Nuclear Fuel Development Cycle

Fuel Design

Reliable and safe operation of nuclear fuel depends on its proper design and manufacturing.

Modeling and Simulation

The Multiphysics Object-Oriented Simulation Environment, or MOOSE, is a computer simulation framework that simplifies the process for predicting the behavior of complex systems ranging from irradiation effects on materials to groundwater physics and chemistry.

Fabrication

Three main stages of most nuclear fuel fabrication:

1. Producing pure uranium dioxide (UO₂) from incoming UF₆ or UO₃.
2. Producing high-density, accurately shaped ceramic UO₂ pellets.
3. Producing the rigid metal framework for the fuel assembly – mainly from zirconium alloy; and loading the fuel pellets into the fuel rods, sealing them and assembling the rods into the final fuel assembly structure.

Steady State Irradiation

Nuclear fuel is loaded into the core, containing only uranium and other structural materials. As the fuel irradiates, the uranium absorbs neutrons (generally through fission) and produces other isotopes. As the core continues to operate Uranium-235 is burned out of the fuel, Plutonium is burned into the fuel, and residual fission products and other minor actinides buildup. Eventually the depletion of U-235 and buildup of other materials decreases the reactivity of the fuel to the point where the reactor can no longer maintain a critical condition. At that point, the core is shutdown and the used (or spent) fuel is discharged from the core and fresh fuel is reloaded to replace it.

Post-Irradiation Examination

Post-irradiation examinations (PIE) provide data on how newly developed or established materials withstand normal operating conditions in new environments. The investigation results provide information for fuel improvement and, thereby, can potentially enhance operating efficiency and reliability.

Transient Testing

Transient testing involves placing fuel or material into the core of a nuclear reactor and subjecting it to short bursts of intense, high-power radiation to simulate off-normal or accident scenarios.
The INL has a long history of using TREAT and other nuclear reactors for safe and successful performance of transient testing of nuclear power reactor fuels.

Post-Transient Examination

After the experiment is completed, the fuel or material is analyzed to determine the effects of the radiation. The resulting information is then used to guide the development and improvement of safer, advanced nuclear fuel designs.