ML14058B182
| ML14058B182 | |
| Person / Time | |
|---|---|
| Site: | Byron, Braidwood  |
| Issue date: | 03/18/2014 |
| From: | Robinson L R License Renewal Projects Branch 1 |
| To: | Gallagher M P Exelon Generation Co |
| Robins R L, 415-4115 | |
| References | |
| TAC MF1879, TAC MF1880, TAC MF1881, TAC MF1882 | |
| Download: ML14058B182 (14) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 March 18, 2014 Mr. Michael P. Gallagher Vice President, License Renewal Projects Exelon Generation Company, LLC 200 Exelon Way Kennett Square, PA 19348 SUBJECT: REQUEST FOR ADDITIONAL INFORMATION FOR THE REVIEW OF THE BYRON STATION, UNITS 1 AND 2, AND BRAIDWOOD STATION, UNITS 1 AND 2, LICENSE RENEWAL APPLICATION, SET 14 (TAG NOS. MF1879, MF1880, MF1881, AND MF1882) Dear Mr. Gallagher: By letter dated May 29, 2013, Exelon Generation Company, LLC, submitted an application pursuant to Title 10 of the Code of Federal Regulations Part 54, to renew the operating licenses NPF-37, NPF-66, NPF-72, and NPF-77 for Byron Station, Units 1 and 2, and Braidwood Station, Units 1 and 2, respectively, for review by the U.S. Nuclear Regulatory Commission (NRC or the staff). The staff is reviewing the information contained in the license renewal application and has identified, in the enclosure, areas where additional information is needed to complete the rev1ew. These requests for additional information were discussed with John Hufnagel, and a mutually agreeable date for the response is within 30 days from the date of this letter. If you have any questions, please contact me at 301-415-4115 or e-mail Lindsay.Robinson@nrc.gov. Sincerely, Lindsay R. Robinson, Project Manager Projects Branch 1 Division of License Renewal Office of Nuclear Reactor Regulation Docket Nos. 50-454, 50-455, 50-456, and 50-457 Enclosure: Request for Additional Information cc: Listserv March 18, 2014 Mr. Michael P. Gallagher Vice President, License Renewal Projects Exelon Generation Company, LLC 200 Exelon Way Kennett Square, PA 19348 SUBJECT: REQUEST FOR ADDITIONAL INFORMATION FOR THE REVIEW OF THE BYRON STATION, UNITS 1 AND 2, AND BRAIDWOOD STATION, UNITS 1 AND 2, LICENSE RENEWAL APPLICATION, SET 14 (TAG NOS. MF1879, MF1880, MF1881, AND MF1882) Dear Mr. Gallagher: By letter dated May 29, 2013, Exelon Generation Company, LLC, submitted an application pursuant to Title 10 of the Code of Federal Regulations Part 54, to renew the operating licenses NPF-37, NPF-66, NPF-72, and NPF-77 for Byron Station, Units 1 and 2, and Braidwood Station, Units 1 and 2, respectively, for review by the U.S. Nuclear Regulatory Commission {NRC or the staff). The staff is reviewing the information contained in the license renewal application and has identified, in the enclosure, areas where additional information is needed to complete the review. These requests for additional information were discussed with John Hufnagel, and a mutually agreeable date for the response is within 30 days from the date of this letter. If you have any questions, please contact me at 301-415-4115 or e-mail Lindsay.Robinson@nrc.gov. Sincerely, IRA! Lindsay R. Robinson, Project Manager Projects Branch 1 Division of License Renewal Office of Nuclear Reactor Regulation Docket Nos. 50-454, 50-455, 50-456, and 50-457 Enclosure: Request for Additional Information cc: Listserv DISTRIBUTION: See following pages ADAMS Acces . No* ML 14058B182 SIOn *concurred via email OFFICE LA:DLR' PM: RPB1 :DLR PM:RPB1 :DLR BC:RPB1 :DLR PM:RPB1 :DLR NAME YEdmonds LRobinson JDaily YDiazSanabria LRobinson DATE 3/5/14 3/12/14 3/12/14 313//14 3/18/14 OFFICIAL RECORD COPY Letter to M.P. Gallagher from Lindsay R. Robinson dated March 18, 2014 SUBJECT: REQUEST FOR ADDITIONAL INFORMATION FOR THE REVIEW OF THE BYRON STATION, UNITS 1 AND 2, AND BRAIDWOOD STATION, UNITS 1 AND 2, LICENSE RENEWAL APPLICATION, SET 14 (TAC NOS. MF1879, MF1880, MF1881, AND MF1882) DISTRIBUTION EMAIL: PUBLIC RidsNrrDir Resource RidsNrrDirRpb1 Resource RidsNrrDirRasb Resource RidsOgcMaiiCenter RidsNrrPMByron Resource RidsNrrPMBraidwood Resource LRobinson JDaily DMclntyre, OPA JMcGhee, Rill EDuncan, Rill JBenjamin, Rill AGarmoe, Rill JRobbins, Rill VMitlyng, Rill PChandrathil. Rill RAI 8.3.1.2*1 Applicability: BYRON STATION, UNITS 1 AND 2, AND BRAIDWOOD STATION, UNITS 1 AND 2, LICENSE RENEWAL APPLICATION REQUEST FOR ADDITIONAL INFORMATION, SET 14 (TAC NOS. MF1879, MF1880, MF1881, MF1882) Byron Station (Byron) and Braidwood Station (Braidwood), all units Background: License renewal application (LRA) Section 8.3.1.2 states that the "Concrete Containment