Investigations of the suitability of the reflector drums as control mechanism for thermionic reactors in space craft with 233U as fuel and ZrH1,7 as moderator

The suitability of borated reflector drums has been investigated and shown as a control mechanism for thermomionic space craft reactors with 233U as fuel and ZrH1,7 as moderator due mainly to their extreme compactness. By optimal total cost of the reactor a reactivity change of 12% has been achieved. This allows the use of reflector drums which keep the cone diameter and the mass of the radiation shield to a minimum. In addition, reflector drums do not cause any kinematical disturbance. All important neutron physics calculations have been carried out with the multigroup SN methods. 123 energy groups, S4-P3 approximation by one-dimensional cylindrical geometry and four energy groups, S4-P1 approximation by r-? geometry have been used. Further, the behaviour of the neutron generation density function during different phases of the reactor control operation has been investigated. © 1978