> Number range CHAPTER**NRC INSPECTION MANUAL** CPNB

TEMPORARY INSTRUCTION 2515/172

REACTOR COOLANT SYSTEM DISSIMILAR METAL BUTT WELDS

CORNERSTONE: Barrier Integrity

Initiating Events

APPLICABILITY: This temporary instruction (TI) applies to all holders of
operating

licenses for pressurized-water reactors (PWRs).

2515/172-01 OBJECTIVES

The objective of this TI is to:

> a\. Support NRC staff oversight of licensees' dissimilar metal butt
> weld (DMBW) mitigation and inspection activities that are being
> implemented in accordance with the industry guidelines of the
> Materials Reliability Program (MRP) ‑139, "Primary System Piping Butt
> Weld Inspection and Evaluation Guidelines," July 2005.
>
> b\. Verify that each pressurized water reactor (PWR) plant conforms to
> its commitments to conduct an inspection program consistent with the
> industry's MPR-139 guidelines.
>
> c\. Verify that mitigation techniques implemented by licensees are
> consistent with MRP-139 as discussed in the inspection requirements
> section of this TI.
>
> d\. Define and initiate information gathering so that NRC staff can
> identify and develop possible future regulatory positions, generic
> communications, and rulemaking in this area.

This TI pertains to primary system piping dissimilar metal butt welds 1"
NPS or larger, including**:**

> a\. pressurizer nozzle dissimilar metal butt welds (DMBWs).
>
> b\. DMBWs less than or equal to 14 inches exposed to temperatures
> equivalent to the hot leg.
>
> c\. DMBWs larger than 14 inches exposed to temperatures equivalent to
> the hot leg.
>
> d\. DMBWs exposed to temperatures equivalent to the cold leg.

MRP‑139 indicates that the initial or baseline volumetric inspections of
butt welds in these four sets of locations are to be completed in 2007,
2008, 2009, and 2010, respectively.

2515/172-02 BACKGROUND

Number range CHAPTEROperating experience has demonstrated that Alloy
600/82/182 materials exposed to primary coolant water (or steam) at the
normal operating conditions of PWR plants have cracked due to primary
water stress corrosion cracking (PWSCC). The NRC has issued several
bulletins and an order since 2001 related to the occurrence of PWSCC in
reactor coolant system components and welds containing Alloy 600/82/182.

Several methods have been used or are being considered by industry to
address PWSCC. These methods include increased frequency of inspection,
replacement of the Alloy 600/82/182 materials with Alloy 690/52/152
materials, structural weld overlays with Alloy 52/152 materials, stress
improvement processes that place the susceptible materials in
compression to prevent crack initiation and growth, and application of
Alloy 52 cladding on the inside surface of the susceptible Alloy 82/182
material.

Number range CHAPTERSection XI of the American Society of Mechanical
Engineers Boiler and Pressure Vessel Code (ASME Code), which is
incorporated into NRC regulations by 10 CFR 50.55a, \"Codes and
Standards,\" specifies examination requirements for reactor coolant
system components and piping, including DMBWs. Volumetric, surface, and
visual examinations are required to ensure the integrity of the reactor
coolant pressure boundary and safe operation of the plant.

In September 2005, NEI issued MRP-139, "Material Reliability Program:
Primary System Piping Butt Weld Inspection and Evaluation Guideline,"
with mandatory implementation for all PWRs under the industry's
proactive management of materials degradation initiative, NEI 03-08.
MRP-139 provides industry's guidance for the volumetric and visual
inspections of butt welds in PWR primary systems. The MRP-139
inspections augment examinations of these locations already required by
the ASME Code, Section XI. MRP-139 Section 1.2 on Implementation,
Section 5 on Examination Requirements, and Section 6 on Examination
Schedules were assigned the mandatory implementation category under NEI
03-08.

Based on recent experience with industry that arose from multiple flaws
found in pressurizer nozzle welds at Wolf Creek, the staff concluded
that it is essential that NRC staff monitor more closely the MRP-139
inspection programs and, in particular, the deviations utilities may be
planning to take from the guidelines stated in MRP-139. This TI contains
inspection and reporting requirements pertaining to deviations taken
from MRP‑139.

