ML20056G726

Responds to NRC 930625 Request for Addl Info Re Generic Ltr 92-01,Rev 1, Reactor Vessel Structural Integrity

ML20056G726
Person / Time
Site:	Monticello
Issue date:	08/27/1993
From:	Richard Anderson NORTHERN STATES POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GL-92-01, GL-92-1, TAC-M83485, NUDOCS 9309070094
Download: ML20056G726 (6)

Text

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2 Northem States Power Company 414 Nicollet Matt Minneapolis, Minnesota 55401 1927 Telephone (612) 330-5500 August 27, 1993 US Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C.

20555 MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 License No. DPR-22 f

Response to Request for Additional Information Concerning Generic Letter 92-01. Revision 1. " Reactor Vessel Structural Interrity" (TAC No. M83485)

As requested by your letter of June 25, 1993, we are hereby providing our written responses to your questions concerning our July 6, 1992 submittal which provided the information requested by NRC Generic Letter 92-01, Revision 1, " Reactor Vessel Structural Integrity" The specif"c response (s) to each of your questions is contained in Attachment A.

This letter contains the following new NRC commitment:

The copy of NEDO-32205 submitted to the NRC on April 30, 1993 will be used as our licensing basis to demonstrate that all beltline plates and welds meet the Upper Shelf Energy (USE) requirements of Appendix G, 10 CFR Part 50.

Please contact Terry Coss, Sr Licensing Engineer, at (612) 295-1449 if you require additional information.

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s &,Mrk w R er 0 Anderson Director Licensing and Management Issues cc: Regional Administrator-III, NRC NRR Project Manager, NRC Resident Inspector, NRC State of Minnesota, Attn: Kris Sanda l j.h J Silberg i

p Attachment A:

Additional Information Concerning the Monticello Response to GL 92-01, Rev 1 9309070094 930827 7

PDR ADOCK 05000263 P

PDR

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Attachment A

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August 27, 1993 Page 1 i

i Attachment A j

Additional Information Concerning the Monticello Response to GL 92-01, Rev 1 Our response to your Letter of June 25, 1993 is as follows:

Ouestion 2.a.

"Your July 6, 1992 response indicates that the initial upper shelf energy (USE) values for all beltline plates and welds, except for the surveillance materials, are not known. A topical report, NEDO-32205, titled 'BWR Owners' Group Topical Report on Upper Shelf Energy Equivalent Margin Analysis' rega.-ding beltline materials with low USE, j

was submitted by General Electric Corporation on April 30, 1993. Please confirm that this topical report vill be used as your licensing bases to demonstrate that all beltline plates and welds will meet the USE tcquirements of Appendix G, 10 CYR Part 50."

NSP Response: The copy of NEDO-32205 submitted to the NRC on April 30, 1993 will be used as our licensing basis to demonstrate that all beltline plates and welds meet the Upper Shelf Energy (USE) requirements of Appendix G,10- CFR Part 50.

The report has been used with the Charpy results for 10 'F test temperature from the original Certified Material Test Reports of the beltline plates to determine the end of life upper shelf energy of the Monticello j

reactor vessel. A summary of these results using Appendix B of NEDO-32205 is provided with this response to demonstrate an " Equivalent Margin Analysis".

Ouestion 2.b (Part 1):

i "Your response indicates that dsta from the drop veight test and Charpy test for beltline materials is either absent or incomplete for initial l

RTun determination. An alternative method developed by General j

Electric (GE) was used in deriving the initial Ring for these materials.

In the GE method, the establishment of the slope for the l

I transition zone of the Charpy curve is crucial in deriving the initial' RTun from incomplete test data.

Please provide all plate and veld Charpy test curves compiled by GE for establishing the 2 *F per ft-1b slope for the transition zone of the Charpy curve. All test data must be from materials equivalent to (i. e., same vendor, fabrication time-f:sme, fabrication process, material specification, etc.) the beltline materials of this reactor vessel."

NSP Response:

The BWR Owners' Group is preparing a generic response on this issue. The response is expected to be submitted to the full owners' group in

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Attachment A i

August 27, 1993 Page 2 late August or early September of this year. Monticello will use this generic response as the basis for our RTmg shift analysis.

The generic submittal will include the information CE has used to develop it's shift calculational method.

Question 2.b.

(Part 2):

"Your response also indicates that chemistry data for plates I-14, I-16 and I-17 are not known. Provide the values of ~opper, nickel, phosphorus, sulfur and neutron fluences that were used to predict the increase in transition temperature and drop in USE for these plates, i

Provide justification for using these values."