Tendon Prestress" aging management program (AMP) is consistent with an enhancement with the Generic Aging Lessons Learned (GALL) Report, Revision 2, AMP X.S1, "Concrete Containment Tendon Prestress." The "monitoring and trending" program element of the GALL Report AMP X.S1 states that "the trend line represents the trend of prestressing forces based on the actual measured forces" and that NRC Information Notice (IN) 99-10, "Degradation of Prestressing Tendon Systems in Prestressed Concrete Containments," provides guidance for constructing the trend line. LRA Section 8.3.1.2 also states that the "[t]rend line regression analysis is consistent with NRC Information Notice (IN) 99-10." The LRA further states that the "[t]rend lines, one for each tendon group, are constructed using the measured tendon forces and represent the changes in mean vertical, hoop and dome prestressing forces with time" and that "the analysis evaluates force trends by group (dome, hoop, vertical) and shows that group mean forces will not fall below applicable [minimum required values] MRV's prior to the end of the period of extended operation." Issue: Table IWL-2521-1 in Subsection IWL of the ASME Code,Section XI, states that for each tendon group the number of tendons to be examined varies between 2 to 5 percent of the tendon population. IN 99-10 discusses that for a small sample size, using the average of the tendon force (TF) for each surveillance test masks the true variation between TF and time (T) (i.e., the tendency of the TF to vary systematically with T, where the scattering of points about the "curve" represents the true relationship between TF and T). The staff noted that LRA Figures 4.5-1 through 4.5-12 show that multiple tendon values are plotted for past inservice inspection (lSI) years. It is not clear whether the applicant uses average/mean TF or individual lift-off values when developing the trend lines. Request: Clarify the methodology used for the construction of the regression analysis. Specifically, state whether the Byron and Braidwood regression analyses use the individual lift-off forces for the development of statistically validated trend lines. ENCLOSURE
-2-RAI 8.3.1.2-2 Applicability: Byron and Braidwood Background: LRA Section 8.3.1.2 states that the "Concrete Containment Tendon Prestress" AMP is consistent with an enhancement with the GALL Report, Revision 2, AMP X.S1, "Concrete Containment Tendon Prestress." The GALL Report AMP X.S1, in its program description, states that "[t]he program consists of an assessment of inspections performed in accordance with the requirements of Subsection IWL of the ASME Code,Section XI, as supplemented by the requirements of 10 CFR 50.55a(b)(2)(viii)" and that the parameters monitored are the prestressing TF in prestressed concrete containments. LRA Section 8.3.1.2 states that "[t]he program requires measurement of prestressing forces on an initial 2% sample of each tendon group (dome, hoop, vertical) every five years, as specified in lWL-2400." The LRA also states in the "operating experience" program element Issue: In 2009 and 2011, Byron and Braidwood, respectively, performed the 251r year interval ASME Section XI, Subsection lWL, examinations of the concrete containment tendons. These examinations included testing to assess the loss of prestressing forces in select containment tendons, consistent with IWL requirements. The audited procedure ER-AA-330-006, "lSI and Testing of the Prestressed Concrete Containment Post Tensioning System, Rev. 6," indicates that Byron and Braidwood alternate every ten years between visual and full examinations which include testing and measurements of TF. Subsection IWL-2421 of Section XI of the ASME Code allows the examination frequency to be modified if the containments are essentially identical in design, utilize the same prestressing systems, and post tensioning operations were completed within two years apart. If all criteria are met, then full examinations as required by IWL-2500 shall be performed at 1, 3, and 10 years and every 1 0 years thereafter for the first containment unit; and for each subsequent containment constructed at the site, examinations shall be performed at 1, 5, and 15 years and every 10 years thereafter. It is not clear whether Byron and Braidwood follow the modified lSI intervals as stated in IWL-2421 and procedure ER-AA-330-006 to perform measurement of TF at alternating time frames for each unit (e.g., one unit fully examined per IWL-2500 on year 20 while the other on year 25) or examines, tests, and measures TF for both units at each site every five years, as stated in the LRA. Request: Clarify the frequency of measuring the prestressing tendon forces for each selected tendon group (dome, hoop, vertical) sample examined during ISis for Byron and Braidwood, all units.
