Modification of a Dynamic Monte Carlo Technique to Simplify and Accelerate Transient Analysis with Feedback

Abstract

In this paper, a simpler approach compared to the existing approaches is developed to analyze nuclear reactor dynamics based on the explicit Monte Carlo method. A new population control method is also introduced to prevent neutron population growth and consequent computer memory shortages, which also increases simulation speed. The scheme is applied for time-dependent particle tracking in three-dimensional arbitrary geometries in the presence of feedbacks through a code named MCSP-Explicit. Changes in material density, as well as geometry dimensions, are also considered during simulation. MCSP-Explicit can be run with either continuous or multigroup data libraries, and it is further boosted by parallel processing to speed up simulations. A number of benchmark problems are studied at the end to evaluate the performance of the proposed approach in various situations.

Keywords:

• Monte Carlo method
• dynamic Monte Carlo
• transient analysis
• MCSP code
• feedback

Nomenclature

$E_f$	=	= recoverable energy per fission
$N{c}_j$	=	= population of delayed neutron precursor of j’th group
$Nd$	=	= number of delayed neutrons
$Np$	=	= number of prompt neutrons
$P$	=	= power generated
$T$	=	= time of simulation
$w_n$	=	= weight of neutron

Greek

${\beta }_j$	=	= decay fraction of delayed neutron precursor of j’th group
$\mathrm{\Delta }T$	=	= time step
${\lambda }_j$	=	= decay constants of delayed neutron precursor of j’th group
$\nu$	=	= average number of neutrons released per fission
$\xi$	=	= random number
${\mathrm{\Sigma }}_f$	=	= average macroscopic fission cross section in system
$\upsilon$	=	= average speed of neutrons in system
$\phi$	=	= normalized scaler flux extracted by the MCSP code