ERMSAR 2012, Cologne March 21 – 23, 2012 Institut de Radioprotection et de Sûreté Nucléaire...

ERMSAR 2012, Cologne March 21 – 23, 2012

Institut de Radioprotection et de Sûreté Nucléaire (IRSN), Cadarache, FranceInstitute of Nuclear Technology and Energy Systems, (IKE) Stuttgart University, GermanyRoyal Institute of Technology (KTH), Stockholm, Sweden

Contact : [email protected], [email protected] [email protected]

Investigation of Multidimensional Effects during Debris Cooling

G. Repetto, T. Garcin (IRSN), M. Rashid *, R. Kulenovic (IKE), Weimin Ma, Liangxing Li (KTH)

* presenter


Experiments Parameters

POMECO KTH

DEBRIS IKE

PRELUDE IRSN

Reflooding From Bottom-Top and dry-out

Bottom- and Top-flooding, dry-out

Bottom-flooding

Temperature (K) Up to 775 Up to 800 Up to 1300

Pressure (MPa) 0.1 0.1 to 0.5 0,1

Water temperature (K)

293 (room temp) 40 to 120 (Subcooling)

293 (room temperature)

Water inlet velocity (m3/h/m2)

Gravity driven with downcomer

1 to 36 2, 5, 10, 20

Heating process Internal heaters Induction Induction

Power maintained during quench (0 to 300W/kg)

Geometry

Debris mass 1 : FL 2 : HT

1 2 3 4

5kg 24kg 57kg 58kg

Diameter/height (mm)

1 : Ø90/635

2 :200×200/620

1 : Ø125/640

2 : Ø150/640

1 : Ø110/100 2 : Ø180/200 3 : Ø170/500 4 : Ø290/250

Particle diameter (mm)

0.2 to 12 both multi-size spheres / irregular shape

3 to 6 + mixtures (2, 3, 6) and irregular shape

Stainless steel : 1, 2, 3, 4, 8 + mixtures + non homogeneous size

bypass by

pass

37kg, 60kg

Debris bed coolability plays an important role in the termination and stabilization of a severe accident. Towards the quantitative understanding of debris bed coolability, many experiments (IKE-IRSN-KTH) have been conducted to investigate two-phase flow and heat transfer in particle beds

Introduction

2

The table summarizes briefly, some conditions of those experiments related to coolability of debris beds: POMECO at Stockholm, DEBRIS at Stuttgart, PRELUDE at Cadarache.

ERMSAR 2012, Cologne March 21 – 23, 2012 3

POMECO-FL POMECO-HT

PRELUDE-HTDEBRIS

Reflooding Facilities

Water tank

Test section

Outlet steam line


Instrumentation : reflooding tests

170 mm

50mm

150 mm150 mm150 mm

Water injection

Overflow line

Water storage

tank(Bottom-Flooding)

Ceramic cylinderQuartz glass

External

Mid radius

Central

PRELUDE-HTDEBRIS

In PRELUDE, simultaneous measurements of steam flow rate, and pressure drop across the bed provide complementary data that allow “cross-checking” and contribute to improve our understanding of quenching of a particle bed

Thermocouples inside the debris bed, in different (axial and radial) locations allow a fine view of the different phases of the transient and are useful to follow the quench front propagation.


DEBRIS Experiments

Boiling / Dryout Experiments with down comer installation in the center of the bed

a) a) Closed down comer (top-flooding)

b) b) Open down comer (bottom-flooding / natural circulation)

c) c) Perforated down comer (lateral flow of water to the bed)

(a)(a) (b)(b) (c)(c)

ceramic balls

“debris”

water pool

down comer


Polydispersed particle bed, System pressure 1, 3 and 5 bar

- no qualitative effect on pressure drop behavior- no qualitative effect on pressure drop behavior

- higher vapor density and small change in latent heat- higher vapor density and small change in latent heat

