ermsar 2012, cologne march 21 – 23, 2012 paper 3.3: revaporisation - bottomley et. al. a study of...

ERMSAR 2012, Cologne March 21 – 23, 2012Paper 3.3: Revaporisation - Bottomley et. al.

A study of the revaporisation behaviour of deposits from the metallic vertical line of Phébus FPT3

by

P. D. W. BOTTOMLEY1, E. FONTANA1, D. PAPAIOANNOU1, G. MONTAGNIER1, E. TEIXEIRA1, C. DIEBOLD1, S. VAN WINCKEL1, J-Y. COLLE1, & V. V. RONDINELLA1; andB. SIMONDI-TEISSEIRE2, F. PAYOT2 & T. HASTE2

1ITU KARLSRUHE (DE) 2IRSN, Cadarache (FR)

Institute for Transuranium Elements (ITU)Karlsruhe, Germanyhttp://www.itu.jrc.cec.eu.int


PhenomenonRevaporisation of deposits can occur in the late stages of a reactor accident when fission product deposits could be exposed to steam surges (from attempted refloods) or undergo reheating (decay heat). - In such conditions already-deposited fission products could revolatilise and travel further down the primary circuit & so significantly increase the source term release.

Introduction

Earlier testingInitial testing on FPT1 vertical line samples (Revaporisation SCA project - a ITU/VTT /AEA Tech. Winfrith Collaboration) of FPT1’s vertical line. This had showed that Cs revaporisation could occur > 500°C - explained Cs releases as FPT1 test shutdown (since waves of fresh steam). Similar behaviour observed for porous ceramic (ThO2) deposits from FPT4 debris bed.

This paper - presents the revaporisation testing on samples of the Phebus FPT3 vertical line.


Phebus FPT3 vertical linesample cutting positions

3AO-V11 (lowest)3AO-V14 3AO-V15 (bend – thicker deposit)

- 3 7 9 8 - 3 7 7 8

- 3 6 5 0 - 3 6 7 0

C o m b u s t i b l e

I n o x

I n c o n e l

3 A 0 - V 1 5

3 A 0 - V 1 4

3 A 0 - V 1 1

F i g u r e 2 : S c h é m a d e l a l i g n e v e r t i c a l e d u d i s p o s i t i f

Stainless

Inconel

Inconel

Bundle

Vertical line


Actual Phébus FPT3 vertical line sampling positions

V15

V14

V11

1) high activity sample-

2) low activity inox sample

3) low activity inconel sample

Sampling done in areas of high activity

Ligne verticale FPT3

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

1,00E-02

-7000 -6750 -6500 -6250 -6000 -5750 -5500 -5250 -5000 -4750 -4500 -4250 -4000 -3750 -3500

cote dispositif (mm)

0,00E+00

4,00E-04

8,00E-04

1,20E-03

1,60E-03

2,00E-03

2,40E-03

2,80E-03

3,20E-03

3,60E-03

4,00E-03

Cs-137

Cs-137 zoom

deuxième cône

TCcentreur de canal

2° scan : 18 au 21 fév. 05

IRSN Cadarache


FPT3 Test - Vertical line samples – activities & substrate compositions as received

V11 - Inconel V14 - stainless steel V15 – Inconel - bend

thick (5mm) outer Ni coating of vertical line –difficult to cut

FPT3 Vertical line sample activities (MBq)

sample Cs-134 Cs-137 total activity

3V0-V15 1989.7 58136.7 60126

3V0-V14 201.0 5546.4 5747

3V0-V11 142.9 4841.8 4985

Cs-134 & Cs-137 were > 97% of the total measured g activity (meas. date.: Feb. 2005)

Substrate alloy compositions

Alloy Fe Ni Cr C Mn S Si

Inconel 600

6-10 Bal. 14-17 <0.15 <1 0.015 0.5 Cu<0.5 Co <0.3

AISI 304L

Bal. 8-11 18-20 <0.03 <2 0.015 0.75 P=0.04


PHEBUS FPT3 - V11 revaporisation sampleMacrographs & V15 powder

V11-1

V11-2

V11-3

V11-4

V11-5

V11-6

V11-7V11-8

V11-1

V11-3

V11-2

V11-4

Average size: 5-10 x 5-10 mmDose rate: typically ~1-2mSv.h-1

powder deposit: from V15 cutting


PHEBUS FPT3 - Revaporisation facility 1

Detector +liq. N2 cooler

Lead shielding

PC - Data acquisition system

Gas supply system panel


Gamma detector monitors loss of activity during heat-up

(revaporisation) and then can scan the installation for the

distribution

Glove box

-detectorRails for detector

PHEBUS FPT3 - Revaporisation facility 2


Phébus FPT3 revaporisation test matrix

Samples0,5 -cm x 0,5-1cm samples FPT3 vertical line (V11,14 & 15) have been tested under different

