1. ERMSAR 2012, Cologne March 21 – 23, 2012 Paper 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. BOTTOMLEY 1, E. FONTANA 1, D. PAPAIOANNOU 1, G. MONTAGNIER 1, E. TEIXEIRA 1, C. DIEBOLD 1, S. VAN WINCKEL 1, J-Y. COLLE 1, & V. V. RONDINELLA 1 ; and B. SIMONDI-TEISSEIRE 2, F. PAYOT 2 & T. HASTE 2 1 ITU KARLSRUHE (DE) 2 IRSN, Cadarache (FR) Institute for Transuranium Elements (ITU) Karlsruhe, Germany http://www.itu.jrc.cec.eu.int

2. ERMSAR 2012, Cologne March 21 – 23, 2012 Paper 3.3: Revaporisation - Bottomley et. al. Phenomenon Revaporisation 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 testing Initial 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 (ThO 2 ) deposits from FPT4 debris bed. This paper - presents the revaporisation testing on samples of the Phebus FPT3 vertical line.

3. ERMSAR 2012, Cologne March 21 – 23, 2012 Paper 3.3: Revaporisation - Bottomley et. al. Phebus FPT3 vertical line sample cutting positions 3AO-V11 (lowest) 3AO-V14 3AO-V15 (bend – thicker deposit) Stainless Inconel Bundle Vertical line

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

5. ERMSAR 2012, Cologne March 21 – 23, 2012 Paper 3.3: Revaporisation - Bottomley et. al. 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) sampleCs-134Cs-137total activity 3V0-V15 1989.758136.760126 3V0-V14 201.05546.4 5747 3V0-V11 142.94841.8 4985 Cs-134 & Cs-137 were > 97% of the total measured g activity (meas. date.: Feb. 2005) Substrate alloy compositions AlloyFeNiCrCMnSSi Inconel 600 6-10Bal.14-17<0.15<10.0150.5Cu<0.5Co <0.3 AISI 304L Bal.8-1118-20<0.03<20.0150.75P=0.04

6. ERMSAR 2012, Cologne March 21 – 23, 2012 Paper 3.3: Revaporisation - Bottomley et. al. PHEBUS FPT3 - V11 revaporisation sample Macrographs & V15 powder V11-1 V11-2 V11-3 V11-4 V11-5 V11-6 V11-7 V11-8 V11-1 V11-3 V11-2 V11-4 Average size: 5-10 x 5-10 mm Dose rate: typically ~1-2mSv.h -1 powder deposit: from V15 cutting

7. ERMSAR 2012, Cologne March 21 – 23, 2012 Paper 3.3: Revaporisation - Bottomley et. al. PHEBUS FPT3 - Revaporisation facility 1 Detector +liq. N 2 cooler Lead shieldingPC - Data acquisition system Gas supply system panel

8. ERMSAR 2012, Cologne March 21 – 23, 2012 Paper 3.3: Revaporisation - Bottomley et. al. Gamma detector monitors loss of activity during heat-up (revaporisation) and then can scan the installation for the distribution Glove box  -detector Rails for detector PHEBUS FPT3 - Revaporisation facility 2

9. ERMSAR 2012, Cologne March 21 – 23, 2012 Paper 3.3: Revaporisation - Bottomley et. al. Phébus FPT3 revaporisation test matrix Samples 0,5 -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 Tests V111) pure steam – fast ramp (35-25°C/min) 2) pure steam –slow ramp (2°C/min) – standard test 3) mixed atmosphere (Steam /55% H 2 ) 4bis) slightly oxidising (steam to 700°C) then v. reducing (Ar-6,5 %H 2 ) 5) low pressure, then very reducing atmos. Ar-6,5 %H 2 from 700°C) V146) pure steam –slow ramp (2°C/min) V15 7) pure steam –slow ramp (2°C/min) V118) air - slow ramp to 900°C 2. gamma spectroscopy during the test shows the revaporisation of 137 Cs ( 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

10. ERMSAR 2012, Cologne March 21 – 23, 2012 Paper 3.3: Revaporisation - Bottomley et. al. PHEBUS FPT3 Revaporisation Test 3 Samples pre- & post-test Pre-test Post-test Test No. 3 - steam atmosphere normal (slow) heat-up 1)N 2 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 N 2 6) 300-20°C @ 10°C min -1 in N 2

11. ERMSAR 2012, Cologne March 21 – 23, 2012 Paper 3.3: Revaporisation - Bottomley et. al. Phebus FPT3 tests 1-3 Cs-activity revaporisation from vertical line deposits in steam & mixtures to 1000°C (V11 samples) Steam/55%H 2 Steam 2°C/min Steam - rapid Effect of a) heat-up rate & b) reducing atmosphere Revaporisation 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%H 2 : >780°C 70%/220°C = 0,32%/°C (in 100 mins. – 0,7%/min)

