| This dissertation is a preliminary study of a nuclear powered reciprocating steam expansion engine. The design features a fissile material rich piston, that upon insertion into a fissile material rich cylinder overcomes the condition for nuclear criticality to produce heat, steam, and finally thermodynamic work with high efficiency. In this design, sub-cooled liquid water is cyclically injected into specially-designed heat transfer cavities where it expands. The rate at which water flashes to steam is a function of the position of the piston(s) and the associated criticality insertion. As the piston approaches the top dead center position (TDC), it inserts positive reactivity which is translated into heat on the surfaces of the heat cavities. The pressure increase due to the expansion of the steam causes the piston(s) to move down from its TDC position generating the power stroke.;Such a structure, constitutes a highly efficient heat-work conversion engine which can be coupled with conventional electric generators. Furthermore, elements of the design produce energy savings since the rate of entropy associated to the two-step processes of heat addition in the boiler and expansion in the expander is reduced, thereby enhancing the efficiency and reducing the rate of environmental degradation. The analysis of high rate steam expansion processes inside the specially designed heat transfer cavities has been conducted by using electronically controlled heating elements which simulate the nuclear fuel heat transfer characteristics. A working analogue of the nuclear powered steam engine has been utilized for the validation of the analytical model and the optimization of the various parameters toward an enhanced cycle efficiency. The results of the analysis, verified by the data obtained from the working analogue, show the feasibility of an engine which is based on controlled high rate steam expansion. |
