Silex invented and developed the ‘SILEX’ laser isotope separation technology in Sydney during the 1990’s. The uranium enrichment application of the SILEX technology was licensed exclusively in 2006 to Global Laser Enrichment LLC (‘GLE’), a joint venture business today owned by Silex (51%) and Cameco (49%). Silex and GLE jointly continue to commercialise the technology for potential deployment in the US with the aim of completing a full-scale pilot demonstration by the mid-2020’s.

The first planned commercial plant could involve a tails (depleted UF6) enrichment facility in Paducah, Kentucky, capable of producing up to 2,000 tonnes of natural UF6 (approximately 5 million pounds U3O8 equivalent) per year for approximately 30 years, which would rank in the top ten of current uranium mines by production volume. The Paducah plant has a target commercial operation date in the late 2020’s.  However, GLE’s owners are currently assessing the feasibility of accelerating this timeline in light of emerging geopolitical risks in the nuclear fuel supply chain, precipitated by Russia’s invasion of Ukraine. Furthermore, these emergent risks may potentially result in multiple target markets for the SILEX technology in the global nuclear fuel industry including for natural and enriched uranium, worth several billions of dollars annually (see Nuclear Fuel Production Opportunities).


The SILEX technology was invented by Silex Systems scientists Dr Michael Goldsworthy and Dr Horst Struve in the 1990’s at Lucas Heights, Sydney. In order to facilitate the potential commercial deployment of the technology in the United States, an Agreement for Cooperation between the governments of the United States and Australia was signed in May 2000. In June 2001, the technology was officially Classified by the United States and Australian governments, bringing the SILEX technology commercialisation project formally under the strict nuclear safeguards, security and regulatory protocols of each country.

From 2006 until 2020 the technology commercialisation project was managed by GLE as a subsidiary of GE-Hitachi Nuclear Energy (GEH) at its nuclear technology complex in Wilmington, North Carolina. In 2013, the project passed a major milestone with the successful demonstration of the technology at prototype scale in a Test Loop facility built by GLE – confirming the inherent efficiency of the laser-based SILEX technology. From 2014, GEH slowed the pace of development in response to the depressed nuclear fuel markets in the aftermath of Fukushima.

In 2016, GLE signed a landmark agreement with the US Department of Energy for the purchase of over 200,000 metric tons of depleted uranium hexafluoride (UF6) being tails material stockpiled from previous decades of enrichment operations at the DOE’s gaseous diffusion facility in Paducah, which was shut down in 2013. This material will be the feedstock for GLE’s Paducah Laser Enrichment Facility (PLEF) planned to be operational in the late 2020’s, or possibly earlier should market conditions and other factors support acceleration – which is currently being considered by GLE’s owners.

In December 2019, Silex announced the signing of a binding Purchase Agreement between Silex, Cameco Corporation (Cameco) and GEH for the purchase of GEH’s 76% interest in GLE. Following receipt of US Government approvals, this agreement closed in January 2021, resulting in Silex acquiring a 51% majority interest in GLE, and Cameco increasing its interest from 24% to 49%.

Uranium Enrichment

Naturally occurring uranium is dominated by two isotopes, U235 and U238. Nuclear energy is produced by the splitting (or ‘fission’) of the U235 atoms. Natural uranium is made up of ~0.7% of the ‘active’ U235 isotope with the balance (~99.3%) made up of the U238 isotope. Uranium enrichment is the process of concentrating or enriching the U235 isotope up to 5% for use as fuel in a conventional nuclear power reactor and up to 20% for emerging advanced Small Modular Reactors (SMRs). Enrichment is a technically difficult process and accounts for around 30% of the cost of nuclear fuel and approximately 5% of the total cost of the electricity generated by nuclear power.

The Separation of Isotopes by Laser EXcitation (SILEX) process is the only third-generation enrichment technology at an advanced stage of commercialisation today. It is able to effectively enrich uranium through highly selective laser excitation of the fluorinated form of uranium – the 235UF6 isotopic molecule.

The two methods of uranium enrichment used to date are the now obsolete Gas Diffusion technique (first generation) and Gas Centrifuge (second generation). Silex’s third-generation laser-based process provides much higher enrichment process efficiency compared to these earlier methods, potentially offering significantly lower overall costs.

Nuclear Fuel Production Opportunities

The first planned commercial project is the Paducah tails enrichment project, which is underpinned by a 2016 agreement between GLE and the US Department of Energy (DOE). Under the agreement, over 200,000 metric tons of depleted UF(DUF6 or tails) will be enriched with the SILEX technology to produce natural grade UFat a rate equivalent to 5 million pounds of uranium oxide per year for approximately 30 years.

The evolving transition of the global energy industry to low-omissions technologies, including nuclear power, and several more recent issues creating risks to the nuclear fuel supply chain, have opened up additional opportunities for GLE and the SILEX technology.  In particular, Russia’s invasion of Ukraine in February 2022 threatens to create supply disruptions to the US and European nuclear fuel markets, because of the over-reliance on Russian-sourced nuclear fuel. This has created a ‘Triple Opportunity‘ for GLE, for production of three grades of nuclear fuel at the proposed Paducah Laser Enrichment Facility (PLEF):

  • Unat

    Natural Grade Uranium (Unat)

    via re-enrichment of DOE inventories of depleted tails through the Paducah commercial project to produce uranium at natural U235 assay of (~0.7%)

  • LEU / LEU+

    Low Enriched Uranium (LEU) / LEU+

    LEU is used in today’s conventional nuclear power reactors (includes U235 assays between 3% to 5%), and LEU+ to meet the higher enrichment demands for existing reactors (includes U235 assays up to 10%)


    High Assay LEU (HALEU)

    a customised fuel for next generation advanced Small Modular Reactors (SMRs) currently under development (includes U235 assays up to 19.9%)

Uranium production and enrichment are the two largest value drivers of the current nuclear fuel cycle, accounting for up to 70% of the value of a fuel bundle. Furthermore, as the tails feedstock for the PLEF plant is already in the form of UF6, the value of the second step for fuel production – conversion – is also captured by the Paducah project.

Key features of the SILEX Uranium Enrichment Technology

The SILEX technology is a unique laser-based process that has the potential to economically separate uranium isotopes (as well as commercially valuable isotopes of several other elements). It has a number of advantages over other uranium enrichment processes including:

  • Inherently higher efficiency and throughput resulting in lower enrichment costs;
  • Smaller environmental footprint than centrifuge and diffusion plants;
  • Greater flexibility in producing advanced fuels for advanced SMRs; and
  • Anticipated to have the lowest enrichment plant capital costs.