-3 -RAI 8.2.1.34-1 Applicability: Byron and Braidwood Background: LRA Section 8.2.1.34 states that the "Structures Monitoring" AMP is consistent with enhancements with the GALL Report, Revision 2, AMP XI.S6, "Structures Monitoring " During a walkdown of Byron and Braidwood's main steam and tendon gallery tunnels, the staff observed white material deposits, or efflorescence, on some below-grade reinforced concrete walls. The conditions at Byron are far more evident than at Braidwood. A review of operating experience revealed similar conditions in the auxiliary feedwater tunnel concrete walls. Through discussions with the applicant, the staff learned that the cracks through which the material appears to be leaching have existed since initial plant construction, and the material deposits are considered to be the result of the limestone backfill migrating through these cracks. The staff noted that the groundwater at both Byron and Braidwood is considered to be an aggressive environment due to high chloride levels (i.e., >500 ppm). Per 10 CFR 54.21 (a)(3), the applicant is required to demonstrate that the effects of aging will be adequately managed so that the intended function will be maintained consistent with the current licensing basis for the period of extended operation. However, without knowing the source of the material deposits in the main steam, auxiliary feedwater, and tendon gallery tunnels (i.e., whether the material deposits are a result of the limestone backfill migrating through the cracks or material leaching from the concrete structures), the staff does not have sufficient information to conclude that the proposed LRA AMP, "Structures Monitoring," will be adequate to manage the effects of aging during the period of extended operation. Requests: 1. State what actions, if any, have been taken to determine the composition of the material (white deposits) State whether an evaluation has been performed to determine the source of the material deposits. If so, provide the technical basis for that conclusion. 2. Considering that the groundwater at Byron and Braidwood is aggressive, state what actions, if any, have been taken to evaluate the condition of the concrete in these below-grade structures. RAI 8.2.1.30-1 Applicability: Byron and Braidwood Background: LRA Section 8.2.1.30 states that the ASME Section XI, Subsection IWL AMP is an existing program that, following enhancements, will be consistent with the GALL Report AMP XI.S2, "ASME Section XI, Subsection IWL During its onsite audit at both Byron and Braidwood, the
-4 -staff reviewed operating experience regarding suspected areas of degradation in the primary containment tendon access gallery tunnel ceilings. The staff noted that, in June 2006, while performing visual examinations of Braidwood's tunnel ceilings concrete surfaces, 11 locations in Unit 1 and 14 locations in Unit 2 were identified as suspect areas with degradation. The suspected areas were covered in white deposits and rust. In addition, during the 2006 20th ASME Section XI, Subsection IWL, concrete examinations at Braidwood Units 1 and 2, degradation was found in the tendon tunnel ceilings near seven vertical tendon anchorage cans. The degradation was within a previously placed patch that extended from the outer wall to the inner wall in the tendon tunnel and consisted of a combination of the following: wet stalactites. surface concrete cracks exceeding .04", heavy accumulation of minerals, corrosion staining, moisture "wetting," accumulation of efflorescence in localized areas, "minor" cracking, and "hollow" sound emitted from the area when tapped with a hammer. In 2012, while performing augmented examinations of suspect areas identified during the 2011 251h year ASME IWL examinations, the following conditions were found at Braidwood Unit 2 tendon tunnel ceilings near six additional vertical tendon anchorage cans: buildup of minerals, efflorescence with evidence of moisture, 8" and 5" long stalactites, and surface corrosion on embedded plates. During the onsite audits at both Byron and Braidwood, the staff performed walkdowns of the tendon access gallery tunnels to observe the overall condition of the area. The staff observed white deposits or efflorescence, stalactites, surface corrosion on