A prototype expert system is developed to provide information to emergency planners on the time, rate, and magnitude of release of important radioactive isotopes given a loss of containment integrity. Basic to the method is the anticipated availability of instruments to measure concentration of significant individual radioisotopes in containment ∼1/min. The escape of radioisotopes is assumed to be proportional to that of noncondensable gases, which are monitored and/or predicted in part. If such a system can be executed practically, it would provide actual release information not available with monitoring systems currently deployed.