flowing atmospheres by ramping to 1000°C, holding for 1h & then slow cooldown. Sample activities: 1,3 - 8mSv.h-1

TestsV11 1) pure steam – fast ramp (35-25°C/min)

2) pure steam –slow ramp (2°C/min) – standard test3) mixed atmosphere (Steam /55% H2)4bis) slightly oxidising (steam to 700°C) then v. reducing (Ar-6,5 %H2)5) low pressure, then very reducing atmos. Ar-6,5 %H2 from 700°C)

V14 6) pure steam –slow ramp (2°C/min) V15 7) pure steam –slow ramp (2°C/min)V11 8) air - slow ramp to 900°C

2. gamma spectroscopy during the test shows the revaporisation of 137Cs ( at 661 keV)

3. Aerosol deposit on filters is later analysed by ICP-MS to give the revaporisation behaviour of other nuclides.

* standard test was also used for FPT1 metallic vertical line & FPT4 ceramic plenum samples


PHEBUS FPT3 Revaporisation Test 3Samples pre- & post-test

Pre-test Post-test

Test No. 3 - steam atmosphere normal (slow) heat-up 1) N2 upto 300°C - @ 10°C.min-1

- to prevent steam condensation in the furnace tube (3-4 bar)2) Plateau 300°C - 10mins - changeover to steam (~4 bar), 3) Ramp 300°C - 1000°C @ 2°C min-1 in steam 4) Plateau 1000°C for 1h - steam 5) 1000°C - 300°C @ 10°C min-1 changeover to N2

6) 300-20°C @ 10°C min-1 in N2


0

0,2

0,4

0,6

0,8

1

1,2

0 100 200 300 400 500 600

Time / mins

No

rmalised

Cs-1

37 a

cti

vit

y (

%)

0

200

400

600

800

1000

1200

Ac

tua

l te

mp

era

ture

/ °C

start of revap: 780°C

~30% activity at 1000°C

10% residual activity heating ramp rate ~35-20°C/min

start of revap: 520°C

Phebus FPT3 tests 1-3Cs-activity revaporisation from vertical line deposits in steam & mixtures to 1000°C (V11 samples)

Steam/55%H2

Steam

2°C/min

Steam - rapid

Effect of a) heat-up rate & b) reducing atmosphereRevaporisation rates: 1) steam rapid: >780°C 80%/220°C = 0,36%/°C (in 20 mins. – 4%/min)

2) steam: >520°C 70%/480°C = 0,15%/°C (in 240 mins. – 0,3%/min) 3) steam/55%H2: >780°C 70%/220°C = 0,32%/°C (in 100 mins. – 0,7%/min)


Phebus FPT3 Revaporisation Test 1

Scanning of 137Cs activity along the oven, diluter & filter (pre- & post-test) of FPT3 -V11-1 (steam)

Revaporised deposit is mainly on filter

0

50

100

150

200

250

300

100 120 140 160 180 200

Position/cm

Co

un

ts/i

mp

.s-1

hot zoneDT1cold zonedilutiontransit zoneaerosol capture

No sample

Pre-test scan of sample

Post-test with sample

Deposit on filter


0

50

100

150

200

250

300

350

400

1 52 103 154 204 255 306 357 408 459 509 560 611

Time /mins.

Act

ivit

y C

s-13

7/ C

ou

nts

.min

-1

0

200

400

600

800

1000

1200

Tem

per

atu

re/

°C

N2 steam Ar - 6,5% H2 N2

Total Revaporisation ~60%

Revaporisation under steam starts at ~550°C

revaporisation stops with change to reducing gas at 700°C, but starts again at ~800°C & is faster !

slope 1slope 2

diffusion-limited final revap.