- higher DHF increased coolability- higher DHF increased coolability

Lateral-flooding may lead to steam flow into the down comer

DEBRIS Experiments


DEBRIS Quenching Experiments

Polydispersed particle bed, bed height 640 mm

Top-flooding, initial maximum bed temperature 432 °C

Two distinct quenching phases realized


DEBRIS Quenching Experiments

Polydispersed particle bed, initial maximum bed temperature 631 °C

Water supplied to the bottom of the bed from an overlying water

tank at a height of ~ 950 mm

Near wall thermocouples indicate faster quench front progression

-75 0 75 -75 0 75 -75 0 75

Radius [mm]

Be

d H

eig

ht

[mm

]

Temperature °C


DEBRIS Experiments- Summary

Boiling and dryout experiments with water have been performed in

volumetrically heated debris bed varying the

- flow conditions (top- and bottom-flooding) and system pressures (1, 3 and 5 - flow conditions (top- and bottom-flooding) and system pressures (1, 3 and 5 bar)bar)

and measuring

- pressure gradient along bed height, temperature distribution and dryout heat - pressure gradient along bed height, temperature distribution and dryout heat fluxflux

Quenching experiments at different flow conditions (top- and bottom-flooding) and

initial superheating temperatures at ambient pressure

- quench time and the behaviour of quench front progression- quench time and the behaviour of quench front progression

Air / Water cold experiments

- single - and two - phase pressure drop measurements- single - and two - phase pressure drop measurements

9


Almost 1000°C during the reflooding phase

Those results qualified PRELUDE HT facility

Water velocity = 2 m/h at 870°C

0

200

400

600

800

1000

2600 2650 2700 2750 2800 2850 2900 2950 3000 3050 3100 3150 3200 3250 3300

Tem

pera

ture

(°C)

0

2

4

6

8

10

12

14

16

Steam

flow

rat

e (g/

s)

TN_0_87_348 (°C) TN_10_46_311 (°C) TN_10_6_314 (°C) TN_55_87_271 (°C) TN_55_6_273 (°C)TN_100_7_282 (°C) TN_100_46_281 (°C) TN_100_87_280 (°C) TN_155_6_366 (°C) TN_155_42_364 (°C)TN_155_87_365 (°C) TN_175A_5_207 (°C) TN_175B_46_226 (°C) TN_175A_46_317 (°C) TN_175B_5_344 (°C)TN_195_87_263 (°C) TN_195_46_269 (°C) TN_195_5_270 (°C) Debit Vapeur (g/ s)

Test 111 : Reflooding at 900°C , P = 300 w/kg - 2mm particles - Q = 2 m/h

This test corresponds to the worst thermal hydraulics conditions for the outlet steam line :

- HT for the debris ( 860-990°C)

- High power deposition (300 W/kg)

- Low flow rate (2 m/h)

First example : B2 mm

Results PRELUDE HT (1/5)

10

The PRELUDE facility, in operation since mid of 2009, has been modified in 2011 to increase the performance regarding the power deposition and the initial temperature of the debris bed up to 1000°C.


with higher water velocily = 5 m/h at 900°C

Second example : B4 mm

0

100

200

300

400

500

600

700

800

900

1000

2750 2775 2800 2825 2850 2875 2900 2925 2950 2975 3000 3025 3050 3075 3100

Time (s)

Tem

per

ature

(°C)

0

5

10

15

20

25

30

35

40

45

50

Wat

er a

nd s

team

flow

rat

e (g

/s)

TN_0_0_322 (°C) TN_10_85_325 (°C) TN_10_40_324 (°C) TN_10_0_323 (°C) TN_45_85_328 (°C)TN_45_0_326 (°C) TN_45_40_327 (°C) TN_100_0_329 (°C) TN_100_40_330 (°C) TN_100_85_331 (°C)TN_155_45_392 (°C) TN_155_0_332 (°C) TN_175_85_390 (°C) TN_175_40_338 (°C) TN_155_85_399 (°C)TN_175_0_391 (°C) TN_195_0_393 (°C) TN_195_40_400 (°C) debit Corriolis (g/ s) Debit Vapeur (g/ s)

