An experimental study regarding the determination of seasonal heat transfer coefficient in KURT by convection conditions

In high-level radioactive waste repositories, heat is generated by the radioactive decay of the waste. This can affect the safety of the repository because the surrounding environment can be changed by heat transferred through the rock. Therefore, in order to ensure the safety of the repository, the temperature change of the atmosphere in the repository due to the heat generated by high-level radioactive wastes needs to be predicted and an appropriate heat reduction system is required. Through the construction of the KAERI Underground Research Tunnel (KURT) by Korea Atomic Energy Research Institute (KAERI), variable experiments about radioactive wastes disposal are in progress and the data on the properties of the surrounding rock in KURT had already been secured. As the internal heater section in KURT is heated by a heater that is 2 m in length and 5 kW in capacity it heats the inside of the rock in the research module by 90 °C, which is regarded as a similar environment to a disposal tunnel. In this study, the seasonal environmental factors (dry–wet-bulb temperature, rock surface temperature, altitude) under the natural and forced convection were measured at the heater section in KURT for the determination of heat transfer coefficient. The results showed that the heat transfer coefficients in the heater section had little seasonal difference. And the averages under natural convection and forced convection were determined 4.53 W/m2 K and 7.46 W/m2 K, respectively.

• The surrounding environment can be changed by heat transferred through the rock.
• The environmental factors were measured to determine the heat transfer coefficient.
• The averages under natural convection was determined 4.53 W/m2 K.
• The averages under forced convection was determined 7.46 W/m2 K.