ML061120003
| ML061120003 | |
| Person / Time | |
|---|---|
| Site: | PROJ0690 |
| Issue date: | 05/03/2006 |
| From: | Kuo P NRC/NRR/ADRO/DLR/RLRB |
| To: | Lochbaum D, Marion A Nuclear Energy Institute, Union of Concerned Scientists |
| tran, l., NRR/DLR/RLRB, 415-4103 | |
| Shared Package | |
| ML061120001 | List: |
| References | |
| %dam200606, LR-ISG-2006-01 | |
| Download: ML061120003 (10) | |
Text
7590-01-PNUCLEAR REGULATORY COMMISSIONProposed License Renewal Interim Staff Guidance LR-ISG-2006-01: Plant-specific Aging Management Program for Inaccessible Areas of Boiling Water Reactor Mark I Steel Containment Drywell Shell Solicitation of Public CommentAGENCY:Nuclear Regulatory Commission (NRC)ACTION:Solicitation of public comment
SUMMARY
- The NRC is soliciting public comment on its Proposed License Renewal InterimStaff Guidance LR-ISG-2006-01. This LR-ISG proposes that applicants for license renewal fora plant with a boiling water reactor Mark I steel containment provide a plant-specific aging management program that addresses the potential loss of material due to corrosion in the inaccessible areas of their Mark I steel containment drywell shell for the period of extended operation.
The NRC staff issues LR-ISGs to facilitate timely implementation of the license renewal ruleand to review activities associated with a license renewal application (LRA). Upon receiving public comments, the NRC staff will evaluate the comments and make a determination toincorporate the comments, as appropriate. Once the NRC staff completes the LR-ISG, it willissue the LR-ISG for NRC and industry use. The NRC staff will also incorporate the approvedLR-ISG into the next revision of the license renewal guidance documents.
DATES: Comments may be submitted by June 8, 2006. Comments received after this date willbe considered, if it is practical to do so, but the Commission is able to ensure consideration only for comments received on or before this date.
ADDRESSES: Comments may be submitted to: Chief, Rules and Directives Branch, Office of Administration, U.S. Nuclear Regulatory Commission, Washington, DC, 20555-0001. Comments should be delivered to: 11545 Rockville Pike, Rockville, Maryland, Room T-6D59,between 7:30 a.m. and 4:15 p.m. on Federal workdays. Persons may also provide comments via e-mail at LNT@NRC.GOV. The NRC maintains an Agencywide Documents Access andManagement System (ADAMS), which provides text and image files of NRC's publicdocuments. These documents may be accessed through the NRC's Public Electronic ReadingRoom on the Internet at http://www.nrc.gov/reading-rm/adams.html. Persons who do not haveaccess to ADAMS or who encounter problems in accessing the documents located in ADAMS should contact the NRC Public Document Room (PDR) reference staff at 1-800-397-4209, 301-415-4737, or by e-mail at pdr@nrc.gov
.FOR FURTHER INFORMATION CONTACT: Ms. Linh Tran, License Renewal Project Manager, Office of Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission, Washington, DC, 20555-0001; telephone 301-415-4103 or e-mail lnt@nrc.gov
.SUPPLEMENTARY INFORMATION: Attachment 1 to this Federal Register notice, entitledStaff Position and Rationale for the Proposed License Renewal Interim Staff Guidance LR-ISG-2006-01: Plant-specific Aging Management Program for Inaccessible Areas of BoilingWater Reactor Mark I Steel Containment Drywell Shell contains the NRC staff's rationale forpublishing the proposed LR-ISG-2006-01. Attachment 2 to this Federal Register notice, entitledProposed License Renewal Interim Staff Guidance LR-ISG-2006-01: Plant-specific Aging Management Program for Inaccessible Areas of Boiling Water Reactor Mark I SteelContainment Drywell Shell, contains the guidance for developing the plant-specific aging management program. The NRC staff is issuing this notice to solicit public comments on theproposed LR-ISG-2006-01. After the NRC staff considers any public comments, it will make adetermination regarding the proposed LR-ISG.Dated at Rockville, Maryland, this 3 rd day of May 2006.FOR THE NUCLEAR REGULATORY COMMISSION/RA/Pao-Tsin Kuo, Deputy DirectorDivision of License Renewal Office of Nuclear Reactor Regulation STAFF POSITION AND RATIONALE FOR THEPROPOSED LICENSE RENEWAL INTERIM STAFF GUIDANCE LR-ISG-2006-01:PLANT-SPECIFIC AGING MANAGEMENT PROGRAM FOR INACCESSIBLE AREAS OFBOILING WATER REACTOR MARK I STEEL CONTAINMENT DRYWELL SHELL STAFF POSITION
- The NRC staff determined that applicants for license renewal for a plant with a boilingwater reactor Mark I steel containment should provide a plant-specific aging management program (AMP) that address the potential loss of material due to corrosion in the inaccessible areas of the Mark I steel containment drywell shell for the period of extended operation.RATIONALE:The current license renewal guidance documents (LRGDs) do not provide sufficientguidance to address inaccessible areas of the Mark I steel containment drywell shell.
