Investigation of flow dynamics of primary coolant in a delay tank of a swimming pool-type nuclear reactor using radiotracer technique. (February 2020)

• Record Type: Journal Article
• Authors: 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
• Is Part Of: Applied radiation and isotopes. Volume 156(2020:Feb.)
• Publication Date: 2020-02
• Subjects: Delay tank -- Coolant -- Technetium-99m -- Residence time distribution -- Breakthrough time -- Mean residence time -- Bypassing -- Dead volume -- Axial dispersion model; Radiology -- Periodicals; Radiation -- Industrial applications -- Periodicals; Nuclear chemistry -- Periodicals; Internet resource; Periodical; 660.298
• DOI: 10.1016/j.apradiso.2019.108982
• Languages: English
• ISSNs: 0969-8043

Abstract

Abstract: 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. Highlights: RTDs of cooling water in a delay tank of a nuclear reactor were measured using technetium-99m as a radiotracer. Breakthrough time, mean residence time and dead volume were determined. Two parallel flow paths with bypassing of coolant were observed in the delay tank. Axial dispersion model was found suitable to model the measured RTD data. Based on the results of the investigations, design of the delay tank was modified.