Status of accident analysis for HCPB

Forschungszentrum Karlsruhein der Helmholtz-Gemeinschaft

X. Jin & L.V. Boccaccini slide # 1

PL FUSION FZK - EURATOM ASSOCIATIONInstitut für Reaktorsicherheit

Status of accident analysis for HCPB

X. Jin, L.V. Boccaccini, R. Meyder

Garching, 9th Oct. 2006

Meeting on Safety assessment for EU TBM




PIE

HCS + CPS

TES

Pla

sma

Cha

mbe

r

Port Cell

TCWS vault

T Building

1. A double-ended pipe break in the TBM cooling loop in a large diameter pipe (ID=100mm) of the primary loop discharging coolant in the TCWS vault during plasma burn.

2. The coolant inventory is lost and the heat removal capability of the HCS goes to zero in short time.




Ex-vessel LOCA using RELAP5 MOD3.2

Double-ended pipe break in the TBM cooling loop in a large diameter pipe (DN100, Di=98.3mm, Da=114.3mm) during plasma burn (270KW/m²).

Recuperator

HX

Dust FilterCirculator

TB

M

8MPa

35°C

V3

T

T

V5

TB

M-B

ypas

s

Rec

-Byp

ass

50°C

500°C

300°C

V4

Heater II

E

T

V2

Heater I

E

Modeling gas compressor in RELAP5

V6

V7

PV He18MPa, 35°C

vlve702 Circ-Bypass

He0.1MPa, 20°C

vlve606

snglvol705

tmdpvol607

7.9MPa

p

Valve cross section:Vlve606 pipe break: 0.015178m² (=2*pipe area)Pressure vessel (PV) vlve 702: 0.0002513m²




Pressure results for ex-vessel LOCA

0.E+00

1.E+06

2.E+06

3.E+06

4.E+06

5.E+06

6.E+06

7.E+06

8.E+06

0 2 4 6 8 10 12 14 16 18 20

Time (s)

Pre

ssur

e (P

a)TBM inlet

• time constant 1.05s (p=2.96MPa)• at 2.4s p< 1MPa• at 10s p 0 (time for ramp of HTC in the next calculation)




Heat up of the FW (and TBM)

HCS + CPS

TES

Port Cell

TCWS vault

T BuildingHo

t sp

ot

500K

W/m

² 27

0KW

/m

²




Break of the FW

HCS + CPS

TES

Pla

sma

Cha

mbe

r Port Cell

TCWS vault

T Building




Case A

3. A trigger system able to shut down the plasma in 100s is assumed and doesn’t fail.

4. In this case, only the failure of the FW channels (now filled with a mixture of He/air at about 0.1 MPa) is considered as following failure; it opens a by pass from the TCWS to the VV with air penetration in VV. Be/air reaction at the FW surface occurs.

5. A loss of off-site power occurs, which is equivalent to a loss of heat sink in the TBM cooling system; it also means that the VV cooling system is in the natural convection mode.

6. After differential pressure inversion the gases (air, He) in the VV and in TBM flow towards outside through the TBM cooling loop bypass and tritium and dust can be transported from the gas stream and released in the external zones.




TBM-Model for study of temperature (air oxidation)Cut from EM_TBM (pol*tor*rad=740*1270*750)

Boundary conditions:• Surface heat flux 500/270KW/m²• FW cooling 330°C, 5000W/m²K• Cooling plate 450°C, 3000W/m²K• Radial power distribution• Radiation MF back side to 135°C• Radiation after plasma off from Be-

cover to blanket FW surface temperature*

• Radiation from BU back plate to MF3• Be reaction rate**• After heating power factor

* FIGURE VII.3.3.1-5 G84RI601-07-10 R1.0** G81RI1003-08-08W0.1




Case A/3,4,5

heat flux(KW/m²)

500

time

a (W/m²K)

5000

FW

0

0

I II III

I: initial position at steady state (4000s).II: loss of coolant in case of ex vessel LOCA, blow down within 10s (alfa=0, II-I=10s). III: plasma off, when Be melting point at 1290°C is reached (III-I=100s).IV: decay heating (IV-III=24h).

IV

Be+1/2O2 = BeO -610KJ/mol

4000s 10s100s

24h

(Other possibilities tbd)




Case A 100s delay (500KW/m²)

Be-cover

surfacePla

sm

a s

ide

interface

FW2 FW3 FW4 FW5 FW6

0 90 180 270 360 450Time (s)

Tem

per

atu

re (

°C)

1290

1057

824

591

358

125

100s

760




Case B

3. The detection of the ex-vessel LOCA fails to trigger the Fusion Power Shutdown System (FPSS); the plasma reaction runs until the beryllium cover of the first wall reaches 1290 °C. This is the melting temperature of beryllium and leads to inherent plasma shut down.

