ML17254A213

Requests Approval to Install Limited Number of Addl Tubesheet Sleeves in Areas Where Accessibility of Brazed Sleeves Limited.Specific Number of Tubesheet Sleeves Will Be Established Based on Results of Insp During Mar 1985 Outage

ML17254A213
Person / Time
Site:	Ginna
Issue date:	02/22/1985
From:	Kober R ROCHESTER GAS & ELECTRIC CORP.
To:	Zwolinski J Office of Nuclear Reactor Regulation
References
NUDOCS 8502260220
Download: ML17254A213 (13)

Text

REGULATORY e

ORMATION DISTRIBUTION SY M (RIDS)

ACCESSION NBR:8S02260220 DOC DATE: 85/02/22 NOTARIZED:

NO DOCKET FACIL:50-244 Robert Emmet Ginna Nuclear Plant~

Unit ii Rochester G

05000204 AUTH,NAME AUTHOR AFFII IATION KOBERiR AN ~

Rochester Gas 8 Elect'r ic Corp, RECIP ~ NAME RECIPIENT AFFILIATION ZWOLINSKIiJ ~ A ~

Operating Reactors Branch 5

SUBJECT:

Requests approval to install limited number of addi tubesheet s]eeves in areas where accessibility of brazed sleeves limited,Specific number of tubesheet sleeves will be established based on results of insp during Mar 1985 outage'ISTRIBUTION CODE:

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-55AlR N.K 14649.0001 ROGER W. KOBER VICE PACSIOCNT ELECTRIC &STEAM PROOUCTION February 22< 1985 TCLCPHONC ARCA COOS TIS 546-2 n/00 Director of Nuclear Reactor Regulation Attention:

Mr. John A. Zwolinski> Chief Operating Reactors Branch No. 5 U.S. Nuclear Regulatory Comnission Washington>

D.C.

20555

Subject:

Steam Generator Tubesheet Sleeves R. E. Ginna Nuclear Power Plant Docket No. 50-244

Dear Mr. Zwolinski:

The installation of tubesheet sleeves was approved by the Nuclear Regulatory Commission (NRC) through a Safety Evaluation Report (SER) transmitted to Rochester Gas and Electric (RGRE) by letter dated June 13> 1983.

This SER limited the number of tubesheet sleeves that could be installed in 1983 to not more than 30 and also prevented the installation of additional tubesheet sleeves after the Spring 1983 outage until the effectiveness of inspection techniques could be demonstrated by RGGE.

During the 1983 outagei four tubesheet sleeves were installed in the A Steam Generator and twenty-four sleeves were installed in the B Steam Generator.

During the 1984 outage>

nine more tubesheet sleeves were installed in the B Steam Generator~

as allowed by an NRC SER dated May 9< 1984.

Based upon work performed during the outage last year< parent tube flaws located 0.75 inches or greater above the sleeve were detectable with the annular differential magnetic bias eddy current probe.

Since that time< the technical evaluation and development of nondestructive examination methods for the purpose of optimizing inspectability of tubesheet sleeves/tube integrity has continued.

An improvement has been achieved which reduces the area above the tubesheet sleeve of limited inspectability.

Inspections will now be performed utilizing a standard annular differential coil probe delivered from the cold leg of the steam generator.

This increases the area'f acceptable inspection to 0.5 inches above the sleeve end.

Defects are marginally detectable at 0.25 inches above the sleeve end.

Improvements in detecting parent tube flaws in the free span region behind the sleeve have been made by increased gain and probe impedance optimization modifications to the Zetec MIZ-12 Multifrequency Eddy Current System.

This has improved the sensitivity by a factor of two to three> enabling standard ASME flaw detection.

However< flaws located from the sleeve end through expansion transition are still not detectable.

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ROCHESTER GAS AND ELECTRIC CORP.

DATE February 22, 1985 To Nr. John A. Zwolinski SHEET NO.

Although improvements have been made in the eddy current inspection techniques>

there are still some areas of the tubesheet sleeve/tube combination where the ability to detect and size defects is limited.

