ML18065B205
| ML18065B205 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 03/26/1998 |
| From: | Haskell N CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-97-06, GL-97-6, NUDOCS 9804090001 | |
| Download: ML18065B205 (11) | |
Text
A CMS Energy Company Palisades Nuclear Plant Tel: 616 764 2276 27780 Blue Star Memorial Highway Fax: 616 764 2490 March 26, 1998 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Covert, Mt 49043 DOCKET 50-255 - LICENSE DPR PALISADES PLANT Nathan L. Haskell Director, Licensing 90-DAY RESPONSE TO GENERIC LETTER 97-06, "DEGRADATION OF STEAM GENERATOR INTERNALS" Generic Letter (Gq 97-06, "Degradation of Steam Generator Internals," issued December 30, 1997, requests that licensees provide information on programs in place or planned to detect degradation of steam generator internals. The enclosure to this letter provides the requested information.
SUMMARY
OF COMMITMENTS This letter contains n~ new commitments and no revisions to existing commitments.
CC Administrator, Region Ill, USNRC Project Manager, NRR, USNRC NRC Resident Inspector - Palisades Enclosure 9804090001 980326. }
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CONSUMERS ENERGY COMPANY To the best of my knowledge, the contents of this response providing requested information per Generic Letter 97-06, are truthful and complete.
By iJ.
Sworn and subscribed to before me this o?6 - day of >>;?Ob.Ck 1998
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Alora M. Davis, Notary Public Berrien County, Michigan (Acting in Van Buren County, Michigan)
My commission expires August 26, 1999
[SEAL]
ENCLOSURE CONSUMERS ENERGY COMPANY PALISADES PLANT DOCKET 50-255 90-DA Y RESPONSE TO GENERIC LETTER 97-06 "DEGRADATION OF STEAM GENERA TOR INTERNALS" 8 Pages
90-DA Y RESPONSE TO GENERIC LETTER 97-06 "DEGRADATION OF STEAM GENERA TOR INTERNALS" INTR.ODUCTION Generic Letter (GL) 97-06, "Degradation Of Steam Generator Internals," was issued on December 30, 1997, to "(1) again alert addressees to the previously communicated findings of damage to steam generator internals, namely, tube support plates and tube bundle wrappers, at foreign PWR facilities; (2) alert addressees to recent findings of damage to steam generator tube support plates at a United States PWR facility; (3) emphasize to addressees the importance of performing comprehensive examinations of steam generator internals to ensure steam generator tube structural integrity is maintained in accordance with the requirements of Appendix B to 10 CFR Part 50; (4) require all addressees to submit information that will enable the NRG staff to verify whether addressees' steam generator internals comply with and conform to current licensing bases for their respective facilities."
The information related to steam generator internals was requested by the NRC to be submitted within 90 days of the date of the generic letter. The following provides the information requested by GL 97-06 for Palisades:
NRC REQUESTED INFORMATION. ITEM 1 (1)
Discussion of any program in place to detect degradation of steam generator internals and a description of the inspection plans, including the inspection scope, frequency, methods, and equipment.
The discussion should include the following information:
(a)
Whether inspection records at the facility have been reviewed for indications of tube support plate signal anomalies from eddy current testing of the steam generator tubes that may be indicative of support plate damage or ligament cracking. If the addressee has performed such a review, include a discussion of the findings.
(b)
Whether visual or video camera inspections on the secondary side of the steam generators have been performed at the facility to gain information on the condition of steam generator internals (e.g., support plates, tube bundle wrappers, or other components). If the addressee has performed such inspections, include a discussion of the findings.
(c)
Whether degradation of steam generator internals has been detected at the facility, and how the degradation was assessed and dispositioned.
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90-DAY RESPONSE TO GENERIC LETTER 97-06 "DEGRADATION OF STEAM GENERA TOR INTERNALS" CONSUMERS ENERGY COMPANY RESPONSE. ITEM 1 Following are the Consumers Energy responses to Items 1 (a) through 1 (c). In addition, an attachment describes additional improvements planned for our steam generator inspection program.
Response to Item 1 (a)
During bobbin coil eddy current testing (ECT) of the steam generator tubes, the tubes are examined at the support plate locations for distortions or non-quantifiable indications. If found, anomalies are reported, reviewed, and dispositioned by the Nondestructive Examination (NOE) Analysts. Any indications tha~ may suggest a damaged tube support plate are to be examined further by other methods. ECT of the steam generator tubes and visual inspection of the steam generator internals have not indicated any degradation of the stainless steel eggcrate tube support plates. Therefore, no further review of eddy current data to identify and evaluate tube support plate damage has been performed or considered necessary at Palisades.
