A sealed and thermally insulated tank arranged in a bearing structure to contain a fluid, said tank comprising tank walls fixed to walls of said bearing structure, a tank wall having in succession, in the thickness direction from the inside toward the outside of said tank, a primary sealed barrier, a primary thermally insulating barrier, a secondary sealed barrier and a secondary thermally insulating barrier, the tank further comprising a through-element (7, 910) arranged through the tank wall, in which tank the tank wall around the through-element comprises: secondary insulating blocks arranged on the wall of the bearing structure around the through-element and forming the secondary thermally insulating barrier around the through-element so that the through-element passes through the secondary thermally insulating barrier between said secondary insulating blocks, the secondary insulating blocks being covered by a first sealed layer forming the secondary sealed barrier, a plate (722, 923) arranged parallel to the tank wall having a surface facing toward the inside of the tank at the same level as the first sealed layer (17, 932) forming the secondary sealed barrier, the plate being connected in a sealed manner directly or indirectly to a peripheral wall of the through-element all around the through-element, a second sealed layer (723, 936, 823, 1036) fixed in a sealed manner straddling the first sealed layer and the plate all around the plate in which tank the tank wall further comprises primary insulating elements arranged on the secondary sealed barrier around the through-element and forming the primary thermally insulating barrier around the through-element so that the through-element passes through the primary thermally insulating barrier between the primary insulating elements, the primary insulating elements being covered by primary sealed barrier elements which are connected in a sealed manner to the peripheral wall of the through-element so that the through-element passes through the primary sealed barrier between the primary sealed barrier elements, characterized in that the plate (722, 923) is a circular plate having a circular exterior shape, and in that the second sealed layer comprises a circular window having a diameter smaller than the outside diameter of the circular plate, the secondary sealed barrier being passed through by the through-element through the window of the second sealed layer. secondary insulating blocks arranged on the wall of the bearing structure around the through-element and forming the secondary thermally insulating barrier around the through-element so that the through-element passes through the secondary thermally insulating barrier between said secondary insulating blocks, the secondary insulating blocks being covered by a first sealed layer forming the secondary sealed barrier, a plate (722, 923) arranged parallel to the tank wall having a surface facing toward the inside of the tank at the same level as the first sealed layer (17, 932) forming the secondary sealed barrier, the plate being connected in a sealed manner directly or indirectly to a peripheral wall of the through-element all around the through-element,