Lingen

The Lingen site fabricates fuel assemblies for pressurized water reactors (PWR) and boiling water reactors (BWR). Besides fuel manufacturing, Lingen also supplies depleted uranium dioxide (UO2) powder and Gadolinium (Gd) rods to all European AREVA Group activities. The plant is the only AREVA facility in Europe that is equipped and licensed to receive and ship all intermediate nuclear fuel assembly products (i.e. UO2 powder, ENU and ERU pellets and fuel rods).

The Lingen site owns—and specializes in—technologies, equipment and processes essential to the fabrication of nuclear fuel, including fuel rod upset shape welders (USW), Automated Pellet Inspection System (APIS), and BTU sinter furnace technology.

The site supplies USW and APIS to other AREVA fuel manufacturing plants and to end-customers. Furthermore, the site has the capacity to accommodate special orders, such as disassembling fresh fuel elements for uranium recovery or for reassembly and use at a different nuclear power plant.

The Lingen plant holds an unlimited license, and specializes in the fabrication of fuel assembly components: conversion, pellet production, fuel rod production, and fuel assembly.

Main stages of the fabrication process

1. Conversion

The raw material, enriched uranium hexafluoride (UF6), is shipped from an enrichment facility and delivered in a solid state inside steel cylinders. As a prerequisite for further steps, UF6 is converted into uranium dioxide (UO2) powder, using a dry conversion process designed and patented by AREVA that does not produce any uranium-containing process waste or emissions—making it significantly more environmentally-friendly. The cylinder is heated to sublimate the UF6 before being made to react with water vapor and hydrogen to form UO2 powder. A by-product of this transformation, gaseous hydrogen fluoride, is discharged and cooled down together with excess water vapor. The hydrogen and water vapor condense to form hydrofluoric acid 40%, which is sold as reusable material with industrial applications.

º2. Pellet production 

The pellet production stage involves processing UO2 powder into uranium pellets—a process known as pelletizing. The powder is ground, compacted and grained to give it fluid characteristics, while lubricants and pore-former agents ensure the pellets can be pressed. This pre-treated UO2 powder is pelletized in rotary presses, into “greenlings,” which are then sintered in an oven for two to three hours at a temperature of 1,780°C to increase their density and strength. Afterwards, the pellets undergo a high precision grinding process to reach their target diameter. A fully automated laser-optical measurement system finally checks all pellets for dimensional accuracy.

3. Fuel rod production 

In the following stage, pellets are stacked in fuel columns and inserted into zirconium alloy cladding tubes, which are welded on one side using vibration technology or a force-monitored slide-in unit. The cladding tube is then furnished with a compression spring, evacuated to a welding chamber, flooded with helium and welded under pressure. Welded on both sides, the fuel rod ensures that no radioactive material leaks during reactor irradiation at a later stage. The completed fuel rod is subjected to several tests, including enrichment analysis of the contained pellets, helium-leakage tests as well as visual inspection.

4. Assembly 

The fabrication of a fuel assembly for pressurized water reactors (PWR) begins by welding spacers and a control rod guide tube to a mechanically stable supporting structure. Fuel rods are then fully inserted inside–following a predetermined loading plan—and sealed off with the head and foot pieces. Finally, the fuel assembly is cleaned, subjected to comprehensive final tests and stored in a suspended state in subsurface fuel assembly storage until dispatch. Ready-to-mount support structures are used in the fabrication of fuel assemblies for boiling water reactors.

Products manufactured at Lingen site

  • BWR fuel: ATRIUM 11, ATRIUM 10
  • PWR fuel: Focus, HTP, GAIA
  • Gadolinium pellets
  • Cr-doped pellets
  • MELOX powder
  • Disassembly of fuel elements
  • Technology transfers (equipment & services)