Understanding CANDU Technology and Its Relevance for Emerging Markets

CANDU reactors—acronym for CANada Deuterium Uranium—represent a distinct pressurised heavy water reactor design originally developed by Atomic Energy of Canada Limited (AECL) and now marketed globally by Candu Energy Inc., a subsidiary of SNC-Lavalin. With over 500 reactor‑years of operational experience across Canada, South Korea, Romania, China, India, Argentina, and Pakistan, the technology has proven its reliability in a range of regulatory environments. For emerging economies seeking to diversify energy portfolios and reduce dependence on fossil fuels while maintaining baseload capacity, CANDU offers strategic advantages: it can utilise natural uranium without requiring enrichment, enables online refuelling that supports high capacity factors (often exceeding 85 %), and its modular pressure‑tube architecture facilitates local manufacturing and adaptability to different fuel cycles, including thorium. However, deploying any nuclear reactor in a nation with a developing regulatory infrastructure introduces complex licensing challenges amplified by the unique characteristics of the CANDU design. The heavy water coolant and moderator, the horizontal fuel channels, and the specific safety case required for pressure‑tube reactors demand a licensing approach that diverges significantly from the more common light water reactor (LWR) pathways. For countries with limited or no prior nuclear power experience, establishing the legal, technical, and institutional foundations for a CANDU construction licence requires a structured, multi‑year effort that must be planned from the outset.

The Regulatory Mosaic in Emerging Markets

Nuclear licensing is founded on a framework of laws, regulations, standards, and guidance documents that collectively ensure a reactor can be built, operated, and decommissioned without posing unacceptable radiological risk to workers, the public, or the environment. In nations with mature nuclear programmes—such as Canada, the United States, France, Japan, and the Republic of Korea—this architecture has evolved over decades and is supported by independent regulatory bodies, well‑established codes, and a large pool of expert reviewers. By contrast, emerging markets often approach nuclear power with regulatory systems that are either nascent or based on outdated institutional models. The absence of a robust, independent nuclear regulatory body is arguably the most significant obstacle. A credible regulator must be politically and financially autonomous, staffed with qualified engineers, health physicists, geologists, and legal specialists, and empowered to issue binding decisions without interference from government ministries or project proponents. Building such an organisation from scratch typically takes a decade or more. During the interim, a country may rely heavily on the vendor’s home regulator—often the Canadian Nuclear Safety Commission (CNSC)—or on generic International Atomic Energy Agency (IAEA) safety standards. This dependency can create tension between the sovereign right to make licensing decisions and the practical necessity of leveraging external expertise. A well‑designed transitional arrangement, formalised through a bilateral agreement, can help bridge this gap without compromising regulatory independence.

Many emerging economies lack comprehensive nuclear legislation that clearly defines the responsibilities of the licence applicant, the safety principles to be satisfied, the process for public hearings, and the liability regime in the event of an accident. Without a primary nuclear law, it becomes ambiguous which agency holds the mandate to review the preliminary safety analysis report, how environmental impact assessments are integrated into licensing, or how local communities can participate in decision‑making. Investors and reactor vendors require regulatory predictability; if the rules can change mid‑project, the financial risk becomes unmanageable. For CANDU reactors, this challenge is compounded by the fact that the design has been licensed primarily in jurisdictions with detailed prescriptive requirements for heavy water systems, pressure‑tube surveillance intervals, and tritium management. A country that simply adopts a generic LWR regulation may inadvertently create gaps that delay the application or force the vendor into costly design revisions. Addressing these gaps requires drafting dedicated regulatory guides, referencing the IAEA’s Specific Safety Requirements series (e.g., SSR‑2/1), and often seeking bilateral assistance from Canada under a Nuclear Cooperation Agreement. Early legislative action, including enactment of a nuclear law that is consistent with the Convention on Nuclear Safety, is a prerequisite for a predictable licensing pathway.

Developing Indigenous Review Capability

The technical depth required to assess a CANDU licence application extends well beyond a generic safety review. Regulators must understand the neutron physics of heavy water moderation, the thermal‑hydraulic behaviour of horizontal fuel channels, the aging mechanisms of zirconium‑alloy pressure tubes, and the implications of a positive coolant void coefficient. Training a cohort of inspectors and analysts requires sustained financial and institutional commitment. Emerging countries frequently send regulators to training programmes organised by the IAEA, the CNSC, or through bilateral technical cooperation. Peer review missions such as the IAEA’s Integrated Regulatory Review Service (IRRS) help identify gaps and provide a roadmap for strengthening the regulatory body. However, the transition from having a few trained individuals to a fully competent technical support organisation—one that can independently question the vendor’s safety case and conduct its own confirmatory analyses—is a multi‑year endeavour. It often extends the pre‑licensing phase by three to five years, which must be factored into project schedules. Establishing a dedicated nuclear safety research programme, in partnership with international laboratories, can accelerate capability building while also addressing site‑specific questions.

