POLICY ISSUE

(Information)

April 10, 2003 SECY-03-0054

FOR: The Commissioners

FROM: William D. Travers /RA/

Executive Director for Operations

SUBJECT: REPLACEMENT OF NORTH ANNA, UNIT 2, REACTOR PRESSURE VESSEL

HEAD WITH A HEAD MANUFACTURED TO FRENCH STANDARDS

PURPOSE:

The purpose of this paper is to inform the Commission of the staff’s review of the replacement

of the North Anna, Unit 2, reactor pressure vessel head (RPVH).

SUMMARY:

In early 2003, Virginia Electric Power Company (VEPCO, the licensee) replaced the North

Anna, Unit 2, RPVH with a head manufactured to the French Nuclear Construction Code

(RCC-M) following the reconciliation process of Section XI of the American Society of

Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code). This effort was

unique, representing a first-of-a-kind activity for the staff and for the U.S. commercial nuclear

power industry. In overseeing this effort, the staff interacted with French and Belgian

regulators, the RPVH fabricator (Framatome ANP), conducted onsite inspections, and reviewed

the licensee’s design and reconciliation documentation. The staff determined there were no

regulatory barriers that precluded procurement of a replacement RPVH manufactured to the

RCC-M Code and believes other licensees, with licensing bases similar to North Anna, Unit 2,

may adopt a similar process.

Contact: John A. Nakoski, NRR

301-415-1068
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One of the more important technical issues identified by the staff involved the use of friction

welds to join the flange and tube portions of the vessel head penetration (VHP) nozzles. The

staff determined that the use of a friction weld in the fabrication of the VHP nozzles produced

high quality, repeatable welds when the requirements of the RCC-M Code are followed and that

such welds can be acceptable for use in commercial U.S. pressurized water reactors (PWRs).

Based on its oversight activities, the staff concluded that RPVHs fabricated to RCC-M Code are

of sufficient quality to ensure safety is maintained and that the replacement of the RPVH

enhanced the overall safe operation of North Anna, Unit 2.

BACKGROUND:

The licensee performed inspections of the North Anna, Unit 2, RPVH in the fall of 2002 in

accordance with the provisions of Bulletin 2002-02, "Reactor Pressure Vessel Head and Vessel

Head Penetration Nozzle Inspection Programs." During this inspection, VEPCO identified

numerous indications in 64 of the 65 VHP nozzle J-groove welds. Most of these indications

would require repair in accordance with the ASME Code. In addition, at several of the VHP

nozzles there was evidence of through-wall leakage. However, none of the indications were of

a size or location to cause a concern regarding the structural integrity of the welds. Therefore,

adequate safety margins were maintained during plant operation.

Originally, the North Anna, Unit 2, RPVH was scheduled to be replaced in the spring of 2004. 

As such, repairing the existing head would have resulted in operation for a cycle with the

repaired head, then replacement of the RPVH. However, to address these indications, VEPCO

determined that the appropriate course of action was to accelerate its plans to replace the

RPVH rather than repair the indications in the existing head. VEPCO’s decision was, in large

part, made with the knowledge that a replacement RPVH was available from Electricite de

France (EdF) through Framatome ANP (EdF RV Head No. 28R). The replacement RPVH was

manufactured by Framatome ANP in 1998 to the 1993 Edition, through the 1996 Addenda, of

the French RCC-M Code as part of the French program of replacing RPVHs at its PWRs to

address concerns with primary water stress corrosion cracking (PWSCC).

The licensee discussed various potential regulatory approaches to accomplish the RPVH

replacement at North Anna, Unit 2, with the staff. These included seeking relief from or

proposing alternatives to the requirements of ASME Section III, requesting exemptions from the

requirements of Title 10 of the Code of Federal Regulations (10 CFR) Section 50.55a that

incorporate the requirements of the ASME Code by reference, and replacing the RPVH as a

design modification using the reconciliation provisions of ASME Section XI seeking prior staff

approval, as a license amendment, only if needed.

The original RPVH was manufactured in 1968 at the Rotterdam Shipyards, in the Netherlands. 

