Small Modular Nuclear Reactors

Bring up “nuclear power” at a social gathering and you may get a few odd looks or chatter about mushroom clouds or the Chernobyl and Fukushima accidents. The promise of nuclear power as a safe and reliable power source has a somewhat uneven past, ever since the Soviets connected the first power plant to their electric grid in June 1954. Even with today’s green energy push, nuclear remains the stepchild – not quite  fitting in with wind, solar, hydro, and geothermal; but still with tremendous potential when the wind won’t blow or the sun doesn’t shine.

Many technologies that have been around for half a century usually see several multiples of expansion and benefit from economies of scale and wider public adoption. But not nuclear. Nuclear power has met so many roadblocks – from safety concerns to NIMBY fever to cost overruns – the overall worldwide use of nuclear has decreased from approximately 18% to 10%. While several countries have embraced nuclear, such as France at 71% and Slovakia’s 55%, the overall trend has been noticeably down over the recent past. But with soaring fossil fuel prices and a rush to net carbon neutral, maybe that trend has a chance of reversing if the public is willing to give nuclear another look with Small Modular Nuclear Reactors (or SMRs).

SMRs, prefabricated modular reactors, may be a game-changer for the energy industry. Several countries – including the United States, Canada, China, India, Russia, and the United Kingdom – are working on unique designs for these “plug and play” small reactors that can be scaled up or down depending on electric demand. Unlike traditional reactors, SMRs are factory made, already contain passive safety measures, take up one percent of the space of a traditional reactor, and can be shipped via a standard shipping container to remote reaches of the world.

SMRs vs. Nuclear Power Reactors

SMRs already offer several key advantages over traditional reactors. But two significant advantages are: their small size precludes the need for a large land area or exclusion buffer around the plant for emergencies; and they operate at a lower thermal setting which enables the design to include automatic passive fail-safe systems to shut the reactor down automatically, without oversight or instructions in case of emergency. The reduced footprint, built in fail-safe system, and low fuel loads make SMRs environmentally friendly and less likely to cause a major radiological catastrophe.

Key Advantages of SMRs:
  • Prefabricated factory scalable modules with plug-in design
  • Built-in passive safety features; no external power sources required
  • Take up less space; can be partially buried or enclosed underground
  • Small reactor core safer to cool during an emergency
  • Small amount of fuel used; less frequent refueling
  • Pre-regulatory approval of smaller Emergency Planning Zone fixed to site boundary; smaller footprint
  • Aesthetically more acceptable than larger reactors
  • Worldwide settings; remote areas; marine-based (immersed or barge-mounted) possible.
  • Waste management handling and practices infrastructure already in place; new waste streams can be incorporated into existing management

Waste Management/New Waste Streams

SMRs come in several designs and contain a cooling method (water, gas, liquid, metal, or salt). The core reactor relies on either thermal or fast neutron spectrum to provide power. SMRs include sodium fast reactors; lead fast reactors; and high-temperature, gas-cooled, water-cooled, and molten salt-cooled reactors.

Waste management and new waste streams generated by the SMRs are currently being studied. As with any power technology, the concern about what to do with the wastes requires careful consideration and environmental impact assessments.

Given the smaller scale of SMRs, waste streams and handling are anticipated to be less than traditional reactors. Moreover, some SMRs are designed with an easily replaceable reactor vessel – with spent fuel that can be changed out on-site with a new vessel, without separating the spent fuel.

But improved SMR designs may bring different methods of cooling that produce new waste streams, not currently anticipated. For example, some more recent designs produce radioactive wastes – including halide salts, halogen off-gases, graphite pebbles, and dust – that may create new intermediate or high-level waste streams requiring additional handling and care.

Advanced countries that have managed large reactors will likely have the expertise to handle these multiple waste streams and have the infrastructure in place. Several challenges may occur in countries that do not already have a nuclear program – including building out of fuel management, storage, and minimization practices. To address these issues, newcomer countries will be required to conduct more research and development work on the fuel cycle and to effectively manage spent fuel and radioactive wastes from the SMRs.

Environmental Risks

Several environmental risk factors must be considered when determining if SMRs are a viable option for power generation in each country. These factors include:

  • Managing inventory of numerous SMRs will be challenging, if technology becomes widespread.
  • Potential transboundary impacts from SMRs near borders between countries must be considered.
  • Transportation routes for wastes may cross international boundaries.
  • Stakeholder involvement of all parties needs to be addressed throughout the planning, operational period, and decommissioning lifecycle.
  • Potential for radiological and non-radiological accidents during the life cycle of the SMRs and releases of wastes to the environment.
  • SMRs submerged in water/contact with groundwater present potential for leakage and release of radioactive materials.
  • Siting SMRs in earthquake, flood or other known natural disaster areas should be avoided to avert accidents.

What’s Next on the Horizon?

SMRs may have a bright future in the energy industry. Globally, there are approximately 50 different types of SMR designs and concepts at different stages of development. Three SMR plants are already in advanced stages of construction in Argentina, China and Russia – with anticipated operational start dates in 2022-2024.

American developers – including GE Hitachi Nuclear Energy, Bill Gates-backed TerraPower, X-Energy, and Hyperion Power Generation – are currently working on SMRs. Canadian ARC Nuclear is also developing an      exportable, factor-produced, 100-megawatt sodium coolant nuclear reactor with fuel costs fixed for more than 20 years. And Russia is working on a floating nuclear power plant that has started producing electricity in a remote region of  Russia.

HETI…Here to Help

HETI staff continue to monitor new and proposed changes to SMR technology, as well as applicable regulations and standards, to better understand potential environmental risks and issues with this new technology. HETI’s extensive engineering and environmental experience enables us to assist our clients in understanding the risks and changing regulatory environment of SMR and other emerging technology.