ML19343A074
| ML19343A074 | |
| Person / Time | |
|---|---|
| Issue date: | 07/29/1980 |
| From: | NRC OFFICE OF STANDARDS DEVELOPMENT |
| To: | |
| Shared Package | |
| ML19343A076 | List: |
| References | |
| RTR-REGGD-1.150, TASK-OS, TASK-SC-705-4 REGGD-01.XXX, REGGD-1.XXX, NUDOCS 8009110362 | |
| Download: ML19343A074 (37) | |
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U.S. MUCLEAR RECULATORT COMil5510N My 29,1980.
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OfflCE OF STANDARDS DEVELOPMENT Divisiosi 1 i DRAFT RECT 1AIORY CUIDE AND VALUE/lHPACT 51AILHENT Task SC 705-4 ;
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ULTRASONIC IE511NG OF REAC10R VE5SEL WELDS DURING INSERVICE EXAMINA110N A.
INIR00U0110N t
i Criterion 1, " Quality Standdrds and Records," of Appe A, " General Design Criteria for Nuclear Power Plants," to 10 CTR Par 0,
estic Licensing of Produ: tion and Utilization Facilities "
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in part, i;;
m that components important to safety be tested to it andards commen-C surate with the importance of the safety functioni erformed. Where C
generally recognized codes and standards are u codes and standards
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must be evaluated to determine their adequ ficiency and must be
>.a supplemented or modified as necessary to ns uality product in keeping l
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with the required safety function. Crit urther requires that a quality assurance program be impleme der to provide adequate assur-W ance that these components will r ly perform their safety functions
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and that appropriate records of et ting of components important to safety i
l be maintained by or under t f the nuclear power unit licensee throughout the life of the i t.
Section 50.55a, " Codes tandards," of 10 CfR Part 50 requires, in part, that s'tructures, systems, and components be designed, fabricated, erected, construct sted, and inspected to quality standards commensurate with the importan h safety function to be performed.,Section 50.55a
!y further requ a SME Boller and Pressure vessel Code (ASME B1PV Code) heettherequirementssetforthinSectionXI,"Rulesfor Class I c n
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Inservic e on of Nucledr Power Plant Components," of the ASHL Code.
~m ooo this repistory pide e.d the assectated vat /i. pact state c.: are bel.g ess.ed I. draf t for. to la.elee O
the pubite le the early steps of the development of a regulatory posttlee la tkle area. 3 hey have met O
received complete statt review have met been reviewed by the hKC Replatory Regelresents Review Commit.
I*e. and do not represent an ef fIctal NaC staf f pestilen.
>Q Public cosaeets are belag solicited on both deaf ts, the golde (including any esplementallen schedule) and f"
the valwe/ impact statement. Comanents en the esfue/ impact statseent should be accompanied by suppee ttog data. Comments en both draf ts should be sent to the secretary of the (essetssten, u.s. Reclear Replatory QhH Consmission. Washington, D.C. 2055s. Atteatten: Dodelleg and service tranch. by ggg lgfg 4
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Requests for slagte copies of issued goldes and draf t pides (which may be eepeeducedt er fee placement en O
se automatic distelbetten list for slagte copies of future goldes and draf t gvIdes is specific divistens M
g shewld be sede in arltlag to the U.s. Nuclear Regulateep Commissten. Maskington, D.C. 20555. Attentlen:
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Director. Division of techalcal lafsemation and Occuneat Centrol.
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Criterion XII, " Control of Measuring and Test Equipment,* of Appen-I dix B, " Quality Assurance Criteria for Nuclear Power Plants and fuel l
Reprocessing Plants," to 10 CTR Part 50 requires, in part, that measures I
be established to ensure that instruments used in activities affecting
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quality are properly controlled, calibrated, and adjusted at specified periods to maintain accuracy within necessary limits.
