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Use of vertical slip flow and flooding models in LOCA analysis

Description: Vertical slip flow and flooding models, which have been incorporated in a version of the RELAP4 computer code by Aerojet Nuclear Company have led to significant improvements in modeling nuclear reactor coolant system phenomena during postulated large and small break loss-of-coolant accidents. The vertical slip flow model computes the separated fluid component velocities and directions at vertical flow junctions. Use of the slip model allows the energy transfer between volumes to be based on individual liquid and vapor component flows rather than on the net junction flow. Continuity and momentum equations are unaffected by the addition of slip. The vertical flow slip model logic is based on the assumption that gravity forces dominate causing slip between phases. 7 references (auth)
Date: January 1, 1975
Creator: Fischer, S.R.
Partner: UNT Libraries Government Documents Department

Experiment data report for 1-1/2-loop semiscale system isothermal Tests 1004 and 1006

Description: isothermal portion of the Semiscale Blowdown and Emergency Core Cooling (ECC) Project. These data represent the results of the first tests in the isothermal test series tn which simulated ECC injection during blowdown was inveatigated. The data, presented in the form of composite graphs in engineering units, have been analyzed only to the extent necessary to assure that they are reasonable and correct. The intent of this report is to make available the uninterpreted data from Tests 1004 and 1006 for use by others and for support of subsequent interpretative reports and analyses. (auth)
Date: March 1, 1974
Creator: Alder, R.S.; Feldman, E.M. & Pinson, P.A.
Partner: UNT Libraries Government Documents Department

Two phase pressure drop across abrupt area changes in oscillatory flow

Description: The ability of one-dimensional momentum balances to predict behavior during two-phase oscillatory flow has been examined. Flow oscillations in a Freon-Freon vapor system were induced by cycling a three-way valve so as to divert a varying portion of the total flow from the test section. The data taken included the phase shift between pressure and flow curves and the head fluctuation to flow fluctuation ratio. These data were compared to theoretical predictions. For void fractions below about 0.55, reasonable agreement between predictions and observations was obtained. At the highest void fractions examined, agreement between prediction and measurement was poor. However, at these high void fractions measurement errors may have been very substantial. Further, the simplifying assumptions required by the numerical calculation procedure chosen could no longer be considered valid. No real conclusion could therefore be drawn from the data at high voids. (auth)
Date: May 1, 1975
Creator: Weisman, J.; Ake, T. & Knott, R.
Partner: UNT Libraries Government Documents Department

Vertical slip flow and flooding models in LOCA analysis

Description: Vertical slip flow and flooding models have been incorporated in a version of the RELAP4 computer code in order to better model nuclear reactor coolant system phenomena during postulated large and small break loss-of-coolant accidents. Much of the complex hydrodynamic phenomena believed to occur during ECC injection, ECC bypass, liquid penetration into the downcomer, and lower plenum entrainment is multidimensional in nature leading to modeling difficulties when the present nonslip version of RELAP4 is used. Flooding type models in combination with vertical slip flow can be used to improve modeling of ECC bypass and liquid entrainment phenomena during reversed core flow. Applications to the analysis of core flow blockage phenomena also exist. Flooding used in this discussion denotes Wallis countercurrent type flooding phenomena which limits the maximum liquid downflow for a given vapor upflow. Flooding as used here does not refer to the deluge type reflood of a core. (auth)
Date: June 1, 1975
Creator: Fischer, S.R.
Partner: UNT Libraries Government Documents Department