[en] The drafted main volume was submitted for review comment to other organizations also concerned with HTRs; most of the criticism advanced could still be taken into account in the final version. General Atomic Comp. assessed the radiological consequences and risk with models of their own and found good agreement with AIPA values. Weak points in the system design of the HTR-1160 plant were identified in the main study, leading to certain unrealistically high risk contributions. Improvements are being proposed in the supplementary studies reported here, which may be justified from a technical point of view and probably would have been called for or taken into account anyway in the further pursuance of the project. The influence on release frequencies and, thus, on risk contributions is assessed by consideration of the modified design in existing fault trees. In this connection it was found that the frequency of core heatup can be totally reduced by a factor of 5. It is even more important to note that the frequency of event sequences involving a failure of the reactor containment and massive environmental releases even decreases by one to two orders of magnitude. Water-ingress accidents become almost insignificant for the risk. (orig.)