Criterion XVil " Quality Assurance Records," of Appendix B requires 4 I
in part, that sufficient records be maintained to furnish evidence of activities affecting quality. Consistent with applicable regulatory requirements, tte applicant is required to establish requirements concerning record retention such as duration, location, and assigned responsibility.
this guide describes procedures acceptable to the NRC staff on an interim basis for implementing the above requirements with regard to the preservice and inservice examination of reactor vessel welds in light-water-cooled nuclear power plants. lhe scope of this guide is limited to reactor vessel welds and does not apply to other structures and componer.ts such as piping.
B.
Ol50tlS$10N Reactor vessels must periodically tie volumetrically examined according to Section XI of the ASHE Code, which is incorporated by reference, with NRC staff modifications, in $50.55a of 10 CFR Part 50. lhe rules of Sec-tion XI require a program of examinations, testing, and inspections to
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evidence adequate safety. Io ensure the continued structural integrity of reactor vessels, it is essential that h ilaws he reliably detected and I
evaluated. It is desirable that results may be compared from one ult asonic testing (Ul) examination to the other so that flaw growth rates may be estimated. Lack of reliability of ui examination results is partly due to the reporting of ambiguous results. Reporting of UI indications as recom-mended in this guide will help to provide a means for assessir.g tie ambiguity of the reported data.
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k' Operating and licensing experience ' ' and industry tests have P Delete (ThishasbeeninsertedinB.7) indicated that UI procedures that have been used for examination may not be adequate to consistently detect and reliably characterize flaws durihg inservice examination of reactors. This lack of reproducibility of location and characterization of flaws has resulted in the need for additional examina-
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tions and evaluations with associated delays in the Ilcensing process.
1.
INSTRUM[Mi PERFORMANCE CHfCES
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This guide gives recossendations for recording the characteristics of the UI,emanination system. This information can be of significance in later i
analysis for determining the location, dimensions, orientation, and growth ra(eo Haws.
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Determinations for " Frequency Amplitude Curve" and " Pulse Shape
- recommended System performance checks to determine the characteristics of the UT sys-in Positions C.I.3 and C.I.4 may be made by the licensee's examination agency tem should be per formed at intervals close enough that each UT examination by the use of any of the common industry methods to measure these parameters may be correlated with particular system gerformance parameters to help com-as long as it is adequately documented in the examination record. These measure-pare results. These determinations will help make it possible to judge ments may be performed in the laboratory, before and af ter each examination, j
whether dif ferences in observations made at dif ferent times are due to changes provided the identical equipment combination ti.e., instrumentation, cable, in instrument characteristics or are due to real changes in the flaw size and and search unit) is used durlog examination.
characteristics.
v These determinations are to aid third party evaluations when different equipment is used to record indications on subsequent examinations, and are 2.
CALIBRATION not intended to qualify systems for use.
According to Appendix i Article I, 1-4230,Section XI of the ASNE
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1.1 Pulse shape Code, 1974 edition, instrument calibration for performance characteristics lhe intent of Position C.I.4 is to establish the instrument pulse shape (amplitude linearity and amplitude control linearity) is to be verified at In a way that actual values of pulse length and voltages can be observed on an i
oscilloscope. The calibrated time base does not necessarily have to follow 3
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the OAC time base but may be chosen to suitably characterize the initial pulse.
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Pulse shape record will assist in analyzing potential differences in flaw 1
2" Summary llatch Nuclear Plant Unit 1 Reactor Pressure Vessel Repair," 1972 l
Georgia Power Company.
response between successive examinations (Is it flaw growth or system change).
3" Summary of the Detection and Evaluation of Ultrasonic Indications - Edwin Pulse shape is best determined by using a high Impedence oscilloscope llatch Unit 1 Reactor Pressure Vessel,* January 1972, Georgia Power Company.
with the transducer disconnected from the Instrument.
y Round robin tests conducted by the Pressure Vessel Research Committee (PVRC) of the Welding Research Council for Ui cf thick section steels.