At that time, foreign suppliers were not certified ASME vendors (no ASME "N" stamps). As

such, the head was procured to owner specifications that incorporated the technical

requirements of ASME Section III, 1968 Edition, and Westinghouse design specifications, but

was not "N" stamped. The important point of note is that the design and licensing basis for

North Anna, Unit 2, is the Owner’s Design Specification and not ASME Section III. Since the

original design and licensing basis of the RPVH is not ASME Section III, seeking a relief or an

alternative would not be appropriate, nor would exemptions from 10 CFR 50.55a. The
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appropriate approach was to implement the change following the reconciliation process of

ASME Section XI for procurement of replacement components. Under this approach, VEPCO

could proceed without prior staff approval provided there were no design changes introduced

that required a license amendment in accordance with the requirements of 10 CFR 50.59. 

Further, the replacement of the North Anna, Unit 2, RPVH was conducted in accordance with

the licensee’s Quality Assurance Program that meets the requirements of 10 CFR Part 50,

Appendix B. This approach is also applicable to North Anna, Unit 1, and Surry, Unit 1, for

which VEPCO plans a similar head replacement strategy, since the original design and

licensing basis for these units are similar to North Anna, Unit 2. While this approach is also

applicable to Surry, Unit 2, VEPCO plans to replace the Surry, Unit 2, RPVH with a head

manufactured to the ASME Code.

DISCUSSION:

The replacement of the North Anna, Unit 2, RPVH in January 2003, represented the first time a

major reactor component fabricated pursuant to the French RCC-M Code was used in a

commercial U.S. PWR. Subsequently, VEPCO announced its plans to replace the North Anna,

Unit 1, and Surry, Unit 1, RPVHs later in 2003 with heads that were manufactured for EdF

pursuant to the RCC-M Code. To assess whether the design, fabrication, examination, and

testing of the replacement RPVH were appropriately reconciled with the Owner’s Specification

through the ASME Code process, thereby providing reasonable assurance that adequate

protection to the public health and safety was maintained, the staff performed reviews and

inspections of the activities conducted by, or for, the licensee in the U.S. and in France. For

example, the staff met with the French regulatory authority (Bureau de Contrôle des Chaudières

Nuclèaires - BCCN) and Framatome ANP, and conducted inspections of replacement activities

at North Anna, Unit 2. In addition, the staff evaluated the design engineering and reconciliation

effort that the licensee performed for North Anna, Unit 2. The licensee followed the

requirements of Article IWA-4000 of the 1995 Edition, with Addenda through 1996, of

Section XI to the ASME Code, as incorporated by reference into 10 CFR 50.55a(b), to perform

the reconciliation. Finally, the staff met with Belgian regulatory organizations (l'Agence

Fèdèrale Contrôle Nuclèaire - FANC, Association Vinçotte Nuclear - AVN, and AIB-Vinçotte -

AV) to discuss their experience with reconciling the RCC-M Code to the ASME Code for the

replacement of the Tihange, Unit 1, RPVH.

Inspection activities were conducted using a draft inspection procedure prepared for RPVH

replacements as guidance. Feedback from the staff's experience with the North Anna, Unit 2,

RPVH replacement will be incorporated into this draft inspection procedure. An overview of the

other activities conducted by the staff is provided below.

French Technical Exchange Visit

In December 2002, the U.S. Nuclear Regulatory Commission (NRC) staff held discussions with

BCCN to discuss the regulatory framework under which RPVHs are designed and

manufactured in France. The outcome of this meeting was that the NRC staff had a clearer

understanding of the regulatory requirements for the design and fabrication, including quality

assurance requirements, of the RPVHs that VEPCO plans to install at North Anna, Units 1

and 2, and Surry, Unit 1. In addition to holding discussions with BCCN, the staff met with
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Framatome ANP to discuss the specific approach used to reconcile the differences in the

design specification of the original North Anna, Unit 2, RPVH and the replacement head, and

other activities being conducted for VEPCO to prepare the replacement head for use at the unit. 