The NRC staff is relying on the industry MRP-139 program as a short term
approach for addressing PWSCC, but the NRC staff needs to verify that
each licensee has developed an inspection program and is implementing
its commitments to conduct the inspections in accordance with MRP-139.
As a long term approach for addressing PWSCC, the NRC staff is working
with the ASME Code to develop inspection requirements for dissimilar
metal butt welds. These Code inspection requirements will be contained
in an ASME code case that the NRC will endorse in its regulations if the
code case is found acceptable.

Number range CHAPTER2515/172-03 INSPECTION REQUIREMENTS

03.01 [Licensee's Implementation of the MRP-139 Baseline
Inspections.]{.underline}

Verify the following:

> a\. The licensee's inspection program includes inspections of the
> pressurizer, hot leg and cold leg temperature DMBWs and that the
> schedules for these baseline inspections are consistent with the
> requirements stated in MRP‑139. If any baseline inspection schedules
> deviate from MRP-139 guidelines, determine what deviations are planned
> and what is the general basis for the deviation.
>
> b\. The licensees (except for the nine plants specified below) have
> completed their MRP‑139 baseline inspections of all pressurizer DMBWs
> by December 31, 2007. For nine PWR plants (Braidwood Unit 2, Comanche
> Peak Unit 2, Diablo Canyon Unit 2, Palo Verde Unit 2, Seabrook, South
> Texas Station Unit 1, V.C. Summer, Vogtle Unit 1 and Waterford Unit
> 3), verify that the baseline pressurizer DMBWs are completed during
> the spring 2008 outages.

03.02 [Volumetric Examinations.]{.underline}

Licensees perform volumetric examinations as part of the
inspection/mitigation activities as described in MRP-139. Inspectors
should use Inspection Procedure (IP) 57080, "Ultrasonic Testing
Examination" and ASME Code Section XI, Appendix VIII, "Performance
Demonstrations for Ultrasonic Examination Systems" as guidance when
observing or reviewing the volumetric examinations performed by the
licensee. Perform the following inspections through either direct
observation (preferred method) or records review. If no examinations are
being performed during the current outage, perform a records review of
an examination during the previous outage.

> a\. Observe or review at least one examination of a weld (for example,
> an examination of a weld that is categorized as not being mitigated,
> an examination of a weld prior to mitigation by either weld overlay or
> mechanical stress improvement, or an examination of a weld after
> mitigation by mechanical stress improvement). Verify that the
> inspection is performed in accordance with the guidelines in MRP‑139,
> Section 5.1.
>
> b\. Observe or review at least one weld overlay volumetric
> examination. Verify that the inspection performed is consistent with
> the NRC staff relief request authorization for the weld overlay. If
> the inspection coverage warrants further evaluation, review the
> licensee's documentation of the basis for achieving the required
> inspection coverage.
>
> c\. Verify that the examinations were performed by qualified
> personnel.

d.  Verify that any deficiencies identified were appropriately
    dispositioned and resolved.

03.03 [Weld Overlays.]{.underline}

MRP-139 addresses inspection of dissimilar metal welds mitigated by weld
overlays as part of the strategy to address the DMBW issue. Inspectors
should use guidance contained in IP 55050, "Nuclear Welding General
Inspection Procedure," when performing their review of licensee's weld
overlay techniques. Perform the following inspections to verify that the
proper weld overlay techniques were used. If no examinations are being
performed during the current outage, perform a records review of an
examination during the previous outage.

> a\. For at least one weld overlay verify that the welding activities
> were performed consistent with ASME Code requirements as modified by
> NRC staff relief request authorizations.
>
> b\. Verify that the licensee has submitted a relief request and
> obtained NRR staff authorization to install the weld overlays, whether
> full structural or optimized weld overlays.
>
> c\. Verify that welding was performed by qualified personnel.
>
> d\. Verify that any deficiencies identified were appropriately
> dispositioned, and resolved.

03.04 [Mechanical Stress Improvement]{.underline}.

