Abstract: Various improvements of a modular wall assembly of the type having panels with channels formed along the side edges of the panels are described. The improvements include the formation of at least the channels, and the surface of the panels adjacent to the closed ends of the channels, of a material resistant to the passage of electrical radiation. Connection assemblies are provided for the joinder of adjacent panels located either in the same plane or in intersecting planes which include elements which continue the electrical radiation barrier of the panel surface and channel across the joint. The connection assemblies provide structural strength to the modular wall assembly, facilitate the creation of acoustically and electrical radiation resistant enclosures, and allow the removal of individual panels from the assembly for inspection and/or replacement without substantial effect upon the remainder of an enclosure structure. The panels and the connection assemblies are also acoustically insulated.