From 7dfcc480ba1e19bd3232349fc733caef94034292 Mon Sep 17 00:00:00 2001
From: stainer_t <thomas.stainer@oecd-nea.org>
Date: Mon, 8 Sep 2025 13:48:49 +0200
Subject: Initial commit from Polytechnique Montreal

---
 Dragon/src/MCGSCEL.f | 85 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)
 create mode 100644 Dragon/src/MCGSCEL.f

(limited to 'Dragon/src/MCGSCEL.f')

diff --git a/Dragon/src/MCGSCEL.f b/Dragon/src/MCGSCEL.f
new file mode 100644
index 0000000..0355e69
--- /dev/null
+++ b/Dragon/src/MCGSCEL.f
@@ -0,0 +1,85 @@
+*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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