ML20029D855

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Summary of 940329 Meeting W/Util in Rockville,Md Re SG Tube Exam at Plant.Attendees Listed in Encl 1
ML20029D855
Person / Time
Site: Crystal River Duke Energy icon.png
Issue date: 04/25/1994
From: Raghavan L
Office of Nuclear Reactor Regulation
To:
Office of Nuclear Reactor Regulation
References
NUDOCS 9405100296
Download: ML20029D855 (86)
v • d • e


Text

-

April 25, 1994 Docket No. 50-302 LICENSEE:

Florida Power Corporation FACILITY: Crystal River Unit 3 (CR-3)

SUBJECT:

SUMMARY

OF MEETING ON MARCH 29, 1994, REGARDING CR-3 STEAM GENERATOR TUBE EXAMINATION Licensee representatives met with members of the staff on March 29, 1994 in Rockville, Maryland, to discuss their proposed steam generator technical specification (TS) criteria for addressing low signal-to-noise ratio indications (S/Ns) in various locations in the steam generator tubes.

l is a list of attendees. consists of the licensee's l

handouts distributed at the meeting.

l I

During the last outage, the licensee pulled six tube sections from the lower l

bundle to permit examination of an increasing number of S/Ns during eddy current examination. The degradation was determined to be pit-shaped intergranular attack (IGA) flaws, caused by sulfur intrusion into the steam generator. The licensee performed several laboratory examinations and tests on four of the six pulled tubes and concluded that the degradation was not safety-significant and that the structural integrity of these tubes met the requirements of Regulatory Guide 1.121. The licensee plans to pull additional tubes and inspect them during the Refuel 9 scheduled to commence in April 1994.

The licensee stated that the current TS for tube repair is based solely on percent through-wall and does not address pit-shaped IGA-type degradation.

The licensee discussed a proposed interim TS change based on a voltage, and flaw length and width-based criteria for plugging IGAs exhibining S/Ns less than 5:1. The proposed criteria would be applicable for Cyc'.e 10 only and are intended to ensure tube structural integrity against tube burst. On March 30, 1994, in a follow-on telephone conference, the staff commented that it needed more detailed technical details on the development of " flaw depth-versus-voltage" correlation, including data acquisition and analysis procedures, measurement uncertainties, and statistical validation of the results.

The staff indicated that the licensee's analyses should account for undetected and multiple flaws, and evaluate leakage integrity during a steamline break.

The licensee indicated that it would review the staff's commen s and may meet with l

the staff later to resolve these issues.

L. Raghavan %jec anager 9405100296 940425 Project Directorate II-2 DR ADOCK 05000302 Division of Reactor Projects - I/II p

PDR Office of Nuclear Reactor Regulation

Enclosures:

As stated e

page S C-E E BE*OU S CD'd " N CE Office LA:PDII2 PM:PDII2 D:PD b h EMCB Name E.Tana L.Raghavan b H.Berkhw!

N Date 04/ /94 04/25~/94 04/b 94 04/

/94

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  • Distribution - See next page - Document Name: G:\\ CRYSTAL \\940329. SUM b

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DATE: April 25,1994 l

Distribution Docket File-NRC & Local PDRs PDII-2 RF W. Russell /F. Miraglia 12-G-18 L. Reyes S. Varga i

G. Lainas H. Berkow L. Raghavan E. Tana OGC E. Jordan, MNBB 3701 B. Sheron T. Reed K. Karwoski E. Murphy E. Sullivan J. Strosnider ACRS (10)

D. Verelli, RIl

Crystal River Unit No.3 Florida Power Corporation Generating Plant cc:

Mr. Gerald A. Williams Mr. Joe Myers, Director Corporate Counsel Div. of Emergency Preparedness Florida Power Corporation Department of Community Affairs MAC-A5A 2740 Centerview Drive P. O. Box 14042 Tallahassee, Florida 32399-2100 St. Petersburg, Florida 33733 Mr. Bruce J. Hickle, Director Chairman Nuclear Plant Operations (NA2C)

Board of County Conmissioners Florida Power Corporation Citrus County Crystal River Energy Complex 110 North Apopka Avenue

.,s.

