Completing the TMF23 October 2019
Construction of a new multi-million-pound tails management facility has been completed in Capenhurst, UK. Caroline Peachey reports.
URENCO GROUP’S CORE BUSINESS IS operating uranium enrichment plants at Gronau (Germany), Almelo (Netherlands), Capenhurst (UK) and Eunice (New Mexico, USA). Responsible management of tails, the byproduct of the enrichment process, is a crucial part of the company’s commitment to sustainability.
Depending on the availability of uranium supplies and the economics of the uranium market, tails may not be required to undergo re-enrichment for many years.
Instead, uranium hexafluoride (UF6) tails are converted to uranium oxide (U3O8), which is stable and allows longterm storage before either further enrichment or safe disposal of the residual uranium.
“There is a clear benefit in converting the hexafluoride to an oxide in terms of the stability of the material. It is also showing the stakeholders that we take management of nuclear material seriously,” says Laurent Odeh, who was recently appointed chief commercial officer of Urenco Group from August 2019. Odeh spoke to NEI in July when he was executive director of new business, a position he held since joining Urenco in February 2017.
Urenco’s Board took the strategic decision in 2009 to invest in a new Tails Management Facility (TMF) at its site in Capenhurst to reduce deconversion costs and reduce the group’s reliance on third-party services.
Construction work began in 2012, with operations initially expected to start by the end of 2015. However, construction was delayed, in part due to post-Fukushima safety-related upgrades, which were required well into the design phase.
Around 2300 people worked on the project during construction. In the end, construction took seven years and in June 2019 representatives from government, industry and the local community attended the official opening ceremony.
“We are happy to see the light at the end of the tunnel,” says Odeh. “We achieved more than seven million hours of safe working, making the TMF one of the safest construction sites in the UK.”
The TMF is operated by Urenco ChemPlants and will process depleted UF6 from Urenco’s European sites. It is scalable: it currently has two kilns with a nameplate capacity of 7000t/year, but more kilns could be built if market conditions warranted it.
The deconversion process
On arrival at the site, cylinders containing the depleted UF6 are loaded into autoclaves. There, electrically produced steam is used to convert the solid UF6 to a gas (see Figure 1).
The gaseous UF6 is fed into a kiln. Inside the kiln, deconversion of UF6 is achieved by reacting gaseous UF6 with steam to produce uranyl fluoride (UO2F2). The UO2F2 reacts further with steam and hydrogen to produce uranium oxide powder (U3O8) and hydrogen fluoride (HF). The U3O8 is packed into special containers for long term storage. The gaseous HF is cooled and liquefied for sale.
The uranium oxide storage facility is a radiologically shielded facility for long-term storage of U3O8 that has been processed and deconverted at the TMF. All material stored in the store is electronically tracked, in line with nuclear safeguards.
Cylinders must be tested and certified every five years. The TMF also includes a handling facility that can process and recertify cylinders. Before testing can be carried out, any residual uranic material must be removed. Once clean, the cylinders are internally pressure-tested using water, checked by an external inspector and then dried. Any new fittings are installed and tested; vacuum pressure is applied to the cylinder and then it is sealed and accurately weighed. The cylinder is then recertified for reuse in the enrichment process.
Any material containing uranic residue is received, treated and processed in a recovery facility, which separates recyclable uranic material suitable for storage and potential reuse. It includes pH adjustment/ precipitation, separation, drying or containment in drums. Water is also recovered for reuse in the TMF processes through evaporation, reverse osmosis and storage.
The TMF also includes a decontamination and maintenance facility, which will be used to decontaminate and maintain TMF plant items so that they can be re-used on the site or disposed of safely.
The current operating life of the suite is 25 years for the plant equipment, 30 years for the building and 100 years for the uranium oxide store. There is an expectation it will be relicensed.
Urenco says it is well into active commissioning of the Tails Management Facility.
“The uranium oxide store has been actively commissioned. We intend to bring cylinders on site for washing over the summer. The active reaction is expected to start in Q4,” says Odeh.
Active commissioning will be followed by a gradual ramp-up plan to reach nameplate capacity in 36 months.
Further expansion of the TMF will depend on market conditions and future requirements.
“The TMF is a dedicated plant for our own internal need, but we are also looking at the potential to use the capacity for other customers and have space for two further kilns in the future if required,” Odeh says.
The timescales for any such future expansion would be much shorter than for the build of the TMF. However, at the moment, Urenco has “enough capacity for the foreseeable future.”