ML20197H970
| ML20197H970 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 12/10/1998 |
| From: | Cruse C BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9812140221 | |
| Download: ML20197H970 (10) | |
Text
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l CH ARLES II. CCtJbE Baltimore Gas and Electric Company Vice President Calvert Cliffs Nuclear Power Plant
- Nuclear Energy 1650 Calven Cliffs Parkway Lusby, Maryland 20657 410 495-4455 December 10,1998 U. S. Nuclear Regulatory Commission Washington,DC 20555 ATTENTION: Document Control Desk
SUBJECT:
Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50-317 & 50-318 Response to Clarification Regarding NRC Question No. 4.1.17; Integrated Plant Assessment Reoort: License Renewal Anolication
REFERENCES:
(a) Letter from Mr. C. IL Cruse (BGE) to NRC Document Control Desk, dated April 8,1998," Application for License Renewal" (b) Letter from Mr. D. L. Solorio (NRC) to Mr. C. H. Cruse (BGE), dated September 3,1998," Request for Additional Information for the Review of the Calvert Cliffs Nuclear Power Plant, Units 1 & 2, Integrated Plant Assessment for the Reactor Coolant System" (c) Letter from Mr. D. L. Solorio (NRC) to Mr. C. H. Cruse (BGE), dated November 18,1998, " Clarification of NRC Requests for Additional Information on Calvert Cliffs Nuclear Power Plant License Renewal Application Submitted by the Baltimore Gas and Electric Company" Reference (a) forwarded the Baltimore Gas and Electric Company (BGE) license renewal application (LRA). Reference (b) forwarded questions from NRC staff on Section 4.1 of the BGE LRA, Reactor Coolant System. Reference (c) reported efforts between NRC staff and BGE to clarify certain questions, and provided clarified question number 4.1.17. Attachment (1) provides BGE's response to Reference (c).
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l Document Control Desk i December 10,1998 Page 2 i
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- Should you have further questions regarding this matter, we will be pleased to discuss them with you.
Very truly yours, i
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/;pjWW i i l STATE OF MARYLAND :
- TO WIT:
COUNTY OF CALVERT :
I, Charles H. Cruse, being duly sworn, state that I am Vice President, Nuclear Energy Division, Baltimore Gas and Electric Company (BGE), and that I am duly authorized to execute and file this l response on behalf of BGE. To the best of my knowledge and belief, the statements contained in this l document are true and correct. To the extent that these statements are not based on my personal knowledge, they are based upon information provided by other BGE employees and/or consultants. Such !
information has been reviewed in accordance with company practice and I believe it to be reliable. .
AulW ~.-
l Subgribed and sworn before me, a Notary ublic in and for the State of Maryland and County of (Vlun,f .this /0Mdayof .cm la d.1998.
WITNESS my Hand and Notarial Seal: M C- il Notary Public My Commission Expires: dA4 /,AddM O b dte '
CHC/KRE/dtm
Attachment:
(1) Response to Clarification Regarding NRC Question No. 4.1.17 on Calvert Clifts ,
Nuclear Power Plant License Renewal Application ec: R. S. Fleishman, Esquire C. I. Grimes, NRC J. E. Silberg, Esquire D. L. Solorio, NRC ,
i S. S. Bajwa, NRC Resident Inspector,NRC A. W. Dromerick, NRC R. I. McLean, DNR H. J. Miller, NRC J. H. Walter, PSC l
ATTACHMENT (1) 4 l
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J RESPONSE TO CLARIFICATION REGARDLNG NRC QUESTION NO. 4.1.17 ON CALVERT CLIFFS NUCLEAR POWER PLANT 4 i l
l Baltimore Gas and Electric Company Calvert Cliffs Nuclear Power Plant Decemher 10,1998
1 ATTACHMENT (1)
RESPONSE TO CLARIFICATION REGARDING NRC QUESTION No. 4.1.17 ON CALVERT CLIFFS NUCLEAR POWER PLANT LICENSE RENEWAL APPLICATION Revised Ouestion No. 4.1.17 STP-M-574-1/2 Procram P xause industry experience to date indicates that eddy current (ET) inspection of steam generator (SG) tubes is not enough to manage aging effects before there is a loss of intended function, the staff also relies on licensee primary and secondary side chemistry control programs to mitigate corrosion, as well as, Technical Specification limits for SG leakage to detect aging effects. Based on the staff's review of Section 4.1 of Baltimore Gas and Electric Company's (BGE's) license renewal application (LRA), it appears that BGE relies solely upon ET testing to manage degradation of SG tubes before there is a loss ofintended function. The information provided in the LRA for the manageme.nt of SG tube degradation does not appear to meet template requirements. Please clarify your explanation of the aging management programs for SG tubes. Also, describe the implementation of ET procedures in more detail.