15760 W. Power Line Street i'>

Inverness,' Florida'32650 Crystal River, Florida 34428-6708 Mr. Robert B. Borsum Mr. Rolf C. Widell, Director B&W Nuclear Technologies Nuclear Operations Site Support (NA21) 1700 Rockville Pike, Suite 525 Florida Power Corporation Rockville, Maryland 20852 Crystal River Energy Complex 15760 W Power Line Street Crystal River, Florida 34428-6708 Regional Administrator, Region II U. S. Nuclear Regulatory Commission Senior Resid9nt Inspector 101 Marietta Street N.W., Suite 2900'"

Crystal River Unit 3 Atlanta, Georgia 30323 U.S. Nuclear Regulatory Comniirsion Mr. Bill Passetti 6745 N. Tallahassee Road Office of Radiation Control Crystal' River, Florida 34428 Department of Health and Rehabilitative Services Mr. Gary Boldt 1317 Winewood Blvd.

Vice President - Nuclear Tallahassee, Florida 32399-0700 Production (SA2C)

Florida Power Corporation Attorney General Crystal River Energy Complex Department of Legal Affairs 15760 W Power Line Street The Capitol Crystal River, Florida 34428-6708 Tallahaseee, Florida 32304 Mr. Percy M. Beard, Jr.

Sr. Vice President Nuclear Operations Florida Power Corporation ATTN: Manager, Nuclear Licensing (NA21)

Crystal River Energy Complex 15760 W Power Line Street Crystal River, Florida 34428-6708

ENCLOSURE 'l Crystal River Unit 3 Steam Generator Tube Examination Meeting on March 29,1994 Attendees Name Office Harley Silver NRR/PDII-2 Herb Berkow NRR/PDII-2 Phyllis Dixon FPC Ken Wilson FPC Rolf Widell FPC Gerry Cowles FPC Loretta Cecilia FPC Kenji Kreywosk EPRI L. Raghavan

- NRR/PDII-2 Sterling Weems MPR Rocky Thompson FPC Ray Luken BWNT Brian Sheron NRR/DE 2

Emmett Murphy NRR/EMCB Lynn Connor STS Richard Coe BWNS Ken Karwoski NRR/EMCB Harry Smith BWNT Tooo Richards BWNT Robert Giardina NRR/0TSB Don Mays DUKE P_0WER

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FLORIDA POWER CORPORATION l

i CRYSTAL RIVER UNIT 3 l

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CRYSTAL RIVER UNIT #3 STEAM GENERATOR TUBE INTEGRITY PROGRAM I

PHASE 1:

Inspection of all tubes in each Steam Generator which have not been inspected since preservice inspection Status:

Completed in 1992 PHASE II:

Pull tubes from the first span of the "B" steam generator for chemical and metallurgical analysis Status:

Completed in 1993

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PHASE lil: Pull tubes from the upper boiling region of the "B" steam generator for chemical and metallurgical analysis Status:

Tube Pull April 1994 Analysis 1994/95 PHASE IV: Continue to improve eddy current inspection practices Status:

Long term maintenance contract with BWNT includes 20%

inspection each outage in accordance with EPRI guidelines; Field trials of advance ~NDE techniques ongoing

PHASE V:

Participation in BWOG tube integrity projects

1..

Status:

Burst Test Program 1995 Oconee tube pull 1994' l

Oconee tube analysis 1995 d

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NOTABLE DIFFERENCES i

OTSGs -VS RSGs j

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Sensitized 1600 Microstructure

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Tube Support Plate Broach Hole Design j

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' Lower Heat Flux in area where most Deposits accumulate I

No Large, Hard Sludge Piles Observed 1

No identified Problems with ODSCC 1

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UPPER TUBESHEET (OTS) 1 AVIlliART

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STEAM OUTLET i

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LOYER SECONDARY

- LOYER SECOND ARY M ANTAY HAN0 HOLE 3

LOYER TUBESHEET (LTS) i Ficure 1:

0TiG Lc, cit Jinal Section 5

4 Broachec TSP Configuration Br'oached Hof f..

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ECT INSPECTION HISTORY l

"A" STEAM GENERATOR

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19871R6 1989/M7 1990lR7 1992/R8 l

Tubes 3,370 2,831 3,795 8,364 l

Inspected

. (22%)

(18.2%)

(24.4%)'

(54%)

Tubes 3

1 10 22 Plugged Total 9

10 20 42 Plugged "B" STEAM GENERATOR 1987/R6 1989/M7 1990lR7 1992/R8 Tubes 0

2,097 4,155 11,250 Inspected (13.5%)

(26.8%J ~~

(73%)

