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New Assessment of the Loft-Wyle Blowdown Test WSB03R Using Relap5-3D.

DE2005835069

Publication Date	2002
Personal Author	Bandini, B. R.; Aumiller, D. L.; Tomlinson, E. T.
Page Count	28
Abstract	The RELAP-3D (version bt03) computer program was used to assess the LOFT-Wyle blowdown test (WSB03R). The primary goal of this new assessment is to represent faithfully the experimental facility and instrumentation using the latest three-dimensional fluid flow modeling capability available in RELAP5-3D. In addition, since RELAP5-3D represents a relatively new and significant upgrade to the capabilities of the RELAP5 series of computer programs, this study serves to add to its growing assessment base. The LOFT-Wyle Transient Fluid Calibration test facility consisted of an approximately 5.4m3 pressure vessel with a flow skirt which created an annulus that acted as a downcomer. An instrumented blowdown loop with an orfice was connected to the downcomer. This facility, built to calibrate the orfices used in several of the LOFT experiments, simulated the LOFT reactor vessel and broken loop cold leg. For the present assessment an existing RELAP5 model developed at INEEL was corrected and upgraded. The model corrections included: (1) employing the proper measured downcomer thickness, (2) positioning the experimental instrumentation in its correct location, and (3) setting the fluid conditions to their measured initial values. Model upgrades included: (1) use of a more finely-detailed fluid component nodalization, (2) explicit modeling of the experimental facility beyond the blowdown orifice, (3) addition of heat structure components to represent the heat capacity of structural material, and (4) use of three-dimensional fluid components to model asymmetrical portions of the facility. The new assessment highlights the need to model explicitly the effects of heat storage in structural materials for slowly evolving transients. The assessment also highlights the sensitivity of choked-flow limited calculations to: (1) the model employed, (2) input discharge coefficient values and/or (3) input nonequilibrium values. In addition, the present assessment demonstrates that an instability in the calculated liquid fraction at the base of the downcomer obtained using the standard RELAP5-3D Kataoka-Ishii drift flux correlation can be substantially mitigated through the use of the optional Gardner correlation in the fully one-dimensional model. Finally, the new assessment demonstrates the correct functioning of the three-dimensional fluid components. For this particular transient, three dimensional modeling does not significantly alter or improve agreement with the experimental data in comparison with an equivalent model consisting entirely of one dimensional fluid components. This assessment shows that the Vea-Lahey drift-flux correlation in conjunction with the modified LeVeque momentum flux-splitting model is required to dampen liquid fraction oscillations at the vessel/downcomer interface in the 3-D model.
Keywords	Blowdown Loft reactor Heat storage Pressure vessels Building materials Calibration Simulation Computer codes Oscillations Sensitivity Thickness
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Bettis Atomic Power Lab., West Mifflin, PA.; Department of Energy, Washington, DC.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200524

New Assessment of the Loft-Wyle Blowdown Test WSB03R Using Relap5-3D.

New Assessment of the Loft-Wyle Blowdown Test WSB03R Using Relap5-3D.
DE2005835069

Publication Date	2002
Personal Author	Bandini, B. R.; Aumiller, D. L.; Tomlinson, E. T.
Page Count	28
Abstract	The RELAP-3D (version bt03) computer program was used to assess the LOFT-Wyle blowdown test (WSB03R). The primary goal of this new assessment is to represent faithfully the experimental facility and instrumentation using the latest three-dimensional fluid flow modeling capability available in RELAP5-3D. In addition, since RELAP5-3D represents a relatively new and significant upgrade to the capabilities of the RELAP5 series of computer programs, this study serves to add to its growing assessment base. The LOFT-Wyle Transient Fluid Calibration test facility consisted of an approximately 5.4m3 pressure vessel with a flow skirt which created an annulus that acted as a downcomer. An instrumented blowdown loop with an orfice was connected to the downcomer. This facility, built to calibrate the orfices used in several of the LOFT experiments, simulated the LOFT reactor vessel and broken loop cold leg. For the present assessment an existing RELAP5 model developed at INEEL was corrected and upgraded. The model corrections included: (1) employing the proper measured downcomer thickness, (2) positioning the experimental instrumentation in its correct location, and (3) setting the fluid conditions to their measured initial values. Model upgrades included: (1) use of a more finely-detailed fluid component nodalization, (2) explicit modeling of the experimental facility beyond the blowdown orifice, (3) addition of heat structure components to represent the heat capacity of structural material, and (4) use of three-dimensional fluid components to model asymmetrical portions of the facility. The new assessment highlights the need to model explicitly the effects of heat storage in structural materials for slowly evolving transients. The assessment also highlights the sensitivity of choked-flow limited calculations to: (1) the model employed, (2) input discharge coefficient values and/or (3) input nonequilibrium values. In addition, the present assessment demonstrates that an instability in the calculated liquid fraction at the base of the downcomer obtained using the standard RELAP5-3D Kataoka-Ishii drift flux correlation can be substantially mitigated through the use of the optional Gardner correlation in the fully one-dimensional model. Finally, the new assessment demonstrates the correct functioning of the three-dimensional fluid components. For this particular transient, three dimensional modeling does not significantly alter or improve agreement with the experimental data in comparison with an equivalent model consisting entirely of one dimensional fluid components. This assessment shows that the Vea-Lahey drift-flux correlation in conjunction with the modified LeVeque momentum flux-splitting model is required to dampen liquid fraction oscillations at the vessel/downcomer interface in the 3-D model.
Keywords	Blowdown Loft reactor Heat storage Pressure vessels Building materials Calibration Simulation Computer codes Oscillations Sensitivity Thickness
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Bettis Atomic Power Lab., West Mifflin, PA.; Department of Energy, Washington, DC.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200524