A number of conceivable reactivity accidents were analyzed, using conservatively pessimistic assumptions and approximations, to permit evaluation of reactor safety. Most of the calculations, which are described in detail, were performed by a digital kinetics program, MURGATROYD. Some analog analyses were also made. None of the accidents which were analyzed lead to catastrophic failure of the reactor, which is the primary consideration. Some internal damage to the reactor from undesirably high temperatures could result from extreme cold- slug accidents, premature criticality during filling, or uncontrolled rod withdrawal. Each of these accidents could happen only by compounded failure of protective devices, and in each case there exists means of effective corrective action independent of the primary protection, so that damage is unlikeIy. The calculated response to arbitrary ramp and step additions of reactivity show that damaging pressures could occur only if the addition is the equivalent of a step of about 1% delta k/k or greater. (auth)