In August 1998, the Nuclear Regulatory Coml,lission (NRC) approved the final version of a revised rule on the acceptance of emergency core cooling systems (ECCS) entitled 'iEmergency Core Cooling System: Revisions to Acceptance Criteria."" The revised rule states an alternate ECCS performance analysis, based on best-estimate methods, may be used to provide more realistic estimates of plant safety margins, provided the licensee quantifies the uncertainty of the estimates and * Ttlis work WJS fuIIdd hy the US Nuclc,lr l{cg[ll,]~ory Cornlniss ion (NRC), of Tit c of Nll(.

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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.

A small scale model (length 1710 mm) of General Motor SUV was built and tested in the wind tunnel for expected wind conditions and road clearance. Two passive devices, rear screen which is plate behind the car and rear fairing where the end of the car is aerodynamically extended, were incorporated in the model and tested in the wind tunnel for different wind conditions. The conclusion is that rear screen could reduce drag up to 6.5% and rear fairing can reduce the drag by 26%. There were additional tests for front edging and rear vortex generators. The results for drag reduction were mixed. It should be noted that there are aesthetic and practical considerations that may allow only partial implementation of these or any drag reduction options.