ML20081F059
| ML20081F059 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 03/15/1995 |
| From: | Saccomando D COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 9503210519 | |
| Download: ML20081F059 (6) | |
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Commonwealth Edison Company
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Downers Grose, IL M)il5 March 15, 1995 Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Attn:
Document Control
Subject:
Response to Questions Identified in NRC Meeting Summary Regarding Pending License Amendment to Increase the. Steam Generator Tube Voltage-Based Repair Limits for Byron Unit 1 and Braidwood Unit 1 NRC Docket Numbers 50-454 and 50-456
Reference:
M.
Lynch letter to-Commonwealth Edison Company dated March-14, 1995, Summarizing the February 23, 1995, Meeting on the Pending License Amendments Raising the Steam Generator Tube Voltage-Based Repair Limits for Byron Unit 1 and Braidwood Unit 1
On February 23, 1995, Commonwealth Edison Company (Comed) met with the Nuclear Regulatory Commission (NRC) to discuss technical issues of the proposed license amendments regarding the increase in the interim plugging criteria (IPC) for the Byron Unit 1 and Braidwood Unit 1 steam generators. As a results of that meeting, the reference meeting summary was issued which included four NRC concerns.
Concern #1:
ComF5 a proposed POD model A status of Co'.nEd's evaluation of items identified by the Staff will be provided to the NRC at an upcoming Comed /NRC meeting.
Comed will p'. ovide a written response to the Staff by the end of April.
Concern #2:
Comed proposed analytical model representing steam generator tube leakage.
Comed will provide the Staff with data which will quantify the potential benefit from using this analytical leakage model by March 20, 1995. In addition, data will be provide to the Staff which will address the model's sensitivity to various PODS.
Concern #3:
Development of an alternate model representing steam generator tube leakage.
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NRC Document Control Desk March 15, 1995 Comed is pursuing use of an alternate model which does not rely on a bobbin voltage correlation with crack length. This model is being developed and a description of this model will be provided to the Staff by March 20. 1995.
Also on March 20, 1995, the Staff will be provided with results quantifying this model's potential benefit. Pending evaluation of results of this model, the model submitted in the proposed Technical Specification amendment, and the laboratory leak test results, Comed may have to revise / create a new leakage model which will then require a supplement to our proposed. Technical Specification amendment.
Concern #4 Development of experimental database to validate analytical leakage model In an effort to obtain bounding leak rates for steam generator indications which have been restricted from burst by the presence of the tube support plate, EPRI is sponsoring a laboratory test program. This program will be performed by Westinghouse Electric Corporation. A description of the test program is included in the attachment.
The plans and preliminary results from this test program will be reviewed by the EPRI SGDSM Ad-Hoc committee which is scheduled to meet in early April. Guidance from the committee will be factored into the leak rate model, and the need for any additional testing or modifications will be determined.
The goal of this program is to determine bounding leak rate values which can be used to update analysis models and perform a probabilistic calculation of leakage due to the fact that probability of burst will be eliminated by " locking" the tube support plates in place, such as is being proposed for Byron and Braidwood.
The room temperature leak rate tests are expected to be completed in early April in time for the SGDSM Ad-Hoc committee meeting.
The operating temperature leak rate tests should be completed by the end of April depending on the scope of modifications needed to the existing test facility.
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NRC Document Control Desk March 15, 1995 Comed and the NRC are currently discussing tentative dates for a proposed meeting to further explore these four technical issues.
Comed looks forward to meeting with the Staff.
Please address any questions or comments concerning this correspondence to this office.
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Denise M.
Sacbodando Nuclear Licensing Administrator Attachment cc:
D.
Lynch, Senior Project Manager-NRR R. Assa, Braidwood Project Manager-NRR G. Dick, Byron Project Manager-NFS S. Dupont, Senior Resident Inspector-Braidwood H.
Peterson, Senior Resident Inspector-Byron J. Martin, Regional Administrator-RIII Office of Nuclear Safety-IDNS K NLA\\BYBWD SEEN\\3VOLTRAI\\3
ATTACHMENT Test Plan for Obtainina Boundina SLB Leak Rate for Indications Restricted From Burst By The Tube SuoDort Plate (TSP)
OBJECTIVES:
Obtain bounding SLB leak rates for SG tubes restricted from burst by the presence of the tube support plate.
- Obtain SLB leak rates for same indications with 0.1" of the crack length extending outside of TSP.
