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Tritium-inventory-Shu

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									              Tritium retention buildup

 towards pulses in ITER PFCs and dust



    W.M. SHU, S. Ciattaglia and M. Glugla
             ITER Organization
Acknowledgement to ITER TF on Tritium inventory

                                                  1
    9th Hydrogen Workshop, Salamanca, June 2-3
                     New findings: two kinds of blisters
                    formed on W by low energy D plasma
Re-crystallized W; 38 eV, 1026 D/m2, around 500 K; W.M.Shu, Appl. Phys. Lett., 92, 211904 (2008).


                                                             fully-removed lids
                                                             by FIB fabrications
                          big blisters



                                                            partial-removed lids
        small blisters
                                                            by FIB observations




 Blistering occurs at W for energy                      For the small blisters, internal blister
 well below the displacement                            was a hole or pit, but the maximum
 threshold.                                             height against diameter reached 0.7,
 The lowest energy to produce                           which is one-order of magnitude
 Frenkel pair is 940 eV for D → W.                      greater than that reported before.
                                                                                                   2
           9th Hydrogen Workshop, Salamanca, June 2-3
                                New features of blisters
Re-crystallized W; 38 eV, 1026 D/m2, around 500 K; W.M.Shu, Appl. Phys. Lett., 92, 211904 (2008).

                                  cross-section
                                  of a blister


                                                                          cross-section
                                                                          of a blister



                                                                             crack/void along
                               crack/void along                              grain boundary
                               grain boundary

 For most cases of big blisters,                        By conventional definition, blisters are
 there was no hollow lid formed,                        plastic dome-shaped buildings where
 but a crack/void at the grain                          a lenticular cavity is included between
 boundary underneath the blister.                       the blister lid and the bulk material.
                                                                                                3
           9th Hydrogen Workshop, Salamanca, June 2-3
                       Various shapes of big blisters
Re-crystallized W; 38 eV, 1026 D/m2, around 500 K;   W.M.Shu, et al., PSI Conference.




                                          (a)                             (b)




                                          (c)                              (d)

                                                                                        4
        9th Hydrogen Workshop, Salamanca, June 2-3
                                                            Bursting release and retention ratio
                                                      Re-crystallized W; 38 eV, W.M.Shu,et                                                    al., PSI Conference.
                                          7
                                                                                                                                                   38 eV D plasma  W
                                                 1026 D/m2, 500 K
  Release rate (10 17 D2/m2/s)




                                          6                                                                                    22
                                                                                                                          10
                                          5




                                                                                              Deuterium retained (D/m )
                                                                                              2
                                          4

                                          3
                                                                                                                               21
                                          2                                                                               10
                                          1

                                          0
                                          300   400   500   600   700   800   900 1000 1100
                                                        Temperature (K)                                                        20
                                                                                                                          10
                                          16
              Release rate (10 D /m /s)
        2




                                          14
                                               2×1026 D/m2, 400 K
                                  2




                                          12
                                                                                                                                       = 1x10 D/m (TDS)
                                                                                                                                              26      2
        17




                                          10
                                                                                                                                       = 1x10 D/m (NRA, 0-7 m)
                                                                                                                                              26      2
                                                                                                                               19
                                          8                                                                               10
                                          6
                                          4
                                                                                                                                300     400               500   600       700   800
                                          2
                                          0
                                          300 400 500 600 700 800 900 1000
                                                                                                                                              Exposure temperature (K)
                                                      Temperature (K)

Busting release peaks were found There is a peak around 500 K. Retention
in the TDS curve, indicating     ratio at 775 K and 380-440 K is smaller
bursts of some blisters.         than 10-7 and 5×10-6, respectively.
                                                                                                                                                                                      5
                                               9th Hydrogen Workshop, Salamanca, June 2-3
                                                     In comparison with the data of
                                                       J. Roth et al. (ICFRM 2007)
                        W.M.Shu,et al., Nucl. Fusion 47 (2007) 201; Phys. Scr T128 (2007) 96.
                                    200 eV D ions, 300 K                                                             Fully-recrystallized W
                                                                                                                     Partially- recrystallized W
                             22                                                                VPS W
                        10




                                                                   %
D retained [atoms/m ]




                                                                                                                     Annealed W
2




                                                                   0
                                                                 10
                                                                                                                     Single W (111)

                             21
                                                                                                            38 eV D ions, 315 K
                        10
                                                                                               polycr. W


