The problem is treated of high-temperature heat and mass transfer in a layer of concrete for biological protection of nuclear reactors at critical heat loads. The processes of evaporation of adsorbed moisture and the reaction of dehydration are taken into account. The set of nonlinear unsteady-state differential equations of heat and mass transfer is solved by the finite difference method. The numerical analysis is performed for a wide range of temperature variation. It is shown that the process of dehydration of concrete during heating to 800-900 K leads to formation in concrete of a high-pressure zone (up to 5 × 105 Pa) of gaseous products of evaporation and dehydration. The level of attendant stresses exceeds considerably the ultimate strength of typical grades of concrete for respective values of high temperature. It is further found that the process of dehydration of high-grade concrete with low porosity may result in higher pressures as compared with low-grade concrete. The results of numerical analysis serve as a basis for a more exact calculation of temperature fields in the biological protection layer of nuclear reactors, as well as for computation of the stress-strain state of concrete and for prediction of the reliability of operation of power reactors as a whole.
|Состояние||Опубликовано - сен 1999|
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)