THE DECISION-SUPPORT SYSTEM OF PSI, AND HOW IT MEETS THE NEEDS OF THEUSERS

Four categories of users of a decision support system (DSS) are charac terised particularly with respect to their know-how and needs: scienti sts, technicians, radiation safety officers and decision makers. The c apabilities of a modem DSS of high performance lie in reliability, fle xibility and user-friendliness. These features are put into perspectiv e of the potential user needs, which are not necessarily compatible. M issing know-how has to be compensated either by expert judgement or by more complex monitoring and modelling. The DSS structure at PSI allow s capabilities of different performance to be grouped in basically two levels of problem complexity with two operational levels (interactive or automatic) each to four modes, which are compatible with different users' needs. The system is designed to simulate the atmospheric tran sport of radioactive effluents in flat and complex terrain in real tim e. The automatic operation of a DSS - with all its limitations - is an important step to a better overall performance of the system even for difficult problems such as atmospheric transport in complex terrain: particularly, in connection with data assimilation for unknown release s. So far, the challenge of meeting the needs of most DSS users is ach ievable.