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International Workshop INFLUENCE OF ATOMIC DISPLACEMENT RATE ON
RADIATION-INDUCED AGEING OF POWER REACTOR COMPONENTS: EXPERIMENTAL AND MODELING
Ulyanovsk State University, Russia, 3 – 7 October 2005
MAIN PROGRAMS AND TECHNIQUES FOR EXAMINATION OF BEHAVIOUR OF THE WWER
HIGH-BURNUP FUEL IN THE MIR REACTOR
А.V. Burukin, S.А. Ilyenko, V.А. Ovchinikov, V.N. Shulimov
FSUE «SSC RIAR», Russia
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Programs and techniques for in-pile examination of the WWER
fuel are aimed at obtaining of experimental data to validate serviceability of the WWER fuel taking account of the following up-to-date trends: Increase of burn-up and extension of the reactor cycle; Introduction of maneuvering conditions;Observance of the up-to-date requirements established
for fuel behaviour under design-basis accidental conditions («Small LOCA», maximum design-basis accident, RIA)
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Performance of the WWER standard fuel under normal, transient and accidental operating conditions is simulated by conducting different tests including repeated irradiation and transient tests of full-size (FSFR) and refabricated (RFR) fuel rods as well as tests of the refabricated fuel rods under design-basis accidental (LOCA and RIA type) conditions and also tests of defective fuel rods.
A high neutron flux density and heat removal conditions allow the performance of experiments with fuel having a burnup of ~ 50...80 MWd/kgU at a linear power (LP) of ~ 50…100 kW/m.
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Parameter WWER-1000 MIR Maximum LP, kW/m 44.7 Higher values are possiblePressure, MPa Up to 17.7 ProvidedCoolant temperature inlet/outlet, оС 290…340 ProvidedWater-chemical conditions Boric acid concentration, g/kg Gas content in the coolant at STP, cm3/kg О2 Н2
Ammonia-boric-potassiumUp to 10
0.005…0.0525…50
ProvidedUp to 10*
ProvidedProvided
Coolant velocity, m/s 5.7 ProvidedFuel burnup, MWd/kgU ~ 55 Up to 85…100Determination of the moment of failure Impossible PossibleAcceleration of burnup processes,increase of LP and cycle number
Impossible Possible
Intermediate control of fuel rod states No Possible in the pool and shielded hot cell
Change of parametersof water-chemical conditions
No Possible
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Comparison of the main fuel testing conditions of the MIR loop facilitieswith operating conditions of the WWER-1000 fuel rods
The MIR reactor is a channel-type, pool-type and beryllium-moderated reactor. It has several high-temperature loop facilities, which provide necessary coolant parameters for WWER fuel testing.
*- 4…5 g/kg - average level of index for WWER water-chemical conditions for long-term testing
Lay-out of the WWER experimental fuel rods in irradiation rigs FSUE SSC RF RIAR 5
62.2
12.75
12.75
60
~300
mm
50
0 m
m
500
mm
640
mm
64
0 m
m
460
mm
49
0 m
m
200
mm
200
mm
Cor
e he
ight
500
mm
50
0 m
m
Core average
plane
WWER fuel rod dummy
(fuel column)
FSFR (fuel column)
RFR
(fuel column)
Square 42
Types and characteristics of gauges for irradiation rigs and fuel rods Parameter Design type Measurement
rangeError Dimensions, mm
Diameter Length
Temperature of coolant and fuel rod cladding
Chromel-alumel thermocouple,cable-type
Up to 1100 оС 0.75% 0.5
Fuel temperature
Chromel-alumel thermoprobe, cable-type
Up to 1100 оС 0.75% 1…1.5
Fuel temperature
Thermoprobe WRe-5/20,casing Мо + ВеО
Up to 2300 оС(up to 1750 оС*)
~ 1.5% 1.2…2
Cladding elongation
LDDT (0…5) mm ± 30μm 16 80
Diameter change
LDDT (0…200) μm ± 2μm 16 80
Change of gas pressure in fuel rod
Bellows + LDDT (0…20) MPa ~ 1.5 % 16 80
Neutron flux density (relative units)
Neutron detector (ND)(Rh, V, Hf)
1015…1019
1/m2s ~ 1% 2…4 50…100
Volume steam content in coolant
Cable-type 20…100% 10% 1.5
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* - experimental data for high-burnup fuel rods
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Repeated irradiation of refabricated and full-size fuel rods
Tests of theWWER high-burnup fuel rods in the
MIR reactor
Power ramping (RAMP) and stepwise
increase of power (FGR)
Testing under design-basis RIA conditions
Testing under fuel rod drying, overheating
and flooding conditions (LOCA)
Testing under power cycling conditions
Testing of defective fuel rods
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The test objective is to determine the change of fuel rod state under burnup increase conditions at a specified power level and to prepare fuel rods with increased burnup for special tests (RAMP, LОСА and RIА).
