Tests were conducted to evaluate methods of simulating on a small scale the effect of nuclear reactor “runaway” on a containment shell surrounding the reactor. Test results from air-filled core vessels were compared with existing blast data from bare chemical explosives and also with Brode's theoretical analysis of spherical blast waves to find the applicability of the test data to the concept of equivalent weight of bare charge. Additional tests were conducted with explosive charges bursting water-filled simulated reactor core vessels. These test results showed that shock waves were formed in air close to bursting vessels, and that the pressure-time histories differed considerably from the “classical” free air blast waves from bare charges. The concept of equivalent weight would therefore not apply to the latter experiments.