embedded plates, and surface cracks in the tunnel ceilings near some of the vertical tendon anchorage cans. The staff noted that the conditions of concrete degradation at the tendon gallery tunnel ceilings are present at both sites. In addition, based on its review of operating experience, the staff noted that the groundwater at both Byron and Braidwood is considered to be an aggressive environment due to high chloride levels (i.e , > 500 ppm). Issue: Per 10 CFR 54.21(a)(3), the applicant is required to demonstrate that the effects of aging will be adequately managed so that the intended function will be maintained consistent with the current licensing basis for the period of extended operation. The staff is concerned that some below-grade areas of the concrete containment are exposed to aggressive groundwater, which may be causing chemical attack and leaching of the concrete. It is not clear whether an evaluation has been performed to assess this condition per the requirements of the IWL Code. The staff needs additional information to determine whether the LRA ASME Section XI, Subsection IWL AMP will be adequate to manage the effects of aging during the period of operation (PEO). Request: State whether the concrete in the tunnel ceiling is subject to chemical attack or leaching, and provide results of any evaluation conducted or planned to determine the composition of the material (e.g., mineral build-up, white efflorescence) and to evaluate the condition of the concrete at the tendon gallery tunnel ceilings.
-5 -RAI 8.2.1.30-2 Applicability: Braidwood Background: LRA Section 8.2.1.30 states that the ASME Section XI, Subsection IWL AMP is an existing program that, following enhancements, will be consistent with the GALL Report AMP XLS2, "ASME Section XI, Subsection IWL." During its review of Braidwood operating experience, the staff noted that ASME Section XI, Subsection IWL inspections have revealed that the sealant and cover are significantly degraded or missing at some of the drain assemblies 1n the dome area of the containment. Plant operating experience has documented that there is separation, chips, and loose concrete at some of the dome drains; accumulation of white deposits or efflorescence on concrete surfaces near all of the drains; and accumulation of water at the dome drains. The staff noted that the applicant performed a detailed visual examination of the suspected areas of concrete deterioration in accordance with Subsection IWL-321 0 of the ASME Code. During the detailed visual examinations, additional signs of deterioration were found on suspected areas of concrete in the form of "minor" spalls near the drains and cracks extending from all six dome drain penetrations (one reported as being more than 6" long and .8" wide at the concrete surface), efflorescence within the cracks, and corrosion staining. Issue: Per 10 CFR 54.21 (a)(3), the applicant is required to demonstrate that the effects of aging will be adequately managed so that the intended function will be maintained consistent with the current licensing basis for the period of extended operation. The staff noted that issues with degradation of the dome drainage system and suspected areas of concrete deterioration have been identified during previous ASME Section XI, Subsection IWL examinations at Braidwood. The staff is concerned that the conditions observed by the applicant near the dome drains (accumulation of white deposits, water accumulation, spalling, cracks, and corrosion staining) may be indicative of, or may result in, degradation. The water accumulated may leak through the cracks and reach the concrete rebar which can result in degradation of the rebar. The staff needs additional information regarding the condition of concrete suspected areas of degradation and methods of evaluation to conclude that the LRA ASME Section XI, Subsection IWL AMP will be adequate to manage the effects of aging during the period of extended operation. Request: Regarding the reported conditions of the containment concrete at the dome drainage system, state whether further actions have been taken or are needed per appropriate programs such that concrete degradation can be evaluated and appropriate mitigating actions are implemented to prevent loss of intended function during the period of extended operation. Also, provide a summary of actions that have been taken to date to correct the degraded condition of the dome drainage system such that water does not accumulate in the suspected areas of concrete degradation near the dome drains.
