A method was developed for faster than real-time liquid-metal fast breeder reactor intermediate heat exchanger (IHX) analysis for purposes of continuous on-line data validation, plant state verification, and fault identification. The basic feature of this method is the utilization of spatial nodes whose sizes vary with time. The use of time-variant node sizes leads to adequately accurate solutions with a few nodes and at short computation times. Applications of this methodology to reference IHX problems with the IBM 3033 machine showed that the computation time for steady-state analysis was ∼6 ms. For transient analysis, a computation time that was one-sixteenth of the real transient time was achieved. This time can be further reduced if the special sparse structure of the system Jacobian matrix is exploited. The analysis of the Experimental Breeder Reactor-II test 8A showed that the maximum difference between temperatures predicted by this methodology and measurements was ∼6K.