Upload
others
View
0
Download
0
Embed Size (px)
Citation preview
J. Stuckert, FZK/IMF1/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
Experimental and Post-Test Calculation Resultsof the Integral Reflood Test QUENCH-12
with a VVER-type Bundle
J. Stuckert, M. Große, M. SteinbrückForschungszentrum Karlsruhe
J. Stuckert, FZK/IMF2/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
Zry rod
(2000 °C)
Water
Steam
Zr +2 H2O → ZrO2 + 2 H2 + 596 kJ
High-Temperature Materials Behavior andFlooding of an Overheated LWR Core and Hydrogen Source Term
J. Stuckert, FZK/IMF3/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
bundle bottom
bundle top
shroud with heat insulation
QUENCH-12Test bundle assembling
J. Stuckert, FZK/IMF4/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
AgInCd absorber, SARNET-Aerosol52WaterNov 7, 2007QUENCH-13
ACM series: M5 ® cladding41WaterJuly 2, 2008QUENCH-14
ISTC 1648.2; VVER48WaterSept 27, 2006QUENCH-12
EC LACOMERA-2; Boil-off, SARNET-Benchmark15WaterDec 8, 2005QUENCH-11
July 21, 2004
July 03, 2002
July 24, 2003
July 25, 2001
Dec 13, 2000
March 29, 00
Juni 30, 1999
Jan 20, 1999
July 07, 1998
Feb 26, 1998
Test date
EC LACOMERA-1; Air ingress50WaterQUENCH-10
EC COLOSS; As Q-07 but under steam starvation49SteamQUENCH-09
As Q-07 but without B4C absorber15SteamQUENCH-08
EC COLOSS; B4C absorber15SteamQUENCH-07
OECD ISP-45; As Q-05 but with water flooding42WaterQUENCH-06
As Q-04 but with pre-oxidation48SteamQUENCH-05
Steam, reference50SteamQUENCH-04
As Q-02 but flooding delayed40WaterQUENCH-03
EC COBE47WaterQUENCH-02
EC COBE52WaterQUENCH-01
RemarksFloodingrate, g/sQuenchmediumTest
Test Matrix (1998-2008)
J. Stuckert, FZK/IMF5/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
Objectives of the QUENCH-12 test
• investigation of the effects of VVER materials and bundle geometry on core reflood
• comparison with the PWR bundle on the base of repeat of the test QUENCH-06 (ISP-45) scenario
J. Stuckert, FZK/IMF6/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
Cross section of the VVER test columnCladding material: E110 (Zr1%Nb)
Cross section of the PWR test columnCladding material: Zry-4 (or M5)
1 unheated rodcladding Zry-4 ø10.75/9.3 mmcentral thermocouplepellet ZrO2 ø9.15/2.5mm
thermalinsulationZrO2 fibrethickn. 37 mm
2 removable corner rodsZry-4 ø6 mm
2 instrumented tubesZry-4ø6/4.2 mm
shroud Zry-4ø84.76/80mm
cooling jacket
20 heated rodscladding Zry-4ø10.75/9.3 mmW-heater ø6mmpellet ZrO2ø9.15/6.15mm
pitch 14.3 pitch 12.753 removable corner rodsZr1%Nb ø6 mm
3 instrumented tubesZr1%Nbø6/4.2 mm
18 heated rodscladding Zr1%Nbø9.15/7.73 mmW-heater ø4mmpellet ZrO2ø7.54/4.15mm
ShroudZr2.5%Nbø88/83.5mm
13 unheated rodscladding Zr1%Nb ø9.15/7.73 mmcentral thermocouplepellet ZrO2 ø7.54/4.15mm
Comparison of PWR and VVER test columns
J. Stuckert, FZK/IMF7/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
Pretest modelling support:
1. SCDAP/SIM simulations: Paul Scherer Institute, Switzerland.
2. ICARE/CATHARE simulations: Kurchatov Institute, Mosccow,with support from IRSN Cadarache).
J. Stuckert, FZK/IMF8/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
Test performance: el. power profile in accordanceto the pre-test calculations provided good reproductionof temperature history in comparison with the reference test QUENCH-06
J. Stuckert, FZK/IMF9/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
Comparison of transient and reflood phases forQUENCH-14 (M5), QUENCH-12 (E110), QUENCH-06 (zry-4):
similar escalation before reflood
bundle temperature at hot elevation of 950 mm shroud temperature at hot elevation of 950 mm
T12 < T06 < T14 T06 < T12 < T14
J. Stuckert, FZK/IMF10/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
QUENCH-12, quench phase: selected readingof the bundle thermocouples. Quench front propagation.