MRP-139 addresses inspection of dissimilar metal welds mitigated by
stress improvement (SI) as part of the strategy to address the DMBW
issue. For each application of SI used, inspectors should review the SI
qualification report that describes the essential parameters of the SI
process (e.g., the location radial loading is applied and the applied
load, as well as the inspection requirements). Inspectors should verify
the following for each location where SI was applied:

> a\. The nozzle, weld, safe end, and pipe configurations, as
> applicable, are consistent with the configuration addressed in the SI
> qualification report.
>
> b\. The SI qualification report addresses the location radial loading
> is applied, the applied load, and the effect that plastic deformation
> of the pipe configuration may have on the ability to conduct
> volumetric examinations.
>
> c\. The licensee's inspection procedure records document that a
> volumetric examination per the ASME Code, Section XI, Appendix VIII
> was performed [prior to and]{.underline} after the application of the
> SI.
>
> d\. The SI qualification report addresses limiting flaw sizes that may
> be found during pre‑SI and post‑SI inspections and that any flaws
> identified during the volumetric examination are to be within the
> limiting flaw sizes established by the SI qualification report.
>
> e\. Verify that any deficiencies identified were appropriately
> dispositioned, and resolved.

03.05 [Inservice Inspection Program.]{.underline}

MRP-139 contains industry mandatory requirements for baseline and
inservice inspection. In accordance with MRP-139, inservice inspections
are performed based on the categorization of the weld configuration,
which are classified as Categories A--I for volumetric examinations and
Categories J and K for visual examinations. The inspectors will perform
an inspection to verify that the licensee has prepared an MRP-139
inservice inspection program applicable welds are included in a category
consistent with MRP-139 guidelines. The inspectors will verify that the
licensee's inspection program and procedures specify inspection
frequencies consistent with Tables 6‑1 and 6-2 of MRP-139. The
inspectors will determine if any welds are categorized as H or I and
review the licensee's basis for the categorization and the licensee's
plans for addressing potential PWSCC. The inspector will determine if
any deviations are planned from the inspection guidelines in MRP‑139,
i.e., frequencies, examination volumes, methods.

Number range CHAPTER2515/172-04 GUIDANCE

Certain inspection requirements will have to take place during plant
outages when the activities occur. For inspection activities related to
programs and reports, it may be necessary to perform inspection onsite
during a non-outage period to obtain adequate support from the
licensee's staff. Additionally, if nondestructive testing performed at a
licensee's facility by an inspection vendor is not directly observed
(preferred method), a records review may require that portion of the
inspection be performed at the vendor's facility since the data may not
available at the plant.

04.01 [Licensee's Implementation of the MRP-139 Baseline
Inspections.]{.underline}

MRP-139 establishes an industry mandatory requirement for licensees to
complete baseline inspections of DMBWs in the reactor coolant system.
The licensee's baseline inspections may be performed on a number of
different weld configurations based on their MRP-139 categorization.
Regardless of licensee's plans to mitigate a particular weld, the
MRP‑139 baseline inspections must be performed using ASME, Section XI,
Appendix VIII, qualified methods.

MRP-139 Table 2-1 contains a listing of locations involving Alloy 82/182
piping butt welds in Westinghouse, Combustion Engineering and Babcox &
Wilcox design plants. This listing can be used to determine if the
licensee appropriately placed these DMBWs into the MRP-139 inspection
program. A complete listing of Alloy 82/182 welds should also be
contained in licensee documentation prepared in response to MRP-126.

It is the NRC staff's view that if the licensee plans to mitigate a weld
by a mechanical stress improvement, the licensee has to conduct a
pre-stress improvement inspection, and this pre-stress improvement
inspection is the MRP‑139 baseline inspection. This view is generally
consistent with the code case being prepared by ASME Section XI on
inspection of dissimilar metal butt welds.

There are nine plants scheduled to perform the pressurizer DMBW
inspections in the spring 2008 time frame. This schedule for inspection
of the pressurizer weld connections was the subject of extensive NRC
staff review and evaluation as documented in the NRC staff's safety
assessment on this issue which can be obtained in Agency Documents
Access and Management System (ADAMS) using accession number ML072400199.

04.02 [Volumetric Examinations.]{.underline}

Examination of a weld prior to application of a full structural weld
overlay (FSWO) is not required by either MRP-139 or the ASME code cases
pertaining to weld overlays. While such an examination is not required
to be performed prior to application of a FSWO, some licensees may
choose to perform this type of examination.

