The EU RTD activities in the field of nuclear fission safety (1994-98) included a number of multi-partner projects in Area B.3 'Reactor safety/severe accident : source term', which were grouped in a cluster known as 'ST', composed of 12 projects (eight 'shared-cost' and four 'concerted' actions) in which several organisations representing research centres, universities, regulators, utilities and vendors were involved. The total cost of these projects was about EUR 8.7 million and the EC contribution amounted to roughly EUR 4.8 million. This cluster complements some of the Phébus FP experiments, which are part of an international programme (also including many teams from the EU Member States) under the management of IPSN in Cadarache, France.