                             20
                        10


                             19
                        10
                                   19           20          21              22        23              24        25
                             10            10          10              10        10              10        10               1026      1027
                                                                                           2
                       Incident fluence [ions/m ]
Smaller retention ratio was found in the higher fluence region at lower energy.
                                                                                                                                                   6
                                  9th Hydrogen Workshop, Salamanca, June 2-3
                                     Calculation by J. Roth et al. (ICFRM 2007)
                                          number of 400s ITER discharges
                                          2,5E-4 0,0025    0,025  0,25                 2,5         25          250          2500
                                     27
                                  1x10
                                                                                                        C co-deposition
                                            700 g limit (1000 g (limit in VV)                           full ERO calcul.
                                     26
                                  1x10      – g T limit
                                           350120 g (in cryopump) – 180 g                               S=0
                                                                                                                                     750
                                                                                                        D/C=0.4
                                            (others))
        Retained amount (atoms)



                                                                                                                                     discharges
                                                                                                                      Be co-deposition
                                     25                            CFC implantation                                   DIVIMP calcul.
                                  1x10                                2     24   2
                                                                   3m , 1x10 /m s                                     D/Be=0.05
                                                                        2     23   2
                                                                   47m , 1x10 /m s
                                                                   750 K
                                     24
                                  1x10
                                           Total retention
                                                 2
                                           800m ITER mix
                                     23
                                  1x10


                                     22                                                       W implantation
                                  1x10                                                            2      20  2
                                                                                              100m , 1x10 /m s
                                           Be implantation
                                                2     20  2
                                           700m , 1x10 /m s
                                     21
                                  1x10
                                           0,1        1       10          100          1000      10000       100000        1000000
                                                                          Time (s)
In the calculation, the retention ratio in W was assumed to be around 10-3,
due to their higher energy (200 eV) and lower fluence (max. 1025 ions/m2).
                                                                                                                                                  7
       9th Hydrogen Workshop, Salamanca, June 2-3
                     Assumptions made in this calculation
1. Area, flux and temperature:
(1) Divertor (strike points): 3 m2, 1×1024 DT atoms/m2/s, 775 K
(2) Divertor (other target area except strike points): 47 m2, 1×1023 DT atoms/m2/s, 775 K
(3) Divertor (others): 100 m2, 1×1022 DT atoms/m2/s, 775 K (not considered in [1])
(4) First wall: 700 m2, 1×1020 DT atoms/m2/s, 380-440 K (750 m2 in [1])
2. Retention ratio (retention against fluence) in W PFCs:
(1) Divertor (at 775 K): 5×10-7 [2]
3. Constant retention in Be due to implantation: 7×1020 DT atoms/m2 [3]
4. Breading in Be first wall: Tritium inventory I (appm) = 280F - 2350[1 - exp(-0.1F)];
   [3]   where F(MWa/m2): neutron fluence.
5. Sputtering yield of Be first wall: 4×10-2 atoms/ions, half is dust [4]
6. Retention ratio of tritium in Be: 4×10-2 [4]
7. Producing rate of W dust (700 kg in 106 s): 2.3×1021 atoms/s [5]
8. Retention ratio in W dust: 1×10-6 [5]
[1] J. Roth, et al., “Tritium Inventory in ITER: Laboratory data,” presented at the 1st meeting of ITER DCR 131 (In
    Vacuum Vessel Tritium Control), Oct.16, 2007.
[2] W.M. Shu, et al., Fusion Eng. Des. (in press).
[3] R.A. Anderl, et al., J. Nucl. Mater. 273, 1 (1999).
[4] GSSR III
[5] W.M. Shu and S. Ciattaqlia, internal discussion.
                                                                                                                      8
             9th Hydrogen Workshop, Salamanca, June 2-3
                                  T inventory at case 1: full tungsten divertor
                                   Number of 400 s ITER discharge 2.5   25   250    2500 25000

                                   1026                                                          700 g limit
       Retained tritium (atoms)
                                     24
                                   10

                                   1022
                                     20
                                   10
                                                                        Total
                                                                        Be dust & codeposits
                                   1018                                 W divertor
                                                                        Be (implantation)
                                     16
                                   10                                   Be (transmutation)
                                                                        W dust
                                   1014
                                      10-1 100 101 102 103 104 105 106 107
                                                    Discharge time (s)
The main contribution is from the Be first wall initially, but Be dust will
be the controlling factor after 200 seconds.
                                                                                                               9
     9th Hydrogen Workshop, Salamanca, June 2-3
            Tritium retention at the case of large wall flux
The averaged tritium retention estimated is 0.056 g T/discharge.

