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Brear, D. J.*; Kondo, Satoru; Sogabe, Joji; Tobita, Yoshiharu*; Kamiyama, Kenji
JAEA-Research 2024-009, 134 Pages, 2024/10
JAEA-Research-2024-009.pdf:2.45MB
The SIMMER-III/SIMMER-IV computer codes are being used for liquid-metal fast reactor (LMFR) core disruptive accident (CDA) analysis. The sequence of events predicted in a CDA is often influenced by the heat exchanges between LMFR materials, which are controlled by heat transfer coefficients (HTCs) in the respective materials. The mass transfer processes of melting and freezing, and vaporization and condensation are also controlled by HTCs. The complexities in determining HTCs in a multi-component and multi-phase system are the number of HTCs to be defined at binary contact areas of a fluid with other fluids and structure surfaces, and the modes of heat transfer taking into account different flow topologies representing flow regimes with and without structure. As a result, dozens of HTCs are evaluated in each mesh cell for the heat and mass transfer calculations. This report describes the role of HTCs in SIMMER-III/SIMMER-IV, the heat transfer correlations implemented and the calculation of HTCs in all topologies in multi-component, multi-phase flows. A complete description of the physical basis of HTCs and available experimental correlations is contained in Appendices to this report. The major achievement of the code assessment program conducted in parallel with code development is summarized with respect to HTC modeling to demonstrate that the coding is reliable and that the model is applicable to various multi-phase problems with and without reactor materials.
Kamiyama, Kenji; Brear, D. J.*; Tobita, Yoshiharu; Kondo, Satoru
Journal of Nuclear Science and Technology, 43(10), p.1206 - 1217, 2006/10
Times Cited Count：28 Percentile：84.44(Nuclear Science & Technology)A mechanistic simulation of molten core-material relocation is required to reasonably assess consequences of postulated core disruptive accidents (CDAs) in fast reactors (FRs). The dynamics of molten core-material freezing when it is driven into the channels surrounding the core region plays an important role since this affects fuel removal from the core region. Therefore, a mechanistic model for freezing behavior was developed and introduced into the FR safety analysis code, SIMMER-III, in this study. Based on the micro-physics of crystallization, two key assumptions, supercooling of melt in the vicinity of the wall and melt-wall contact resistance due to imperfect contact, were introduced. As a result, encouraging agreement both with measured melt-penetration lengths and freezing modes of UO
and metals was obtained. Furthermore, in order to reinforce the developed model, a semi-empirical correlation to predict the supercooling temperature was found. The developed model with the new correlation reproduced both stainless steel freezing and alumina freezing.
Yamano, Hidemasa; Fujita, Satoshi; Tobita, Yoshiharu; Kamiyama, Kenji; Kondo, Satoru; Morita, Koji*; Fischer, E. A.; Brear, D. J.; Shirakawa, Noriyuki*; Cao, X.; et al.
JNC TN9400 2003-071, 340 Pages, 2003/08
JNC-TN9400-2003-071.pdf:1.54MB
An advanced safety analysis computer code, SIMMER-III, has been developed to investigate postulated core disruptive accidents in liquid-metal fast reactors (LMFRs). SIMMER-III is a two-dimensional, three-velocity-field, multiphase, multicomponent, Eulerian, fluid-dynamics code coupled with a space-dependent neutron kinetics model. By completing and integrating all the physical models originally intended at the beginning of this code development project, SIMMER-III is now applicable to integral reactor calculations and other complex multiphase flow problems. A systematic code assessment program, conducted in collaboration with European research organizations, has shown that the advanced features of the code have resolved many of the limitations and problem areas in the previous SIMMER-II code. In this report, the models, numerical algorithms and code features of SIMMER-III Version 3.A are described along with detailed program description. Areas which require future model refinement are also discussed. SIMMER-III Version 3.A, a coupled fluid-dynamics and neutronics code system, is expected to significantly improve the flexibility and reliability of LMFR safety analyses.
; Brear, D. J.
Nuclear Engineering and Design, 189, p.337 - 357, 1999/00
Times Cited Count：40 Percentile：90.69(Nuclear Science & Technology)None
Brear, D. J.
PNC TN9410 98-005, 53 Pages, 1998/01
When liquid fuel makes contact with steel structure the liquid can freeze as a crust and the structure can melt at the surface. The melting and freezing processes that occur can influence the mode of fuel freezing and hence fuel relocation. Furthermore the temperature gradients established in the fuel and steel phases determine the rate at which heat is transferred from fuel to steel. In this memo the 1-D transient heat conduction equations are applied to the case of initially liquid UO brought into contact with solid steel using up-to-date materials properties. The solutions predict criteria for fuel crust formation and steel melting and provide a simple algorithm to determine the interface temperature when one or both of the materials is undergoing phase change. The predicted steel melting criterion is compared with available experimental results.
Morita, Koji; Brear, D. J.; Tobita, Yoshiharu; Kamiyama, Kenji;
Donen Giho, (101), p.21 - 28, 1997/00
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; Brear, D. J.; Tobita, Yoshiharu; Morita, Koji
Proceedings of 8th International Topical Meeting on Nuclear Reactor Thermal-Hydraulics (NURETH-8), Vo.3, p.1340 - 1348, 1997/00
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