ML020280283
| ML020280283 | |
| Person / Time | |
|---|---|
| Site: | Three Mile Island  |
| Issue date: | 02/12/2002 |
| From: | Colburn T NRC/NRR/DLPM/LPD1 |
| To: | Kingsley O Exelon Generation Co, Exelon Nuclear |
| Colburn T, NRR/DLPM, 415-1402 | |
| References | |
| TAC MA9460 | |
| Download: ML020280283 (9) | |
Text
February 12, 2002 Mr. Oliver D. Kingsley, President and Chief Nuclear Officer Exelon Nuclear Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555
SUBJECT:
SAFETY EVALUATION OF PROCEDURES FOR PERFORMING AND EVALUATING THE REACTOR BUILDING TENDON SURVEILLANCE, THREE MILE ISLAND NUCLEAR STATION, UNIT 1 (TMI-1) (TAC NO. MA9460)
Dear Mr. Kingsley:
By letter dated February 25, 2000, in accordance with TMI-1 Technical Specification 4.4.2.1.6.a, you submitted Topical Report No. 136, Revision 00, 25th Year Reactor Building Tendon Surveillance (Period 7) for TMI-1. Attachment 3 of the report included the three-volume contractor report by Precision Surveillance Corporation entitled, 25TH Year Physical Surveillance of the Three Mile Island Unit 1 Containment Building, Post Tensioning Surveillance Report, which provided procedures used by the licensee to perform its 25th year tendon surveillance and the methods used in evaluating the surveillance results. During a conference call on March 7, 2001, the Nuclear Regulatory Commission (NRC) staff questioned the approach of normalizing forces to the individual as-found tendon lift-off forces when plotting vertical, hoop, and dome tendon forces versus time trend plots described in Attachment 1 to the above Topical Report. In response to the NRC staffs request, you provided Revision 01 of Topical Report No. 136 by letter dated September 17, 2001, in which the normalizing forces were removed.
The NRC staff has completed its review of Topical Report 136. Based on its review, the NRC staff finds that the procedures used for conducting the surveillance and the methods used in evaluating the results are in accordance with the NRC staffs recommendations in the safety evaluation dated August 28, 1997. Additionally, the report serves to provide the engineering evaluation report required by Title 10 of the Code of Federal Regulations, Section 50.55a, and paragraph IWL-3300 of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code,Section XI. The NRC staff concludes that the procedures and method of evaluations used for examination of concrete and the post-tensioning system are acceptable.
O. Kingsley Enclosed is our safety evaluation of the report. This action closes our review effort under TAC No. MA9460.
Sincerely,
/RA/
Timothy G. Colburn, Senior Project Manager, Section 1 Project Directorate I Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-289
Enclosure:
Safety Evaluation cc w/encl: See next page
O. Kingsley Enclosed is our safety evaluation of the report. This action closes our review effort under TAC No. MA9460.
Sincerely,
/RA/
Timothy G. Colburn, Senior Project Manager, Section 1 Project Directorate I Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-289
Enclosure:
Safety Evaluation cc w/encl: See next page DISTRIBUTION:
PUBLIC ACRS OGC JMunday PDI-1RF DTerao BPlatchek, RI MOBrien HAshar EAdensam TColburn Accession No. ML020280283 *No major changes made to SE.
OFFICE PDI-1\PM PDI-2\LA EMEB\SC PDI-1\(A)SC NAME TColburn MOBrien DTerao* JMunday DATE 2/7/02 2/8/02 SE dated 9/21/02 2/8/02 OFFICIAL RECORD COPY
SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO PROCEDURES FOR PERFORMING AND EVALUATING CONTAINMENT TENDON SURVEILLANCE AMERGEN ENERGY COMPANY, LLC THREE MILE ISLAND NUCLEAR STATION, UNIT 1 DOCKET NO. 50-289
1.0 INTRODUCTION
In Reference 1, dated August 28, 1997, the Nuclear Regulatory Commission (NRC) staff evaluated the licensees (then GPU Nuclear Corporation) 20th year reactor building (containment) tendon surveillance results for the Three Mile Island Nuclear Station, Unit 1 (TMI-1). In that safety evaluation (SE), the NRC staff observed that the loss of prestress in hoop tendons was more than predicted, and it might reduce the hoop tendon force below the minimum required force at about 25-years after the plants initial structural integrity test. In Reference 1, the NRC staff also recommended that the licensee modify its procedure for the tendon force regression analysis and future grease inspections.
