diff --git a/documentation/proc-pages/physics-models/fusion_reactions/plasma_reactions.md b/documentation/proc-pages/physics-models/fusion_reactions/plasma_reactions.md
index 2c2349d118..52b1f5cc78 100644
--- a/documentation/proc-pages/physics-models/fusion_reactions/plasma_reactions.md
+++ b/documentation/proc-pages/physics-models/fusion_reactions/plasma_reactions.md
@@ -11,7 +11,7 @@ $$
Roughly 20% of the energy produced is given to the alpha particles (\(^4\)He). The remaining 80% is carried
away by the neutrons, which deposit their energy within the blanket and shield and other reactor components.
-The fraction of the alpha energy deposited in the plasma is [`f_alpha_plasma`](#coupled-alpha-particle-power).
+The fraction of the alpha energy deposited in the plasma is [`f_alpha_plasma`](#coupled-alpha-particle-power).
**`PROCESS` only assumes the alpha power produced is coupled to and self heats the plasma, other charged particles do not.**
PROCESS can also model D-\(^3\)He power plants, which utilise the following
@@ -38,11 +38,11 @@ $$\begin{aligned}
\mathrm{D + D} & \Longrightarrow \mathrm{T + p + 4.03 \,MeV}
\end{aligned}$$
-Also, as tritium is produced by the latter reaction, D-T fusion also occurs.
+Also, as tritium is produced by the latter reaction, D-T fusion also occurs.
As a result, there is still a small amount of neutron power
extracted from the plasma.
-Pure D-\(^3\)He tokamak power plants do not include breeding blankets, because
+Pure D-\(^3\)He tokamak power plants do not include breeding blankets, because
no tritium needs to be produced for fuel.
The contributions from all four of the above fusion reactions are included in
@@ -56,7 +56,9 @@ profiles
The fractional composition of the 'fuel' ions ($\text{D}$, $\text{T}$ and $^3\text{He}$) is
controlled using the three variables `f_deuterium`, `f_tritium` and `f_helium3`, respectively.
-More information about setting seeded impurities and simulating first wall sputtering can be found in the [composition and impurities section](../plasma_composition.md)
+More information about setting seeded impurities and simulating first wall sputtering can be found in the [composition and impurities section](../plasma_composition.md).
+
+It is also possible to optimise on the deuterium-tritium fuel mixture ratio. For this, `f_tritium` **must** be set as an iteration variable with `ixc = 173`. More info can be found [here](#fuel-ions-mixture-self-consistency).
!!! note "Reactions not calculated"
@@ -232,5 +234,13 @@ This constraint can be activated by stating `icc = 28` in the input file.
The value of `bigqmin` can be set to the minimum desired $Q_{\text{plasma}}$ value. The scaling value `fqval` can be varied also.
+-------------------------
+
+### Fuel ions mixture self-consistency
+
+This constraint can be activated by stating `icc = 92` in the input file.
+
+This constraint should be activated if the user wishes to allow the ratio of the fuel ions to be iterated upon. For this, `f_tritium` has to be set as an iteration variable with `ixc = 173`. This constraint ensure that the summation of the fuel fractions always sums to 1.0 and will modify the other compositions depending on the value of `f_tritium`.
+
[^1]: H.-S. Bosch and G. M. Hale, “Improved formulas for fusion cross-sections and thermal reactivities,” Nuclear Fusion, vol. 32, no. 4, pp. 611–631, Apr. 1992, doi: https://doi.org/10.1088/0029-5515/32/4/i07.
-[^2]: I. P. E. G. on E. Drive and I. P. B. Editors, “Chapter 5: Physics of energetic ions,” Nuclear Fusion, vol. 39, no. 12, pp. 2471–2495, Dec. 1999, doi: https://doi.org/10.1088/0029-5515/39/12/305.
