NSRR High Burnup Fuel Tests for RIAs and BWR Power ...Oscillation Tests & RIA Tests 0 50 100 150 200...
Transcript of NSRR High Burnup Fuel Tests for RIAs and BWR Power ...Oscillation Tests & RIA Tests 0 50 100 150 200...
NSRR High Burnup Fuel Tests for RIAs and BWR Power Oscillations without Scram
T. Nakamura, H. Sasajima, J. Nakamura and H. UetsukaFuel Safety Research Lab. JAERI, Japan
Prepared for NSRC 2002 Oct. 29, 2002 at Washington D.C., USA
JAERI 1
Objectives of the NSRR TestsClarify influence of fuel burnups on- Fuel failure threshold and its mechanism- Consequence of the failure
(Fission gas release, fuel fragmentation & dispersal, etc. )under Reactivity-initiated accident (RIA), and toExamine fuel behavior under cyclic power transient conditions
simulating BWR power oscillations without scram
Fuel fragmentation& dispersal
Steam generation
Cross section
Cracking
Fission gas bubbles
High burnup (rim) structure
Oxide
Hydrides
Cladding deformationdue to PCMI
Thermal and fission gasbubble expansion of the pellets
Fission gas release
JAERI 2
Mechanism to cause failure Consequences of failure
NSRR (Nuclear Safety Research Reactor)
Inlet of offset loading tube
Reactor pool
Offset loading tube
Control rod driving mechanisms
Vertical loading tube
Driver coreExperimentalcapsule
6 Regulating rods2 Safety rods
3 Transient rods149 Driver core fuels
Test fuel
Experimental capsule
Experimental cavity
272J/g(65cal/g)
0.23 0.24 0.25 0.26 0.27
542J/g(130cal/g)
0
50
100
150
Time (s)
Line
ar h
eat
rate
(M
W/m
)
JAERI 3
200 mm
1250
mm
OuterCapsule
Test FuelRod
InnerCapsule
Test Capsule Instrumentation
Test Fuel Rod
Rod InternalPressure Sensor
Cladding SurfaceTemperature
Water Temperature
ElongationSensors
Water ColumnVelocity Sensor
Irradiation Capsule and Instrumentation
Strain gage
JAERI 4
NSRR Test Fuel & Burnups
Fuel type
Highly enrichedUO2 Irradiated
in JMTR
PWR
ATR/MOX
BWR
Pellet Burnup (GWd/t)
10 20 30 40 50 60Number of tests
Remarks
16failure >62cal/g
at 61GWd/t
22, failure >667J/g(160cal/g) at 38GWd/t
24 failure >60cal/g
at 50GWd/t
5no failure <140cal/g
at 20GWd/t
Test plan in 2002-2006
UO2 EU [<74GWd/t] JP [60GWd/t]
MOX ALPS[59GWd/t]
MOX [30-45GWd/t]
70 80
MOX
MOX
UO2
UO2
MOX
UO2 EU [<75GWd/t] JP [61-65GWd/t]
MOX EU[<78GWd/t]
Tests to be conducted in 2002-2003
UO2
JAERI 5
Power oscillation [25GWd/t]
EU: European fuel, JP: Japanese fuel
Brittle
Ductile
Oxide Hydride clusters
Key Observations in NSRR/RIA Tests(1) Hydride-assisted PCMI failure at low enthalpies (2) Consequence of fuel failure
(i) Fission gas release(ii) Fuel fragmentation
PWR50GWd/t
(hydrogen: about 400ppm) failed at 250J/g(60cal/g) BWR
61GWd/t(Hydrogen: about 200ppm)
failed at 292J/g(70cal/g)
Brittle
Ductile Zr liner
RIA Test ResultsJAERI 6
Test FK-90
90
Top Bottom20 mm
Fue
l rod
pow
er (M
W/m
)
Cla
ddin
g te
mpe
ratu
re (?
