[Federal Register Volume 68, Number 93 (Wednesday, May 14, 2003)]
[Notices]
[Pages 25909-25912]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 03-11960]


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NUCLEAR REGULATORY COMMISSION


Proposed Generic Communication; Requirements for Steam Generator 
Tube Inspections

AGENCY: Nuclear Regulatory Commission.

ACTION: Notice of opportunity for public comment.

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SUMMARY: The U.S. Nuclear Regulatory Commission (NRC) is proposing to 
issue a generic letter (GL) to (1) advise all holders of operating 
licenses for pressurized-water reactors (PWRs), except those who have 
permanently ceased operations and have certified that fuel has been 
permanently removed from the reactor vessel, that the NRC's 
interpretation of technical specification (TS) requirements in 
conjunction with Appendix B to part 50 of title 10 of the Code of 
Federal Regulations (10 CFR part 50) raises questions as to whether 
steam generator (SG) tube inspection practices ensure compliance with 
these requirements, (2) request that addressees submit a description of 
the tube inspections performed at their plants, including an assessment 
of whether these inspections ensure compliance with the requirements 
contained in their TS in conjunction with 10 CFR part 50, Appendix B, 
(3) request that addressees propose plans for coming into compliance 
with these requirements if they conclude they are not in compliance, 
and (4) request that addressees submit a safety assessment addressing 
any differences from the NRC's position regarding these requirements. 
The NRC is seeking comment from interested parties on the clarity and 
utility of the proposed GL under the SUPPLEMENTARY INFORMATION heading. 
The NRC will consider the comments received in its final evaluation of 
the proposed GL.
    This Federal Register notice is available through the NRC's 
Agencywide Documents Access and Management System (ADAMS) under 
accession number ML031270171.

DATES: Comment period expires July 14, 2003. Comments submitted after 
this date will be considered if it is practical to do so, but assurance 
of consideration cannot be given except for comments received on or 
before this date.

ADDRESSES: Submit written comments to the Chief, Rules and Directives 
Branch, Division of Administrative Services, Office of Administration, 
U.S. Nuclear Regulatory Commission, Mail Stop T6-D59, Washington, DC 
20555-0001, and cite the publication date and page number of this 
Federal Register notice. Written comments may also be delivered to NRC 
Headquarters, 11545 Rockville Pike (Room T-6D59), Rockville, Maryland, 
between 7:30 a.m. and 4:15 p.m. on Federal workdays.

FOR FURTHER INFORMATION CONTACT: Paul Klein at (301) 415-4030 or by E-
mail to [email protected].

SUPPLEMENTARY INFORMATION:

NRC Generic Letter 2003-XX: Requirements for Steam Generator Tube 
Inspections

Addressees

    All holders of operating licenses for pressurized-water reactors 
(PWRs), except those who have permanently ceased operations and have 
certified that fuel has been permanently removed from the reactor 
vessel.

Purpose

    The U.S. Nuclear Regulatory Commission (NRC) is issuing this 
generic letter to
    (1) Advise addressees that the NRC's interpretation of the 
technical specification (TS) requirements in conjunction with 10 CFR 
part 50, Appendix B, raises questions whether certain licensee steam 
generator (SG) tube inspection practices ensure compliance with these 
requirements,
    (2) Request that addressees submit a description of the tube 
inspections performed at their plants, including an assessment of 
whether these inspections ensure compliance with the requirements 
contained in their TS in conjunction with 10 CFR part 50, Appendix B,
    (3) Request that addressees that conclude they are not in 
compliance with the SG tube inspection requirements contained in their 
TS in conjunction with 10 CFR part 50, Appendix B, propose plans for 
coming into compliance with these requirements, and
    (4) Request that addressees submit a safety assessment that 
addresses any differences from the NRC's position regarding the 
requirements of the TS in conjunction with 10 CFR part 50, Appendix B.

Background

    Steam generator tubes function as an integral part of the reactor 
coolant pressure boundary (RCPB) and, in addition, serve to isolate 
radiological fission products in the primary coolant from the secondary 
coolant and the environment. For the purposes of this generic letter, 
tube integrity means that the tubes are capable of performing these 
functions in accordance with the plant licensing basis, including 
applicable regulatory requirements.
    Title 10 of the Code of Federal Regulations (10 CFR) establishes 
the fundamental regulatory requirements with respect to the integrity 
of the SG tubing. Specifically, the general design criteria (GDC) in 
Appendix A to 10 CFR part 50 state that the RCPB shall be ``designed, 
fabricated, erected, and tested so as to have an extremely low 
probability of abnormal leakage * * * and of gross rupture'' (GDC 14), 
``designed, fabricated, erected, and tested to the highest quality 
standards practical'' (GDC 30), and ``designed to permit periodic 
inspection and testing * * * to assess * * * structural and leaktight 
integrity'' (GDC 32). (There are similar requirements in the licensing 
basis for plants licensed prior to 10 CFR part 50, Appendix A.)
    Given the importance of SG tube integrity, all current PWR 
licensees have TS governing the surveillance of SG tubes. These TS 
typically do not prescribe non-destructive test methods for conducting 
tube inspections or specify where a particular methodology should be 
used. For example, current TS may employ the following or similar 
nonspecific language:

