Power cutbacks as an alternative to scrams: an application of the MIT-SNL period generated minimum time control laws

A cutback is a rapid reduction in a reactor's neutronic power caused by the high-speed insertion of the control devices. The advantage of using cutbacks in lieu of scrams is that the cutback may make the reactor only slightly subcritical while still significantly decreasing the power. Thus, the thermal stress associated with a complete shutdown is avoided, and a rapid return to normal operation is possible. The physical basis for cutbacks is reviewed. and possible areas of application are enumerated. At present, cutbacks are implemented by inserting the control devices at a prespecified speed. The power will decrease, but neither the profile nor the magnitude of the decrease is specified. As a result, cutbacks are not used extensively in reactor safety systems. Use of the Massachusetts Institute of Technology-Sandia National Laboratories (MIT-SNL) period-generated minimum time control laws to rectify these deficiencies is proposed