Advanced reactor and fuels transport

Above: HALEU ready for fuel fabrication (Photo: INL)

Radioactive materials play a vital role in many aspects of our everyday lives. They are used in medical diagnostic equipment and radiopharmaceuticals; as the key component in many smoke detectors; in the exploration for oil and natural gas; in industrial applications; to date archaeological artifacts; in research applications supporting a wide range of technologies; and in nuclear power plants to produce electricity. Safe and secure packaging and transport of these radioactive materials makes the use of these materials in all these applications possible.

Focusing on nuclear fuel cycle materials, the various transportation steps – from transport of uranium ore from mines to processing facilities, to transport of fabricated fresh fuel to nuclear power plants, and on to the transport of used nuclear fuel for storage or disposal – are all necessary steps in the production of electricity from nuclear energy. Today, there is a renewed focus on nuclear energy’s role in combating global climate change and an associated reduction in carbon emissions. Many countries are consequently embracing nuclear power for electricity production and as a means of bolstering national energy security. Reliable fuel supply will require a strong international supply chain from trusted companies. Included within that supply chain must be a robust system for packaging and transportation of all the materials found within the nuclear fuel cycle.

New reactors and new fuels

Existing and planned light-water reactors (LWR) utilise fuel with uranium enrichment levels of up to 5.0 weight-percent (wt%) in the Uranium-235 (235U) isotope. However, fuel suppliers are also developing advanced fuels which would utilize high-assay low-enriched uranium (HALEU). HALEU fuel has enrichments above 5.0 wt% and up to 20 wt% of 235U. Fuel with enrichment assays from 5.0 to 10.0 wt% are referred to as “LEU+” by some entities, reserving the term “HALEU” for enrichment assays of between 10.0 and 19.5 wt%. Commercial LWR operators and fuel fabricators are pursuing LEU+ fuel along with new accident tolerant fuel (ATF) designs, with plans to begin using LEU+ fuel in reload quantities in the mid- to late-2020s. Package designs for the transportation of fabricated LEU+ fuel have already been revised by fuel suppliers and a new package was recently approved for transport of uranium hexafluoride (UF6) which can support transport of enrichment assays up to 20 wt% 235U. U.S. regulators are also considering changes to U.S. transportation safety regulations to allow existing UF6 packages to transport LEU+ fuel.

The fuel for many Advanced Reactor (AR) designs requires enrichment assays above 10 wt% 235U. This includes, for example, the fuel required for high-temperature gas-cooled reactors (HTGR). The use of HALEU fuel will therefore require existing transport packages to be revised or completely new packages to be developed in order to transport HALEU fuel in its various forms. Packages for transport of AR TRi- structural ISOtropic (TRISO) particle fuel have been approved by regulators in the U.S. Amendments to existing transportation packages to allow them to transport HALEU feed material in metal form are also expected in the near term. However, fresh fuel assemblies for certain advanced reactors will likely require the development of new fresh fuel packages, possibly adapted from an existing package. Development and approval of transport packages for AR fuel will be an important step in the deployment of AR technologies around the world.

New concepts for the use of nuclear power are also under development, such as transportable nuclear modules (TNM), which would require the transportation of fully-fuelled reactor components as cargo for delivery at a destination; transportable nuclear power plants (TNPP), such as microreactors which would also require transport of fuelled nuclear power plants as cargo for delivery at a destination; nuclear electric propelled ships (NEPS), in which an integrated power plant would provide maritime propulsion; and floating nuclear power plants (NFPP), which would be transported to a destination for power production. Industry is working with the relevant competent authorities to determine whether there are gaps in the existing regulations as they relate to maritime transport, security and radioactive materials packaging, and which must be addressed in order to deploy these new concepts.

Author: Eileen M. Supko, Principal, Energy Resources International, Inc.