Advanced Methodologies for Multigroup Cross Section Generation

Multigroup cross sections are necessary for deterministic neutronics calculation. The generation of the appropriate cross sections is fundamental to obtain accurate solutions of the transport equation. In the following diagram, it is depicted the standard collapsing procedure.

It is necessary to utilize appropriate methodologies for

There is no publicly available methodology for construction of group structure; hence, we have developed the CPXSD (Contribution and Pointwise Cross-Section Driven) methodology for generation of problem-dependent group structure. The standard methodology for collapsing does not account for angular dependency of differential cross sections; hence, we have developed a Bi-linear adjoint weighting methodology to address this issue.

Group Construction Methodology

The CPXSD (Contribution and Point-wise Cross-Section Driven) is a general, iterative, objective-dependent methodology

1. An arbitrary energy group structure is selected.
2. A “contribution” formulation is used to determine the importance of energy groups for the problem objective.
3. The point-wise cross sections of an important isotope is used to partition the energy groups.
4. Steps 2 and 3 are repeated until the change in objective value is within a given tolerance .

Contribution formulation

The CPXSD Methodology

[back to top]