Cooling of the bundle during ~350 s (similar to Q-06 and Q-14)
300
500
700
900
1100
1300
1500
1700
1900
2100
7100 7150 7200 7250 7300 7350 7400 7450 7500 7550 7600Time, s
Tem
pera
ture
, K
TFSU 31/5/17 TFC 13/3/16 TFC 16/4/15 TFC 15/3/14 TFC 14/4/13 TFC 1/13 TFSH 3/2/12 TFSH 7/2/11 TFSU 16/4/10 TFSH 30/5/9 TFSU 15/3/6 TFSU 13/3/5 TFSH 24/5/4 TFSH 4/2/1
quench
950 mm
250 mm
650 mm
J. Stuckert, FZK/IMF11/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
corner rod B after pre-test (800 °C, oxide layer thickness less of 5 µm)
corner rods withdrawn during the test:spalling of the outer skin of oxide layer due to breakaway oxidation.
D – withdrawn after pre-oxidation,F – withdrawn before reflood,
B – withdrawn after test.
D
F
B
QUENCH-12: withdrawn Zr1%Nb corner rods
β-Zr melted between880 and 1030 mm
J. Stuckert, FZK/IMF12/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
-250
-50
150
350
550
750
950
1150
1350
500 700 900 1100 1300 1500 1700 1900 2100T, K
Elev
atio
n, m
m
Q6_7170s_trans_end Q12_7265s_trans_end
Axial bundle temperature profiles for QUENCH-06 and QUENCH-12on beginning and end of transient phase
beginning of transient end of transient
-250
-50
150
350
550
750
950
1150
1350
500 700 900 1100 1300 1500 1700 1900 2100T, K
Elev
atio
n, m
m
Q6_5950s_preox_end Q12_5972s_preox_end
E110break-away
E110break-away
J. Stuckert, FZK/IMF13/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
900 mm:circumferential
and longitudinal cracksat the cladding;
nodular breakawaycorrosion
at the shroud
650 mm:spalled oxide scales
at shroud and cladding
400 mm:circumferential spalling
of the oxide layeron the surface
of fuel rod simulator cladding-400mm:
spalled oxide scalesas debris
at the bundle bottom
QUENCH-12: post-test videoscope observations of breakaway oxidation at different elevations of the bundle
Tmax
Tmin
J. Stuckert, FZK/IMF14/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
β-Zr
α-Zr(O)
ZrO2
β-Zr
α-Zr(O)
ZrO2
Comparison cross-sections of QUENCH-06 and QUENCH-12at elevation 550 mm with ZrO2 thickness ~40 µm
Q12 cladding: spalling of oxide scalesdue to breakaway effect
Q12: rubble on spacer gridconsists of spalled cladding scales
and fragments of partially oxidized cladding
Q06 oxidized cladding
Q06 cross-section
J. Stuckert, FZK/IMF15/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
Comparison cross-sections of QUENCH-06 and QUENCH-12 at elevation 750 mm with ZrO2 thickness ~80 µm
Q06 cross-section;few bundle deformation
Q12 cross-section;moderate bundle deformation
β-Zr
α-Zr(O)
ZrO2
β-Zr
α-Zr(O)
ZrO2
Q12 cladding: spalling of oxide scalesdue to breakaway effect
Q06 oxidized cladding
J. Stuckert, FZK/IMF16/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
Comparison of averaging oxide cladding thicknessesfor QUENCH-06 and QUENCH-12 at all elevations
0
100
200
300
400
500
600
700
800
900
1000
550 650 750 850 950 1050 1150Bundle elevation, mm
ZrO
2 th
ickn
ess,
µm
Q12_ZrO2 (1.56*exhausted metal) Q06_ZrO2
Degree of cladding oxidation is mostly lower for QUENCH-06 (Zry-4) in comparison to QUENCH-12 (E110)
E110 breakaway
J. Stuckert, FZK/IMF17/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
Q-06Q12: H2 uptake in claddingmeasured by hot extraction
Comparison of hydrogen uptake by bundleduring QUENCH-06 and QUENCH-12
Q-12: H2 uptake in corner rods measured by neutron radiography
0
5
10
15
20
25
30
35
40
550 750 950 1150Bundle elevation, mm
Hyd
roge
n, a
t%
corner rod D (preox)corner rod F (tansient)corner rod B (end of test)
releaseof absorbedhydrogen
0
5
10
15
20
25
30
35
40
550 650 750 850 950 1050 1150Bundle elevation, mm
Hyd
roge
n, a
t%Q6_hydrogen absorbed in claddings; at%Q12_hydrogen absorbed in claddings; at%
QUENCH-12breakaway
(according totemperature
history)
J. Stuckert, FZK/IMF18/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
Cooling during normal cleaning:- high flow rate- closed loop
Cooling after cleaning - low flow rate - open loop with connection to spent fuel pool - possibility of by-pass by bundle low head
decay heat for 30 bundle: 241 kW
Paks/Ungary cleaning tank incident in April 2003with destroying of 30 VVER fuel assemblies
J. Stuckert, FZK/IMF19/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
0
200
400
600
800
1000
1200
1400
0 5000 10000 15000 20000 25000
0 1 2 3 4 5 6 7
0
200
400
600
800
1000
1200
1400
123 4 5 6
7
8
910
Time (h)
Time (s)
Cla
ddin
g te
mpe
ratu
re (o
C)
Breakaway long-term oxidation during the Pakscleaning tank incident (destroying of 30 VVER fuel assemblies)
Results of modeling (FRAP-T6 code)
breakawayregion
J. Stuckert, FZK/IMF20/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
Collapse of VVER-bundles, strong hydrogenatedunder breakaway conditions
