ML20052F696

Ringhals 3 Steam Generator Insp Evaluation of Eddy Current Results

ML20052F696
Person / Time
Site:	05000000, 05000465
Issue date:	05/31/1981
From:	SWEDEN, GOVT. OF
To:
Shared Package
ML20049H209	List: ML20049H208 ML20049H210 ML20049H253 ML20052F683 ML20052F696 ML20052F711 ML20052F716 ML20052F746 ML20052F757 ML20052F771 ML20052F787 ML20052F790 ML20052F794 ML20052F797
References
FOIA-82-167 NUDOCS 8205130418
Download: ML20052F696 (6)

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A RINGHALS 3 I

STE.Ot EDERATOE IHSPECTION EVALUATION 3

0F EsOY CUES.!HT RE59tTS PAY, 1951 I

INTR c.'tTIcii

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One stem gentrnor (f 2) in the Ringhals 3 (STP) n'.'cleer plant wes subjs:tec

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k to eddy current (EC) t sting in Kay,1961, af ter a water hamer event had I

tten re::rded in the fee:Nater lines. One steam generator (SG) only was i

h:sen to lock for schanical effects, such as dents at the prehtater baffle t

elevations; fourteen (14) tucts in F.W 49 w6re insp cted by Iettc which was I;

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retain-d by the Swedish State pwer Bosrd (55pB) for this purpcse. Ietes r

reported no significant indications or dents on the prehester tubes which were enmined; it kes suggested that several tubes exhibited signels, which should be monitored in future inspections. On the basis of that inspection, it wts concludsd that no dr.25e to the S/G had resulted from-the water hazer evet:. A listing of the tubes inspected by 7etec is given in Table 1.

WESTINGHOUSE REVIEW 0F 5/81 EC TAPE kg ccturence of primary to secondary leakage in tube R49C55 in 10/81 caused another, snore exietoive Et impection to be pnrformed at Ringhals f 3 in Octcher,1981. A large nur,ber of significant (>20% penetration) Et indica.

f tiors were reported in all three S/G's, concentra;ed at the preheater baffle elevations.

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3 To eysluate the progression rate of the penetrations observed, k'estinghouse I

re-ew ir.ed the EC te.g from Key,1981. A number of s..all EC indications were obtained frcm the residual cutput of the multiple frequency mixing i

process which cce.bined the EC responses frca 550 KHz (differential) and 130 l

XH2 (differentiti) to eliminate the baffle plate sigr, sis.

The interpretation g

f of the May 1901 date was made with nuwrical estitutes given in Table 2 even t,

theugh there is little confidente in the reality of such ntr.bErs. This was i

I an attem Lv uldeiri wm.h.N cf wear prQoregion between M4v and h

October. As is discussed belcw hwever, an overell averace 4toth of gp;-

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traticn of 45 percent (72C1) for this K3y data is believed unsupportable in that the signals are so soll as to introduce excessive errors in interpre.

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tation.

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Tha EC rrixing process is illustrated in Figure l A derein referer.ce supper:

plate sfruiater sipals and cc:nbined to yield a ms11 residual with rc sig.

h nific2nt vertical features.

Ft;ure 13 demnstrated sintlarly that no fl signific:nt less of sipal is seen den the mixing is.erfomed en a calibra-hu tien standard withut sunort plate inter'erence. When the calibrati:n helis id m placed under the ed;a Of the referer.ce su;;c-t plete sirulater - theey

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-h. i n ta r* r-n ce - tha m ir.c nmeans preauen tha u ult niu:

s tratad in Fi;ure 2A-E.

It is seen th:t the calibratien h:le signals are cet Ig l!

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"icst" in the prccess, but the spread of phase angles in :?.e residual is

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recuted therdy increasing the uncertainties associated with the estir.ates.

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Mertheless, this represents significant ir.prcyter. ant in inspection caphility i

since the regort plats-calibratien hole ccm;csite signal by sin;1e fre;umy f

is not susceptible to reitable depth estimation.

It is Ecssible by reviti-

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frequency mixing to ciscrir.inate between shalW, large volure incHeations snd deep indicatient by climinating the support pl:te ir.terference, f

When the residual signal is very ur.all in emplitude in cc parisen to the sicnal being eli:*ir.ated, large uncertainties are intrcduced. The trolitude F

of the signal is propertional to the volua.e of metal removed.

In part these

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uncertainties could arise frcen prche wobble or the cptielration of the mixing selution; as such the anticipated errer could go in either a positive or a L!

i negative direction. When the mixed signal solutten is viewed 'fran a tuba with and without the support plate signal, a phase angle shift is observed n

b (see Figure 3) resulting in an overestirrete of the tube well penetratien.

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In order to produce a ec::ncn data tase, a coc6tned Westinghouse /Zetec tape l

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analysis was perfomed on all the EC data from Ringhals 3, both frm. 5/51 -

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tapes and from the 10/81 tapes. Table 2 lists the results for the fourteen tubes inspected in 5/81 and 10/81.

For each locatien where an indication

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l was reported in the 5/81 data, a photo cceparison of the signals frc:a teth inspections has been prepared (see Attschornt 1).

