A sealing system of a burner basket in an ammonia oxidation burner, wherein the burner basket has a wall that is anchored in the ammonia oxidation burner and the burner basket has a gas-permeable bottom plate, which is placed on further internal fittings of the ammonia oxidation burner and has a peripheral rim, wherein the wall and the gas-permeable bottom plate are not mechanically connected to each other, and so there is a gap between the wall and the peripheral rim of the bottom plate, wherein at the peripheral rim of the bottom plate a rim seal that is made up of individual segments is mounted movably by way of guiding pins and the rim seal projects over the gap between the peripheral rim of the bottom plate to the wall and lies against the wall.