Fast Vector Computation of the Characteristics Method

Abstract

Two numerical algorithms, an odd-even sweep (OES) method and an independent sequential sweep (ISS) method, for the fast neutron transport computation by the characteristics method on vector computers have been developed. The neutron tracking procedure is based on the newly devised vectorized sweeps with long vector length, which enables efficient vector processing in comparison with the ordinary forward sweep. Numerical tests have been done on FUJITSU FACOM VPP-5000 for a realistic PWR fuel assembly. The results show that the vector computation with either of the two methods reduces the computation times to one-fifteenth comparing with the scalar computation. Of the two methods, the ISS method is recommended, because the ISS method gives faster convergence and requires smaller memory size than the OES method.

KEYWORDS:

• characteristics method
• neutron transport
• heterogeneous geometry
• vector computation
• odd-even sweep
• independent sequential sweep
• fuel assemblies
• sweep efficiency
• calculation method