ML20210L731

SER Accepting Babcock & Wilcox Owners Group Topical Rept BAW-2244, Demonstration of Mgt of Aging Effects for Pressurizer

ML20210L731
Person / Time
Issue date:	08/18/1997
From:	NRC (Affiliation Not Assigned)
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ML20210L638	List: ML20210L634 ML20210L731
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PROJECT-683 NUDOCS 9708210288
Download: ML20210L731 (33)

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FINAL SAFETY EVALUATION REPORT CONCERNING BABCOCK & WILCOX OWNERS GROUP TOPICAL REPORT No. BAW 2244

" DEMONSTRATION OF THE M/.NAGEMEh T OF AGING EFFECTS FOR THE PRESSURIZER" PROJECT No. 683 9708210288 970818 PDR TOPRP EMVFRAMA C PDR

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T/.BLE OF CONTENTS 1

I NT R O D U CTI O N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Babcock & Wilcox Owners Group Topical Report BAW.2244 . . . . . . . . . . . . . . 1 1.2 Conduct of staff Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.3 Organization of this Report . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2

SUMMARY

OF TOPICAL REPORT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.1 Components and Intended Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 2.2 E ff e ct s o f A gin g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.3 Aging Management Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3

STA F F EVAL UATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1 Components and lntended Functions . . . . . . . . . . . . ................ .. 4 3.1.1 Components . . . . . . . . . . ............. ........... .4 3.1.2 Intended Functions . . . . . . ..........................6 3.2 E f f e ct s o f A g in g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... .B 3.2.1 Pressurizer Pressure Vessel . . . . . . . . ........ ........ 8 3.2.2 Pressure Vessel Nozzles . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3.2.3 Other Pressure-Retaining Cumponents . . . . . . ...... ... 12 3.2.4 Pressure Retaining Bolting . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.2.5 Integral Attachments . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.3 Aging Management Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.3.1 Industry Operating Experience Review . . . . . . . . . . . . . . . . . . 13 3.3.2 Evaluation of Aging Management Programs . . . . . . . . . . . . . . 14 4 CONCLUSIONS . . ................................................. . 29 4.1 Renewal Applicant Action items . . . . . . . . . . , . . . . . . . . . . . . . . ...... , 29 4.2 Open item s . . . . . . . . . . . . . . . . . . . . . . ............... . .., . . 30 Appendix l - List of References . . . . . . . . . . . . . . . . . . . . ...... ....., . .. . .

, 32 Appendix tl List of Correspondence . . . . . ...................... .... ..... . . 33 til

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i INTRODUCTION Pursuant to Title 10. Section 50.51, of the Code of federalRegulations (10 CFR 50.51), the U.S.

Nuclear Regulatory Commission (NRC) issues licenses to operate nuclear power plants for a l

fixed period not to exceed 40 years. Before expiration of the current operating term, the NRC l may renew these licenses for an additional period not to exceed 20 years. The amended license renewal rule,10 CFR Part 54, published in the FederalRegister on May 8,1995 (Ref.1), sets forth the requirements for renewing operating licenses for commercial nuclear power plants.

The license renewal rule requires an applicant to perform an integrated plant assessment (IPA).

As specified under 10 CFR 54.21(a)(1), the first step of an IPA requires an applicant to identify and list the structures and components subject to aging management review. In addition, 10 CFR 54.21(a)(2) requires an applicant to describe and justify the methods used to meet the requirements of 10 CFR 54.21(a)(1). Next,10 CFR 54.21(a)(3) requires that, for each structure and component identified under 10 CFR 54.21(a)(1), an applicant demonstrate that the effects of aging will be adequately managed so that the intended function (s) will be maintained consistent with the current licensing basis (CLB) during the period of extended operation. This demonstration may be presented in a plant specific application, or in the form of a topical report developed for a defined scope of structures and/or components.

1.1 Babcock & Wilcox Owners Group Topical Report BAW 2244 By letter dated August 31,1995, the Babcock & Wilcox Owners Group (B&WOG), Generic License Renewal Program (GLRP) submitted topical report BAW 2244," Demonstration of the Management of Aging Effects for the Pressurizer" (Ref. 2), for review and approval by the Nuclear Reactor Regulation (NRR) staff of the NRC. This report provided a technical evaluation of the effects of aging on the pressurizer, and a demonstration that B&WOG member plant owners can adequately manage these aging effects during the period of extended operation associated with license renewal. The report was intended to provide the nuclear power plant utility owners participating in the B&WOG GLRP with the necessary technical details relating to the pressurizer for submitting a license renewal application.

1.2 Conduct of Staff Eva'uation The staff reviewed BAW 2244 to determine whether it provided adequate information to meet the requirements set forth in 10 CFR 54.21(a)(3). After completing the initial review, the staff issued several requests for additionalinfnrmation (RAls). B&WOG representatives responded in writing to the staffs RAls and provided further clanfication in a number of public meetings held with the staff. Appendix ll of this SER is a liet of correspondence that documents the RAls, meeting summaries, and other information applicable to this SER.

1.3 Organization of this Report This SER provides a summary of the topical report, BAW 2244, the details of the staffs evaluation, a description of the action items identified by the B&WOG and documented in BAW 2244, and a description of the open items identified by the staff during the evaluation of BAW 2244. A list of references and correspondence used by the B&WOG and the staff in the development and evaluation of BAW 2244 is provided as well.

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For consistency with BAW 2244, the staff used the terms " components" or " pressurizer components" to refer to the constituent parts of the pressurizer within the content of this SER.

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SUMMARY

OF MPICAL REPORT The B&WOG topical report, BAW 2244, contained a technical evaluation of the aging effects relating to Babcock and Wilcox (B&W) pressurizer, and was provided to the staff to demonstrate that B&WOG member plant owners can adequately manage these effects of aging during the period of extended operation. This evaluation specifically applied to the following B&WOG GLRP member plants:

Arkansas Nuclear One, Unit 1 (ANO 1)

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Oconee Nuclear Station, Units 1,2 and 3 (ONS 1, 2 and 3)

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Three Mile Island, Unit 1 (TMI 1)

The time-limited aging analyses (TLAAs) associated with B&W pressurizers, as defined in 10 CFR 54.3, are beyond the scope of BAW 2244. These pressurizer re!sted TLAAs included transient cycle count assumptions needed for fatigue usage factor calculations and flaw growth acceptance under American Society of Mechanical Engineers (ASME), Boiler and Pressure Vessel (B&PV) Code,Section XI(Ref 3). These TLAAs will be evaluated on a plant specific l basis, i

2.1 Components and intended Functions The B&WOG topical report addressed the effects of aging on B&W pressurizers. Section 2 of BAW 2244 contained a detailed description of the pressurizer and its components, and the materials used in their construction. Within the report, the pressurizer components were divided into the following five component categories:

(1) pressurizer pressure vessel (2) pressurizer nozzles (3) other pressure-retaining items (4) pressure-retaining bolting (5) integral attachments As reported in BAW-2244, the pressure vessel included the vessel shell, heads, and heater belt forgings. The pressurizer nozzle included the attached safe ends and the long weld necks, out to, but not including, the welded connection to the reactor coolant system (RCS) piping. Other pressure-retaining components included the manway, heater bundles, and heater bundle cover plates, instrument lines and sample-lines connected to the pressurizer were evaluated in Topical Report BAW-2243," Demonstration of the Management of Aging Effects for the Reactor Coolant Pressure Boundary Piping"(Ref. 4). The review of BAW-2243 by the staff was documented in the related SER dated March 21,1996 (Ref 5).