Tubes 0

0 23 70 Plugged Total 27 27 50 120 Plugged I

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REFUEL 9 PLANS Bobbin Coil Inspection of 20% of the total tubes per steam generator Rotating Field Inspection of lane region tubes at the 15th TSP and UTSF, indications of interest on candidate tubes to be pulled Rotating Pancake Coil inspection of SINS detected for the first time as well as a sample inspection of existing SINS Considering Ultrasonic Inspection of indications of interest on candidate tubes to be pulled Removal of four tube sections with Indications at the 7th and 9th TSPs and distorted tube sheet signals at the LTSF Preventive sleeving of 164 tube.s __

in the lanelwedge region of each steam generator

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"A" STEAM GENERATOR 4

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I i

TUBES TO BE INSPECTED "B" STEAM GENERATOR i-.

i

-~

v-

--w..--,,,

m

_., ~.. _,.... _ _ -

l DECISION TO PULL TUBES WAS BASED ON AN INCREASING NUMBER OF S/Ns IN CR-3 DATABASE AS MANY TUBES WERE INSPECTED FOR THE FIRST TIME l-INDUSTRY EXPERIENCE WITH S/Ns l

SHOWED THAT REAL DEFECTS COULD BE PRESENT 4

l

1l i

i VECTOR MECHANICS ILLUSTRATION OF HOW A PHASE ANGLE IS DETERMINED FOR A DEFECT SIGNAL NL r

1 i

t R

r - Defect Signal (Impedance (Z))

Xn - Inductive Reactance R = Resistance 0 = Phase Angle r=

X

. g2 2

t l

$ = tan *8 (X /R) t i

j FIGURE 1 1

i Vector Mechanics Illustration of How Noise Signal Vector (ar) Interferes with Defect Signal Vector (r} Producing Resultant Signal (ri?

Ar

__. __ _ _ 7 _ _ __

3

\\

\\

{

\\

180-0 g

r s

N ri

\\

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\\

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i

\\

\\

0 N

\\

P 4

.r = Original defect signal A(

i ar = Noise signal 0 = Angle between defect signal and noise signal c: = Change in phase (Error angle) r1 = Resultant signal j

h Error Angle vs Signal to Noise Ratio for Different Values of 0 60

+ for 0 = 170*

a for 0 = 140*

- for 0 = 110 E

50 a for 0 = 90*

o for 0 = 70*

x for 0 = 40

,e e for 0 = 10 40 o;

Q io 30 p*

8 3

x 20

\\

x X

10

+

so

~'#

0 R*

' "C5 i

0 5

10 15 20 25 Signal to Noise Ratio ( )

( A r)

l 5:1 CRITERIA Used as cutoff to ensure that error in percent through wall sizing of indications does not exceed 10%

Refuel 8 Analyst Guidelines allowed Analysts to make %TW calls for S/N ratios < 5:1 where signals were acceptably clear.

Indications of this type were documented using~an OSN code.

Three out of four indications on pulled tubes which had axial dimensions of ~ greater than 0.06 inches and.%TW depth greater than 50% were recorded as OSNs with %TW calls made.

Average sizing error for the three indications using phase angle was 16.3%

Demonstrates that 5:1 criteria is a conservative point at which to differentiate between applicable repair criterias

?

h

i I

i l

EDDY CURRENT SIGNAL NOISE i

i i

Most observed in the CR-3 "B" Steam Generator, j

only marginal noise in the "A" Steam Generator Noise obsented in CR-3 Steam Generators is l

primarily associated with the horizontal component j

of the signal which indicates that it is not associated with an electrical source, probe cable or j

cable extension length.

Noise appeam to be l

inherent and varies from tube to tube, likely a result of the tube manufacturing process.

l J

i l

l

..., ~

EFFORTS T0 MINIMlZE[NDISE"i j

Data cable length consistently kept at 60 feet 400 kHz differential frequency used for detection l

Optimized fill factor of 0.85 Electrical noise is easily distinguished from tube noise; when electrical noise is identified, actions such as rerun with an alternate probe or.

replacement of sacrificial data cable are taken

r l

l REFUEL 8 TUBE PULL GOALS Physically characterize any tube degradation associated with S/N eddy current signals Identify the damage mechanism, if any Evaluate the structural integrity of tubing if damage is present t

Quantify the accuracy of eddy current techniques

i J

j i

PULLED TUBE EXAMINATION l

l 1

i Eddy Current Examination with Bobbin Coil and Rotating Pancake Coil Probes 2

Ultrasonic Examination Tube' Swelling and Burst Testing Chemical Analysis of Deposits.and Indication Surfaces i

j, Metallography i

i i

.. _ _ _ ~,. _ _. _. _..