04.03 [Weld Overlays.]{.underline}

ASME Section XI does not presently contain inspection requirements for
weld overlays. Section XI has issued Code Cases N-504-3, "Alternative
Rules for Repair of Classes 1, 2, and 3 Austenitic Stainless Steel
Piping" and N-638-1, "Similar and Dissimilar Metal Welding Using Ambient
Temperature Machine GTAW Temper Bead Technique." These two code cases
are listed in Regulatory Guide (RG) 1.147, Revision 15, "Inservice
Inspection Code Case Acceptability, ASME Section XI, Division 1," with
limitations. Although these code cases are approved with limitations in
RG 1.147, their use for a weld overlay on an Alloy 82/182 weld requires
a relief request, since they were not written for this application. ASME
Section XI has issued N-740 and N-740-1, "Dissimilar Metal Weld Overlay
for Repair of Class 1, 2, and 3 Items," and is working on the second
revision to this code case. When the NRC staff approves code case
N‑740-X in RG 1.147 and endorses this regulatory guide in an update to
10 CFR 50.55a, application of weld overlays will no longer require NRR
approval through authorization of a relief request.

04.04 [Mechanical Stress Improvement]{.underline}.

Mechanical stress improvement is generally applied through a proprietary
process referred to as the Mechanical Stress Improvement Process or
MSIP™. This process was originally employed in the nuclear power
industry to boiling water reactor piping susceptible to intergranular
stress corrosion cracking. Each application of the process is expected
to be accompanied by a qualification report that documents the specific
stress improvement parameters to be applied to the weld, the basis for
the parameters, and the inspection requirements. While SI has been
through MSIP™ in the past, industry intends to also use what is referred
to as optimized weld overlays. Optimized weld overlays are not as thick
as full structural weld overlays, but are designed to obtain essentially
the same stress improvement benefits as an MSIP™. ASME Code, Section XI,
Appendix VIII volumetric examination must be performed [prior to
and]{.underline} after the application of stress improvement whether by
an MSIP™ or an optimized weld overlay.

04.05 [Inservice Inspection Program.]{.underline}

MRP-139 categorizes welds according to their mitigation status.
Mitigation techniques noted in MRP-139 are full structural weld overlays
and stress improvement. MRP-139 requires less frequent inspection of
welds that have been mitigated. These categories also relate to the
condition of the weld as cracked or uncracked. Categories H and I
pertain to welds for which a qualified ASME examination can not be
performed. NRR is aware of some welds for which a qualified examination
may not be possible without taking additional measures. Category H and I
welds may include welds joined to cast austenitic stainless steel
piping.

Number range CHAPTER2515/172-05 REPORTING REQUIREMENTS

Each refueling cycle for each unit document inspection results in
section 4OA5 of the routine resident inspectors' integrated inspection
report and send a copy of the inspection report to NRR/DCI, Attention:
Edmund Sullivan or e-mail the electronic file of the inspection report
to EJS@NRC.gov. In addition, forward the electronic file(s) that
documents the results of this TI to Mr. Edmund Sullivan when the TI is
completed. Mr. Sullivan can also be reached by telephone at (301)
415-2796.

The purpose of this TI is to support NRR/DCI by inspecting and reporting
on the licensees' performance on implementing MRP-139. Specifically, the
inspectors should provide a qualitative description of the effectiveness
of the licensees' DMBW inspection and mitigation program. As a minimum,
the inspectors shall document the following aspects in an inspection
report:

> a\. For MRP‑139 baseline inspections:
>
> 1\. Have the baseline inspections been performed or are they scheduled
> to be performed in accordance with MRP-139 guidance? Were the baseline
> inspections of the pressurizer temperature DMBWs of the nine plants
> listed in 03.01.b completed during the spring 2008 outages.
>
> 2\. Is the licensee planning to take any deviations from the MRP‑139
> baseline inspection requirements of MRP-139? If so, what deviations
> are planned and what is the general basis for the deviation? If
> inspectors determine that a licensee is planning to deviate from any
> MRP-139 baseline inspection requirements, NRR should be informed by
> email as soon as possible.
>
> b\. For each examination inspected, was the activity:
>
> 1\. Performed in accordance with the examination guidelines in MRP‑139
> Section 5.1 for unmitigated welds or mechanical stress improved welds
> and consistent with NRC staff relief request authorization for weld
> overlaid welds?
>
> 2\. Performed by qualified personnel? (Briefly describe the personnel
> training/qualification process used by the licensee for this
> activity.)
>
> 3\. Performed such that deficiencies were identified, dispositioned,
> and resolved?
>
> c\. For each weld overlay inspected, was the activity:
>
> 1\. Performed in accordance with ASME Code welding requirements and
> consistent with NRC staff relief requests authorizations? Has the
> licensee submitted a relief request and obtained NRR staff
> authorization to install the weld overlays?
>
> 2\. Performed by qualified personnel? (Briefly describe the personnel
> training/qualification process used by the licensee for this
> activity.)
>
> 3\. Performed such that deficiencies were identified, dispositioned,
> and resolved?
>
> d\. For each mechanical stress improvement used by the licensee during
> the outage, was the activity performed in accordance with a documented
> qualification report for stress improvement processes and in
> accordance with demonstrated procedures? Specifically,
>
> 1\. Are the nozzle, weld, safe end, and pipe configurations, as
> applicable, consistent with the configuration addressed in the SI
> qualification report?
>
> 2\. Does the SI qualification report address the location radial
> loading is applied, the applied load, and the effect that plastic
> deformation of the pipe configuration may have on the ability to
> conduct volumetric examinations?
>
> 3\. Do the licensee's inspection procedure records document that a
> volumetric examination per the ASME Code, Section XI, Appendix VIII
> was performed [prior to and]{.underline} after the application of the
> SI?
>
> 4\. Does the SI qualification report address limiting flaw sizes that
> may be found during pre‑SI and post‑SI inspections and that any flaws
> identified during the volumetric examination are to be within the
> limiting flaw sizes established by the SI qualification report.
>
> 5\. Performed such that deficiencies were identified, dispositioned,
> and resolved?
>
> e\. For the inservice inspection program:
>
> 1\. Has the licensee prepared an MRP-139 inservice inspection program?
> If not, briefly summarize the licensee's basis for not having a
> documented program and when the licensee plans to complete preparation
> of the program.
>
> 2\. In the MRP-139 inservice inspection program, are the welds
> appropriately categorized in accordance with MRP‑139? If any welds are
> not appropriately categorized, briefly explain the discrepancies.
>
> 3\. In the MRP-139 inservice inspection program, are the inservice
> inspection frequencies, which may differ between the first and second
> 10-year intervals after the MRP‑139 baseline inspection, consistent
> with the inservice inspection frequencies called for by MRP-139?
>
> 4\. If any welds are categorized as H or I, briefly explain the
> licensee's basis for the categorization and the licensee's plans for
> addressing potential PWSCC.
>
> 5\. If the licensee is planning to take deviations from the inservice
> inspection "requirements" of MRP-139, what are the deviations and what
> are the general bases for the deviations? Was the NEI 03-08 process
> for filing deviations followed?

Any issues identified during this inspection should be processed and
documented in accordance with NRC Inspection Manual Chapter (IMC) 0612,
"Power Reactor Inspection Reports." The significance of inspection
findings should be evaluated in accordance with applicable appendices of
IMC 0609, "Significance Determination Process." Any noncompliance with
NRC requirements resulting from this inspection should be evaluated and
documented in accordance with NRC Enforcement Policy (NUREG -1600) and
Section 3.12 of the NRC Enforcement Manual. Also, licensees are required
to address the findings resulting from the MRP-139 inspections (i.e.,
perform analyses and repairs) in accordance with existing requirements
in the ASME code and 10 CFR 50.55a.

2515/172-06 COMPLETION SCHEDULE

Up to three outages may be needed to complete the inspections associated
with this issue. The inspection activities identified in this TI should
be completed within one cycle of the last MRP-139 baseline inspections.
Inspectors may perform inspection of record-related aspects of the TI at
any time and, if an inspection opportunity is available, perform
inspections of mitigation and examination activities in this TI during
the refueling outages.