The B&WOG stated that maintaining pressure boundary was the only intended function for the components within the evaluation boundary assessed in BAW 2244 that required an aging management review.

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l 2.2 Effects of Aging The B&WOG topical report, BAW 2244, evaluated the applicability of the following aging effects on pressurizer components:

cracking (initiation and growth)

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has of frecture toughness

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loss of matedal e

loss of mechanical closure integrity (fnr bolted connections)

The B&WOG reviewed industry operating experience for aging effects relating to pressurizers.

Table 3.1 in BAW 2244 summadzed the aging effects identified during the operating experience review. The following is a summary of Table 3.1:

Component Cateaory Potential Effects of Aalno Pressurizer Vessel Cracking of welded joints Loss of material (extemal surfaces)

Pressurizer Vessel Cracking of weldedjoints Nozzles Loss of material (extemal surfaces)

Cracking at or near welds Other Pressure- Loss of material '

Retaining items Cracking at or near welds Cracking of Base Metal Pressure-Retalning Loss of material Bolting Cracking Loss of preload/ cloture integrity Integral Attachments Cracking of welded joints Loss of material (extemal surfaces) 2.3 Aging Managament Programs Table 4.1 in BAW 2244 summarized the specific programs used at ANO, ONS, and TMl to

- provide reasonable assurance that the effects of aging will be adequately managed such that the intended function will be maintained consistent with the CLB during the period of extended operation. The following is a list of the programs from Table 4.1:

ASME B&PV Code,Section XI, inservice Inspection (ISI) Program (Ref. 3) e response to Generic Letter (GL) 88-05 (Ref. 6) on boric acid corrosion

- response to Bulletin (BL) 82-02 (.~,sf. 7) on fastener degradation information developed from Information Notice 9010 on Alloy 600 cracking (Ref,8)

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Technical Specifications primary coolant leakage limits and surveillance requirements Technical Specifications primary coolant water chemistry requirements On the bases of the evaluation presented in BAW-2244, the B&WOG concluded that these programs were adequate to manage the aging effects on the pressurizer components.

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3 STAFF EVALUATION

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The staff reviewed BAW 2244, as well as additionalinformation submitted by the B&WOG, to perform its evaluation. In accordance with 10 CFR 54.21(a)(3), the staff evaluated this information to determine if the B&WOG demonstrated that the aging management programs, as desenbod within the report, could adequately manage the effects of aging relating to the pressurizer such that the intended function would be maintained consistent with the CLB during the period of extended operation.  !

The staff did not review information relating to the individual B&WOG-GLRP plants to determine whether the report accurately reflected their respective pressurizer designs and included all constituent components. Consequently, when referencing this report, in order to demonstrate that they can adequately manage the aging effects relating to their pressurizer during the period of extended operation, each participating B&WOG member plant must demonstrate that its pressurizer design is consistent with BAW 2244. This demonstration, that an applicant's pressurizer design is consistent with BAW 2244, will be a required applicant action item.

In addition to IPA, applicants are required to provide an evaluation of TLAAs in accordance with 10 CFR 54.21(c). Because the B&WOG has elected to exclude TLAAs applicable to the pressurizer from the scope of BAW 2244, TLAAs relating to B&W pressurizers will be reviewed on a plant specific basis at the time of application.

3.1 Components and Intended Functions This section of the SER contains the staff evaluation of the pressurizer components determined l by the B&WOG to be within the scope of BAW 2244, and the intended function associated with

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3.1.1 Components As summarized in Section 2 of this SER, BAW 2244 divided the pressurizer into five component categories to ensure a comprehensive review of the associated aging effects and aging management programs.

The pressurizer components addressed in BAW 2244 are the pressurizer pressure vessel, pressure vessel nozzles, other pressure-retaining components, pressure retaining bolting, and integral attachments. The pressurizer vessel evaluation boundary was extended to include the attached safe ends and long weld necks, out to but not including the welded connections with the RCS piping. The welded connection at the RCS piping was addressed in the B&WOG topical report BAW 2243 (Ref. 4). The welds included within the scope of BAW-2244 were the vessel welds, the welds attaching nozzles to the vessel, the welds attaching nozzles to safe ends, the weld buildup for the manway, the pressure retaining welds for heater bundle items, and the welds used to connect integral attachments to the pressurizer.

Examples of the pressure vessel components in Category 1 included the vessel shell, the vessel heads, and the heater belt forgings. Examples of pressure vessel nozzle components in Category 2 included the vont and sample nozzles, pressure relief nozzles, spray nozzle, thermowells, level sensing nozzles, and the surge nozzle and thermal sleeve. The pressure retaining components in Category 3 included the manway and heater bundle pressure retaining components. The pressure retaining bolting in Category 4 included the manway cover bolting and the botting for the three heater bundle cover plates. The integral attachments in Category 5 4

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were comprised of the pressurizer vessel support bracket assemblies. The welds within the scope of BAW 2244 were issoc:sted with each of the five categories and were categorized with their applicable components.

The B&WOG excluded several components, within the scope of the pressurizer report from further evaluation. The B&WOG based this exclusion on the rationale that certain components either did not have an intended function that met the criteria of 10 CFR 54.4, or the intended function (s) of the component were performed with moving parts or with a change in configuration or properties. Specifically, the B&WOG excluded the pressurizer heaters, intemal surge line components, the spray head and intemal spray line components, heater bundle assembly components, vessel lifting lugs, intemal maintenance equipment support plates, and intemal ladder. Section 3.1.2 of this SER addresses the staffs assessment of the exclusion of these items.

The staff noted that BAW 2244 may not contain a complete listing of the structures and components subject to aging management review for the B&WOG member plants as is required under 10 CFR 54.21(a)(1). The report also did not describe and justify the methodology for generating such a list, as is required under 10 CFR 54.21(a)(2). With the exception of assessing t;1e acceptability of excluding certain pressurizer components from the scope of components requiring an aging management review, the staff did not make any finding relative to the completeness of the list of pressurizer components subject to aging management review or the adequacy of the B&WOG scoping methodology. Consequently, to demonstrate compliance with the intent of 10 CFR 54.21(a)(1) and (2), individual applicants will need to provide a site specific list of structures and components subject to an aging management review, and a methodology for developing this list, as part of their license renewal applications.

The staff noted that the B&WOG elected not to address a repaired upper level nozzle at ANO-1.

This upper level nozzle had an Alloy 182 weld buildup pad added to the outer surface of the pressurizer shell nozzle penetration. The staff will evaluate this nozzle on a plant specific basis if ANO-1 submits an application for a renewed license.

in RAI No. 9, the staff noted that BAW 2244 excluded the manway gasket from the scope of the pressurizer report because it was a replacement item and met the provisions of 10 CFR 54.21(a)(1)(ii). The B&WCG report stated that the manway gasket is replaced each time the manway cover is installed, in addition, as part of the leakage monitoring program, the gasket would be replaced if any detectable leakage occurred from the manway. In its response to RAI No. 9, dated February 20,1996, the B&WOG stated that the manway gasket will be considered within the scope of license renewal; however, the B&WOG maintained that the gasket was not subject to aging management review because it is short-lived and is replaced on the basis of performance and condition monitoring.

