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Tritium Release Experiments

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Tritium Release Experiments Powered By Docstoc
					  Tritium Extraction from a DCLL Blanket


               Prepared by: Scott Willms (LANL)
Collaborators: Brad Merrill (INL), Siegfried Malang (Consultant),
           Clement Wong (GA), Dai-Kai Sze (UCSD)

               Presented by: Jim Coons (LANL)

               Coordinating Meeting on R&D for
      Tritium and Safety Issues in Lead-Lithium Breeders

                          11 June 2007
                         Idaho Falls, ID



                                                             LA-UR-05-1711
Outline

•DCLL process overview
•Conventional separator
•T removal via vacuum permeator
•Model
•Mass transfer coefficient
•Parametric study
•DEMO design
•Issues
•Conclusions
   DCLL process overview
          He              Recover tritium
                          from He
                                         T2

                         Permeator
                He, T2
                                                   Breeder, T2, He


                                                                               T2, He     To Tritium
                                                      Use He to                           Plant
                               T2
                            Breeding                  strip T from
                                                      PbLi
                                       Dual Coolant
                                         Blanket                                                             To Tritium
                                                                           T2/Breeder                        Plant
                                                                 He
                                                                           Separator
      Heat
    Exchanger
                                              PbLi loop
                                         Breeder                           Breeder, T2
                 He

                                                                                     He, T2
    He loop
                         T permeation                                                             T2
                         thru HX tubes                          Heat
                                                              Exchanger
                                                                                  Permeator    Recover tritium
                                                                                               from He
Avg. T2 breeding
rate: 0.024 sccm                                                      He
                                                                                              He loop
Pressure in T2 separator tank if all tritium is contained
(no permeation, no stripping, etc.)
                                  14


                                  12
 Tritium Partial Pressure (atm)




                                  10


                                  8


                                  6


                                  4


                                  2


                                  0
                                       0   20   40       60        80   100   120
                                                     Time (days)
Rough estimate for tritium removal pathways from PbLi
with both tank pump off and HX permeation

                         1

                        0.9

                                                          Total tritium
                        0.8
                                                          removed

                        0.7
 Tritium Removed (gm)




                        0.6                           Tritium removed by
                                                      permeation through HX
                        0.5                           tubes

                        0.4

                        0.3

                        0.2
                                                          Tritium removed by
                        0.1                               mass transfer (through
                                                          collection tank)
                         0
                              0   20   40       60               80            100   120
                                            Time (days)
   Evaluating the possibility of using a vacuum permeator
   for tritium separation from Pb-Li
                   Recover tritium
                   from He




                                     Use
                                     Permeator
                                     to recover
                                     T from
                                     PbLi

                               PbLi loop


    He loop
                   T permeation
                   thru HX tubes
                                                  Recover tritium
                                                  from He
Avg. T2 breeding
rate: 0.024 sccm
                                                  He loop
Low Pressure Permeator Experimental Apparatus



                           66.0cm.
                            (26")

                                                                   Retentate
Permeate                                                            (Inert)
  (H2)
            10.2cm. (4")
To Vacuum
                                                                       Feed
                                                                    (Inert/H 2)


                                     27.7 cm (10.9")      0.635 cm
                                      total length x     (0.25") dia.
                                        0.318 cm       Stainless Steel
                                      (0.125") dia.         Tube
                                       Pd/Ag Tube
Experimental Setup


                                 P       GC

                                                    F        Vent


   H2       FC
                     T
                 P               P
                                                             Vent

                                 Turbo Pump   Backing Pump
                     Permeator
 Ar or N2   FC
With 25 sccm H2, the retentate and permeate are
initially in agreement and ultimately breakthrough is
observed at about 375 sccm. at 450 C
                      25 sccm H /N Flow                   2   2
                                                                                o




                   0.1


                  0.09


                  0.08


                  0.07       Constant 25 sccm H2
Pressure (torr)




                  0.06       Increasing N2

                  0.05       450 C

                  0.04


                  0.03
                                                                        Retentate Partial Pressure

                  0.02


                  0.01
                                                                                                     Permeate Pressure
                    0
                         0      100           200                 300                     400               500          600

                                                    Total Feed Flowrate (sccm)

                                         --Willms, R. Scott, Pamela R. Arzu, Kevin G. Honnell and Stephen A. Birdsell; "Initial
                                         Testing Of A Low Pressure Permeator For Tritium Processing"; Fusion Engineering and
                                         Design, 49-50, 963-970 (2000)
Mathematical model for PbLi/T permeator

• A component balance describes the tritium                  dx   D MW G
                                                                
  mass fraction along the membrane length                    dz     F

• Tritium transport to the membrane surface                            km 
                                                             Ni             xi  x 0 
  is described by a mass transfer coefficient                          MW
                                                                                    2
• The effective tritium partial pressure at the                   x            
                                                             pr   0
                                                                  k            
                                                                                
  membrane surface is given by the solubility                      s           
                                                           G kp
                                                                                          