. Characterize the crack opening shape, area and crack extension for these type of indications.
Definition of Indication Restricted from Burst by the TSP Although ODSCC which is confined within a TSP is restricted from burst, an indication could develop for which the crack face would open wider inside the TSP than obtained for the EPRI free span leak rate correlation, such as might occur for an indication that would burst in free span.
- For the purposes of this proposed test program, indications which are restricted from burst will be obtained by pressurizing the indication with a bladder to about 15% above the calculated burst pressure for the indications as defined by UT examination and dye penetrant results.
SUMMARY
PROGRAM DESCRIPTION: (additional details attached)
. Perform leak rate tests on 3 specimens (available in 7/8" tubing)
. Perform dye penetrant testing of specimens to supplement UT data and calculate the free span burst pressures for each specimen.
. Test sequence for each specimen to include the following:
-Center crack within simulated tube support plate " clamshell" and pressurize the indication to 15% above the calculated burst pressure to achieve full crack opening.
-Perform room temperature leak test on each specimen at three pressure differentials up to 2560 psid.
-Repeat the leak test at operating temperature for at least 2 of the 3 specimens.
-Measure the size of the crack area, length and diameter after removal of the clamshell.
-Move the specimen to expose about 0.1" of the crack length and measure leak rate at room temperature and operating temperature if within test facility capacity.
-Measure the size of the crack area, length and diameter after removal from the clamshell.
-Document test results
- Evaluate test results xmunavmounomuvotnan4 i
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a Test Plan for Obtainina Boundina SLB Leak Rate for Indications Restricted From Burst By The Tube Sunnort Plate (TSP)
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Details of Test Procram GENERAL TEST REQUIREMENTS:
+ Utilize a clamshell TSP simulant to facilitate inspections of the crack openings after and between leak tests. The simulated support plate will form a 0.023" tube to support plate gap.
. Deionized water for leak tests LEAK RATE TESTS (7/8" Diameter Test Specimens):
. Perform dye penetrant test on the three test specimens q
identified below to obtain ID and OD crack lengths for comparison with UT data. Based on this data, calculate burst pressure.
Test 1: Specimen 4B 220 (0.34" Axial Throughwall Length)
- Room temperature leak rate tests
-With the crack centered within the TSP, pressurize the specimen with a bladder to 15% above the calculated burst pressure to assure an equivalent free span burst pressure is obtained.
-Perform leak rate measurements at AP = 2200, 2400, 2560 psid
-Remove specimen from TSP, measure crack opening width, area and tube diameter across crack opening as a function of axial location from crack center.
-Move crack edge closest to TW to 0.10 (max 0.15") outside TSP and repressurize the specimen with a bladder to the same burst pressure as previously applied above.
-Perform leak rate measurements at same pressure differentials performed for the centered crack with a maximum of 2560 psid
-Remove specimen from TSP, measure crack opening width, and tube diameter across crack opening as a function of axial location from crack center.
- Retain specimen for possible retest at temperature if necessary following tests 2 and 3.
. Measure corrosion depth versus length for the crack Test 2: Specimen 4B 218 (0.40" Axial Throughwall Length)
- With the crack centered within the TSP, pressurize the specimen with a bladder to 15% above the calculated burst pressure to assure an equivalent free span burst pressure is obtained.
-Perform room temperature leak rate measurements at AP = 2200, 2400, 2560'psid.
-Repeat leak rate measurements for same pressure differentials at operating temperatures.
-Remove specimen from TSP, measure crack opening width, area K:NLA\\BYBWD\\STGEN\\3VOLTRAI\\5
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and tube diameter across crack opening as a function of axial location from crack center.
. Move crack edge closest to TW to 0.10 (max 0.15") outside TSP and repressurize the specimen with a bladder to the same burst pressure as previously applied above.
-Perform room temperature leak rate measurements at same pressure differentials performed for the crack centered with a maximum of 2560 psid.
-Repeat leak rate measurements for the same pressure differentials at operating temperatures.
-Remove specimen from TSP, measure crack opening width, area and tube diameter across crack opening as a function of axial location from crack center.
. Measure corrosion depth versus length of the crack Test 3: Specimen 4B 214 (0.50" Axial Throughwall Length)
. Test sequence same as test 2 K : NLA\\ BYBh"O\\ STGEN \\ 3 VOLTRAI \\ 6