The staff agreed that the manway gasket was within the scope of license renewal. In addition, the staff agreed with the conclusion that the gasket did not require an aging management review; however, the staff conclusion was based on different reasons than those cited by the B&WOG.

Specifically, the staff notes that the manway gasket is part of the bolted connection. As such, the manway gasket exists to minimize leakage and is not solely responsible for providing oressure boundary or supporting a structuralload.

Pressure boundary integrity is maintained by the manway bolts / studs, manway cover, and pressure vessel. Degradation of any or all of these components as a result of boric acid corrosion could threaten the pressure boundary function. The staff evaluation of the aging 5

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management program for the pressurizer manway bolted connection is provided in Section 3.3.2.3 of this SER.

3.1.2 Intended Functions in the B&WOG response to RAI No.1, dated February 20,1996, the B&WOG stated that the

" pressurizer supports two component intended functions:

(1) To maintain the reactor coolant pressure boundary (RCPB).

(2) To provide RCS pressure control for regulated events (except ANO-1) as defined by 10 CFR 54.4(a)(3)"

The B&WOG provided additional clarification on the component intended functions when they stated that the " pressurizer supports the pressure boundary by the integrity of the items that were part of the RCS pressure boundary," and that "the pressurizer supports the control of RCS pressure by operation of the heaters and flow through the spray head and surge line." The B&WOG considers the safety related heaters as being required during regulated events for ONS-1 2 and 3, and TMI 1.

The staff agreed with the B&WOG determination that the component intended functions applicable to the pressurizer and within the scope of license renewalincluded the need to maintain the pressurizer pressure boundary (and ultimately the RCS pressure boundary) and control RCS pressure in accordance with the CLB.

In a letter, dated April 17,1996, the B&WOG stated that the pressurizer heaters were not subject j to an aging management review because their function was accomplished through a change of 1

configuration or propertie .. The B&WOG contended that by energizing and performing their intended function, the heaters converted electrical energy into heat. The B&WOG further contended that this conversion of one form of energy to another (electrical energy to heat) was consistent with a change ;n configuration or properties; thus heaters should be considered active components.

The intended functions of the pressurizer heaters as defined by the B&WOG were (1) to maintain the RCPB and (2) to provide RCS pressure control for regulated events (except ANO-1). The statement of consideration (SOC) published in the FederalRegister(60 FR 22477), dated May 8, 1995, discussed structures and components that may have functions that both meet and do not meet the requirements of 10 CFR 54.21(a)(1). On this basis, the staff asserted that the first intended function of the pressurizer heaters (to maintain the RCPB) met the criteria of 10 CFR 54.21(a)(1). The pressurizer heater pressure boundary m maintained by preserving the integrity of the heater sheath (or sleeves) and end caps. Therefore, tho heater sheath (or sleeve) and end caps were subject to an aging management review. The staff also agreed that, for the purposes of license renewal, the second intended function (to provide RCS pressure control for regulated events) was an active function that did not meet the criteria of 10 CFR 54.21(a)(1) but for different reasons than stated by the B&WOG.

RCS pressure controlis maintained by cycling the pressurizer heaters on and off and, therefore, required a change in the energized state cf the heaters to perform the intended functions. In the SOC (60 FR 22477), the Commission had concluded that "a change in configuration or properties" should be interpreted to include "a change in state." In addition, the SOC (60 FR 22472 and 60 FR 22477) state the following: " Functional degradation resulting from the effects of aging on active functions is more readily determinable...;" and "The Commission has 6

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determined that passive structures and components for which aging degradation is not readily monitored are those that perform an intended function without moving parts or without a change in configuration or properties...;* respectively. Any degradation of the pressurizer heaters to provide RCS pressure controlis readily monitorable through normal operating pressure and alarme, and technical specification surveillance requirements of the pressurizer heaters. On the bases of a change in configuration and readily monitorable effects of age degradation, the staff concluded that the pressurizer heaters RCS pressure control function did not meet the criteria of 10 CFR 54.21(a)(1) and was not within the scope of aging management review.

The intemal surge line components included the diffuser, diffuser cap, and diffuser cap support legs. The B&WOG stated that the intended fi 4 tion of the intemal surge line components was to provide minor thermal mixing during in-surge., of coolant into the pressurizer, and their absence would not impact the pressure control function. The staff agreed with the B&WOG assessment ,

that the failure of these components would not affect performance of the pressure control  ;

function. The staff also agreed that the intemal surge line components were not part of the RCPB. Therefore, these components were not within the scope oflicense renewal and not subject to the requirements of 10 CFR 54.21(a)(3).

In their response to RAI No. 7, dated February 20,1996, the B&WOG stated that the spray hu and associated intemal spray line items did not support the pressurizer pressure boundary.

Therefore, the B&WOG contends that these components were not necessary to shut down the reactor and maintain it in safe shutdown condition; not required to mitigate design basis accidents as defined by Chapter 15 of each plant's final safety analysis report; and not credited for compliance with the Commission's regulations for fire protection (10 CFR 50.48),

environmental qualification (10 CFR 50.49), pressurized thermal shock (10 CFR 50.61),

anticipated transients witt wt scram (10 CFR 50.62), and station blackout (10 CFR 50.63).

Furthermore, the B&WOG s'ated that industry experience did not support a scenario in which failure of the spray head or intemai spray line items leads to a loss of the pressurizer pressure boundary. Consequently, the Bi.'.WOG contended that such a scenario was beyond the scope of the pressurizer design and otherwise hypothetical. De staff agreed t;iat the spray head and intemal spray lir,c .tems did not support any of the intended functions defined la 10 CFR 54.4(a) and, therefore, were not within the scope of license 7newal.

The B&W pressurizer was designed with three heater bunale assemblies, each uf which consisted of three parallel disks (two referred to as support plates, and one referred to as the diaphragm plate) drilled to hold 39 individualimmersion heaters. The heater bundle assembly components included heater bundle assembly support plates, the heater bundle assembly hc.tontal guide plates or guide rails, and heater bundle assembly suoport collars. None of these components supported the pressure boundary or pressure control functions. Furthermore, a failure of these components would not lead to a loss of the pressure boundary or pressure control functions. Tnerefore, the staff determined that these components were not within the scope of license renewal.

The vessel lifting lugs. intemal maintenance equipment support plates, and the intemal ladder also did not support the ressure boundary or prusure control functions, because failure of these components would not effect the pressurizer pressure boundary or RCS pressure control.

Therefore, the staff made the determination that these components were not within the scope of license renewal. In the case of the O-rings between the heater bundle diaphragm plates and heater belt forgings, the pressure boundary function has been extended to the seal welde located between the heater bundle diaphragm plate and the indiviriual heater sheaths or the heater sleeves. Therefore, the staff made the determination thd the O' ring. t>> tween the heater bundle 7

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diaphragm plates and heater belt forgings were not within the scope of license renewal.

However, the seal wel6 that performed the pressurizer pressure boundary function were within i' the scope of license renewal.

