def max_fuel_in_storage_rule(mod, prj, tmp):
    """
    **Constraint Name**: Fuel_Prod_Max_Fuel_in_Storage_Constraint
    **Enforced Over**: FUEL_PROD_OPR_TMPS

    The amount of fuel stored in each operational timepoint cannot exceed
    the available fuel storage capacity.
    """
    return (
        mod.Fuel_Prod_Starting_Fuel_in_Storage_FuelUnit[prj, tmp]
        <= mod.Fuel_Storage_Capacity_FuelUnit[prj, mod.period[tmp]]
        * mod.Availability_Derate[prj, tmp]
    )