A homogeneous, mono-energetic, 1D-planar geometry system pulsed at a supercritical condition of $k=1.1$.

The simulation is run for 20 mean free times, during which the particle population grows by $\exp(2)=7.389$ times. A semi-analytical reference solution for neutron flux space-time distribution, $\phi(x,t)$, is available. The problem is based on the time-dependent analytical transport benchmark suite AZURV1¹.

A mono-energetic, 3D shielding system featuring a dog-leg vacuum channel surrounded by a shielding material.

The problem is based on an NEA steady-state fixed-source benchmark problem suite ². Time dependence is introduced by turning the fixed source source into a histogram pulse. Quantities of interest are the 4D flux distribution, $\phi(x,y,z,t)$, in a fine mesh of 60x100x60x100 and the total neutron density in time.

An infinite homogeneous system of 361 energy groups pulsed at a delayed supercritical condition.

The multigroup cross-section data is generated from a light-water reactor pin cell homogenization with OpenMC³ using the SHEM-361 energy group structure. A logarithmic time-mesh tally is used to observe both the prompt and delayed neutron flux responses. A semi-analytical reference solution for neutron flux energy-time distribution, $\phi_g(t)$, is available.

A pulsed infinite pin cell lattice.

The continuous-energy system is made subcritical by increasing the distance between fuel pins. A logarithmic time-mesh tally is used to observe both the prompt and delayed neutron flux responses. Quantities of interest are the flux energy spectrum evolution, $\phi(E,t)$, and the total neutron density in time.

A 3D 4x4 multigroup light water reactor assembly turned off-critical by maneuvers of control rod assemblies.

This is the fourth test problem of Exercise 4 of the C5G7-TD benchmark suite ⁴. Solving the problem consists of three parts:

1. Running static k-eigenvalue calculation to obtain fission neutron particles and parameters needed for initial condition generation, and
2. Running the initial condition generation based on the parameters and fission neutrons obtained in the previous part.
3. Running the time-dependent problem using the sampled initial source neutrons.

The first two parts are based on the methods described in ⁵

A nuclear reactor transient exercise exhibiting several key neutronics transient features. The transient is driven by time-dependent control rod positions and neutron source strengths.

• Phase 1: Start-up convergence of a source-driven subcritical configuration,
• Phase 2: Control rods withdrawal demonstrating the S-shape maneuver of power level,
• Phase 3: Power excursion from prompt supercriticality,
• Phase 4: Reactor shutdown emphasizing the delayed neutron effects. Stuck control rods are considered to promote spatial asymmetry in the flux distribution. Quantities of interest include evolutions of total power and axially segmented pin power, as well as thermal and fast fluxes.

The C5G7-TD model ⁴ going through the Four-Phase Transient.

A continuous-energy version of the C5G7-TD model ⁴ going through the Four-Phase Transient.

A multigroup NuScale-inspired small modular reactor model ⁶ going through the 4-phase transients.

A NuScale-inspired small modular reactor model ⁶ going through the 4-phase transients.

A depleted NuScale-inspired small modular reactor model ⁶ going through the 4-phase transients.

A fast neutron burst induced by strong reactivity pulses from a drop-through of a highly enriched uranium slug.

The problem attempts to simulate the Dragon machine experiment by Otto Frisch ⁷. At the heart of the problem is the reactivity excursion, giving nine orders of magnitude power increase in tens of milliseconds. A second reactivity pulse is introduced to emphasize the effect of the accumulating delayed neutron precursors.