Tsample= 934°C

cooling curve

Revaporisation rates: steam : 14% loss @ 550-700°C= 0,09%/°C (in 58 mins.=0,24%.min-1) Ar-6,5%H2 : 38% loss @ 800-920°C= 0,32%/°C (in 71 mins.=0,53%.min-1)

& 10% loss at 1000°C

PHEBUS FPT3 Revaporisation 4bis testLoss of Cs-137 activity from a V14B sample during

heating under steam then reducing atmosphere


V15 steam revaporisation rates: 1: 28% loss @ 620-840°C= 0,13%/°C (in 105 mins. = 0,27%.min -1) 2: 60% loss @ 840-1000°C= 0,38%/°C (in 80 mins. = 0,75%.min-1)

PHEBUS FPT3 Revaporisation Test 5 Loss of Cs-137 activity from a V15 B sample during heating under steam atmosphere

0

50

100

150

200

250

300

350

0 100 200 300 400 500 600

Time / minutes

Cs

-13

7 P

ea

k A

rea

/ c

ou

nts

.min

-1

0

200

400

600

800

1000

1200

Te

mp

era

ture

/°C

Revap. starts 620°C

Revap. faster from 840°C

Revap.finished by 1000°C from 810°C

Residual Activity 12%

88% Revap loss

N2 N2steam


0

500

1000

1500

2000

2500

3000

1 31 61 91 121 151 181 211 241 271 301 331 361

Time/ mins

Cs-

137

Pea

k A

ctiv

ity/

Co

un

ts.m

in-1

0

200

400

600

800

1000

1200

Tem

per

atu

re /

°C


Total Revaporisation 91%

change in kinetics ?

fast kinetics550-700°C

N2 Low pressure N2Ar-6,5%H2 N2

slower kinetics700-1000°C

V11 revaporisation rates: 1: 51% loss @ 550-670/700°C = 0,42%/°C ( in 65 mins. = 0,78%.min -1) 2: 40% loss @ 700-1000°C = 0,13%/°C ( in 180 mins. = 0,18%.min -1)

PHEBUS FPT3 Revaporisation Test 6 Sample V11-IX under low pressure N2 up to 700°C,

then reducing atmosphere (Ar-6.5%H2) up to 1000°C


0

1000

2000

3000

4000

5000

6000

7000

2 77 152 227 306 382 457 534

Time / mins

Cs-

137

Pea

k A

rea

/Co

un

ts.m

in-1

0

200

400

600

800

1000

1200

Tem

per

atu

re/°

C

N2 Ar - 6,5%H2Steam N2

Residual Activity ~11%

slight revaporisation already from 300°C

Total revaporisation: ~90%

similar activity loss rates from 300 to 900°C

52% loss of remaining deposit on sw itching to reducing gas reducing to 32% in next ~7 mins

change in revap kinetics?

Revap to 700°C = ~15%

Total Revap after change of gas @ 700°C: 75%

Revaporisation rates: 1: 15% loss @ 300-700°C in steam = 0,04%/°C (in 65 mins. = 0,78%.min -1) 2: 60% loss @ 700°C on switch to Ar-6,5%H2

3: 15% loss @ 700-1000°C = 0,05%/°C (in 172 mins. = 0,09%.min-1)

PHEBUS FPT3 Revaporisation test 7 Loss of Cs-137 activity of V11-X sample heating to 1000°C under steam then reducing Ar-6,5%H2 gas


Revaporisation rates: 1: 7% loss @ 300-570°C in air = 0,03%/°C ( in 160 mins. = 0,05%.min -1) 2: 70% loss @ 610-720°C in air= 0,64%/°C ( in 85 mins. = 0,83%.min -1)

3: 14% loss @ 720-900°C in air= 0,08%/°C (in 143 mins. = 0,10%.min-1)

PHEBUS FPT3 Revaporisation test 8Loss of Cs-137 activity from sample V11-XI heating

in air to 900°C.

0

2000

4000

6000

8000

10000

12000

14000

0 90,0 180,0 270,0 360,0 450,0 540,0

Time /mins

Cs

Pea

k (6

61ke

V)

Act

ivit

y /

cou

nts

.min

-1

0

100

200

300

400

500

600

700

800

900

1000

Sam

ple

T

emp

erat

ure

/°C

N2 Air N2

Revaporisation starts at ~570°C

Rapid revap kinetics from 610 -720°C

Slower revap kinetics from 730-900°C

Total Revaporisation 91%


7% revaporisation 300-570°C

Kinetics change at 720°C


PHEBUS FPT3 Summary Table of Cs-137 Revaporisation Rates.