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the beginning of each day of examination. Requirements in Article 4, Sec-tion V, 1977 edition, which is referenced by Section XI, for the periodic 3
check of instrument characteristics (screen height linearity, amplitude l
control linearity, and beam spread measurements) for UI examination of reactor pressure vessels have been relaxed. Ihis periodic check has been extended from 1 day to a period of extended use or every 3 months, whichever is less.
This change has not been justified on the basis of statistically significant field data. Stability of automated electronic equ;, ment is dependent on many factors, and the ASME Code has no qualit'y standards on the components of these systems. Until stability of performance of UT systems can be ensured by the introduction of quality standards for all components, it is not reasonable to increase the period between calibration c. hecks. Therefore, recommendations have been made to check instrument characteristics more frequently than specified in the ASME Code.
Requirements of Appendix I, Article I, 1-4230,Section XI of the A5MC i
Code, 1974 edition, state:
" System calit, ration shall be checked by verifying the distance-amplitude correction curve (1-4420 or I-4520) and the sweep range calibration (1-4410 or I-4510) at the start and finish I
of each examination, with any change in examination personnel, j
and at least every 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> during an examination."
In the 1911 edition, these requirements were changed. According to Article 4 (I-432.1.2),Section V of the ASHE Code, 1977 edition, the follow-ing applies:
"A calibration check on at least one of the basic reflectors in l
the basic calibration block or a check using a simulator shall be made at the finish of each examination, every 4 hr. during the examination and when examination personnel are changed."
.I lhis requirement has several minor deficiencies, including the following:
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a.
Calibration check is now required on only one of the basic reflectors.,i As a result, the accuracy of or.ly one point on the Olstance-Amplitude Correction (DAC) curve, and s,ot the accuracy of three points as previously required, is checked. Ihis alteration would permit the instrument drift for other metal path distances to gu unnoticed, which is not desirable.
b.
The change allows a one point check by a mechanical or electronic I
simulator instead of a check against the basic calibration block. A mechanici e
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sui'ered by the instrument. Since error band value depends on these parameters, it would be advisable to assure, through recording instruments, that the EBS
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was not subjected to higher temperatures (container lying in the sun) and shock (container dropped) during transport than served as a basis for defining the error band.
Use of electronic simulators would be admissible if these can check the calibration of the UT system as a whole and the error band introduced by their use can be relied on and taken into consideration.
d.
Static versus dynamic reflector responses With some automated systems, the OAC curve is manually established by maximizing the signal by optimizing the transducer orientation toward6 the call W oon holes. Subsequently, detection and sizing of flaws is on the basis of si %als received from a moving transducer where no attempt is made (or it is not,Msible) to maximize the signal even (cr the significant flaws. This procedure ney;.ds several sources of error introduced due to the possible variation in signal strength caused by:
a.
Olfferences between the maximized signal and nonsaximized signal, b.
Loss in signal strength due to the separatf an of the transducer from the metal surface because of the viscosity of the coupling medium (planing effects).
c.
Variation in contact force and transducer coupling ef ficiency.
d.
Loss in signal strength due to structural vibration effects in L '
moving transducer mount and other driving mechanisms.
loss in signal strength due to the tilting caused by the mounting e.
arrangement in some transducer mounts.
Because of the above, it would be advisable to establish the DAC curve under the same conditions as those under which scanning is performed to obtain data for detection and sizing. It would be acceptable to establish a DAC curve by maximizing signal strength during manual scans when signals are also maximized for flaw sizing. Ilowever, it would not be advisable to use manually maximized signals to estabitsh the OAC curve when data is obtained later by mechanized transducers (where signals cannot be maximized) for the detection and sizing page 5.
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of flaws without adjustment for the potential error introduced. In these situa-tions, an acceptable method would be to establish DAC curves using moving transducers or establish correction factors which may be used to adjust signal strength, it would be advisable to use care and planning in establishing correc-tion factors. For example, establishing a ratio between a dynamic and static mode under laboratory conditions using a precision transducer drive and stiff I
mounting may have very little in common with the transducer mounting and traverse f
conditions of the actual examination set up.