MN-3-110 Procram The LRA cites the subject program to manage erosion corrosion of various SG components such as the main steam outlet nozzles. Confirm that the inspection frequency of the various components is on a refueling basis. If the frequency is longer, provide the specific inspection frequency and the basis for the inspection frequency for the following components: main steam outlet nozzles, secondary manway, handhole, and associated cover plates.
Provide relevant operating experience to demonstrate the effectiveness of the program in managing erosion corrosion of the following components: main steam outlet nozzles, secondary manway, handhole, and associated cover plates.
SG-20 Procram The licensee cites the subject n ogram to manage general corrosion of the SG primary manway cover.
Provide the acceptance criteria for the subject procedure. Provide relevant operating experience to demonstrate the effectiveness of the program in managir g general corrosion of the manway cover.
FASTENER-01 Program He licensee cites the subject program to manage stress corosion cracking (SCC) of the SG primary manway studs. Staff experience 4, SCC indicates that visual inspection may not be adequate to detect SCC because of the size and nature and location of such cracks. Provide the basis for concluding visual inspection of the studs is sufficient to detect SCC before there is a loss ofintended function.
Provide the acceptance criteria for the subject procedure. Provide relevant operating experience to demonstrate the effectiveness of the program in managing SCC of the SG primary manway studs.
Allov 600 Procram Confirm weld metals 182/82 are implicitly included within the scope of the Alloy 600 program.
BGE Resnonan Because the response for the Surveillance Test Procedure (STP)-M-574-1/2 program is very lengthy, it is provided last.
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J XITACHMENT (1)
RESPONSE TO CLARIFICATION REGARDING NRC QUESTION NO. 4.1.17 ON CALVERT CLIFFS NUCLEAR POWER PLANT LICENSE RENEWAL APPLICATION '
MN-3-110 Baltimore Gas and Electric Company performs an examination of the SG main outlet nozzles welds in accordance with American Society of Mechanical Engineers (ASME) Section XL Three of the four SG main steam nozzle to reducer welds have been examined during the current inservice ;
inspection interval. The welds were examined using ultrasonics and magnetic particle methods. The only indications noted were caused by the ID root geometry of the weld.
- S/G 11 Examined - 1996 ,
- S/G 12 Examined - 1996
- S/G 21 Examined - 1995 These items were scheduled and examined in accordance with ASME Section XI.
Baltimore Gas and Electric Comp.ny has determined that the erosion / erosion corrosion of the SG secondary manway, manway cover plate, and handhole cover plate are not aging issues, but rather an operational concern. Any da.rnage to these SG components found during refueling outages would be repaired before the unit (s) would be brought back to power. Discussion concerning the SG secondary manway, manway cover plate, and handhole cover plate listed on page 4.1-26 of Section 4.1.2 (Group 3 - Materials and Environment) should be disregarded since erosion / erosion corrosion is not an aging issue for these components.
SG-20 The procedure SG-20, " Primary Manway Removal and Installation," is not credited in Section 4.1.2 of the LRA for general corrosion of the SG primary manway cover plate. On page 4.1-36 of LRA Section 4.1.2 (Group 5), the procedure (SG-20) is credited with the discovery of general corrosion on the SG primary manway bolting materials, not the SG primary manway cover plate. The procedures ;
credited for discovering general corrosion on the SG primary manway cover plates are MN-3-110, ;
"lSI of ASME Section XI Components," and MN-3-301," Boric Acid Corrosion Inspection Program," l as described on page 4.1-22 of LRA Section 4.1.2. These programs use visual examinations (VT-2 (a !
type of visual examination described in ASME XI, IWA-2212]) to discover general corrosion. The ,
acceptance criteria (general corrosion) for MN-3-301 is the presence of boric acid leakage (e.g., boric j acid crystals) around the SG primary manway cover plate, and for MN-3-110 the acceptance criteria i is the presence of corrosion on the SG primary manway cover plate. Full descriptions of these two programs are provided in LRA Section 4.1.2 Group 2 on pages 4.1-21 through 4.1-23, including operating experience.
EASTENER-01 Baltimore Gas and Electric Company has reconsidered this aging scenario and concluded that, although FASTENER-01 provides generic guidance to inspectors, it would be more appropriate to credit SG-20 (in modified form). Procedure SG-20 provides a more direct and focused approach in this area for managing the effects of SCC on the SG primary manway studs. The modified SG-20 will include direction that if leakage has occurred at the joint, additional NDE is required, and the NDE will include an examination for SCC of the studs. The NDE techniques will not rely on strictly visual techniques, but on other examination methods (e.g., surface techniques) deemed appropriate.