Specifically, additional guidance is needed for inaccessible areas where the distance between the drywell shell and the surrounding concrete structure is too small for the successful performance of visual inspection. Past operating experience with Mark I steel containments indicates that when water is discovered in the bottom outside areas of the drywell (for example in the sand-pocket area), the most likely cause is the seepage through the space between the drywell shell and the shield concrete.Numerous requests for additional information (RAIs) on previous and current licenserenewal applications (LRAs) have been needed to obtain the information needed by the staff to perform its review. The purpose of the proposed LR-ISG-2006-01 is to provide guidance on the information that should be provided in the LRA to reduce the number of RAIs issued to theapplicants. Specifically, the staff has determined that applicants for license renewal for a plantwith a boiling water reactor Mark I steel containment should provide a plant-specific AMP to address the potential loss of material due to corrosion in the inaccessible areas of the Mark I steel containment drywell shell for the period of extended operation.The drywell shell is a passive, long-lived structure within the scope of license renewalthat is subject to aging degradation. Pursuant to 10 CFR 54.21, the applicant must demonstratethat the effects of aging will be adequately managed so that the intended function will bemaintained consistent with the current licensing basis for the period of extended operation. PROPOSED LICENSE RENEWAL INTERIM STAFF GUIDANCE LR-ISG-2006-01:
PLANT-SPECIFIC AGING MANAGEMENT PROGRAM FOR INACCESSIBLE AREAS OFBOILING WATER REACTOR MARK I STEEL CONTAINMENT DRYWELL SHELL IntroductionLine Item II.B1.1-2 of NUREG-1801, Volume 2, Revision 1, includes a provision for agingmanagement of the Mark I steel containment drywell shells. However, the line item requires additional detail to address the inaccessible areas of the Mark I steel containment drywell shells. Specifically, the line item does not provide guidance when the distance between the steel drywell shell and the surrounding concrete structure is too small for the successful performance of visual examination.All Mark I containments are free-standing steel construction, except for Brunswick, Units 1 and 2.The Brunswick Mark I containment is a reinforced concrete drywell with a steel liner. A drywell shell is a free-standing steel structure with no concrete backing, whereas the steel liner of a drywell is a leak-tight membrane in direct contact with the concrete containment. Historical BackgroundInformation Notice (IN) 86-99, "Degradation of Steel Containments," dated December 8, 1986,described an event related to the degradation of the drywell shell at Oyster Creek NuclearGenerating Station. IN 86-99, Supplement 1, dated February 1991, explained that the mostlikely cause of corrosion of the drywell shell in sand-pocket areas (near the bottom of the drywell) and in the spherical portion of the drywell at higher elevations, was the water in the gap between the drywell and the concrete shield. The source of water was noted as leakage through the seal between the drywell and the refueling cavity. The IN supplement also notedthat ultrasonic testing (UT) discovered minor corrosion in the cylindrical portion of the drywell. DiscussionGeneric Letter (GL) 87-05, "Request for Additional Information-Assessment of LicenseeMeasures to Mitigate And/Or Identify Potential Degradation of Mark I Drywells," requested additional information regarding licensee actions to mitigate and/or identify potential degradation of boiling water reactor Mark I drywells. As a result, most licensees performed UTof their carbon steel drywell shells adjacent to the sand pocket region. In addition, many licensees established leakage monitoring programs for drain lines to identify leakage that may have resulted from refueling or spillage of water into the gap between the drywell and the surrounding concrete.UT performed as a result of GL 87-05 provided a set of data points to determine the drywellshell thickness that could be compared to the nominal/minimum fabrication thickness and the minimum thickness required to withstand the postulated loads. These UT measurements taken during the 1987-1988 time frame fall approximately near the mid-point of the current 