Technical Hurdles Specific to CANDU Licensing

Licensing a CANDU unit involves demonstrating that the design meets fundamental safety objectives: controlling reactivity, removing heat from the core, and confining radioactivity under all operational states and accident conditions. The CANDU’s horizontal fuel channels, low‑pressure heavy water moderator, and two independent shutdown systems—shutoff rods and liquid poison injection—create a safety architecture that differs markedly from a pressurised water reactor. For an emerging‑market regulator, this unfamiliarity can lead to a protracted review process, especially if the regulator attempts to cross‑reference the safety analysis with international practices that are heavily LWR‑oriented. The safety analysis report must cover a broad spectrum of potential initiating events, including large‑break loss‑of‑coolant accidents (LOCAs), which in CANDU behave differently because of the distributed fuel channels and the separate moderator cooling system that can act as an additional heat sink. The regulator must be convinced that the analysis methods, computer codes, and experimental validation are appropriate. This often requires the vendor to submit detailed code‑to‑code comparisons, participate in international benchmark exercises organised by the OECD Nuclear Energy Agency (NEA), and sometimes construct scaled test facilities to demonstrate key phenomena such as fuel‑channel ballooning or moderator circulation under accident conditions. The licensing schedule should allow for iterative question‑and‑answer cycles that can extend over two to three years.

Fuel Cycle Flexibility and Associated Licensing Complexities

One of the CANDU’s strongest attributes is its ability to utilise different fuel cycles: natural uranium, slightly enriched uranium, recovered uranium from reprocessing, and even thorium‑based fuels. While this flexibility makes the reactor attractive for countries concerned about fuel supply security, it introduces significant licensing complexity. Each fuel cycle option presents its own safety case regarding reactor physics, source term estimation, and waste characteristics. If a country initially licenses a plant for natural uranium but later contemplates switching to an advanced fuel, a major licence amendment may be required—one that involves new radiological consequence assessments, revised emergency planning zones, and possibly updated containment analysis. The regulator must have the capacity to review fuel qualification programmes, irradiation performance data, and the thermal‑mechanical behaviour of novel fuel under accident conditions. For an emerging country with limited resources, this can become a significant bottleneck, potentially delaying the entire project. A prudent approach is to license the initial core with a well‑established fuel type and to include a framework for licensing future fuel changes early in the regulatory process, allowing for a phased review that does not hold up construction.

Heavy Water and Tritium Management

The CANDU reactor’s inventory of heavy water—amounting to several hundred tonnes in the moderator and primary heat transport system—creates unique licensing obligations. Heavy water is expensive and must be maintained at high chemical purity and isotopic concentration. The regulator must approve procedures for heavy water upgrading, leak detection, and emergency recovery to minimise economic losses and ensure safety. Moreover, neutron activation of deuterium produces tritium, a radioactive isotope of hydrogen that can permeate through materials and pose occupational exposure and environmental release concerns. The safety case must demonstrate that tritium releases during normal operation and design‑basis accidents remain within authorised limits. This requires robust containment and ventilation systems with tritium‑resistant barriers, as well as environmental monitoring programmes specifically calibrated for tritium pathways (e.g., tritiated water vapour in air and soil). For countries without previous heavy water reactor experience, establishing these programmes means building new laboratories for liquid scintillation counting, training radiation protection staff in tritium dosimetry, and engaging with local health authorities to set baseline levels. The licensing schedule must also allow for the procurement of heavy water from a limited number of global suppliers—primarily Canada and Argentina—and for the logistics of handling a hazardous substance that is subject to export controls under the Nuclear Suppliers Group guidelines.