3.2 Effects of Aging i

As discussed in Section 2.2 of this SER, the effects of aging evaluated in BAW 2244 included cracking (initiation and growth), loss of fracture toughness, loss of material, and loss of mechanical closure integrity (for bolted connections). The B&WOG reviewed these effects for their specific applicability to the pressurizer components within the scope of the report.

After reviewing BAW-2244, the staff identified Open item No.1 (discussed in Section 3.2.1 and 4.2 of this SER) that, in addition to cracking of welded joints and base metals, required the B&WOG to address the potential cracking of tne stainless steel cladding, in addition, the staff concluded that a primary water chemistry program could not be used to justify precluding stress corrosion cracking (SCC) of stainless steels, as a potential aging effect. With the exception of Open item No.1, the staff agreed that the B&WOG had properly identified the potential aging effects to be evaluated for the five categories of the pressurizer components as discussed in Sections 3.2.1 through 3.2.5 below.

3.2.1 Pressurizer Pressure Vessel The B&W pressurizer vessel as defined in BAW 2244 consisted of a vertical cylindrical shell with a semi-hemispherical head at both the top and the bottom. its dimensions were documented as nominally 42 feet,8.625 inches in height from top to bottom and 96.375 inches in ouw diameter.

The vessel walls were identified to be 6.1875 inches thick at the cylindrical section,12.5 inches at the heater belt forgings, and 4.75 inches at the upper and lower welds. These sections were formed from carbon steel plate, while the upper and lower heads were formed from hot pressing 5.125-inch carbon steel plato. The pressurizer sections were intemally clad with stainless steel, in BAW-2244, the B&WOG stated that the potential effects of aging on the clad carbon steel pressurizer vesselinclude crackir:g of the base metal welded joints and loss of material from the external surfaces. The staff concurred with this assessment. When degraded as a result of cracking, the clad carbon steel pressurizer vessel may not have the structural integrity to withstand design-bases event loads (such as seismic loads) prescribed in the plant's CLB.

Cracking within the welded carbon steeljoints (i.a, circumferential and longitudinal welds of the pressurizer vessel) was considered an applicable aging effect for the period of extended operation because of the potential for pre-service and service-induced flaws. The staff agreed with the B&WOG that the pressurizer base rr-tal welded joints were potentially susceptible to cracking. The reason for this susceptibility w.s that the welds contained residual welding stresses, and the associated heat affected zones (HAZ) contained a microstructure susceptible to cracking as a result of being exposed to welding temperatures. BAW-2244 also stated that, other than welded joints, the pressurizer base metal was not susceptible to cracking, provided that the cladding mate,ial remains intact. The reason for this was that the base metalitself was not affected by the welding process. The staff agreed that,if not exposed to primary coolant, cracking of the surrounding base metal would not be an applicable aging effect for the period of extended operation. However, the base meto! material was susceptible to age-related cracking or loss of materialif exposed to primary csolant as a result of cracking or loss of the cladding material.

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The pressurizer vessel was clad on the inside surface with stainless steel. This cladding was not l credited in the plant's CLB as a load-bearing element of the pressuriz' " vessel; however, cracking orloss of cladding material could expose the underlying base metal to the reactor i coolant environment. This can result in the loss of material or cracking of the base metal, thus I challenging the structuralintegrity of the pressurizer vessel and its ability to withstand design basis hads.

Strict control of the cladding fabricat!on and application processes precluded significant cladding flaws and ensured a sound bond between the cladding and the base metal material. However, industry experience has shown that the stainless steel cladding in pressurizers may be Nceptible to cracking. For example, BAW 2244 identified a non-B&W plant that experienced numerous clad cracks with one crack extending into the base metal of the pressurizer.

The pressurizer pressure vessel was known to be subject to thermal stresses while in service including stresses induced by water level fluctuations and energized heaters with a potential for thermal fatigue. The staff also noted that welds used to attach items to the vessel internal clad surfaces could potentially crack and propagate into the vessel walls. The B&WOG did not consider clad cracking an applicable aging effect. Nonatheless, for the reasons stated above, the staff considered cracking of pressurizer stainless steel cladding an aging effect that needed to be addressed. Industry experience has also shown that cracking of the cladding can penetrate through the base metal of the pressurizer that raised concems with the integrity of the pressure vessel and its ability to perform its intended function under CLB design eding conditions.

In a draft version of this SER, dated September 13,1996, the staff made the potential clad cracking issue Open item No.1. Cpecifically, the staff stated that the B&WOG must propose a program to address potential cracking of the stainless steel cladding of the pressur,zer vessel. In that draft SER, the staff suggested that one way to demonstrate the integrity of the pressurizer cladding would be to conduct an additionalinspection of the stainless steel cladriing as a prerequisite to licanse renewal. This inspection would provide evidence that the, dadding had not experienced cracking. If a flaw were detected, Appendix B to 10 CFR far+ 50 would require a root cause determination and corrective measuras.

in its response to this open item, dated November 22,1996, the B&WOG m:intained that, although industry has experienced cracking of the cladding, the incident in question was not -

appucable tc pressurizers designed by B&W. As such, the B&WOG deferred resolution of this open item, including any agreement to perform a one-time cladding inspection as suggested by the staff, to a plant-specific renewal application. Therefore, this item remained open.

The B&WOG stated that lost of fracture toughness due to thermal embrittlement was not an applicable aging effect for B&W pressurizer vessel materials. The staff concurred with this assertion because the materials used and the relatively low operating temperatures of pressurized water reactors (PWRs) did not create conditions conducive to thermal embrittlement.

The B&WOG indicated that the loss of bare metal material from the extemal surfaces cf the pressurizer as a result of boric acid wastage was an applicable aging effect. Experience has shown that primary coolant leakage onto the extemal surfaces of carbon steel components can cause boric acid corrosion that will ultimately result in loss " material. The staff agreed with the fact that the loss of base metal material from beric acid corrosion was an aging effect applicable to license renewal.

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3.2.2 Pressure Vessel Nozzles Category 2 components (pressure vessel nozzles) included full-penetration welded nozzles, pressure-retaining partial-penetration welded nozzles, and pressure-retaining dissimilar metal welds in vessel nozzles. The pressurizer shell contained 18 penetrations. Associated nozzles

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were fabricated from either Alloy 600, stainless steel, or carbon steel cladded with stainless steel. Safe ends and thermal sleeves were fabricated from either stainless steel or Alloy 600.

Stainless steel safe ends or long weld necks were attached to the surge and pressure relief nozzles at all plants, For full-penetration welded nozzles, Alloy 600 safe ends were attached to the spray nozzles at all plants and to the sampling and level sensing nozzles at ONS-1,-2 and -3, and TMI-1. Pressure- i retaining partial-penetration welded nozzles were fabricateo from Alloy 600. Pressure-retaining dissimilar metal welds in vessel nozzles, specificady the surge nozzle and spray nozzle, were fabricated from clad cart >on steel with either stainless steel or Alloy 600 safe ends attached with Alloy 82/182 weld material.

