MORE THAN 30 YEARS OF REACTOR THERMAL-HYDRAULICS

Reactor thermal hydraulic research began together with the first light water reactor early in the sixties. Extensive experimental research p rograms have been carried out to increase understanding of the behavio r of light water reactors under accident conditions and to validate th e computer code developed. An example of the developmental stages for a system code is given. Problems associated with the use of system cod es are identified and possible solutions are given. The application of system codes in the design and licensing of innovative reactors and t he development and qualification of uncertainty methodologies, constit ute issues of current interest in this area of research that are consi dered in the present paper. Perspectives and requirements for future r esearch are outlined.