4 i

I i

i

SUMMARY

OF TUBE PULL FINDINGS

?

e j

S/N Eddy Current Signals in the First Span i

of the "B" Steam Generator are l

due to very small pit-like IGA 4

3 l

l Pit-like IGA was caused by attack by sulfur oxyanions t

i i

1 j

i i

.-e

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ew, v,m-,r.

r 0.04"

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S AVERAGE PIT-LIKE IGA

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4 100X i

1 Cross Section Through IGA - Tube Section 109-30-2B

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n e

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Burst Pressures for tuhmg with i

with multiple pit-lika IGA indications l

demonstrated a me:igin of safety l

above Regulatory Guide 1.121 requirements i

l 1

j 4

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tp L

8 8

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O v Wg0M0)WCn. $gg OwNQ1gz t

e BURST TEST RESULTS Tube Number of Burst Indications Pressure l

on Tube (psig) 97-91 17 12,400 106-32 62 11.,400 l

l l

ln.

l 1

Detection Rate was determined to be i

approximately 70 to 80% for indications of 40% through wall o~r greater 4

i i

l~

This detection rate was determined J

by both BWNT and EPRI via independent reviews 4

1 i

i i

l i,

1 l

Review of eddy current historical data concluded indications were not l

growing in number or size 3

l i.

Conclusion of no growth was reached l

by both BWNT and EPRI during independent reviews 4

i I

t l

i b

i 1

e

,-3---,_

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--~-m.

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FPRE JE-EC-.O N 3 90BAB L TY 100

=!

90-I O

[

o 80-3

/

m 70-8 d

60 m

/

50 m

z O

40 i-

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30-l 5

20

+

/

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10-0 10 20 30 40 50 60 70 80 O

% WALL LOSS BY DESTRUCTIVE ANALYSIS t

-*- BOBBIN Coll RESULTS Figure 2 - IGA percent detection at various ' depths by bobbin

-r

..n,

,r--

-r

-- ~ --

i l

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i 1

i l

The Bobbin Coil Phase Angle Method

...1l l

currently used to estimate an indication's i!

percent through wall depth is inaccurate l

for CR#3's very small volume indications l

i l

Inaccuracy of Phase Angle demonstrated in independent reviews by BWNT and'EPRI h

i l

i i

?

4

_.,,.,g,y,,._,

.,_.7,,

3F0793-02 FIGURE 8 BOBBIN EDDY CURRENT ACCURACY TUBES 52-51, 90-28, 97-91, & 106-32 INCLUDES BOTH FIELD AND LAB DATA y

z i OVERSIZED BY BODBtN EC

/

b o

o 60 u

o g

g 8

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g 20 8o UNDERStIED BY DOOBIN EC

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EPRI ANALYSIS 5/14/92 100 W

/

~ "

x x a--

EC DATA g

90 l__.. x i--

go

/

BEST FIT W

/

s 70-I N

/

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X/Y-MEAN 36/30%

10-w--#

w 0i

,=,x Y

x 1

0 10 20 30 40 50 60 70 80 90 100 1

MET PERCENT WALL LOSS l

1

- Linear regression analysis of eddy current bobbin coil estimates versus metallurgical test results l

l l

l l

1 i

l COMPARISON OF FIRST SPAN "B" l

S/N INDICATIONS TO THE-BALANCE l

OF S/N INDICATIONS IN BOTH STEAM GENERATORS

$A i

FIRST SPAN "B" BALANCE OF S/Ns f

small volume RPC data shows I

pit like IGA majority are voiumetric indications similar i

to CR-3 first span low voltages low voltages most <

1 most <

1 Average axial and Average axial and circumferential sizes circumferential sizes estimated by RPC estimated by RPC 0.11 to 0.19 inch axial.

063 to 0.2 inch axial 0.14 to 0.25 inch cire !

0.2 to 0.22 inch cire 1

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C3 SLL S/N INDIC.

M PULLED TUBES.

Figure 5: Comparison of 5/N indications on pulled tubes to Inservice S/Ns

CRYSTAL RIVER 3 B-OTSG, S/92 OUTAGE BOBBIN AMPLITUDE VS. EXTENT, S/Ns 0.75 Fu roz

-g o.5-il Q.