VEPCO also participated in these discussions. As a result of these discussions, the NRC staff

developed a clear understanding of the approach being used; the level of detail required to

ensure that the reconciliation addressed all of the design, material, nondestructive examination

(NDE), and fabrication differences; and the quality assurance controls that were in place when

the replacement heads were manufactured. In addition, the staff toured the fabrication facility

and observed the North Anna, Unit 2, replacement RPVH during the final stages of the

preservice inspection being performed at the direction of VEPCO. Also, the staff observed the

storage conditions of the replacement heads for North Anna, Unit 1, and Surry, Unit 1.

One of the more important technical issues identified by the staff involved the use of friction

welds to join the flange and tube portions of the VHP nozzles. The welding process used is a

continuous drive friction welding process. This is a solid state welding process that, simply put,

rotates the flange portion while holding the tube portion still, aligning the pieces, pressing them

together while the flange is rotating to create heat, quickly stopping the rotating piece, and

pressing the pieces together under greater pressure. Section III of the ASME Code does not

allow the use of friction welds in the fabrication of Class 1 vessels and piping. However, in

France, of the approximately 5900 VHP nozzles manufactured using this process since 1981,

following the requirements of the RCC-M Code, there have only been five nozzles rejected

during the fabrication process due to a process variable being out of specification. None of the

nozzles have been rejected during post-fabrication NDE, nor has there been any operational

failure of these welds once in service. In addition, the French conducted extensive destructive

tests (including impact tests, side bend tests, tensile tests, and Charpy U-notch tests) and

nondestructive examinations of the product form of the weld during qualification of the process.

Key features of the replacement head highlighted by Framatome ANP were the fabrication

materials and methods used to mitigate PWSCC. Materials selected for the fabrication

(Alloy 690, Alloy 152, and Alloy 52) are considered more resistant to PWSCC than materials

previously used in RPVH fabrication. Framatome ANP presented information to the staff that

under laboratory conditions, Alloy 690 has been shown to have significantly more resistance to

crack initiation than Alloy 600. Tests were conducted on Alloy 690 and Alloy 152 weld material

at temperatures higher than encountered in reactor vessels. The tests were conducted using

samples cut from the representative forms of the materials (microstructure, section thicknesses,

primary water chemistry) used in replacement head fabrication. The tests were performed for

extended periods (multiple-year duration accelerated aging tests) at the conclusion of which

there was no evidence of crack initiation. It should be noted that the tests were not crack

growth rate tests, but rather crack initiation tests. While the testing has shown improved

resistance to crack initiation for Alloy 690 and the Alloy 152 weld materials, no information is

available for stress corrosion crack growth of either Alloy 690 or Alloy 152 weld materials. The

initiation tests suggest that Alloy 690 and Alloy 152 are generally more resistant to stress

corrosion cracking than the Alloy 600 or Alloy 182 materials previously used. As part of the

staff’s action plan in response to the Davis-Besse Lesson Learned Task Force, the staff will

collect information on nozzle cracking for Alloys 600 and 690, and other nickel-based alloys, in

order to evaluate the need to revise the RPVH inspection requirements. In addition, the staff

will evaluate the existing stress corrosion cracking models with respect to their continued use in
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the susceptibility index. As additional data becomes available regarding crack initiation and

growth in Alloys 690 and 152, the staff will re-evaluate what inspection requirements are

appropriate to ensure that the integrity of RPVHs fabricated with Alloys 690 and 152 are

maintained.

There are other metallurgical and welding issues that warrant confirmation to support the staff’s

long-term evaluation of these replacement heads (i.e., weldability of Alloy 152, potential

degradation of fracture toughness at lower temperatures, and crack initiation and growth

behavior at typical operating temperatures). These issues are being explored as part of the

ongoing research program being conducted by the staff. Further, in response to the

degradation observed on the Davis-Besse RPVH, and indications of throughwall cracks in

RPVH penetrations at other PWRs, Orders were issued on February 11, 2003, to all PWR

licensees requiring supplemental examinations of RPVHs (ADAMS Accession No.

