Transcript pps

JSC “State Scientific CenterResearch Institute of Atomic Reactors”
Express diagnostics of WWER fuel rods at
nuclear power plants
S.V.Pavlov, S.V.Amosov, S.S.Sagalov, A.N.Kostyuchenko
8th International Conference on WWER Fuel Performance,
Modelling and Experimental Support
26 September – 04 October 2009, Helena Resort near Burgas, Bulgaria
CONTENTS
INTRODUCTION
1. Ultrasonic testing of failed fuel rods (FR) in
WWER fuel assemblies (FA)
2. Eddy current testing of FR claddings
3. Method of determination of the diametrical fuel-
cladding gap
4. Method of oxide film thickness measurement on
the FR cladding outer surface
CONCLUSION
2
INTRODUCTION
1.
The efficiency of technological support for standard fuel
operation and new fuel introduction depends on the
completeness of irradiated fuel data in many respects as
well as on the rapidity and cost of such data obtaining.
2.
In order to increase the comprehensiveness of primary
data on fuel assemblies and fuel rods immediately after
their removal from the reactor, inspection test facilities
are widely used for these purposes. The inspection test
facilities make it possible to perform non-destructive
inspection of fuel in the NPP cooling pools .
3.
Specifically, non-destructive inspection of fuel rods at the
inspection stands is conducted by different optical,
ultrasonic and other methods.
3
INTRODUCTION
4.
For inspection of the WWER-1000 fuel rods, methods of
ultrasonic testing of failed fuel rods and eddy current
testing of FR claddings have been developed and proved.
These methods are used at the stands for inspection and
repair of TVSA at the Kalinin and Temelin NPP.
5.
Method of determination of a diametrical fuel-cladding
gap and an electromagnetic method of the oxide film
thickness measurement on the FR cladding outer surface
have been successfully used at RIAR for examination of
irradiated WWER fuel for many years. These methods
could be easily accommodated for underwater operation
of the inspection stands.
4
5
Ultrasonic testing of failed fuel rods
Probe
Fuel
rod
Principle of method operation
а
b
Oscillogram of tight (а) and failed (b) fuel rod
Water
АT АF =const expV S(z)
where:
V – volume of water in the cladding-fuel gap;
S z  – average area of the cladding-fuel gap for the
segment of fuel rod filled with water
Ultrasonic testing of failed fuel rods
Method sensitivity and results of its validation
Method validation
А F /А T 1.2
1.0
0.8
0.6
0.4
0.2
0,0
0
0,0
0.1
0.2
0.3
0.4
V , cm3
АF АT = exp -17,5 V 
1. 8 leaking
WWER-440 and
WWER-1000 FAs
with a burnup of
13.8 to 37.5 MW
·day/kgU were
examined.
2. All failed fuel rods
were correctly
identified.
6
Ultrasonic testing of failed fuel rods
Special manipulator
1-rod; 2-frame; 3-spring; 4-ultrasonic probes; 5-guiding pins
7
Ultrasonic testing of failed fuel rods
Main window of computer program
8
Eddy current testing
Position of the
eddy current probe
and fuel rod
9
Signal of artificially applied defects
Characterization of the artificially applied defects
Defect
No.
