Moderator acts as primary heat sink to arrest the unwarranted heat-up of fuel channels in the scenario of loss of coolant accident along with the unavailability of emergency core cooling system. In addition, severe heat-up of channel (which consists of fuel bundles, Pressure Tube, PT and Calandria Tube, CT) also occurs during any un-called for event of moderator-cooling/make-up system malfunctioning. Eventually, this all lead to the major loss in structural rigidity. Present investigation is performed to study the sagging deformation of PT for standardized 220MWe Indian PHWR. A scaled-down PT (1/3rd scale) is tested with a uniquely designed experimental setup that is capable of capturing high temperature sagging behavior. Results confirm that the Indian PT significantly deforms under thermally assisted rate-dependent plasticity (creep) above 600 °C. Post-test visual examination reveals no cracks in the PT, however a significant thinning of the PT near the junction of weight simulators is observed.

主持人充当主要散热器，以在发生冷却剂意外事故以及没有应急核心冷却系统的情况下，阻止燃料通道不必要的升温。此外，在减速器/补给系统发生故障的任何非要求事件中，还会严重地加热通道（由燃料束，压力管，PT和Calandria管组成）。最终，所有这些都会导致结构刚度的重大损失。目前进行的研究是为了研究标准220MWe印度PHWR PT的下垂变形。比例缩小的PT（1/3比例）已通过独特设计的实验设置进行了测试，该设置能够捕获高温下垂行为。结果证实，印度PT在高于600°C的热辅助速率依赖性塑性（蠕变）下会明显变形。测试后的目视检查未发现PT出现裂纹，但是在重量模拟器的交界处发现PT明显变薄。