ASTEC validation on PANDA tests A. BENTAIB, A. BLEYER Institut de Radioprotection et de Sûreté...

ASTEC validation

on PANDA tests

A. BENTAIB , A. BLEYERInstitut de Radioprotection et

de Sûreté NucléaireBP 17, 92262 Fontenay aux

Roses Cedex, FRANCE

B. ATANASOVAINRNE-BAS

Tzarigradsko shossee 72, 1784 Sofia, BULGARIA

Nesseber september 2010 2/26

Motivation

Conclusions & perspectives

Outline

PANDA T9, T9bis and T25 analysis


3 barriers between radioactive materials and

environment (« Defense in depth » principle) :

• Combustible clads

• Primary Circuit

• Containment

Volume : 50000 to 80000 m3 depending of the type

Length scale : some cm to several meters

Double concrete containment or simple concrete containment with liner (steel or composite)

H2 risk issues: Pressurized Water Reactors


Severe Accident:

A severe accident is characterized by a reactor core uncovery leading to

core degradation and Fission Products release into the containment

atmosphere (loss of the two first barriers)

H2 Risk Issues: Pressurized Water Reactors

Four main Phases :

• Loss of Fuel coolant phase in the primary circuit

• Core uncovery and core degradation phases

• Core melt-throughand reactor core vessel

failure

• Core concrete interaction and base mat

penetration


• the composition of the gaseous mixture inside the containment at each location and at each time (Distribution)

• the effect of the mitigation means as spray, catalytic recombiners (Mitigation)

• an estimation of the possible ignition of the gaseous mixture (Flammability limits)

• an evaluation the propensity of a premixed flame to propagate inside the containment (Flame acceleration criteria)

• the pressure and temperature loads due to combustion events inside the containment (Combustion)

Hydrogen Risk evaluation for PWR: Needs


IRSN/GRS cooperation since 1996 for development of an integral code for LWR (present/future PWR, BWR, VVER) source term severe accident (SA) calculation

Main objectives: o Applications to PSA2, including uncertainty analysis,o Accident management studies, o Investigations of NPP behaviour in SA cond., including source term

evaluation, o Support and interpretation of experiments,o Basis for a better understanding of SA physical phenomena.

Main requirements:o Comprehensive coverage of phenomena, account for their interactions.o "Reasonable" calculation time (fast-running code) < 12h CPU for one day

of accident simulated, o Accounting for safety systems and their availability (SAM),o High level of model validation,o Modularity, flexibility, user-friendliness, easy model incorporation.

=> ASTEC aim : becoming the european reference code for Severe Accidents

ASTEC : Accident Source Term Evaluation Code


TOSQAN (IRSN) ThAI (BT) MISTRA (CEA) PANDA (PSI)

Example of experimental programs in support of ASTEC validation

Addressed phenomena : Condensation, Gas and Thermal stratification , stratification break-up, Spray effect, Scaling effect

7 m3 60 m3 100 m3 480 m3


PANDA facility

SETH configuration :Dimensions : Height 8 m, diameter 3.957 m, volume about 180 m³Materials: Steel walls

instrumentation: more than 275 TC and 47 sampling points for MS measurements

Operated by Paul Scherrer Institute (Switzerland)


Experiments

Steam/gasvent

Steam/gas vent

Test 13 Test 14

Steam injection into DW1: DW1 and DW2 initially filled with air or steam/air mixture

DW1 DW2DW1 DW2

4 m

6 m

Steam/gasvent

Test 11

DW1 DW2

1.8 m

Steaminjection140 °C, 1 m/s

Init. cond. Air 108 °C 1.3 bar




Steam/gas vent

Test 10

DW1 DW2

1.8 m


Steam/gasvent

Tests 9, 16, 17

DW1 DW2

1.8 m

Steaminjection140 °C

Exitvelocity:

: 1 m/s: 3 m/s: 5 m/s

Test 9Test 16Test 17



Steam/gasvent

Test 9bis

DW1 DW2

1.8 m


Steam/gasvent

Test 12

DW1 DW24 m




Exitvelocity 1 m/s

Init. cond. Steam/ 50% Air 108 °C 1.3 bar

Steam/gasvent

Steam/gas vent

Test 13 Test 14

Steam injection into DW1: DW1 and DW2 initially filled with air or steam/air mixture

DW1 DW2DW1 DW2

4 m

6 m

Steam/gasvent

Test 11

DW1 DW2

1.8 m






Steam/gas vent

Test 10

DW1 DW2

1.8 m


Steam/gasvent

Tests 9, 16, 17

DW1 DW2

1.8 m


Exitvelocity:

: 1 m/s: 3 m/s: 5 m/s

Test 9Test 16Test 17



Steam/gasvent

Test 9bis

DW1 DW2

1.8 m


Steam/gasvent

Test 12

DW1 DW24 m




Exitvelocity 1 m/s

Init. cond. Steam/ 50% Air 108 °C 1.3 bar

Main addressed phenomena

- Steam and non-condensable gases mixing behavior- Thermal stratification phenomena- Characteristic of gas transportation between compartments- Steam condensation on the walls- Injection location effect


PANDA nodalizationnear wall injection configuration

2.15 m

0 m

1.47 m

0.81 m

2.85 m

3.31 m

3.78 m

4.65 m

5.3 m

6.47 m

8 m

DW1 DW2

A040

A114L

B040

B114L

A181L

A250L

A308L

A355L

A421L

A498L

A589L

A725

A589P

A498P

A421P

A355P

PIPE

A589R

A498R

A421R

A355R

A308R

A250R

A181R

A114R

B725P B725

B589P B589L B589R

B498P B498L B498R

B421L B421R

B355L B355R

B308L B308R

B250L B250R

B181L B181R

B114R

C355

C308

C355

C308

50 zones

10 vertical levels

Zones connected by

flowpaths with area

according geometry

Structures: heat exchange

with atmosphere,

condensation, heat capacity,

heat losses to environment


In the early phase the amount of steam is for both tests comparable over the Vessel 1 height

Test 9 and Test 9bis analysis

steam concentration profil

0

1

2

3

4

5

6

7

8

9

0,00E+00 1,00E+01 2,00E+01 3,00E+01 4,00E+01 5,00E+01 6,00E+01

steam concentration

hei

ght

(m)

Test9bis-1400s

test9bis-3400s

test9bis-5500s

test9-1400s

test9-3400s

test9-5500s

expT9b-1400s

expT9b-3400s

exp9b-5500s

expT9-1400s

expT9-3400s

expT9-5500s

Later on, due to the on-set of condensation in Test 9bis the steam concentration at the top of vessel increases faster in Test 9

Due to the evaporation of condensate water, steam concentration in lower becomes higher in test9bis


Test 9bis: steam concentration (DW1)

DW1

0,0

0,1

0,1

0,2

0,2

0,3

0,3

0,4

0,4

0,5

0,5

0 1000 2000 3000 4000 5000 6000

Time(s)

Ste

am

mass f

racti

on

Astec -0.53

Astec-7.48

Exp-7.48

Exp._0.53 m

Evolution of Gas temperature (top and bottom of DW1)

70

72

74

76

78

80

82

84

0 1000 2000 3000 4000 5000 6000 7000 8000 9000

time (s)

tem

pera

ture

(°C)

Exp.-DW1-7,48m

Exp.-DW1-1,076m

Astec-A114R

Astec-A725

the condensate water drained to the lower part of DW1 leads to a sharp decrease of gas temperature at 4000 seconds. Afterwards and due to the difference between gas and wall temperature, steam evaporation occurs and generates an increase of gas temperature and steam concentration in the bottom of DW1


Thermal stratification in DW1

Gas Temperature profile DW1 half radius

0

2

4

6

8

70,00 72,00 74,00 76,00 78,00 80,00 82,00 84,00 86,00 88,00 90,00

Temperature (°C)