Response to Item 1 (b)
Visual/video inspections of Palisades steam generators' secondary side have been completed during each of the refueling outages in 1992, 1993, 1995, and 1996 since replacement of the steam generators in 1990. Inspections during each refueling outage were documented and video taped. Areas of inspection included the upper steam drum area, steam dryers, moisture separators, recirculation and feedwater distribution piping, and upper bundle tube support plates. Each refueling outage inspection also included a video inspection within the tube bundles and a foreign object search and retrieval (FOSAR). These inspections are covered under Palisades Nuclear Plant steam generator inspection procedures:
- 1)
SSS-2.4.2-CPAL-2 Secondary Side Steam Generator Inspection
- 2)
SSS-2.4.2-CPAL-3 Steam Generator Upper Bundle Support Plate Inspection
- 3)
SSS-2.4.2-CPAL Remote Examination and Removal of Foreign Objects from Steam Generator Secondary Side Visual inspections have noted no flow assisted corrosion (FAC) or other damage mechanisms on the secondary side. Steam generator secondary side inspections have also verified that no support plate damage or ligament cracking is occurring. In addition to these inspections, Palisades has performed cleaning (sludge lancing) on the top of the tubesheet in each steam generator during each refueling outage.
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0 90-DA Y RESPONSE TO GENERIC LETTER 97-06 "DEGRADATION OF STEAM GENERA TOR INTERNALS" A discussion of the visual and video inspection activities and the findings for each steam generator secondary side inspection follows:
Preservice Inspection The current Palisades steam generators are replacement steam generators and were installed in the fall of 1990. The preservice inspection indicated there were no active degradation mechanisms present within the steam generators prior to service.
1992 Refueling Outage A FOSAR video inspection was performed after tube sheet cleaning of both Steam Generators E-50A and E-508. Seven objects were observed in Steam Generator E-50A. These objects included one wire and six pieces of scale, which were removed. One object was observed and removed in Steam Generator E-508. _The tubes displayed no external. wear due to foreign objects. The tubes also showed no signs of scale build-up.
1993 Refueling Outage A FOSAR video inspection was performed after tube sheet cleaning of both Steam Generators E-50A and E-508. Two pieces of wire were identified and removed from Steam Generator E-50A. One piece of wire was removed from Steam Generator E-508. In addition, fine pieces of wire were also removed by sludge lancing in both steam generators. This wire was identified as wire from the moisture separator baskets. The tubes displayed no external wear due to foreign objects. The tubes also showed no signs of scale build-up.
1995 Refueling Outage A FOSAR video inspection was performed after tube sheet cleaning of both Steam Generators E-50A and E-508. Small particles were removed from Steam Generator E-50A. Nothing was found in Steam Generator E-508. An upper bundle inspection was also performed on Steam Generator E-50A to observe the condition of the upper secondary side. There was no sludge or other type of deposits found in *the upper secondary side.
1996 Refueling Outage Areas of inspection included the upper steam drum area, steam dryers, moisture separators, recirculation and feedwater distribution piping, and upper bundle tube support plates. The refueling outage inspection also included a video inspection within the tube bundles and a foreign object search and retrieval (FOSAR).
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90-DA Y RESPONSE TO GENERIC LETTER 97-06 "DEGRADATION OF STEAM GENERA TOR INTERNALS" The FOSAR inspection found small metal slag particles and a gasket segment in Steam Generator E-50A. The FOSAR inspection found sludge rock and a bundle of wire bristles in Steam Generator E-508. All objects were removed from both steam generators. Post sludge lancing inspection of both steam generators showed the tube sheet annulus and tube lanes to be clean of sludge. Video inspections showed the secondary side of both steam generators to be clean and free from wear with no signs of degradation.
Response to Item 1 (c)
To date, no degradation has been found on the secondary side of Palisades' steam generators. Palisades' steam generators have stainless steel eggcrate supports, which are less susceptible to corrosion or FAC than carbon steel. This observation was reported in the Combustion Engineering Owners Group (CEOG) Report CE NPSD-1092, "Evaluation of Degraded Secondary Internals Operability Assessment."
NRC REQUESTED INFORMATION. ITEMS 2 (2)
If the addressee currently has no program in place to detect degradation of steam generator internals, include a discussion and justification of the plans and schedule for establishing such a program, or why no program is needed.
CONSUMERS ENERGY COMPANY RESPONSE. ITEM 2 Palisades currently has a program in place to detect degradation of steam generator internals. Therefore, Item 2 is not applicable to Palisades.
