ML20206D504
| ML20206D504 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 11/07/1988 |
| From: | Sieber J DUQUESNE LIGHT CO. |
| To: | NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM) |
| References | |
| IEB-88-009, IEB-88-9, NUDOCS 8811170109 | |
| Download: ML20206D504 (4) | |
Text
_ _ _ _ _ _ _ _ -.
C OLn g @ CCgilpagly B;lg,gev %c w=
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=4? unm November 7, 1988 U.
S.
Nuclear Regulatory Commission Attn:
Document Control Desk Washington, DC 20555
Reference:
Beaver Valley Power Station, Unit No. 1 and No. 2 BV-1 Docket No. 50-334, License No. DPR-66 BV-2 Docket No. 50-412, License No. NPF-73 NRC Bulletin 88-09 Thimble Tube Thinning in Westinghouso Reactors Gentlemen:
This submittal is in response to the reporting requirements contained in NRC Bulletin 88-09.
Inspections were performed at Beaver Valley Unit No.
1 during the sixth refueling outage which ended March 2,
- 1988, and therefore, this submittal specifically addresses Item 3.b of the Bulletin.
Inspections for Unit No. 2 are scheduled for tho first refueling outage which is expected to begin approximately March 17, 1989.
Additionally, information regarding program development applicable to both Units is provided.
A formal program for performing Flux Thimble Tube inspection has not been developed for Beaver Valley.
The inspections on Unit No. 1 completed during the sixth refueling outage were performed using approved procedures with the intent of obtaining baseline information regarding thimble tube thinning.
Several thimbles indicated wear and corrective action was taken following data analysis by our NSSS.
One location (J-15) exceeded our acceptance criteria for rcmaining in service and four locations (B-5, D-12, J-5 and L-4) were repositioned to prevent further wear at the wear indications.
The acceptance criteria utilized was defined by our NSSS and will be discussed below.
This information was submitted to the NRC on June 29, 1988, on Licenseo Event Report 88-010-00.
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Be0Vor VallCy Psw0r Statien, Unit Nac.1 & 2 Dockct No. 50-334, License No. DPR-66 Docket No. 50-412, License No. NPF-73 NRC Bulletin 88-09 Thimble Tube Thinning in Westinghouse Reactors Page 2 The re-inspections scheduled for Beaver Valley Unit No. I during the seventh refueling outage, and the initial inspections scheduled for Unit No. 2 during the first refueling outage will be performed in accordance with an inspection program as described below.
The inspection criteria and methodology discussed here were applicable to the initial inspection of the Unit No. I thimble tubes.
Our program will be presented in a format consistent with the actions requested portion of NRC Bulletin 88-09.
Actions _Requestedt l
1.
Each addressee is requested to establish an inspection program to monitor thimble tube performance.
This inspection program should includet the establishment, with technical justification, of an appropriate thimble tube wear acceptance criterion (for
- example, percent through-wall loss).
This acceptance criterion should include allowances for such items as inspection methodology and wear scar geometry uncertainties.
I An approved program will be in place prior to conducting thimble tube inspections on Unit No.
2.
As previously stated, this outage is tentatively scheduled for mid-Narch, 1989.
The Unit No. 1 seventh refueling outage is tentatively scheduled for September, 1989.
This program will define appropriate thimble tube wear acceptance criterion as follows.
Flux thimbles exhibiting wear indications in excess of 45% will be removed from service by closing the seal table isolation valve.
During the Unit No. 1 initial examination, a finite element structural analysis was performed that concluded a thimble tube could experience 60%
material wear loss and still assure operation with an external pressure of 2250 psig.
A 15% allowance is used to account for inspection methodology and wear scar geometry j
uncertainties.
This formed the basis for an acceptance criterion of 45%.
I Tubes exhibiting indications greater than or equal to 40% thru
'I wall will be axially repositioned to provide new wear surfaces.
This criteria was also applied to Unit No.1 and is supported by the finite element analysis.
This action provides assurance of pressure boundary integrity through the implementation of remedial corrective actions.
Beavor Vallcy Powcr Stction, Unit No3. 1&2 DockOt No. 50-334, License No. DPR-66 Docket No. 50-412, License No. NPF-73 NRC Bulletin 88-09: Thimble Tube Thinning in Westinghouse Reactors Page 3 Our acceptance criteria may be revised in the future based on further refinement of the accaptance criteria following completion of a
Westinghouse owners' Group (WOG)
Program that is currently y'
underway.
This program will provide accurate eddy current wear scar standards via correlation with removed worn flux thimble samples from 1
operating plants.
the establishment, with technical justification, of an appropriate inspection frequency (for
- example, every refueling outage).
Our program will define an inspection frequency of each refueling i
outage based on Beaver Valley Unit 1 experience to date.
The WOG program will provide wear rate estimates for various styles of Westinghouse plants.
The inspection frequency can then be adjusted to reflect the results of the WOG program and/or subsequent i
1 examinations.
the establishment of an inspection methodology that is l
capable of adequately detecting wear of the thimble tubes (such as addy current testing).
l Since the postulated wear mechanism of flux thimbles is flow induced vibration, Beaver Valley has employed state of the art eddy current testing for detection of degradation.
This inspection technique has proven to be capable of detecting flow induced 1
vibration wear degradation in heat exchanger tubing.
Further demonstration of the reliability of the eddy current technique will again be provided by the ongoing WoG program.
The above represents the approach used for Unit No. 1 for the initial inspection of the thimble tubes and our intended program for I
subsesuent inspections at both units.
Program changes will occur as 1
more information becomes available either through the Woo or through the assessment of plant specific data.
l If you have any questions regarding this submittal, please contact me or members of my staff.
very Truly yours, k
k q
/ J.
D. Sieber l Vice Fresident, Nuclear i
i cc:
Mr. J.
Beall, Sr. Resident Inspector Mr.
W. T.
Russell, NRC Region I Administrator t
Mr.
P. Tam, Project Manager Director, Safety Evaluation & Control (VEPCO)
.. S.
COMMONWEALTH OF PENNSYLVANIA)
)
SS:
COUNTY OF BEAVER
)
On this 7-day of.
644 e CA1/
, 1988,
_d [ [,m. M / ',
a Hotary Public in and for said before me, es commonwealth and County, personally appeated J. D. Sieber, who being duly
- sworn, deposed, and said that (1) he is Vice President of Duquesne
- Light,
( 'J )
he is duly authorired to execute and file the foregoing Submittal on behalf of said Company, and (3) the statements set forth in the Submittal are true and correct to the best of his knowledge, information and belief.
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