[en] The purpose of this publication is to provide guidance to Governments and Port Authorities on the various procedures and precautionary measures that may be employed when nuclear merchant ships use ports and approaches. The problem is basically that of siting a nuclear reactor in a populated area, with the extra factor of mobility. Added to this is the fact that the safety standards of the nuclear ship may be those of a country other than that of the port of entry. Thus the problem must be solved in international agreements.