Thermal-stress analysis of rock formations for nuclear fuel and waste storage

ADINA and ADINAT in partnership have provided a unique tool for analysis of heat flow, temperature distribution, and underground stresses and deformations due to excavation and storage of nuclear fuel and/or waste cannisters in hard rock formations. During this work we have determined successful and unsuccessful combinations of elements and properties for both the thermal and the stress analyses. In addition, we have determined a need for thermal radiation transport between portions of the model, as contrasted to radiation between the model and its surroundings. This latter need has been met in the interim by use of nonlinear bar conductors, and it will be satisfied in the future by a special user subroutine at ADINAT. The geological modeling was preceeded by a period of code testing and verification during which it was found that at least one material model did not produce correct thermal stresses even though the thermal deformations were correct. We also found that thermal stresses were likely to be in apparent error due to differences in the way in which ADINA interpolates the temperature and strain fields within each element. Solutions to this problem are discussed