Analysis of Self-Sustained Nuclear Fission Wave Evolution in a Fast Critical Reactor

Present paper deals with the phenomenon known as self-sustained nuclear fission wave that is set up with establishment of the U-Pu cycle in a fast nuclear reactor. The safety arised from self sustained state of the wave and also 50%the possibility of initiation and evolution of the wave, the system comprised of neutron diffusion equation coupled with burn-up and kinetic equations have been considered. The linearizationmethod used to solve this systemnot only separates diffusion subsystem from reaction one but also simplifies greately dealing with several real hundred days of simulation. Space and time discretizations of the linearized diffusion subsystem were performed by 3D finite element and crank nicolson methods, respectively. The convergence of equation was carried out using the iterations based on the optimized BiCGStab(L) method. Rung-Kutta (5) method was used to solve the first order differential equations of the reaction subsystem since the concentrations of elements in the reaction subsystem changed slowly. Using the element by element FEMand BiCGSta (L) used for solving the systemdropped the required memory down to 1/10. Considering the long period of the simulation, 3D case of the problem and heavy computations, the OpenMp method was used to parallelize the code written in FORTRAN 95.