ML030380470). As licensees replace their RPVHs, the units would likely be categorized as low

susceptibility plants based on the criteria specified in the Orders. This would allow the

licensees to conduct bare metal visual examinations of the RPVH and penetrations once every

third refueling outage or every five years (whichever is less), and to conduct ultrasonic

examinations and dye penetrant examinations of the J-groove welds of the RPVH penetration

nozzles every four refueling outages or seven years (whichever is less). The requirements of

the Orders may be changed, as allowed by the Orders, based on continuing research and

operating experience.

To establish baseline information for RPVHs fabricated for the French nuclear power industry,

Framatome ANP examines the J-groove welds by ultrasonic testing (UT) (the fusion zone or

heat-affected zone between the outer diameter of the VHP nozzle and the J-groove weld can

be examined). During these examinations, Framatome has found rejectable defects requiring

repair. Heads constructed at Framatome ANP to the ASME Code for the U.S. market do not

receive this examination. Framatome ANP also employs a polishing and honing process on the

J-groove welds. Framatome ANP believes this leaves only compressive residual stresses on

the weld surface that prevents the propagation of cracks from the surface. Additionally,

Framatome ANP changed the fabrication process for the form of the stock used to manufacture

the VHP nozzles. The current form of the Alloy 690 sleeve portion of the nozzles is hot

extruded round bar stock that has a well defined grain structure with little or no intragranular

carbides, and high intergranular carbide precipitation.

The staff notes that the material and processes used by Framatome ANP are believed to

provide a RPVH that offers improved resistance to PWSCC. However, the specifics of

fabrication processes used by other vendors, even when similar or the same materials are

used, will have to be evaluated to assure similar improvements in PWSCC resistance.

Belgian Technical Exchange Visit

In December 2002, the staff met with representatives of Belgian regulatory organizations. The

purpose of the meeting was to gain insights into the reconciliation conducted by Tractebel in

support of the Tihange, Unit 1, RPVH replacement. The replacement head was manufactured

to the RCC-M Code, whereas the original head was manufactured in accordance with ASME

Section III. The main differences identified in the Belgian reconciliation were (1) items
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constructed to the RCC-M Code were not required to be inspected by an authorized inspection

agency (AIA), however, inspections were conducted by EdF; (2) the allowance of friction welds

by the RCC-M Code between the flange and tube portions of the VHP nozzle, whereas friction

welds are not allowed to be used in the fabrication of pressure vessels or pipes by the ASME

Code; (3) requirements for auditing of suppliers differed between the two Codes; (4) the ASME

Code requires an overpressure protection report, whereas the RCC-M Code does not;

(5) differences in the quality assurance requirements; (6) differences in material specifications

between the two Codes; and (7) the hydrostatic test pressure is 1.25 times design pressure

under ASME and 1.33 under RCC-M.

Each of the differences between the two Codes was reconciled by Tractebel as documented in

a reconciliation report. In its reconciliation of the use of friction welds, AV inspectors conducted

an audit of the manufacturers’ facilities including Framatome ANP and SMFI (the subcontractor

that fabricated the VHP nozzles using the friction welding process), reviewed the qualification

files, reviewed the welding procedure qualification, reviewed the procedures for NDE, examined

the test coupon results, and witnessed UT and dye penetrant testing performed by Framatome

ANP. At the conclusion of the Belgian reviews, it was determined that the fabrication of the

replacement RPVH for Tihange, Unit 1, to the RCC-M Code was equivalent to a RPVH

fabricated to the ASME Code and acceptable for use.

During evaluation of VEPCO’s reconciliation documentation, the staff reviewed the Belgian

reconciliation report prepared by Tractebel. Based on this review, the staff found that the

conclusions of the Belgian reconciliation effort were consistent with the staff’s review, providing

additional confidence that RPVHs fabricated to the French RCC-M Code are of sufficient quality

to ensure safety is maintained.