C)
[Cal
cula
ted
with
FR
AP
-T6]
Rod
inte
rnal
pre
ssur
e (M
Pa)
0.25 0.26 0.27 0.280
50
100
150
200
0
5
10
15
20Test FK-9 Time of failure
at 359J/g(86cal/g)
Rod power ( x 2 MW/m)
Average
Surface
Time (s)
BWR fuel at 61GWd/tU
(1) Hydride-assisted PCMI failure at low enthalpiesJAERI 7
PCMI Failure Thresholds
HBO-1 50GWd/t 250J/g(60cal/g)HBO-5 44GWd/t 321J/g(77cal/g)TK-2 48GWd/t 250J/g(60cal/g)TK-7 50GWd/t 359J/g(86cal/g)
FK-6 61GWd/t 292J/g(70cal/g)FK-7 61GWd/t 259J/g(62cal/g)FK-9 61GWd/t 359J/g(86cal/g)FK-10 61GWd/t 334J/g(80cal/g)
0 10 20 30 40 50 60 700
50
100
150
200
250
Pellet Average Fuel Burnup (GWd/tU)
Ent
halp
y In
crea
se (
cal/g
)
PCMI failure threshold(by the Japanese Nuclear Safety Commission)
No failure Failure Test ID No failure Failure
NSRR
Test ID
PWR
BWR
SPERT, PBF
CABRI UO2
CABRI MOX
JMTR
ATR/MOX
0
200
400
600
800
1000
Ent
halp
y In
crea
se (
J/g)
PWR fuel burnupsand failure enthalpies
JAERI 8
BWR fuel burnupsand failure enthalpies
Failure Map in Terms of Hydrogen Content and Fuel Enthalpy for BWR Fuel
0
250
500
750
0 50 100 150 200 250
Hydrogen content (wtppm)
Fue
l ent
halp
y (J
/g)
FailureNo Failure
solid: failedopen: not failed
Fuel failure correlates well to hydrogen content in cladding in BWR fuel tests.
JAERI 9
Fresh PWR Fuel Tests with Hydrided Cladding
Brittle cladding fracture due to PCMI occurred in fresh PWR fuel tests with hydridedcladding, similar to high burnup fuel tests.
JAERI 10
0.0
1.0
2.0
3.0
0 500 1000
Hydrogen content (%)
Cla
dd
ing
ho
op
str
ain
(%
)[c
alc
ura
ted
pe
ak]
Fresh PWRfailureno failure
5 cm
0.3 mm
Fuel stack
1 cm
Cross section of crack
Longitudinal crack of about 10cm generated over the fuel stack
0.0
1.0
2.0
3.0
0 500 1000
Hydrogen content (%)
Cla
dd
ing
ho
op
str
ain
(%
)[c
alc
ura
ted
pe
ak] Fresh PWRfailureno failure
Failure Criteria of Hydrided CladdingEstimated peak strains to cause the failure was larger in fresh fuel tests, suggesting influence of the irradiation embrittlement of the cladding.
Failure threshold differs depending on cladding type, suggesting hydride precipitation morphology effects.
Irradiated PWR rod failure
Fresh PWR rod failureIrradiated
BWR rod failure
JAERI 11
Transient hoop deformation of irradiated fuel cladding by PCMI during early phase of RIA transient was measured for the first time.
The hoop deformation was about 0.4% at fuel enthalpy of about 80cal/g.
Transient Hoop Strain MeasurementJAERI 12
0.24 0.25 0.26 0.27 0.28 0.29
StrainReactor power
Time of failureat 334J/g (80cal/g)
0
0.1
0.2
0.3
0.4
0.23 0.25 0.27Time (s)
Cla
ddin
g ho
op s
train
(%
)
Strain
Reactor power
Rod internalpressure
Test FK-10 (61GWd/t BWR)
Peak fuel enthalpy: 359J/g (86cal/g)no fuel failure
Test TK-10 (46GWd/t PWR)
Time (s)
Detachment of strain gage
Cladding strains at failurePeak strain measured at 70-80cal/g was below 0.4%.Plastic hoop strain of the cladding failed was 0%.?(Elastic strain< 0.6%)
20 40 60 80 100 1200.0
0.5
1.0
1.5
2.0100 200 300 400 500
Fuel enthalpy (cal/g)
Cla
ddin
g ho
op s
trai
n (%
)
Fuel enthalpy (J/g)
Calculated strain due to pellet thermal expansion
Measured peak strain (by strain gages)
Measured plastic strain
Estimated peak strain from plastic strains
Deformation to cause the failure could be explained by thermal expansion of fuel pellets
JAERI 13
(2) Consequence of the fuel failure(i) Fission Gas Release in RIA Tests
JAERI
Considerable fission gas release during RIA transient was observed.
