ML13016A523
| ML13016A523 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 01/11/2013 |
| From: | - No Known Affiliation |
| To: | Division of License Renewal |
| References | |
| Download: ML13016A523 (5) | |
Text
Davis-BesseNPEm Resource From: dorts@firstenergycorp.com Sent: Friday, January 11, 2013 9:48 AM To: CuadradoDeJesus, Samuel Cc: custerc@firstenergycorp.com
Subject:
FENOC Telephone Conference Summary -- High Strength Bolting Attachments: NRC telecon 20121214 RAI High Strength Structural Bolts.pdf Sam..... attached is a copy of the FENOC telecon summary from the discussions on the Davis-Besse License Renewal high strength bolting request for additional information (RAI) B.2.4-1a, held on December 14 and December 19, 2012.
Both telecons were documented in the attached telecon summary.
Please contact Cliff Custer or me with questions on the attached telecon summary.
Thank you, Steve Dort FENOC License Renewal
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1
Hearing Identifier: Davis_BesseLicenseRenewal_Saf_NonPublic Email Number: 4010 Mail Envelope Properties (OF8392A16D.3AA16DB3-ON85257AF0.0050B26E-85257AF0.00514698)
Subject:
FENOC Telephone Conference Summary -- High Strength Bolting Sent Date: 1/11/2013 9:47:44 AM Received Date: 1/11/2013 9:47:53 AM From: dorts@firstenergycorp.com Created By: dorts@firstenergycorp.com Recipients:
"custerc@firstenergycorp.com" <custerc@firstenergycorp.com>
Tracking Status: None "CuadradoDeJesus, Samuel" <Samuel.CuadradoDeJesus@nrc.gov>
Tracking Status: None Post Office: FirstEnergyCorp.com Files Size Date & Time MESSAGE 1024 1/11/2013 9:47:53 AM NRC telecon 20121214 RAI High Strength Structural Bolts.pdf 28983 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:
Recipients Received:
Doc No. 121412 TO: File DATE: December 14, 2012 FROM: Larry Hinkle
SUBJECT:
NRC Telecon Regarding Davis-Besse License Renewal -
Request For Additional information (RAI) B.2.4-1a Related To High Strength Bolting NRC Attendees: Sam Cuadrado de Jesús, Bill Holston FENOC Attendees: Ken Byrd, Jon Hook, Trent Henline, Jake Hofelich, Dewey-Munson, Cliff Custer, Don Kosloff, Larry Hinkle This telephone conference call was initiated by Sam Cuadrado de Jesús, NRC Project Manager for Davis-Besse License Renewal. The telecon took place at 0900 hours0.0104 days <br />0.25 hours <br />0.00149 weeks <br />3.4245e-4 months <br /> on December 14, 2012. The purpose of the call was to discuss RAI B.2.4-1a related to high strength structural bolting, issued by NRC letter dated November 14, 2012 (ML12318A246). The request includes the following items:
a) The ASTM A 540 grade and class of materials that are used in in-scope structural locations.
b) If grade and class materials were used that have a minimum specified yield equal to or higher than 130 ksi, the actual measured yield strength of in service bolts.
c) If none of the currently installed bolts are high strength bolts, what controls will be in place to ensure that the actual measured yield strengths of A 540 supplied replacements will not exceed 150 ksi.
d) If high strength ASTM A-540 bolting material has been used in in-scope structural applications, what inspections will be conducted.
e) If visual examinations will be used to detect corrosion or conditions indicative of a corrosive environment in lieu of volumetric or surface (for removed bolts) examinations to detect stress corrosion cracking (SCC), the definition for a corrosive environment at Davis-Besse, and the threshold for which an environment will be classified as corrosive.
f) How it will be demonstrated that a non-corrosive environment is maintained for all high strength bolts, and how visual inspections will be able to detect all instances of corrosion or a corrosive environment, or update the aging management program (AMP) to show that volumetric examinations comparable to that of American Society of Mechanical Engineers Code Section XI, Table IWB-2500-1, Examination Category BG-1 are being performed on high strength bolting.
2 FENOC described the bolting used at Davis-Besse includes A540 Gr.B23 Cl3 bolting.
A review of the Certified Material Test Reports of A540 bolting installed at Davis-Besse has concluded that for 216 of these bolts in the population, the yield strength has either been determined to be > 150 ksi or it was indeterminate by a search of site records. This population of 216 bolts is considered to conservatively bound the high strength structural bolting of 1 or larger diameter in use at the site. Typical locations for this bolting include building support connections for the Reactor Coolant Pumps, Reactor Vessel Supports, and the Decay Heat Suction line from the Reactor Coolant system. Per site drawings, all of the bolting in this population is embedded in concrete with a coating installed at the bolt/nut head and interfacing structural steel. Some of this bolting is greater than 7 feet in length, with the majority of the bolt threads encased in concrete. As such, a visual walk down of the bolting every 5 years is proposed to confirm a corrosive environment does not exist and has not existed at the site of the bolting location and immediate surrounding area. Evidence of a corrosive environment would include staining, residue, a wetted location, or rust bloom.
