Merrill Tritium permeation issues by x5YKdrJ


									Tritium Permeation in

Brad Merrill1, Phil Sharpe1, Dai-Kai Sze2

1INLFusion Safety Program

FNST Meeting
UCLA, August 12th-14th, 2008
Presentation Overview

     • This presentation examines Dual Cooled Lead Lithium (DCLL)
       and Helium Cooled Lead Lithium (HCLL) blanket tritium
       inventory and permeation rates as impacted by tritium:
            Solubility in PbLi
            First wall (FW) implantation
            Reduced turbulent mass transport in PbLi
     • The results are based on a TMAP model developed for the
       ARIES-CS DCLL design, with the model modified to give an
       intermediate helium cooling system to Rankine cycle in place
       of ARIES-CS Brayton cycle
     • This TMAP model was also modified to simulate a HCLL
       blanket in ARIES-CS based on Melodie experimental results
     • Conclude with a summary
ARIES-CS Design Parameters
                                                ARIES-CS Power Parameters
                                Fusion Thermal Power in Blanket                     2480 MW
                                Typical Module Dimensions                           ~4 m2 x 0.62 m
                                Tritium Breeding Rate                               ~400 g/d
                                PbLi Inlet/Outlet Temperatures                      464/737°C
                                PbLi Inlet Pressure                                 1 MPa
                                Typical Inner Channel Dimensions                    0.26 m x 0.24 m
                                Average PbLi Velocity in Inner Channel              ~0.04 m/s
                                Fusion Thermal Power removed by PbLi                1323 MW
                                PbLi Total Mass Flow Rate                           25,910 kg/s
                                Maximum PbLi/FS Temperature                         472°C
                                He Inlet/Outlet Temperatures                        385/460°C
                                He Inlet Pressure                                   10 MPa
                                Typical FW Channel Dimensions (poloidal x radial)   2 cm x 3 cm
                                He Velocity in First Wall Channel                   46 m/s
Layout of ARIES-CS Power Core   He Inlet/Outlet Temperatures                        385/460°C
                                Total Mass Flow Rate of Blanket He                  3559 kg/s
                                Maximum Local ODS/RAFS Temperature at FW            654/550°C
      ARIES-CS Tritium Extraction
                               Vacuum Permeator Concept                            T2
                            Vacuum                      Niobium Membrane

    QPb-17Li                                                                                              QPb-17Li
    CT,I                                                                                                  CT,O

                                                                                                          Membrane diffusion
• All PbLi component models (blanket gaps, pipes,                                 Pb-17Li                               CT
  permeator, and HTX) account for turbulent enhanced                                                        T  - DT
  transport of tritium in the PbLi
                                                                                mass transport                           x
•   Correlationaproposed by Scott Willms used to model                      T  K m CT,Bulk  CT,S1 
    turbulent mass transport enhancement:
                   K m D tube
                                                                                        CT,Bulk                           C T,S3  Ks P
                                 0.0096 Re 0.913Sc 0.346
                   D T, Pb17Li                                                         QPb-17Li
• Tritium solubility and diffusivity correlations                                                                         Or CT,S3 based
  developed by Reiterb and Teriac                                                                          CT,S1          on molecular
                   K s  2.32x108 n PbLiexp(1350/RT)                                                                    T2  r C2 S3
                                                            m  Pa1/2

                   D  2.5x10 7 exp(27000/RT)                                              CT,S2   K
                                                      s                                             S, Nb
                                                                                             CT,S1 KS, Pb-17Li
                                    aHarriot  and Hamilton, Chem Engr Sci, 20 (1965) 1073
                                    bReiter, FED 14 (1991) 207-211
                                    cTeria, J. Nucl. Mater. 187 (1992) 247-253
           Schematic of ARIES-CS DCLL TMAP Model
 Non-Hartmann    PbLi core    Shield   Manifolds

                                                               He/PbLi Nb HX


                                                                                                He/H2O Al HX

  Rib walls

              Back                                                               Helium Cycle
                             Concentric pipes

