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Frequently Asked Questions

Last updated: February 22, 2023

We are currently actively engaging with the community to get feedback on our proposed plans and seek input.  We welcome your thoughts, so please continue to contact us with your feedback and questions at or using the feedback form.  Check back often as we will continue to post the frequently asked questions that we receive. 

The Proposed Subcritical Assembly Project

  • Why is Ontario Tech Pursuing This Project?

    The proposed subcritical assembly aligns with the University's key priorities, mainly: Tech with a Conscience

    The Canadian government acknowledges in the 2030 Emissions Reduction Plan that the investment in nuclear energy is crucial to achieving our net zero goals by 2050. A healthy nuclear energy sector is vital to securing Canada’s energy requirements for the future, and vital to economic development.   The subcritical assembly will support the nuclear energy sector as they deliver next-generation solutions to global challenges through:

    Enriching Research and Teaching Opportunities:

    A subcritical assembly will the only facility of its kind in Canada. It will provide a focal point for faculty and student nuclear energy research that can be leveraged to advance knowledge and develop new technologies to drive innovation which will power economic growth.   Further, the unique facility will support program recruitment efforts by attracting future students and grow the nuclear industry talent pool.    

    Expanding Experiential Learning Possibilities:

    Students will have the hands-on experience of operating a teaching reactor under supervision.  Because of a subcritical assembly's distinct design features, the proposed facility will be very accessible to students which enables early introduction to experience the safety culture and learn the technical expertise required in a Class 1A Nuclear Facility.  The proposed facility will further empower our career-ready graduates to thrive in the workforce.

    Engaging Partners within the community.  

    As Canada’s only undergraduate nuclear program, the proposed facility will be a one-of-a-kind asset that will enable expanded partnerships with nuclear energy sector organizations.  The facility will support both traditional reactor and small modular reactor (SMR) design.

    Importantly, the subcritical assembly provides a favourable environment for independent validation of data and nuclear designs for industry. For example, it will potentially allow industry to:

    • Test instrumentation before use on critical reactors.
    • Confirm reactor modelling and simulations.
    • Train personnel and upskill the existing workforce on nuclear technologies.
    • Assess automation of control systems in a nuclear environment.

    In addition to research, we envision the subcritical assembly to be a hub for community engagement to educate the public on nuclear energy and the vital role it plays in the clean energy economy in order to achieve Canada's sustainable development goal #7: affordable and clean energy.

  • What will the Proposed Subcritical Assembly be used for?
    The subcritical assembly will be used for research, teaching, training.  We will provide more details as we progress through planning.
  • Where Will The Proposed Subcritical Assembly Facility be Located?
    The proposed subcritical assembly will be built and operated in an existing laboratory in the Nuclear Facility Complex of the Energy Systems and Nuclear Science Research Centre (ERC), located on Ontario Tech University's North Campus in Oshawa, Ontario.
  • What is the Process for Allowing the Operation of the Proposed Subcritical Assembly?

    It is very early in the process and there are numerous steps required before the proposed plan could come into fruition.  Operating the subcritical assembly requires a licence from the Canadian Nuclear Safety Commission (CNSC), who are responsible for regulating the use of nuclear energy and materials to protect health, safety, security and the environment.

    We have informed the CNSC of our intent to apply for a license to operate the subcritical assembly, which is different from the two CNSC licences we already hold.  The subcritical assembly licence is for the operation of a Class 1A Nuclear Facility

    Obtaining a Class 1A Nuclear Facility licence is a comprehensive process - please visit the CNSC Licencing Process for more details.

    In parallel to the licencing process, proactive engagement and communications with Indigenous communities, the campus community, and members of the public will be ongoing, to share information and seek input on our plans.

  • Why Does the Licensing Process Take So Long?

    Canada is a tier-1 nuclear nation with a full spectrum of capabilities and resources in nuclear technology, and, as such, requires a robust regulatory framework. For Class 1 licencing, the Canadian Nuclear Safety Commission (CNSC) performs a comprehensive technical and environmental review of all license applications, which includes engagement with Indigenous and Public communities.  All of this takes time and underpins the importance of ensuring the protection of health, safety, security, and the environment of Canadians. 

    Much like going through the G1 -> G2 -> G driver's license process to show a driver is capable to responsibly operate a vehicle, we must show the CNSC we are capable of responsibly operating such a proposed facility. 

    Ontario Tech University understands the importance of the licensing process and we respect the timelines of the CNSC. 

  • How Can I Learn More About and Get Involved In the Proposed Project?
    We would love to hear from you!  We are currently actively engaging the campus, Indigenous, and public communities on our proposal to seek input and guidance.  For more details, please visit our learn more and get involved webpage.

About Subcritical Assemblies

  • What is a Subcritical Assembly?

    There are many classes of nuclear reactors, one of which is a subcritical assembly.  In Canada, the Canadian Nuclear Safety Commission uses the term “subcritical nuclear assembly”, however, in other areas of the world a subcritical assembly can also be referred to as a subcritical reactor. 

    Most people are familiar with large, traditional nuclear reactors that generate electricity – like those operated in Ontario by Bruce Power and Ontario Power Generation. Subcritical assemblies are about as far on the other end of the spectrum as you can get from that, and yet still be classified as a reactor.  The table shows the difference in power output of some of the various reactors types in Canada: 

    Types of Reactors In Canada. OPG and Bruce CANDU Power Reactors are on the high end of the spectrum at over 600 MW.  Towards the opposite end of the spectrum we have the Research Reactors at McMaster, Ecole Polytechnique, Royal Military College, and Canadian Nuclear Laboratories.  These range from 5 megawatts to 0.0001 megawatts.  The proposed subcritical assembly is on the low end at 0 megawatts of power.