12. ERMSAR 2012, Cologne March 21 – 23, 2012 Paper 3.3: Revaporisation - Bottomley et. al. Phebus FPT3 Revaporisation Test 1 Scanning of 137 Cs activity along the oven, diluter & filter (pre- & post- test) of FPT3 -V11-1 (steam) Revaporised deposit is mainly on filter No sample Pre-test scan of sample Post-test with sample Deposit on filter

13. ERMSAR 2012, Cologne March 21 – 23, 2012 Paper 3.3: Revaporisation - Bottomley et. al. Revaporisation rates: steam : 14% loss @ 550-700°C= 0,09%/°C (in 58 mins.=0,24%.min -1 ) Ar-6,5%H 2 : 38% loss @ 800-920°C= 0,32%/°C (in 71 mins.=0,53%.min -1 ) & 10% loss at 1000°C PHEBUS FPT3 Revaporisation 4bis test Loss of Cs-137 activity from a V14B sample during heating under steam then reducing atmosphere

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

15. ERMSAR 2012, Cologne March 21 – 23, 2012 Paper 3.3: Revaporisation - Bottomley et. al. Residual Activity 9% Total Revaporisation 91% change in kinetics ? fast kinetics 550-700°C N2N2 Low pressure N 2 Ar-6,5%H 2 N2N2 slower kinetics 700-1000°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 N 2 up to 700°C, then reducing atmosphere (Ar-6.5%H 2 ) up to 1000°C

16. ERMSAR 2012, Cologne March 21 – 23, 2012 Paper 3.3: Revaporisation - Bottomley et. al. 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%H 2 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%H 2 gas

17. ERMSAR 2012, Cologne March 21 – 23, 2012 Paper 3.3: Revaporisation - Bottomley et. al. 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 8 Loss of Cs-137 activity from sample V11-XI heating in air to 900°C. 7% revaporisation 300-570°C Kinetics change at 720°C

18. ERMSAR 2012, Cologne March 21 – 23, 2012 Paper 3.3: Revaporisation - Bottomley et. al. PHEBUS FPT3 Summary Table of Cs-137 Revaporisation Rates. Expt No.SampleConditions Temp/atmosphere Revaporisation start /end/ %revap (Total revap) Revaporisation rates 1 st / 2 nd %activity/°C Revap 1V11-I ~2.0mSv/h -1 1000°C/steam (fast)780°C/1000°C/20mins/ 90%0,36%/°C Revap 2V11-II 1.3mSv/h -1 1000°C/ 45%steam-55%H 2 780°C/1000°C/100mins/ 67%0,31%/°C Revap 3V11-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°C b) Ar-6,5%H 2 /700- 1000°C a) 550°C/700°C/58mins/14% b) 800°C/920°C/72min/ 37%* Total Revaporisation: 60% 0,09%/°C 0,32%/°C Revap 5V15 ~3mSv/h -1 1000°C/steama) 620°C/840°C/105mins/32% b) 840°C/1000°C/80mins/56% Total Revaporisation: 88% 0,15%/°C 0,35%/°C Revap 6V11-IX ~6mSv/h -1 a) <700°C low pres, b) 700-1000°C/(Ar- 6,5%H 2 ) a) 550°C/670°C/65mins/51% b) 700/1000°C/180mins/40% Total Revaporisation: 91% 0,42%/°C 0,13%/°C Revap 7V11-X ~6-8mSv/h -1 steam to 700°C /(Ar- 6,5%H 2 ) 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%/°C Very high 0,05%/°C Revap 8V11-XI ~8mSv/h -1 900°C/Aira) 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%/°C 0,64%/°C 0,08%/°C * and final 10% at 1000°C

19. ERMSAR 2012, Cologne March 21 – 23, 2012 Paper 3.3: Revaporisation - Bottomley et. al. 1)Tests on the Phebus FPT3 vertical line show the Cs deposits undergo revaporisation under a range of conditions and atmospheres (in steam, steam/H 2 and Ar-6.5%H 2, and up to 900°C in air). The ranking of revaporisation rates are: air >steam-55%H 2 > 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 ThO 2 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

20. ERMSAR 2012, Cologne March 21 – 23, 2012 Paper 3.3: Revaporisation - Bottomley et. al. 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  G O 2 ) at 700°C to strongly reducing (Ar-6,5%H 2 ) 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 N 2 to Ar-6.5%H 2 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 N 2 in the1 st stage. 661keV Conclusions from revaporisation tests with FPT3 vertical line samples - 2 Revaporisation with changing rates and atmospheres