+

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CRYSTAL RIVER 3, 5/92 OUTAGE BOBBIN AMPLITUDE VS. EXTENT, ODI S/Ns-TUBES DESTRUCTIVELY EXAMINED O.75 to W

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i l

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50 -

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i j

)

j l

0.0 0.25 0.50 0.75 i(M 1.25 1.50 0;

g Axial Length of beiect (Inches)

Allowable Tube Wall Penetration Figure 11:

For Axial Slot Type Defects (Axial Cracks)

MR EB,n..P,s.n 42 r.u rsvs.tu' 1

f

- ~ -. - _ _, _ _ _ - _ _ _ _,.

i l

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1 i

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j cf Figure 1 are also Met, j

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90

(

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10 20 30 40 50 60 70 60 90 100

1 1

Penetration of Degradation

i

(%)

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Figure 12: Maximum Allowable Penetration Versus Arc Length for 34.1 % Maximum Allowable Area of Degradation WM.PR.

r.,ci. n.c c2/'s/s* ss) 43

f 1

MPR CALCULATED DIMENSIONAL LIMITS 4

l Axial Size TW Depth Circumferential Size i

0.25 inch 100%

122 0.5 inch 65.6%

187 s

0.75 inch 62%

198 1.5 inch ~

60.3%

204 i

6 j

k 4

a e-p y

y

l l

l l

l l

SINCE PHASE ANGLE CANNOT BE USED l

TO ESTIMATE % TW DEPTH OF AN INDICATION, l

THE DIMENSIONAL LIMITS SELECTED TO ENSURE STRUCTURAL INTEGRITY ARE BASED ON l

,i ALLOWING UP TO 100% TW PENETRATION 4

l DIMENSIONAL BASED REPAIR LIMITS f

0.25 inch Axial O.6 inch Circumferential Sizing Estimates Made using RPC Clip Plots

CIRCUM. EXTENT MEASUREMENT ACCURACY DESTRUCTIVE EXAM VS. RPC CLIP PLOT a=

a2;

/

CONSEfNATNE

-i a22

/

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AXIAL EXTENT MEASUREMENT ACCURACY DESTRUCTIVE EXAM VS. RPC CLIP PLOT

/

a:

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aoe ain a6 a6 a6 di ab ah a'i.

al.

a2 ACTUAL AXIALEXTENT, INCHES J

Figurc 9: Accuracy of Axial Sizing using RPC

BASED ON RPC OF INDICATIONS ON PULLED TUBES,100% WOULD HAVE PASSED THE DIMENSIONAL BASED STRUCTURAL CRITERIA IF APPLIED l

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i I

INDUSTRY DATA l

EDDY CURRENT VOLTAGES i

i FOR VARIOUS SIZES OF IGA 4

)

pal.lSADES:

l l

Grew standardized IGA patches on sensitized 1600 j

tubing using sulfurous acid.

Patches were 0.2" l

axial by 0.588" circumferential with various l

through wall penetrations.

Observed voltages l

increased as volume (i.e. %TW? increased.

i 4

l BWOG NDE COMMITTEE:

i Grew IGA patches on 1600 tubing using acidified i

sodium tetrathionate (sulfur in an oxidized state?.

l Indications grown were 0.75 inch axial by 0.25 i

inch circumferential.

Metallography was performed to determine %TW depth.

Observed voltages increased as indication volume (i.e. %TW increased?.

3 i

L

l i

l Since the standard axial and circumferential i

size of the Palisades' IGA was less than the i

axial and circumferential size limit for indications i

on CR3 tubes, none of the indications studied i

would be considered structurally ~ unacceptable j

if found on CR-3 tubes.

l Palisades' study demonstrates that:

I l

1.

Observed voltage is a function of the l

indication's size.

j l

2.

Voltages much higher than those observed l

from S/N indications in CR-3 steam l

generators.

l l

i 1

I i

l

, ~ '

i i

l i

i s

One IGA indication studied by BWOG NDE l

Committee would have been considered j

structurally significant on CR-3 tubing i

per MPR's calculated limits.

The indication j

size was 0.75 inch axial, 0.25 inch l

circumferential, with 71% TW penetration.

l i

The 600 kHz voltage recorded from this

I indication was 7.7 volts.

i i

l The % TW limit for a 0.75 inch axial

)

indication.on CR-3 tubing is 62%.

l Based on BWOG NDE Cornmittee work, the voltage for a 0.75 inch axial, j

0.25 inch circumferential, and 62% TW indication would be approximately 6 volts.

I

=

mL

.Mt-m.

a, s

u 6

.c.