Repeated irradiation of refabricated and full-size fuel rodsfrom spent WWER fuel assemblies up to high-burnup values
Type of fuel rod
Number of fuel rods
Length of fuel column of fuel
rod, m
Initial burnup, MWd/kgU
Final burnup, MWd/kgU
Maximum LP, kW/m
Repeated irradiation test No. 1WWER-1000 2 3.53 49…50 62…63 18…30WWER-1000 1 0.95 49 63 19…31WWER-440 2 2.42 61 72 17…28WWER-440 1 0.94 60 72 19…31
Repeated irradiation test No. 2WWER-1000 5 3.53 53…55 74…75 18…24WWER-1000 3 0.4 53…58 74…78 18…24
General data on repeated irradiation testsof the WWER fuel rods in the MIR reactor
Designation Number
of fuel
rods
Burnup,
MWd/kgU
Initial LP,
kW/m
LP increment
on ramping,
kW/m
Max. LP
increase rate,
kW/m/min
FGR-1 6 ~ 49…61 9…12 15 + 6 + 11 0.3
FGR-2 6 ~ 49…59 12…15 8 + 5 + 7 + 9 0.3
FGR-3 6 ~ 56…61 12…17 9 + 9 0.1
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Testing under power ramping conditions
The tests aimed at determination of the effect of power ramping parameters (RAMP) (including FGR) on serviceability of fuel rods with different burnup.
General information about FGR tests with the WWER fuel rodsin the MIR reactor
Range of burnup and LP amplitudes in the course of RAMP testsof the WWER fuel rods in the MIR reactor
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0102030405060708090
100110120
0 10 20 30 40 50 60 70
LP,
kW
/m
Burnup, MWd/kgU
○ Tight WWER-1000 fuel rods (E110 (Zr-1%Nb)) Tight WWER-1000 fuel rods (E110 (Zr-1%Nb)) with cracks on the cladding ◊ Tight WWER-1000 fuel rods (E635) ♦ Failed WWER-1000 fuel rods (E635) ∆ Tight WWER-440 fuel rods Tight WWER-440 fuel rod with cracks on the cladding▲ Failed WWER-440 fuel rod □ Combined fuel rod (cladding - E110 (Zr-1%Nb), fuel - France) ■ French fuel rods (cladding - Zr-4F) Damage threshold of the KWU fuel rods (Germany) Damage threshold of the KEP fuel rods (Japan)
Testing under power cycling conditions (CMP-1, CYCLE 1, CYCLE 2)
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The objective of testing was to obtain experimental data that characterize a change in the cladding strain, gas pressure in the free volume of a fuel rod, fuel temperature in course of power changing and fuel rod state after testing.
