Small Modular Reactors

Table of Contents

Context: Recently, the NITI Aayog published a report titled ‘the role of small modular reactors in the energy transition’.

Small Modular Reactors Background

Nuclear Energy

Nuclear energy is a type of energy that is generated by the process of nuclear reactions- either nuclear fission or nuclear fusion.
The energy released during these reactions can be harnessed and used to produce electricity, heat, or other forms of energy.
Nuclear fission: It is a process in which the nucleus of an atom is split into two or more smaller nuclei, releasing a large amount of energy in the process.
- This process is used in nuclear power plants to generate electricity.
- One example of nuclear fission is the reaction that occurs in a nuclear reactor when uranium atoms are split into smaller atoms.
Nuclear fusion: It is a process in which two or more atomic nuclei come together to form a single, more massive nucleus, releasing a large amount of energy in the process.
- This process occurs naturally in stars, including our own sun.
- One example of nuclear fusion is the reaction that occurs in a hydrogen bomb.

Advantages of Nuclear Energy

Role of Nuclear Energy in Energy Transition across the Globe

Energy transition is the process of revamping global energy systems through rapid introduction of low-emission energy supply technologies, and aggressive penetration of non-fossil-based energy sources in the primary energy mix.
According to the International Atomic Energy Agency (IAEA), as of April 2023, 413 nuclear power reactors with a total net installed power generating capacity of 368 GW(e) are in operation globally, which is projected to rise to 871 GW by 2050, more than doubling the current capacity.
The share of nuclear power generation is nearly 10% of the global electricity mix.
As per IAEA, the nuclear power has avoided the CO2 emissions of 70 Gt over the past five decades and it continues to avoid CO2 emissions of about 1 Gt annually.
The IEA acknowledges the role of nuclear energy in energy transition. The UN Economic Commission for Europe (UNECE) has stated that nuclear power is an “indispensable tool” for achieving the Sustainable Development Goals (SDGs).

Various Types of Nuclear Reactor Technologies

The nuclear industry has been developing several types of nuclear reactors with progressive increase in reactor capacity and improvement in safety features, performance, and economics.
At present, nuclear power reactors of various types are in operation like PWRs, BWRs, PHWRs, FBRs, HTGRs etc.
- Pressurized Water Reactor (PWR): They use enriched uranium as fuel and employ water as both coolant and moderator.
- Boiling Water Reactor (BWR): BWRs are similar to PWRs but differ in their design. In BWRs, the water in the primary circuit boils directly due to heat generated by fission.
- Pressurized Heavy Water Reactor (PHWR): They use heavy water (deuterium oxide) as both the coolant and moderator.
- Fast Breeder Reactor (FBR): It is a type of nuclear reactor that uses fast neutrons to sustain the nuclear chain reaction.
- High-Temperature Gas-Cooled Reactor (HTGR): It is a type of nuclear reactor that uses helium gas as a coolant and graphite as a moderator.
Among the various reactor types, PWRs are at the top with more than 300 operating reactors in the world at present.

Emergence of Small Modular Reactors (SMRs)

