ML20140B602
| ML20140B602 | |
| Person / Time | |
|---|---|
| Site: | Peach Bottom  |
| Issue date: | 05/20/1997 |
| From: | Hunger G PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-80-013, IEB-80-13, NUDOCS 9706060261 | |
| Download: ML20140B602 (5) | |
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IEB 80-13 PECO NUCLEAR nm o-c-9ti5 Chesterbrook Boulevard A Unit of PECO Energy Wayne, PA 19087-5691 May 20,1997 Docket No. 50-278 License No. DPR-56 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D.C. 20555
Subject:
Peach Bottom Atomic Power Station, Unit 3 Reactor Vessel Intemals Examination Plans for the Core Spray Piping
References:
1.
Letter from J. W. Shea (U. S. Nuclear Regulatory Commission) to G. A. Hunger, Jr. (PECO Energy Company) dated November 15,1996 i
Dear Sir This letter is in response to the Roference 1 letter which requested our plans for the i
inspection of the Peach Bottom Atomic Power Station (PBAPS), Unit 3 Core Spray piping and spargers for the upcoming refueling outage (3R11), currently scheduled to begin in October,1997. As also discussed in the Reference 1 letter, the inspection plans should take into account any staff generic evaluations of the BWRVIP-18, "BWR Core Spray Intemals inspection and Flaw Evaluation Guidelines," dated July,1996, available prior to the outage. As of the issuance of this letter, no staff generic evaluations have been issued.
Augmented visual examinations of the Core Spray System piping and spargers inside the reactor vessel have been conducted each refueling outage since 1980, as requested by Bulletin 80-13, " Cracking in Core Spiay Spargers," dated May 12, 1980. These examinations have been implemented in accordance with the PBAPS Augmented Inspection Program 3 (AUG-03). Implementation of this program will be modified for the upcoming refueling outage, to incorporate industry experience, and to more closely follow the current guidance developed by the BWRVIP ("BWR Core Spray internals Inspection and Flaw Evaluation Guidelines," BWRVIP-18, dated July,1996). Use of BWRVIP-18 was previously approved for PBAPS, Unit 2 by the U. S. Nuclear Regulatory Commission (USNRC) in the Reference 1 letter.
l The modifications will affect scope and examination technique. The adjustments to the examinations will focus more attention on the welds and their heat affected zones, utilizing an enhanced visual examination of the areas where degradation is more likely to occur, and will eliminate the detailed examination of the piping base metal between the welds. Also included in this inspection will be the repair clamps located on the Core Spray downcomer welds at the spigot / sleeve joint, connecting f
the downcomer to the sparger inlet elbow, which were installed on PBAPS, Unit 3 y
during 3R10.
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Attached are our conclusions regarding the ability of the Core Spray System to continue to perform its intended safety function as a. result of the revised
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inspections.
if you have any questions, please contact us.
I Very tnaly yours,
. Q.
, n.
G. A. Hunger, Jr.
Director-Licensing
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cc:
H. J. Miller, Administrator, Region I, USNRC W. L. Schmidt, USNRC Senior Resident inspector, PBAPS 3
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PECO ENERGY COMPANY PEACH BOTTOM ATOMIC POWER STATION
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UNIT 3 REACTOR PRESSURE VESSEL INTERNALS AUGMENTED INSPECTION PROGRAM CORE SPRAY SYSTEM PBAPS Unit 3 (3R11)
BACKGROUND PECO Energy Company has been performing augmented examinations of the Core l
Spray System piping inside the reactor vessel since 1980. The augmented inspection program for Core Spray internals was developed and implemented as a result of the l
requirements of U. S. Nuclear Regulatory Commission (USNRC)Bulletin 80-13. During each refueling outage since 1980, Peach Bottom, Units 2 and 3 Core Spray piping and spargers have been visually examined for any indication of degradation. The visual examinations performed used a resolution standard of.001", as required by the Bulletin. The augmented inspection program also considered guidance suggested by General Electric Company's Service Information Letter (SIL) No. 289.
To date, PBAPS, Unit 3 examinations have revealed cracks in the heat affected zone of creviced welds on the four Core Spray downcomers. These cracks were repaired with permanently installad clamps over the affected sections of the piping. This repair was approved in your letter dated October 13,1995 (letter from J.F. Stolz (U. S. Nuclear Regulatory Commission (USNRC) to G. A. Hunger, Jr. (PECO Energy)). Additionally, as discussed in our letter dated November 8,1985 (letter from S. L. Daltroff (Philadelphia Electric Company) to J. F. Stolz (USNRC)), two cracks were identified in the heat affected zone of the piping to junction box weld of the "A" Core Spray piping i
header tee box. These cracks were repaired with welded brackets installed on the "A" header tee box. Brackets were also installed on the "B" header tee box although no cracks were identified.