    Tube inspection for tubes selected in accordance with Table 
[xxxx] means an inspection of the steam generator tube from the 
point of entry (hot leg side) completely around the U-bend to the 
top support of the cold leg, excluding sleeved areas.


[[Page 25910]]


    The surveillance requirements do, however, specify acceptance 
limits for SG tubes (often called plugging or repair limits). The 
surveillance requirements seek to ensure that enough information is 
obtained about imperfections (flaws) in the tubes to determine if TS 
plugging limits are being met. Tube imperfections are defined in the TS 
and include circumferential and axial cracks.
    SG tube inspections are also subject to the quality assurance 
requirements of 10 CFR part 50, Appendix B. Specifically, SG tube 
inspections must be performed in accordance with Criterion IX of 10 CFR 
part 50, Appendix B, which requires that ``measures shall be 
established to assure that special processes, including welding, heat 
treating, and nondestructive testing, are controlled and accomplished 
by qualified personnel using qualified procedures in accordance with 
applicable codes, standards, specifications, criteria, and other 
special requirements.''
    Licensees currently employ an eddy current test bobbin probe, at 
least, to inspect the entire length of tubing required by the TS. The 
bobbin probe is a high-speed probe which the industry has demonstrated 
to be qualified for and capable of detecting volumetric flaws and 
axially oriented cracks in the absence of significant masking signals. 
Masking signals may be produced by tube geometry variations or 
irregularities along the tube axis (such as small-radius U-bends, dents 
and dings, and expansion transitions) or by tube surface 
irregularities. Masking signals can also be produced by deposits on the 
tube surface, adjacent support structures (such as the tubesheet), 
probe wobble, cold working, permeability variations, or electrical 
noise.
    While the bobbin probe generally provides an effective means of SG 
tube inspection over much of the tube length, experience has shown that 
the bobbin probe may not be effective at locations where significant 
masking signals are present. In addition, the bobbin probe generally 
cannot detect circumferential cracks. Circumferential cracks can occur 
at locations of high axial stress (e.g., small-radius U-bends and the 
tubesheet expansion region).
    Plant TS for virtually all PWRs require inspection of the entire 
length of hot leg tubing within the tubesheet. With some exceptions 
where specified in the plant TS, the acceptance limits (plugging 
limits) for these inspections apply to all imperfections along the full 
length of the tube in the tubesheet on the hot leg side, including 
axial and circumferential cracks. Criterion IX, ``Control of Special 
Processes,'' of 10 CFR part 50, Appendix B, requires in part that 
nondestructive testing is to be accomplished by qualified personnel 
using qualified procedures in accordance with applicable criteria. The 
bobbin probe has not been qualified for and is not capable of reliably 
detecting axial or circumferential cracks in the expanded region of 
tubing inside the tubesheet; however, specialized probes are available 
which have been qualified for this application.
    As a result of these limitations, the industry practice is to 
supplement the bobbin probe inspection with inspections by specialized 
probes, such as the rotating pancake coil or plus point probe, that are 
qualified for and capable of detecting degradation that is not 
detectable with the bobbin probe. However, inspecting tubes with these 
specialized probes is slower than with the bobbin probe. Therefore, 
these slow-speed probes are typically not applied over the entire 
length of a tube that is subject to inspection, but only at tube 
locations where degradation which cannot be detected with the bobbin 
probe (e.g., circumferential cracks, axial cracks in U-bends and 
expansion transitions) is known to be present or considered to have a 
potential to occur. This practice involves a degree of engineering 
judgment to determine the locations in which potential degradation 
mechanisms may exist that could lead to degradation that is not 
detectable using a bobbin probe. The EPRI Steam Generator Examination 
Guidelines provide guidance on assessing the potential for degradation 
to occur at various locations.
    In 2002, the staff learned of several instances in which licensees 
were not fully implementing inspection methods capable of detecting 
circumferentially oriented cracks at all locations where the potential 
for such cracks exists and where, based on available evidence, there is 
reason to believe such cracks may be present. These licensees were 
conducting full-length bobbin probe inspections of the tubes, and were 
performing additional inspections using specialized probes to inspect 
for axial and circumferential cracks at certain locations, including 
the tube expansion transitions near the top of the tubesheet. The 
licensees conducted the specialized probe inspections at the tube 
expansion transitions in an area that extended from 2 inches above the 
top of the tubesheet to about 5 inches below the top of the tubesheet. 
At several facilities, circumferential cracks were identified at tube 
expansion transitions, as well as below the transitions near the bottom 
of the zone being inspected. These results indicate a potential for 
circumferential cracks to exist in the tubing below the zone inspected 
with the specialized probe. However, each licensee also performed an 
analysis indicating that circumferential cracks below the zone being 
inspected would not be detrimental to tube structural and leakage 
integrity. These licensees concluded, therefore, that inspections for 
circumferential cracks with the specialized probe were unnecessary 
below the zone already inspected with the probe. These analyses had not 
been provided to the NRC staff.
    The staff became aware of these activities during the licensees' SG 
inspections conducted during refueling outages and asked the licensees 
to submit TS amendment requests or safety analyses to obtain NRC 
approval of their inspection approaches. The staff reviewed the 
resulting submittals on a one-cycle basis before the plants restarted. 
Subsequent to these plant-specific actions, the staff evaluated the 
appropriate method to interact with licensees on this issue. Given the 
potentially generic nature of the issue, the staff decided to 
communicate this issue to addressees through issuance of this generic 
letter.

