ML20082D302
| ML20082D302 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 04/03/1995 |
| From: | Richard Anderson NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9504100037 | |
| Download: ML20082D302 (4) | |
Text
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Northern States Power Company Prairie Island Nuclear Generating Plant 1717 Wakonade Drive East.
Welch, Minnesota 55089 April 3, 1995 U S Nuclear Regulatory Commission l
Attn: Document Control Desk Washington, DC 20555 i
PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 1
50-306 DPR-60 Response to NRC Request For Additional Information Related to F* and L* Steam Generator Repair License Amendment Recuest The attached information is being provided in response to your letter dated March 8, 1995 which transmitted NRC Staff questions related to our License l
Amendment Request dated January 9, 1995 which proposed the incorporation of F*
and L* Steam Generator Tube Repair Criteria into the Prairie Island Technical 1
Specifications.
Previous responses to the March 8, 1995 request for additional information were provided by NSP letters dated March 15 and 22, 1995. Attached are our responses to the remaining questions related to the L*
repair criteria from the March 8, 1995 NRC letter In this letter we have made one new Nuclear Regulatory Commission commitment which is identified as such in the attachment as the statement which is in italics.
Please contact Gene Eckholt (612-388-1121, Ext. 4663) if you have any questions related to the attached responses, c
Roger O Anderson Director Licensing and Management Issues c: Regional Administrator - Region III NRC Senior Resident Inspector, NRC NRR Project Manager, NRC J E Silberg Attachments: Response to March 8, 1995 NRC Request For Additional Information, 9504100037 950403 PDR ADOCK 05000282 f}h l
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ATTACHMENT 1 Response to March 8. 1995 NRC Reauest For Additional Information The following information is provided in response to requests for additional information received from the NRC Staff related to the Prairic Island License
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Amendment Request for the F*/L* steam generator repair criteria:
i Question A-5:
The staff compared your proposed wording to that approved for the Summer nuclear plant. The licensee for Summer chose an L* distance (0.7 inch)'that l
includes 0.2 inch for eddy current measurement uncertainty. Northern States chose an L* distance of 0.5 inch not including eddy current uncertainty.
Please contarvatively specify an L* distance that includes addy current uncertainty.
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Answer:
f The L* distance for Prairie Island will be 0.7 inches which includes an eddy current uncertainty of 0.2 inches. The bases for Technical Specification 4.12 as proposed in our January 9,1995 License Amendment Request will be revised to incorporate this information and will be resubmitted along with the change i
to Technical Specification 4.12.D.l. (m) described below.
Question A-6. Part 1:
Please reword the first sentence defining an L* tube because it is unclear.
Answer:
Technical Specification 4.12.D.l.(m) as proposed in our January 9,1995 License Amendment Request will be revised and resubmitted with the following j
wording:
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- (m)
L* tube is a tube with short (less than 0.5 inches) axially oriented (20 degrees or less from axial) degradation occurring below the undegraded L* distance. An additional minimum of 0.04 inches (not l
including eddy current uncertainty) of sound expanded tube (below the L* distance) separated by no more than 2 areas of axially oriented l
degradations must be contained in the top three inches of tube (within the tubesheet).
Each area of degradation is lindted to a maximum of 5 distinct indications. A maximum of 600 tube ends per steam generator may utilize L*.
Tubes qualifying as F* tubes are not classified as L*
tubes.
L* tubes will be inspected with the rotating pancake coil system (or equivalent technology) in the top 2.8 inches of the roll l
expanded region to adequately characterize the degradation. When the l
hard roll region meets the criterion for F*,
the F* criterion applies 6
and the tube end would not be counted in the 600 tube limit."
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Attechment USNRC April 3, 1995 Page 2 of 3 i
Question A-6. Part 2:
Also, explain why your definition of an L* tube appears to be much less conservative than that of Summer.
The definition the staff approved for Summer defines an L* tube as a tube with short (less than 0.5 inch) axially oriented (20 degrees or less from axial) degradation occurring below the undegraded L* distance. An additional minimum of 1.0 inch of sound tube (below the L* distance) separated by no more than two areas of axially oriented degradations must be contained in the top 3.5 inches of tube (within the tubesheet).
Each area of degradation is limited to a maximum of five distinct indications. A maximum of 2500 tube ends per steam generator may utilize L*.
Tubes qualifying as F* tubes are not classified as L* tubes.
Answer:
The Prairie Island L* definition is taken from WCAP-14225.
Discussions with VC Summer personnel identified their criteria were arbitrarily set more conservative than the Westinghouse criteria.
At this time, we propose the following criteria:
The L* inspection length shall be the uppermost three inches of the hard e
roll expansion measured from the bottom of the hard roll transition.
The L* distance shall be 0.7 inches of sound roll expansion which e
includes 0.2 inch of uncertainty, Within the 2.3 inches below the L* region there shall be no more than 2 e
distinct bands of indications which contain axial indications (No other type of indications is allowed).
Axial indications allowed in the bands shall be no longer than 0.5 inch.
e There shell be no more than 5 axial indications in each band e
Axial indications can be up to 20 degrees from the vertical line.
e Question L-1:
As above, conservatively specify a value that includes addy current measurement uncertainty and the bases for the value.
Answer:
The L* region encompasses the L* distance, the additional sound roll expansion and up to two separated bands of indications. The L* distance for Prairie Island is 0.5 inches plus an eddy current uncertainty of 0.2 inches. The additional sound roll expansion distance is 0.84 inches plus an eddy current uncertainty of 0.2 inches.
The additional sound roll expansion distance is the difference between the total 1.34 inch WCAP-14225 distance minus the L*
distance.
The two bands of axial degradation can be as much as 0.5 inches j
each, for a total possible length of 1.0 inch. There is no eddy current uncertainty applied to the axial degradation distance since the roll transition zone is only 0.25 inches long. The sum of these distances (2.74 inches) is the length of the L* inspection region which is conservatively rounded to 3.0 inches.
The bases for Technical Specification 4.12 as proposed in our January 9,1995 License Amendment Request will be revised to incorporate this information and i
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- s Attcchment USNRC i
April 3, 1995 j
Page,3 of'3 l
will be resubmitted along with the change to Technical Specification 4.12.D.1.[m) described above.
Question L-2:
Please specify the total length of tube you plan to inspect and the inspection techniques.
Answer:
l The total length of tubing to be examined for L* criteria is the lower ten inches of the tubesheet region.
The inspection will be done with rotating l
pancake coil probes (or equivalent technology).
Ouestion L-3:
1 The staff will require that there be a performance demonstration of the adequacy of the inspection method used to characterize the indications to be left in service under the use of the L* criteria.
i Answer:
There v111 be a performance demonstration of the adequacy of the inspection I
method used to characterize the indications to be left in service under the use of the L* criteria prior to the first implementation of the L* criteria in the Prairie Island Steam generators.
Question L-4:
i The staff plans to perform an independent evaluation of the stress analysis justifying the L* criteria. This will be conducted by the Mechanical Engineering Branch, NRR.
It is anticipated that there will be further requests for additional information.
Answer:
No response to this item is required.