\ No newline at end of file
+[^2]: I. P. E. G. on E. Drive and I. P. B. Editors, “Chapter 5: Physics of energetic ions,” Nuclear Fusion, vol. 39, no. 12, pp. 2471–2495, Dec. 1999, doi: https://doi.org/10.1088/0029-5515/39/12/305.
diff --git a/source/fortran/constraint_equations.f90 b/source/fortran/constraint_equations.f90
index 34ea74886f..5cf3816860 100755
--- a/source/fortran/constraint_equations.f90
+++ b/source/fortran/constraint_equations.f90
@@ -286,6 +286,8 @@ subroutine constraint_eqns(m,ieqn,cc,con,err,symbol,units)
case (90); call constraint_eqn_090(tmp_cc, tmp_con, tmp_err, tmp_symbol, tmp_units)
! Constraint for indication of ECRH ignitability
case (91); call constraint_eqn_091(tmp_cc, tmp_con, tmp_err, tmp_symbol, tmp_units)
+ ! Constraint for D/T ratio
+ case (92); call constraint_eqn_092(tmp_cc, tmp_con, tmp_err, tmp_symbol, tmp_units)
case default
idiags(1) = icc(i)
@@ -3387,6 +3389,32 @@ subroutine constraint_eqn_091(tmp_cc, tmp_con, tmp_err, tmp_symbol, tmp_units)
tmp_units = 'MW'
end subroutine constraint_eqn_091
+ subroutine constraint_eqn_092(tmp_cc, tmp_con, tmp_err, tmp_symbol, tmp_units)
+ !! Equation for checking is D/T ratio is consistent, and sums to 1.
+ !! author: G Turkington, UKAEA
+ !! args : output structure : residual error; constraint value;
+ !! residual error in physical units; output string; units string
+ !! f_deuterium : input : fraction of deuterium ions
+ !! f_tritium : input : fraction of tritium ions
+ !! f_helium3 : input : fraction of helium-3 ions
+ use physics_variables, only: f_deuterium, f_tritium, f_helium3
+ implicit none
+ real(dp), intent(out) :: tmp_cc
+ real(dp), intent(out) :: tmp_con
+ real(dp), intent(out) :: tmp_err
+ character(len=1), intent(out) :: tmp_symbol
+ character(len=10), intent(out) :: tmp_units
+
+
+ ! Iterate over f_tritium and calculate f_deuterium
+ f_deuterium = 1.0D0 - (f_tritium + f_helium3)
+ tmp_cc = 1.0D0 - (f_deuterium + f_tritium + f_helium3)
+ tmp_con = 1.0D0
+ tmp_err = tmp_con * tmp_cc
+ tmp_symbol = '='
+ tmp_units = 'fraction'
+
+ end subroutine constraint_eqn_092
end module constraints
diff --git a/source/fortran/iteration_variables.f90 b/source/fortran/iteration_variables.f90
index 4a2b3f17e7..26efdcd508 100755
--- a/source/fortran/iteration_variables.f90
+++ b/source/fortran/iteration_variables.f90
@@ -3850,31 +3850,28 @@ subroutine set_itv_172(ratio)
casths = ratio
end subroutine set_itv_172
- !---------------------------------
- ! DUMMY variables below here
- !---------------------------------
- !---------------------------------
-
subroutine init_itv_173
- !! (173) DUMMY : Description
+ !! (173) f_tritium : Tritium fraction in fuel
use numerics, only: lablxc, boundl, boundu
implicit none
- lablxc(173) = 'DUMMY '
- boundl(173) = 1.0d-99
- boundu(173) = 1.0d99
+ lablxc(173) = 'f_tritium '
+ boundl(173) = 0.000
+ boundu(173) = 1.000
end subroutine init_itv_173
real(kind(1.d0)) function itv_173()
- implicit none
- itv_173 = DUMMY
+ use physics_variables, only: f_tritium
+ itv_173 = f_tritium
end function itv_173
subroutine set_itv_173(ratio)