                                                         _
• Permeation depends on the permeability                 G                    pr  p p
                                                           A  l
                                                  Gtot
                        Membrane          T2



   F, Ci                G                                     F, Ci


                        Dz
   PbLi, T                                                   PbLi, T

               z
                                                                         Mass Transfer Coefficient (m/s)
2.
   W                    1.
       et                    Pl
         te                       at
             d                         e,




                                                                0.0000
                                                                         0.0005
                                                                                  0.0010
                                                                                           0.0015
                                                                                                    0.0020
                                                                                                             0.0025
                                                                                                                      0.0030
                                                                                                                               0.0035
                                                                                                                                        0.0040
                 Tu                         La
                   be                             m
                        /P                         in
                           l   at                        ar
                                    e,
                                           La
                                             m
                      3.                          /T
                            Pl                       u  rb
        4.                     at
             W                      e,
                                           La
                 et
                   te                           m
                        d                        /T
                            Tu                     ur
                                 be                         b
                                       ,T
                                         ur
                                                bu
                                                     le
                                                          nt

                      6.
                            Pl                       5.
                                 at                         ?
                                      e,
                                           Tu
                      7.                      r bu
                            Tu                       le
                                 be                       nt
                                       ,T
                                         ur
                      8.                          bu
                            Tu                         le
                                 be                       nt
                                       ,T
                                         ur
                      9.                          bu
                            Tu                         le
       10                        be                       nt
             .P                        ,T
                 ac                      ur
                      ke                          bu
                         d                             le
                             Be                           nt
                                                                                                                                                 Comparison of mass transfer coefficient results




                                    d,
                                           Tu
                                                rb
                                                  ul
                                                       en
                                                            t
The mass transfer coefficient for this system was
estimated from general correlations

•   10 general correlations were considered

•   The following correlation appeared to be
    the most appropriate:
                                                                xi
                                                                            x0   liq to solid
          km D                                               liq bulk-to-        xfer
                0.0096 Re 0.913 Sc 0.346                    surface mass   pr
          D AB                                               xfer

                                                                                                pp
                                                             permeation
    --Harriott and Hamilton, Chem Engr Sci, 20, 1073, 1965   through membrane          solid to gas
                                                                                       xfer

•   However, this correlation was developed
    with benzoic acid and glycerin-water
    mixtures at room temperature—
    considerably different from 700 C PbLi
    and tritium
Values used to solve the model

 Description                      Value                           Value in other units
 Temperature                                         973.150 K                          700 C
 Permeate Pressure                              1.32E-008 atm                        1.E-5 torr
 Membrane Diameter                                      0.01 m                            1 cm
 Membrane wall thickness                             5.00E-4 m                     500 microns
 Area for flow of PbLi                            7.85E-05 m2
 Molecular weight of tritium                      0.006 kg/mol                      6 gm/mole
 Tritium solubility in PbLi            0.162 mol T/m3/atm^0.5
 Tritium solubility in PbLi        5.5E-8 kg T/kg PbLi/atm^0.5
 Diffusivity of tritium in PbLi                  8.87E-9 m2/s
 Tritium solubility in Nb              6740 mol T/m3/atm^0.5
 Tritium diffusivity in Nb                       1.24E-8 m2/s
 Permeability of tritium in Nb     4.16E-5 mol T2/m/s/atm^0.5
 Viscosity of PbLi                               7.4E-4 kg/m/s
 Density of PbLi                                   8813 kg/m3
 Flow velocity                                            5 m/s
 Volumetric flowrate                             3.93E-4 m3/s
 Schmidt Number                                            9.47
 Reynolds Number                                       595000.
 Mass transfer coefficient                         3.47E-3 m/s
 Beta-Collection of constants                            61200
 Mass fraction of T in feed                              2.E-10      1.E-2 torr partial pressure
Using these base conditions the tritium concentration
down the length of the permeator was determined

                                     2.5E-10                                                                1.E-02




                                                                                                                     Equilibrium partial p of T over PbLi (torr)
                                                                                                            1.E-02
                                     2.0E-10
  Mass fraction of tritium in PbLi




                                                                                                            8.E-03
                                     1.5E-10

                                                                                                            6.E-03

                                     1.0E-10           Practical Length of Tube?
                                                                                                            4.E-03
                                                                                   Exit Conc. Target
                                     5.0E-11
                                                                                                            2.E-03



                                     0.0E+00                                                                0.E+00
                                               0   5                        10                         15
                                                   Distance along tube (m)
Performance depends strongly on the mass transfer
coefficient

                                    2.5E-10


                                                  1.3 Pa (1x10-2 torr)

                                    2.0E-10
 Mass fraction of tritium in PbLi




                                                                                                      0.00005 m/s


                                    1.5E-10
                                                                                                        0.0005 m/s

                                                            km=0.0035 m/s (base case)
                                    1.0E-10
                                                                             0.005 m/s

                                                                                                            Exit Conc. Target
                                    5.0E-11

                                                  0.05 m/s                                              0.0013 Pa (1x10-5 torr)
                                                        0.5 m/s