Safety Assessment and Emergency Preparedness

Modern nuclear licensing places strong emphasis on deterministic safety analysis, probabilistic safety assessment (PSA), and defence‑in‑depth. For CANDU reactors, the probabilistic assessment must address specific vulnerabilities such as pressure‑tube rupture, calandria tube failure, or moderator drain scenarios. While a full‑scope PSA can provide quantitative insights into risk, developing the model requires detailed plant‑specific failure data and initiator frequencies, which may not be readily available for a first‑of‑a‑kind design in a new country. Emerging‑market regulators may lack experience in reviewing PSA results or may insist on overly conservative assumptions, leading to iterative rounds of questions that add years to the licensing timeline. One effective strategy is to conduct a joint PSA review with an experienced regulatory body, such as the CNSC, under a technical cooperation agreement. This accelerates mutual understanding of risk‑significant sequences and helps focus resources on the most important safety upgrades. Additionally, the regulator should require a living PSA that is updated throughout the design and construction phases, so that the final risk profile reflects as‑built conditions.

Emergency Planning Zones and Site Selection

A critical step in licensing is defining the emergency planning zones (EPZs) around the site. The size of the EPZ depends on the source term used in the safety analysis and on the effectiveness of engineered safety features. CANDU plants have demonstrated robust containment integrity, and filtered venting systems can be incorporated to reduce potential offsite releases. Nevertheless, emerging countries face challenges in demonstrating that the chosen site meets exclusion zone requirements and that local infrastructure can support an effective emergency response. The regulator must assure itself that the siting criteria address external hazards such as earthquakes, flooding, and extreme weather—all of which require site‑specific data that are often sparse in developing regions. Conducting geotechnical surveys, seismic hazard assessments (using probabilistic seismic hazard analysis), and hydrological modelling can take several years and must be integrated into the early licensing stages to avoid costly delays later. The IAEA’s Safety Guide NS‑G‑3.3 on site evaluation provides a useful framework, but its adoption must be supplemented with local meteorological and geological studies. In many emerging markets, it is advisable to initiate site characterisation well before the licence application is submitted, possibly under a separate site permit.

Cybersecurity and Physical Protection

Security considerations are an integral part of the licensing package. CANDU reactors incorporate digital control and protection systems that must be evaluated against cyber threats, especially given the increasing sophistication of state‑sponsored and criminal cyber actors. Emerging markets may not yet have comprehensive cybersecurity regulations for industrial control systems, making it necessary to develop new requirements in parallel with the licence review. The regulator should issue specific cybersecurity guidelines that align with standards such as IEC 62443 and with the IAEA’s Nuclear Security Series. Physical protection of nuclear material, though less challenging for natural uranium facilities than for enrichment plants, still requires a robust design basis threat (DBT) analysis and an approved security plan. The regulator must certify that the physical protection system meets international obligations under the Convention on the Physical Protection of Nuclear Material and its 2005 Amendment. The IAEA’s International Physical Protection Advisory Service (IPPAS) can assist countries in building this part of the licensing regime. A practical recommendation is to engage IPPAS early, before the licence application, so that any gaps in physical protection can be addressed without delaying construction.

Political and Economic Factors Shaping Licence Schedules

Political stability and the strength of government commitment are often the most decisive factors in whether a nuclear project proceeds on schedule. In emerging markets, energy policy can shift rapidly with changes of administration, and a new government might suspend licensing processes, renegotiate contracts, or even cancel the project entirely. The long lead time for nuclear licensing—often 5 to 10 years before first concrete—magnifies the impact of political risk. To mitigate this, vendors and host governments typically negotiate inter‑governmental agreements that provide a stable legal platform for the project. These agreements cover nuclear liability, intellectual property protection, taxation, and the repatriation of spent fuel or its storage arrangements. For CANDU technology, the Canadian government’s willingness to enter into a bilateral Nuclear Cooperation Agreement is a prerequisite for any export licence under the terms of the Nuclear Non‑Proliferation Treaty (NPT). The absence of such an agreement stalls the licensing process and prevents the transfer of technical data needed for the safety review. Therefore, early diplomatic engagement—often starting years before a request for proposal is issued—is critical.

Financing, Cost Recovery and Economic Regulation

Nuclear power plants are among the most capital‑intensive infrastructure projects, and their licensing costs can be substantial, covering regulatory fees, environmental studies, legal services, and the expenses of maintaining a project team over many years. Emerging economies typically seek export credit financing, development bank loans from institutions such as the World Bank or Asian Infrastructure Investment Bank (under specific climate‑related mandates), or vendor financing to manage upfront costs. Lenders demand that the licensing roadmap is credible and that the plant will be insurable under international nuclear liability conventions. The economic regulator—sometimes separate from the nuclear safety regulator—must approve the project’s tariffs or power purchase agreements to ensure cost recovery. If the licensing process drags on, construction costs mount, financing charges accumulate, and the project can become economically unviable. This adds pressure on the safety regulator, which must resist any temptation to cut corners while still maintaining an efficient review. One mechanism to align incentives is to adopt a staged licensing process in which the regulator issues a site licence first, then a construction licence, followed by an operating licence, with clear milestones that allow investors to assess progress and release funding in tranches.

