rods that was covered with the cladding of zirconium alloy. Zirconium alloy reacts with steam when it is hot to produce hydrogen that can become hazardous during any loss-of-coolant nuclear accident. For this reason, ceramics have also become a choice for nuclear reactors, but its demand is not yet as much as of zirconium alloy. Silicon carbide, a compound of ceramic, is expected to withstand very high temperature in a Fukushima kind of event that would provide plant operators additional time before materials start to fail.
However, despite the advantage of silicon, zirconium alloy is still in most demand given its above mentioned benefits and the wider usage of zirconium alloy has led countries to continue with this alloy for their nuclear reactors. Silicon in reactors are still at experimental stage and hence, would take some years to capture the market that zirconium alloy has.
(Debalina Ghoshal is Independent Consultant specialising in nuclear, missile and missile defence issues.)