    All reactors are based on the same principles of nuclear science, where fission takes place within the reactor core:  neutrons split atoms, releasing more neutrons, and so on, creating a chain reaction.

    The difference is that a power generating reactor is CRITICAL: it can sustain a chain reaction.  A subcritical assembly is SUBCRITICAL: it cannot sustain a chain reaction and stops operating unless neutrons are proactively added from an external source.  To understand more about nuclear fission and chain reactions, please see the What is Nuclear Fission FAQ.   

    Because of the inherent design features, a subcritical assembly serves as a valuable tool for research, teaching, and training.  This is why it is often referred to as a "teaching reactor".

  • How Does a Subcritical Assembly Work?

    Subcritical assemblies come in many different shapes and sizes but in all designs, there is nuclear fuel, a structural moderator core, and a neutron source.

    In order to operate and “switch on” a subcritical assembly, a neutron source is inserted into the core.  The subcritical assembly “amplifies” the neutrons to a steady state BUT it is still subcritical.  It MUST have the neutron source inserted in order to keep the chain reaction going.  When the neutron source is taken away, the chain reaction stops: the subcritical assembly ceases operation and is considered “switched off”.

    For more details on how nuclear fission works in a subcritical assembly, please visit the What is Nuclear Fission FAQ.

  • What is Nuclear Fission?
    Please see what is nuclear fission? for more information.
  • What Makes a Subcritical Assembly Unique?

    A subcritical assembly is unique due to it's very simplistic inherent design.  A subcritical assembly:

    • does not generate any power to produce electricity
    • does not produce significant heat that needs to be cooled or controlled
    • does not require an extensive start up or shutdown process - the neutron source is simply inserted and removed to "turn on" and "turn off" the system
    • does not need pressurized systems

    These inherent design features makes a subcritical assembly very conducive for research, teaching, and training.

     Reference: Considerations of Safety and Utilization of Subcritical Assemblies, IAEA 

  • What is The Typical Size of a Subcritical Assembly?

    Subcritical assemblies come in many different shapes and sizes but in all designs, there is nuclear fuel, a core structure, and a neutron source.  To see examples of subcritical assemblies around the world, please visit the research reactor database of the International Atomic Energy Association

    Our proposed subcritical assembly will be able to fit inside an existing laboratory.  The design is still being finalized as we are still in the early stages of the process.  We will share a finalized design once we progress further in the process.

  • Where Else in The World do Subcritical Assemblies Exist?

    The Research Reactor Database of the International Atomic Energy Agency provides a list of all the research reactors in the world.  A search shows subcritical assemblies operating in countries such as the USA, Philippines, Jordan, Czech Republic, among others.   

Questions From the Community

  • Is The Proposed Subcritical Assembly Safe?

    Yes, the proposed subcritical assembly is safe for all members of our campus community, the public in the surrounding community, and the environment.

    A subcritical assembly with its inherently distinct design features makes it a very conducive tool for research, teaching, and training.  No adverse effects on the community and the environment are anticipated based on operating experience from similar subcritical assemblies currently operating around the world. Our detailed analysis will confirm this and will be documented in the licence application.  Our analysis will be available for the public and will be reviewed by technical experts at the CNSC.

    In addition, we will also incorporate additional safety barriers and enhancements into the design and operating procedures to add even more protection for people and the environment.

    The CNSC’s comprehensive process ensures that no licence is issued to an applicant until the Commission is satisfied that all aspects of health, safety and environmental protection are met.

  • Is the Proposed Subcritical Assembly Already on Campus?

    No, there is no subcritical assembly on-site. We are still in the design and pre-licensing stage with many steps ahead.  If successful, this will be the first subcritical assembly on campus.  

    We have individual components of a subcritical assembly on-campus - some components are securely and safety stored, while other components are regularly used for research and teaching under our current CNSC licenses.  This is similar to having individual lego bricks - all the pieces must be used together to build the final design.  

    We are not authorized to assemble, configure and/or operate the individual components into a subcritical assembly until the CNSC grants approval and issues the appropriate operating licence.  

  • Is There Enough Space On Campus to Build or Install The Proposed Subcritical Assembly?
    Yes.  The proposed facility will be located in the Nuclear Facility Complex, within an existing laboratory that is purpose-built for nuclear work.
  • Are There Other Nuclear Activities Currently Taking Place On Campus?

    We are proud to offer the only Nuclear Engineering undergrad degree program in Canada, as well as various other undergraduate, masters’ and doctoral programs in health physics, radiation and nuclear science, and nuclear engineering - all of which include opportunities for students to gain hands-on experience working in our high-tech nuclear laboratories.

    We currently hold two licences granted by the Canadian Nuclear Safety Commission (CNSC) which governs the materials and equipment currently in use for education and research purposes - for example: radioisotopes, nuclear gauges, and irradiators. The licences were granted following a comprehensive review and approval process by the CNSC.  Our Nuclear Substances and Radiation Devices licence was granted in 2003 and our Class II Nuclear Facility licence for our neutron generator was granted in 2012.  We have successfully renewed our licenses every 5 years, with the CNSC performing a comprehensive technical review of our radiation safety program each time. 

    We have consistently demonstrated our ability to successfully manage the equipment and materials currently on-site, meeting and surpassing all CNSC license requirements.  Our 20-years of experience working safely with nuclear substances and radioactive devices demonstrates our ongoing commitment to the protection of our campus, the community, and the environment.

  • How Will the Nuclear Waste be Handled? Will Nuclear Waste be Produced?

    A subcritical assembly produces minimal to no nuclear waste due to its inherent design features, however, we are still very early in the planning stages and will have a more definitive answer once a design is finalized.  As part of licensing, an environmental review and preliminary decommissioning plan assessment of our final design will be performed by technical experts at the CNSC.