If correction factors are to be 8
used, it would be worthwhile to build either full-scale mockups or consider the variation of all the important parameters in a suitable model taking into consideration scaling laws on variables such as mass, vibration, and stiffness constants. It would be advisible to confirm the scaling law assumptions and predictions for vibration and viscosity effects before correction factors are used for setting scanning sensitivity levels.
Olf ferences in the curvature and surface finish between calibration blocks and vessel areas could change the dynamic response, so it may be advisible to establish correction factors between dynamic and static responses from the indications that are found during examination. This would avoid the difficul-ties associated with establishing a dynamic response OAC curve and still tale all the factors into consideration.
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1 nI may be used if sizing is performed using a static transducer. To minimize g
Delete the effect of any vibrations, the scanning speed should not exceed the cali-
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bration speed when automated equipment is used. ter automated equipment,
_ _,,,g.
the scanning direction should be the same as the calibration direction.
l unless it can be shown that change of scanning direction does not make a l~
difference in the sensitivity and vibration background noise received from an the search unit, or these differences should be taken into account. Some search units have a curved shoe that tends to heel over when the scanning Ldirection is changed, thereby resulting in loss of received signal.
(2) Secondary DAC. During some manual scans, the end point of j
the DAC curve may fall below 20% of the full screen height. When this happens, j
lt is difficult to evaluate flaws on the 20% and 50% DAC basis in this region since the 20% and 50% DAC points may be too close to the baseline. To over-come this difficulty, it is advisable that a secondary DAC curve, using a j
higher gain setting, be developed so that 20% and 50% DAC points may be I
easily evaluated. For this purpose, it is advisable that the gain be The secondary DAC curves need not be generated unless they are required.
Increased sufficiently to keep the lowest point of the secondary DAC curve here electronic DAC is used and amplitudes are maintained to above 20% of above 20% of screen height.
p full screen height a secondary DAC would not be necessary.
(3) Component Substitution. A calibration check should be made each time a component is put back into the system to ensure that such compo-f nents as transducers, pulsers, and receivers were not damaged while they were in storage. Ihls will ensure elimination of the error band and af stakes l
in resetting the various control knobs.
(4) Calibration Holes. Comparison of results between examinations performed at different times may be facilitated if the same equipment is used and if the reflections from growing flaws can be compared to the same reference signal. Reference signals obtained from a calibration block depend on, among other things, the surface roughness of the block and the reflector holes. lherefore, these surfaces should be protected from corrosion and mechanical damage and also should not be altered by machanical or chemical means between successive examinations. If the reference reflector holes or the block surface are given a high polish by any chemical or mechanical means, the amplitude of the reflections obtained from these reflector holes may be altered. Polishing the hules or the block surface is not forbidden a
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by the ASME Code. However, this possibly altered amplitude could affect the sizing of indications found during ar-examination. At this time, no I
recommendations are being made to control.he surface roughness of the block or the above-mentioned reflector holes; however, if the block or these holes l
are polished, this fact should be recorded for conslderation if a review of the UI data becomes necessary at a later date.
I 3.
HEAR-SURFACE EXAMINATION AND SURFACE RESOLUTION Sound beam attenuation in any material follows a decaying curve (expo-nential function); however, in some cases the reflection from the nearest hole is smaller than the reflection from a farther hole. This makes it dif ficult to draw a proper DAC curve. In such cases, it may be desirable to use a lower frequency or a smaller transducer for flaw detection near the beam entry surface to overcome the difficulty of marginal detectability.