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ATTACHMENT CONSUMERS ENERGY COMPANY PALISADES PLANT DOCKET 50-255 90-DA Y RESPONSE TO GENERIC LETTER 97-06 "DEGRADATION OF STEAM GENERA TOR INTERNALS" PLANNED IMPROVEMENTS TO PALISADES' STEAM GENERA TOR INSPECTION PROGRAM 3 Pages
PLANNED IMPROVEMENTS TO PALISADES' STEAM GENERA TOR INSPECTION PROGRAM Significant industry-wide initiatives have been undertaken with related. actions to be included in the Palisades steam generator secondary inspection plan. A detailed discussion follows:
In response to the issuance of the proposed GL on degradation of steam generator internals, the Nuclear Electric Institute (NEI) formed the Steam Generator Internals Task Force in January, 1997. The purpose of the task force was to develop a coordinated industry wide response to the secondary side degradation issues identified in the proposed GL. Participation on the task force included the Electric Power Research Institute (EPRI), licensees, and representatives of the vendors and owners groups for each domestic steam generator design. The task force developed an action plan to assess potential steam generator tube degradation throughout the industry.
In response to the NEI Steam Generator Internals Task Force Plan, Combustion Engineering (CE) initiated a program to assist CE owners in assessing the susceptibility of tube damage and loss of decay heat removal capability in their steam generators due to secondary side degradation. An integral component in this assessment was an appreciation of the applicability of the degradation found in the French units to domestic steam generators. Together, EPRI and Electricite de France (EdF) developed report GC-109558, "Steam Generator Internals Degradation: Modes of Degradation Detected in EdF Units," to address the applicability issue.
The EPRI report.GC-109558 provides evaluations of the causal factors involved in the modes of degradation experienced in the French units. CE used this report to gain insights into the applicability of the French experience to their steam generator designs and operating history. NEI transmitted this report to the NRC on December 19, 1997.
In addition to the review of the EdF degradation casual factors, ttie CE susceptibility assessments included consideration of:
design factors fabrication and manufacturing techniques plant operating history (including chemistry) plant inspection experience, and related degradation, such as denting.
As part of the inspection experience review, the CEOG compiled and assessed collective visual, video and pertinent NOE inspection experience information to further enhance their evaluations regarding the susceptibility to internals degradation.
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PLANNED IMPROVEMENTS TO PALISADES' STEAM GENERA TOR INSPECTION PROGRAM In May, 1997, the NEI task force met with the NRG to gain a better understanding of the safety concerns discussed in GL 97-06. As a result of these efforts, the GEOG developed reports for operational assessment, susceptibility and bounding safety analysis. These reports provide reasonable assurance that degradation of internals has not compromised steam generator tube integrity or decay heat removal capability.
The GEOG has reviewed EPRI GC-109558 relative to the design of CE steam generators, and has determined that there is no susceptibility to the specific causes of degradation experienced in the French units. Analysis of a CE design unit with observed eggcrate degradation indicates a potential susceptibility to FAC of tube supports. The CEOG evaluation, in the CEOG Report CE NPSD-1103, provides assurance that FAC is the only steam generator internals components damage mechanism of potential safety significance for steam generators with stainless steel eggcrate tube supports. However, stainless steel eggcrate tube supports have a very low susceptibility to FAC.
In summary, a comprehensive review of CE designed steam generator internals degradation experience has been conducted. In addition, Consumers Energy participates in the CEOG Steam Generator Task Force, which took part in the NEI sponsored Owners Group reviews of industry wide experience. Based on these reviews, it is concluded that existing or potential degradation mechanisms to steam generator secondary side internals do not pose a safety concern. This conclusion is documented in the following reports:
- 1.
CEOG Report CE NPSD-1092, "Evaluation of Degraded Secondary Internals Operability Assessment"
- 2.
CEOG Report CE NPSD-1103, "Evaluation of Susceptibility of Internals Degradation in CE Designed Steam Generators"
- 3.
CEOG Report CE NPSD-1104, "Evaluation of Degraded Secondary Internals Bounding Safety Analysis" Palisades Response to NEI 97-06 Initiative Palisades is developing a Steam Generator Program using the NEI 97-06, "Steam Generator Program Guidelines" as a model. The Palisades Steam Generator Program will be a site Engineering Manual procedure entitled, "Steam Generator 2
PLANNED IMPROVEMENTS TO PALISADES' STEAM GENERA TOR INSPECTION PROGRAM Program." One section of the procedure will cover Foreign Material Exclusion. A second section will cover Maintenance of Steam Generator Secondary Side and will address the following:
Degradation of Steam Generator Internals Secondary Side Visual Inspection, Including:
Steam Drum Inspection Steam Generator Upper Bundle Support Plate Inspection Sludge Lance Cleaning and Bundle Flushing FOSAR Main Condenser Eddy Current Inspection Condenser Water and Air lnleakage Detection and Location A third section of the procedure will include a steam generator operational assessment, to be performed before each refueling outage. This assessment will determine the frequency. and scope of the secondary side inspection. This operational assessment also references the steam generator degradation assessment and condition monitoring assessment completed at the end of each steam generator inservice inspection.
Our plans call for the revised Palisades Steam Generator Program, modeled after NEI 97-06, to be in place by the start of the first refueling outage after January 1, 1999.
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