These areas are at the weld transitions and at the upper end of the sleeve.

Use of the above coils will allow 20% through wall defects to be identified as shown on Attachments 1 and 2.

larger defects can be seen at some intermediate locations.

A comparison of the current inspection capability with that available in Spring 1984 is shown on Attachment 3.

Research and development efforts are continuing in the following areas:

A.

The Zetec NIZ-18 Multifrequency Eddy Current System>

improving gain by developing a modification to the system.

B.

Improved Design Multi-array Pancake Coil Probes for above the sleeve.

C.

Improved Cross~ound Coil Probes< with optimized magnetic bias by Eddy Current Technology Incorporated.

D.

Improved 3-D Eddy Current Coil Probes> with optimized magnetic bias by Eddy Current Technology Incorporated.

E.

Low Frequency Eddy Current Instrumentation to improve the depth of penetration of the eddy current fields for inspecting above the explosive weld but below the sleeve end.

F.

Electromagnetic Acoustic Transducers (ENAT's) developed for the inspection of the parent tube above the sleeve and down to and including the expansion area of the explosive weld.

Any of these efforts resulting in improvement in the inspection which are completed by the March 1985 Annual Refueling and Maintenance Outage< will be considered for a first time application and evaluation.

Design changes in the upper end of the sleeve< relative to the expansion area and end-effect area are under evaluation for future consideration.

Due to limitations of the eddy current inspection techniques>

the acceptability of installing additional tubesheet sleeves has been reviewed.

The small number of defects found during eddy current inspection of the steam generator tubes in the 1984 outage indicates that the crevice environment<

especially at the elevation of the upper end of the tubesheet sleeves> is enhanced by our programs of crevice flushing and water chemistry control.

Additionally< recent tube pull analyses have shown that the area of the tube at or above the explosive weld has essentially no intergranular attack< less than 3% involvement.

Therefore>

the probability of experiencing additional degradation in the area of concern is minimal.

Further~

the indications that have been seen have been well within the crevice, below the explosive joint.

Also< a corrosion test program has been performed with Babcock 6 Wilcox to access the potential for primary side stress corrosion cracking.

Results of samples removed from the test environment have not indicated any, detrimental effects due to the tubesheet sleeve process.

U II I

ROCHESTER CAS AND ELECTRIC CORP.

DATE February 22I 1985 To Mr. John A. Zwolinski SHEET NO.

Because installation of tubesheet sleeves permits repair of tubes without requiring the tube to be removed from service>

as is the case in pluggingI it is desirable to sleeve instead of plug.

Therefore>

we request approval to install a limited number of additional tubesheet sleeves.

These installations will be limited to areas where accessibi1ity of brazed sleeves is limited or where it would be beneficial from an ALARA standpoint.

The specific number of tubesheet sleeves will be established based on the results of inspections to be conducted during the Spring 1985 outagei scheduled to begin in early March.

We believe this is acceptable based on the limited area at the upper end of the sleeve where the eddy current inspection cannot currently detect and size defects at the 20% level> the low likelihood defects will occur in this area near the top of the tubesheeti and the acceptable consequences (limited leakage as shown in our submittal of April 23I 1984)I even if a defect does develop in this area.

V truly yoursi R

r W. Kober Attachments

ATTACHMENT 1 TUBE/SLEEVE EDDY CURRENT

!INSPECTION CAPABILITY FOR ASME FLAWS

.Tubesheet CD CD

'CD LA B

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'Tube Tubesheet Sleeve G

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ATTACHMENT 2 TUBE/SLEEVE EDDY CURRENT INSPECTION CAPABILITY

~'Designation (See attachment 1)

Distance From Top of Tubesheet Flaw Detection Capability ASME Flaw Sizing Capability.

A D

E F

G H

I J

K L

0. 50 1.00 1.25 1.50 1.75 2.00 - 2.25 2.63 3.38 3.38 Yes Yes Yes Marginal None Ma'rginal None Yes Yes Yes Yes Yes 20K 20K 20Ã None None

!;None None 40K 40K 20K 20K 20K

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