Several obser.ations m s proprtit~:

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1) Ravtu of the 31 signals recorded for the May ik31 data, shcws

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that 21 have :nplitudes of less than 1 volt and thess, thereicre,

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are conside;ed Unsuitable for estir.stes of depth of penetratten, i

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2) Of the 10 sigr,als fr:m the w,5y 19$1 data that have ceplitude: cf 1 er mre volts, it is ncted that 6 of these have not changed in dep:h estimte er have shewn a decrease in depth of penetratien when ccepared with the October 1921 data alth: ugh uplitudes hhvo increased. This cbsenation is incensistent with the cyerall t

innd bised en trear veh.w chriges which tho< the rear pr.:m ts j

c:nti r.uing.

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3) Ccnsidering the four re:aining signals of the May B31 data that have op11tudes of 1 volt or erste and that also show scoe increase in depth relative to the Octcbir 1."81 data, it is believed net credible to assign either a de;th cf pnetration r.or a chtn;e in ie depth of penetration for the tubes based en these few signals.

4) For virtually every indication. a significant increise in signal uplitude is apparent between 5/81 and 10/S1 inspections.

5) For each indication cbserved in May,1981 scme departure from nonnal is apparent in the single frequency EC traces. This supports the pattern shce by the mixed frequency output.

6) Where signals in 5/81 mrely created distortions in the single I

frequency suppbrt plate signatures, the 10/81 data consistently I

reflect strenger. components of tube degradition.

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It is notable that the average signal uplitude in the 5/61

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data is <0.9 volts whereas the typical support plate signal uplitude was approximately 3 Yolts (see photos).

The 10/81 I

signP amplitudes for the same locations yield an average of

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5.1 volts, a S.7 fold increase fran 5/81 to.10/51.

CONCl.USICH Review of the eddy current data for the tubes inspected in S/G (2 in both 5/21 and 10/81 shws grwth in the tube degradation 'n both volu,e of wear for individual locatiens and in ntr.ber of indicatiois at the preheeter l

baffle lecattens. This is bated en the 5.7 fold increase in signa! upli-tudes for the et3ened indicaticns. Even though *.he presence of incipiert l

west is indicated in the 5/81 data, the nature and cmplitude of the cbserved l

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indt:stient ere such tMt r*liele estintien of the tube wall pmete:tien is nc!. tw11ered possiM ei thi: resulted fiom the tw :12nsi to noise retic, in the mixed resi:!ual signals as well as the relative si:e of the tube des adatjen si;nals cc= pared to the sucport plate signals. A positive bias was ncted in the mixed residual.utput for R19 C65 - one cf t.% hbes pulled fm the plant - when the depth of poetration with a support plate i

sicciater was : r;.z zd tc that cf the E4 e tun.

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Vnila the 5/51 data is subject to large errers in interpret:tien, the 10/51 produced signals of truch larger uplitude wt.ich are less subject to tha i

effects affecting the'5/S1 ruults. The 10/21 data is believed conser,'ativa h

k at noted in the Return to Ponr P.eport in that an approxftrate 17 percent l.

over estimate is indicated by addy current empared to actual depth Petsure-mnts trade en remved tubas.

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TASLE I i

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N LISTING OF TUBES IHSPECTED AT RINGK45 III u

DURIMG THE MAY.1931 OUTAGE 11 pm Cchen

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49 31 l-49 as 1

49 39 l

c 49 43

,1 49 51 49 55 49 59 49 63 49 67 49 71 49 75 49 79 I-49 83

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<i3 WEST!XW.CSE IEEC /.v.' SIS OF RINGRA1.5 3 S/G P2 til May 1981 October 1991 j

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Ateli tude N :ent Amit tede Percent letstien 49 35

<.5 c ::

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< 20 B:ffle #3 49 35

<.5

< ~0 1

37 Stffle f5 49 35

<.5

• l0 1

< 20 Baffle 63 49 35 5

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2; hffle #10 g-49 39

<.5

<;0 1

35 hffia f5 49 39

<.5

*0 1

' 20 Baffle it,

' f 49 39

<.5

<3 1

36 Baffie fS 49 39

.5 45 3

37 Saffle 110 h

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49 43

.,5 24 2

20 Esf fle fB 49 47

.5 5

3 43 Baffle #4 49 4't 2,

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> 18 36 Baffle (6 49 47

.5 55 1

26 h ffle fS 49 47

.5 57 3

36

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h ffle (9 49 51 3.

54 6

51 Baffle il 49 51

.5 35 4

_37 84ffle f2 49

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I 49 51 2.

55 12 43 Baffle f5 49 51

.5 58 4

37 Eaffle l$

49 55 3.

12 18 5.0 Bdf.le._f5 -

49 55

.5 32 2

33 Baffit fB j.

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49 55

.5 e I0 1

50 Eaffle 110 49 59 1.

13 6

36 Bifne f5 49 63 2.

54 8

41 Baffle f5

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49 63

.5 27 3

36 Esffle fB 49 67 1.

23 12 48 Baffle f3 49 67

.5 34 5

34 u ffle f4 49 67 2

La 5

44 Esffle f5 49 67 1

10 7

48 Saffle 16 49 67 1

32 7

50 Biffle 77 49 71

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'2 6

t.4 Bifn e f5 43 71

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6 7-6 Raffle #8 l

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