-6-RAI 8.2.1.30-3 Applicability: Braidwood Background: LRA Section 8.2.1.30 states that the ASME Section XI, Subsection IWL AMP is an existing program that, following enhancements, will be consistent with the GALL Report AMP XI.S2, ASME Section XI, Subsection IWL." LRA Section 8.2.1.30 states that "free-water has been found in 3-8% of the tendon inspections at Braidwood Unit 2 ... the presence of free water has been consistently detected in specific horizontal, vertical, and dome tendons, and this type of condition has also been detected [at] Braidwood Unit 1." The LRA further states that, since Braidwood construction, free water has been found in a "few, specific horizontal and vertical tendon anchorages located below grade." The LRA also states that the water in the dome tendons is due to the degraded dome drainage system and that the water found at vertical tendons and below-grade horizontal tendons is due to the high water table, which is about 20 to 25 feet higher than the bottom of the containment. LRA Section 8.2.1.30 states that to address the presence of water in the tendon sheaths, the applicant has performed augmented inspections on additional tendons beyond those selected for the ASME Section XI, Subsection IWL Program. These augmented inspections are performed every five years in conjunction with the ASME Section XI, Subsection IWL examinations. The LRA also states that due to the history of water found in containment tendons, the applicant included Enhancements 2 and 3 to the ASME Section XI, Subsection IWLAMP. Enhancement 2 states: A one-time inspection of one (1) vertical and one (1) horizontal tendon on each unit will be performed prior to the period of extended operation. The inspection will consist of visually examining one ( 1) wire from each of the two (2) types of tendons at a worst-case location based on evidence of free water, grease discoloration, and grease chemistry results. This location will serve as a leading indicator for potential degradation or tendon surface corrosion (Braidwood only). Enhancement 3 states: In order to monitor for tendon exposure to free water and moisture and manage any potential adverse effects, a periodic tendon water monitoring and grease sampling program will be implemented (Braidwood only). The program will consist of: (a) A baseline inspection of tendon grease caps at the bottom of all vertical and dome tendons, as well as all below-grade horizontal tendons, prior to the period of extended operation. The baseline inspection will check for evidence of free water and grease discoloration, with further actions taken based on the condition of the grease. (b) A follow-up tendon grease cap inspection of all vertical and dome tendons, as well as all below-grade horizontal tendons, will be performed within 10 years of the initial inspection, using the same approach as the baseline inspection.
Issue: -7 -(c) For those tendons where free water, moisture, and grease did not meet acceptance criteria during the two (2) previous inspections, periodic monitoring of grease chemistry and moisture, free water, and grease discoloration will be performed on a frequency not to exceed 10 years. Corrective actions will be taken as necessary to ensure that the tendon grease meets ASME Section XI, Subsection IWL requirements. The GALL Report states that "the conditions and operating experience at the plant must be bound by the conditions and operating experience for which the GALL program was evaluated, otherwise it is incumbent on the applicant to augment the GALL program as appropriate to address the additional aging effects." The GALL Report also states that "[o]perating experience involving the AMP, including past corrective actions resulting in program enhancements or additional programs, should provide objective evidence to support a determination that the effects of aging will be adequately managed so that the structure and component intended functions will be maintained during the period of extended operation." The staff noted that the applicant has augmented and will enhance (Enhancements 2 and 3) its IWL AMP to address its plant-specific operating experience regarding the historical exposure of tendons to free water at Braidwood. However, the staff needs additional information regarding how the augmented inspections and enhancements will adequately manage the effects of aging during the period of extended operation. The staff has the following concerns:
- For the augmented inspections of additional tendons, performed every five years in conjunction with the ASME Section XI, Subsection IWL examinations, it is unclear how the locations for additional tendon inspections will be identified.
