ML20079L745
| ML20079L745 | |
| Person / Time | |
|---|---|
| Site: | Summer  |
| Issue date: | 02/14/1983 |
| From: | Dixon O SOUTH CAROLINA ELECTRIC & GAS CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8302230432 | |
| Download: ML20079L745 (8) | |
Text
f SOUTH CAROLINA ELECTRIC & GAS COMPANY eost orrica vos CoLuneetA. south CAROLINA 29218 O.W.DFXON,JR.
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February 14, 19'83 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555
Subject:
V'irgil C. Summer Nuclear Station Docket No. 50/395 Operating License No. NPF-12 0perating License Condition 2.C.14
Dear Mr. Denton:
This letter is provided in response to Operating License Condition 2.C.14.
This condition required South Carolina Electric and Gas Company (SCE&G) to provide a description of the proposed modifications to our_ Model D-3 Westinghouse Steam Generator. The modification developed by Westinghouse, which will be installed at the Virgil C. Summer Nuclear Station, is summarized in the Westinghouse Report, " Westinghouse Preheat Steam Generator - D2/D3 Design Modification Evaluation Package," December 1982, and addenda. These have been submitted to the NRC.
A Design Review Panel, composed of members from Duke Power Company, TVA and SCE&G has performed an independent design review of the modification. The
" Utility Design Review Panel Evaluation Report, D2/D3 Steam Generator Design Modifications, January 1983," has been provided to the NRr. in a submittal from S. K.
Blackley to H. R. Denton on January 19, 1983. The Evaluation Report relies extensively on technical data in the Westinghouse Report.
As noted in the design review report, the Design Review Panel (DRP) concluded that the modification to the D2/03 steam generator preheater section can be installed and the steam generator can be operated safely.
In particular, the DRP concluded:
o The modification to the D2/03 steam generators does not represent an unreviewed safety question under 10CFR50.59.
o The modification will result in reduced tube vibration by minimizing turbulence in the preheater section.
EK)D2230432 830214 PDR ADOCK 05000395 P
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l Harold R. Denton Operating License Condition 2.C.14 February 14, 1983
-Page-f2 o The modification is. structurally sound and capable of withstanding plant. transients, provided the plant is operated within specified limits identified in the DRP Evaluation Report.
o Adequate consideration has been given to installation methods.and controls including welding processes, NDE requirements, chemistry / cleanliness control and Ai. ARA principles.
o Inservice inspection and testing for modified plants will provide sufficient evidence that the modification reduces tube wear rates to acceptably low values, o After the modification, the steam generator can be safely operated at 100% design capacity.
The DRP Evaluation Report identified several items which should be addressed specifically by each plant owner. These are listed below with the SCE&G responses.
1.
Provisions should be made for intitial monitoring of-inlet pressure oscillations (Section 5.2).
O Pressure transducers for detection of feedwater pressure pulsations are installed in each feedwater line adjacent.to the steam generator feedwater nozzle.
To verify that the plant specific feedwater system performance corresponds to the analysis assumptions, the feedwater inlet nozzle pressure oscillations will be monitored throughout the design operating flow ranges during the power escalation period following installation of the preheater modification. Monitoring will be performed during subsequent periods if necessary to obtain additional or missed data.
2.
Plant specific provisions for assuring feedwater flow and/or feedwater temperature restrictions are met should be described (Section 6.0).
o In order to assure adequate stress margins in the bolting of the modification manifold assembly, operating limits on feedwater flow rates and temperature have been established. The limits require that (1) for feedwater at 32*F, the minimum flow must be at least 2.5% of design flow to ensure adequate stress margins, or (2) for
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F Harold R. Denton Operating License Condition 2.C.14 February 14, 1983 Page 13 feedwater at or above 200*F, no.ninimum-flow rate is required.
SCE&G intends to provide assurance of a minimum feedwater temperature of 200*F.
through design changes in the main feedwater system. This will be accomplished by providing a reverse flushing scheme from the steam generator back to the Feedwater Isolation Valve (FIV) and forward flushing up to the FIV. Temperature and flow permissives will be incorporated and must be met for an appropriate period of time for both reverse and forward flushing to allow opening the FIV. These changes will be made during the plant shutdown to modify the steam generators. They have been evaluated under 10CFR50.f9 and do not represent an unreviewed safety question. Any aspect of this design modification which changes prior to implementation will be reevaluated under 10CFR50.59 accordingly. A simplied flow diagram of the design modifications is shown in Figure 1.
3.
