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Particle confinement criteria for velocity space particle loss are used to calculate the radial and axial electric potential profiles in field-reversed configurations (FRC’s). Assuming Vlasov equilibrium distribution functions for both electrons and ions, the density profile and the potential profile are calculated self-consistently. With rest Maxwellian distribution functions for both species and the Hill’s vortex magnetic configuration, a radial electric field of about 0–70 V/cm and an axial electric field of about 0–4 V/cm, depending on positions, have been found for a typical set of experimental parameters: electron temperature Te=100 eV, ion temperature Ti=200 eV, magnetic field B0=5500 G, separatrix radius rs=12 cm, and elongation factor k=5. The corresponding density profile has behavior similar to profiles observed in the experiments. Cases using rigid-rotor distribution functions with different rigid rotating frequencies are also studied. [ABSTRACT FROM AUTHOR]

• NRC has demonstrated a method to estimate fuel dispersal during accidents in PWRs with high burnup/enrichment fuel. • The method involves loose coupling among neutronics, fuel performance, and systems analysis codes. • This exercise has identified several areas for improvement in all facts of the analysis, including validation. • This is only a demonstration of our code capabilities using a hypothetical core design. Recent experimental findings indicate that under certain transient conditions, high-burnup fuel operating at sufficiently high power can fragment and escape from burst fuel cladding, as discussed in the Nuclear Regulatory Commission's Research Information Letter (RIL) 2021–13. The escaped fuel fragments could subsequently be distributed throughout a reactor coolant system (RCS), potentially challenging core coolability during a loss of coolant accident (LOCA). Consequently, the NRC has developed a methodology to estimate the mass of fuel that could be dispersed during a large-break LOCA. The methodology involves several NRC-sponsored computer codes, including SCALE/Polaris for lattice physics, PARCS/PATHS for full-core neutronics, TRACE for core and RCS thermal hydraulics, and FAST for steady-state and transient fuel performance calculations. Output from FAST is combined with the models in RIL 2021–13 to estimate fuel dispersal to the coolant. NRC staff have exercised this methodology using a prospective Westinghouse four loop core design with high burnup and extended enrichment that was obtained from the Department of Energy's NEAMS program. Results demonstrate that the NRC methodology can be exercised to provide fuel dispersal estimates that can subsequently be used to study the potential consequences of FFRD. However, this exercise has also identified several areas for improvements to both the codes and to the modeling approaches used here, including the pin power reconstruction methods in PARCS, the modeling approach used to connect the Cartesian and cylindrical vessel components in TRACE, transient fission gas release and fuel rod upper plenum models in FAST, and tighter coupling between FAST and TRACE. [ABSTRACT FROM AUTHOR]

Highlights: [•] Study and implement high-resolution numerical methods for two-phase flow. [•] They can achieve better numerical accuracy than the 1st-order upwind scheme. [•] They are of great numerical robustness and efficiency. [•] Great application for BWR stability analysis and boron injection. [Copyright &y& Elsevier]