A Study of Consequences of Concrete Structures for Storage of Nuclear Wastes due to Permafrost

Rapport, 2013

This report presents the results from a study of consequences of freezing of concrete structures for storage of nuclear waste due to the action of permafrost. The experimental data measured from over 20 years aged cement paste specimens were used as input parameters of freezable water and mechanical properties. The model based on the poroelasticity was employed for calculation of overpressure of unfrozen liquid and strain of the porous body. The calculation results show that micro-cracking may occur due to ice formation in the fully water-saturated hardened cement pastes under the action of permafrost. The main consequences of this ice formation induced micro-cracking after one cycle of freezing-thawing at temperature –5°C and –10°C will be as follows: • The compressive strength of the silo concrete may in a normal case be reduced by 1% and 2%, respectively, and in the worst case by 15%, and the compressive strength of the 1 BMA concrete may in a normal case be reduced by 1% and 4%, respectively, and in the worst case by 19%. • The tensile strength of the silo concrete may in a normal case be reduced by 11% and 17%, respectively, and in the worst case by 45%, and the tensile strength of the 1 BMA concrete may in a normal case be reduced by 13% and 22%, respectively, and in the worst case by 51%. • The hydraulic conductivity of both the silo and the 1 BMA concrete may in a normal case be increased by not more than 2%, and in the worst case by not more than 10%. • It is hardly possible to lead a structural collapse due to the reduction in tensile strength in both the silo and the 1 BMA concrete containers filled inside with grout after filling of nuclear waste, unless the steel reinforcement in the reinforced concrete structure is designed with significantly less amount of steel bars and there exists large unfilled volume under the concrete roof.