Inservice inspection and eddy current testing monitoring programs and schedules should be described (Section 5.8).
o To assess the long term integrity of the manifold and the effects of'the modification on the steam generator components, a visual inspection program will be performed. To assess the performance of the modification with respect to tube wear, an eddy current test (ECT) program will be performed.
Visual Inspection The visual inspection will be general in nature. As much of the assembly as is accessible will be inspected with oarticular emphasis on any critical areas.
The general inspection will cover three major areas:
- 1) Mechanical inspection
- 2) Weld inspection 3)
Sludge / deposit inspection The scope of the internal man; fold assembly visual inspection will include accessible areas. With respect to applied mechanical loads, feedwater flow loads and adverse chemical build-up, no critical areas have been identified. The primary goal of the inspection is to ascertain the overall integrity of the assembly after a period of power operation.
In addition, this inspection will allow the identification
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Harold R. Denton Operating License Condition 2.C.14 February 14, 1983 Page #4 of impending problems. The scope of the inspection will include, as accessible, a survey for mating surface gaps, fretting / wear, erosion, corrosion, service induced cracking, sludge / deposit buildup and loose parts. The accessible manifold f asteners will also be inspected to ensure that the locking clips are engaged and intact. Based on the results of the examination, remedial programs will be developed to
' address any. problem areas.
Access to' the manifold can be gained through a port. This small opening allows inspection of portions of the manifold and manifold inlet assembly,' including the flow limiter, fla splitter, manifold boxes and associated welds. The primary inspection tool will be a fiberoptic boroscope or equivalent guided to the areas of interest manually.
A visual inspection will be performed concurrent'with the first shutdown for eddy current inspection after the modification.
Followup inspections will be based on the results of the first inspection after power operation.
Eddy Current Inspection The primary area of interest for the ECT program for the steam generators are Rows 45 through 49, all columns.
The tubes in these rows will be inspected as part of the preheater modification verification program. Table 1 is a list of the tubes to be examined. The cold leg side of the tubes will be inspected from support plate 1 through support plate 10.
The ECT program is'the primary means of assessing in-plant performance of the_ modification. Comparison between the initial examination results and results after a period of power operation will be used to determine whether the modification is effective in eliminating tube wear.
In addition, these data will be used to determine the scope and nature of follow-up examination deemed appropriate.
The ECT program recommended by SCE&G is summarized in Table 2. The ECT program includes those tubes which are most likely to oe affected by the modification. Because the modification is expected to reduce the rate of tube wear to an acceptably small value, only those tubes suspec+.ed to be principally affected by excessive wear mechanisms will need to be included in the inspection program.
Harold R. Denton Operating License Condition 2.C.14 February 14, 1983 Page #3 A multifrequency eddy current inspection will be performed utilizing the wear scar standard and will be conducted at the time of installation of the modification. This inspection will serve as a baseline for future inspections. The next ECT inspection will be performed prior to approximately six (6) effective full power months of operation. After this inspection, the inspection interval will be determined based on the measured wear rate.
The information included and referenced-in this submittal is provided to meet the requirements of Operating License Condition 2.C.14.
It is requested that a review of this material be conducted and completed prior to March 1, 1983.
fhis will allow resolution of this license condition and NRC concurrenc~e prior to shutting down the Virgil C. Summer Nuclear Station.for performing the steam generator modifications, which are scheduled for early March.
If you have any questions, please contact us.
Very truly ours,
/
- 0. W. Di n, J.
AMP:RBC:0WD/fjc Attachments:
cc:
V. C. Summer
- 0. S. Bradham E. C. Roberts A. R. Koon H. N. Cyrus C. A. Price T. C. Nichols, Jr.
G. J. Braddick
- 0. W. Dixon, Jr.
J. C. Miller M. B. Whitaker, Jr.
J. L. Skolds J. P. O'Reilly J. B. Knotts, Jr.
H. T. B abb B. A. Bursey D. A. Nauman F. K. Mangan C. L. Ligon (NSRC)
NPCF W. A. Williams, Jr.
File R. B. Clary
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'I TABLE l' Tubes To Be Inspected for Preheater Modification Verification Preheater Inlet Region Row Colurn 49 31 through 84 48 29 through 86 47 28 through 87 46 26' through 99 45 25 through 90 t
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TABLE 21 Eddy Current Test-Program Location Time Sequence
- Reas'on Preheater inlet 1.:Afte'r modification
. Baseline.for preheater 5 rows (45-49) prior to startup-modification perfor-(cold leg only)
'mance verification
- 2. Af ter power opera-Establish the tube tion pericd cf wear rate of the approximately_.
modified steam six (6) effective generators forf input
' full power months-
_ to.the Inservice-Inspection Program
_