3.2.2.1 Full-Penetration Welded Nozzles I

As discussed in Section 3.2.1 of this safety evaluation, the B&WOG stated that the potential effects of aging on clad carbon steel nozzles were the same as for the pressurizer clad carbon steel vessel; i.e., cracking of wtJded joints and loss of material (extemal surfaces). With the exceptiori of Open item No.1, the staff agreed that these aging effects were applicable to the clad carbon steel nozzles and manway forgings.

t The safe ends of the full-penetration welded nozzles were either Alloy 600 or forged stainless steel fabricated from wrought austenitic stainless steel. For the forged austenitic stainless steel safe ends, the staff agreed that loss of material (both intemal and extemal) was not an applicable aging effect because of the low generci corrosion rate of austenitic stainless steels. The caff also agreed that thermal embrittlement was not a significant concem for components fabricated from wrought material and, therefore, was not an aging management concem for license renewal.

The B&WOG identified cracking as an applicable aging effect for the stainless steel safe end attacnment welds and other dissimilar metal welds relating to safe ends. This potential cracking can occur in the HAZ of a weld where a susceptible microstructure may exist as a result of being exposed to welding temperatures. In contrast, the B&WOG asserted that general SCC of stainless steel safe ends was not an applicable aging effect because of reactor coolant water chemistry controls. The staff agreed with 'ne B&WOG assessment that cracking in the HAZ of stainiess , teel safe end attachment welds and dissimilar metal welds were an applicable aging effect. However, the staff disagreed with the B&WOG assertion that general SCC of stainless e, teel safe ends was not an applicable aging effect. In this case, the staff asserted that the water chemistry control program was scrying as an aging management program to inhibit cracking of the safe ends, and should not be used to justify cracking as a non-plausible aging effects for SCC. Therefere, the staff deterrr bed SCC to be an applicable aging effect that needed to be addressed for license renews rid made this Open item No. 2 in the draft SER, dated September 13,1996.

In response to the draft SER, Open item No. 2, the B&WOG maintained their original position, but agreed to consider SCC of stainless steel safe ends an applicable aging effect and credited the primary water chemistry controls as an aging management program to manage SCC of 10

)

I 4 I stainless steel safe ends. The staff agrees that a chemistry control program can maintain an environment where parameters, such as oxygen and chloride concentration, are kept within acceptible limits to preclude general SCC of stainless steel. Therefore, Open item No.2 was resolved.

For Alloy 600 safe ends, the B&WOG asserted that loss of material due to corrosion was not an applicable aging effect. The staff agreed with this assertion because Alloy 600 is a nickel based material which h corrosion resistant. In cc .trast, B&WOG asserted that Alloy 600 was susceptible to cracking. Industry experience had shown a potential for primary water stress corrosion cracking (PWSCC) of Alloy 600 components to occur when high tensile stress, and a susceptible microstructure were simultaneously present. Although Allay 600 safe ends were typically heat treated to reduce residual stresses, the use of heat treatment was not considered sufficient to preclude cracking of Alloy 600 welded joints and base metal at or near HAZs where the stresses and microstructure susceptible to cracking may exist. The staff therefore concurred with B&WOG's assertion that cracking of the welded joints and base metal at or near HAZs was an applicable aging effect for Alloy 600 safe ends.

The B&WOG asserted that the stainless stael the mal sleeves for the full-penetration welded nozzles were not susceptible to any aging effects. However, in RAI No.13, the staff noted that thermal sleeves do experience age-related degradation and fai!ure. In its response to RAI No.

13, dated February 20,1996, the B&WOG stated that, based on industry experience, the thermal sleeves that have experienced degradation and failure were limited to high-pressure injection / makeup (HPl/MU) nozzles. They further explained that those thermal sleeves extending into a pulsating flow stream and, therefore, were subject to vibratory loading. According to the B&WOG, this vibratory loading not only caused wear, but also led to a situation where the thermal sleeves were exposed to altemating hot and cold fluid, thereby resulting in thermal fatigue. Although HPl/MU and pressurizer thermal sleeves were installed using similar methods, the pressurizer thermal sleeves do not extend into a flow stream. Thus, the B&WOG contended that the pressurizer thermal sleeves were not subject to the vibratory loadings an : resultant thermal transient effects described as the root cause of the HPl/MU thermal sleeve failure. In addition, the B&WOG was unable to find any industry operating experience of loose thermal sleeves or cracking in the welds of the pressurizer nozzles or safe ends. Therefore, the staff concurred that a specific aging management program for the stainless steel pressurizer thermal sleeve full-penetration welds was not required. However, the staff noted that the stainless steel thermal sleeves were made of similar materials and exposed to the same environmental conditions as the stainless steel safe ends. The staff considered the primary water chemistry control program to be applicable to all the stainless steel components within the scope of BAW-2244. Therafore, the staff asserted that the stainless steel thermal sleeves required the same reactor coolant water chemistry controls to manage the potential aging effects of general SCC.

3.2.2.2 Pressure-Retaining Partial-Penetration Welded Nozzles Pressure-retaining partial-penetration welded nozzles included the thermowell, vent, and sampling nozzles, as well as the sampling and level sensing nozzles at ANO-1 and CR-3. The B&WOG noted that industry experience has shown that through-wall cracking can occur in these locations. Also, Alloy 600 partial-penetration nozzles were susceptible to cracking as a result of PWSCC in welded joints or the base metal near the HAZ. The staff agreed that cracking was an applicable aging effect for the components identified above. The partial-penetration welds between the heater bundle diaphragm plate and the heater sheath or sleeve will be addressed in Section 3.2.3 of this SER.

11 t

g 1 A

3.2.2.3 Pressure-Retaining Dissimilar Metal Welds in Vessel Nozzles Pressure-retaining dissimilar metal welds in vessel nozzles included the surge and spray nozzles, the pressure relief nozzles, and the sampling ed level sensing nozzles at ONS-1, -2 and -3 and TMl-1. These nozzles were fabricated from ci::d carbon steel with either stainless steel or Alloy '

600 safe ends attached with Alloy 82/182 weld material. The B&WOG asserted that pressure-retaining dissimilar metal welds were susceptible to cracking as a result of PWSCC in welded joints or the bcse metal near the HAZ. The staff agreed with this auessment based on the applicable discussions regarding cracking of stainless steel cladding and Alloy 600 welds in Sections 3.2.1 and 3.2.2.1, respectively.

1 3.2.3 Other Pressure-Retaining Components Other pressure-retaining components included the carbon steel manway cover and the pressure retaining components associated with the heater bundles.

The manway cover was fabricated of SA-516 Grade 70 carbon steel plate, and was protected from general corrosion on the internr i surface by the presence of a stainless steel manway insert and a manway gasket. The extemal surface, however, was susceptible to corrosion from leakage of boric acid onto the extemal carbt,n steel surface. The staff agreed that a loss of material was an applicable aging effect for the extemal surface of the manway cover.

In RAI No.15, the staff noted that the failure of the manway gasket could result in general corrosion of the manway cover bolt holes and the manway carbon steel in the area where the carbon steel manway cover and the stainless steelinsert interface, in the response to RAI No.15, dated February 20,1996, the B&WOG stated that the potential existed for the loss of material from the underside of the carbon steel manway cover and the mating surface of the manway forging. Should the gaskei fail, the intemal surface of the carbon steal manway including the bolt holes would be exposed to a corrosive environment and, therefore, would be susceptible to loss of material resulting from boric acid wastage. The low alloy steel bolts would also be susceptible to a loss of material as a result of being exposed to this environment. The staff agreed with the B&WOG assessment that loss of material caused by boric acid wastage on the manway cover surfaces and manway bolt holes was an applicable aging effect should the manway gasket fail. The staff also agreed with the assessment that the carbon steel manway forging external surfaces and the area of interface between the carbon steel and stainless steel insert were also susceptible to loss of material under these same conditions.

