Pellet Fuel Development Programme
STL has the capability and know-how to design a pellet fuel manufacturing production plant to produce UO2 fuel. The experience was gained at BEVA NECSA where firstly a Fuel Development laboratory was established and test were done to establish the technology and know-how to deconvert UF6 to produce UO2 powder and then to condition the powder to press green pellets. The pellets were then sintered under high temperature to produce high density UO2 pellets. After establishing the technology a pellet fuel fabrication facility was designed, procured, installed and commissioned. This plant after a qualification programme produced qualified fuel for the Koeberg nuclear reactor in South Africa. The plant was operated for 15 years and produced fuel to the same standard as the Reference Organization.
STL is also involved with the pellet production and irradiation programme in Norway with Thor Energy and the IFE. (Institute for Energy Technology) where pellets of different compositions including thorium are being produced for irradiation tests.
STL has acquired a 14% share in the Norwegian company Thor Energy who is a daughter company in the Scatec group of renewable energy enterprises based in Oslo, Norway. Among its portfolio of business activities, Scatec has major solar and wind energy interests - including mono-crystalline wafer production, solar PV plant system integration, and offshore wind power planning.
Thor energy is exploring the use of thorium in traditional LWR nuclear plants and has therefore started with an extensive fuel test program in which thorium fuel will be irradiated as part of the fuel qualification program.
Thorium fuels in the broadest sense can provide avenues to improve the credentials for nuclear energy by:
• Achieving more sustainable energy generation in which mined nuclear material is used more effectively. This draws on the possibility for high-conversion or even breeding of fissile 233U from thorium fuels in thermal reactors.
• Employing fuels that generate smaller problematic waste streams, and that can also transmute (destroy) actinide components in current-generation thermal reactor systems.
Thor Energy's technology development activities are undertaken with the vision that thorium-plutonium MOX analog fuels will be an attractive option for both light water reactor (LWR) operators and nuclear energy policy makers alike.
Thorium based fuels are being tested in the Halden Research Reactor in Norway with the aim of producing the data necessary for licensing of these fuels in the today's light water reactors (LWRs). The fuel types currently under irradiation are thorium oxide fuel with plutonium as the fissile component, and uranium fuel with thorium as an additive for enhancement of the thermo-mechanical and neutronic fuel properties. Fuel temperatures, rod pressures and dimensional changes are monitored on-line for quantification of thermo-mechanical behaviour and fission gas release. Preliminary irradiation results show benefits in terms of lower fuel temperatures, mainly caused by improved thermal conductivity of the thorium fuels. In parallel with the irradiation tests, a manufacturing procedure for thorium-plutonium mixed oxide fuel is being developed with the aim to manufacture industrially relevant high-quality fuel pellets for the next phase of the irradiation campaign.
The Seven-Thirty program started in late 2011 with experiment design and material procurement efforts. Burnup accumulation started with the loading of a first irradiation rig in April 2013, with the view of collecting high burnup data within five years. In parallel, the alpha laboratory at IFE Kjeller has been extended to enable manufacture of (Th,Pu)O2 material. Batches of experimental and reference fuel have been manufactured at the IFE Kjeller laboratory and loaded into the reactor together with (Th,Pu)O2 pellets procured from an earlier thorium fuel research program. The development of (Th,Pu)O2 fuel manufacture using powder metallurgical routes is underway at IFE Kjeller, so that more batches of pellets containing (Th,Pu)O2 and Uranium with thorium as an additive can be loaded in the Halden Research Reactor .
A major goal for the company is to initiate the trial irradiation of a candidate thorium-MOX fuel in an experiment to be conducted in the Halden test reactor. The intention is to build an international cost-sharing consortium by which to realize this major undertaking.