REACTOR POWER TRANSIENTS AS CALCULATED BY THE SPACE INDEPENDENT REACTOR EQUATIONS

A number of reactor power transients were calculated as a part of the ETR and MTR safety systems analysis. These calculations were performed on the IBM-650 digital computer by numerically integrating the basic non-linear space- independent reactor equations (with delayed neutrons). The transients are of two basic types: linear withdrawal of the control rods with a subsequent accelerated scram; and step reactivity insertion followed by an accelerated scram. As these calculations are primarily descriptions of hypothetical accident conditions, they must not be overly optimistic. Comparing identical transients, assuming the existence and non-existence of delayed neutrons, shows the desirability of using the more complex reactor equations as an aid to the establishment of safe operating limits. The energy release as calculated by assuming no delayed neutrons may be too small by as much as a factor of two. It should be noted that even though these calculations contain a small degree of sophistication, actual reactor transients may be quite different. Factors such as void and temperature coefficients, neutron energy spectrum, boiling, meltdown, etc., were not considered. Many of these neglected effects operate as shutdown mechanics in the actual reactor; therefore, the magnitudes of the calculated overshoots are in error to somemore » degree. The transient periods and reactor power are probably accurate below a value of about 2 n/sub f/. (auth)« less