ML20043H290

Forwards Results of Refuel 7 once-through Steam Generator (OTSG) Eddy Current Insp,Per Tech Spec Section 4.4.5.5.Eight Defective Tubes & Two Administratively Plugged Tubes in OTSG a Resulted from Review of Insp Data

ML20043H290
Person / Time
Site:	Crystal River
Issue date:	06/15/1990
From:	Beard P FLORIDA POWER CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
3F0690-02, 3F690-2, NUDOCS 9006250041
Download: ML20043H290 (5)

Text

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m Power-coneoncion l June 15,_1990

'3F0690-02 l

,U.S.. Nuclear Regulatory Commission  ;

LAttention':- ' Document Control Desk- l Washington, D.C. 20555 l

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Subject:

Crystal River Unit 3 j K Docket No.- 50-302

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' Operating-License No. DPR-72 q ,

Steam' Generator Tube-Plugging

Dear Sir:

.. -J Florida Power Corporation.isl submitting the results of the Refuel 7 Once

• Through Steam ' Generator f(OTSG) ' eddy current examination ir) .accordance

.with: -Technical -Specification-_Section - 4.4'.5.5. 'The -eddy current inspections of the OTSG'"A" and "B"-.were completed on_May'29, 1990' . A review of the inspection data resulted in eight (8). defective; tubes and L :two.(2) administratively plugged tubes in the-"A" OTSG,~and sixteenI(16) ,

i defective tubes, one-(1) obstructed tube-and~seven (7) administratively -

plugged tubes in the "B'_' OTSG. Attachment'l-describes the criteria used-for sample selection andl Attachment 2, provides the-location and percent

-degradation ofLthe tubes plugged during the inspections.

. Sincerely, O

.M.' Beard, Jr. . i

Senior'Vice President Nuclear' operations PMB:wla Attachment

'h. xc: l Regional Administrator, Region II i l 0L

,- sSenior Resident Inspector 0 9'006250041 900615 U ( ('

PD ADOCK 05000302 51 PDC \

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GENERAL' OFFICE: 3201 Thirty iourth Street South * ' P.O. Box 14042.

• St. Petersburg, Florida 33733 * (813) 866-5151 .,

, A Florida Progress Company l s y_:

). s ATTACHMENT 1  ;

Florida Power Corporation (FPC) performed eddy current examinations of the once Through Steam - Generators (OTSG's) during Refuel 7. The examinations included the following:

OTSG "A" OTSG "B" i

% No. of  % No. of Tubes Tubeg Random sample size 22 3417 22 3417 Special Areas (lane & peripheral) 2. 4 _ 372 4.8 .745 Total % & No. of Tubes inspected 24.4% 3789 26.8% 4162 Sample selection for an eddy current examination must be done in ,

accordance with Table 4.4-2 (enclosure 1) of the Technical ,

Specifications. This Table describes the initial random sample size (3%) i and classifies the inspection results into three categories, C-1 through  ;

C-3, which define the size of subsequent random samples. Entry into the  :

C-2 category results in a progressive reinspection scheme up to a maximum i of 21% of the tubes in the affected steam generator. Entry into the C-3 category requires a 100% inspection of the affected steam generator.

Reinspection of additional steam generator tubes on a progressive basis is costly in both personnel exposure and outage time because of the reindexing of the-robotics in the steam generators and the rescheduling of other outage activities. Therefore, the Refuel 7 inspection scheme was devcipped ' to incorporate in advance the cascading effect for reinspection in the C category, thus avoiding the added burden .of changes to the robotics and interference with other scheduled outage activities. The inspection scheme assumed the result of each of three sample inspections would be no worse than a' C-2 category. (In hindsight, ,

as noted below,-the approach was in error since it did not follow the intent of the progressive logic of Table 4.4-2) . In addition, the Refuel-7 eddy current scope was developed'to provide at least 20% tube coverage to be consistent with the EPRI "PWR Steam Generator Examination Guidelines, Revision 2".

