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from the crack edges are observed. These two approximate theories are compared in the paper with some new exact solutions of the elastic wave equation.
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III
FOREWORD
Both OECD Nuclear Energy Agency (NEA) and 1AEA make full use of the tr'aditional methods of co-operatlon throuyh Working Groups and meetings. The 1AEA Worklng Group on Reliability of Reactor Pressurized Components as well as the CSN1 (OECD) Working Group on Pr~mary Circu 1 t Integrity (WG No.3) dec ided to organ ize a specialist meeting on defects detection and sizing owing to the importance of NDE both for quality assu- / ran ce in the manufactu re of nuclear components and for the safety of the operation of nuclear plants. A joint OECD-NEA/IAEA meeting has thus been organized at 1s- pra, Joint Research Centre of the CEC which is the Operating Agent of the PISC II programme, one of those major international cooperative actions aiming at NDE effectiveness assessment and improvement.
I
The present ted by the
proceedings include the papers as submit- authors. The conclusions of the sessions
I I I I I I I I I I
chairmen are added; these conclusions highlight the major points of interest and of discussion.
Acknoledgements go to the session chairmen for organi- zing so well several long sessions and producing con- clusions.
Serge CRUTZEN Chairman of the Meeting
IV
PROGI<AMME GROUP
Serge CRUTZEN (Chairman) NOT Section, Materials Science Division Commission of the European Communities, Joint Research Centre Gun the r'ENOL Kraftwerk Union AG, Dept. R Prof. D.G.H. LATZKO Dept. of Mech. Eng. Lab. for Thermal Power Engineering, Delft University of Technology Dr. R.W. NICHOLS Head, Ri.sley Nucl. Power Dev. Lab., UKAEA. Risley Andr'£:PROT D~pt. de Saret~ Nucl~aire, SAER
Commissariat i l'Energie Atomique, CEN/FAR
Dr. C.Z. SERPAN
Chief, Mat. Eng. Branch, Div. of Eng. Technology U.S. Nuclear Regulatory Commission Peter OLIVER Nuclear Safety DIvision OECD Nuclear Energy Agency Andre i SII\JEV Inter'national Atumic Ener'gy Agency, IAEA
I I I I I I I I I I I I
Chairman of the Meeting S"J.^ CI<LJTZEI\J,CEC,^ ..JRCIspra,^ NDT
Laboratories, I
I
l.
Organization of the Meeting Dr. M.P. MORETTI
CEC, JRC Ispra, Press and Public Relations
Tel. : (0332) 789889 Telex : 380042-380058EUR I I I I I I I
J.P, LAUf!AY
J.P. LIE TARO
A. LLJCIA
G. MAC1GA
F. MARCHINI
R. MARTINE LLI
H. MAURER
I-I.S. MAIER
H. MAYER
P. NAUCHE
.'^ , , ~!AI,(DONI
P ~.IICHOLS
M, ~IYMAN
r • NIXON
P. OLIVER
M. PAPPONt:TTI
J. P. PE LSENEER
J. PEREZ-PRAT
M. PLAGNARD
Y. PliAL.US
A. PROT VJ. f~ATHBE RG
S. REALE
G.P, REDONDI
V. REGIS
J. HE YI\JEI\I
A. RIMOLDI
f. I~OCE: F<SON
J. L. SA.RAIVA RAMOS
r, SASAI<I
E. t:;UINE I DER A.. ~JC!IOLZ /I,. S li'JE V G. SlT\ilIART J.A. TUvlPLE A. TIIOMAS F. TOI\lOLINI G. T()r~RIDA
A. TROYA
O. VAL KEJAE RV I
L. VENTKARAMAN
C. VINC/-IE
G. VOLTA
D. VEn~:jPEELT
B. WATf<lNS H. ~\IELJUOI~N II. wit:; n:NBE RG
M. ZAI\JOTTI
VI FF\AMATOME TracUonel
Jr~C Isp,.,a
Ef'IE LOCO
1st, Donegani
Er!E:.ACasaccia
CEC-DG XII
MPA, Un. of Stuttgart
1KE, Un. of Stuttgart
CEC DG X] I AT UKAEA R~JL TVO
UKAEA, SRD
OECD, NEA
Registro Navale
Ass.Vincotte
Tecnatorn
Bureau du Contr5le Constr.
CE TIM
CEA CEN/FAR
KWU
Univ. Fir'enze
CISE
ENEL CRTN
JRC Ispr'a
AGI\JI\JUCL.
