[en] A computer-aided simulation is developed to analyze the transient behavior of loop type liquid metal-cooled fast breeder reactor plants. A set of nuclear, heat transfer, sodium dynamics, steam/water thermodynamics and control models for the multi-loop plant is developed to simulate operational, incident and accident transients. The major important features of the model include: (1) a multi-loop simulation, consisting of a single loop and the remaining lumped loops; (2) a method to calculate the characteristic times for every differential equation, and apply the Runge--Kutta algorithm to variables with slow and moderate time responses as compared to the integration time step and evaulate the variables with fast responses from a prompt approximation to assure numerical stability and reduce the computation time; and (3) a pre-accident initialization method by forcing most variables into their prompt approximation. The analytical submodels of the EPRI--CURL Code simulates: (a) the dynamics of sodium flows in the primary and secondary systems governed by forced and natural circulation; (b) reactor heat transfer; (c) neutron kinetics, reactivity feedbacks, and reactor power control; (d) intermediate heat exchanger heat transfer; (e) sodium transport delays in the primary and secondary systems; (f) steam/water thermodynamics, normal feed water flow and auxiliary feed water flow control; and (g) turbine header, throttle, steam bypass and relief flow control. There is a total of 489 first order ordinary differential equations modelling the entire plant. The EPRI--CURL systems analysis computer code for loop-type liquid metal cooled fast breeder reactors is used to model the plant response of a typical LMFBR to several transient conditions