A digital computer analysis of the loss-of-coolant accident in the primary system of a multicircuit core nuclear power plant in the event of a complete severance of a pressure or jumper tube is presented. The time-dependent mass, momentum, and energy balance differential equations are expressed in finite difference form and solved numerically on an IBM-7090 digital computer together with the equations of state, system boundary conditions, and constraints. The system mass flow rate, pressure, and enthalpy distribution are calculated together with the other important system properties as functions of time during the transient operation following the break. The application of the analysis to the Carolinas-Virginia Tube Reactor indicates that the loss-of-coolant accident could lead to flow starvation in the reactor core and steam formation in the primary pump with subsequent core damage if no corrective action were taken. The flow starvation and steam formation problems are solved by the operation of a high pressure, high capacity emergency injection pump with fast starting characteristics.