Type of fuel rod
Number of fuel rods
Instrumentation
Burnup, MWd/kgU
Initial LP,
kW/m
LP increment during
cycling, kW/m
LP increase rate,
kW/m/min
WWER-440 1 РF + L+ D 51 19 10 0.3
WWER-440 2 Т 51 19 10 0.3
WWER-440 3 --- 51…60 15…19 8…10 ~ 0.3
The main data of the CMP-1 test
Type of fuel rod
Number of fuel rods
Instrumentation
Burnup, MWd/kgU
Max. initial LP,
kW/m
LP increment during cycling, kW/m
Max. LP increase
rate, kW/m/min
CYCLE-1 test
WWER-440 4 T, T 52…61 18 11 ~ 0.9
CYCLE-2 test
WWER-1000 2 Т, L 49…50 21; 21* 9; 21* 0.6; 0.9*
WWER-1000 2 РF, L 49…50 21 9 0.6
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General information about the CYCLE-1 and CYCLE-2 tests
*- maximum values of initial LP, increment and power increase rate under ramping conditions after maneuvering
The main examination tasks are as follows: Formation of parametric dependences of fission product release (different physical-
chemical groups and separate nuclides) on fuel burnup, power level, type and size of the cladding and location of the cladding defect;
Definition of kinetics and features of the cladding defect evolution including generation of the secondary defect
Testing of defective fuel rods with high-burnup FSUE SSC RF RIAR 13
Equipment Measurement results Final dataStandard leak-control system of fuel rod cladding of a loop facility
Logging intensity of n–radiation of loop facility coolant
Change in the release of delayed neutron carriers into coolant
Special sampling system.On-line gamma spectrometer
Nuclide activity in the coolant measured directly in the pipeline of a loop facility and in the coolant samples with separation of liquid and gas phases
Fission product release rate into the coolant through the cladding defectFuel wash-out rate by coolant coming in contact with fuel in the defect area
Standard sensors of a loop facility
Coolant parameters:flow rate, pressure and temperature.Power of an EFA
Coolant parameters: rate, pressure, and temperature. Local power, cladding temperature, heat removal mode
Types of experimental data obtained during examinationof fission product release into coolant
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Registration of the coolant n-radiation in the loop facility
Registration of the coolant γ- radiation
On-line gamma spectrometer on the control
Special coolant sampling system
New equipment
Cross-section of irradiation rig for testing defective fuel rod
Lay-out of the special equipment for determination of fission product release into the coolant of the loop facility primary circuit in the MIR reactor
Reference fuel rods
Defective fuel rod
381
Testing under fuel rod drying, overheatingand flooding conditions (LOCA)
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The objective of the tests is to verify or refine serviceability criteria of fuel
rods and fuel assemblies, determine ultimate parameters, which allow
the core disassembling after operation under deteriorated heat transfer
conditions, and to obtain data for code verification and improvement.
Testing of the WWER fuel assembly fragments under «Small
LOCA» conditions was performed in accordance with a special program
that provided a wide range of environmental conditions.
Experiment
Composition, number and
burnup of fuel rods in EFA
Pressure in the
primary circuit of
a loop facility,
MPa
Implemented temperature
range, оС
Drying duration,
min
Exposure at max.
temperature, min
Fuel rod state
Unirradiated
fuel rod
Fuel rod with
burnup, MWd/kgU
Tight Failed
Experiments at increased pressure in the primary circuit of a loop facility (cladding compression)SL-1 18 - 12 530…950* 72 72 +
SL-2 19 - 12 Up to 1200 100 3 +
SL-5 6 1/52 4.9 750…1250 40 2 +
SL-5P 6 1/49 6 700…930 40 40 +
Experiment at decreased pressure in the primary circuit of a loop facility (cladding swelling)SL-3 19 - 4 650…730 25 25 +
The WWER-1000 fuel assembly fragments were tested in the SL-1, SL-2 and SL-3 experiments; the WWER-440 fuel assembly fragments were tested in the SL-5 and SL-5P experiments.