4. In this case it is assumed a complete failure of the FW integrity with penetration of air in the VV.

5. In addition it is assumed that a major plasma disruption is triggered by the entering air but without failure of water confinement in the shielding blanket or divertor system.

6. A loss of off-site power coincides with the disruption, which is equivalent to a loss of heat sink in the TBM cooling system; it also means that the VV cooling system is in the natural convection mode.

7. Box structures containing lithium orthosilicate and beryllium pebbles can loose their integrity. This means that air can enter the TBM box reacting with the Be pebbles.

8. After differential pressure inversion the gases (air, He) in the VV and in TBM flow towards outside through the TBM cooling loop bypass and tritium and dust can be transported from the gas stream and released in the external zones.




Case B/3,4,5,6,7

heat flux(KW/m²)

270

time

a (W/m²K)

5000

FW

0

0

I II III

I: initial position at steady state (4000s).II: loss of coolant in case of ex vessel LOCA, blow down within 10s (alfa=0, II-I=10s). III: plasma off, when Be melting point at 1290°C is reached (III-I=212s).IV: decay heating (IV-III=24h).

IV

Be+1/2O2 = BeO -610KJ/mol

4000s 10s212s

24h




Case B 212s delay to Be melting point (270Kw/m²)

Be-cover

surfacePla

sm

a s

ide

interface

FW2 FW3 FW4 FW5 FW6

0 90 180 270 360 450Time (s)

Tem

per

atu

re (

°C)

1290

1057

824

591

358

125

212s

896




Case B/7 0.1MPa air in pebble bed (“unrestricted air access” model)

Pebble bed temperatures, 24h after plasma offPebble bed temperatures, enlarged

Tem

per

atu

re (

°C)

980

856

732

608

484

360

0 4.8 9.6 14.4 19.2 24Time (h)

0 170 340 510 680 850Time (s)

1290

1090

890

690

490

290

Tem

per

atu

re (

°C)




Case C

5. In addition it is assumed that a major plasma disruption is triggered by the entering air with failure of water confinement in the shielding blanket or divertor system.

6. A loss of off-site power coincides with the disruption, which is equivalent to a loss of heat sink in the TBM cooling system; it also means that the VV cooling system is in the natural convection mode.

7. Box structures containing lithium orthosilicate and beryllium pebbles can loose their integrity. This means that a mixture of air/steam (tbd) can enter the TBM box reacting with the Be pebbles.

8. After differential pressure inversion the gases (air, steam) in the VV and in TBM flow towards outside through the TBM cooling loop bypass and tritium and dust can be transported from the gas stream and released in the external zones.




Case C Be/steam, assumption for ANSYS calculation

Be+H2O->BeO+H2-370KJ/mol

heat flux (KW/m²)

270

time

a (W/m²K)

5000

FW

0

0

I II III IV

4000s 1s10s

5h/96h

TBM pebble bed 0.2m³

Porosity por=0.67

steam diffuses into TBM pebble

bedpmax=60KPa, in=0.005mol/s

N mH2

Steam pressure in pebble bed p=nRT/[0.2*(1-por)], R=8.314J/molK

I: initial position at steady state (4000s).II: loss of coolant in case of ex vessel LOCA, plasma off within 1s (II-I=1s).III: blow down within 10s (alfa=0, III-I=10s). IV: decay heating (IV-II=96h).




Case C Be/steam reaction

172g H2 generated after 5h, extrapolation to 1day 825.6g H2, 4days 3.3Kg H2 (tbd).

H2 generation in pebble bed (steam)

0

20

40

60

80

100

120

140

160

180

0 1 2 3 4 5

Time (h)

H2

(g)

H2 generation at FW (steam)

0.00

0.05

0.10

0.15

0.20

0.25

0 1 2 3 4 5

Time (h)

H2

(g)

0.236g H2 generated after 5h, extrapolation to 1day 1.133g H2, 4days 4.53g H2 (tbd).




tbd

• Case A/3

ramp of power for plasma shut down in 100s?

• Case A/6, B/8

After differential pressure inversion the gases (air, He) in the VV and in TBM flow towards outside through the TBM cooling loop bypass and tritium and dust can be transported from the gas stream and released in the external zones.

• Case B/3

reference temperature uses EUROFER melting point instead of Be melting point?

• Case C/7-8

Box structures containing lithium orthosilicate and beryllium pebbles can loose their integrity. This means that a mixture of air/steam (tbd) can enter the TBM box reacting with the Be pebbles.

After differential pressure inversion the gases (air, steam) in the VV and in TBM flow towards outside through the TBM cooling loop bypass and tritium and dust can be transported from the gas stream and released in the external zones.

Documents

Status of accident analysis for HCPB