2. Material alternatives to limit activation of ZS
J. Borburgh
With valuable input from: C. Theis, H. Vincke, W. Weterings
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3. Actual ZS
Tank: 3.2m x Ø0.6m tank made of stainless steel 304L, 6 mm thick sheet.
Anode support: 3.1m x 200 x 94 mm C-shaped support made of Invar or stainless steel.
Accessories and
supports neglected
for the time being.
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4. Alternative materials mechanical components
Low-Z materials could be selected for the vacuum vessel, or even anode support.
J-Parc built a Ti vacuum vessel, anode support and endplates to reduce residual radioactivity [11]
LEP used Al vacuum chambers
PS SEH uses Al anode supports
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5. Alternatives considered
Tank
Stainless steel: dimensions as present
Aluminium: 67% thicker material (10 mm tank body, 50 mm covers)
Titanium: 33% thinner material (4 mm tank body, 25 mm covers)
Anode (dimensions identical for all cases)
Stainless steel
Invar
Titanium
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6. Material properties used
Inox 304
Al (6061)
Ti-A6-V
Invar
Young’s modulus [GPa]
200 69
120
148
Yield strength [MPa]
760
483
Density [Mg/m3]
7.85
2.7
4.43
8.05
Thermal expansion [1e-6/K] 17 23 9
1.5
Global Radiation risk at 400 GeV/c (operation)*
1.6
0.27
0.94
2.13
Global Radiation risk at 400 GeV/c (waste)*
0.83
0.35
1.16
0.81
*Activation occurring at 10 cm lateral distance to the target.
Source: Actiwiz web catalogue
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7. Modelling
Tank
Anode
Weight [kg]
Volume [dm3]
Stainless steel
367 47
239 30
Aluminium
211 78
n.c.
n.c
Titanium
146 33
135
Invar
245
ZS tank
anode
Case 1: Activation occurring at the beam impact area
Case 2: Activation occurring at 10 cm lateral distance to the target
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8. Radiation hazard results
Influence of the irradiation case on the results
Global hazard results vs. 1 and 20 yrs operation results
Optimal material choice
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9. Radiological hazard factors
To establish the radiological hazard factors the following approach was used:
Operational hazard factor: the volume of each topology (tank volume) is multiplied by the compound risk factor.
Waste hazard calculation: a normalised hazard factor is calculated based on the weight of the anode and the tank ratio.
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10. Influence of the irradiation case on the results
Although absolute values differ between the 2 cases, comparison of topologies within each case provide coherent indications of activation.
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11. Global hazard factor vs. 1 year and 20 yrs of operation
Global hazard factor correlates well with cases of 20 yrs of operation.
For 1 yr operation and in particular for titanium some small differences are visible.
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12. Activation in operation
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13. Global radiation hazard
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14. Aluminium alloys for tank
easy to machine, easily weldable, most commonly used general-purpose alloy,
compatible with vacuum applications,
Al 6000 series looses strength when heated up: not recommended for bake-able tank.
Al 2219
Strong, alloyed with copper,
More difficult to weld than other Al alloys,
Susceptible to stress corrosion cracking, increasingly replaced by 7000 series (alloyed with zinc),
Can be used for bake-able application.
Al 5083
Strong, alloyed with magnesium,
More difficult to weld than Al 6061,
5083 retains strength after welding. It has the highest strength of the non-heat treatable alloys, but is not recommended for use in temperatures in excess of 65°C.
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15. Conclusions (1/2)
The 2 different load cases in Actiwiz provide coherent results.
The results after 1 yr and 20 yrs of operation are coherent with the global hazard assumptions in general.
Changing the anode to Titanium is favourable, but:
it is still unclear if the (thermal) stability is sufficient for using it for positions ZS1, 2 and 3 instead of Invar.
Ti appears a valid candidate for ZS4 and 5 anodes.
For the tank material, aluminium appears preferable over titanium, but:
Bi-metal CF flanges (stainless steel/ aluminium) are commercially available,
Conflat (CF) flanges made of Aluminium are being developed by TE/VSC,
Larger flange diameters or aluminium flanges to replace ‘Suchet’ or ‘Wheeler’ flanges will have to be developed.
Titanium tank dimensions are based on stress levels, but buckling is not yet considered; this may necessitate a thicker tank, or more reinforcements, leading to less favourable hazard factors.
Impact of smaller components is neglected in the evaluation for the time being.
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16. Conclusions (2/2) Anode Titanium anode is readily feasible.
Its cost limited to manufacturing and assembly.
Can be considered for ZS3 and ZS5, possibly ZS2.
Tank
R&D is needed for an aluminium vacuum tank flanges.
This will require a new tank design, as well as manufacturing and thorough testing.
Not certain if the vacuum vessel can be made bake-able.
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17. Back up slides
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18. Tank body (SPS_ )
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19. Anode support (SPS_ )
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20. Wire tensioning spring (SPS_8032050579)
Influence of springs not taken into account yet.
3000 springs per tank, 128 mm long, Ø1 mm,
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21. Vacuum flanges for Al alloy vacuum chambers
TE/VSC have tested successfully CF flanges (up to CF100) made of Al-Li alloy. They use aluminium CF-type seals and proved to be bake-able (repeatedly) to 230⁰C.
These Al-Li CF flanges are stir welded (by Sominex) to 5083 Al alloy tubes, which are butt welded to vacuum chambers of the same material.
Bi-metal flanges proved prone to leaking, in particular when they have to be baked.
Bimetal flanges (Al or Ti + Stainless steel) are commercially available from Atlas.
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