Based on the examinations, the SG primary manway studs and nuts are accepted for reuse or new ones are installed. Operational experience with this procedure has resulted in some new replacement 2
ATTACHMENT (1)
. RESPONSE TO CLARIFICATION REGARDING NRC QUESTION NO. 4.1.17 ON CALVERT CLIFFS NUCLEAR POWER PLANT LICENSE RENEWAL APPLICATION studs being installed in the SG primary manway due to damage in the removal / installation process.
References to FASTENER-01 should be replaced with SG-20 (modified) on page 4.1-48 under Aging !
Mrogement Programs, on page 4.149 under Demonstration of Aging Management, and on page 4.1-54 under Table 4.1-4.
Alloy 600 Prtwram Baltimore Gas and Electric Company has confirmed that the weld materials 182/82 are explicitly included within the scope of the Alloy 600 Program.
STP-M-574-1/2 In response to this request for additional information, BGE has elected to supplement Section 4.1 of I the LRA with additional programs to manage aging of the SG tubes, and to provide more detail for the ET program (STP-M-574-1/2, " Eddy Current Examination of CCNPP 1/2 SGs"). The CCNPP SGs are currently scheduled to be replaced in 2002 (Unit 1) and 2003 (Unit 2). The new SGs will be j managed by the same programs credited for the existing CCNPP SGr. The new programs credited for managing aging of the SG heat exchanger (HX) tubes are:
Calvert Cliffs Chemistry Procedure CP-217, " Specifications and Surveillance: Secondary l Chemistry," is credited with mitigating the effects of SG HX tube (secondary side) denting (Group 1 of Section 4.1.2), pitting (Group 5 of Section 4.1.2), and SCC /intergranular stress corrosion cracking (IGSCC) (Group 7 of Section 4.1.2). Chemistry Procedure CP-217 is described in Section 5.9.2 of the BGE LRA under Group 1.
- Calvert Cliffs Chemistry Procedure CP-204, " Specification and Surveillance Primary Systems," is credited with mitigating the effects of SCC /lGSCC/ primary water stress '
corrosion cmcking (PWSCC)(Group 7 of Section 4.1.2) on the SG HX tubes (primary side).
Chemistry procedure CP-204 is described in Section 4.1.2 of the BGE LRA under Group 6.
In addition to these programs, BGE has also expanded the discussion of STP-574-1/2, which is credited for discoveri,.g denting (Group 1 of Section 4.1.2), pitting (Group 5 of Section 4.1.2) and SCC /IGSCC/PWSCC (Group 7 of Section 4.1.2) of SG HX tubes. Additional references have also been included for this expanded discussion of the CCNPP SG HX ET Program. i Details of CCNPP SG HX ET Program Calvert Cliffs has been proactive in implementing the latest technologies and industry standards in managing aging effects on the CCNPP SGs. The primary purpose of SG aging management is to ensure tube integrity. The programs for managing aging contain a balance of prevention, inspection, evaluation, and repair. Both mitigation and discovery programs are credited with managing aging of the SG components to maintain tube integrity. The CCNPP Steam Generator Management Plan outlines the responsibilities and aging issues in order to meet the goal of SG tube integrity. Central to meeting this goal are proper chemistry control, inservice inspection, and any necessary SG tube repairs. Baltimore Gas and Electric Company is currently using the elements of NEl 97-06," Steam Generator Program Guidelines," in our programmatic approach to SG tube integrity.
Chemistry controls are based on Technical Specifications and BGE's interpretation of industry standards and recommendations made by Combustion Engineering. The foundation of secondary chemistry control is the latest revision of Electric Power Research Institute's (EPRI's) "PWR 3
ATTACIIMENT (1)
RESPONSE TO CLARIFICATION REGARDING NRC QUESTION NO. 4.1.17 ON CALVERT CLIFFS NUCLEAR POWER PLANT LICENSE RENEWAL APPLICATION 4
Secondary Water Chemistry Guidelines," as these guidelines represent the current industry best practices. Controls are formalized to ensure that chemical and radiochemical excursions are responded to with appropriate corrective actions. Remedial actions .re also specified to minimize corrosion degradation. [ Reference 1]
Concentrations of aggressive impurities in the CCNPP SGs are maintained at very low levels, typically at less than one-tenth of the EPRI Guideline Action Level Limit. A wide range of pH and chemical injection strategies and full-flow condensate filtration are employed to limit the transport of corrosion products to the SGs. A high-hydrazine feed regime is used to keep a " chemically reducing environment" in the SGs to reduce the rate of intergranular attack / SCC. Tight limits are placed on bulk chemicals and ion exchange resins to restrict potential contaminant source terms. [ Reference 1]
A set of SG lay-up guidelines have been developed to help plan outages for maintaining proper chemistry. The guidelines include how to feed and bleed the generator, plant equipment needed, chemical contaminant control strategies, and alternatives. [ Reference 1]
Calvert Cliffs is using the elements of EPRI PWR Steam Generator Examination Guidelines (Reference 2) in its response to NRC Generic Letter 95-03, "Circumferential Cracking of Steam Generator Tubes," and is also following NEl 97-06. Some of the important features of NEl 97-06 include: [ Reference 3, Section 3.2]
e Sampling using a prescriptive or performance-based approach; e Obtaining information necessary to develop degradation assessments; and e Qualifying the inspection program by determining accuracy and defining the elements for enhancing system performance.
