Accident analyses for the Cryostat- building interface components

Accident analyses for the Cryostat- building interface components

Emili Martinez

emili.martinez@idom.com

Imanol Zamora

imanol.zamora@idom.com

• ^Background

• Specifications

• Model development and nodalization

• Case definition

• ^Simulation

Index

This task has been funded by F4E under the contract F4E-0578-01

Background

• ITER Cryostat is a metallic structure that maintains a technical vacuum.

• The Cryostat is attached to the building by means of the bellow flanges

• This bellow flanges are air-tight

and may be under heavy thermal

stress in some tokamak events

Specifications

• The mechanical performance of the bellow flanges may be compromised due to thermal stress

• The performance is modelized using a FEM model, but detailed

boundary conditions are needed for event calculations

Specifications

• To get detailed BC, the MELCOR model of the ITER building, including the tokamak had to be done

• Latest modifications and safety features of the building and tokamak had to be implemented

• Simulation of different scenarios

◦ ^{ICE III}

◦ ICE IV

◦ LOCA III

◦ ^HLG

◦ Fire in PC

Model developement

• The model aim is to simulate thermal and pressure transients due to accidental scenarios.

• No RN models needed for this task

• Had to implement several overpressure devices for cryostat and building protection

• New building nodalization developed to include all the involved

volumes and flow paths.

Model developement

• The bellow flanges heat transfer have a important role defining the volumes temperature

• They are thin structures with vacuum inside

• An equivalent thermal conductivity had to be calculated and applied

to a made-up material for each bellow.

Model developement

• Radiation heat transfer had to be linearized

• Although there are different regions in a bellow, it was modeled as a single HS

steel rad steel

steel air steel

T ₁ T ₂

steel rad steel

steel air steel

T ₁ T ₂

T ₃ T ₄

T _CSR T _PCI

Nodalization

Credit © ITER Organization, http://www.iter.org/

Nodalization

Basement gall.

CV140 Div. Gall

CV141 Eq. Gall.

CV 142 Upper gall.

CV143 Cryo dist. Gall.

CV139

TCWS vault CV133

Pipe chase

and shafts CV134 VVPSS gall.

CV138

Port Cell CV153

Env Non filtered

CV146

Env HVAC filtered

CV144

201

221 222 223 224

225

CSR-L CV202

226

303 200

204 205

215

211

216 218

CSR-H CV201

227

Interspace

CV203 206

208

209

210

Nodalization

Basement gall.

CV140 Div. Gall

CV141 Eq. Gall.

CV 142 Upper gall.

CV143 Cryo dist. Gall.

CV139

TCWS vault CV133

Pipe chase

and shafts CV134 VVPSS gall.

CV138

Env HVAC filtered

CV144

CSR-L CV202 CSR-H CV201

HVAC impulsion CV149 (22ºC)

261

259

251

253

255

257

250

252

254

256

260 258

S_DS CV145 Port Cell

CV 153

N-VDS CV 147 207

Nodalization

Nodalization

HS 172

HS 140

H S9 92 H S9 92

CV996

HS 951

HS 951

H S 17 0

HS CV201 171

CV201

CV 203

HS 142 HS 141

CV 153 HS

H S 95 2 173

HS 941 HS 729

HS 941 HS 729

H S 72 4

Case definition

• ICE III: 2600 Kg of cryogenic He in the cryostat

◦ Mass source of NCG

• ICE IV: 4000 Kg of cryogenic He in the cryostat

◦ Mass source of NCG

• LOCA III: 98000 kg of water at 513K in PC

◦ Simulation as mass and energy source. Pipe system is not explicitly modeled in this task

• HLG: 2600 kg of cryogenic He in the building

◦ Mass source of NCG

• Fire in PC: 4500 kW for 2h

◦ Simulated as mass and energy source

Case simulation: ICE III

Case simulation: ICE III

Case simulation: ICE IV

Case simulation: ICE IV

Case simulation: LOCA

• Overpressure due to very conservative leak definition (much more flow than in AAR)

• Leak conditions defined in time independent volumen,

imposing flow rate

Case simulation: LOCA

Case simulation: HLG

Case simulation: HLG

Case simulation: Fire

• Very conservative fire power and duration

• A lot of numerical instabilities,

very dependent on walls BC

Case simulation: Fire

Thank you!

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