Discussion

    In the aforementioned instances, tube inspections with a 
specialized probe near the top of the tubesheet clearly indicated the 
potential for circumferential cracks to occur deeper into the tubesheet 
beyond the region inspected with the specialized probes. In each 
instance the licensee was aware of the potential for such cracks to 
exist deeper into the tubesheet, but the licensee did not employ 
techniques qualified for detecting such cracks based on the licensee's 
analysis that such cracks did not have safety implications.
    The staff acknowledges that there may be circumstances under which 
certain flaws at certain locations may not pose a safety concern. 
However, it is the staff's position that pending the submission of a 
license amendment request clarifying the acceptability of a more 
limited inspection approach, licensees are required under existing 
requirements (TS in conjunction with 10 CFR part 50, Appendix B) to 
employ inspection techniques capable of detecting all flaw types which 
may potentially be present at locations which are required to be 
inspected pursuant to the TS. The staff is concerned that in instances 
similar to those cited above, failure to expand the scope of the 
specialized probe inspection deeper into the tubesheet to detect cracks 
likely to be present poses a potential compliance issue with

[[Page 25911]]

respect to the plant TS in conjunction with 10 CFR part 50, Appendix B.
    In addition, the staff notes that not inspecting for cracks with 
qualified procedures in the lower regions of the tubesheet would allow 
any such cracks to remain in place. However, most plant TS state that 
only tubes with imperfections less than 40 percent of the nominal tube 
wall thickness are acceptable for continued service (there are 
exceptions specified in some plant TS). While it is not known whether 
any such cracks actually exist, the staff notes that the acceptance or 
plugging limit for SG tube inspections is a specific technical 
specification limit that can only be changed through the license 
amendment process.
    Also, for the instances cited above, the safety basis developed by 
the licensees for not expanding the scope of the specialized probe 
inspection beyond a specific distance (x-inches) into the tubesheet was 
that any cracks below that distance were not detrimental to tube 
integrity. This was based on analyses indicating that tubes only needed 
a minimum embedment of x-inches into the tubesheet to exhibit 
acceptable structural and accident leakage integrity. These analyses 
have been performed to demonstrate that cracks below this embedment 
distance do not impair SG tube integrity, even if these cracks cause 
complete severance of the tube. According to plant final safety 
analysis reports (FSARs), the SGs were designed in accordance with 
section III of the American Society of Mechanical Engineers (ASME) 
Code. In accordance with section III of the Code, the original design 
basis pressure boundary for the tube-to-tubesheet joint included the 
tube and tubesheet extending down to and including the tube-to-
tubesheet weld. The criteria of section III of the ASME Code constitute 
the ``method of evaluation'' for the design basis. In the event 
licensees are using a different ``method of evaluation'' for assessing 
the steam generator pressure boundary, an evaluation under 10 CFR 50.59 
would determine whether a license amendment is required in these cases.
    In summary, for the cases discussed above, the TS required a tube 
inspection for the full length of the tube within the tubesheet 
(scope), and the findings from this inspection were required to be 
evaluated against a repair (plugging) criteria. Neither the scope nor 
the repair criteria in the TS contained provisions for limiting the 
inspections through a licensee controlled analysis.
    Based on these instances, the NRC cannot conclude that addressees 
that are using such an approach remain in compliance with their TS in 
conjunction with Criterion IX of 10 CFR part 50, Appendix B with regard 
to the inspections they are performing. This concern stems, in part, 
from the experience with some addressees relying on licensee controlled 
analyses to limit the scope and therefore the repair or plugging of 
defective SG tubes contrary to the requirements in the TS in 
conjunction with Criterion IX of 10 CFR part 50, Appendix B, which 
contains no provisions for limiting the inspections in this manner. It 
is the staff's position that pending a license amendment clarifying the 
inspection approach to be followed, licensees are required to employ 
inspection methods capable of detecting all flaw types which may 
potentially be present at locations which are required to be inspected 
pursuant to the TS, as set forth above.
    Based on these staff concerns, the NRC is issuing this generic 
letter, consistent with the requirements in 10 CFR 50.54(f) to obtain 
information necessary for the staff to determine if addressees are in 
compliance with the technical specifications in conjunction with 10 CFR 
part 50, Appendix B. In addition, licensees who have not been 
implementing inspections consistent with the staff's position should 
submit a safety assessment that demonstrates their ability to ensure 
continued safe operation and addresses any differences relative to the 
staff's position.
    For licensees that cannot demonstrate continued compliance with the 
TS in conjunction with 10 CFR part 50, Appendix B, owners group 
involvement in the development of standard or generic approaches to 
this issue, including TS and associated Bases wording, could be helpful 
from the standpoint of minimizing resource impacts for both licensees 
and the staff.

