ALMAS 1.0

Thermal-Hydraulic Analysis of a Light water reactor core using Porous Media Approach in transient Situations

To address the challenges of thermo-hydraulic behavior and its secondary effects, accurate modeling of nuclear reactor cores in both steady-state and transient conditions is essential. For this purpose, the "ALMAS1.0" software was developed. It allows for the modeling of reactor cores with various configurations and arrangements of fuel assemblies, such as square and triangular patterns, under both single-phase and two-phase flow conditions, using a porous media approach. The two-phase flow model implemented in this software is based on drift-flux and homogeneous theories.

The software can handle transient calculations by simulating scenarios where power distribution changes, the inlet flow rate varies, the inlet flow temperature shifts, or outlet pressures fluctuate. Like many other tools it can process these variations simultaneously. Additionally, it offers flexibility in specifying the number of control volumes with either constant or varies mesh spacing, setting the times steps for simulations, and configuring the arrangement of fuel bundles (allowing each bundle to have between 0 to 6 neighboring bundles). Finally, the software can simulate the conditions where cross-flow between the bundles is present or not, account for channel blockage, and include the effects of fuel spacer grid (support) structure.

Software Features:

• Ability to model the core of nuclear reactors with square and triangular arrangements.
• Ability to model blockages in subchannels.
• Ability to simulate the core of LWRs under steady-states and transient conditions.
• Ability to simulate two-phase flow, including subcooled and saturated boiling, using drift-flux and homogeneous equilibrium models.
• Ability to define between 0 to 6 neighboring assemblies.
• Ability to define transient conditions for reactor power, inlet temperature, inlet fluid flow rate, and outlet (operating) pressure over time.
• Ability to simulate subchannels with varying porosities and hydraulic diameters.
• Ability to export outputs and results in excel and text files.
• Ability to create input files in text, graphical and wizard formats.