C PARDEC    SOURCE    CB215821  16/04/21    21:17:56     8920
C PARDEC     SOURCE    INSL       24/10/96
      SUBROUTINE PARDEC(ST,SIE,EPSC,EQSTR,EDC,IPLA,DEFR0,RB,ALPHA,EPO1,
     & EX,EMAX,ICAL)
C
      IMPLICIT INTEGER(I-N)
      IMPLICIT REAL*8(A-H,O-Z)
C
C             ***********************************************
C             **  CALCUL :  EPSC , EQSTR , EDC             **
C             ***********************************************
C
      FPT=ALPHA*RB
      DEFRL = RB/EX-EPO1
      DEFR0 = ST-SIE/EX
C
      IF(DEFR0.GT.DEFRL) THEN
         CALL EQUIV1(DEFR0,EPSC,EQSTR,EX,RB,EPO1,ICAL)
      ELSE
         A3  = RB/(EPO1-EMAX)
         B1  = -1.D0*EX*DEFR0
         B3  = A3*EMAX
         EPSC=(B3-B1)/(EX-A3)
         EQSTR=EX*EPSC+B1
         IPLA=2
      ENDIF
      EDC=(ABS(EQSTR)+RB)/(ABS(EPSC)+(RB/EX))
C
      IF(EDC.GT.EX.OR.EDC.LT.1.D-5) EDC=EX
      DEFR0 = EPSC-EQSTR/EDC
      EQSTR=ABS(EQSTR)
      IF(ABS(DEFR0).LT.1.D-8) DEFR0=0.D0
C
      RETURN
      END