CYNOD: A Neutronics Code for Pebble Bed Modular Reactor Coupled Transient Analysis

Hiruta, Hikaru; Ougouag, Abderrafi M.; Gougar, Hans D.; Ortensi, Javier; Nigg, David W.; Davis, Cliff B.; Weaver, W.L.

doi:10.1115/htr2008-58255

Cited by 11 publications

(10 citation statements)

References 4 publications

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“…2 has not yet been performed. A 3-D MCNP calculation is planned in the near future, and the results will enable verification of the deterministic analyses performed in this study.…”

Section: Two and Three Dimensional Resultsmentioning

confidence: 99%

Results of a Neutronic Simulation of HTR-Proteus Core 4.2 using PEBBED and other INL Reactor Physics Tools: FY-09 Report

Gougar¹

2009

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The Idaho National Laboratory's deterministic neutronics analysis codes and methods were applied to the computation of the core multiplication factor of the HTR-Proteus pebble bed reactor critical facility. A combination of unit cell calculations (COMBINE-PEBDAN), 1-D discrete ordinates transport (SCAMP), and nodal diffusion calculations (PEBBED) were employed to yield k eff and flux profiles. Preliminary results indicate that these tools, as currently configured and used, do not yield satisfactory estimates of k eff . If control rods are not modeled, these methods can deliver much better agreement with experimental core eigenvalues, which suggests that development efforts should focus on modeling control rod and other absorber regions. Under some assumptions and in 1-D subcore analyses, diffusion theory agrees well with transport. This suggests that developments in specific areas can produce a viable core simulation approach.

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“…2 has not yet been performed. A 3-D MCNP calculation is planned in the near future, and the results will enable verification of the deterministic analyses performed in this study.…”

Section: Two and Three Dimensional Resultsmentioning

confidence: 99%

Results of a Neutronic Simulation of HTR-Proteus Core 4.2 using PEBBED and other INL Reactor Physics Tools: FY-09 Report

Gougar¹

2009

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“…2 has not yet been performed. A 3-D MCNP calculation is being concluded by INL, but for the other Proteus cores which featured pebbles loaded in a crystalline lattice.…”

Section: Comparison Of Flux Profiles As Computed By Pebbed and Combinmentioning

confidence: 99%

“…CYNOD was recently incorporated into the RELAP5 systems analysis code to enable modeling of plantwide phenomena in PBRs. 2 Neutronic verification of PEBBED has thus far been limited to tests of the standalone diffusion and depletion solvers. The diffusion solver has been verified against solutions to simple core problems for which analytic solutions were computed.…”

Section: Introductionmentioning

confidence: 99%

Results of the Simulation of the HTR-Proteus Core 4.2 Using PEBBED-COMBINE: FY10 Report

Gougar¹

2010

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Deterministic neutronics analysis codes and methods established at Idaho National Laboratory were applied in computing the core multiplication factor of the high temperature reactor-Proteus pebble bed reactor critical facility. These same calculations were performed previously using earlier versions of the codes with less developed methods. The results of that earlier study (reported in INL/EXT-09-16620) indicated that the cross sections generated using COMBINE-7.0 did not yield satisfactory estimates of k eff , concluding that the modeling of control rods was not satisfactory. Over the past year, improvements to the homogenization capability in COMBINE have enabled the explicit modeling of tri-isotropic particles, pebbles, and heterogeneous core zones, including control rod regions, using a new multiscale version of COMBINE in which the one-dimensional discrete ordinate transport code ANISN has been integrated. The new COMBINE is shown to yield benchmark quality results for pebble unit cell models, the first step in preparing few-group diffusion parameters for core simulations. Presented in this report are results of this modeling effort where the full critical core is modeled, but with cross sections generated using the capabilities and physics of the improved COMBINE code. The new PEBBED-COMBINE model enables the exact modeling of the pebbles and control rod region along with better approximation to structures in the reflector. Initial results for the core multiplication factor indicate significant improvement in the Idaho National Laboratory's tools for modeling the neutronic properties of a pebble bed reactor. Errors on the order of 1.6 to 2.5% in k eff are obtained; a significant improvement over the 5 to 6% error generated by previous versions of the code. This is acceptable for a code system and model in the early stages of development, although too high for a production code. Analysis of a simpler core model indicates an over-prediction of the flux in the low end of the thermal spectrum. Reasons for this discrepancy are under investigation. Since new homogenization techniques and assumptions were used in this analysis, further confirmation and validation are required. Further refinement and review of the complex Proteus core model are likely to reduce the errors even further. vii viii

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“…The current Idaho National Laboratory (INL) coupled neutronics-thermal-hydraulics code CYNOD-THERMIX-KONVEK (Hiruta 2008) includes a shell model that approximates the temperature of the fuel region. Figure 2a includes an illustration for pebble bed fuel.…”

Section: Deficiencies Of Current Fuel Modelsmentioning

confidence: 99%

“…CYNOD (Hiruta 2008) is a semi-analytical nodal diffusion code based on a Green's function method with an implicit time-dependent scheme. CYNOD is coupled to the thermalhydraulics code THERMIX-KONVEK (Teuchert 1994), a two-dimensional (R-Z) quasi-static code developed by the KFA-Jülich, which contains correlations and material properties developed in the German PBR program.…”

Section: Integration Into the Coupled Neutronic-th Systemmentioning

confidence: 99%

Status Report on the Modeling of TRISO Energy Deposition, Time-Dependent Temperature Field and Doppler Feedback

Ortensi¹,

Ougouag²

2009

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The Doppler feedback mechanism is a major contributor to the passive safety of gas-cooled, graphite-moderated high-temperature reactors that use fuel-based Tristructural-Isotropic (TRISO) coated particles. It follows that the correct prediction of the magnitude and time dependence of this feedback effect is essential to the conduct of safety analyses for these reactors. We present a fuel conduction model for obtaining better estimates of the temperature feedback during moderate and fast transients. The fuel model has been incorporated in the CYNOD-THERMIX-KONVEK suite of coupled codes as a single TRISO particle within each calculation cell. The heat generation rate is scaled down from the neutronic solution and a Dirichlet boundary condition is imposed as the bulk graphite temperature from the thermal-hydraulic solution. This simplified approach yields similar results to those obtained with more complex methods, requiring multi-TRISO calculations within one control volume, but with much less computational effort. An analysis of the hypothetical total control ejection event in the pebble bed modular reactor (PBMR)-400 design that clearly depicts improvement in fuel temperature predictions is provided. vii viii ACKNOWLEDGEMENTS

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CYNOD: A Neutronics Code for Pebble Bed Modular Reactor Coupled Transient Analysis

Cited by 11 publications

References 4 publications

Results of a Neutronic Simulation of HTR-Proteus Core 4.2 using PEBBED and other INL Reactor Physics Tools: FY-09 Report

Results of a Neutronic Simulation of HTR-Proteus Core 4.2 using PEBBED and other INL Reactor Physics Tools: FY-09 Report

Results of the Simulation of the HTR-Proteus Core 4.2 Using PEBBED-COMBINE: FY10 Report

Status Report on the Modeling of TRISO Energy Deposition, Time-Dependent Temperature Field and Doppler Feedback

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