[Federal Register Volume 71, Number 89 (Tuesday, May 9, 2006)]
[Notices]
[Pages 27010-27012]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E6-7000]


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NUCLEAR REGULATORY COMMISSION


Proposed 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 Comment

AGENCY: Nuclear Regulatory Commission.

ACTION: Solicitation of public comment.

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SUMMARY: The Nuclear Regulatory Commission (NRC) is soliciting public 
comment on its Proposed License Renewal Interim Staff Guidance LR-ISG-
2006-01. This LR-ISG proposes that applicants for license renewal for a 
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 rule and 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 to 
incorporate the comments, as appropriate. Once the NRC staff completes 
the LR-ISG, it will issue the LR-ISG for NRC and industry use. The NRC 
staff will also incorporate the approved LR-ISG into the next

[[Page 27011]]

revision of the license renewal guidance documents.

DATES: Comments may be submitted by June 8, 2006. Comments received 
after this date will be 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 [email protected]. 
The NRC maintains an Agencywide Documents Access and Management System 
(ADAMS), which provides text and image files of NRC's public documents. 
These documents may be accessed through the NRC's Public Electronic 
Reading Room on the Internet at http://www.nrc.gov/reading-rm/adams.html. Persons who do not have access 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 [email protected].

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 
[email protected].

SUPPLEMENTARY INFORMATION: Attachment 1 to this Federal Register 
notice, entitled Staff Position and Rationale for the Proposed 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 contains the NRC staff's rationale 
for publishing the proposed LR-ISG-2006-01. Attachment 2 to this 
Federal Register notice, entitled Proposed 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, contains the guidance for developing the 
plant-specific aging management program. The NRC staff is issuing this 
notice to solicit public comments on the proposed LR-ISG-2006-01. After 
the NRC staff considers any public comments, it will make a 
determination regarding the proposed LR-ISG.

    Dated at Rockville, Maryland, this 3rd day of May 2006.

    For the Nuclear Regulatory Commission.
Pao-Tsin Kuo,
Deputy Director, Division of License Renewal, Office of Nuclear Reactor 
Regulation.

Attachment 1--Staff Position and Rationale for the Proposed 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

Staff Position

    The NRC staff determined that applicants for license renewal for a 
plant with a boiling water reactor Mark I steel containment should 
provide a plant-specific aging management program (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.

Rationale

    The current license renewal guidance documents (LRGDs) do not 
provide sufficient guidance 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 license renewal 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 the applicants. Specifically, the staff has determined 
that applicants for license renewal for a plant with 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 renewal that is subject to aging degradation. Pursuant 
to 10 CFR 54.21, the applicant must 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.

Attachment 2--Proposed 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

Introduction

    Line Item II.B1.1-2 of NUREG-1801, Volume 2, Revision 1, includes a 
provision for aging management 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 Background

    Information 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 Nuclear Generating 
Station. IN 86-99, Supplement 1, dated February 1991, explained that 
the most likely 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 noted that ultrasonic testing (UT) discovered 
minor corrosion in the cylindrical portion of the drywell.

Discussion

    Generic Letter (GL) 87-05, ``Request for Additional Information-
Assessment

[[Page 27012]]

of Licensee Measures 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 UT of 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 drywell shell 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-year operating 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 is subject to aging degradation. Pursuant 
to 10 CFR 54.21, the applicant must 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.
    On the basis of license renewal application reviews and industry 
operating experience, the NRC staff 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 Action

    In addressing Line Item II.B1.1-2 of NUREG-1801, Volume 2, Revision 
1, applicants for license renewal 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 consider the following:
    (1) Develop a corrosion rate that can be reasonably inferred from 
past UT examinations or establish 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 
shell will have sufficient wall thickness to perform its intended 
function through the period of extended operation.
    (2) Demonstrate that UT measurements performed in response to GL 
87-05 did not show degradation inconsistent with the developed or 
established corrosion rate.
    (3) Where degradation has been identified in the accessible areas 
of the drywell, provide an evaluation 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 of the drywell shell:
    (a) Include in the scope of license renewal any components that are 
identified as a source of moisture, such as the refueling seal, and 
perform an aging management review.
    (b) Identify surface areas requiring examination by implementing 
augmented inspections 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 thinning using an ultrasonic thickness measurement method,
    (iii) When ultrasonic thickness measurements are performed, one-
foot square grids shall 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 with ASME Section XI IWE that corrosion is not occurring or 
that corrosion is progressing so slowly that the age-related 
degradation will not jeopardize the intended 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 of extended 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 ensure that 
the integrity of the drywell shell will be maintained through the 
period of extended operation.

[FR Doc. E6-7000 Filed 5-8-06; 8:45 am]
BILLING CODE 7590-01-P