Download Intro_RASKT_v3


The nodal diffusion code RAST-K is the second part of a conventional two-step approach code system, which is developed by UNIST CORE laboratory and sponsored by Korea Hydraulic & Nuclear Power Co. Ltd.. To achieve high accuracy of reactor analysis with affordable memory requirement and computing time, the pin-by-pin kernel is newly implemented in RAST-K v3. The neutron transport calculation is performed by solving pin-by-pin SP3 equation with axially unified nodal method. The pin-wise cross section data is corrected by SPH factor to preserve the accuracy of transport calculation. The depletion, TH feedback, and cross section feedback modules and user-supporting engineering features for convenience of reactor core design and analysis are extended from the sub-assembly to sub-pin level. The parallel computing capability is also applied to pin-by-pin kernel with high computing resources.


Physics Model


– Multi-group pin-wise SP3

– Assembly-wise CMFD acceleration

– UNM for axial layer

XS model

– Eight-group group constants from STREAM2D

– Full / Hot case matrices

– Save micro XS for micro depletion

– XS functionalization with 3D/2D Lagrange interpolation

– XS correction using SPH factor with assembly DF

TH feedback

– Single phase formulation (no boiling) without momentum equation (constant pressure)

– 1D radial heat conduction

– Consider TCD with FRAPCON-4.0 correlation

– CTF Steam table (IAPWS industrial formulation 2008)

Fuel cycle analysis

– Micro-depletion for 22 actinides and 12 fission products

– Effective Gd approach

– CRAM depletion solver


Domain Decomposition

All processor need to have …
‒ Geometry information (all mapping index)
‒ Basic 3D information: macro XS, flux, power, psi, Tfuel, Tmod, BU, …
‒ Count node per same XS type
‒ Arrange node for each processor
‒ Then, each processor have only pin XS in 1 FA
DD for Depletion
‒ Same domain with XSFB
‒ Number density & micro XS & reaction rate
DD for TH
‒ Only radially decomposition to solve  axial heat convection
DD for neutronics (SP3, UNM, not for CMFD)
‒ Same with TH, but, including mesh in reflector assembly



– OPR1000 cycle 1 whole core depletion

– Critical boron concentration


– Peaking factor


– Pin power distribution