2515/172-07 EXPIRATION

This TI will expire on June 30, 2011, or upon completion of the MRP‑139
baseline inspections for all DMBWs in the PWR fleet. This TI will be in
effect for more than 24 months because the mitigation and MRP‑139
baseline inspection of DMBWs potentially affected by PWSCC will not be
fully addressed by all licensees for all affected components until at
least the end of calendar year 2010.

2515/172-08 CONTACT

For questions regarding the performance of this TI and emergent issues,
contact Ted Sullivan at (301) 415-2796 or e-mail Ted Sullivan at
<EJS@NRC.GOV>.

2515/172-09 STATISTICAL DATA REPORTING

All direct inspection effort expended on this TI is to be charged to
2515/172 for reporting by the Regulatory Information Tracking System
(RITS) reporting with an IPE code of TI.

2515/172-10 ORIGINATING ORGANIZATION INFORMATION

10.01 [Organizational Responsibility.]{.underline}

This TI was initiated by the Division of Component Integrity (NRR/DCI).

10.02 [Resource Estimate.]{.underline}

The estimated direct inspection effort to perform this TI is estimated
to be 40 to 60 hours per PWR unit per refueling cycle.

10.03 [Training.]{.underline}

No formal training is proposed for the performance of this TI. However,
if technical support is needed during the inspection of licensees' weld
mitigations, volumetric examinations or MRP-139 program, contact DCI
through IRIB at least 30 days before the anticipated need for technical
support.

2515/172-11 REFERENCES

Primary System Piping Butt Weld Inspection and Evaluation Guidelines,
MRP‑139, EPRI, Palo Alto, CA, July 2005. \[ML052150196\]

Safety Assessment on the Advanced Finite Element Analysis Related to
Growth of Postulated Primary Water Stress Corrosion Cracking Flaws in
Pressurizer Nozzle Dissimilar Metal Butt Welds, August 2007.
\[ML072400199\]

Mayfield, M.E. letter to Marion, A., NRC Staff Comments on MRP-139,
October 12, 2005 \[ML052720290\]

MRP 2006-018 MRP-139 Interim Guidance on Implementation Schedules,
August 11, 2006 \[ML080300470 \]

MRP 2007-039 MRP-139 Interim Guidance on Bare Metal Visual Inspection,
November 1, 2007 \[ML080300474\]

MRP 2007-038 MRP-139 Interim Guidance on Small Bore Volumetric
Inspection, November 1, 2007 \[ML080300478\]

Attachment 1

Revision History for TI 2515/172

+-----------+---------+----------------+-------+----------+------------+
| C         | Issue   | Description of | Tra   | Training | Comment    |
| ommitment | Date    | Change         | ining | Co       | Resolution |
| Tracking  |         |                | N     | mpletion | Accession  |
| Number    |         |                | eeded | Date     | Number     |
+-----------+---------+----------------+-------+----------+------------+
| N/A       | 0       | Support NRC    | N/A   | N/A      | M          |
|           | 2/21/08 | staff          |       |          | L080390335 |
|           |         | oversight of   |       |          |            |
|           | CN      | licensees'     |       |          |            |
|           | 08-009  | dissimilar     |       |          |            |
|           |         | metal butt     |       |          |            |
|           |         | weld (DMBW)    |       |          |            |
|           |         | mitigation and |       |          |            |
|           |         | inspection     |       |          |            |
|           |         | activities     |       |          |            |
|           |         | that are being |       |          |            |
|           |         | implemented in |       |          |            |
|           |         | accordance     |       |          |            |
|           |         | with the       |       |          |            |
|           |         | industry       |       |          |            |
|           |         | guidelines of  |       |          |            |
|           |         | the Materials  |       |          |            |
|           |         | Reliability    |       |          |            |
|           |         | Program (MRP)  |       |          |            |
|           |         | ‑139.          |       |          |            |
+-----------+---------+----------------+-------+----------+------------+
|           |         |                |       |          |            |
+-----------+---------+----------------+-------+----------+------------+
|           |         |                |       |          |            |
+-----------+---------+----------------+-------+----------+------------+
|           |         |                |       |          |            |
+-----------+---------+----------------+-------+----------+------------+
|           |         |                |       |          |            |
+-----------+---------+----------------+-------+----------+------------+
|           |         |                |       |          |            |
+-----------+---------+----------------+-------+----------+------------+