- Enhancement 2 proposes a one-time inspection of one horizontal and vertical tendon prior to the period of extended operation. lt is not clear what the acceptance criteria will be for the one-time inspection of the corrosion protection medium and tendon wires and what further actions will be taken if the acceptance criteria are not met. Additionally, the enhancement does not include inspection of dome tendons, and the basis for this exclusion is not clear.
- Enhancement 3 states that a follow-up inspection will be performed within 10 years after the first baseline inspection. The enhancement also states that tendons that do not meet the acceptance criteria during the two previous inspections will be subject to periodic monitoring at a frequency not to exceed 10 years. The staff is concerned that tendons that meet the acceptance criteria during the baseline inspection but do not meet the acceptance criteria in the follow-up inspection will not be subject to periodic monitoring. For sites with multiple plants, IWL-2421 (b) states that when the conditions on lWL-2421 (a) are met, the examinations required by IWL-2500 can be performed at a 1 0-year frequency instead of every five years. A 1 0-year frequency is the maximum frequency (less conservative approach) allowed by the IWL Code for a site with multiple plants. lt is unclear as to how a frequency of examinations not to exceed 10 years will be adequate to address the additional aging effects at Braidwood.
-8 -Request: 1. Describe how the locations for augmented inspections of additional tendons will be identified 2. Regarding Enhancement 2, state (1) the acceptance criteria for the one-time inspections, (2) what actions will be taken if the acceptance criteria are not met, and (3) the justification for not performing a one-time inspection of the dome tendons. 3. Regarding Enhancement 3, state (1) what actions will be taken for those tendons where the corrosion protection medium meets the acceptance criteria during the baseline inspection but are found not acceptable during the follow-up inspection, and (2) how the proposed frequency of inspections (not to exceed 10 years) will ensure that possible age-related degradation due to water in leakage to the tendons will be detected in a timely manner and managed such that the tendons will continue to peliorm their intended functions during the PEO RAI 8.2.1.30-4 Applicability: Braidwood Background: LRA Section B.2.1.30 states that the ASME Section XI, Subsection IWL AMP is an existing program that, following enhancements, will be consistent with the GALL Report AMP XI.S2, "'ASME Section XI, Subsection IWL." The GALL Report AMP XI.S2 states that "IWL-2510 specifies that concrete suliaces are examined for conditions indicative of degradation, such as those defined in American Concrete Institute (ACI) 201.1 Rand ACI 349.3R." ACI 201.1 R, "Guide for Conducting a Visual Inspection of Concrete Suliaces," and ACI 349.3R, "Evaluation of Existing Nuclear Safety-Related Concrete Structures," identify rust staining as a condition that may be indicative of concrete degradation. The GALL Report also states that "visual examination methods and testing would identify the aging effects of accessible concrete components." During the Byron and Braidwood onsite AMP audits, the staff performed a walkdown to observe the exterior surfaces of Braidwood Units 1 and 2 containments and noted a vertical tine of rust staining on the south face of the Unit 2 concrete containment. Issue: As described in ACI 349.3R, rust staining is a condition that can be indicative of active corrosion of iron based material that is taking place internally in the concrete containment or externally on the surface of the structure. Based on the review of the Braidwood operating experience, on-site available documentation, and interviews with the applicant, it's not clear (1) what is the cause of the rust staining, (2) whether the noted condition is indicative of age related degradation, and (3) how the condition is being addressed (e.g., through visual examination methods and testing consistent with the ASME Section XI, Subsection IWL AMP).