                                    0.0E+00
                                              0         2           4         6          8       10          12         14        16
                                                                         Distance along membrane tube (m)
                                   Wall thickness

                                   2.50E-10




                                   2.00E-10
Mass fraction of tritium in PbLi




                                   1.50E-10




                                   1.00E-10
                                                  Wall=0.0005 m
                                                  (base case)
                                                                      Wall=0.005 m                  Exit Conc. Target
                                   5.00E-11
                                                                  Wall=0.00005


                                   0.00E+00
                                              0          2        4        6         8        10    12        14        16
                                                                          Distance along tube (m)
Surface Concentration

                                   2.50E-10




                                   2.00E-10
Mass fraction of tritium in PbLi




                                   1.50E-10


                                                            In bulk
                                   1.00E-10


                                                                                                    Exit Conc. Target
                                   5.00E-11


                                                  At tube surface
                                   0.00E+00
                                              0         2             4   6         8         10       12         14    16
                                                                          Distance along tube (m)
                Permeability

                                   2.50E-10




                                   2.00E-10
Mass fraction of tritium in PbLi




                                   1.50E-10                            kp=Nb/1000
                                                                       (like Fe)
                                                      kp=Nb/10
                                                      (like Pd)
                                   1.00E-10
                                                           kp=Nb/100

                                                                                            Exit Conc. Target
                                   5.00E-11


                                                        kp=Nb (base case)
                                   0.00E+00
                                              0   2    4          6         8         10      12         14     16
                                                                  Distance along tube (m)
                                   PbLi Flowrate

                                   2.50E-10




                                   2.00E-10
Mass fraction of tritium in PbLi




                                   1.50E-10
                                                                v=50 m/s



                                   1.00E-10                            v=10 m/s
                                                  v=0.5 m/s

                                                   v=2.5 m/s
                                                                                                        Exit Conc. Target
                                   5.00E-11
                                                              v=5 m/s
                                                              (base case)

                                   0.00E+00
                                              0           2           4           6     8         10    12         14       16
                                                                              Distance along tube (m)
                    Feed concentration

                                1.00E-08




                                1.00E-09
Mass fraction tritium in PbLi




                                                                x0=2x10-9



                                               x0=2x10-10(base case)                                  Exit Conc. Target
                                1.00E-10




                                1.00E-11
                                               x0=2x10-11




                                1.00E-12
                                           0    2           4           6        8         10    12          14           16
                                                                       Distance along tube (m)
Tube diameter does significantly affect performance


                                   2.50E-10




                                   2.00E-10
Mass fraction of tritium in PbLi




                                                                             Tube Diameter

                                   1.50E-10



                                                                D=0.02 m
                                   1.00E-10


                                                                                               Exit Conc. Target
                                   5.00E-11

                                                                                    D=0.01 m (base case)
                                                  D=0.005

                                   0.00E+00
                                              0   2         4      6        8         10       12          14      16
                                                                  Distance along tube (m)
                                Permeate pressure

                                2.50E-10




                                2.00E-10
Mass fraction tritium in PbLi




                                1.50E-10




                                1.00E-10                     Pperm=1x10-5 torr (base case)


                                                                                             Exit Conc. Target
                                5.00E-11
                                                                                                 Pperm=1x10-4 torr
                                                       Pperm=1x10-6 torr

                                0.00E+00
                                           0   2   4          6            8      10           12         14         16
                                                             Distance along tube (m)
Considerations for a practical PbLi permeator

•   PbLi flowrate for Demo: 26270 kg/s
•   With 1 cm dia. tubes and 5 m/s flow velocity: 7592 tubes
•   Total Nb required for 5 m tubes: 2.6 tons
•   Total cost for Nb: ~$0.5M (?)
•   Diameter of vessel to contain tube cross sections + twice that
    area for space between tubes: 1.7 m



    This permeator is a substantial vessel, but one that can
    practically be constructed
While this initial analysis indicates that a PbLi permeator may be
feasible, there are many issues that must be resolved

• Measured mass transfer coefficients for the PbLi-T system
• Compatibility of PbLi with Nb at 700 C
• Additional resistances to tritium permeation such as surface
  resistance?
• At the PbLi-membrane interface, is the effective partial pressure
  exerted by tritium indeed given by the solubility equation? (this
  may be a very different mechanism with a very different rate)
• What pressure can be practically maintained on the permeate
  side of the membranes?
• Will Nb tubes degrade due to reactions such as oxidation? Will
  a surface treatment be needed?
Conclusions

• Tritium permeation through the heat exchanger materials will be
  substantial and cannot be neglected
• Tritium can be recovered from helium streams with gas
  permeators and other technologies
• A reasonable plan for ITER TBM ancillary equipment is to
  include a helium bubbler on the PbLi loop and permeators on
  both He loops
• A potentially attractive option is a PbLi permeator to directly
  remove tritium from PbLi. Based on present information such a
  device might be practical.
• Whether or not it is actually practical would require considerable
  R&D

				
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posted:10/6/2011
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