The release correlates with fuel enthalpy and burnup.
14
0 10 20 30 40 50 60 700
5
10
15
20
25
Fuel burnup (GWd/t)
Fis
sion
gas
rel
ease
(%
)
PWR
BWR
Peak fuel enthalpy about 70 cal/g
Peak fuel enthalpy about 130 cal/g
0 50 100 1500
5
10
15
20
25
Peak fuel enthalpy (cal/g)
Fis
sion
gas
rel
ease
(%
)
PWR
BWR
Burnup about 60GWd/t
Burnup about 45GWd/t
5µm
20µm
(ii) Fuel Fragmentation
Fine fuel fragmentation occurred when rod failed.
Average size of the fragments was smaller in tests at higher fuel enthalpy (as small as 0.04 mm).
Thermal interaction between fragments and coolant caused water hammer in the capsule.
BWR fuel (61GWd/t) test at 377 J/g (90 cal/g)
JAERI
0
5
10
15
20
25
30
35
????
(%)
FK-6 FK-9W
eigh
t Fra
ctio
n (%
)
0
5
10
15
20
25
30
35
????
(%)
FK-6 FK-9W
eigh
t Fra
ctio
n (%
)3535
Average 43, 81µm
Diameter < 0.026 0.026 0.07 0.122 0.4 0.51 1.02 >2.02(mm) 0.07 0.122 0.24 0.51 1.02 2.02
0
5
10
15
20
25
30????
(%)
Wei
ght F
ract
ion
(%)
0
5
10
15
20
25
30????
(%)
Wei
ght F
ract
ion
(%)
Diameter < 0.026 0.026 0.07 0.122 0.4 0.51 1.02 >2.02(mm) 0.07 0.122 0.24 0.51 1.02 2.02
BWR fuel (61GWd/t) tests 548 377 J/g(131 90 cal/g)
15
Fuel Behavior Tests under Conditions Simulating BWR Power Oscillations without Scram
BWR fuel test
Burnup: 56 GWd/t4 power oscillationsPeak power: 48kW/mFuel enthalpy: 256 J/g (61 cal/g)
Burnup: 25 GWd/t7 power oscillationsPeak power: 95kW/mFuel enthalpy: 368 J/g (88 cal/g)
High power test
JAERI 16
0
10
20
30
40
50
0 10 20 30Time (s)
Pow
er (k
W/m
)
0
100
200
300
400
500
Fue
l ent
halp
y (J
/g)
0
20
40
60
80
100
0 10 20 30Time (s)
Pow
er (
kW/m
)
0
100
200
300
400
500
Fuel
ent
halp
y (J
/g)
Transient Behavior in Power Oscillation Tests
Clear sign of PCMI (Cladding deformation fuel enthalpy) No plastic nor ratcheting deformation of claddingNo DNB (departure from nucleate boiling) No failure
JAERI 17
Cladding (mid)
Water (top)
Rod power(relative)
0 10 20 30Time (s)
0.0
0.1
0.2
0.5
0.4
0.3
Cla
ddin
g el
onga
tion
(%
)
0
50
100
250
200
150
Tem
pera
ture
(?C
)
High power test (25GWd/t)
Claddingelongation
Cladding Deformation in Power Oscillation & RIA Tests
0 50 100 150 200 2500
1
2
3
4
5
6 0 200 400 600 800 1000
Peak fuel enthalpy (cal/g)
Cla
ddin
g el
onga
tion
(%
) RIA High power
BWR
High power test
BWR fuel test
Thermal expansion ofpellets (MATPRO)
Peak fuel enthalpy (J/g)
Cladding deformation comparable to RIA tests (by PCMI in the two types of transients)
JAERI 18
Fission Gas Releases in Power Oscillation Tests & RIA Tests
0 50 100 150 200 2500
5
10
15
200 200 400 600 800 1000
Peak fuel enthalpy (cal/g)
Fis
sion
gas
rel
ease
(%
)
Peak fuel enthalpy (J/g)
PowerOscillation
RIARIA test with sibling BWR fuel (FK-5)
Power oscillation test of BWR fuel
0
500