                             Helium pipes                 He/He FS HX

                                                                    Tritium cleanup
    Tritium Inventory and Permeation Results For DCLL
                                   Ks-Reiter   100 x Ks-Reiter       FW           Km/5
                                                                 Implantation                • Based on TMAP results,
                                                                                               increasing the solubility of tritium
Tritium source                    ~400 g/d       ~400 g/d         ~940 g/d      ~400 g/d
                                                                                               in PbLi by 100 increases the PbLi
                                                                                               tritium inventory by ~12, but
Structure1                         335 g           86 g            2500 g        1850 g        surprisingly reduces the reactor
PbLi                                1.0 g         11.5 g            2.6 g         3.0 g
                                                                                               structural inventory and
                                                                                               permeation rate
Release2                           0.9 g/a       0.03 g/a          3.4 g/a3      3.0 g/a3
                                                                                             • This is due to the fact that the
Permeator overall efficiency        70%            7.7%             73%          26.5%
                                                                                               concentration jump at all
Tritium pressure                                                                               PbLi/metal interfaces drops by
                                                                                               100 while the PbLi concentration
PbLi                              0.17 Pa      1.3x10-3 Pa         0.86 Pa       1.1 Pa
                                                                                               increase of ~12 produces a
Helium                           1.4x10-2 Pa   9.0x10-4 Pa         0.9 Pa        0.5 Pa
                                                                                               balance between tritium
Tritium global balance                                                                         production and extraction
Permeator                          99.8%          99.9%            98.2%         96.7%
                                                                                             • Tritium release is at or near
Helium cleanup system              0.15%        2.0x10-2%           1.7%          2.4%
Leaked                           1.0x10-2%      2.0x10-3%           0.1%          0.2%       198%   of this inventory is in the Nb alloy HTX and
Permeates to VV                  4.0x102%       8.0x10-3%            0%           0.7%         because reactor has 6 sectors only 1/6th is at
                                                                                               risk during most accident
Permeation into Rankine cycle                                                                299% ventilation flow cleanup is assumed
                                                                                             3Limit is < 1 g/a
                                                                                             4Based on CANDU water concentration of ~1
Intermediate helium cycle         360 Ci/a5       93 Ci/a        2160 Ci/a5     1690 Ci/a5
                                                                                               Ci/kg (34,000 Ci/a allowed into Rankine cycle)
Direct (required reduction)4/5       47               0           1.7x103         1.1x103    5Based on US PWR water concentration of ~ 1
                                  /4.7x103           /2           /1.7x105       /1.1x105      mCi/kg (340 Ci/a allowed into Rankine cycle)
 Melodie* Results used to Investigate Extraction Column Tritium
           Removal for an ARIES-CS HCLL Blanket

80 cm

                                                                                                20 cm

   • The extractor column used in Melodie experiments was a Sulzer
     Mellapak 750 Y series
   • The extraction column was 60 mm in diameter, 800 mm in height,
     and had an area packing of 750 m2/m3

                                                                                  Sulzer Column
                                     Alpy, et al., FED, 49-50 (2000) 775-780.
                                                                                (not a 750 Y series)
              Schematic of ARIES-CS HCLL TMAP Model

   Poloidal      PbLi core    Shield   Manifolds           PbLi/He HX

                                                                     823 K

                                                                     673 K
 wall                                                                                               He/H2O Al HX
                                                   PbLi Pipes                 gas
 Rib walls

              plate                                             He/He FS HX               Intermediate
                                                                                          Helium Cycle