A b &

BWOG NDE COMMilIEE IGA STUDY VOLTAGE Tb'i)ERCENT THROUGH WALL 100 90 i

80 O

-j 70 3

I 60 00 O

O rt 50 Iw

's 40 O

to U

b 30 a

0 20 h

[

10 O

i i

i i

i O

2 4

6 8

1 3

5 7'

VOLTAGE i

i

l l

i 4

l VOLTAGES UP TO 6 VOLTS CAN l

BE OBSERVED FROM NON-STRUCTURALLY j

SIGNIFICANT INDICATIONS i

k SETTING THE STRUCTURAL LIMIT AT 3 l

VOLTS ACCOUNTS FOR UNCERTAINTY AltB LIM:ITED AMOUNT OF DATA AVAILABLE i

3 VOLT UPPER LIMIT ALSO REDUCES l

THE PROBABILITY THAT ANY' 100%

i TW INDICATIONS WILL REMAIN IN SERVICE 4

i

i 4

1 d

l Voltage to Defect %TW Correlation j

Performed by EPRI as part of a BWOG Project i

4 i

~

i Correlation used voltages and metallography data from CR-3 Pulled Tubes l

4 i

i i

l

}

.i l

em l

Plot of Canned IGA to TRANS/ ROTATED ASME Field Data for Smallest Voltage's 100 90 80-70-1

//

=

//

40/

i 30 0

0.5 1

1.5 2

2.5 3

3.5 4

Voltage EPiti Voltage to Percent Throunh wa?! correlation f ir.'ure 6:

l FIGURE 1 BURST PRESSURE FOR UNIFORM THINNING 3/4" LONG FLAW (REFERENCE 3.1) i 12 10-l W

a_

a-a v

w c

h 6-P' '

C o

h.wl a-l

)

l 3.4v w

4-W

/ %

a b.fJ 2-0 0

10 20 30 40 50 60 70 80 90 100 MAXIMUM DEGRADATION, %TW M S4 THNNED LENGTH 1

1 51-1229189-00 l

Page 5 of 5 l

I i

I

?

-l 3

INSERVICE INDICATION GROWTH STUDIES

SUMMARY

FREESPAN:

Voltage change over at least two consecutive inspections for 65 indications studied resulted in an average deviation of +0.01 volts with a standard deviation of 0.11.

No evidence of growth.

TUBE SUPPORT PLATE INDICATIONS:

Voltage change over at least two consecutive inspections for 62 indications studied resulted in an average deviation of 0.19 volt and~a standard deviation of 0.30.

No significant growth observed.

1 i

i 1

i

)

i i

i 1

PROPOSED 2 VOLT SCREENING CRITERIA INCLUDES CONSERVATIVE 1 VOLT ALLOWANCE FOR GROWTH i

'i l

l i

i 1

2 3

1 i

1 4

l i

i i

...._._.,.,..,-,_,m,.e

.,,,w,m

,.,,, - _, ~,.

,_,.u,,,.

a.

. _ - w I

l l

l l

CRACK LIKE INDICATIONS FOUND,BY RPC IN THE LANE AND WEDGE REGION WILL BE REPAIRED, REGARDLESS OF THEIR ESTIMATED SIZE i

3 l

~~'

t

er a

a-1) 4 4

i 1

)

N i

i

-1 1

i l

i i

.i 1

I LEAKAGE CONSIDERATIONS

~

i

?

d 4

4 4

2 t

4 4

1 i

d

]

4 1

1 1

I I

4 1

a i

j 8

1

't

'k 1

4 e

a I

'l l

d i

k 2~

5

a 4

I Eddy Current history indicates no significant growth of indications.from j

inspection to inspection l

J l

NO PRIMARY TO SECONDARY LEAKAGE HAS BEEN OBSERVED AT CR-3 i

I i

\\

v i

f l

f l

1 J

l s

+

l r

-,. - n

.n..

3.--..-....

l A

i l

t

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}

nd O

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f-----)

& _ _ _ _ _ _ _ _.)

s

/

( _ _ __ _ _ _.)

V l

(___________N_____/_______()

___ = -_--____

l l

j (j___.__________._.____._____.___

J (a) EDM SLOT (b) ELLIPTICAL WASTAGE I

t i

i A

I (1 - Il i

i v

I i

ll I

t i

I s

~~

,i I l l

/

\\~_J l

(c) UNIFORM THINNING l

FIGURE 1.1.

EDM-Slots, Elliptical-Wastage, and Uniform-Thinning Wastage Flaw Specimens 1.3 i

,,.,.,.--.-.,-.._.e-

i I

l l

i l

10 8

9 8

o6

_m 7

e we 6

O D

m O

w 5

O m

6 c'

C.

& 4 m

K O

$3 g

0 UNDEFECTED o

2 00 WRAP ANGLE O 45 WRAP ANGLE i

1 O

f I

I I

1 1

0 10 20 30 40 50 60

,70 80 90 100 MAXIMUM DEGRADATION (% WALL) 21.