The pressure-retaining items of the heater bundles included the stainless steelimmersion heater sheaths and end plugs, the stainless steel or Alloy 600 heater bundle diaphragm plates, the Alloy 600 heater sleeves (ONS-1 and TMI-1 only), and the low alloy steel heater bundle cover plates and associated welds. With regard to these components, the B&WOG indicated that stainless steel immersion heater sheaths and end plugs may be susceptible to cracking because operating conditions may result in an environment conducive to SCC. For example, energized pressurizer heaters while uncovered can cause temperatures to approach the sensitization temperature of stainless steel. If exposed to coolant that contained dissolved oxygen, halides and sulfides, after reaching sensitization temperature, the stainless steel component would be susceptible to SCC.

Industry experience indicatsa that SCC of stainless steel sheaths and end plugs was a potential aging effect. The staff agreed that cracking of stainless steelimmersion heater sheaths and end plugs was an applicable aging effect. In addition, B&WOG noted opercting experience that showed the heater sleeves and partial-penetration welds associated with the heater sleeves, and the diaphragm plate-to-shell forging seal welds could crack. The staff agreed with the B&WO'3 12

assessment that the partial-penetration welds were susceptible to cracking at the heater sheath-l to-diaphragm plate, the heater sleeve-to-diaphragm plate, the heater sheath-to-oeater sleeve, and the diaphragm pitte-to-shell forging seal welds. {

1 The staff also agreed that the low alloy steel heater bundle cover plates were susceptible to loss of material on the extemal surfaces as a result of being exposed to boric acid wastage.

3.2.4 Pressure-Retaining Bolting The pressure-retaining bolting included 2%- and 2-inch diameter SA-320 Grade L43 low alloy steel studs and nuts for the manway closures and heater bundle closures, respectively. The staff agreed with the B&WOG assessment that cracking, loss of bolt preload associated with stress relaxation, and loss of material as a result of exposure to boric acid wastage were aging effects applicable to pressure-retaining botting that should be addressed for license renewal. Stress relaxation and loss of preload may lead to a loss of mechanical closure integrity and subsequent localized leakage. This leakage, in tum, may expose the bolting materials and flange surface to an environment conducive to cracking and loss of material.

3.2.5 Integral Attachments The integral attachments were fabricated from carbon steel plate. As such, these attachments were determined to be suoject to cracking at the welded joints and the loss of material as a result of exposure to boric acid wastage caused by leakage from nearby components. Cracking of the carbon steel welded joints may result from pre-service or service-induced flaws as discussed in Section 3.2.1. Loss of material may occur as a result of carbon steel exposure to boric acid wastage from RCS leakage. The staff agreed that cracking and loss of material were potential aging effects for the pressurizer integral attachments.

3.3 Aging Management Programs As discussed in Section 2.3 of this SER, the B&WOG identified aging management programs necessary to address the effects of aging on the pressurizer componentt described in BAW-2244. This section of the SER contains the staff evaluation of the aging management programs presented in BAW-2244.

3.3.1 Industry Operating Experien' <eview In preparing BAW-2244, the B&WOG reviewed industry operating experience regarding aging effects applicable to the pressurizer for the period of extended operation. This review identified the following generic communica' ions conceming the effects of aging on the pressurizer components:

Information Notice (lN) 90-10 on cracking of Alloy 600 components (Ref. 8)

BL 82-02 on degradation of threaded fasteners in the RCS pressure boundary of PWR (Ref. 7)

BL 88-11 on the effects of thermal stratification of surge line (Ref. 9)

GL 88-05 on boric acid corrosion of carbon steel components of the RCS pressure boundary of PWR (Ref. 6)

The B&WOG indicated that the industry operating experience described in these generic communications represents relevant aging effects on the pressurizer components that should be 13

i i

P~ - addressed by aging management programs for the period of extended operation. However, the B&WOG stated that BL 8811 addresses fatigue, which was determined to be outside the scope of this report and will be addressed separately by individual applicants.

I .in BAW 2244, the B&WOG indicated that programs implemented in response to GL 88-05 that manage the effects of boric acid wastage, and BL 82-02 that manage the degradation of

. threaded fasteners associated with RCS pressure coundary components, were necessary to

' - maintain the applicable intended functions during the period of extended operationi in addition, the B&WOG indicated that licensee actions taken in response to IN 9010 provided information useful in the development of the additional sample inspection program proposed by the B&WOG.

' The staff recohnized that the B&WOG had completed a review of pressurizer-related industry

' ' operating experience. The staff found that the B&WOG had identified the appropriate generic communications relevant to pressurizer component aging effects ar'd had developed appropriate

[ aging management programs for the period of extended operation.

F

- 3.3.2 Evaluation of Aging Management Programs ,

in developing BAW 2244, the B&WOG evaluated existing aging management programs and, in general, found them to be adequate to manage the effects of aging such that the intended function of the pressurizer components will be maintained consistent with the CLB for any period of extended operation.- However, the B&WOG did identify the need to augment existing _

programs with volumatric inspection of a representative sample of small-bore nozzles and safe ends. These additional inspection activities will be developed by individual B&WOG license renewal applicants. _Upon submittal by a B&WOG applicant, the staff will review the details and adequacy of the volumetric inspection program for small-bore nozzles and safe ends.

With respect to a reactor coolant water chemistry program, the staff contends that the B&WOG sxperience, which showed no evidence of aging for several of the components discussed in BAW 2244, and the B&WOG conclusions that no aging management programs were necessary, was predicated on the existence of an effective water chemistry control program. As discussed

- in Section 3.2.2.1 of this SER, the B&WCG had areed to credit water chemistry controls for managing the effects of general SCC on stainless steel safe ends. In addition, the staff contended that crediting technical specifications primary water chemistry requirements for one component in a closed-loop system would also protect against degradation of other components made of the same material subject to same aging effects in that system. Therefore, the staff considered the primary water chemistry control program to be applicable to all the stainless steel components within the scope of BAW-2244.

In summary, the following B&WOG programs were considered necessary for managing the effects of aging to maintain the functionality of the pressurizer during any period of extended operation:

. Category 1 Components - Pressurizer Vessel ASME B&PV Code,Section XI,' ISI Examination Categories B-B and B-P Response to GL 88-05 Technical specifications primary coolant leakage limits-Technical specifications primary water chemistry control requirements 14

_ _ _ . _ . _ . - . u_-- _ _ . _ - . _ _ . _ _ ._. _ ,

4 *

-* Category 2 Components - Pressure Vessel Noules Full-Ponstration Wolded noules with a nominal pipe size (NPS) >1 o

ASME B&PV Code,Section XI, ISI Examination Categories B-D and B-P o Response to GL 88-05 o Technical specifications primary coolant leakage limits o-Technical specifications primary water chemistry control requirements Full-Penetration Wolded Noules with a NPS s 1.

o ASME B&PV Code,Section XI, ISI Examination Category B-P.

o -Response to GL 88 l o Technical specifications primary coolant leakage limits

! o

' Additional sampled volumetric impection program (to be developed) o Technical specifications primary water chemistry control requirements L -