Neau-field effects, decay time of pulse reflections, shadow effects, restricted access, and other factors do not permit of fective examination of certain volume areas in the component. To present a clear documenta-tion and record of the volume of material that has not been effectively examined, these volume areas need to be identified. Recommendations are provided to best estina'te the volume in tne region of interest that has not bees. ef fectively examined, such as volumes of material near each surface (because of near-field ef fects of the transducer and ring-down ef fects of the pulse due to the contact surface), volumes near interfaces between cladding and parent metal, and volumes shadowed by laminar flaws.
)*
4.
BEAM PR0fitE l'
8eam profile is one of the main characteristics of a transducer. It helps to show the three-dimensional distribution of beam strength for comparing f
results between examinations and also for characterizing flaws. Ihe beam profile needs to be determined and recorded so that comparisons may be made with results of successive examinations.
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_ m.-
_ - _ _ - _ _ - _ _ - - _ _ _ _ _ _ _ _ _ - _ _ _ _ - - _ _ _ _ _ _ - _ _ _ - _ - _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ - - - _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _. _ _ _ _ _ _ _ - _ _ - _ _ - _ _ _ _ _ _ _ _ _ - _ _ _ - - _ - _ -. = _ _ _. _ _ - _ _ _ _.
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8 5.
SCANNING Wl9-ETAL lbfERFACE The amount of energy reflected back free a flaw is dependent on (Ls surface characteristics, orientation, and sire. the present ASME Code proce-dures rely on the asplitude of the reflected signal as a basis for judging j
l
, flaws.' This means that the size estimation of a defect depends on the propor-tion of the ultrasonic beam reflected back'to the probe. the reflection l
behavior of a planar defect, which largely depends on the incident beam angle when a single search unit is used to characterize the flaw, is thus a decisive factor in flaw estimation. the larger the size of a planar defect.
the narrower is the reflected directional sound beam pattern, and hence 6
3 I
the flaw is more difficult to detect and size.5A Iherefore, the beam angles 3
used to scan welds should be based on the geometry of the weld / parent metal g
interface. At least one of these angles should be such that the beam is almost perpendicular (115 degrees to the perpendicular) to the weld / parent metal interface, unless it can be demonstrated that large (Code-unacceptable) planar flaws unfavorably oriented, parallel to the weld setal interface, can be detected by the UT technique being used. In vessel construction, some weld preps are essentially at right angles to the metal surface. In these cases, use of shear wave angles close to 75* is not recommended. Two factors j
would make the use of shear wave angles close to 75* inadvisable. -- first, the test distances necessary beceae too large resulting in loss of signal l
and second, the generation of surface waves tends to confuse the interpreta-tion of results. In these cases, use of alternative volumetric nondestruc-f
> Subarticle IWA-2240,Section XI of tiveexamination(NDE) techniques,aspermittedby[theASMECode,shouldbe considered. Alternative NDE techniques to be considered may include high-intensity radiograph or tandem probe ultrasonic examination of the wald-setal interfac:. To avoid the possibility of missing large fl Ws, particularly
- 6. Reflection of Ultrasonic Pulses from surfaces Heines and Langston Central Electridity Generating Board, U.K. ( CE58) report number those that have an unfavorable orientation, it is desirable that the back l
RD18/ N 4115 reflection amplitude, while scanning with a straight beam, be monitored over I
i 5" Probability of Detecting Planar Defects in Heavy Wall Welds by Ultrasonic Techniquo According to Existing Codes," Dr. Ing. Hans-Jurgen Meyer.
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Quality Department of M.A.M., Nurnberg D 8500 Nurnberg 115.
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the entire volume of the weld and adjacent base metal. Any area where a reduction of the normal back-surface reflection amplitude exceeds 50% should be examined by angle beams in increments of 115 degrees until the reduction i
of signal is explained. Where this additional angle beam examination is not practical, it may be advisable to consider examining the weld by a
~
supplementary volumetric NUE technique.
6.