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The main parameters of «Small LOCA» experiments
*- short-term duration, non-instrumented corner fuel rod
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Testing of the WWER-1000 fuel assembly fragmentunder maximum design-basis accidental conditions
These tests were aimed at obtaining information about the behaviour of the fuel rod bundle and also data for codes of fuel rod thermomechanical state and for the estimation of radiation consequences of cladding failure.
1, 3, 4, 6, 8, 12, 18 – unirradiated and non-instrumented fuel rods;5, 11 - unirradiated fuel rods instrumented with one thermoprobe in the fuel;2, 10, 17, 15 – unirradiated fuel rods instrumented with three thermoprobes on the cladding;7, 9, 13 – unirradiated fuel rods instrumented with PF and one thermoprobe on the cladding;14, 16 – non-instrumented refabricated fuel rods;19 – refabricated fuel rod instrumented with one thermoprobe in the fuel (Numerals in figure correspond to cell numbers)
Location of fuel rods and gauges in the EFA for «Large LOCA» test
9
16
17
10
19
15
5
6
8
7
18
11
4
14
13
12
3
2
1
I - evaporation conditions (up to 5 hours); II – exposure of fuel rod cladding at drying temperature (150…250 s); III - (180…240 s); IV - (120…150 s); V - (60…120 s) –
maximum design-basis accidental conditions (II stage) (Ts - saturation temperature)
Temperature scenario of «Large LOCA» test
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200300400500600700800900
-300
-200
-100
0 100 200 300 400 500 600Time, s
Tem
pera
ture
of f
uel r
od c
ladd
ing,
оС
I
II
IVV
III
Тs
up to 5 hours
Temperature range of test
A program and technique for testing in the MIR loop facilities were developed to obtain experimental data on behaviour of high-burnup fuel rods under design-basis RIA conditions. In the MIR loop channel it is possible to provide rated LP and parameters of the WWER-1000 primary circuit coolant as initial ones, the fuel rod operating conditions being simulated in full-scale.
FSUE SSC RF RIAR 19Testing of the WWER-1000 high-burnup fuel rods
under design-basis RIA conditions
Technological parameters of the WWER-1000 primary circuitPressure, MPa 15.7Coolant temperature, оС up to 290Coolant velocity, ms up to 6Initial LP, kWm up to 25
Parameters of the neutron power impulseImpulse rise time, s 0.5…1.0Impulse amplitude, relative units 3.5…4Impulse half-width, s 1.5…2Shape of neutron power impulse triangular or trapezoidInitial fuel enthalpy, cal/g (kJ/kg) 60…70 (251…293)Fuel enthalpy increment, cal/g (kJ/kg) up to 100 (up to 419)
Simulated parameters
FSUE SSC RF RIAR 20Impulse shape in the MIR reactor
( - exposure time at maximal LP)
012345678
0 2 4 6 8 10Time, s
Ene
rgy
rele
ase,
rel
ativ
e un
its
12
34
1.0E+51.5E+52.0E+52.5E+53.0E+53.5E+54.0E+54.5E+5
0 5 10 15 20Time, s
Ent
halp
y, J
/kg
Mean radial fuel enthalpy1 - = 0.5s; 2 - = 0.75s; 3 - = 1s; 4 - = 1.25s
1
2
34
200
600
1000
1400
1800
2200
0 5 10 15 20Time, s
Tem
pera
ture
, о С
Temperature in the center of the fuel column1 - = 0.5s; 2 - = 0.75s; 3 - = 1s; 4 - = 1.25s
ConclusionsThe in-pile examination programs and techniques of the WWER fuel presented in the paper allow obtaining of experimental data on the high-burnup fuel behaviour under different operating conditions. These data can be used for:Checking the conformity of the WWER fuel with the licensing
requirements involving the majority of criteria;Estimation of the radiation consequences as a result of cladding
failure;Checking and updating of calculation codes;Estimation of the fuel rod state
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