The inspection program endorses using the best available ET techniques to examine areas in the SGs that are most susceptible to degradation. Specialized examinations are conducted with rotating ET probes to provide more detailcd information necessary to assess the condition of the SGs, and to evaluate the effectiveness of SU management programs. The selection of areas to be inspected is based both on Calvert Cliffs and industry operating experience. [ Reference 1]
An effective ET inspection program is essential to understanding and managing SG degradation mechanisms. Corrective and preventive measures to manage specific degradation mechanisms are established based in part on the ET data. [ Reference 1]
Written guidance for ET analysis comes from the CCNPP SG ET Analysis Guidelines. The key elements of these guidelines include: [ Reference 4]
- Assessment of degradation mechanisms; e Personnel qualifications;
- Procedural qualifications;
- Acquisition and data analysis;
- Probe selection; e Indication report requirements; and 4
1 ATTACHMENT (1) l RESPONSE TO CLARIFICATION REGARDING NRC QUESTION NO. 4.1.17 ON CALVERT CLIFFS NUCLEAR POWER PLANT LICENSE RENEWAL APPLICATION
- Analysis protocol.
Periodic visual inspections of the secondary side of the generators are also conducted. Visual I inspections of egg crates and tube support plates are periodically performed to look for signs of i erosion and tube bundle fouling. [ Reference 1] '
l Vendors are typically used to perform the tasks of acquiring and analyzing SG ET data at CCNPP.
]
The requirements for personnel qualifications are currently delineated in CCNPP procedure MN-3-105, " Qualification of NDE Personnel and Procedures." This procedure requires that '
personnel analyzing SG ET data be certified in accordance with the most recent version Reference (2), Appendix G (Qualified Data Analyst training / qualification). Additionally, all personnel acquiring and/or analyzing SG ET data are required te be certified to a vendor procedure
{
that meets or exceeds the requirements of American Society for Non-Destructive Testing !
SNT-TC-1 A. [ Reference 4, Section V]
All analysts are required to take and pass a CCNPP site-specific performance demonstration. The l purpose of this exam is to familiarize analysts with the ET signals associated with active or potential degradation mechanisms at CCNPP. He site-specific performance demonstration is implemented per Section 6.6 of Reference (2). [ Reference 4, Section V]
The following discovery program implements the goals of the CCNPP SG Management Plan, CCNPP SG ET Analysis Guidelines and EN-4-106, " Steam Generator Tube Surveillance Program," which l incorporates the latest industry guidance. Aging management of the CCNPP SGs not only monitors past performance of the SG HX tubes, but also ensures that the tubes will perform their intended function until the next scheduled inspection.
The CCNPP Surveillance Test Procedures STP-M-574-1/2 are credited for discovering denting, pitting and SCC /IGSCC/PWSCC of SG HX tubes. The procedure directs the user as to the sample size for tube inspection, inspection process, evaluation, and determination of tube status. The evaluation of SG HX tubes is accomplished with this procedure, EPRI/ industry guidelines, and CCNPP Technical Specifications. Specialized examinations are conducted with rotating ET probes to provide more detailed information necessary to assess the condition of the SGs and to evaluate the effectiveness of SG management programs. [ Reference 1] The current examination involves 100%
full length bobbin coil of all inspected SG tubes during each refueling outage. Currently, a plus point probe is used to examine the hot leg top of tube sheet (100% inspection), steam blanket area (100%
inspection), dented support intersections, tight U-bends, cold leg top of tube sheet, arc and stay dome, and rolled plugs. A visual inspection (100%) is also performed for tube plugs as well as a sludge pile mapping. Remote video equipment is also used to examine the interior SG structural components.