Requested Information

    Within 30 days of the date of this generic letter, addressees are 
requested to provide to the NRC the following information:
    1. Addressees should provide a description of the SG tube 
inspections performed at their plant during the last inspection. In 
addition, addressees should provide an assessment of how the tube 
inspections performed at their plant meet the requirements of the TS in 
conjunction with Criterion IX of 10 CFR part 50, Appendix B, if they 
are not using SG tube inspection methods with capabilities consistent 
with the NRC's position. This assessment should also address whether 
the tube inspection practices ensured that the tube plugging or repair 
limits were implemented for the entire length of tubing required to be 
inspected per the TS (i.e., discuss whether the techniques employed 
during the tube inspections ensured flaws could be detected such that 
the plugging or repair limits could be implemented).
    2. If addresses conclude that full compliance with the TS in 
conjunction with Criterion IX of 10 CFR part 50, Appendix B, requires 
corrective actions to be taken, they should discuss their proposed 
corrective actions (e.g., changing inspection practices consistent with 
the NRC's position, or submitting a TS amendment request with the 
associated safety basis for limiting the inspections). If addressees 
choose to change their TS, the staff has included in Attachment 1 
suggested changes to the TS definitions for a tube inspection and for 
plugging limits to show what may be acceptable to the staff in cases 
where the extent of the inspection in the tubesheet region is limited.
    3. For plants where SG tube inspections have not been or are not 
being performed consistent with the NRC's position on the requirements 
contained in the TS in conjunction with Criterion IX of 10 CFR part 50, 
Appendix B, the licensee should submit a safety assessment that 
addresses any differences relative to the NRC's position (i.e., submit 
the safety basis for not employing inspection methods capable of 
detecting specific flaw types at specific locations where these flaw 
types may potentially occur and where a tube inspection is required by 
the TS), and include an evaluation of whether this safety assessment 
constitutes a change to the ``method of evaluation'' (as defined in 10 
CFR 50.59) for establishing the structural and leakage integrity of the 
joint. Licensees should also determine whether a license amendment is 
necessary pursuant to 10 CFR 50.59.

Required Response

    In accordance with 10 CFR 50.54(f), addressees are required to 
submit written responses to this generic letter. Two options are 
available:
    (a) Addressees may choose to submit written responses providing the 
information requested above within the requested time period.
    (b) Addressees who cannot meet the requested completion date are 
required to notify the NRC in writing as soon as possible but no later 
than 30 days from the date of this generic letter. The responses must 
address any alternative course of action proposed, including the basis 
for the acceptability of the proposed alternative course of action, the 
basis for finding that the SGs remain

[[Page 25912]]

operable, and the schedule when the requested information will be 
submitted.
    The required written response should be addressed to the U.S. 
Nuclear Regulatory Commission, ATTN: Document Control Desk, 11555 
Rockville Pike, Rockville, Maryland 20852, under oath or affirmation 
under the provisions of section 182a of the Atomic Energy Act of 1954, 
as amended, and 10 CFR 50.54(f). In addition, submit a copy of the 
response to the appropriate regional administrator.

