SIMULATE5

Advanced Solvers: Neutronics Built for Tomorrow

SIMULATE5 has been completely rewritten with a focus on first-principle physics, far exceeding the capabilities of existing methods:

• Generalization of the two-group diffusion model to full multi-group formulation
• Extension of the depletion model to microscopic depletion with more than 50 explicit nuclides
• Extensions of the axial heterogeneity model to treat explicitly each spacer gird, every material interface, and all control rod interfaces
• Improvement of the radial rehomogenization model to significantly improve modeling of bundle heterogeneities
• Improvement of the pin power reconstruction to treat detailed local pin isotopic as well as representation of intra-assembly flux shape in more detail

SIMULATE5 solves the multi-group diffusion or, optionally, the simplified P3 equations. Cross sections are described by a hybrid microscopic-macroscopic model that includes approximately 50 heavy nuclides and fission products (17 actinides, 30+ fission products and burnable absorbers). Heterogeneities in the axial direction of an assembly are treated explicitly. Radially, the assembly is divided into heterogeneous submeshes, thereby overcoming the shortcomings of spatially-averaged assembly cross-sections and discontinuity factors generated with zero net-current boundary condition.

In the improved pin power reconstruction module of SIMULATE5, the heterogeneous pin powers are calculated by modulating homogeneous multi-group pin powers from the submesh solver with pin form factors from single-assembly CASMO5 lattice physics calculations. The multi-group pin power module captures instantaneous spectral effects, the actinide tracking on the assembly submesh describes exposure-induced pin power variations.

Engineering Applications: Automated Calculations

SIMULATE5 is built on over 25 years of real-world engineering experience. Several new automated engineering features have been incorporated into the core product to accompany the long list of existing features:

• Fuel Management: Loading pattern validation, cycle length prediction, technical data book
• Core Follow and Operational Support: Automated reactivity coefficient calculations, rod worth calculations, and multi-criteria searches
• Fuel Integrity: Thermal limits (BWR), Power-dependent limits (PWR), PCI analysis, 3D shutdown margin calculations
• Control Rods: Rod depletion, fluence tracking, pattern searches, stuck rod analysis
• Special Projects: Steaming rate calculations, channel bow modeling, fixed-source calculations, power adaption

The SIMULATE5 input format is simple to use, allowing free-format input capable of modeling complex core layouts and includes automated functions to simplify tedious engineering calculations. With practical defaults for PWRs and BWRs, robust error checking, and seamless interfaces to other Studsvik core analysis tools, SIMULATE5 allows engineers to spend their time analyzing, not troubleshooting software.

Better Fuel Management: Validate and Verify Vendor Designs

The improvements in SIMULATE5’s calculation engine dramatically increase the accuracy of cycle eigenvalue behavior, cycle length predictions, cold critical eigenvalue, and startup predictions for heterogeneous cores and long cycle lengths. The microscopic depletion model improves history modeling for more efficient power maneuvering over long-length cycles.

SIMULATE5 has native support for inputting as-built enrichment and loading values, ensuring that the model is as close to what’s actually in the core as possible. Shutdown cooling and pin power reconstruction are now more accurate than ever before, making for better thermal margin calculations and more accurate isotopic inventories.

SIMULATE5 efficiently and accurately verifies core loading pattern designs even with complicated core designs containing:

• Reprocessed uranium and/or MOX
• Integrated burnable poisons (gadolinia, erbia, IFBA), removable poisons (WABA, Pyrex), and a combination of both
• In-core instrumentation for power monitoring, including 235U fission chambers, rhodium and platinum detectors, gamma and neutron TIPs, vandadium aeroballs, and gamma thermometers

SIMULATE5 maintains the proven, easy-to-use input/output formats of its predecessors - allowing users to model light water reactor cores loaded with fuel from any vendor consistently and accurately. Existing users will experience a seamless transition as SIMULATE5 was built to maintain compatibility with all derivative products (SIMULATE3-K/S3R).

Generalized Thermal-Hydraulics: New Models For BWRs and PWRs

SIMULATE-5 includes an all-new four-equation thermal-hydraulic engine that unifies BWR and PWR modeling inside the reactor core. In each axial node of a channel, the total mixture mass, steam mass, mixture enthalpy, and mixture momentum balance equations are solved and void fractions are determined by a drift flux model.

For pressurized water reactors, a unified model allows for voiding, with each assembly having an active channel and a number of parallel water channels. The PWR core treats assembly cross-flow by solving the axial and lateral momentum equations. Outside of the core, PWR thermal-hydraulics are calculated from the lower to upper tie plates.

For boiling water reactors, SIMULATE5 models the entire vessel loop: core, chimney (for natural circulation reactors), upper plenum, standpipes, steam separators, downcomer, re-circulation pumps, and lower plenum. The BWR assembly may be divided into four radial sub-channels, which communicate via cross-flow (or are closed for SVEA-type fuel). The cross flows are determined by solving lateral momentum equations.

SIMULATE5 also offers a DNBR evaluation.

All thermodynamic quantities in SIMULATE5 are now evaluated by using the modern NIST/ASME steam/water function library.