SillNG lhe depth or through-wall dimension of flaws is more si nificant than 0
the length dimension, according to fracture mechanics analysis criteria.
tising the single probe pulse echo technique, it is possible, depending on flaw orientation, that some of these large flaws may not reflect much energy,
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j to the search unit.5(Because of this possibility, th' depth dimen' ion of
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the flaw should be more conservatively slied unless there is evidence to prove that the flaw orientation is at right angles to the beam. It is recommended that indications that are associated with through-thickness flaws and do not meet Code-allowable criteria or criteria recommended in this guide be sized at 20% DAC as well as at 50Y DAC.
In certain cases, it is possible for various reasons that a flaw would not reflect enough energy to the search unit to make the indication height 50% of the DAC curve height. Ilowever, if such a flaw were large, a persist-ent signal could be obtained over a large area. It is therefore recommended that all continuous signals that are 20% of DAC with transducer travel move-wnt of more than 1 inch plus the beam spread (as defined in Article 4, I,
nonmandatory Appendix B,Section V of the ASHE Code, 1977 edition) should be considered significant and should be recorded and investigated further.
The beam spread effect in sose cases can make very small flaws appear to be large when judged at 20% DAC; hence, beam spread has to be considered in judging the siQnificance of flaw N it is therefore recommended that only signals with a total transducer travel movement greater than the beam spread should be considered significant.
('
[ Ultrasonic [xamination Comparison of Indication and Actual flaw in RPV."
Ishi Kawajima-Harina Industries Co., Ltd., January 1976.
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Insert continued Typically a BWR reactor pressure vessel (RPV) wall in the beltline region is 6" thick and PWR-RPV wall is 8.5" thick. During flaw evaluation, where the- -
wall temperature is high and the available toughness is high, and the calculated critical surface flaw depth (a ) exceeds the wall thickness (t), a is taken*
g g
as the wall thickness. According to IWi-3600,Section XI, the allowable end-of-life size is ag = 0.la. Flaws exceeding this allowable value, which would g
be.85* for a PWR and.65* for a BWR, will have to be repaired. The above f
example illustrates the importance of blanking out the electronic indication signals and not examining the surface volume to 1" depth. 51nce tie flaws that can be alssed due to electronic gating may be larger than the flaws permitted with or without evaluation, this unexamined volume is important ard needs to-he identified.
s in certain cases areas were not examined because insulation was in the way and transducer could not scan the volume of interest and NRC was never
+
appraised about this situation until much later.
In view of above, to avoid licenslag delays, it is advisible that the volume of areas not examined due to any or all of the above causes is reported.
" Flaw Evaluation Procedures: ASME Section XI-EPRI, NP-719-SR, special report August 1978.
Return to previous"page 0
I Page 10.
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I Code-allouable criteria. As a minimum, these checks should be verified e
within one day t
andj5 Tier examining all the welds that 3ied To ba examined ln a Eractir ~ wI
~
.+ within one day pressure vessel during one outage.
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Pulse shape and noise suppression controls should remain at the same 1.1 Screen Height linearity setting during examination and calibration.
Screen height linearity of the ultrasonic instrument should be determined N
according to the mandatory Appendix ! to Article 4,Section V of the ASME Code, within the time limits specified
{
wi M iHe same setting'of pul'se-shape' modification a [ noise suppression controis-j in C.1 above.
as used during examination and in the same range of the instrument as the range g
f that would actually be used during examination. for systems using an electronic DAC, a means should be devised and used for demonstrating the proportionality of the signal response to dif ferent sites of re flectors at 1/4,1/2, and 3/4 I (depth. The accuracy of the proportionality should be recorded.
a l
t 1980 1.2 Amplitude Control linearity Amplitude control linearity should be determined according to the man withinthetimelimitsspecifiedl tory Appendix II of Article 4,Section V of the ASME Code, 91 edition.
in C.) ateve.
