Estimation of mcp-195m elements stress-strain state at the initial dynamics of shaft jamming/mpa transient process
DOI:
https://doi.org/10.15276/opu.3.59.2019.04Keywords:
CFD-simulation, MCP, impeller, transient process, strength assessment, BLOCA, CAE-modelAbstract
MCP is an important element for NPPs safe operation. During the lifetime prolongation project for domestic power units, special attention is paid to assessment of MCPs body state. First, this is because pump body serves as a safety barrier, and that it is a hard-replaceable NPP element. The MCP elements integrity is estimated for many representative emergency transients, which are calculated using system thermal hydraulics codes (RELAP/CORSAR). In the best case, in such codes the pump unit can be represented by first order inertial link model, which makes it possible to simulate its run-out. However, such models cannot fundamentally reproduce MCP dynamic during the instantaneous change in torque, as well as during shock changes in absolute pressure. This actually leads to uncertainties of initial dynamics for such transients that can effect on their qualitative and quantitative characteristics. In fact, obtained by nodal thermal hydraulic codes results are irrelevant, i.e. it is unclear whether they underestimate or overestimate thermal parameters important for future strength calculations. This work presents simplified CFD-models and CAE-models of MCP-195М for analysis of transient process with pump jamming initial dynamics. There is an uncertainty regarding the absolute value of dynamic loads amplitude when pump shaft is jamming. It is also incomprehensible to which phenomena group we should refer this process, and is taking account of it phenomena due prolongation of MCP elements service life is critical. Developed CFD-model includes coolant domain and CAE-model of MCP construction elements, which create a unidirectional fluid – solid interaction interface. CFD-model was validated for a correspondence with experimental pump characteristics. For analysis of transient process in flow MCP part “compressible liquid method” was used. Initially, this method was tested for correct prediction of classical water hammer characteristics. Stress assessment of MCP elements indicates that strength criterions are satisfied. Pressure change amplitudes obtained using CFD for initial dynamics
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