Burst Pressures for 0.625 x 0.034 in. Elliptical Wastage 41 MH 9

y q

Y y

e f

~y=y f

,g

. ~-

  • t. '. -

~ :,

L

i 1

s i

MINIMUM LIGAMENT RE(lUIRED TO l

PREVENT LEAKAGE FOLLOWING i

A MAIN STEAM LINE BREAK l

l t

j 0.0029 inch wall (Calculated by MPR Associates, Inc.)

i i

!i 4

Equates to 91.5% Through Wall Depth i

4 i

a 4

i

Plot of Canned IGA to TRANS/ ROTATED ASME Field Data for Smallest Voltage's 100 90

/

80 m

6-

/

/

  • /

i i

i i

30-0 0.5 1

1.5 2

2.5 3

3.5 Voltage LPiti Voltane. to Percent Throunit wall correlation fioure 6:

i

l I

l Largest %TW identified out of 120 pit-like IGA indications on 4

pulled tubes was 62% TW 1

i Similarity in the axial and circumferential j

sizes and volumetric characteristics

]

of inservice S/Ns and pit-like indications on pulled tubes indicates high probability 1

that inservice S/Ns have similar through wall l

depth distribution i

i i

i l

i i1

DISTRIBUTION OF IGA PATCH DEPTHS, CR-3 TUBES 52-51, 90-28, 97-91, & 106-32 30 W 25 b

FIRST SPAN INDICATIONS ONLY Em oO 15 o

8 g 10 m2 g5 0-9 :'

10-19 20-29 30-39 ' 40-49 50-59 ' 60-69 ' 70-79

%M FROM DESTRUCTIVE EXAM 4

i l

CRYSTAL RIVER 3 B-OTSG, 5/92 OUTAGE BOBBIN AMPLITUDE VS. EXTENT, S/Ns 0.75 m

tu I

o z_

~

O.5 a

D.

+

O_ao 2

o a

o

[ 0.25

~

oor o+ o T

o,

=,

o

=

O 1

2 3

./.

)

0.5

. 1.5 2.5 3.5 BOBBIN SIGNAL AMPUTUDE, VOLTS o

AXIAL

+

CIRCUMFERENTIAL

~ * *

  • AMPLITUDE VS. PHASE RELATIONSHIP CR-3 PULLED; TUBES VS. REMAINING c

5 h

2O UI O

h 6

o a=

0-m k

~

Y:

7 Z

o o

.P U

a o

o g" o o o 4

o

"#a o

o

,o y s m

o I"

o

=

a o

A 4o b

b2 lb ib lb 1' 0 lb 6

N PHASE ANGLE, DEG.

[] hLL S/N INDIC.

M PULLED TUBES.

Figure 5: Comparison of S/ti indications on pulled tubes to Inservice S/tts

AVERAGE WIDTH TO DEPTH RATIO DEPTH ESTIMATES FOR INSERVICE S/Na 60

~

~

50 1

~

Q 40 u

i sO 8

30 g

4 5

20

~

Z 10

~

Q

.Y b

20 4O l

6O l __

NO l

Id0 10 30 50 70 90 DEPTH 1%TW)

Is S/N s 5:1?

l I

I YES NO I

1 Is Indication in Existing dbase?

Size Based on Phase f*>

2 0V ' ' >2Of

>40%

d-Imperfec' tion De' graded Repair YES NO 2

l Is Voltage s 2 Volts?

.e NQI.,

YbS NO I

Is bobbin coil voltage within +/- 0.5 Volts of last recorded examination?

l Is RPC data available for this indication?

i YES NO l

1 1

I i

NO NQS NQI YES v

(Imperfection) l l

Is bobbin coil voltage NQI within +/- 0.5 Volts of last recorded examination?

Perform RPC

{

~ '

on 3% random i

i sample per YES NO I

generator NQI~

Use existing RPC to characterize l

l

[

IGA /Pitlike Wear MBM I

I I

Is axial size 3 0.25 TW Size based Historical data inch AND circumferential on Wear Standard Review must be size s 0.60 inch?

performed to confirm its i

i i

presence in all

<20%

>20%

>40%

previous exams.

e i

l l

No change Imperfectiol YES NO n

Degraded Repair observed in signal.

