The invention relates to a storage device (1) for the storing and/or transporting of nuclear fuel assemblies, including a plurality of adjacent housings each having a lateral wall and being able to receive a nuclear fuel assembly, the lateral walls being realized at least in part using stacking and intercrossing slotted structural assemblies (6a, 6b), each structural assembly including at least one plate (22) realized in a first material comprising aluminum. According to the invention, each structural assembly (6a, 6b) further includes a tubular cross-section element (20) inside of which is located said at least one plate (22), this tubular cross-section element (20) being realized in a second material selected from steels and titanium and alloys thereof.