Measurement of helium thermophysical properties and modification of the calculation models in the KTA 3102.1 report

Helium is a commonly used circulating working fluid in high-temperature gas-cooled reactors (HTGR). The thermophysical properties of helium are crucial for HTGR design and operation. The isobaric specific heat capacity, viscosity and thermal conductivity of helium were determined in this study based on flow method, capillary method and dynamic light scattering (DLS) method, respectively. To fill the data gap, the measurements were conducted over a temperature range of 293 K∼773 K and at pressures up to 7 MPa. The relative uncertainty estimates for the experimental apparatuses of isobaric specific heat capacity, viscosity, and thermal conductivity are less than 0.9%, 1.4%, and 2.2%, respectively. Based on the experimental data, the deviation of the existing calculation models for isobaric specific heat capacity, viscosity and thermal conductivity were analyzed. The calculation model posted by the Nuclear Safety Standards Commission (KTA) was modified to improve the reliability in the target p-T region.