UKAEA, RI\JL
1st. de Saldatura
1/- lL.fP
Br'owrtBoveri
lAEA Vienna
BI\JFL AE RE, Harwell
Framatorne
CISE
FIf\T TTG
1st. It. Saldatura
STL Bhabha AF~C JRC Ispl'a
JI~C Ispra
Ass. Vincotte
UKl\EA, HNL UNIT Insp. Co.Ltd. B,l\M
ENEA Bologna
Ft'ance
Belgium
CEC
Italy Italy Italy CEC
Fed. Rep. of Germany
Fed. Rep. of Germany
CEC
Italy
Un i ted Kingdom
Finland
United Kingdom
OECD
Ita 1y
Belgium
Spain
France
I=t'ance
France
Fed. Rep. of Germany
Italy Italy
Italy
CEC Italy
United Kingdom
f^1 ol'tugal
Japan
Fed. Rep. of Germany
Swi ze 1'1and
Un.ited I<ingdom
United Kingdom
1=1"'ance
Italy
Italy Italy Finland
India
CEC CEC Belg ium
United Kingdom
United Kingdom
Fed. Rep.of Germany
Italy
I I I I I I I I I I I I I I I I I I I
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VIr
CONTENTS OF VOLUME I
I
SESSION 1 OPENING REMARKS 1
I
I
G ..BISHOP
P. OLIVER
A. SINEV
(Director of the Ispra Establishment)
(NEA)
(IAEA)
3 5 7
I
SESSION 2 LATEST DEVELOPMENTS IN INSPECTION PROCEDURES
NEW TRENDS IN NDE TECHNOLOGY
9 I I I I I I I I I I I
2.1. Overview of German R&D programs
H. Bohn, G. Engl, M. Kr6ning
(Kraftwerk Union AG, Erlangen, FRG)
2.2. Le Nouveau Code Francais pour la Conception et la Construction des
Reacteurs a Eau Legere : les regles relatives aux methodes
de contr8le
J.P. Launay, (Framatome, France) and L. Valibus (EdF, France)
2.3. Developments in Ultrasonic Techniques in the United Kingdom
J.M. Farley, J. B. Dikstra
(Babcock Power Ltd, Research Centre, UK)
2.4. Research activities developed by ENEL-CISE on defect detection
alld sizing by acoustic emission and advanced ultrasonic
techniques
V. Regis (ENEL, Milano, Italy)
2.~. Defect Detection and Characterization - Some Experiences
L. Venkataraman
(Bhabha, Atomic Res. Centre, Bombay, India)
2.6. Application of ASME XI in Italy
L. Gentili (ENEL - DPT/SN, Rome, Italy)
G. Maciga (ENEL, DCO/LPC, Piacenza, Italy)
2.7. Views of the Marshall Committee
R. Nichols (UKAEA, RNL, UK)
1 1
37
49
65
91
103
1~
I
I SESSION^4
IX
ADVANCED TECHNIQUES - PART 2 301
I I I I I I 4.1. Defect detection and sizing using SAFT-UT. Operational Experiences J.L. Jackson (SWRI, USA) D.R. Hamlin (Electronic Systems Engineprlli~, U~A) 4.2. Developme~Lal techniques for ultrasonic flaw detection and characterization in stainless steel D.S. Kupperman (A.N.L., Argonne, USA) 4.3. AcoustIC emission monItoring during pressure vessel hydrotest F. Tonolini (CISE SpA, Segrate, MIlano, Italy) 4.4. Least squares pattern classification of acoustic emission signals for noise rejection A.C. Lucia, R. Brunnhuber (CEC, JRC, Ispra) L. Arienti (visiting fellow - CEC, JRC Ispra)
303
319
339
363
5.1. Djfficult~s dans la mesure des dimensions des d~fauts d~tect~s par radiographie P. Ruault (G.D.F., France) 5.2. Determination of mechanical stress by polazized shear waves and micromagnetJc methods E. Schneider, K. Goebbels, I. Altpeter, W. Theiner (IZFP, Saarbrucken, FRG) 5.3. Defect classification by multifrequency eddy current R. Becker, K. Betzold (IZFP, Saarbucken, FRG) 5.4. Use of the newest Eddy-Current inspection techniques and the resulting improvement in their predictive capacities A. Scholl, H. Ziegler (Brown Boveri, Baden, Switzerland)
I I I I I I I I I I I SESSION 5 ADVANCED TECHNIQUES - PART 3 381
383
397
399
413
r-- --- x
CONTENTS OF VO_UME II
I I I I SESSION 6 MODELLING OF ULTRASONIC PHYSICAL PHENOMENA 421 I 6.1. All improvement algorithm for the simulation of the ultrasonic inpection process M. Certo (CISE SpA, Segrate, MIlano, Italy) 6.2. Application of elastic scattering theory for smooth flat cracks to the quantitative prediction of ultrasonic defect detection and sizing J.M. Coffey, R.K. Chapman (CEGB, Manchester, UK) 6.3. Time of flight inspection Theory J.A.C. Temple (AERE, Har'well, UK) 423 r: 445