Ele

vat

ion

(m

)

Exp.-1000s

Astec-1000s

Exp.-4000s

Astec-4000s

Exp.-7000s

Astec-7000s

Gas Temperature profile DW1 half radius

0

2

4

6

8

102 103 104 105 106 107 108 109 110 111 112 113

Temperature (°C)

Ele

vat

ion

(m

)

Exp.-1000s

Astec-1000s

Exp.-2000s

Astec-2000

Exp.-3000s

Astec-3000s

Exp.-7000s

Astec-7000s

Until 3000 s, the increase of gas temperature is comparable for both tests

For test 9bis and after 3000 s, steam condensation induces a strong heat transfer and an increase of wall and gas temperature


Thermal stratification in DW2


time evolution of steam concentration in IP

0,0

0,1

0,2

0,3

0,4

0,5

0 1000 2000 3000 4000 5000 6000 7000 8000

Time (s)

Ste

am

mo

lar

fracti

on

ASTEC-T9bis

Exp-T9bis

ASTEC-T9

Exp-T9

Steam transport in IP

steam is transported mainly in the top of the interconnecting pipe The on-set of condensation in Test 9bis determines similar observation as in Vessel 1


Steam transport to DW2

DW2

0,0

0,2

0,4

0,6

0,8

1,0

0 1000 2000 3000 4000 5000

Time (s)

Ste

am v

olu

me

frac

tio

n

Exp. z=0,538m

Exp. z=7.478m

Astec-(6,47m-8m)

Astec (0-0,81m)

Steam volume fraction:DW2

0,00E+00

1,00E-01

2,00E-01

3,00E-01

4,00E-01

5,00E-01

6,00E-01

0,00E+00 1,00E+03 2,00E+03 3,00E+03 4,00E+03 5,00E+03 6,00E+03 7,00E+03 8,00E+03 9,00E+03

time (s)

stea

m v

olum

e fr

acti

on

Astec-bottom

Astec-top

Exp-0.538m

Exp-7.748m

Sharp steam stratification is observed during the overall test period, between the regions above and under the interconnecting pipe height

The on-set of condensation in Test 9bis determines similar observation as in Vessel 1


Steam concentration at venting location

0,0

0,2

0,4

0,6

0,8

1,0

0 1000 2000 3000 4000 5000 6000 7000

time (s)

Ste

am v

olu

me

frac

tio

n

ASTEC-T9bis

Exp-T9bis

Astec-T9

Exp-T9

Steam at the venting locationUntil 3000 s, steam concentration at venting location is compared for both tests

After 3000 s, The on-set of condensation in Test 9bis determines similar observation as in Vessel 1, Vessel 2 and IP.


PANDA nodalizationcentral injection configuration

ww

53 zones with 12 vertical levels

Zones connected by flowpaths with area according

geometry

Structures: heat exchange with atmosphere,

condensation, heat capacity, heat losses to

environment


Predicted pressure, gas composition and temperature in the vent are in good agreement with data

Test 25 analysis : pressure time evolution


Test 25 analysis: 1st Phase (time <815s)


Test 25 analysis 1st Phase (2215<time <2815s)


Test 25 analysis 1st Phase (4415<time <7015s)


Test 25 analysis 2nd Phase (7415<time <14215s)


Conclusions

Results on gas temperature and gas concentration obtained with the ASTEC code for both tests T9, T9bis and Test25 are in good agreement with the experimental data:

gas mixing and stratification above and under the height of the DW interconnecting pipe have been well reproduced by the code.

the steam condensation effect on the thermal and the concentration front propagation in the two drywells and the interconnecting pipe have been well predicted by the calculation


Conclusions

The Astec validation process will continue by considering well instrumented experiments to check the effect of facility scaleand to prepare rules and recommendations to best use of LP codes for reactor applications


Thank you for your attention

ASTEC validation on PANDA tests A. BENTAIB, A. BLEYER Institut de Radioprotection et de Sûreté...

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