In the calculation, averaged D-T flux at the first wall was assumed
to be 7×1022 DT atoms/s, the same as that used by Roth.

However, Philipps [1] argued that the most recent value of the
averaged D-T flux increased to 3-5×1023 DT atoms/s.

If the same assumptions are used, the averaged tritium
retention will increase to 0.24-0.4 g T/discharge for the case
of large wall flux.

[1] V. Philipps, “T–retention from present experiments and further validation,”
presented at the 4th meeting of ITER DCR 131 (In-Vacuum Vessel Tritium
Control), March 12, 2008.
                                                                                  10
         9th Hydrogen Workshop, Salamanca, June 2-3
                   Baking at 623 K to release major portion
                         of tritium in Be codeposits

                                                                        M.J. Baldwin, et al.,
                                                                        J. Nucl. Mater. 337-
                                                                        339, 590 (2005).




D/Be (a) and O/Be (b) ratios for deposited material collected on Ta (grey symbols), Mo (dotted
symbol) and W (white symbols) deposition probe coupons as a function of coupon temperature.
                                                                                                 11
          9th Hydrogen Workshop, Salamanca, June 2-3
          Tritium retention after baking at 623 K

Baking at 623 K of divertor after 1750-3000
discharges should be performed to release tritium
from the Be dust that is located around divertor
region.

The DT/Be ratio could decrease from 4×10-2 to less
than 10-2 after baking.

Thus, the averaged tritium retention finally will be
0.06-0.1 g T/discharge if baking is taken into
account.

                                                       12
    9th Hydrogen Workshop, Salamanca, June 2-3
                      Tritium buildup in the first 5
                            years’ operation

                                                        ~ 0.06 g T/discharge
                             1st D-T       2nd D-T   3rd D-T   4th D-T   5th D-T
                              year          year      year      year      year
     Equivalent
accumulated nominal             750         1750     3250      5750       8750
   burn pulses [1]
 Tritium inventory in          50 g         110 g    200 g     350 g      530 g
   Vacuum vessel


[1] Project Integration Document PID, Jan. 2007, ITER Organization, Editor: J. How.



                                                                                      13
        9th Hydrogen Workshop, Salamanca, June 2-3
                            Permeation of tritium in CuCrZr (castellation) at 623 K
                       1
                                                                                      Permeation flux:
Relative permeation



                      0.8                                                            =2pDLSP1/2/ln(dout/din)

                      0.6                                                            3.7×10-7 g-T/h
                                              Graph considers bulk                     for inner divertor;
                      0.4                     diffusion only, not                    5.7×10-7 g-T/h
                                              grain boundary                          for outer divertor;
                                              diffusion or leakage.
                      0.2                                                            9.4×10-7 g-T/h
                       0
                                                                                      in total.
                                          2           3               3          3
                        0          5x10          1x10        1.5x10       2x10       0.09 mg in 100 h.
                                               Time (s)
If the transport properties of hydrogen in CuCrZr are the
same as that in Cu, tritium permeation through CuCrZr pipes
without W armor will reach the steady state within one hour.
                                                                                                               14
                        9th Hydrogen Workshop, Salamanca, June 2-3
                                    Permeation of tritium in large SS pipes at 623 K
                                               Time (day)
                       1
                            0      4     8     12    16   20   24    28      32        Permeation flux
                                                                                       at steady state:
Relative permeation




                      0.8                                                             =2pDLSP1/2/ln(dout/din)
                                                                                        1.3×10-10 g-T/h
                      0.6
                                               Graph considers bulk
                                               diffusion only, not
                                                                                      In 100 hours’ baking:
                      0.4
                                               grain boundary                             7×10-10 g-T
                                               diffusion or leakage.
                      0.2
                                                                                            in total.
                       0
                                        5       6         6      6           6    6
                        0         5x10       1x10 1.5x10 2x10 2.5x10 3x10
                                                    Time (s)
      The steady state will be reached in more than one month, and
      tritium permeation will be negligibly small in 100 hours’ baking.
                                                                                                                15
                                9th Hydrogen Workshop, Salamanca, June 2-3
                                  Permeation of tritium in small SS pipes at 623 K
                                              Time (day)
                         1
                              0     0.2       0.4        0.6       0.8          1           Permeation flux
                                                                                            at steady state:
  Relative permeation