                             Helium pipes

                                                                        Tritium cleanup
   Melodie Experimental Loop Results for Sulzer Extraction
            Column and Application to ARIES-CS
            Melodie Results
                                      • Melodie measured extractor efficiencies were ~25% based
                                        on concentration, i.e.          pH 2
                                      • For this TMAP model, the reactor PbLi processing flow
                                        rate is assumed to be 300 kg/s, giving a change out rate of
                                        eight times per day 
                                      • All external volumes (PbLi - manifolds, pipes, HTX) were
                                        scaled to the 300 kg/s (from the DCLL 26,000 kg/s) and all
                                        turbulent mass transport terms set to diffusion only
                                      • Extractor PbLi flow rate per column was set at 50 l/h
Schematic of TMAP Extractor Model     • ARIES-CS will require ~2430 parallel extractor column
                                        paths, and at an efficiency of ~25% will also need five
     PbLi flow
                                        stages per path (i.e., 12150 Melodie type extractors) – an
                                        occupational radiation exposure problem based in DCLL
  Packing        CT = Ks (PT2)1/2       TBM analyses
  Plate                               • The counter flow gas rate per column set at 100 Ncm3/min
                       CT2 = PT2/kT   • A film thickness of 0.2 mm was used to give an efficiency
                                        of ~25% per stage in this TMAP

                          Gas flow
  Tritium Inventory and Permeation Results For HCLL
                                     Ks-Reiter   100 x Ks-Reiter       FW
                                                                   Implantation   • An increase in solubility by 100
Tritium source                      ~400 g/d       ~400 g/d         ~910 g/d1
                                                                                    increases the PbLi inventory by
                                                                                    ~16 and increases HTX
Inventory                                                                           permeation, with the helium
   Structure1                         295 g          274 g            455 g         cleanup system now removing
                                                                                    a large fraction of the tritium
   PbLi                               60 g           864 g            60 g
                                                                                  • A tritium inventory of 0.9 kg for
Release2                            130 g/a3,4     95 g/a3,4        145 g/a3,4      high Ks case could represent a
Extractor overall efficiency          80%            3.6%             80%           radioactive release hazard for
                                                                                    ex-vessel PbLi spills
Tritium pressure
                                                                                  • Tritium airborne releases are
   PbLi                             2900 Pa          60 Pa          2925 Pa         above allowable
   Helium                             2 Pa           14 Pa           130 Pa
                                                                                  • When implantation is
                                                                                    considered, most of the
Tritium global balance                                                              implanted tritium remains in the
   Extraction columns                81.5%          55.5%             33%           helium cycles
                                                                                  195%   in of this inventory is in austenitic steel of
   Helium cleanup system              7.3%          30.0%             60%
                                                                                    extraction columns, and because there are
   Leaked                             9.2%           6.5%             7.0%          12,150 columns very little tritium is at risk in
                                                                                    most accidents
   Permeates to VV                    2.3%           8.0%              0%         299% ventilation flow cleanup is assumed
                                                                                  399% of this permeation is from extraction
Permeation into Rankine cycle                                                       columns
                                                                                  4Limit is < 1 g/a

   Intermediate helium cycle        2890 Ci/a6    5930 Ci/a6       12,060 Ci/a6   5Based on CANDU water concentration of ~1

                                                                                    Ci/kg (34,000 Ci/a allowed into Rankine cycle)
   Direct (required reduction)5/6     3.1x103       1.3x104          5.3x104      6Based on US PWR water concentration of ~ 1

                                     /3.1x105      /1.3x106         /5.3x106        mCi/kg (340 Ci/a allowed into Rankine cycle)
• Based on the present models, an increase in tritium solubility above that measured by Reiter would
  increase the tritium inventory in the PbLi, decrease extraction efficiencies, but could reduce the
  structural tritium inventory and permeation rates in DEMO reactors
• Most of the tritium in a DCLL concept will be in the PbLi/helium HTX tube walls, and because Nb is a
  getter accidents that result in HTX cooling will not release significant quantities of tritium
• For the HCLL concept, the majority of the tritium inventory and permeation is associated with the
  extractor columns, which could be reduced by a better design or selection of column materials. In
  addition, the HCLL has a much higher PbLi tritium inventory, making ex-vessel PbLi spills a tritium
  release concern
• Tritium permeation into a simulated Rankine power cycle was compared against equilibrium tritium
  concentrations in CANDU and US PWRs, it appears to be difficult to maintain an equilibrium
  concentration of 1 mCi/kg (PWR concentrations) by permeation barriers and/or material heat
  exchanger choice
• Regardless of the blanket concept employed, FW tritium implantation represents a significant
  problem for a Rankine cycle; a FW coating is need on the plasma side
• However, these result are based on the assumption that a sufficient understanding of tritium
  behavior in the PbLi, at PbLi/metal or PbLi/gaseous interfaces is presently known. Based on present
  experimental information this is clearly not the case
• What can be inferred from these results is that fusion reactors tritium inventories and permeation
  rates are highly dependent on this information, and thereby the ability to predict accidental and
  routine release of tritium from fusion reactors
                       Postscript On Melodie Results
                                             • Conservation of mass between phases:
Schematic of TMAP Extractor Model
                                                        C   H2
                                                             go    C g i2  Q l C lH  C lH
                                                                                  i      o
      PbLi flow
                                                   since C lH  C lH 1    C lH  C To  C lH
                                                            o      i              i     l        i

