Static measurements of various nuclear core parameters were completed for the highly enriched plate-type Al-clad core to be used for the Spert I integral core destructive test program. Self-limiting power excursion tests were performed with initial asymptotic reactor periods in the range of 934 to 4.6 msec to establish the transient response of the core and to obtain data for extrapolation to shorter-period tests in which violent destructive effects are expected. For tests with periods shorter than about 7 msec, fuel plate deformations were produced as a result of thermal stresses in the plates. Melting of fuel plates was obtained in two tests with periods of 5 and 4.6 msec. For tests with periods in the range of 9 to 4.6 msec, power burst shape changes were observed which result in an increase in the ratio of the energy release in the total burst to that at the time of the power peak, as the period is shortened. Maximum transient pressures never exceeded 10 psi for tests thus far performed. A series of self-limiting power excursion tests was initiated in Spert II to determine the effects of the initial system temperature on the kinetic response of the D/sub 2/Omoderated expanded …

Additional data from the 3.2-msec-period destructive test were analyzed. Recovery and cleanup operations in the Spert I area were completed. Each of the 270 highly enriched, aluminum-clad fuel plates in the core was found to have experienced melting to some degree. The available data on the nature of the pressure pulse and on the condition of the core fuel plates at the time of the pulse are consistent with the hypothesis that the observed destructive effects were produced by a self-propagating steam explosion resulting from the dispersal of molten fuel plates into the water throughout the core. A series of tests was initiated to determine the response of the Spert IV plate-type core to step- inputs of reactivity at ambient temperature, for various initial system conditions of hydrostatic head above the core, and forced coolant circulation rate. Power excursion tests with initial reactor periods in the range from 1 sec to 8.5 msec were performed with an 18-ft hydrostatic head above the core and no forced coolant circulation. Tests with periods of 20, 12, and 8.5 msec were also performed with a 2-ft head. No significant change was observed in the peak power, power burst shape, energy release, or transient …