[en] The COVA programme of small scale experiments consist of a two pronged attack, on the provision of high quality accurate data for validating explosion containment codes. This paper examines some effects arising from the inclusion in the model geometries of either thin or over strong outer tanks, of hemispherical or right cylindrical bases or of simple internals. The main energy source for the COVA programme is a low pressure high explosive which has been especially developed by the UK for use in model test series. The paper describes the characterisation of this low density explosive which is based on a PETN/polystyrene mix expanded, under strictly controlled heating, to form self supporting charges of various sizes. This characterisation, involving the analysis of cylinder tests and underwater firings of bare spheres, shows that the explosive performs in a reproducible manner in both dry and wet environments. The development of a JWL equation of state is illustrated and discussed. The explosion containment codes being developed within the UK are the 2-D Lagrangian code ASTARTE-3 and the 2-D Eulerian code SEURBNUK-2, the latter being currently developed jointly with JRC, Ispra. Both codes are able to deal with transient compressible flow in deformable primary containment tanks, with various geometries of internal components, depending upon the limitations of Lagrangian or Eulerian concepts and the current state of the development of both codes. (Auth.)