An LNG system generally comprises a primary container, and a secondary container positioned around the primary container. The secondary container generally comprises a first end wall, a second end wall, and at least two side walls. At least one of the walls is fabricated from a plurality of prefabricated wall panels. Each of the wall panels is fabricated from a combination of concrete and steel. The wall panels are preferably prefabricated offsite, and then transported to the construction site where they are adjoined together in end-to-end fashion to form walls. A method for constructing a full containment LNG system is also provided. In one embodiment, walls and a roof for a secondary container are assembled, but leaving an end open. At least one primary tank is brought into the secondary container. A second end wall is then erected to form the enclosure for the secondary container.