ITER Vacuum Vessel Supports Cadarache, 21 August – 7 September 2007

Andrea Capriccioli 22/08/2007 11.45 pag. 1 of 9

Vacuum Vessel Support – ongoing activity report n°1 New Electromagnetic Forces (22 August 2007) During the downward disruptions the max load per vertical support should be close to 40 MN

(Ioki; Wang; Capriccioli meeting on 23th of August): this value includes the dead weight and the

electromagnetic horizontal forces contribution.

On the basis of this total value (40 MN) it is roughly possible to estimate the electromagnetic

vertical force: for the downward disruptions the application point of the net horizontal force (73

MN) is not clear but if an application point 3 m upper the vertical supports it’s presumed and 90°

rotated (with respect to the vertical peak position), we obtain a vertical contribution of about 6.5

MN. This means that the component due to the vertical loads only results 40-6.5 = 33.5 MN.

If the same vertical amplification factor (1.1) and the peak factor (2) are applied, we obtain as first

approximation a Total vertical force (Tvf) equal to 176 MN (⇒ 90/9 + Tvf/9 *1.1 + 2 = 33.5 MN).

Downward Plasma Disruption With reference to the Neoprene material characteristics, it’s possible to consider the following values: Neoprene transient compression limit = 80 MPa (Ref. K. Ioki) = average static pressure = 20 MPa = max static pressure ≤ 40 MPa If φ=960 mm (Ref. X.Wang) is the external bearing pad diameter, the average pressure of 80 MPa

on neoprene is reached (net φ=800mm: the average pressure results = Max local 80 MPa during

transient with =1 safety factor).

In this case we have no safety margin but other possibilities can be analyzed:

VDE Downward Forces Vertical [MN) Horizontal [MN]

176* (from 72; ratio of ≈ 2.4) (* to be checked)

73 (from 25; ratio of 3)

Asymmetry peak= 2 MN Application point=3 m* (* to be defined)

Dynamic ampl.fact.= 1.1 Dynamic ampl.fact.=1.7

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the increase of the diameter from 0.8 m to 1 m: this means 36% lower pressure (see Fig1);

the use of load/stroke limiting devices to avoid neoprene damage; the use of metallic spherical joint, instead of neoprene;

the use of an upward “translated” bearing pad (see Fig.2).

Port

Bearing Pad

Pedestal Ring

1158 mm

1612 mm

Fig.1

Molybdenum Bisolfure

Fiberslip

BRONZAL (W7-X: AISI 316LN+Bronzal) INCONEL 718 (spec. ASTM B637 N07718)

ASTM-A 453

Ref. 960 mm

1800 mm

1300

mm

Fig.2

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While in the toroidal direction seems feasible to increase the bearing pad size from 960 up to 1700 or more (Fig.2), in the radial direction (Fig.3) the maximum neoprene diameter should be around 1200 mm. In every case, changing the neoprene diameter from 800 to 1200 mm induces an area increment of about 2.3 times and an average pressure less then 35 MPa (against the previous 80 MPa).

1158 mm

max 1400 mm

1200 mm

Fig.3

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Other open points:

• Bearing pad dimensions: lower ring (two small models show roughly the level of

stress in an example of ring). The sketch of the axial section is shown in Fig.4 and

the dimensions are set only for a preliminary analysis (see “Mageba Pot

Bearings.pdf” file as first reference)

• Vertical upward forces.

Upward Plasma Disruption

• Vertical ropes/rods/dumpers. • Radial restraint system. • Toroidal restraint system.

• Alternative solution with flexible plates as vertical (up/down) and toroidal restraint

systems.

Vertical Height ≤ 1300 mm; Toroidal Width = 960 mm; Radial Length ≤ 1400 mm.

VDE Upward Forces Vertical [MN) Horizontal [MN] __ (from 60) __ (from 25)

Asymmetry peak= 2 MN Application point=11 m

Dynamic ampl.fact.= 1.1 Dynamic ampl.fact.=1.7

Andrea Capriccioli 22/08/2007 11.45 pag. 5 of 9

Bearing Pad outer ring (half section): sketch and brief ANSYS analysis 2D analysis (ring with inner fillet 10 mm radius): Stresses in [MPa]; Displacements in [mm]

Fig.4 50

50

(D/1

5)

50

80

480[mm]

400

D=rubber diameter

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3D analysis (10 mm radius inner fillet)

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200

210

220

230

240

250

260

270

280

290

50 60 70 80 90 100 110 120 130 140 150 160 170 180 190

ring thickness [mm]

Max

loca

l von

Mis

es s

tres

s [M

Pa]

A brief parametric analysis to

evaluate the Max stress and

displacement, versus the ring

thickness [mm] was

performed.

After 150 mm it seems

useless to increase the ring

thichness (note: the rubber

diameter remains constat and

equal to 800 mm while the

external ring diameter

increases from 960 mm to 1320mm).

Top position ring Central position (pressure application zone) Some material properties and allowable:

AISI 316 LN Sy0.2=314 MPa (RT)

Su=540 MPa (RT)

Sm =176 MPa (RT)

Sm = 441 MPa (30 K)

ASTM-A 453 Sy0.2=589 MPa (RT)

Su=893 MPa (RT)

Sm = 295 MPa (RT)

Sm = 451 MPa (77 K)

INCONEL 718 Sy0.2=1010 MPa (RT)

Su=1246 MPa (RT)

Sm = 667 MPA (RT)

Sm = 863 MPA (77 K)

0.1

0.12

0.14

0.16

0.18

50 60 70 80 90 100 110 120 130 140 150 160 170 180 190

ring thickness [mm]

Max

radi

al d

isol

acem

ent [

mm

]

Andrea Capriccioli 22/08/2007 11.45 pag. 9 of 9

Ref.:80 mm ring thickness 100 mm

140 mm 180 mm