0 mm45 mm 100 mm 155 mm 195 mm

250 s

175 mm

220 s

0

5

10

15

20

25

30

35

40

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300

Stea

m F

low

rat

e (g

)

0

500

1000

1500

2000

2500

3000

3500

4000

Stea

m P

roduct

ion (g)

Debit Vapeur (g/ s) E126 Debit vap. (g/ s) essai 80 Cumul vap. Essai 80 Cumul Vapeur (g) E126

Test 126 : 900°C

Test 80 : 700°C


11

While the general behavior of the reflooding is not strongly changed by the increase of temperature, the experiment performed at 900°C has shown the highest water/steam conversion factor never reached up to now (> 90%), even more that was foreseen by the pre-calculation.

Higher peak steam flow rate in the short term and reflooding longer in long term (more important stored energy) with a higher total steam production


y = 0,9405x - 2656

y = 1,6846x - 4761,6

y = 1,0985x - 3099,5

0

20

40

60

80

100

120

140

160

180

200

220

2800 2850 2900 2950 3000 3050

Quenching time (s)

Leve

l (m

m)

Central location

Liquid from pressure

Mid radius location

External location

Reflooding duration : 220 s

Quench Front Velocity : 5,6 m/ h




12

Illustration of the quench front propagation (timing for quenching identified when thermocouples reached the saturation conditions). The existence of a quasi steady propagation of the quench front is verified for most of the tests. The faster quench front velocity in the periphery versus the centre outlines the 2D behaviour of the reflooding process.

Comparaison with DEBRIS tests regarding the Quench front propagation


0

100

200

300

400

500

600

700

800

900

1000

1950 2000 2050 2100 2150 2200 2250 2300 2350 2400

Tem

pera

ture

(°C)

0

5

10

15

20

25

30

35

40

Wat

er/s

team

flow

rat

e (g

/s)

0 mm55 mm 100 mm

155 mm 195 mm175 mm

Water flow rate

0 2 m/h 5 m/h 10 m/h 20 m/h 50 m/h

900

800

700

600

500

400

300

200

100

Billes de Ø2 mm

Test 90Test 93Test 94

Test 95

Test 87Test 88

Test 91 Test 92Test 96

Test 89

Test 107

Test 108 Test 109

Test 113

Test 118

Test 112

Test 110

Test 111

Test 114

Test 115

Test 117

Test 116FLUIDISATION Tests 2011 :

12Tests 2010 : 10

Test 117

The impact of the bypass which could change T/H conditions for the fluidisation will be studied in the beginning of 2012, using a larger PRELUDE test section

Nevertheless, those results give preliminary information of their impacts on the PEARL tests matrix

The fluidisation domain has been estimated for various particles size : B4, B2 et B1 as function of the thermal hydraulics conditions (T, Q)

22 tests with Ø2mm diameter


13

When the steam produced during the reflooding create drag force higher to gravitational force of the debris, fluidisation phenomenon could occure and was observed in PRELUDE experiments


0

5

10

15

20

25

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 360 380 400 420 440

Time (s)

Stea

m fl

ow r

ate

(g/s

)

0

500

1000

1500

2000

2500

3000

3500

4000

Stea

m P

rodu

ctio

n (g)

Test 107 Test 108 Test 116 Test 114 Test 115 Test 117

850°C/190 W/kg

850°C/300 w/kg

750°C/190 W/kg

750°C/190 W/kg

900°C/0 w/kg

420°C/190 W/kg

0

2

4

6

8

10

12

14

16

0 30 60 90 120 150 180 210 240 270 300 330 360 390 420 450 480 510 540 570 600 630 660