1000
1500
2000
0.0 0.2 0.4 0.6 0.8 1.0Relative radius
Tem
pera
ture
() Power oscillation test
RIA test
Lower fission gas release during the power oscillation test?Lower temperature at fuel periphery?Smaller heat-up rate
JAERI 19
Radial temperature distributions at time of enthalpy peaked (Calculated with FRAP-T6)
RIA Tests• Brittle cladding failure occurred in high burnup PWR and BWR fuel tests at
fuel enthalpies as low as 60 cal/g. • Same type of failure occurred in fresh PWR fuel rods with hydrided cladding.
The failure thresholds, however, was higher in fresh fuel tests than irradiated fuel tests, suggesting the irradiation effects for the cladding embrittlement.
• Recent RIA tests with transient cladding hoop strain measurementsuggested that the PCMI failure was caused mainly by thermal expansion of pellets. Contribution of fission gases to the failure seems limited.
• Considerable fission gas release and fine fuel fragmentation were observed in the tests. Consequence of the fuel failure would be influenced by these phenomena which should depend on fission gases and fuel morphology at high burnups.
Power Oscillation Tests• First two tests under conditions of BWR power oscillations without scram
were conducted in the NSRR.• Cladding deformation was caused by PCMI and was comparable to those
observed in RIA tests.• Fission gas release was smaller than that observed in RIA test at a
comparable fuel enthalpy.• One more test in FY 2002 is planned under a condition with expected DNB.
SummaryJAERI 20
Future plan to be continued
Future Tests on High Burnup Fuels
NSRR/RIA Tests• Failure thresholds and its consequences
•Japanese UO2 at 45-65GWd/t (Zirlo, MDA, NDA, Zry-2)•Japanese MOX at 30-45GWd/t (Advanced Thermal Reactor type Zry-2)•European* UO2 at 70-74GWd/t (Zirlo, MDA, NDA, Zry-2)•European* MOX at 49-78GWd/t (Zry-4, Zry-2)
• Tests at high temperature high pressure (HT Tests) conditions, in addition to roomtemperature conditions
Cladding Mechanical Testing• Ring tensile, tube burst, etc.
*in ALPS (Advanced LWR Fuel Performance and Safety Research) program sponsored by METI of Japan
MDA, NDA: Zr-Sn-Fe-Cr-Ni-Nb alloy developed by Japanese fuel vendors
Test fuel rod
Pressure suppression tank
Heater
T initial < 286 ? CP initial < 7 MPa
HT Test
JAERI 21
Test Type
2002 2004 2005 2006 20072003
RIA/RT Test
RIA/HT Test
UO2 Fuel
MOX Fuel
FY
Japanese PWR&BWR PWR 17x17 [60 GWd/t]
MDA, Zirlo, NDA
BWR8x8 [61 GWd/t]9x9 [45-65 GWd/t]
PWR 17x17 [70-74 GWd/t] MDA, Zirlo, NDA
BWR 10x10 [75 GWd/t]European (ALPS)
European (ALPS)
PWR 17x17 [59 GWd/t]BWR 8x8, 9x9 [49-78 GWd/t]
ATR[30-45 GWd/t]
NSRR Test Schedule
NS
RR
Shu
t Dow
n fo
r M
odifi
catio
nPower osc. test
JAERI 22
Eu
rop
ean
Fu
el
Shi
pmen
t to
Japa
n