Non‑proliferation and Safeguards Commitments

Every CANDU exported to an emerging market operates under a comprehensive safeguards agreement with the IAEA, and often an Additional Protocol. The design’s inherent use of natural uranium simplifies some aspects of safeguards because enrichment facilities are not present on site, but the online refuelling capability introduces complexity for nuclear material accountancy. The IAEA must be able to verify that all irradiated fuel remains accounted for and that no undeclared production of plutonium is taking place. The host state must establish a State System of Accounting for and Control of Nuclear Material (SSAC), which the regulator or a separate authority oversees. Licensing applications must demonstrate how the facility will accommodate IAEA inspector access, containment and surveillance equipment, and sample collection without compromising safety or operations. The process of concluding a safeguards approach—which includes developing a facility attachment and verifying the design—can extend the licensing timeline if the host country’s SSAC is still under development. Early engagement with the IAEA’s Department of Safeguards, ideally during the pre‑licensing phase, helps ensure that safeguards requirements are incorporated into the design from the start rather than retrofitted later.

The Role of International Collaboration and Vendor Support

Recognising these multifaceted challenges, reactor vendors and international bodies have developed a range of support mechanisms. Candu Energy, for instance, typically provides a comprehensive licensing package that includes a generic safety analysis report (GSAR), environmental assessment templates, quality assurance programmes, and a training curriculum for the regulator. However, the vendor cannot substitute for the sovereign decisions of the nuclear regulator. Therefore, emerging countries frequently turn to the IAEA for the Milestones Approach, a phased methodology that guides a nation through 19 infrastructure issues—from nuclear safety and legislation to stakeholder involvement and procurement. The IAEA’s Milestones document is widely regarded as the reference framework for new entrants and is often incorporated into the roadmap presented during licence hearings. The Agency’s peer reviews and advisory missions provide an independent check on progress and help build confidence among all stakeholders.

Bilateral Partnerships and Regulator‑to‑Regulator Cooperation

Direct cooperation between the vendor country’s regulator and the receiving state’s regulator is one of the most effective ways to harmonise expectations and reduce duplication of review. Canada’s CNSC engages in various bilateral activities, such as secondments, joint safety reviews, and training workshops. For example, the CNSC has maintained cooperative programmes with regulators in Argentina and Romania—both established CANDU operators—providing valuable insight into licensing renewal and power uprate processes. Such relationships can be formalised through memorandums of understanding (MoUs) that allow for information exchange and mutual recognition of safety assessments where appropriate. The World Association of Nuclear Operators (WANO) also contributes by sharing pre‑startup peer review experiences, which, while focused on operational readiness, feed into the licensing process by confirming that the plant is being built to high standards. These forms of international collaboration help build institutional memory and can meaningfully shorten the review cycle, especially for a country licensing its first nuclear plant.

Capacity Building Through Regional Networks

Regional nuclear networks, such as the Asian Nuclear Safety Network (ANSN) or the African Nuclear Regulators’ Forum (FNRBA), provide platforms for sharing regulatory practices and developing common guidelines. Emerging markets benefit from these networks by accessing translated safety standards, participating in regional training courses on CANDU‑specific topics such as pressure‑tube integrity management, and benchmarking their regulatory processes against neighbours that are further along in their programmes. The IAEA’s Technical Cooperation programme funds many of these activities and provides expert missions to individual countries. In a region where a country has already licensed a CANDU unit—for instance, Romania for the Cernavoda plant—others can draw on that real‑world precedent to streamline their own assessments. The safety analysis report from a reference plant, adapted to site‑specific conditions, can serve as a starting point, significantly reducing the volume of original documentation required. However, regulators must remain vigilant to ensure that adaptation does not overlook unique local hazards, such as different seismic or climatic conditions.

