[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