Expt No. Sample ConditionsTemp/atmosphere

Revaporisation start /end/ %revap (Total revap)

Revaporisation rates1st/ 2nd %activity/°C

Revap 1 V11-I ~2.0mSv/h-1 1000°C/steam (fast) 780°C/1000°C/20mins/ 90% 0,36%/°C

Revap 2 V11-II 1.3mSv/h-1 1000°C/45%steam-55%H2

780°C/1000°C/100mins/ 67% 0,31%/°C

Revap 3 V11-III 2.1mSv/h-1 1000°C/steam (normal) 520°C/1000°C/240mins/ 67% 0,14%/°C

Revap 4 bis

V14-B 1,8mSv/h-1 a) Steam/700°Cb) Ar-6,5%H2/700-

1000°C

a) 550°C/700°C/58mins/14%b) 800°C/920°C/72min/ 37%*Total Revaporisation: 60%

0,09%/°C0,32%/°C

Revap 5 V15 ~3mSv/h-1 1000°C/steam a) 620°C/840°C/105mins/32%b) 840°C/1000°C/80mins/56%Total Revaporisation: 88%

0,15%/°C0,35%/°C

Revap 6 V11-IX ~6mSv/h-1 a) <700°C low pres, b) 700-1000°C/(Ar-6,5%H2)

a) 550°C/670°C/65mins/51%b) 700/1000°C/180mins/40%Total Revaporisation: 91%

0,42%/°C0,13%/°C

Revap 7 V11-X ~6-8mSv/h-1 steam to 700°C /(Ar-6,5%H2) to 1000°C &

cool down

a) 300°C/700°C/65mins/15% b) 700°C/<3min/60%c) 700°C/1000°C/172mins/15%Total Revaporisation: 90%

0,04%/°CVery high0,05%/°C

Revap 8 V11-XI ~8mSv/h-1 900°C/Air a) 300°C/570°C/160mins/7%b) 610°C/720°C/85min/70%c) 720°C/900°C/172mins/14%Total Revaporisation: 91%

0,03%/°C0,64%/°C0,08%/°C

* and final 10% at 1000°C


1) Tests on the Phebus FPT3 vertical line show the Cs deposits undergo revaporisation under a range of conditions and atmospheres (in steam, steam/H2 and Ar-6.5%H2, and up to 900°C in air). The ranking of revaporisation rates are: air >steam-55%H2 > steam.

2) Cs revaporisation is in all cases between 60-95% depending on atmosphere. It commences at ~550°C and is completed at 1000°C.

3) High revaporisation (90-95%) is observed on most metallic surfaces (as in metallic FPT1 samples).

4) Lesser revaporisation (60 -70%) in some tests implies Cs is embedded in oxide film (ie. diffusion limitation) as in porous ThO2 FPT4 samples.

5) More rapid heat–up rates delays the onset of revaporisation to nearly 800°C but then it is faster.

6) Reduced atmosphere pressures can also increase the revaporisation rate, even below 700°C. 7) There is no noticeable difference between revaporisation from the metallic substrates

(Inconel vs. stainless steel).

661keV

Conclusions from revaporisation tests with FPT3 vertical line samples - 1

Revaporisation Phenomenon


8) V11 in air & V14 under steam show changes in revaporisation above 700-800°C: V11 in air it slows down –V14 in steam it accelerates. This suggests different chemical forms are revolatilising - also differences in deposit composition would contribute.

9) Changes in atmosphere (or DGO2) at 700°C to strongly reducing (Ar-6,5%H2) increased the revaporisation rate when: i) it was switched from steam atmosphere in 2 tests (V14 & V11 samples) -in one case with enormous acceleration (possible chemical reaction?), followed by a slow final phase (exhaustion of deposit?). ii) by contrast, switching from low pressure N2 to Ar-6.5%H2 at 700°C was observed to slow the revaporisation rate, but this maybe a result of the acceleration in revaporisation caused by the low presssure N2 in the1st stage.

661keV

Conclusions from revaporisation tests with FPT3 vertical line samples - 2

Revaporisation with changing rates and atmospheres

ermsar 2012, cologne march 21 – 23, 2012 paper 3.3: revaporisation - bottomley et. al. a study of...

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