Reasons for Requested Information

    This generic letter requests that addressees submit information. 
The requested information will enable the NRC staff to make a 
determination as to whether licensees are implementing SG tube 
inspections in accordance with applicable requirements. In cases where 
licensees are not implementing inspections in such a manner, the 
requested information will allow the staff to make a determination as 
to the adequacy of the licensee's inspection program and compliance of 
the licensee's program relative to existing requirements (the plant TS 
in conjunction with 10 CFR part 50, Appendix B).

Backfit Discussion

    Under the provisions of section 182a of the Atomic Energy Act of 
1954, as amended, and 10 CFR 50.54(f), this generic letter transmits an 
information request for the purpose of verifying compliance with 
applicable existing requirements. Specifically, the requested 
information will enable the NRC staff to determine whether applicable 
requirements (plant TS in conjunction with 10 CFR part 50, Appendix B) 
are being met. No backfit is either intended or approved in the context 
of issuance of this generic letter. Therefore, the staff has not 
performed a backfit analysis.

Federal Register Notification

    To be done after the public comment period.

Paperwork Reduction Act Statement

    This generic letter contains information collections that are 
subject to the Paperwork Reduction Act of 1995 (44 U.S.C. 3501 et 
seq.). These information collections were approved by the Office of 
Management and Budget (OMB), control number 3150-0011, which expires on 
January 31, 2004.
    The burden to the public for these information collections is 
estimated to average 60 hours per response, including the time for 
reviewing instructions, searching existing data sources, gathering and 
maintaining the data needed, and completing and reviewing the 
collection of information. The U.S. Nuclear Regulatory Commission is 
seeking public comment on the potential impact of the collection of 
information contained in the generic letter and on the following 
issues:
    (1) Is the proposed collection of information necessary for the 
proper performance of the functions of the NRC, and will the 
information have practical utility?
    (2) Is the estimate of burden accurate?
    (3) Is there a way to enhance the quality, utility, and clarity of 
the information to be collected?
    (4) How can the burden of the collection of information be 
minimized? Can automated collection techniques be used?
    Send comments regarding this burden estimate or on any other aspect 
of these information collections, including suggestions for reducing 
the burden, to the Information and Records Management Branch (T-6 E6), 
U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by 
Internet electronic mail to [email protected]; and to the Desk 
Officer, Office of Information and Regulatory Affairs, NEOB-10202 
(3150-0011), Office of Management and Budget, Washington, DC 20503.
Public Protection Notification
    The NRC may not conduct or sponsor, and a person is not required to 
respond to, a collection of information unless it displays a currently 
valid OMB control number.
    If you have any questions about this matter, please contact one of 
the persons listed below or the appropriate Office of Nuclear Reactor 
Regulation (NRR) project manager.

Attachments: 1. Sample Changes to the TS for Plants Limiting 
Inspections in the Tubesheet Region

Attachment 1

Sample Changes to the TS for Plants Limiting Inspections in the 
Tubesheet Region

    Plugging Limit means the imperfection depth at or beyond which 
the tube shall be removed from service and is equal to 40% of the 
nominal tube wall thickness. All tubes with degradation in the 
portion of the tube from x-inches below the bottom of the expansion 
transition or the top of the tubesheet to the bottom of the 
expansion transition or the top of the tubesheet, whichever is 
lower, shall be removed from service.
    Tube Inspection means an inspection of the steam generator tube 
from x-inches below the hot-leg expansion transition or the top of 
tubesheet, whichever is lower, completely around the U-bend to the 
top support of the cold leg.
    Documents may be examined, and/or copied for a fee, at the NRC's 
Public Document Room at One White Flint North, 11555 Rockville Pike 
(first floor), Rockville, Maryland. Publicly available records will 
be accessible electronically from the Agencywide Documents Access 
and Management System (ADAMS) Public Electronic Reading Room on the 
Internet at the NRC Web site, http://www.nrc.gov/NRC/ADAMS/index.html. If you do not have access to ADAMS or if you have 
problems in accessing the documents in ADAMS, contact the NRC Public 
Document Room (PDR) reference staff at 1-800-397-4209 or 301-415-
4737 or by e-mail to [email protected].

    Dated in Rockville, Maryland, this 8th day of May, 2003.

    For the Nuclear Regulatory Commission.
William D. Beckner,
Program Director, Operating Reactor Improvements, Division of 
Regulatory Improvement Programs, Office of Nuclear Reactor Regulation.
[FR Doc. 03-11960 Filed 5-13-03; 8:45 am]
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