Utilizing additional industry experience gained since 1980 in the area of examination, evaluation, analysis, and repair of this system, the Boiling Water Reactor Vessel and Internals Project (BWRVIP) developed a comprehensive guideline for the inspection and evaluation of this piping. This guidance, BWRVIP-18, "BWR Core Spray internals inspection and Flaw Evaluation Guidelines", was submitted to the USNRC for review on July 26,1996. The intention of the BWRVIP document is to supersede the GE SIL and Bulletin requirements for examination of this piping.
PBAPS UNIT 3 PLANNING Considering the industry experience regarding Core Spray internals cracking contained in the BWRVIP guidelines (i.e. Table 3-1) and PBAPS site specific experience with such cracking, a decision was made to enhance the existing augmented inspection program for the PBAPS Units 2 and 3 Core Spray internals, beginning with the eleventh refueling outage for PBAPS, Units 2 and 3. The basis for the change was to focus additional resources and time on the areas of the Core Spray piping which have shown 1
l a susceptibility to cracking (i.e. creviced welds), and to adjust examinations of areas not found to be susceptible to cracking (i.e. piping base metal). To achieve this enhancement, PECO Energy upgraded the existing Augmented inspection Program 3 (AUG-03) to reflect the guidance provided in the BWRVIP Guidelines (i.e.
This upgrade was implemented by first itemizing and detailing all PBAPS specific susceptible areas on program tables and Inservice Inspection (ISI) drawings, as recommended by the BWRVIP-18, Table 3-2. These susceptible areas were then assigned the BWRVIP recommended examination technique. Both Ultrasonic Testing (UT) and Visual Testing (VT) techniques are described as options in the BWRVIP-18.
The visual technique was selected for the PBAPS, Unit 3 upcoming refueling outage (3R11), utilizing an enhanced resolution requirement of.0005". This technique, identified as Enhanced VT-1 (EVT-1), was chosen because of the successful application of similar techniques during previous PBAPS inspections.
The examinations performed during the previous refueling outage at PBAPS, Unit 3 (3R10) were reviewed and compared to the recommended baseline examinations of the BWRVIP-18 document. This review determined that the examination of the annulus portion of the Core Spray internals did not meet the intent of BWRVIP-18. The entire annulus piping portion of the Core Spray internals was inspected during 3R10.
However, the technique used during 3R10 was equivalent to the Core Spray VT-1, which requires only a.001" resolution. Therefore, the recommended baseline examinations were not satisfied and have been scheduled for implementation during the upcoming outage. In accordance with Figure 3-1 of the BWRVIP-18, all applicable accessible Core Spray annulus piping welds have been scheduled for examination using the EVT-1 technique.
For the sparger portions of the Core Spray internals, the examinations performed 1
during 3R10 included the recommended scope, and actually exceeded the recommended examination techniques. Therefore, in accordance with Section 3.2 of the BWRVIP-18, the baseline examination recommendations (Figure 3-2) for the sparger portion of the Core Spray intemals have been satisfied during 3R10. The reinspection recommendations of the BWRVIP-18 (Figure 3-4) were reviewed. The reinspection recommendations require examination of a specific scope of welds every two cycles. PBAPS is not "sparger geometry critical" as defined in Section 3.2.3 of BWRVIP-18. All of the sparger piping, nozzles, and brackets were examined using the CS VT-1 (i.e. 001 " resolution) technique. This technique is superior to that recommended for the nozzle welds and sparger brackets. Accordingly, no examinations are required to be performed during the upcoming outage on this portion of the Core Spray internals.
The repair ple's welds installed on the "A" and "B" header tee box have been scheduled for examination during 3R11. The examination technique for these welds is the VT-1 technique. Additionally, the four repair clamps installed on the downcomers will also be examined using the VT-1 technique.
The administrative and reporting requirements of the AUG-03 Inspection Program have not been revised from the requirements of Bulletin 80-13. If cracks are discovered during the examinations, they will be identified to the USNRC Resident inspector within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of their confirmation. All evaluations and repairs will be submitted to the USNRC for approval prior to restart.
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4 SUNSAARY implementation of the upgraded Augmented Inspection Program 3 (AUG-03), during the 3R11 refueling outage, is considered an enhancement to the overall inspection program, as previously implemented.
Since superior visual examinations will be performed on all applicable accessible weld locations of the Core Spray annulus piping, visible cracking in the welds and heat affected zones will be identified and evaluated for acceptability. Additionally, the previously installed downcomer clamps and header tee box brackets will be inspected.
j The completion of the 3R11 examinations will assure the integrity of the annulus piping
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@rtion of the Core Spray System which is essential to delivering low pressure coolant Into the shroud following a design basis Loss of Coolant Accident.
The more refined examination technique to be used for the annulus region piping will
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enhance the ability to identify piping degradation. For the sparger portions of the Core i
Spray internals, the examinations performed during 3R1D included the recommended scope, and actually exceeded the recommended examination techniques. Acceptable results from previous inspections, and an acceptable baseline inspection using the BWRVIP criteria during outage 3R10, serve as the basis for implementing the reinspection criteria of BWRVIP-18. The updated Augmented Inspection Program for Core Spray Internals will provide an acceptable level of assurance that the integrity and performance of the Core Spray System will meet its design requirements.
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