Quenching studies of ballooned fuel pins have indicated enhancement of coolability for flow blockages ranging upto 90% with blockage extension of 6% (20 cm blockage length) under typical Emergency Core Cooling System (ECCS) injection rates. Similar enhancement is also observed for flow blockage of 45% with higher blockage extension of 60% and lower injection rates. An experimental setup is developed to assess the coolability under high flow blockage (upto 80% of the flow area) and longer ballooned length extensions (up to 60% or 600 mm). The setup employs 5 X 5 matrix of indirectly heated, pre-fabricated ballooned fuel pin simulator (FPS) surrounded with 20 heated and ballooned FPS which are further surrounded with 12 dummy FPS. The objective of this experiment is to study the effect of water injection rate on the quenching behaviour of large scale ballooned heated pins simulating early phase of severe accident. Bottom re-flood condition is considered for the study. The water injection rates (0.11–0.45 g/s per unit length per FPS) are kept lower than the typical PWR specific SAMG injection flow rates to assess minimum flow rate requirement. The FPS is observed to be coolable only when the injection rates are higher than a certain value. Higher quenching rate is observed in the region towards the entry of the ballooned length as compared to the region towards the exit of the ballooned length. Conduction controlled rewetting is found to be dominant for the entire range of injection rates considered for the experiments. Flow rates (0.11–0.45 g/s per unit length per FPS) are found to successfully quench the bundles. However, the FPS temperatures exceed the oxidation run-away threshold temperature for 10–25 g/s injection flow rates (0.11–0.275 g/s per unit length per FPS).

气球状燃料销的淬火研究表明，在典型的紧急堆芯冷却系统（ECCS）喷射速率下，流量阻塞的可冷却性提高了90％，阻塞扩展了6％（阻塞长度为20 cm）。对于45％的流量阻塞，也观察到了类似的增强，阻塞扩展率更高，达到60％，注入速率更低。开发了一种实验装置，以评估在高流量阻塞（最多80％的流量区域）和更长的气囊长度扩展（最多60％或600毫米）下的可冷却性。该设置采用5 X 5矩阵的间接加热的预制气球状燃料销模拟器（FPS），周围环绕20个加热的气球状FPS，并进一步包围12个虚拟FPS。该实验的目的是研究注水速率对模拟严重事故早期的大型气球加热销的淬火行为的影响。本研究考虑底部再注水条件。注水速率（每FPS每单位长度0.11-0.45 g / s）保持低于典型的PWR特定的SAMG注水速率，以评估最低流量要求。仅当注射速率高于特定值时，才观察到FPS是可冷却的。与朝向气球状长度的出口的区域相比，在朝向气球状长度的入口的区域中观察到更高的淬火速率。发现在实验考虑的整个注入速率范围内，传导控制的再润湿是主要的。流速（0.11–0。发现每FPS每单位长度45 g / s可成功淬灭束。但是，对于10–25 g / s的注射流速（每FPS每单位长度0.11–0.275 g / s），FPS温度超过了氧化失控阈值温度。