Nuclear Science and Engineering / Volume 155 / Number 2 / February 2007 / Pages 223-235
Technical Paper / Mathematics and Computation, Supercomputing, Reactor Physics and Nuclear and Biological Applications
This paper presents recent developments of the acceleration techniques for the method of characteristics (MOC) in the code APOLLO-2. The main contribution concerns the introduction of a multidomain DPN technique where all regions belonging to the same macrodomain are coupled by an integral operator that is strictly equivalent to the MOC. Different macrodomains are coupled via currents that are defined with the DPN formalism. This new integral DPN(IDPN) operator is built by using transmission and escape probability factors that respect symmetries/antisymmetries and complementary properties that are enforced to preserve the physics of the problem and to save computational effort. These factors are computed using the numerical tracking of the MOC operator. This paper presents results on realistic assembly calculations that demonstrate the effectiveness of the IDPN operator as a synthetic acceleration tool.