[ Reference 5]
l Calvert Cliffs Surveillance Test Procedures STP-M-574-1/2 selects the number of tubes to be ;
examined according to current CCNPP Technical Specifications and EPRI SG guidelines. The CCNPP SG sampling size far exceeds the requirements in Technical Specifications.
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ATTACHMENT (1)
RESPONSE TO CLARIFICATION REGARDING NRC QUESTION NO. 4.1.17 ON CALVERT CLIFFS NUCLEAR POWER PLANT LICENSE RENEWAL APPLICATION The SG HX tubes are ranked in categories of degradation according to the CCNPP Technical Specifications. The Technical Specifications currently have three categories for inspection results
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based on the percentage of tubes that are classified as degraded and defective. The ET acceptance criteria for SG HX tubes are:
ImperfecSon - means an exception to the dimensions, finish, or contour of a tube from that required by Ebrication drawings or specifications. Eddy-current testing indications below 20% of the %dnal wall thickness, if detectable, may be considered as imperfections.
- Degraded tube - means a tube containing imperfections 2 20% of the nominal wall thickness caused by degradation.
Defect - means an imperfection of such severity that it exceeds the plugging or repair limit.
A tube containing a defect is defective. Any tube that does not permit the passage of the ET I inspection probe shall be deemed a defective tube. Any tube with a crack is a defect. l e l Plugging or repair limit - means the imperfection depth at or beyond which the tube shall be '
removed from service by plugging, or repaired by sleeving in the affected area because it may become unserviceable prior to the next inspection. The plugging or repair limit imperfection depths are specified as 40% of original nominal tube wall thickness or 40% of Westinghouse laser-welded sleeve wall thickness. For the ABB-Combustion Engineering tungsten-inert-gas-welded sleeves the limit is 28%.
The surveillance procedures, STP-M-574-1/2, also determine if additional tube examinations are required in accordance with Technical Specifications or Reference (2). [ References 6 and 7, Section 6.6) Results of the examinations are then documented on attachments to the procedure.
An issue Report is submitted to plug or sleeve SG HX tubes that are considered susceptible to failure before the next inspection. The inspection frequency for SG HX tubes is determined by the CCNPP Technical Specifications. [ References 6 and 7] For purposes of SG tubing, " susceptible to failure" means active degradation has been identified through inspection and the tube is susceptible to not satisfying structural integrity li nits prior to the next refueling outage (or next inspection).
As a result of these SG HX tube examinations, tubes have to be plugged or repaired. The number of tubes that have been plugged at CCNPP to date are: SG No. I1 - 604 tubes; SG No.12 - 776 tubes; SG No. 21 - 704 tubes; SG No. 22 - 443 tubes. [ Reference 4,Section III, Table D, Reference 8]
Some tubes were pulled to confirm degradation mechanisms. In 1983, two tubes were pulled and in j 1986, six tubes were pulled from the Unit 1 SG No. I1. The results showed indications of wear and l
SCC /lGSCC. In 1995 three tubes were pulled from the Unit 2 SG No. 22, which also showed signs of SCC /IGSCC; in 1996, three tubes were pulled from the Unit 1 SG No.12 with similar defects. 1
[ Reference 4, Section 111 E) i The Units 1 and 2 SG tubes are inspected during each unit's refueling outage. Inspections are based j on EPRI guidance, applicable industry experience, Technical Specifications and site-specific SG degradation characteristics. Consistent with this, BGE is currently an active participant on committees sponsored by EPRI, Combustion Engineering Owners Group, and the Nuclear Energy Institute focusing on preservation of SG structural integrity.
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ATTACIIMENT (1)
RESPONSE TO CLARIFICATION REGARDING NRC QUESTION NO. 4.1.17 ON CALVERT CLIFFS NUCLEAR POWER PLANT LICENSE RENEWAL APPLICATION References-
- 1. CCNPP Steam Generator Management Plan, October 1998
- 2. EPRI's PWR Steam Generator Examinstion Guidelines, Revision 5, September 1997
- 3. Nuclear Energy Institute 97-06, Steam Generator Program Guidelines, December 1997
- 5. CCNPP 1998 Steam Generator Maintenance and Inspection Project Plan, Revision 0, August 25,1997
- 6. CCNPP Technical Procedure STP-M-574-1, " Eddy Current Exam of CCNPP Unit 1 SGs,"
Revision 7, January 22,1998
- 7. CCNPP Technical Procedure STP-M-574-2, " Eddy Current Exam of CCNPP Unit 2 SGs," ,
Revision 4, April 4,1995
- 8. Letter from Mr. P. E. Katz (BGE) to NRC Document Control Desk, dated May 26,1998,
" Report of Steam Generator Tube Plugging"(Unit 1) b 4
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