1, 4
Defect description and its nominal dimensions
External blind hole 0.7 mm in diameter, 0.3 and
0.5 mm deep, respectively
2, 3
External circular mark, 0.06 and 0.10 mm deep,
0.08 and 0.14 mm wide, respectively
5, 6, 7, 8 Through hole, 0.4, 0.8, 1.5 and 2.5 mm in
1-eddy current probe body;
diameter, respectively
2-measuring coil;
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Internal circular mark, 0.20 mm deep, 0.25 mm
3-container for fuel rod;
wide
4-fuel rod
10
Eddy current testing
Amplitude, V
Examples of method application
3
2
1
0
-1
-2
-3
1
0
500 1000 1500 2000 2500 3000 3500 4000
Coordinate, mm
а
b
c
Results of the eddy-current defectoscopy of the FR
cladding (а), outer appearance (b) and cross-section of
the cladding with part-through debris-defect: 1-signal of
the debris-defect
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Eddy current testing
Amplitude, V
Examples of method application
5
3
1
2
1
-1
-3
-5
0
500 1000 1500 2000 2500 3000 3500
а
Coordinate, mm
b
c
Results of eddy-current defectoscopy of the defect fuel rod:
а-eddy-current diagram; b – appearance of the debris-defect;
c-cladding microstructure in the region of the secondary
defects; 1-signal of the debris-defect; 2-signals of the
secondary internal defects
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Eddy current testing
Registration of local changes of FR cladding diameter
Formation of goffers
Diameter, mm
Results of the FR cladding testing
1-cladding; 2-fuel pellet; 3-goffers
9.12
9.1
9.08
9.06
9.04
9.02
9
0
Magnitude of the eddy-current
signal against fuel burnup
500
1000 1500 2000 2500 3000 3500 4000
Amplitude, rel.units
Coordinate, mm
5
4
3
2
1
0
-1
-2
0
500 1000 1500 2000 2500 3000 3500 4000
Coordinate, mm
Method of determination of the cladding - fuel gap13
Method principle
Typical diagram
“force-deformation”
Scheme of the facility
1
4
5
8
2
7
6
P
“X”
“Y”
3
P
1-fuel rod; 2-loading pin;
3-load sensor; 4-displacement transducer;
5-bellows; 6-charge amplifier;
7-amplifier; 8-analog-to-digital converter
Method of the cladding - fuel gap determination
Non-destructive measurement results compared to the optical
metallographic examination results
 r ( Z i , )
minr (Z, )(a,b)
minr (Z,   )(a,b)
r ( Zi ,   )
ND i (a,b) = minr (Zi , i )(a,b)  minr (Zi , i  )(a,b)
MG Zi , i  = r (Zi , i ) r (Zi , i  )
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Method of the cladding - fuel gap
determination
15
200
150
240
100
50
0
0
50
100
150
MG)min, m m
ND, mm
150
Diametrical gap, µm
MG)max, m m
Method testing
Initial gap
200
160
120
80
40
0
0
100
5
10 15 20 25 30 35 40 45 50 55 60
Burnup, MW·day/kgU
50
0
0
50
100
150
ND, mm
- results of non-destructive measurement
- results of optical metallographic
measurement
Method of oxide film thickness measurement
on the FR cladding surface
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Scheme of the facility
1-fuel rod;
2-eddy-current probe;
3-signal amplifier;
4-signal processing unit;
5, 6, 7-stepper motors;
8, 9-stepper motor
controller;
10-computer.
Method of oxide film thickness measurement
on the FR cladding surface
17
Results of method testing with the use of WWER fuel rods
Oxide film thickness versus burnup
Comparison between the
measurement results and the results
of FR cross-sections metallography
40
10
Measured data,
µm
Oxide film
thickness, µm
12
8
6
4
2
30
20
10
0
0
0
20
40
60
Burnup, МW day/kgU
Alloy E110
WWER-440 ( - measurement, - metallography),
WWER-1000 ( - measurement, - metallography).
0
10
20
30
40
Optical metallography data,
µm
- alloy E110
- alloy E635
CONCLUSION
1.
The ultrasonic testing of failed fuel rods inside the
fuel assembly was developed for stands of inspection
and repair of TVSA WWER-1000 for the Kalinin
NPP and Temelin NPP.
2.
This method was tested for eight leaking fuel
assemblies WWER-440 and WWER-1000 with a
burnup of ~14 up to 38 MWday/kgU. The
ultrasonic testing proved its high degree of
reliability and efficiency.
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CONCLUSION
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3.
The defectoscopy by means of the pulsed eddy-current
method was adapted for the stand of inspection and
repair of TVSA WWER-1000 for the Kalinin NPP. This
method has been used at RIAR as an express testing
method of FR claddings during the post-irradiation
examinations of fuel assemblies WWER-440 and WWER1000. This testing method was used for examination of 47
spent WWER fuel assemblies in total. But there were 16
failed spent fuel assemblies among them .
4.
Methods of oxide film thickness measurement and fuelcladding gap measurement in the WWER fuel rods have
been successfully used for examination of the WWER fuel
in hot cells. They can be easily adapted for use under
water and can be recommended for adoption at stands of
inspection and repair of TVSA WWER-1000
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THANK YOU FOR ATTENTION!