Rough neutron fields and nuclear reactor noise

Area of Science:

• Nuclear Engineering
• Statistical Physics
• Complex Systems

Background:

• Nuclear reactor cores rely on a critical state for sustained fission chain reactions.
• Neutron fields exhibit noise, causing fluctuations at smaller scales, especially during low power or due to perturbations.
• Unexplained power noise increases have led to reactor shutdowns.

Purpose of the Study:

• To model the effects of neutron power noise in nuclear reactors using statistical field theory.
• To investigate the connection between neutron field evolution and surface growth dynamics.
• To identify a noise amplitude threshold for a new criticality state and characterize the resulting phase transition.

Main Methods:

• Application of statistical field theory of critical processes.
• Modeling neutron field evolution using the Kardar-Parisi-Zhang equation.
• Utilizing renormalization-group approaches for numerical calculations.

Main Results:

• Established a link between neutron field dynamics and surface growth models.
• Calculated a threshold for reactor noise amplitude leading to a new criticality state.
• Estimated critical exponents for the phase transition to rough neutron fields.

Conclusions:

• The developed nonlinear noise model provides insights into reactor instabilities.
• The findings offer qualitative and quantitative understanding of previously misunderstood reactor noise phenomena.
• This work bridges statistical mechanics and reactor physics for improved safety and operational insights.