Roots of SMRs can be traced back to 1940s-1950s when small capacity nuclear reactors of various designs were used for military purposes.
As per the IAEA, the SMRs are advanced nuclear reactors with a power generation capacity ranging from less than 30 MWe to 300+ MWe.
SMRs are:
- Small – physically a fraction of the size of a conventional nuclear power reactor.
- Modular – making it possible for systems and components to be factory-assembled and transported as a unit to a location for installation.
- Reactors – harnessing nuclear fission to generate heat for electricity production or direct application.
Many countries have active national programmes dedicated to SMR design and technology development with a view to deploy them by 2035 with extensive global cooperation.
SMR designs can be categorised into six types based on the basic nuclear technology employed in the design:
- Land-based water-cooled SMRs: This category includes SMRs that use water as a coolant and moderator, following the principles of pressurized water reactors (PWRs) commonly found in large nuclear power plants.
- Marine based water cooled SMRs: SMRs in this category include the water-cooled SMR designs for deployment in a marine environment. This can be achieved in the form of floating units installed on barges or ships.
- High temperature gas-cooled SMRs: SMRs from this category can provide very high temperature heat of more than 750 degrees Celsius and thereby higher efficiency in electricity generation.
- Liquid metal-cooled fast neutron spectrum SMRs (LMFRs): SMRs in this category include designs based on fast neutron technology with different coolant options including helium gas and liquid metal coolants like sodium, lead and lead-bismuth.
- Molten Salt Reactor SMRs (MSRs): SMRs in this category are based on molten fluoride or chloride salt in the role of coolant.
- Microreactors (MRs): MRs are very small SMRs designed to generate electrical power typically up to 10 MW(e). Different types of coolant, including light water, helium, molten salt and liquid metal are adopted by microreactors.

Key features and benefits of Small Modular Reactors (SMRs)

Size and Portability: SMRs are smaller and more compact than conventional reactors, allowing for easier transport, installation, and scalability.
Enhanced Safety Features: SMRs incorporate advanced safety features to ensure the protection of the public and the environment. These features include passive cooling systems, advanced control mechanisms, and robust containment structures.
Flexibility and Grid Resilience: Their smaller size and modular nature make them suitable for deployment in remote areas or as a supplement to existing power grids, enhancing grid resilience.
Reduced Capital Costs: The modular design of SMRs allows for standardized manufacturing processes, potentially reducing construction costs.
Potential for Decentralization: SMRs offer the potential for decentralized power generation, allowing communities or industries to have their own local sources of electricity.
Integration with Renewable Energy: SMRs can complement renewable energy sources, such as solar and wind, by providing baseload power and maintaining grid stability during periods of low renewable generation.

Challenges associated with SMRs

Technology choice issue: Many SMR technology alternatives are available at present with varying requirements of supply chains, regulation, operations, etc. For large scale commercial deployment of SMRs, the technology choice needs prioritization.
Supply chain issues: As with big LWRs (Light Water Reactors), the supply chain is an important factor in SMR competitiveness. Supply chains for the SMR industry may need consolidation in order to capitalize on economies of scale, as witnessed in the aviation industry.
Safeguards challenges: In most countries, novel SMR technologies will require the application of international safeguards, potentially requiring the development of novel or customized technical measures that demand time and resources, typically in collaboration with the relevant governments and industry.
Potential disadvantages: SMRs also produce radioactive waste from spent fuel and require spent fuel storage & disposal facilities. Apart from the technological and cost aspects of such a requirement, this requirement can also lead to socio-political resistance.
Public perception and engagement: Nuclear power has faced traditional opposition due to the potential consequences of a nuclear disaster, notwithstanding the low likelihood of such events.

Way Forward

Technology Development and Demonstration: Continued research and development efforts are necessary to refine and optimize SMR designs. Prototyping and testing of SMR modules are crucial steps in validating their performance and safety.
Cost Optimization and Standardization: Achieving cost competitiveness is essential for the widespread adoption of SMRs. Standardization of designs, components, and manufacturing processes can help drive down production costs through economies of scale and improved quality control.
Regulatory Harmonization and Safety Assessment: Regulatory frameworks need to be adapted or developed to address the unique characteristics of SMRs. This includes updating safety assessment methodologies to consider multi-module designs and emergency planning zones.
Skilled Workforce Development: Ensuring a skilled workforce across the value chain of SMR development, construction, and operation is vital.
Strategic Partnerships and Collaboration: Collaboration among national laboratories, research institutions, private companies, and government departments is crucial for technology development, safety assessments, regulatory harmonization, and research coordination.
Consensus Building and Stakeholder Engagement: Engaging relevant stakeholders, such as communities, environmental organizations, and industry representatives, through transparent communication and participatory processes can help foster acceptance and support for SMR projects.