Determination of thermal properties of hardening concrete for massive nuclear shielding structures

Abstract

Nuclear reactor containments must maintain high durability since they restrict the spread of radiation and radioactive contamination to the general public, which could have significant consequences. The containment integrity and impermeability for potentially contaminated media is ensured using sophisticated structural and materials solutions including prevention of early age cracking of concrete. The results of numerical and experimental investigation on thermal behavior of early age concrete are presented. Concrete mixes were prepared with low-heat blended cements and various mineral aggregates. Special aggregates were selected for enhancing the radiation shielding capacity of concrete, including minerals of high atomic weight and of increased content of bound water. The proposed approach consisted of several stages, consisting mainly of measurements of the one-dimensional heat distribution in cylindrical concrete elements and solving the equation of one-dimensional heat transfer to determine thermal properties of hardening concrete. The proposed model of temperature distribution in hardening concrete is based on the non-linear inverse heat transfer problem solution. The obtained experimental results and numerically determined material characteristics are discussed in respect to the concrete mix design.