Strategies for Successful CANDU Licensing in Emerging Markets

Moving from challenges to solutions, there are concrete steps that host governments, regulators, and vendors can take to facilitate a predictable and thorough licensing process for CANDU reactors. The starting point is a formal government commitment to establish a strong, independent regulatory body with secure funding and clear legal authority. This body should be in place well before the vendor submits a licence application, giving it time to draft regulations, hire and train staff, and conduct preliminary site investigations. Early engagement between the regulator and the vendor is vital; pre‑application meetings can clarify expectations, identify knowledge gaps, and agree on the formats for submissions, reducing the likelihood of later requests for additional information that stymie progress. A regulatory project plan, with agreed milestones and timelines for review, should be developed and publicly communicated to manage stakeholder expectations.

Customising the Licensing Framework Without Diluting Safety

International safety standards are the baseline, but each country must tailor its regulations to its legal system, industrial capacity, and societal preferences. For CANDU licensing, this can mean issuing specific regulatory guides on heavy water chemistry, pressure‑tube inspection intervals, and tritium dose assessment. It can also involve adopting a graded approach where the depth of review is proportional to the risk significance of the system, as recommended in IAEA Safety Guide GS‑G‑1.3. The CNSC’s REGDOC series offers a starting template, but emerging markets should adapt those documents rather than adopt them wholesale, ensuring that local requirements are met while avoiding unnecessary regulatory burden. By building flexibility into the framework—such as allowing alternative acceptance criteria if supported by risk‑informed justification—the regulator can keep the licensing process moving without compromising safety. A transparent process for proposing and approving deviations from prescriptive requirements helps maintain both safety and schedule.

Transparent Communication and Public Involvement

Nuclear projects often face public scepticism, and a licence hearing can become a focal point for opposition. A licensing strategy that includes early and ongoing dialogue with local communities, municipalities, and non‑governmental organisations can reduce friction. Fact‑based communication about the CANDU’s safety features, its emergency planning zones, and the environmental monitoring programme is essential. Public hearings should be accessible, with documents available in local languages and opportunities for intervenors to ask questions and submit written comments. When the public sees that the regulator is competent, independent, and responsive, confidence in the licensing outcome grows. Additionally, international peer reviews of the licensing process itself—such as the IAEA’s IRRS missions—can be conducted publicly, demonstrating a commitment to transparency that strengthens the social licence to operate. Some countries have also appointed an independent nuclear ombudsman to represent public interests in licensing proceedings.

Managing the Regulatory Interface Throughout Construction and Beyond

Licensing does not end with the construction permit. A CANDU project involves critical hold points during manufacturing of large components (e.g., calandria vessel, steam generators), civil works (reactor building basemat), commissioning, and eventually the transition to operations. The regulator must plan for these phases and resource them accordingly. A common model is to use a construction licence that specifies a schedule of inspections and tests, followed by an operating licence that is valid for a defined period and subject to periodic safety review. By integrating the experience of countries that have already licensed and built CANDU plants—such as South Korea’s experience with Wolsong units—emerging markets can anticipate resource needs and build in the flexibility to handle unforeseen technical issues. The IAEA’s Nuclear Power Plant Life Management framework provides guidance on the long‑term regulatory oversight that begins at the design stage. Early planning for decommissioning and waste management funding should also be part of the licence conditions, as these have financial implications that affect the project’s overall viability.

Looking Ahead: Building a Sustainable CANDU Licensing Pathway

The deployment of CANDU reactors in emerging markets is not merely a transactional export of technology; it is a long‑term partnership that strengthens the global nuclear safety and security regime. The licensing challenges described here—regulatory immaturity, technical unfamiliarity, political volatility, and resource constraints—are formidable but not insurmountable. Success depends on a patient, step‑by‑step approach that front‑loads infrastructure building, invests in human capital, and leverages the full suite of international support mechanisms. The IAEA, CNSC, WANO, and vendor organisations together offer a safety net of guidance that can be customised to local conditions. As more countries in Africa, Southeast Asia, and the Middle East seriously consider nuclear power to meet their clean energy objectives while maintaining grid reliability, the experience gained from existing CANDU licensing will prove invaluable. A well‑executed licensing process not only protects people and the environment but also lays the foundation for a domestic nuclear industry that can thrive for generations.

By aligning national legislation with internationally recognised safety principles, investing early in regulatory competence, and fostering transparency, emerging markets can turn the CANDU’s distinctive capabilities into a reliable source of low‑carbon electricity. The road is long, but the tools, knowledge, and political will are increasingly available to make it a reality. Additional information on the Canadian regulatory framework for CANDU can be found at the Canadian Nuclear Safety Commission’s CANDU reactor page, which details the specific licensing requirements applicable in Canada and which often serve as a reference for exporting nations.