Design Engineering and Reconciliation Inspection Activities

The staff found that VEPCO’s efforts to reconcile the design, fabrication, and examination of

the replacement RPVH with the current design requirements were acceptable, and provided

reasonable assurance that adequate protection to the health and safety of the public continued

to be maintained with the installation and use of the replacement RPVH. The staff noted that

the Framatome ANP manufacturer’s data report had been reviewed and accepted by

Framatome ANP’s Authorized Nuclear Inspector (ANI). The ANI stated: "The contents of this

report are accurate and, as far as possible, are equivalent to the requirements of Section III,

Division I of the ASME Code ...." The staff found that the records reviewed were of high quality,

providing an auditable record of VEPCO’s reconciliation and design change efforts.

There were no issues identified by the staff that required prior NRC approval before the

replacement RPVH could be placed in service at North Anna, Unit 2, and the unit was returning

to operation at the time the team completed its inspection activities. During the inspection there

were a number of observations made by the staff for which the VEPCO and Framatome staffs

provided prompt feedback to clarify how the reconciliation activities were conducted, to clarify

the results of the reconciliation, or to develop additional documentation supporting the bases for

reconciling the design, fabrication, examination, and testing of the replacement RPVH to the

North Anna, Unit 2, RPVH design specification. For example, in response to the staff’s

observation, VEPCO prepared and included an overview in the reconciliation report of the
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quality assurance processes and oversight activities related to VEPCO’s and Framatome’s

activities. Similarly, a VEPCO addendum was prepared that described other activities that had

been performed to support the reconciliation as it related to the NDE of the replacement RPVH.

The staff reviewed the welding procedures, processes, and records used in the fabrication of

the replacement RPVH. Of particular interest to the staff was the application of a friction

welding process in the fabrication of the VHP nozzles. As noted previously, the friction welding

process has been used in France to fabricate the nozzles since about 1981 and only five of the

approximately 5900 nozzles manufactured using this process have been rejected during the

fabrication process. None of the nozzles have been rejected during post-fabrication NDE and

there have been no failures of these welds once placed in operation. Based on the staff’s

review of the process and the operational experience of the French, the staff concluded that the

friction welding process, as controlled by the RCC-M Code, produces high quality, repeatable

VHP nozzle welds that can be used safely in commercial U.S. PWRs.

CONCLUSIONS:

Based on the staff’s technical exchange visits with French and Belgian regulatory authorities,

the tour and meeting with Framatome ANP, and staff inspection efforts, the staff made the

following conclusions:

• VEPCO's actions to replace the North Anna, Unit 2, RPVH with a head manufactured in

accordance with the RCC-M Code enhanced the overall safe operation of the unit.

• RPVHs fabricated to the 1993 Edition, through the 1996 Addendum, of the RCC-M

Code are of sufficient quality to ensure safety is maintained for use in commercial U.S.

PWRs provided an appropriate ASME, Section XI reconciliation process (i.e., Article

IWA-4000) is adhered to.

• The use of a friction weld in the fabrication of the VHP nozzles produces high quality,

repeatable welds when the requirements of the RCC-M Code are followed and such

welds can be acceptable for use in commercial U.S. PWRs.

• For commercial U.S. PWRs with similar design and licensing bases to North Anna,

Unit 2 (i.e., original RPVH procured without an ASME "N" stamp), there are no

regulatory barriers that would preclude procurement of a replacement RPVH

manufactured to the 1993 Edition, through 1996 Addendum, of the RCC-M Code.

RESOURCES:

The review of the reconciliation of the North Anna, Unit 2, RPVH replacement with a head

fabricated to the requirements of the RCC-M Code required technical expertise in the areas of

quality assurance; materials; welding; nondestructive examination; ASME, Sections III, IX, and

XI; and design. The direct effort expended included the following resources:
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• Technical Exchange Visits 0.19 FTE

• Onsite Inspection Activities 0.25 FTE

• Reconciliation Inspection Activities 0.30 FTE

There were unique aspects to the North Anna, Unit 2, RPVH replacement that should not be

necessary for future replacements. For example, the technical exchange visits need not be

repeated for other RPVH replacements. Further, for units that procure replacement RPVHs

under ASME, Section III, the reconciliation inspection activities can be significantly reduced as

there is no need to assess the impact of the differences between the RCC-M Code and ASME