Safe Ends of Full-Penetration Welced Noules - See Programs for Dissimilar Metal Welds Pressuro-Retaining Partial-Penetration Welded Nozzles o

ASME B&PV Code,Section XI, ISI Examination Categories B-E and B-P o Response to GL 88-05 -

o Technical specifications primary coolant leakage limits o

. Additional sampled volumetric inspection program (to be developed)

Pressure-Retaining Dissimilar Metal Welds in Vessel Nozzles with a NPS 2 4 -

o ASME B&PV Code,Section XI, ISI Examination Categories B-F and B-P o Technical specifications primary coolant leakage limits -

o Technical specifications primary water chemistry requirements Pressure Retaining Dissimilar Metal Welds in Vessel Nozzles with- NPS > 1 and-NPS < 4

,o' ASME B&PV Code,Section XI, ISI Examination Categories B-F and B-P o Technical specifications primary coolant leakage limits -

o-Technical specifications primary water chemistry requirements o

Additional sampled volumetric inspection program (to be developed)

Pressuro-Retaining Dissimilar Metal Welds in Vessel Nozzles NPS s 1 =

o ASME B&PV Code,Section XI, ISI Examination Category B-P

'o Technical specifications primary coolant leakage limits o-Additional sampled volumetric inspection program (to be developed) o Technical specifications primary water chemistry control requirements Category 3 Components - Other Pressure-Retaining items -

o- - ASME B&PV Code,Section XI, ISI Examination Category B-P 15

o Response to GL 88-05 o

. Technical specifications pnmary coolant leakage limits i o

Technical specifications primary water chemistry control requirements 1

Category 4 Components - Pressure-Retaining Bolting Pr6ssure-Retaining Bolting > 2 inches in diameter o

ASME B&PV Code,Section XI, ISI Examination Categories B-G-1 and B-P o Response to GL 88 o Response to BL 82 i o

Technical specifications primary coolant leakage limits -

Pressuro-Retaining Bolting s 2 inches in diameter o

ASME B&PV Code,Section XI, ISI Examination Categories B-G-2 and B-P o Response to GL 88-05 o Response to BL 82 02 o

Technical specifications primary coolant leakage limits

.. Category 4 Components - Integral Attachments o

ASME B&PV Code,Section XI, ISI Examination Category B-H o Response to GL 88-05 The following information was provided to describe the background of existing programs:

ASME B&PV Code Section XI ISI-In accordance with the ASME B&PV Code,Section XI, all plants have an ISI program on a 10-year interval as required by 10 CFR 50.55a(g) that was reviewed and approved by the staff. Pressurizer ISI program requirements,.

evaluation criteria, and procedures were described in Subsection lWB of Section XI.

Pressurizer examination activities were divided into " Examination Categories.": If flaws were found that exceed acceptance criteria and the flawed components were determined '

to be unacceptable for continued service,Section XI provided repair and replacement procedures. (Ref. 3)

Response to GL 88 All PWR licensees had responded to GL 88-05 by describing their programs for mitigating the effects of boric acid corrosion of extemal surfaces of carbon steel pressurizer components. The staff had reviewed the responses and had audited some licensee programs as part of operating plant activities. (Ref. 6)

- Response to BL 82 All PWR licensees had responded to the BL 82-02 describing their maintenance procedures for threaded fasteners (bolts and studs) in RCPB components. The staff had inspected licensee programs as part of operating plant activities? (Ref. 7)

Information Resultina from IN 90 In IN 90-1g, all PWR licensees were informed of the potential for PWSCC of Alloy 600 materials. All licensees were required to evaluate the applicability of information provided in generic communications to their facilities and were -

required to taken appropriate actione (Ref. 8) 16

-.~

o Technical specifications primary caalent M3a= limits - Plant-specific technical

- specsfications contaened surveillance requirements to monitor and trend primary coolant leakage, to require specific limits for identified and uniden*ified pnmary coolant leakage, and to require no leakage from the RCPB, Exceeding any of the RCS leakage limits required a licensee to enter a limiting cor,tletion of operation that may result in plant shutdown, NRC notification (10 CFR 50.72), and/or reporting (10 CFR 50.73), as appropriate.110 CFR Part 50, Appendix e, Criterion XVI required licensees to establish

- measures to assure that conditions, adverse to quality and nonconformances, wore _

promptly identified and corrected, in cases of significant conditions adverse to quality -

l

' the measures shall assure that the cause of a condition was determined and corrective actions were taken to preclude repetition.- The identification of a significant conditions adverse to quality, the cause of the condition, and the corrective action (s) taken shall be L docuemented and reported to appropriate levels of management (root cause analysis).

l- As prescribed under 10 CFR 50.73, licensees are also required to provide a description of the action (s) taken to prevent recurrence.

+

- Technical specifications crimary water chemistry recirements - Plant-specific technical specifications contained requirements to maintain primary water chemistry parameters -

(including chloride, fluoride, and oxygen concentrations) within prescribed limits.

Exceeding any of the RCS primary cociant chemistry concentration limits required a licensee to enter a limiting condition of operation and may have resulted in plant shutdown, NRC notification (10 CFR 50.72), end/or reporting (10 CFR 50.73), as appropriate.: Appendix B of 10 CFR Part 50, Criterion XVI required licensees to establish measures to assure that conditions adverse to quality and nonconformances were promptly identified and corrected. In cases of significant conditions adverse tc quality,

the measures shall assure that the cause of a condition was determined and corrective action (s) was taken to preclude repetition. The identification of a significant conditions adverse to quality, the cause of the condition, and the corrective action (s) taken shall be documented and reported to appropriate levels of management (root cause analysis). As

_ prescribed under 10 CFR 50.73, licensees are also required to provide a description of the af, tion (s) taken to prevent recurrence.

In the response to RAI No. 3, dated February 20,1996, the B&WOG identified the 1989 edition as the cmdited edition of the ASME Code,Section XI, for this topical report.' The Section XI

' examination categories relevant to this report included catsgories B-B, B-D, B-E, B-F, B-G-1, B-G-2, B-H, and B-P including mandatory Appendices Vil and Vill. The staff agreed that use of L

the examination categories of this edition was appropriate, it was the responsibility of a license renewal applicant to ensure that the requirements of the categories applicable to the pressurizer components were in accordance with the 1989 edition of the ASME Code (including Appendices

- Vil and Vill) in order to take credit for the programs delineated in BAW-2244.

i

, Specific programs for managing the effects of aging during the period of extended operation to  ;

maintain the functionality of the pressurizer vessel, pressure vessel nozzles, other pressure j

, retaining items, presure retaining bolting, and integral attachments were evaluated in Sections 3.3.2.1 through 3.3.2.5 of this SER, respectively.

~

-3.3.2.1 Pressurizer Pressure Vessel

. In BAW-2244, the B&WOG described three programs necessary to manage the effects of aging of the pressurizer pressure vessel to maintain the RCPB ~ intended function during the period of extended operation. Specifically, these programs included the ASME B&PV Code,Section XI, 17

c., -

' ISI Examination Categones B B and B-P, the program developed in response to GL 88-05, and the technical specifications primary coolant leakage limits. In addition, the staff considered the technical specifications pnmary water chemistry controls applicable to managing the effects of aging of the pressurizer pressure vessel as discussed in Section 3.3.2.

