Un problema statico relativo a reattori nucleari di nuova generazione

Recent proposals for innovative nuclear power plant design consider steam generator tubes pressurized from outside. If sized according to presently accepted procedures, such as the Boiler & Pressure Vessel Code of the American Society of Mechanical Engineers (ASME), the resulting thickness is extremely high. This entails a major contribution of the thermal conduction through the wall thickness to the thermal resistance in the heat exchange process between primary and secondary fluids, with detrimental consequences on the steam generator design. ASME code seems excessively conservative for very thick tubes, which have found limited engineering application so far. Their collapse behavior has been explored little if at all and the code apparently reacts to this lack of knowledge by assuming a very conservative attitude. This papers aims at a rational assessment of this behavior, based on the interpretation of computational results by means of a comparatively simple formula. It is shown that significant thickness reductions can be achieved without jeopardizing safety.