-9 -Request: 1. Identify the cause of the verticalline(s) of rust stains. 2. State whether there are aging effects associated with the rust stains. 3. State whether the rust stains have been evaluated and will be monitored consistent with IWL*251 0. Provide a summary of your results and the technical basis for the response. RAI 6.2.1.29-1 Applicabilitv: Byron Background: LRA Section 8.2.1.29 states that the ASME Section XI, Subsection IWE AMP is an existing program that, following enhancement, will be consistent with the GALL Report, Revision 2, AMP XI.S1. The "detection of aging effects" program element recommends, in accordance with IWE-1240, that augmented examinations should be performed for containment surface areas subject to degradation. In addition, the GALL Report states that operating experience involving the AMP should provide objective evidence to support a determination that the effects of aging will be adequately managed so that the structure and component intended functions will be maintained during the PEO. During the audit, the staff performed walkdowns of the Byron main steam and tendon gallery tunnels and observed white material deposits on the concrete walls and tendon gallery tunnel ceilings, indicative of water leakage or seepage through the containment concrete. Through discussions with the applicant, the staff learned that the cracks, through which the material appears to be leaching, have existed since initial plant construction. The staff noted during its review that on the south side of Byron Unit 1 and north side of Unit 2, the below grade areas between the main steam tunnels and containment structures were in-filled with limestone during the original construction. According to plant operating experience, this area has allowed groundwater infiltration to the below-grade containment concrete. The staff noted that the groundwater at both Byron and Braidwood is considered to be an aggressive environment due to high chloride levels (i.e., >500 ppm). lWE-1240 states that interior and exterior containment surface areas that are subject to accelerated corrosion, with no or minimal corrosion allowance, require augmented examinations. Issue: With the history of aggressive water infiltrating the containment concrete, as evidenced by signs of water intrusion at the tendon gallery ceilings, there is the potential that elevated moisture levels at the outside of the containment concrete could cause moisture to travel through the concrete and come in contact with the carbon steel containment liner. This condition could result in degradation of the containment liner plates caused by accelerated corrosion at exterior surfaces of the containment liner. The applicant has not provided information, based on examination or analysis, on a determination as to whether water has been in contact with the outer surface of the liner or whether there has been any loss of thickness in the carbon steel due to accelerated corrosion in order to ensure the requirements of IWE-1240 are met.
-1 0 -Request With regards to the operating experience indicating that water is infiltrating the containment concrete, state whether there has been (or will be) an evaluation in accordance with IWE to determine (1) if the moisture could come into contact with the liner plate and (2) any resulting loss of material thickness due to corrosion. Describe how the IWE AMP will be able to ensure that the liner is not degraded such that the teak-tight integrity of the carbon steel is maintained through the PEO. RAI 8.2.1.29-2 Applicability: Byron and Braidwood Background: LRA Section 8.2.1.29 states that the ASME Section XI, Subsection IWE AMP is an existing program that, following enhancement, will be consistent with the GALL Report, Revision 2, AMP XI.S1. The "operating experience" program element recommends that the ASME Section XI, Subsection IWE program consider operating experience regarding liner plate and containment shell corrosion. The applicant should demonstrate that it utilizes industry operating experience in development of the AMP. There is recent industry operating experience which has indicated that at some plants, the implementation of the IWE program has been ineffective in identifying moisture intrusion into the leak chase channel areas and potential leakage to the containment shell and liner seam welds. This issue is discussed in NRC Integrated Inspection Report 05000348/2012003 and 0500036412012003 (Joseph M. Farley Nuclear Plant}; NRC Integrated Inspection Report 0500039512011003 (Virgil C. Summer Nuclear Station}; and NRC Integrated Inspection Report 0500032712012005 and 05000328/2012005 (Sequoyah Nuclear Plant}. Some licensees were not performing general visual examinations of 100 percent of the containment liner plate leak chase systems in accordance with ASME Code Section XI, Subsection IWE requirements; and upon inspection, moisture was discovered in the leak chase channel system. Moisture intrusion into the leak chase channel system could reach the containment seam welds. This has the potential to cause corrosion at the welds and affect leak-tightness at the containment or liner pressure boundary. Issue: Regarding the recent industry operating experience concerning implementation of the 100 percent visual inspection requirements of the ASME Code IWE and the GALL Report recommendation that the applicant consider industry operating experience in development of the ASME Section XI, Subsection IWE AMP, the staff needs additional information for applicability to Byron and Braidwood. Request Considering the recent industry operating experience described above regarding implementation of the IWE visual examinations, inspections of the leak chase channel system, and concerns of standing water or moisture intrusion to the containment liner plate, state what
-11 -actions have been or will be taken to (1) determine whether there is moisture in the leak chase channel area and (2) ensure the IWE program will be effective in ensuring moisture intrusion and corrosion do not affect the carbon steel containment liner through the PEO.