Time (s)

Stea

m fl

ow r

ate

(g)

0

500

1000

1500

2000

2500

3000

3500

4000

Stea

m P

rodu

ctio

n (g)

Test 91 Test 112 Test 109 Test 110 Test 111

850°C/300 w/kg

750°C/190 W/kg

720°C/190 W/kg

420°C/70 W/kg

850°C/190 W/kg

with injection flow rate 2 m/h with injection flow rate 5 m/h

Effect of temperature and power deposition


14

The effect of the initial debris temperature has shown an impact on the peak of the steam flow rate during the first stage of the reflooding whereas the(specific power maintained during the transient) has a stronger impact during the second stage of the reflooding and consequently on the duration of the complete quenching of the debris bed , which is in agreement with the more important stored energy


While the general behavior of the reflooding is not strongly changed, the High

Temperature Tests in PRELUDE HT, up to 900°C, outlined very high

water/steam conversion factor during the first stage of the Reflooding

The impact of the power deposition, which simulated the residual neutron

power has a stronger impact during the end of the transient

Simultaneous measurements of steam flow rate, temperature evolution and

pressure drop across the bed provide complementary data that allow “cross-

checking” and contribute to improve our understanding of quenching of a

particle bed with bottom cooling injection

Regarding Fluidisation, the open questions are the probability to occur in the

Reactor case, according to the thermal hydraulics in the partially degraded

core, the heat transfers which could increase the efficiency of the Reflooding.

Conclusion in PRELUDE

15


Objective: To study the friction laws and dryout heat flux of particulate

beds packed with non-spherical particles

16

Bed Particles Facility Bed shape ε Test Focus

1

Cylinders:

3 x 3 / mm

(diameter x length)

POMECO-FL

Cylindrical:

90 x 635 / mm

(diameter x length)

0.34 Single-phase flow Effective diameter

2

Cylinders:

3 x 3 / mm

(diameter x length)

POMECO-HT

Cuboidal:

200 x 200 x 620 /mm

(L x W x H)

0.34

Two-phase flow:

top-flooding

&bottom fed

Dryout heat flux

POMECO Experiments


mmdd sdeq 6.2

mmSA

Vd

vp

psd 3

66

1–Hu & Theofaneous model

2–Schulenberg & Műller model

3–Reed model 4–Lipinski model

1–Lipinski model

2–Reed model

POMECO-FL POMECO-HT

Single phase flow test Top flooding test Bottom fed tests

Results POMECO

17


The tests on the POMECO-FL facility show that for a particulate bed packed

with non-spherical particles such as cylinders, the effective particle diameter

can be represented by the equivalent diameter of the particles, which is the

product of Sauter mean diameter and the shape factor.

Given the diameter obtained from the test on POMECO-FL facility, the dry-out

heat flux obtained in POMECO-HT test is well predicted by the Reed’s model

for a top-flooding bed.

The bottom injection improves the dry-out heat flux significantly and the

prediction of the Reed model is more conservative with increasing flow rate of

the bottom injection.

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Conclusion in POMECO


Future Work

19

2D quenching experiments with down comer installation in the center of the

bed

The PRELUDE results will be extended in 2012 with reflooding experiments of

heterogeneous porous media (mixture of particles of different diameter, non

spherical particles) in the larger test section (PRELUDE 2D including a

bypass) and different mode of water injection to prepare PEARL experiments,

in a the largest Debris Bed and very challenging configuration never

performed up to now

Benchmark reflooding experiments at IKE-DEBRIS and IRSN-PRELUDE

Investigation of friction laws with Air / Water cold experiments at IKE-DEBRIS


• The European Research Project on Severe Accidents SARNET: Severe Accident Research NETwork of Excellence)

Acknowledgement:

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Thank you for your attention

ERMSAR 2012, Cologne March 21 – 23, 2012 Institut de Radioprotection et de Sûreté Nucléaire...

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