Code requirements. Similarly, units that procure replacement RPVHs under the 1993 Edition,

through 1996 Addendum, of the RCC-M Code, provided this approach is consistent with their

licensing basis, would not require the NRC staff to repeat its assessment of differences

between the RCC-M and ASME Codes even though the licensee would need to follow the

requirements of ASME, Section XI related to reconciliation. Therefore, staff review of the

design aspects of RPVH replacements in these cases could be accomplished using about half

of the effort expended during the North Anna, Unit 2, reconciliation inspection. Similar

resources would be expended by the staff inspecting these activities for subsequent

replacement heads and the staff estimates that future RPVH replacement activities at other

units would require:

• Onsite Inspection Activities 0.25 FTE

• Design Engineering Inspection Activities 0.15 FTE

Inspections of the replacement of RPVHs have not been specifically budgeted. However, there

are resources set aside for supplemental inspection activities in the current budget that can be

used to conduct these emergent inspections. As licensees inform us of their plans to replace

RPVHs, the staff will use the Planning, Budgeting, and Performance Management process to

provide inspection resources that may be beyond the current budget allocation for supplemental

inspection activities.

COORDINATION:

The Office of the General Counsel has reviewed this paper and has no legal objection to its

contents. The Office of the Chief Financial Officer has reviewed this paper for resource

implications and has no objections.

/RA by William F. Kane Acting For/

William D. Travers

Executive Director

 for Operations
The Commissioners - 8 -

• Technical Exchange Visits 0.19 FTE

• Onsite Inspection Activities 0.25 FTE

• Reconciliation Inspection Activities 0.30 FTE

There were unique aspects to the North Anna, Unit 2, RPVH replacement that should not be

necessary for future replacements. For example, the technical exchange visits need not be

repeated for other RPVH replacements. Further, for units that procure replacement RPVHs

under ASME, Section III, the reconciliation inspection activities can be significantly reduced as

there is no need to assess the impact of the differences between the RCC-M Code and ASME

Code requirements. Similarly, units that procure replacement RPVHs under the 1993 Edition,

through 1996 Addendum, of the RCC-M Code, provided this approach is consistent with their

licensing basis, would not require the NRC staff to repeat its assessment of differences

between the RCC-M and ASME Codes even though the licensee would need to follow the

requirements of ASME, Section XI related to reconciliation. Therefore, staff review of the

design aspects of RPVH replacements in these cases could be accomplished using about half

of the effort expended during the North Anna, Unit 2, reconciliation inspection. Similar

resources would be expended by the staff inspecting these activities for subsequent

replacement heads and the staff estimates that future RPVH replacement activities at other

units would require:

• Onsite Inspection Activities 0.25 FTE

• Design Engineering Inspection Activities 0.15 FTE

Inspections of the replacement of RPVHs have not been specifically budgeted. However, there

are resources set aside for supplemental inspection activities in the current budget that can be

used to conduct these emergent inspections. As licensees inform us of their plans to replace

RPVHs, the staff will use the Planning, Budgeting, and Performance Management process to

provide inspection resources that may be beyond the current budget allocation for supplemental

inspection activities.

COORDINATION:

The Office of the General Counsel has reviewed this paper and has no legal objection to its

contents. The Office of the Chief Financial Officer has reviewed this paper for resource

implications and has no objections.

William D. Travers

Executive Director

 for Operations

*See previous concurrence **concurred via email

ADAMS Accession Number: ML030580391

OFFICE PDII-1/SC PDII-1/LA PDII RII/DRS DIPM/DD

NAME JNakoski CHawes* HBerkow* CCasto** BBoger*

DATE 04/8/03 02/25/03 02/25/03 02/28/03 3/6/03

OFFICE DE/DD DLPM/DD ADIP ADPT OGC

NAME RBarrett* JZwolinski* RBorchardt* BSheron* RWeisman for JMoore*

DATE 3/3/03 3/10/03 3/26/03 3/11/03 3/21/03

OFFICE OCFO RES/DET NRR/D DEDR EDO

NAME BFicks* MMayfield* SCollins* WKane WTravers

DATE 3/24/03 3/7/03 3/31/03 04/10/03 04/10/03

OFFICIAL RECORD COPY