                        0.8                                                                =2pDLSP1/2/ln(dout/din)
                                                                                             2.8×10-10 g-T/h
                        0.6                    Graph considers bulk
                                               diffusion only, not                         In 100 hours’ baking:
                        0.4                    grain boundary
                                               diffusion or leakage.                           3×10-8 g-T
                        0.2                                                                     in total.
                         0
                                          4          4         4            4          5
                          0         2x10      4x10        6x10           8x10       1x10
                                                Time (s)
The steady state will be reached in one day, but tritium permeation
will be negligibly small in comparison with that of CuCrZr.
                                                                                                                     16
                          9th Hydrogen Workshop, Salamanca, June 2-3
                           T inventory at case 2: full tungsten PFCs

                                           Number of 400 s ITER discharges 2.5   25    250   2500
                                    1027
          Retained amount (atoms)                700 T limit
                                                350 g g limit
                                    1025
                                                                                                    350 days for
                                                                                                    continuous
                                    1023              W divertor                                    operation
                                                      W First wall
                                                      W dust
                                    1021


                                    1019


                                    1017
                                       10-1 100          101     102     103     104   105   106
                                                                Time (s)
W divertor is always the major component for T retention.
Tritium retention in continuous operation: 2 g /day (9 mg / discharge)
                                                                                                                   17
    9th Hydrogen Workshop, Salamanca, June 2-3
                    In comparison with that by J. Roth
                        for the case of Full W PFCs
                                          Number of 400 s ITER discharges 2.5   25    250   2500
                                   1027
         Retained amount (atoms)               350 g g limit
                                   1026         700 T limit
                                     25
                                   10

                                     24
                                                                      By J. Roth
                                   10

                                   1023

                                     22
                                   10                                           This work

                                   1021
                                      10-1 100          101     102     103     104   105   106
                                                               Time (s)
The retained amount calculated by this work is smaller than that by
Roth, because of the lower retention ratio in higher fluence region.
                                                                                                   18
   9th Hydrogen Workshop, Salamanca, June 2-3
                                          Summary
• In the case of full W divertor and Be first wall, tritium in Be
  dust (including codeposits) will be the controlling factor after
  200 s of discharge. The averaged tritium retention finally will be
  0.06-0.1 g T/discharge for the case of large wall flux if baking is
  taken into account.

• If baking at 623 K is performed, permeation through CuCrZr
  pipes located at castellation will be predominant. Considering
  bulk diffusion only, the total permeation will be 0.09 mg in 100
  hours’ baking.

• In the case of full W FPCs, the major contribution to the
  inventory is from the divertor, and the averaged tritium retention
  will be 9 mg/discharge (2 g/day for continuous operation).
• More accurate calculation should be performed by considering the effects of
  simultaneous H and He plasma on W blistering and dust producing.
                                                                                19
        9th Hydrogen Workshop, Salamanca, June 2-3
                                T inventory at case 3: CFC+W divertor
                                Number of 400 s ITER discharge 2.5     25      250   2500 25000

                                  27              700 g (~700 discharges)
                                10
    Tritium retention (atoms)
                                  25
                                10

                                  23
                                10

                                  21
                                10

                                  19
                                10                                   Total
                                                                     C codeposits
                                  17                                 Be dust & codeposits
                                10
                                                                     Be (implantation)
                                  15
                                                                     Be (transmutation)
                                10                                   W divertor
                                                                     W dust
                                  13
                                10     -1    0      1     2      3         4     5      6     7
                                     10     10   10     10    10      10       10    10     10
                                                          Time (s)
                                                                                                  20
9th Hydrogen Workshop, Salamanca, June 2-3
                   Some issues related to in-vessel
                     removal of T by oxidation
 Highly tritiated water processing  DCR-140
 Corrosion highly tritiated water is very corrosive even to stainless steel
    due to the radiochemical formation of peroxides and radicals
 Radiolysis and tritiated polymer formation  re-deposition and
    accumulation of tritiated polymers formed in the gas mixture of tritiated
    water vapour, tritium, CO and CO2 is unavoidable
 Oxidation of Be first wall  tritiated water moisture produced during
    oxidation may react with beryllium
 Wall conditioning  implications for after-oxidation wall conditioning to be
    evaluated
 Increased tritium retention in Be co-deposits  Oxidised Be codeposits
    are found to retain larger amount of T than pure Be codeposits
 Evaluation of safety related issues (such as dust-related) required to
    determine compatibility with ITER safety requirements

                                                                             21
      9th Hydrogen Workshop, Salamanca, June 2-3

								
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