- implicit none
+ use physics_variables, only: f_tritium
real(kind(1.d0)) :: ratio
- DUMMY = ratio
+ f_tritium = ratio
end subroutine set_itv_173
+ !---------------------------------
+ ! DUMMY variables below here
!---------------------------------
subroutine init_itv_174
@@ -4117,8 +4114,8 @@ subroutine loadxc
case (170); xcm(i) = itv_170()
case (171); xcm(i) = itv_171()
case (172); xcm(i) = itv_172()
- ! DUMMY Cases
case (173); xcm(i) = itv_173()
+ ! DUMMY Cases
case (174); xcm(i) = itv_174()
case (175); xcm(i) = itv_175()
diff --git a/source/fortran/numerics.f90 b/source/fortran/numerics.f90
index 22e3ae219a..051868d370 100755
--- a/source/fortran/numerics.f90
+++ b/source/fortran/numerics.f90
@@ -19,7 +19,7 @@ module numerics
integer, parameter :: ipnvars = 175
!! ipnvars FIX : total number of variables available for iteration
- integer, parameter :: ipeqns = 91
+ integer, parameter :: ipeqns = 92
!! ipeqns FIX : number of constraint equations available
integer, parameter :: ipnfoms = 19
@@ -193,7 +193,9 @@ module numerics
!! (88) Constraint for TF coil strain absolute value
!! (89) Constraint for CS coil quench protection
!! (90) Lower Limit on number of stress load cycles for CS (itr 167 fncycle)
- !! (91) Checking if the design point is ECRH ignitable (itv 168 fecrh_ignition)
+ !! (91) Checking if the design point is ECRH ignitable (itv 168 fecrh_ignition)
+ !! (92) D/T/He3 ratio in fuel sums to 1
+
integer, dimension(ipnvars) :: ixc
!! ixc(ipnvars) /0/ :
@@ -374,7 +376,7 @@ module numerics
!! (170) beta_div : field line angle wrt divertor target plate (degrees)
!! (171) casths_fraction : TF side case thickness as fraction of toridal case thickness
!! (172) casths : TF side case thickness [m]
- !! (173) EMPTY : Description
+ !! (173) f_deuterium : Deuterium fraction in fuel
!! (174) EMPTY : Description
!! (175) EMPTY : Description
! Issue 287 iteration variables are now defined in module define_iteration_variables in iteration variables.f90
@@ -545,7 +547,9 @@ subroutine init_numerics()
'TF coil strain absolute value ', &
'CS current/copper area < Max ', &
'CS stress load cycles ', &
- 'ECRH ignitability ' &
+ 'ECRH ignitability ', &
+ 'Fuel composition consistency ' &
+
/)
! Please note: All strings between '...' above must be exactly 33 chars long
diff --git a/tests/unit/test_power.py b/tests/unit/test_power.py
index f1b1510ebb..73e243a4b8 100644
--- a/tests/unit/test_power.py
+++ b/tests/unit/test_power.py
@@ -952,6 +952,7 @@ class PfpwrParam(NamedTuple):
False,
False,
False,
+ False,
),
ioptimz=1,
tim=np.array(
@@ -1694,6 +1695,7 @@ class PfpwrParam(NamedTuple):
False,
False,
False,
+ False,
),
ioptimz=1,
tim=np.array(
diff --git a/tests/unit/test_pulse.py b/tests/unit/test_pulse.py
index af23de9a5e..23965c0eaa 100644
--- a/tests/unit/test_pulse.py
+++ b/tests/unit/test_pulse.py
@@ -647,6 +647,7 @@ class BurnParam(NamedTuple):
False,
False,
False,
+ False,
),
i_pulsed_plant=1,
outfile=11,
@@ -1204,6 +1205,7 @@ class BurnParam(NamedTuple):
False,
False,
False,
+ False,
),
i_pulsed_plant=1,
outfile=11,