Abstract
The paper describes the first of a series of three tests designed to obtain information about the nozzle assemblies on reactor pressure vessels under a variety of loading conditions, with a view to predicting their behaviour in service. This first test is concerned with the effect of loadings which cause yielding in the nozzle region, and while overloads as severe as those described cannot occur in practice, the results enable a quantitative assessment to be made of the margins between operating pressure and failure pressure as far as shortterm yielding is concerned. They also provide data which will be of interest when improved design methods, involving higher working stresses, are considered.
The test was carried out on a spherical vessel containing a small group of oblique nozzles, manufactured to represent a nozzle layout typical of reactor vessels, at scale size. The vessel was hydraulically pressurized up to 1670 1b/in2 gauge when failure occurred through the heat-affected zones of the nozzle to shell welds. The basic shell stress at failure was approximately equal to the ultimate tensile strength of the material.
Strain readings recorded during the tests, and the results of the metrological surveys, carried out on the vessel before and after testing, are discussed in the report.
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