J. Stuckert, FZK/IMF21/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
Other important phenomenon: melt formation and oxidation byQUENCH-06 and QUENCH-12 at elevation 950 mm
Q06 - bundle geometry intact->good coolability;
melt localized between pellet and ZrO2 layer Q12 – bundle geometry destroyed->
declined coolability;molten pools formation inside rod clusters
J. Stuckert, FZK/IMF22/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
Melt formation and oxidation byQUENCH-06 and QUENCH-12 at elevation 950 mm
Q12: molten pool between rods,precipitates formation due to melt oxidation in steam
Q06: melting of cladding metal layer,precipitates formation on cooldown
J. Stuckert, FZK/IMF23/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
850 - 900 mm: melt formation in bundle at the position of melted corner rod B
neutronographyshows the deep holeat the placeof melted out β-Zr
A
C
E
1010 mm
1035 mminitial positionof rod B
QUENCH-12: melting of corner rod B
J. Stuckert, FZK/IMF24/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
0,0
0,5
1,0
1,5
2,0
2,5
3,0
7000 7050 7100 7150 7200 7250 7300 7350 7400 7450 7500Time, s
Rat
e, m
g/s
0
10
20
30
40
50
60
Inte
gral
, g
rate_H2_Q12 rate_H2_Q6 intl_H2_Q12 intl_H2_Q6
reflood QUENCH-12
reflood QUENCH-06
Comparison of hydrogen releaseduring QUENCH-12 and QUENCH-06
J. Stuckert, FZK/IMF25/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
Comparison of post-test cladding and melt structuresfor Q-08 and Q-12
Q-08, 860 mm Q-12, 850 mm
J. Stuckert, FZK/IMF26/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
0
500
1000
1500
2000
2500
3000
-80 -60 -40 -20 0 20 40 60 80 100 120Time, s
Rel
ease
rate
, mg/
s; T
empe
ratu
re, K
Q08_H2 rate Q12_H2 Q08_TIT A/13 Q12_TIT A/13
flooding
Comparison of hydrogen release during refloodfor Q-08 test (oxidation before transient 270 µm; significant melt oxidation)
and Q-12 test (oxidation before transient 160 µm; minor melt oxidation)
Long duration of hydrogen productionduring the quench phase in case of significant melt oxidation (Q-08)
J. Stuckert, FZK/IMF27/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
Despite the similar thermal response through almost the entire sequence,all of the calculations underestimated the oxidation.
QUENCH-12: calculated and measured hydrogen generation/J. Birchley, PSI/
C-P: Cathcart-PawelU-H: Urbanic-HeidrickP-C-S: Prater-Courtright-Schanz
J. Stuckert, FZK/IMF28/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
CONCLUSIONS
• The QUENCH-12 experiment was carried out to investigate the effects of VVER materials and bundle geometry on core reflood, in comparison with the test QUENCH-06 (Zry-4-cladding) with western PWR geometry.
• During the pre-oxidation and transient phases the E110 cladding alloy is susceptible to breakaway oxidation within relative broad temperature range (1050 – 1300 K). Oxide scale of layered type showed spalling into sub-layers and loss of fragments, which were collected at spacer grids and bundle bottom.
• The breakaway oxidation was accompanied by hydriding of claddings and shroud with the result of material embrittlement, which can lead to a severe degradation of the bundle during quenching as was demonstrated in the Paks accident.
J. Stuckert, FZK/IMF29/29
Computational and Experimental Studies of LWR Fuel Element Behaviorunder beyond Design Basis Accidents and Reflood Conditions:
Internat.Scientific and Technical Meeting, Moskva, Russia, July 27-28, 2009
CONCLUSIONS (cont.)
• Melting point of claddings and shroud metal layer was reached at the peak temperature elevations of 950 – 1050 mm. Contrary to QUENCH-06, where melt was confined between pellets and the outer cladding oxide layer, the melt in QUENCH-12 has in places dissolved the surrounding oxide layer. As a result, non-coherent melt relocation, melt pool formation, and minor melt oxidation were observed.
• The total hydrogen production was 58 g (QUENCH-06: 36 g), 24 g of which were released during reflood (QUENCH-06: 4 g). Three possible sources of increased hydrogen production during reflood: 1) interaction of steam with new metal surfaces developed by spalling of oxide scales damaged during pre-oxidation phase because breakaway effect; 2) release of hydrogenabsorbed in metal by breakaway during pre-oxidation and transient phases; 3) moderate melt oxidation released into space between rods.
• The S/R5 code adequately reproduced the QUENCH-12 thermal transient. Both the Cathcart-Pawel and Sokolov correlations underestimated the oxidation kinetics, but preliminary analysis indicates that the comparison with QUENCH-06 is consistent with the change in the bundle configuration and cladding material; in particular breakaway effect may have enhanced the oxidation.