Research Papers: Techniques and Procedures

Application of Fractional Scaling Analysis to Loss of Coolant Accidents, System Level Scaling for System Depressurization

[+] Author and Article Information
Wolfgang Wulff1

11 Hamilton Road, Setauket, NY 11733wolfgangwulff@optonline.net

Novak Zuber

703 New Mark Esplanade, Rockville, MD 20850wulff@bnl.gov

Upendra S. Rohatgi

 Brookhaven National Laboratory, Building 197D, Upton, NY 11973rohatgi@bnl.gov

Ivan Catton

 UCLA-MAE, P.O. Box 951597, 48-121 Engineering IV, Los Angeles, CA 90195-1597catton@ucla.edu


Corresponding author.

J. Fluids Eng 131(8), 081402 (Jul 20, 2009) (13 pages) doi:10.1115/1.3155994 History: Received October 24, 2008; Revised April 16, 2009; Published July 20, 2009

Fractional scaling analysis (FSA) is demonstrated at the system level. The selected example is depressurization of nuclear reactor primary systems undergoing large- and small-break loss of coolant accidents (LOCA), specifically in two integral test facilities of different sizes and shapes, namely, LOFT and Semiscale. The paper demonstrates (1) the relation between pressure and volume displacement rates in analogy to generalized “effort” and “flow” in interdisciplinary analysis of complex systems and (2) using experimental data that a properly scaled depressurization history applies to both large- and small-break LOCA in two different facilities. FSA, when applied at the system, component, and process levels, serves to synthesize the worldwide wealth of results from analyses and experiments into compact form for efficient storage, transfer, and retrieval of information. The demonstration at the system level shows that during LOCAs the break flow dominates for break sizes between 0.1% and 200% of cold-leg flow cross-sectional area, and that FSA ranks processes quantitatively and thereby objectively in the order of their importance. FSA supersedes the hereunto subjectively implemented phenomena identification and ranking table. FSA readily quantifies scale distortions. FSA reduces significantly the need for and current cost of experiments and analyses.

Copyright © 2009 by American Society of Mechanical Engineers
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Figure 1

Fractional change in pressure for different negative FRCs

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Figure 2

Measured large-break LOFT and Semiscale depressurizations: facility effects are scaled to preserve blow-down time

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Figure 3

Measured small-break LOFT and Semiscale depressurizations show effects of facility and break sizes on blow-down time

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Figure 4

Scaled large- and small-break LOCAs in LOFT: effects of break size on blow-down time is scaled

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Figure 5

Scaled large- and small-break LOCAs in Semiscale: effects of break size on blow-down time is scaled

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Figure 6

Scaled large-break LOFT and Semiscale depressurization: facility effects are scaled for 200% break size

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Figure 7

Scaled small-break LOFT and Semiscale depressurization: facility effects are scaled for 1 in. and 212% break sizes, respectively

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Figure 8

Small-break LOCA blow-down in LOFT and three break sizes in Semiscale. Pressurizer volume included in primary system volume. The legend shows break sizes for Semiscale and, in parentheses, recorded test durations. Compare with unscaled curves in Fig. 3.




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