- 1. 3 Frequency-Amplitude Curve A photographic record of the frequency-amplitude curve should be obtained; as a minimum, when a camera is not available, the peak frequency value and points 3 d8, 6 d8, and 12 di below peak frequency amplitude should be recorded. The reflector used in generating the frequency-amplitude curves as well as the elec-,
tronic system (i.e., the basic ultrasonic instrument, gating, form of gated l
signal, and spectrum analysis equipment) and how it is used to capture the frequency-amplitude information should be documented.
l l
j 1.4 Pulse Shape I
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A photographic record of the unloaded initial pulse should t>e obtained ll against a calibrated time base. The time base and voltage values should i
l l
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be identitled and recorded on the horizontal and vertical axis of the above 2.1 Calibration for manual scanning For manual scanning for the sizing of flaws, static calibration may be photographic record of the initial pulse. The method used in obtaining the pulse-shape photograph, including the test point at which it is obtained, used if slzing is performed using a M atic transducer. When signals are daximized during calibration, they should also be maximized during sizing.
should be documented.
For manual scanning for the detection of flaws, reference hole detection should 8
be shown at scanning speed and detection level set accordingly (from the 2.
CAtl8 RATION dynamic DAC).
System calibration should be checked to verify the DAC curve and the 2.2 Calibration for mechanized scanning sweep range calibration per normandatory Appendix 8. Article 4.Section V of the ASME Code, as a minimum, before and after each reactor pressure vessel When flaw detection and sizing are to be done by mechanized equipment, examination (or each week in which it is in use, whichever is less) or each j
the calibration should be performed using the following guidelines:
time any component (e.g., transducer, cable, connector, pulser, or receiver) a.
Calibration speeJ should be at or higher than the scanning speed, I
b.
lhe direction of transducer movement during calibration should be in the examination system is changed. Where possible, the same calibration block should be used for successive inservice examinations of the same reactor the same as the direction during scanning, unless it can be shown that the pressure vessel. lhe calibration side holes in the basic calibration block change in scanning direction does not make a difference in the sensitivity and and the block surface should be protected so that their characteristics do vibration background noise received from the search unit, or alternatively these not change during storage. lhese side holes or the block surface should differences should be taken into account by a correction factor, c.
For mechanized scanning, signals should not be maximized during the not be modified in any way (e.g., by polishing) between successive exawina-establishment of the DAC curve, Lions, if these calibration reflector holes or the block surface is polished d.
One of the following alternative guidellmes should be followed for by any chemical or mechanical means, this fact should be recorded.
i establishing the DAC curve:
3.
HIAR-5URFACE (X/.NINA110N AND SURF ACE RE50 tuli 0N i
(1) the DAC curve should be established using a moving transducer mounted on the methanism that will be used for examination of the component.
(2) Correction factors between dynaalc and static response should The capability to effectively detect defects near the front and back surfaces of the actual component should be estimated. The results should be established using full-scale mockups, (3) Correction factors should be established using models and taking be repostei! with the report of abnormal degradation of reactor pressure boundary in accordance with the reu mmendation of regulatory position 2.a(3)
{
scaling factors into consideration (assumed scaling relationship should be verified).
of Regulatory Guide 1.16, " Reporting of Operating Information--Appendix A Technical Specifications." In determining this capability, the effect of (4) Correction factors should be established between dyannic and j
the following factors should also be considered; static response from the indications that are found during examination for i
If an electronic gate is used, the time of start and stop of the sizing. If assumed correction factors are used for detection these factors a.
control points of the electronic gate should be related to the volume of should later t+ confirmed on indications during the examination. Deviation in material near each surface that is not being examined.
the assumed value may result in reexamining the data.
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The decay time, in terms of metal path distance, of the initial pulse and of the pulse reflections at the front and back surface should be considered.
c.
The disturbance created by the clad-weld-metal interf ace with the parent metal at the front or the back surface should be related to the j
volume of material near the interface that is not being examined.
I d.
the disturbance created by front and back metal surface roughness should be related to the volume of material near each surface that is not l
being examined.
t 4.