The approach used a first sample inspection of 3% of the tubes per steam generator, a second sample inspection of 6% more tubes per generator and a third sample inspection of an additional 12% of the tubes per steam ~

generator. This results in a total inspection population of 21% of the tubes. For conservatism, a 22% sample. size was decided upon. The 22%

sample was then randomly selected as a total group and the eddy current examination was performed. However, upon review following the ,i E inspection, it was realized that the 3% first sample as well as the-L second and third sample sets had in fact not been randomly selected and D tracked within the randomly generated 22% sample. Therefore, it is not possible to determine if, following the progressive logic of Table 4.4-2, a sufficient number of defective tubes would have been ident;.fied in 1

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[j ;.. x sir tho' - first 'or second sample sets to produce- a C-3 category result

requiring inspection of all tubes'in the generator.

However, Florida' Power' Corporation considers the inspection scheme used  ;

adequate to verify the~ integrity of the OTSG pressure boundary and that -1

-no, safety concern exists. This conclusion is based on the small-number

.of defective tubes identified when compared to the large sample of tubes Einspected. FPC will assure-that future eddy current inspections will

~ follow the progressive logic intent of Technical Specifications Table 4'.4-2.

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~ TABLE 4.4-2 _ _

STEAM GENERATOR.TW9E INSPECTION ,

1ST SAMPLE INSPECTION 2ND SAMPLE-INSPECTION 3R9 SAMPLE INSPECTION

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. Action Required Result Action Required Result Action Required Sample Size Result g

A minimum C-1 Non'a N/A N/A N/A N/A-E ef S tubes ,

per.s.6. C Plug defective C-1 None M/A N/A y,

y tubes and inspect Plug defective tubos C-1 None Ql additional 25 tubes in this S.G. C-2 and inspect additional C-2 45 tubes in this S.G. Plug defective tubes.

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>o "8 C-3 Perform action for C-3 result of first sample.

C-3 Perform action for C-3 result of first sample N/A N/A C-3 Inspect all tubes All in this S.G., plug other None N/A N/A defective tubes,- S.G.s

'd and' inspect 2S are:C-1

• tubes in each U

• other S.G. ~

Notify NRC Some Perform action for pursuant to S.G.s C-2 result of-second N/A N/A 10-CFR 50.72. C-2 but sample. e no add-itional S.G.s are C-3 gp ,

$ Addi- Inspect all tubes in N/A N/A of tional' each S.G. and plug g S.G. is defective tubes.

r' z C-3 Motify NRC pursuant o

- to 10 CFR 50.72.

$ = 3H1 Where N. is '.he number of steam geners' 's in the unit'and n is number n of steam generators inspected during Anspection.

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ATTACHMENT 2

-Eddy Current Testing on "A" and "B" 8 team Generators.

'"A" Steam Generator - Ten Tubes Plugged Bew rd;tl '  % Thruwall Location j 63 129 44 10th TSP  !

64' 127 45 10th TSP i 69 130 43 loth TSP-77 3 55 15th TSP 77 4 42 15th TSP  !

77 124 41 10th TSP 77 125 48 9th TSP 77 125 46 10th TSP 99- 41 45

• 4th TSP i 25 4 40 91 38 38 ADM l ADM i "B" Steam Generator - Twenty Four Tubes Plugged q RQH s.21  % Thruwall Location 27 93 67 8th TSP 27 93 70 7th TSP 28 93 40 8th TSP 34 61 61 UTS i 78 49 40 UTS 79 37 55 lith TSP i 88 39 47 7th TSP

9 6. 33 65 LTS 98 28 66 LTS

98 44 43 LTS A 109 34' 53 LTS .;

116- 46 54 LTS 124 39 56 7th TSP -4 125 9 42 8th TSP -!

126 9 66 8th TSP.

145 11 61 7th TSP  :

146 25 64 8th TSP

' 8 7., 59 N/A

• UTS Only 64 114 38% ADM 124 9 38% ADM 47' 1 OBSTRUCTED -ADM 47 2 N/A ** ADM 46 1 N/A ** ADM 40- 1- N/A. ** ADM

.48 2 N/A ** ADM TSP - Tube Support Plate UTS - Upper Tube Sheet

.ADM' , Administrative LTS - Lower Tube Sheet

" Plugged UTS To Match LTS earlier plugged

- Tubes plugged and Stabilized to surround obstructed tube 4 [

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