The phenomenon of a long-term time expansion of frozen Lead-Bismuth Eutectic (LBE) should be taken into account for the integrity of liquid metal (LM) steel containers (4 m long cylinder) during operation and handling of a spallation neutron source target, (e.g. transportation of the target in a horizontal position as a simple supported beam, stiffer by connection with solidified LBE). The temperature dependency of the LBE time expansion in the range from freezing (approx. 125 °C) to room temperature (RT) and the effect of mechanical constraints are unknown. The experimental investigations have been performed at Paul Scherrer Institute (PSI) on a model of LM container from steel. The model has been instrumented with strain gauges (SG) and thermocouples (TC). The results show, that after two weeks from solidification of the LBE inside of LM container, the connection between both metals: steel and LBE, has caused the overstressing of the steel container. The maximal strains occur at the lowest exposure temperature and are located in the lower part of the LM container near the hemispherical enclosure of the cylindrical vessel. With rising temperature the strains decrease drastically. The extent of expansion in the direction of constraint was found markedly smaller than that communicated for freely expanding conditions. This behavior can be explained by plastic flow of the LBE and the decrease of the shear yield stress of the LBE caused by rising temperature. To avoid the overstressing of the embrittlemented steel in area of the hemispherical proton beam entrance window, the special zone freezing procedure has been proposed.