I NSP Response: The Chemistries for the plates 1-14, I-15, I-16 and I-17 are known and can be found in Appendix C, pages 1-4, of our July 6, 1992 response to Generic Letter 92-01, Revision 1.

This information also appears in a i

summary table (Table 4.2.3.2-1 of the Suggested Revision to the Updated Final Safety Analysis Report (UFSAR)) that was included in our July 6,1992 response. The Copper values given in the USAR table are valid for the plates, l

and were obtained in previous work via contact with Luken's Steel, who has records that include Cu content for the heats used in the formation of the plates used at Monticello.

As indicated in our earlier response, we do not have specific chemistry values assigned to specific beltline welds. We do, however, have the chemistries (with the exception of Copper content) for all of the weld wire used in the vessel welds at Monticello.

Therefore, the value for Ni used in the RTmy shift calculation was the highest value found in the weld wire. chemistries, which yields a conservative RTun.

The 0.1 % Copper value used in the RTun calculations was a limit previously accepted and utilized by the NRC in a Safety Evaluation Report attached to a letter from V S Noonan, Assistant Director for Materials and Qualifications Engineering, Division of Engineering (NRC), to T M Novak, Assistant Director for Operating Reactors, Division of i

Licensing (NRC),' dated January 21, 1981, titled " Northern States Power Company, Monticello Nuclear Generating Plant. Revision of Pressure-Temperature Operating Limits in Technical Specifications (TAC 42360)"

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3 A

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NEDO-32205 APPENDIX B PLANT-SPECIFIC APPLICABILITY The evaluations in Section 8, which demon.;trate that the equivalent margin analyses are bounciag for all U.S. BWR/2-6 vessels, are based on an important assumption, which must be verified on a plant-specific basis. It is assumed that the percent decreases in USE prescribed by R.G.1.99 are appropriate for a given vessel's beltline materials. The validity of this assumption can be verified with vessel surveillance capsule USE data, when it becomes available.

Obviously, if the surveillance data show a decrease in USE less than predicted in R.G.1.99, the equivalent margin analysis is bounding for the plant. Example 1 below for weld metal demonstrates this case.

Example _1: Surveillance data < R.G.1.99 prediction Decrease in USE for surveillance material, based on capsule data = 9%

Decrease in USE for surveillance material, predicted by R.G.1.99 = 15%

32 EFPY USE decrease forlimiting beltline weld, based on R.G.1.99 prediction =20%

32 EFPY % decrease in USE assumed in equivalent margin analysis = 33%

207o.<_33fc, so vessel beltline welds are bounded bv eauivalent marcin analysis B-1

o NEDO-32205 -

,s g1 EQUIVALENT MARGIN ANALYSIS PLANT APPLICABILITY VERIFICATION FORM BWR/3-6 PLATE Surveillance Plate USE:

%Cu =

0.168

)

Capsule Fluence =

3.0 x 1017

)

1 Measured % Decrease =

_ (Charpy Curves) 14 R.G. 1.99 Predicted % Decrease =

(R.G. 1.99, Figure 2)

Limitina Beltline Plate USE:

%Cu =

0.17 M

2 3.8 x 10 n/m l

32 EFPY Fluence =

)

21 R.G. 1.99 Predicted % Decrease =

(R.G. 1.99, Figure 2)

"I^

Adjusted % Decrease =

(R.G. 1.99, Position 2.2)

(0.nly one data point'. not adequate for this suggested analysis.)

21% s 21%, so vessel plates are bounded by equivalent margin analysis Filled in by Mark Hugo, 7/22/93 mp-r

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- NEDO-32205 EQUIVALENT MARGIN ANALYSIS PLANT APPLICABILITY VERIFICATION FORM BWR/2-6 WELD' Surveillance Weld USE:

0 10

%Cu =

17 2

3.0 x 10 n/cm Capsule Fluence =

0 Measured % Decrease = _

(Charpy Curves) 8 R.G. J.99 Predicted % De9rease =

(R.G. 1.99, Figure 2) i s

Limitina Beltline Weld USE:

0'10

%Cu =

2 3.8 x 1018 n/cm 32 EFPY Fluence =

i 17%

R.G. 1.99. Predicted % Decrease =

(R.G. 1.99, Figure 2) t N/A Adjusted % Decrease =

(R.G. 1.99, Position 2.2)

(Only one data point, not. adequate for this suggested analysis.)

P 17% < 33%, so vessel welds are bounded by equivalent margin analysis Filled in by Mark Hugo, 7/22/93 Y

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