3. DESCRIPTION OF PROGRAM OR FUNCTION
(1) Problems to be solved:
MVP/GMVP can solve eigenvalue and fixed-source problems. The multigroup code GMVP can solve forward and adjoint problems for neutron, photon and neutron-photon coupled transport. The continuous-energy code MVP can solve only the forward problems. Both codes can also perform time-dependent calculations.
(2) Geometry description:
MVP/GMVP employs combinatorial geometry to describe the calculation geometry. It describes spatial regions by the combination of the 3-dimensional objects (BODIes). Currently, the following objects (BODIes) can be used.
- BODIes with linear surfaces : half space, parallelepiped, right parallelepiped, wedge, right hexagonal prism
- BODIes with quadratic surface and linear surfaces : cylinder, sphere, truncated right cone, truncated elliptic cone, ellipsoid by rotation, general ellipsoid
- Arbitrary quadratic surface and torus
The rectangular and hexagonal lattice geometry can be used to describe the repeated geometry. Furthermore, the statistical geometry model is available to treat coated fuel particles or pebbles for high temperature reactors.
(3) Particle sources:
The various forms of energy-, angle-, space- and time-dependent distribution functions can be specified.
(4) Cross sections:
The ANISN-type PL cross sections or the double-differential cross sections can be used in the multigroup code GMVP. On the other hand, the specific cross section libraries are used in the continuous-energy code MVP. The libraries are generated from the evaluated nuclear data (JENDL-3.3, ENDF/B-VI, JEF-3.0 etc.) by using the LICEM code. The neutron cross sections in the unresolved resonance region are described by the probability table method. The neutron cross sections at arbitrary temperatures are available for MVP by just specifying the temperatures in the input data.
(5) Boundary conditions:
Vacuum, perfect reflective, isotropic reflective (white), periodic boundary conditions can be specified.
(6) Variance reduction techniques:
The basic variance reduction techniques Russian roulette kill and splitting are implemented. In addition, importance and weight window based on them are available. Path stretching and source biasing can be also used.
The track length, collision, point and surface crossing estimators are available. The eigenvalue is estimated by the track length, collision and analog estimators for neutron production and neutron balance methods. In the final estimation, the most probable value and its variance are calculated by the maximum likelihood method with the combination of the estimators.
GMVP calculates the eigenvalue, the particle flux and reaction rates in each spatial region, each energy group and each time bin for each material, each nuclide and each type of reactions, and their variances as the basic statistical parameters. In addition to these physical quantities, MVP calculates the effective microscopic and macroscopic cross sections and the corresponding reaction rates in the specified regions. These quantities are basically tallied for each spatial region but can be tallied for the arbitrary combination of the regions with options. Furthermore, the calculated quantities are output to files and can be then used for the input data of a drawing program mentioned later or a burnup calculation code MVP-BURN.
(9) Drawing geometry:
The CGVIEW code draws the cross-sectional view on an arbitrary plane and output it on a display or in the postscript or encapsulated postscript form. These functions are useful for checking the calculation geometry.
(10) Burnup calculation:
The auxiliary code MVP-BURN implemented in the MVP/GMVP system is available for burnup calculations.
Parallel calculations can be performed with standard libraries MPI and PVM.
(12) Other capabilities:
MVP/GMVP has a capability of reactor noise analysis based on simulation of Feynman-alpha experiments.