Transient thermal analysis for radioactive liquid mixing operations in a large-scaled tank

Highlights: • A transient heat and mass balance model was developed to assess the impact of a submersible mixer. • The model was benchmarked against the test results to examine the thermal response of the tank. • Number of active cooling coils and coolant flow rate are dominant cooling mechanisms. • Maximum nuclear waste remains below boiling temperature under the reference operating conditions. • The mixer power provides dominant heat source, compared to the radioactive decay heat of tank contents. - Abstract: A transient heat balance model was developed to assess the impact of a Submersible Mixer Pump (SMP) on radioactive liquid temperature during the process of waste mixing and removal for the high-level radioactive materials stored in Savannah River Site (SRS) tanks. The model results will be mainly used to determine the SMP design impacts on the waste tank temperature during operations and to develop a specification for a new SMP design to replace existing long-shaft mixer pumps used during waste removal. The present model was benchmarked against the test data obtained by the tank measurement to examine the quantitative thermal response of the tank and to establish the reference conditions of the operating variables under no SMP operation. The results showed that the model predictions agreed with the test data of the waste temperatures within about 10%