Degraded Repair Figure 16:

Revised Analyst Guidelines 56

I NCI I

t Perform;RPC' examination 1

i

_I Volumetric Crack-like 1

'Use RPC to Characterize l

Repair 1 4=<.

ti m

a I

s i

IGA / Pit-like Wear TEM 4

i l

Is Axial Eize s 0.25 inch TW size based Historical data l

AND Circumferential size on wear'standhrd review must be

< 0.60 inch?

performed to

)n

. verify"its

j 4

g presence in i

i i

i i

<20%

.>20%

- >40%.

t all previous

?

l l

exams.

No Imperfec: ion Degraded Repair,, c change, observed in signal.

l l

i

,,4g.

?

YES NO I

f Repair a

j 5.2 Volts

>2 Volts f

Imperfection Degraded ii 1

h 4

r l

4 I

1 l

i l

j Figure 17: Analyst Guidelines for Non Quantifiable Indications 1

3 1

57 t

f

m,

-+.s e

es--,-,.

3

,w--es.

.*-----r--

-e.

-g' g

-q-w

,p-.p.m-g 9,e eg gcq p-g piy-g, ew-~

A 4

1 i

,i i

i REPEATABILITY OF INSPECTIONS

~,.......

i Use of the same, experienced vendor (BWNT) l for all eddy current inspebtiins l

Use of same procedures from outage to outage 1

2 l

Changes in~ probe types, inspectio, n.frequ,encies, j

etc., made only when 'demonstratsd improvements l

Optimized fill factor of 0.85 l

Consistent data calile length

' ~

i d

2 i

1

.,...___.__-_..,-..m..,_

)

i I

e

-. m.,,

m.., a...,,,...,,

i Probe wear has not been considered a 4

l problem during past inspections j

l Mandatory probe change after every l

500 full length tube examinations i

is under consideration to ensure l

probe wear will ~not affect signal amplitude 3

4>

j 4

k

{

i l

i j

i i

1

,. - -... - -..., - -.... _., _. -.., _, - _,.,.. -. ~,., - -..

l:a-i ANAL.YSIS CONSISTENCY 4

j Procedures provide consistent guidance l

to analysts on signal formation, l

signal to noise ratio, phase angle and signal amplitude measurement i

Majority of indications at CR-3 in the freespan l

where difficulty of separating a mix residual l

component from signal amplitude is NOT present i

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All data analysts required to pass a performance demonstration test specific to CR-3 which doc 0ments acceptable measurement of l

typical CR-3 damage mechanisms i

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Written Analyst Guidelines Specific to CR-3 are provided.

Revision to Refuel 8 Guidelines currently in progress to provide guidance on " noise" and new methodology for disposition of S/N indications Voltage normalization addressed in CR 3 specific analyst guidelines; in accordance with the 1989 edition of the ASME code Use of Primary and Secondary Data Analysis with resolution by the lead analyst as required, including resolution of differences in recorded voltages and characterization codes During Refuel 9, one senior ana yst will be assigned overall responsibility for implementation of new S/N criteria to assure consistency in application

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SUMMARY

J S/N indications in first span of "B" steam i

l generator have been demonstrated by pulled tube analysis to be small, pit like IGA.

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Sample RPC of inservice S/Ns indicates the majority are volumetric and approximately l

l the same physical size as indications l

found on pulled tubes from the.first span.

l Refuel 9 tube pull data will further validate this.

l Small, Volumetric indications are not l

structurally significant.

Burst testing of Pulled j

tubes demonstrated a margin of.~ safety l

above RG 1.121 requirements.

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l No significant growth of freespan or tube support plate indications has been observed l

over consecutive inspections.

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l Dimensional Based Repair limit of 0.25" axial l

and 0.60 inch circumferential ensures no structurally significant indications will be left.in service, even for through wall depths up to 100% penetration.

i Voltage Based Screening Criteria of 2 volts l

minimizes unnecessary RPC while ensuring that.the largest SlN indications receive

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.second level examination.

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Through wall depth distribution of first span S/Ns indicate none exceed the maximum l

allowable depth to ensure no ~ leakage following a main steam line break.

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i Proposed method for dispositioning CR 3 small volume S/Ns represents a significant improvement over past practice AND is superior to the current Technical Specification Repair limit which is based solely on' percent through wall Request for approval of proposed criteria is for one cycle only Lcycle 10).

Proposed criteria is the result of a proactive steam generator tube integrity program and is NOT reactive to tube leaks or ruptures.

No primary to secondary leakage has ever been observed at CR-3 as a result of tube degradation.

Additional information from CR-3 and Oconee tube pulls and from BWOG Burst Test Plan will be available prior to the Refuel 10 ECT inspection.

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