By letters dated February 25, 2000, and September 17, 2001, the licensee (now AmerGen Energy Company, LLC) provided the results of its 25th year reactor building tendon surveillance in Topical Report No. 136 (TR 136), Revision 00 (Reference 2) in accordance with Section 4.4.2.1.6.a of the TMI-1 Technical Specifications. This SE reviews the content of the topical report, and assesses (1) the adequacy of the surveillance procedures being used for the containment concrete and post-tensioning system, and (2) the results of the surveillance in terms of the containment tendon system integrity.
2.0 EVALUATION The 25th year tendon surveillance and associated inspections (i.e., containment Inservice inspection (ISI)) were performed between August 27, 1999, and October 26, 1999. The licensee followed the requirements of the 1992 Edition and the 1992 Addenda of Subsection IWL of Section XI of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) in performing these inspections. Although the topical report is titled 25th Year Tendon Surveillance (Period 7), the licensee stated that it also serves as the Engineering Evaluation Report required by paragraph IWL-3300 of the ASME Code. Accordingly, this SE includes an evaluation of (1) the concrete examination, and (2) the post-tensioning tendon system examination.
2.1 Concrete Examination The licensee performed the concrete visual examinations in accordance with IWL-2510 of Subsection IWL, Requirements for Class CC Concrete Components of Light-Water Cooled Plants, in conjunction with alternatives authorized pursuant to Title 10 of the Code of Federal Regulations (10 CFR), Section 50.55a(a)(3). Because Subsection IWL does not provide explicit acceptance criteria for concrete examinations, the licensee established its acceptance criteria based on Section 5.1 of ACI 349.3R-96. The licensee identified five areas where Tier 1 acceptance criteria of ACI 349-3R were not met. The licensee performed the engineering evaluations of these areas and determined that no immediate repairs were required. However, it will be monitoring these areas during subsequent inspections. The licensee identified three additional areas of grease leakage or grease stains. The licensee determined that these grease leakages and stains will not adversely impact the containment concrete. However, the licensee states, the Mechanical/Structural Engineer shall perform continued monitoring of the grease leakage as part of its Repetitive Preventive Maintenance Task No. 9641.
Based on this description, the NRC staff finds that the licensees procedures for examination of concrete of the TMI-1 Reactor Building are in accordance with the requirements of Subsection IWL of the ASME Code as modified by 10 CFR 50.55a(b)(2)(ix).
2.2 Post-Tensioning System The post-tensioning system examination is evaluated in three areas: (1) examination of post-tensioning tendon components (e.g., tendon wires, tendon-anchorage components), (2) examination of corrosion-inhibiting medium (i.e., grease), and (3) analysis to determine the containment prestressing forces.
- 1. Examination of Post-Tensioning Tendon Components: All accessible grease caps were visually examined for grease leakage and for grease cap deformations, in accordance with 10 CFR 50.55a(b)(2)(ix)(A). The licensee identified several hoop and vertical tendons with grease leakage from the grease caps. Twenty-three hoop tendons were identified requiring grease cap modifications and gasket replacements, and six hoop tendons were identified requiring only gasket replacements. Five vertical tendons were identified requiring gasket replacements.
The licensee also examined the anchor-heads, shims, and bearing plates of the sampled 13 tendons. No evidence of cracking or degradations were noted on any of these components. One tendon in each group of tendons was detensioned for removal of a sample wire. The sample wires were found to be free of physical damage. Their ultimate strengths and elongations were found to meet or exceed the minimum specified values. The NRC staff finds the procedures used in the examination of post-tensioning tendon components in accordance with IWL-2523.
- 2. Examination of Corrosion-Inhibiting Grease: Samples of grease were obtained and analyzed in accordance with Table IWL-2525.1. In one sample, the licensee identified nitrate concentration greater than the acceptance limit of 10 parts-per-million (ppm).
The examination of a back-up sample met the acceptance criterion. The water content in the grease samples was found to be less than the 10-percent limit established in
10 CFR 50.55a(b)(2)(ix)(D)(1). The NRC staff finds the procedure for examining the grease and documenting the results to be adequate.
- 3. Determination of Prestressing Force Level: Lift-off forces of 4 vertical, 5 hoop, and 3 dome tendons were determined using the feeler gage pull out method. The licensee had estimated the lower predicted prestressing force limits (PPLs) for these tendons.
The licensee compared these PPLs with the corresponding measured lift-off forces and determined if they met the acceptance criteria of IWL-3221.1. A review of Table 1, Tendon Forces, Acceptance Limits & Margins, in Attachment 1 of the report indicates that the measured prestressing forces met the acceptance criteria.
In order to perform the tendon force trending analysis, the licensee established the minimum required (prestressing force) value for each group of tendons. In developing the trends, the licensee disregarded the measurements recorded prior to the 10th year surveillance, considering them as unreliable. The licensee used the 10th, 15th, 20th, and the 25th year measured tendon data for evaluating the adequacy of the prestressing forces in each of the three directions, i.e. hoop, vertical and dome.
