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*DECK MCGSCEL
SUBROUTINE MCGSCEL(N,K,M,NOM,NZON,H,XST,B)
*
*-----------------------------------------------------------------------
*
*Purpose:
* Calculate coefficients of a track for the characteristics
* integration. Linear-Discontinuous-Characteristics scheme with
* exact exponential calls. Source term isolation option turned off.
*
*Copyright:
* Copyright (C) 2015 Ecole Polytechnique de Montreal
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version
*
*Author(s): A. Hebert
*
*Parameters: input
* N number of elements in the current track.
* K total number of volumes for which specific values
* of the neutron flux and reactions rates are required.
* M number of material mixtures.
* NOM vector containing the region number of the different segments
* of this track.
* NZON index-number of the mixture type assigned to each volume.
* H vector containing the lenght of the different segments of this
* track.
* XST macroscopic total cross section.
*
*Parameters: output
* B LDC coefficients.
*
*-----------------------------------------------------------------------
*
IMPLICIT NONE
*----
* SUBROUTINE ARGUMENTS
*----
INTEGER N,K,M,NOM(N),NZON(K)
REAL XST(0:M)
DOUBLE PRECISION H(N),B(0:5,N)
*---
* LOCAL VARIABLES
*---
INTEGER I,NOMI,NZI
DOUBLE PRECISION TAUDMIN,SQ3,TAUD,HID,TEMP,DSIG,C1,C2,H2,H3,TEMP1
* tabulated exponential common block
PARAMETER ( TAUDMIN=2.0D-2)
*
SQ3=SQRT(3.0D0)
DO I=2,N-1
NOMI=NOM(I)
NZI=NZON(NOMI)
HID=H(I)
TAUD=HID*XST(NZI)
IF(TAUD.LE.TAUDMIN) THEN
* Use Taylor series expansions
H2=HID*HID
H3=H2*HID
B(0,I)=TAUD*(0.5D0*TAUD-1.0D0)+1.0D0
B(1,I)=HID*(TAUD*(TAUD/6.0D0-0.5D0)+1.0D0)
B(2,I)=H2*(TAUD*(TAUD-4.0D0)+12.0D0)/24.0D0
B(3,I)=-SQ3*H3*(TAUD*(TAUD-2.0D0)+4.0D0)/24.0D0
B(4,I)=-SQ3*TAUD*(TAUD*(TAUD-2.0D0)+4.0D0)/24.0D0
B(5,I)=H3*(TAUD*TAUD-TAUD+4.0D0)/40.0D0
ELSE
* Use exact exponential
TEMP1=EXP(-TAUD)
DSIG=DBLE(XST(NZI))
B(0,I)=TEMP1
TEMP=(1.D0-TEMP1)/TAUD
B(1,I)=TEMP*HID
B(2,I)=HID*(1.D0-TEMP)/DSIG
B(3,I)=-SQ3*HID*(2.0D0-(TAUD+2.0D0)*TEMP)/DSIG**2
B(4,I)=-SQ3*(2.0D0-(TAUD+2.0D0)*TEMP)/TAUD
C1=TAUD*(TAUD-6.0D0)-12.0D0
C2=TAUD*(3.0D0*TAUD+12.0D0)+12.0D0
B(5,I)=(C1+C2*TEMP)/(TAUD*DSIG**3)
ENDIF
ENDDO
*
RETURN
END
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