I I I I I SESSION 7 ReLIABILITY OF NDE 539 I 7 •.1. P,'ogres~', towards an understanding of reliability in NDE N.F. Hai'les (CEGG, Berkeley, UK) 7.c.. [cJdy Cur'r'ent s.ignal data bank of heat exchanger tube defects J.B. Perez-Prat, J.B. Fern&ndez, J.V. Fern&ndez (Tecnatom, S.A., Spain) 7.3. Caract&risation par leur fonction de transfert des composants du systcime de contrale par ultrasons R. Denis (CEe, JRC, Ispra) 7.4. Description de programme de caract~risation d'~quipement ul.trasonore A. Coquette, D. Verspeelt, Ph. Dombret (Association Vincotte, Belgium) 7.6. The PISC Parametric Studies on the effect of equipment characteristics on defect detection and sizing E. Borloo, I Bredael, (CEC, JRC lspra) 7.6. Statistical aspects of the evaluation of NDE reliability B. Hansen ISVC, Glostrup, OK) 541 563 575 589
633 I I I I I I I I
10.1. Conclusions of the IAEA internationaly symposium on
Reliability of Pressure Components, MPA, Stuttgart,
March -1983 (oral presentation only)
K. Kus'.;rnau
(MPA, Stuttgart, FRG)
10.2. Requirements for NOI reliability as a function
of the size and position of defects in RPVs
A. Lucia, G. Volta (CEC, JRC, Ispra)
10.3. The need for validat LOn of techniques and procedures
T. Cur'rie (HM Nucl. Inst. Insp., UK)
SESSION 10
SESSION 11
x:u
\
RELIABILITY OF COMPONENTS AND EFFECTIVENESS
OF NOE
CONCLUSIONS OF SESSION CHAIRMEN
789
791
793
823
831
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CONC LUS IONS OF SFSSION 2 833
CONCLUS IOf\lSOF SI::.SSION 3
835
CONC LU~3IONS OF SeSSION 4 842
CONe LU~:;IONS OF SLSSION 5
843 COf\JCLUSIONS OF Sl:S::iJON 6 (;
CONCUJSIOr\lS OF Sl-SSION (^) "7 (^) :-} (^845)
CONe UJ~:;1ON~3 OF SISSJON (^8 )
CONe UJ~31ONS OF Sl:SSION (^9 )
CONCLUS IONS (^) OF THE MEETING (^852)
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(4)
(3 )
q(y)," JJ J J(](y) ( 2)
~6f~ Since the transfer functions of the two transducers do not depend
Equation (3) can therefore be written in the form
behaviour.
The frequency response of transducers T E (Y), T R (V) can be introduced
into the model as experimental data obtained from their characterization or analytically generated by a proper model of their electromechanical
on the integration variables, they can be written out of the integral sign:
where }I is the ultrasound frequency, TE(Y), TR(V) are the t.ransfer
functions of the emitting and receiving transducers, respectively. The echo signal available at the receiving transducer output is
obtained by integrating (1) over the three surfaces under analysis
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In the time domain, function U(y) assumes the form
-«(t)=" V'J COSo(e tCOSa(a. cot;~ coS ~ .i.-.i. J It J} t f(l. )dll c:lri' cJ~ (5)
JJ 'l E It P ~ l' - .c -; e on 0 6'"p It 61 ~ 4l. where S stands for Dirac's delta function. The direct numerical integration of eq. (5) involves the discreti- zation of the three surfaces in many elementary small areas and the integral reduction to a summation of the contributions relevant to each combination of the small qreas of the three surfaces. The sizes of these areas must be sufficiently small to comply with the sampling theorem,
consequently the number of calculations to be performed increases beyond I
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times within acceptable limits.