In the conference call on March 7, 2001, the NRC questioned the approach of applying a normalization process (used for adjusting the estimated tendon forces to account for elastic shortening losses, etc.) to the measured tendon forces. The licensee revised TR 136 and submitted Revision 01 of the report with the non-normalized measured prestressing forces on September 17, 2001 (Reference 3).
In Section 4 of Revision 01 of the topical report, the licensee identifies the areas of follow-up examination to be performed during the next tendon surveillance. Overall, the NRC staff finds the procedures utilized, documentation prepared, and description of the follow-up examination in accordance with the containment ISI requirements in 10 CFR 50.55a and are acceptable.
3.0 CONCLUSION
Based on this review, the NRC staff finds that the procedures used by the licensee to perform the 25th year tendon surveillance and the methods used in evaluating the surveillance results are in accordance with NRC staffs recommendations in the NRC staffs SE of August 28, 1997.
Additionally, the report also serves to fulfil the requirement of 10 CFR 50.55a and IWL-3300 of the ASME Code to provide an engineering evaluation report. Based on the review of the report, the NRC staff concludes that the procedures and method of evaluations used for examination of concrete and the post-tensioning system are acceptable
4.0 REFERENCES
- 1. Letter from B. Buckley, NRC, to J. Langenbach, GPU Nuclear Corporation, Three Mile Island Nuclear Station, Unit 1 (TMI-1) Review of Twenty-Year Reactor Building Tendon Surveillance Report (TAC NO. M92045), August 28, 1997.
- 2. Letter from AmerGen Energy Company to NRC, Twenty-Fifth Year Reactor Building Tendon Surveillance (Period 7), Three Mile Island, Unit 1 (TMI Unit 1), February 25, 2000.
- 3. Letter from AmerGen Energy Company to NRC, Additional Information - TMI Unit 1 25th Year Reactor Building Tendon Surveillance Report, September 17, 2001.
Principal contributor: H. Asher Date: February 12, 2002
Three Mile Island Nuclear Station, Unit No. 1 cc:
John Skolds Chairman Chief Operating Officer Board of County Commissioners Exelon Generating Company, LLC of Dauphin County 4300 Winfield Road Dauphin County Courthouse Warrenville, IL 60555 Harrisburg, PA 17120 William Bohlke Chairman Senior Vice President Nuclear Services Board of Supervisors Exelon Generating Company, LLC of Londonderry Township 4300 Winfield Road R.D. #1, Geyers Church Road Warrenville, IL 60555 Middletown, PA 17057 John B. Cotton Senior Resident Inspector (TMI-1)
Senior Vice President - Operations Support U.S. Nuclear Regulatory Commission Exelon Generating Company, LLC P.O. Box 219 4300 Winfield Road Middletown, PA 17057 Warrenville, IL 60555 Michael P. Gallagher Joseph J. Hagan Director - Licensing Senior Vice President - Exelon Generation Company, LLC Mid Atlantic Regional Operating Group Correspondence Control Desk Exelon Generation Company, LLC P.O. Box 160 200 Exelon Way, Suite 305 Kennett Square, PA 19348 Kennett Square, PA 19348 David J. Allard, Director Jeffrey A. Benjamin Bureau of Radiation Protection Vice President - Pennsylvania Department of Licensing and Regulatory Affairs Environmental Protection Exelon Generation Company, LLC P.O. Box 8469 4300 Winfield Road Harrisburg, PA 17105 Warrenville, IL 60555 George H. Gellrich Mark E. Warner Plant Manager Vice President TMI Unit 1 TMI Unit 1 AmerGen Energy Company, LLC AmerGen Energy Company, LLC P. O. Box 480 P. O. Box 480 Middletown, PA 17057 Middletown, PA 17057 James J. McElwain Regional Administrator Manager - Regulatory Assurance Region I TMI Unit 1 U.S. Nuclear Regulatory Commission AmerGen Energy Company, LLC 475 Allendale Road P.O. Box 480 King of Prussia, PA 19406 Middletown, PA 17057
Three Mile Island Nuclear Station, Unit No. 1 cc: continued John F. Rogge, Region I U.S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 Edward J. Cullen, Jr., Esquire Vice President, General Counsel and Secretary Exelon Generation Company, LLC 300 Exelon Way Kennett Square, PA 19348 Michael A. Schoppman Framatome ANP Suite 705 1911 North Ft. Myer Drive Rosslyn, VA 22209 Dr. Judith Johnsrud National Energy Committee Sierra Club 433 Orlando Avenue State College, PA 16803 Eric Epstein TMI Alert 4100 Hillsdale Road Harrisburg, PA 17112