Pant Harish Jagat, Goswami Sunil, Sharma Vijay Kumar, Mukherjee Tanumoy, Mukherjee Kallol, Guchhait Paban Kumar, Rastogi Sachin, Pal Sanjit, Thomas Shibu, Mukherjee Pradip, Pujari Pradeep Kumar
Isotope and Radiation Application Division, Bhabha Atomic Research Centre, Mumbai, 400085, India.
Isotope and Radiation Application Division, Bhabha Atomic Research Centre, Mumbai, 400085, India.
Appl Radiat Isot. 2020 Feb;156:108982. doi: 10.1016/j.apradiso.2019.108982. Epub 2019 Nov 15.
Radiotracer investigations were carried out for tracing primary coolant in a delay tank of a swimming pool type nuclear reactor. The delay tank was designed to provide a certain delay or residence time to the primary coolant so that the short-lived radioisotopes such as (nitrogen-16 and oxygen-19) decay to a safer level before exiting from the delay tank. However, soon after commissioning of the reactor, the radiation levels at the exit of the reactor core and delay tank, in the working area were found to be higher than the permissible levels. Therefore, the main objectives of the investigations were to measure breakthrough and residence times and, to investigate flow dynamics of the coolant within the tank. Residence time distributions (RTDs) of the coolant were measured in the delay tank using technetium-99m as sodium pertechnatate as a radiotracer. The breakthrough time (BTT) and mean residence time (MRT) were determined from the measured RTD and the same were found to be inadequate to allow the decay of short-lived radioisotopes to the permissible levels. Axial dispersion model with two parallel flow streams was used to simulate the measured RTD curves. Results of the model simulation indicated bypassing of the coolant. Based on the results of the radiotracer investigations, necessary modifications were carried out in the design of the tank. After implementing the modifications, the radiotracer experiments were repeated and, the BTT and the MRT were found to increase sufficient enough to allow decay of the produced radioisotopes and thus to reduce the radiation levels at the exit of the delay tank and in the working area to the safer and permissible levels.
开展了放射性示踪剂研究，以追踪游泳池式核反应堆延迟罐中的一回路冷却剂。延迟罐的设计目的是为一回路冷却剂提供一定的延迟时间或停留时间，以便诸如（氮 - 16和氧 - 19）等短寿命放射性同位素在从延迟罐排出之前衰变到更安全的水平。然而，反应堆投运后不久，发现反应堆堆芯和延迟罐出口处、工作区域的辐射水平高于允许水平。因此，这些研究的主要目的是测量穿透时间和停留时间，并研究冷却剂在罐内的流动动力学。使用锝 - 99m作为高锝酸钠作为放射性示踪剂，在延迟罐中测量冷却剂的停留时间分布（RTD）。根据测得的RTD确定穿透时间（BTT）和平均停留时间（MRT），发现它们不足以使短寿命放射性同位素衰变到允许水平。采用具有两个平行流的轴向扩散模型来模拟测得的RTD曲线。模型模拟结果表明冷却剂存在旁通现象。根据放射性示踪剂研究结果，对罐的设计进行了必要的修改。实施修改后，重复进行放射性示踪剂实验，发现BTT和MRT增加到足以使产生的放射性同位素衰变，从而将延迟罐出口处和工作区域的辐射水平降低到更安全的允许水平。
