Why the future CANDU Reactor Will Probably Be a Superior Choice Over LWRs for Modern Energy Needs (in most countries)

In the quest for sustainable and efficient nuclear energy solutions, the choice of reactor technology plays a pivotal role. While Light Water Reactors (LWRs) have been the predominant choice for many years, CANDU (CANada Deuterium Uranium) reactors, or more broadly, Heavy Water Reactors (HWRs) present compelling advantages that could make them a superior option for most countries in the coming years. Let's explore why CANDU reactors stand out in the nuclear energy landscape.

1. Fuel Efficiency and Flexibility

One of the most significant advantages of CANDU reactors is their ability to use natural uranium as fuel. Unlike LWRs, which require enriched uranium, CANDU reactors can operate with natural uranium, reducing the need for complex and costly enrichment processes. This not only lowers fuel costs but also makes CANDU reactors accessible to countries without enrichment capabilities. Moreover, CANDU reactors are highly efficient in utilizing fuel. They extract more energy from the same amount of natural uranium compared to LWRs. This efficiency translates to better resource utilization, addressing one of the critical challenges in nuclear energy management.

2. Online Refueling

CANDU reactors offer the unique capability of online refueling. This means that the reactor can be refueled while it is still operating, without the need for shutdown. Minimizing and simplifying the activities that happen during outages, the Availability Factors of a NPP could be increased beyond the about 95% long term ceiling that the industry is used to. However, removing the need to shut down for refueling is not enough, since there are other activities such as inspections that may require the shutdown for maintenance to happen anyway. Nevertheless, online refueling gives the chance of optimizing operations to minimize or remove the other causes of outages. Through this process, online refueling offers an opportunity to improve Capacity Factors.

On the other hand, we should also mention that CANDUs have the outages due to refurbishments, that would reduce effective Availability Factors from their startup date to decommission. Refurbishment times can also be optimized, but in all fairness to LWRs we should mention that they don’t need to deal with as complex refurbishments as CANDUs (although when life extensions happen in LWRs, some components and parts are typically replaced, leading to some outages as well).

AP1000s (LWRs) are gen 3+ reactors very well-optimized for smooth operation and high Availability Factors. Since they have started operating worldwide, they have delivered better Availability Factors in general than the HWRs we have today. However, the CANDU fleet that we have today in the world is all gen3 or lower. I am optimistic that the next CANDU design iterations will be able to improve Availability Factors with respect to the CANDU reactors in operation today.

3. Energy Independence

In today's world, where relationships between companies, governments, stakeholders, and customers can be strained and competitive, achieving energy independence is crucial. Many countries do not have the capability to enrich uranium, making them reliant on external suppliers. This dependency can be risky, especially if the supplier has significant leverage or influence, which is often the case in geopolitical contexts.

Heavy Water Reactors (HWRs), such as CANDU reactors, offer a valuable solution. These reactors can use natural uranium, eliminating the need for enrichment. This independence from uranium enrichment not only reduces costs but also minimizes the risk of being pressured or bullied by suppliers.

For countries that cannot enrich themselves and already have an operating nuclear fleet with enriched uranium, factors such as economies of scale, workforce preparedness, and established supply chains may outweigh the energy independence argument. These countries might find it more practical to continue with their existing Light Water Reactor (LWR) technology due to the established infrastructure and trained workforce.

However, for countries that are yet to embrace nuclear power technology for the first time and would benefit from nuclear energy independence, Heavy Water Reactors (HWRs), such as CANDUs, would be preferable, CAPEX aside. For these nations, this plus the added benefits of HWRs in terms of fuel flexibility and safety make HWRs an attractive option.

4. Capital Expenditure (CAPEX) Considerations

While the initial capital expenditure for CANDU reactors has been a point of contention, recent cost trends suggest that the cost difference between CANDU and Light Water Reactors (LWRs) may not be as significant as previously thought. The horizontal orientation of the calandria in CANDU reactors allows for more efficient space utilization and potential reduction in reactor building volume in future design iterations such as MONARK. Additionally, the cost of heavy water, once a major economic disadvantage, is now a smaller fraction of the overall cost due to the high costs of Nuclear Power Plants construction in the West.

i. Efficient Space Utilization

Due to the horizontal orientation of the calandria and associated operations such as refueling, it may make more sense than in an LWR to also orient steam generators (SGs) horizontally or have compact SGs. This results in potential for reactor building (RB) volume reduction leading to a modest reduction in capital cost.

ii. Heavy Water Cost

The cost for "enriching heavy water" used to be a large slice in the CAPEX estimates for CANDUs and also in terms of $/kW, in the case of LWRs. This was pointed out as the main economic disadvantage from CANDUs. This was in a world where large LWRs were projected at $3,000/kW. Then an extra $1,000/kW only for the heavy water seemed like a lot (+33%). However, the West has not proven capable of completing an LWR in this century below $10,000/kW. Assuming the cost of enriching heavy water remains (which is a valid assumption given that the facilities exist, and it is mostly about using energy in the separation process), then the difference comes down to 10%, namely, engineering error. Now the capital cost estimate starts looking much more similar.

iii. Financial Cost

Financial costs (at equal construction duration) should be lower for a Heavy Water Reactor (HWR) than for an LWR given the risk of relying on an external Low Enriched Uranium (LEU) supplier is gone. This independence from external suppliers reduces financial risk and should lead to more stable and predictable capital costs.

Conclusion

While LWRs have served the nuclear energy sector well, the advantages of CANDU reactors make them a superior future technology of choice in many places. Their fuel efficiency, online refueling capability and potential for greater energy independence position CANDU reactors as a forward-thinking solution for countries aiming to achieve sustainable and efficient nuclear energy.

As the world continues to seek cleaner and more reliable energy sources, embracing CANDU technology could be a pivotal step towards a brighter and more sustainable future.

Call to Action

• AtkinsRealis: Please deliver and promote your technology. Consider innovative designs and arrangements to enhance the efficiency and appeal of CANDU reactors.

• Countries: Open your eyes to the benefits of Heavy Water Reactors (HWRs). Each nation has unique conditions, but the pursuit of energy independence (alongside energy security) should be a priority unless there are no viable options.