a different approach was developed to reduce the computing
that permit the calculation of eq. (S) to be simplified. A typical assumption considers the defect in the transducer "far-field"; in this case the transducers are considered of point-like type and a suitable function describing the angular sensitivity of the transducers is introduced. This approach permit:; the reduction of integral (5) ex- tended to three surfaces to an integral extended to only the single surface of the defects, thus reducing the necessary calculations by a large extent. To overcome the limitation of operating in the transducer "far-fi.eld"
I I I I I I
acceptability. It becomes therefore necessary to introduce assumptlons
I 3. DEVELOPMENT OF THE ALGORITHM
I 3.1.^ Integration^ vs.^ the^ transducer^ surfaces
can be approximated with enough accuracy
and Dirac's delta function can be written as follows
(7)
(8)
M-{ (t)::: Jf~OSCl(E i COSo{R C05.... COS")( .i i. [it - FeT^ Fa) 01&: au; (6) 2 °e 0a. P e <. E R. ~~ If n cosotE+cos~ Expression ------------ 2 even for high values of the incidence angles by
where ~ denotes the convolution symbol. Equation (6) can therefore be rewritten in the form
Let us primarly consider the contribution relevant to, the reflection of a single infinitesimal area of the defect
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where ~. ., t.. are calculated with reference to the central point
l,J l,J
of the small area and S .. (t) is a trapezoidal function of time, defined
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by the distance of the reflecting points from of the four rectangle apices, see fig. 2, and whose area is equal to the area of th~ elementary rectangle. Function S. .(t) can assume either the form of a true trapezium
l,J
or that of a triangle or of a rectangle, in dependence on the relative position of the reflecting point vs the rectangular small area. In the
aim at further simplifying the calculation of c. l,J .(t) the rectangular
form wa$ always assumed for S. l,J .(t).
Convergence tests were carried out with reference to pulse-echo technique, shear wave transducer with 20x22 mm^2 crystal and sampling the time axis each 100 nS. The tests showed that it is possible to obtain consistent results by discretizing the transducer surface i.n a number of elements varying from 5x5 for distances from the reflecting point higher than the near-field length to 20x20 when the reflecting point is very close to the transducer (10~30 mm). In the same conditions, the direct numerical integration of eq. (9) would have required the subdivision of the transducer surfaces into not less than 4400 elements having a 0.
mm side. Since the determination of function S.. is very simple, it is possible
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to state that the reduction in the number of computations to be performed varies by a factor 10 to 40, whereas, if reference is made to the direct integration of the originary equation (6) the reduction factor turns out to be larger than 104 •
3.2. Integration vs. the defect surface
The integration vs. the defect surface is obtained by subdividing the same surface into elementary small areas; with reference to the center of gravity of each of them, a calculation is made of the contribution to the echo signal using the previously mentioned techniques and, finally, all contributions, weighted with the area value of the relevant elementary areas, are summed to obtain the total echo signal u(t). The discretization is of rectangular type and is obtained by superimposition on the defect of a variable-pitch grid; the grid is conveniently oriented, as roughly sketched in fig. 3. The side of the grid meshes are calculated in such a way that, when passing from a small area to an adjacent one, "the time
I
shift" of the corresponding echo signal does not exceed the sampling time interval. This procedure provides a minimization of the overall I number of the elementary areas. I
- MODELLING OF TRANSDUCER TRANSFER FUNCTIONS (^) I
account to other factors, such as static capacitance of the transducers,
tuning inductance, effect of the excitation circuit, connection cables,
The.overall transfer function of the emitting anA rece~ving transducer is analytically generated in the frequency range directly, the input data being the operating frequency and the bandwidth. The electromechanical properties of each transducer can be represented, in a first approximation, by means of an electric resonating circuit
L-R-C; if Y (^) o is the resonance frequency of the circuit and Q is the
Q-factor, then T(~) can be written as follows
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----^ -1^ ]^2 ;::;T;(v) {(v) J~ -t Q(1-~) Yo ~ modelling of the transfer function should give due
T(v)= [
A more qccurate
etc. Without going through a detailed analysis of the effect of these
factors, the following form was chosen for (^) I
T(v): [ 1 ,] 3 ( Jf;, + Q (1- fr,.) since the time wave form corresponding to (14) is quite similar to
those experimentally detectable.
I
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I s. EFFECT OF THE PERSPEX SHOE IN THE CASE OF ANGLED TRANSDUCERS I When angled transducers are considered, it is necessary to take
into account the effects due to the presence of the perspex shoe. In
the far-field, such effects can be reduced to an apparent reduction
in one of the two transducer sides, as shown in fig. 4.
This description of the presence of the shoe was adopted also for
the near-far field, where, however, its effect requires a more complex
description.
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