If a corrosive environment is identified, volumetric examination using ultrasonic testing will be used to confirm stress corrosion cracking of the high strength bolting is not present. A one-time volumetric examination will be used on 20 percent or a maximum of 25 samples of such connections to confirm SCC is not present.
NRC: How do you know past events have not exposed the high strength bolting material to a corrosive environment?
FENOC: A visual inspection of the bolting in this population would identify if a corrosive environment would have existed in the history of the connection. This inspection will look to see if the coating is intact; it is not intended to disassemble the joint if the coating is intact. The bolting coating is expected to be found in the same condition as the original installation.
NRC: Will the visual inspection include 100% of the A540 high strength bolting with yield strength greater than 150ksi?
FENOC: Yes.
NRC: Was Molybdenum Disulfide (MoS2) used as a lubricant during the original installation of this high strength bolting material? How do you know the constructor did not use MoS2? Without confirmatory volumetric inspections and if MoS2 was used, it is possible SCC could occur. Please include the number of A540 high strength bolts in the RAI response.
FENOC: The site will check to determine whether MoS2 was used during installation.
The installation specification did not require MoS2. The installation specification for Hilti 1 expansion anchors did use MoS2 but these are not high strength bolting.
NRC: In the RAI response, FENOC must provide the definition of a corrosive environment and discuss how the bolting is susceptible to the environment. If the bolting is constantly susceptible, define the sample size for volumetric testing and frequency of testing. If the bolting experiences a one-time event, it is understood a volumetric inspection will be performed to confirm SCC has not occurred. The response should
3 define the follow-up frequency for volumetric testing after a one-time event has occurred.
The reviewer will have a discussion with NRC Engineering Division to determine how fast SCC would progress.
FENOC: The definition of a corrosive environment will be included in the response. The sample size for constantly susceptible bolting is intended to be 20 percent of the population, not to exceed 25 inspections. Volumetric inspections using ultrasonic inspection would be limited to a depth of 12 inches. The recommended frequency of repeat volumetric inspections, if necessary, is a 5-year periodic frequency for conditions constantly susceptible to corrosive environment. For event-driven inspections, the volumetric inspection is intended to be repeated once after the one-time event has occurred; within a 5 year frequency. If the follow-up inspection is satisfactory, a return to monitoring by the visual inspection plan would occur.
In a follow-up conference call on December 19, 2012 (NRC attendees were Sam Cuadrado de Jesús and Bill Holston; FENOC attendees were Trent Henline, Jake Hofelich, Allen McAllister and Larry Hinkle), FENOC agreed to include the following into the RAI response.
A review of both Davis-Besse specific and industry generic Operating Experience for A540 bolting has not identified a history of failures related to Stress Corrosion Cracking.
Molybdenum Disulfide (MoS2) was not required, nor prohibited, for any of the bolts in the structural bolting population during installation.
Davis-Besse has an extensive history of volumetric examinations of the Reactor Head Closure Studs (RHCS). The RHCS material is SA-540, Grade B-23. These studs also have a measured yield strength greater than 150 ksi, falling into a range of 151 to 159 ksi. One hundred percent of the RHCS population has been subject to volumetric examination each ten year inservice inspection interval, with no evidence of SCC identified. Davis-Besse concludes that reasonable assurance of structural integrity exists such that performing a threshold visual inspection of all bolts to determine the potential volumetric examination population is warranted.
Also, volumetric examinations will be performed no later than the subsequent refueling outage following visual identification of bolting subject to a corrosive environment.
Deferral of volumetric examinations to the subsequent refueling outage is not permitted if the visual inspection indicates evidence of contaminant penetration through the coatings.
In addition, it was agreed that an exception to the recommended Structures Monitoring Program defined in NUREG-1801, Generic Aging Lessons Learned (GALL) Report, Revision 2 is not required. Use of visual inspection in lieu of volumetric examination will be documented as an enhancement to the Davis-Besse Structures Monitoring Program and the enhancement will be included as a commitment in the Updated Safety Analysis Report (USAR) Supplement.
There was no further discussion, and the call was concluded.