                                                                        2Q l
                                                   giving C g o2 
                                                                             C lH ; given that C g i2  0
  Packing          CH =   Ks (PH2)1/2                                   Qg       i

                          CH2 = PH2/kT       • Conservation of mass in liquid and diffusion:

                                                   A s D  C li  C lo        
                                                                                                         
                                                             H      H
                                                                       C lH   Q l C lH  C lH
                                                             2           s 
                                                                                         i      o

                              Gas flow
                                                   solving for C lH

                                                                      1 Q l 
• If the simple TMAP extractor model is             C lH  C lH 1         
                                                                       2 A D   K s kT Cg o

                                                                              
                                                       s      i
                                                                         s     
  correct, then data from Melodie can be
  used directly to determine if Reiter’s     • Substituting the above and solving for film thickness:
  solubility coefficient is reasonable for
  Melodie conditions, at least based on
                                                      As D  1       2kTQl                        1
  simple conservation equations                           1  K s                               
                                                      Ql            C lH Q g                     2
                                                                        i                          
                                                   where C lH  K s p sat2
                Postscript On Melodie Results (cont.)
                                                 • Given the other parameters of
 Schematic of TMAP Extractor Model                   T  673 K
       PbLi flow                                     D  2.0x10-9
                                                              l            5 m
                                                     Q l  50  1.39x10
   Packing         CH = Ks (PH2)1/2                          hr                s
                                                                     3                   3
   Plate                                                        Ncm                6 m
                                                     Q g  100          3.76x10           @ T  673 K
                         CH2 = PH2/kT                            min                   s

                                                   and using Melodie saturation pressures and
                            Gas flow               efficiencies gives:
                                                     PH2sat                         Ks-max      Ks-=0.15 mm
                                                     (Pa)                 (mm)   /Ks-Reiter    /Ks-Reiter
• Given the volume of the Melodie column              1100     0.31       0.149      1.37          0.998
  (V=2.26x10-3 m3), a packing fraction of 80%,
                                                       475     0.25       0.156      1.28          1.010
  and a packing area density of 750 m2/m3,
  the packing (film) surface area is ~ 1.4 m2          230     0.25       0.046      1.07          0.843

                                                   where, Ks-max is the largest solubility that still results in
                                                   a film for the TMAP extractor model, which is found by
                                                   setting the term in brackets in the film thickness
                                                   equation to zero => Reiter Ks fits Melodie results
              Schematic of ARIES-CS HCLL TMAP Model

   Poloidal      PbLi core    Shield   Manifolds
    Gaps                                                    PbLi/He HX                     Tritium cleanup

                                                                    823 K

First                                                               673 K
                                                                                 Brayton     boundary
Second                                               Columns

                                                   PbLi Pipes
 Rib walls
Radial                                                                                     Inter-cooler

                             Helium pipes
           Schematic of ARIES-CS DCLL TMAP Model
 Non-Hartmann    PbLi core    Shield   Manifolds
     Gaps                                                                          Tritium cleanup
                                                         PbLi/He Nb HX



  Rib walls                                                              Brayton

                             Concentric pipes                                      Inter-cooler

                             Helium pipes

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