BI AM PROF IIE the beam profile should be determined if any recordable flaws are detected. Ihis should be done for each search unit used during the examina-tion by a procedure similar to that outlined in the nonmandator Appendix B (B-60), Article 4,Section V of the ASME Code, for determining he's spread.
Jp. Interpolation for beam profile may be made for flaw assessment at Beam profile curves should be determined for each of the holes in che basic intermediate depths for which beam profile has not been determined, calibration block.
A. %..
5.
SCANNING Wtt0-MEIAL. INIERFACE i
lhe beam angles used to scan welds should be based on the geometry of the'keld/ parent metal interface. At least one of these angles should be such that the beaw is almost perpendicular (115 degrees to the perpendicular) to the weld / parent attal interface unless it can be demonstrated that large (Code unacceptable) planar flaws unfavorably oriented, parallel to the weld-n tal interface, can be detected by the UI technique being used. Otherwise, use of alternative volumetric nondestructive examination (ND[) techniques, as permitted by the A5ME Code, should be considered. Alternative NDE tech-niques may be considered to include high-intensity radiography or tandem probe ultrasonic examination of the weld metal interface. Beam angles used for UT ex.wination should be reported with the report of abnormal degradation of rea6 tor pressure boundary in accordance with the recommendation of regu-latory position 2.a(3) of Regulatory Guide 1.I6.
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7.
REPORTING Of' RE50t15 Records obtained while following the recommandations of ret'slatory positions 1.1, 3, 5, and 6 above, along with discussions and explanations, if any, should ce reported with the examination test results to NRC.
If i
the size of an Indication, as determined in regulatory positions 6.1 or 6.2, equals or exceeds the allowable limits of Section XI of the ASHE B&PV Code, the indications should be reported as abnormal degradation of reactor pressure l
boundary in accordance witti the recommendations of regulatory position 2.a(3) of Regulatory Guide 1.16.
Along with the report of ultrasonic examination test results, the follow-Ing information should also be included; a.
The best estimate of the error band in sizing the flaws and the basis for this estimate should be given.
b.
Ihe best estimate of the volume that has not been effectively examined out of the volume required to be examined by the A5ME Code such as volumes of material near each surface because of near-field or other effects, volumes near interfaces betweer -ladding and parent metal, volumes shadowed by laminar material defects, vilumes shadowed by part geometry, volumes inaccessible to the transduces, volumes affected by electronic gating, and volumes near the surface opposite to the transducer should be given.
c.
If considered desirable, the material volume that has not been effectively examined by the use of the above procedures may be examined by alternative effective volumetric NDE techniques. If one of these alternative NDE techniques is a variation of UI, recommendations of regulatory post-tions 1 and 3 should apply. A description of the techniques used should be included in the report. If other volumetric techniques or variations
.J UI are used as indicated in regulatory position 5, the effectiveness of these techniques should be demonstrated and the procedures reported for review by the NRC staff, i
)
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15 I
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. IMPlfMENTATION i
lhls pro;4 sed guide h.as been rele.ased to encourage public participa-
- - + Delete tion in its developmentJ Except in those cases in which an appilcant pro-
.I l
Delete poses an acceptable alternative method for complying with specified portions
_f of the Commission's regulations, the methodhdescribed in the Q Outde reflecting public comments will be used in the evaluation of (1) the resu_lt.s of in. servi.ce examination programs of all operat.ing reactors perfor.me b,
(a~fter_issuanceoft.he_activeDuhn_d(2)theresultsofpreserviceexamina-
/.
~
tion programs of all reactors under construction performed [E months)af ter j
-p July 15, 1981.
h...nceoftheactivegulde) l
-The recommendations of this guide are not intended to apply to pre-
~~ %
% Delete.
s" service examinations that have already.been completed.
Qtt_er the issuance of the active auldelMe NRbtaf f intends to recommend that all licensees consider modifying their technical specifica-tions50thattheyareconsistentwiththerecosumndationscontainedhherein.'
l.
- Intended to t>e 6 sionths after the issuance of the guide.
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