40-yearoperating license period for most plants with Mark I steel containments. The drywell shell is a passive, long-lived structure within the scope of license renewal that issubject to aging degradation. Pursuant to 10 CFR 54.21, the applicant must demonstrate thatthe effects of aging will be adequately managed so that the intended function will be maintainedconsistent with the current licensing basis for the period of extended operation. On the basis of license renewal application reviews and industry operating experience, the NRCstaff determined that a plant-specific aging management program (AMP) is needed to address the potential loss of material due to corrosion in the inaccessible areas of the Mark I steel containment drywell shell for the period of extended operation.Proposed ActionIn addressing Line Item II.B1.1-2 of NUREG-1801, Volume 2, Revision 1, applicants for licenserenewal for plants with a Mark I steel containment need to provide a plant-specific AMP that addresses the potential loss of material due to corrosion in the inaccessible areas of the Mark I steel containment drywell shell for the period of extended operation.In conducting the aging management review of the drywell shell, the applicant should considerthe following:(1)Develop a corrosion rate that can be reasonably inferred from past UT examinations orestablish a corrosion rate using representative samples in similar operating conditions, materials, and environments. If degradation has occurred, provide a technical basis using the developed or established corrosion rate to demonstrate that the drywell shellwill have sufficient wall thickness to perform its intended function through the period ofextended operation.(2)Demonstrate that UT measurements performed in response to GL 87-05 did not showdegradation inconsistent with the developed or established corrosion rate. (3)Where degradation has been identified in the accessible areas of the drywell, provide anevaluation that addresses the condition of the inaccessible areas for similar conditions.(4)To assure that there are no circumstances that would result in degradation of the drywell,demonstrate that moisture levels associated with accelerated corrosion rates do not exist in the exterior portion of the drywell shell, i.e., (1) the sand pocket area drains and/or the refueling seal drains are monitored periodically; (2) the top of the sand pocket area is sealed to exclude water accumulation in the sand pocket area; and/or alarms are used to monitor regions for moisture/leakage.(5)If moisture has been detected or suspected in the inaccessible area on the exterior ofthe drywell shell: (a)Include in the scope of license renewal any components that are identified as asource of moisture, such as the refueling seal, and perform an aging management review.(b)Identify surface areas requiring examination by implementing augmentedinspections for the period of extended operation in accordance with the American Society of Mechanical Engineers (ASME)Section XI IWE-1240 as identified in Table IWE-2500-1, Examination Category E-C.(c) Use examination methods, that are in accordance with ASME Section XI IWE-2500,which specifies: (i) surface areas accessible from both sides shall be visually examined using a VT-1 visual examination method,(ii)surface areas accessible from one side only shall be examined for wall thinningusing an ultrasonic thickness measurement method,(iii)when ultrasonic thickness measurements are performed, one foot square gridsshall be used, and(iv) ultrasonic measurements shall be used to determine the minimum wall thickness within each grid. The location of the minimum wall thickness shall be marked such that periodic reexamination of that location can be performed.(d)Demonstrate through use of augmented inspections performed in accordance withASME Section XI IWE that corrosion is not occurring or that corrosion is progressing so slowly that the age-related degradation will not jeopardize theintended function of the drywell shell through the period of extended operation.(6)If the intended function of the drywell shell cannot be demonstrated for the period ofextended operation (i.e., wall thickness is less than the minimum required thickness),
identify actions that will be taken as part of the aging management program to ensurethat the integrity of the drywell shell will be maintained through the period of extendedoperation.