Ali Siddiqui, acting head of the Directorate, Advanced Reactors at Canadian Nuclear Laboratories spoke to Nuclear Engineering International about work to develop fuel for advanced reactors


CNL is supporting, enabling, and accelerating SMR deployments. (Credit: Markus Distelrath from Pixabay)

As Canada’s national nuclear laboratory, Canadian Nuclear Laboratories (CNL) is directly connected to developing advanced reactor and fuel technologies. CNL is supporting, enabling, and accelerating small modular reactor (SMR) deployments by developing underlying capabilities to enable SMR fuel prototyping and qualification.

CNL is currently working with Ultra Safe Nuclear Corporation (USNC) to develop the manufacturing process for its Fully Ceramic Microencapsulated fuel pellets, a tristructural-Isotropic (TRISO) type fuel that is used in high-temperature gas-cooled reactors. Funded through the Canadian Nuclear Research Initiative (CNRI), the project represented the first time that a TRISO-based fuel has been manufactured in Canada. CNL is working to develop its capabilities in molten salt synthesis and is working with molten salt technology developers to assist them in producing the scientific data to support their regulatory decision making and enable their success. CNL is also developing and applying additive manufacturing techniques to manufacturing of nuclear fuel materials. AM allows better control of the geometry of the manufacturing process, which benefits fuel performance and safety.

Can you tell us more about your work on TRISO fuel?

The past year was very exciting. Earlier in spring 2021 we completed the first series of development projects for USNC on their Fully Ceramic Microencapsulated fuel concept. This is a proprietary concept from USNC. It uses TRISO particles within a silicon carbide matrix material for the pellets. CNL is working closely with USNC to develop that concept further, including qualified procedures for fuel fabrication and characterisation of the end-product. That work is continuing and is first of a kind in Canada to produce TRISO-based fuel at CNL. We hope it is the beginning of much more work in that area.

What work is CNL doing on molten-salt fuels and what are the challenges?

CNL is developing a programme to increase our knowledge and skills and capabilities here. CNL is one of the facilities in the world that can handle a broad range of different materials, nuclear materials, special nuclear materials, and we’re developing capabilities as we speak here to synthesise and purify actinide-bearing fuel salts. This would be in a laboratory to prototype scale, so not large volumes for use in actual reactors, but to do the initial work upfront to measure thermophysical properties, study corrosion and thermal hydraulic behaviour of representative fuel salt. Some areas that we’re focusing on right now are developing the thermal physical property measurements to measure things like the thermal conductivity of molten salts across a broad regime of properties and temperatures. That is quite a bit different than measuring those properties for solid fuel materials. It’s a big development effort largely funded under our federal work, but we do anticipate these will all be required along with advanced modelling and simulation as these concepts move towards deployment.

When do you see deployment of an MSR?

I think I think it’s fair to say that molten salt reactors have a lot of promise being at near atmospheric pressure. You really do reduce the overall risk profile. You don’t have to have as many engineered safety systems in place, as you do with say, a water-cooled reactor. There are technical challenges and some hurdles to jump over the next few years. I think it’s safe to say that with a concerted effort in the…early 2030s, it’s very possible we’ll see Molten Salt Reactors deployed. Many of these vendors are looking for innovative approaches, and I think that must be taken into account…CNL and other labs around the world are certainly equipping ourselves to help answer technical questions and provide science based information to regulators and policymakers.

What are benefits of 3d printing for nuclear fuel?

3d printing is a technology that’s rapidly moving from being new to being something that’s well used in many industries… There have in the last year been several 3d printed reactor components that have gone in core in various stations. This is an exciting area of technology that promises reduced cost and faster turnaround time for replacement of certain components. But that said, the question is around fuel. Can this technology be applied to nuclear fuels? We’ve got a programme of work underway at CNL under our Federal Nuclear Science and Technology programme to look at the innovative approaches of using 3d printing technology to push the boundaries of what’s possible with printing of actual fuel material itself. This has not been done in many circles. Near term applications would be for instrumented fuel to allow voids within the fuel for mounting of sensors for in situ measurements during an irradiation programme, for example. But there are major questions that go a little bit beyond the technology of the fuel itself that are of interest to some of our stakeholders in the federal government. These include questions around safeguards and non-proliferation.

This article first appeared in Nuclear Engineering International magazine.