ASME B&PV Code,Section XI, Examination Category B-B included volumetric inspection of 100-percent of the shell-to-head circumferential welds every inspection interval and the inspection of 1 foot of all longitudinal shell-to-head welds at the first interval and 1 foot of one longitudinal shell-to-head weld per head at succeeding intervals. Volumetric examination indicated the presence of discontinuities throughout the volume of material and used techniques such as ultrasonics or radiography.

Eumination Category B-B inspection was conducted for all applicable welds every 10 years.

When an indication or flaw was detected, the component was evaluated according to Article  ;

IWB-3410-1 of Section XI to determine if the component was acceptable for continued service

- (that was, if the component can maintain its structuralintegrity under ASME ' Service L*:vels A, B, C, and D"). If the evaluation reveals that the flaw was unacceptable, corrective actions and root cause detem.. nations were required.

ASME Code Section XI, Examination Category B-P consisted of system leakage and hydrostatic tests. Visual (VT-2) examinations were conducted to locate evidence of leakage during the tests.

Leak testing was conducted every refueling outage prior to plant startup and hydrostatic testing was conducted every 10 years. Technical specifications primary coolant leakage limits were described in Section 3.3.2 of this SER.

The first aging effect applicable to the pressurizer pressure vessel was cracking. The B&WOG stated and the staff agreed that the regions of the vessel welded joints were potentially susceptible to cracking as was discussed in Section 3.2.1 of this SER. Therefore, an aging management program that monitors the regions of the welded joints needed to be presented as part of a license renewal application for the applicable plants.- Should cracking be detected in a welded region,10 CFR Part 50, Appendix B, Criterion XVI, " Corrective Action" required a root cause determination and corrective measures be implemented. Corrective action (s) may have involved activities eMonding beyond the welded region, as appropriate.

Operating experience showed that cracking of carbon steels, if it occurs, originated in and around welded regions. Volumetric inspection of the welded regions can detect significant cracking originating from the inside surface of the coinponent. ASME Code,Section XI, Examination Category B-B consisted of volumetric examinations that detect cracking of the weld metal materials. . On the bases of this operating experience, these periodic volumetric examinations provided reasonable assurance that cracking would be detected and ccrrective actions should be taken before cracking results in loss of the RCPB. For these reasons, the staff found that the ASME Code,Section XI, ISI Program an acceptable method of managing cracking of the pressurizer weld metal materials to ensure that the RCPB function of the pressurizer pressure vesselwas maintained during the period of extended operation.

The B&WOG also proposes a leakage detection program under Examination Category B-P. The staff found that such a program provided defense-in-depth and was complimentary to the volumetric inspection program of Examination Category B-B for ensuring that remedial actions were taken when leakage was detected, and that the possibility of cracking recurrence was minimized. The staff noted, however, that leakage detection alone was not an acceptabb aging management program to maintain the RCPB function of the pressurizer vessel. The staffs 18 r

w

0 .

i concem was that partial through-wall cracks, which were not self revealing because they may not be leaking, may not have the structuralintegrity to ensure the RCPB function of the pressurizer vessel for all design load conditions.

The second aging effect applicable to the pressurizer vessel was loss of material from extemal surfaces. The B&WOG identified the boric acid wastage surveillance programs implemented by licensees in response to GL 88-05 as being necessary to manage the potential loss of material from the extemal surfaces of the susceptible carbon steel and low-alloy steel pressurizer components. In particular, GL 88-05 requested that licensees provide assurance that they have implemented a program to address the corrosive effects of RCS leakage at limits less than those specified by the technical specifications. Briefly, the program described in GL 88-05 included determining potential leakage locations, establishing procedures for locating small coolant leaks, implementing methods for conducting visual examinations, performing evaluations, and taking appropriate corrective actions when leakage was detected to prevent recurrence. On the basis of the above discussion and operating experience with implementation of GL 88-05, the staff found that the commitments made by the B&WOG to continue to implement their responses to GL 88-05 were adequate to manage loss of material from the extemal surfaces of the pressurizer vessel for the period of extended operation.

3.3.2.2 Pressurizer Vessel Nozz!es The B&WOG described five basic programs necessary to manage the effects of aging of pre:surizer nozzles to maintain the intended function of the RCPB during the period of extended operation. Specifically , these programs included the ASME B&PV Code,Section XI, ISI Examination Categories B-B, B-D, B-E. B-F, and B-P, the programs developed in response to GL 88-05, the technical specifications primary coolant leakage limits, the technical specifications primary water chemistry requirements, and an additional sample volumetric inspection program (that is to he developed).

3.3.2.2.1 Full-penetration Welded Nozzles As discussed in Section 3.2.2.1 of this SER, full-p' itration welded nozzles were susceptible to two aging effects; the first was cracking and the second was loss of material.

- For full-penetration nozzles with a NPS of >1, the B&WOG identified the ASME Code Section XI ISI program, the Examination Categories B-D and B-P, and the technical specifications RCS leakage limits as programs necessary to manage cracking at the welded joints to maintain the RCPB during the period of extended operation. In addition, the staff considered the technical specifications primary water chemistry controls applicable to managing the effects of aging of the full-penetration welded nozzles as discussed in Section 3.3.2. Large nozzles attached to the vessel with full-penetration welds include the surge nozzle, the spray nozzle, and the pressure relief nozzle. The manway forging was also attached with a full-penetration weld.

ASME Code,Section XI, Examination Category B-P consists of system leakage and hydrostatic tests. Examination Category B-P was described in Sectlon 3.3.2.1 of this SER. Technical specifications RCS leakage limits were described in Section 3.3.2 of this SER.

ASME Code,Section XI, Examination Category B-D included a volumetric examination of the nozzle-to-vessel welds and nozzle inside radius section performed at every inspection interval for full-perWration welds with a NPS 21. Volumetric incpection of the welded regions can be used to detect significant cracking originating from the inside surface of the component, as well as at 19

w,-

the noule to-vessel welded joints. Should cracking be detected,Section XVI, "Correctiva Action,"in Appendix B tc 10 CFR Part 50 required that the licensee performs a root cause determination and implement corrective measures.-

i Similar to the staff's determination in Section 3.3.2.1 of this SER, the staff found that these periodic examinations provide reasonable assurance that cracking would be detected and corrective actions should be taken before loss of the RCPB. For these reasons, the staff found that ASME Code,Section XI, ISI Examination Category B-D was an acceptable method of managing cracking of the pressurizer full-penetration welds to maintain the RCPB function during the period of extended operation.

The manway welds were exempt from Examination Category B-D volumetric examination because the manway welds were not subject to loadir.g stresses attributed to attachment piping.

As a result, the aging effects on the other full-penetration attachment welds %bject to volumetric inspection would be considered bounding. Additionally, the staff found that Examination Category B-P, technical specifications leaktge limits, and technical specifications primary water chemistry requirements provided defense-in-depth and were acceptable to complement the volumetric inspection program of Examination Category B-D.

For full-penetration noules with a NPS si, the B&WOG described the three programs necessary to manage the effects of cracking at the welded joints te maintain the RCPB during the period of extended operation. Specifically, these programs include ASME Code,Section XI, ISI program Examination Category B-P, technical specifications RCS leakage limits, and a program of additional volumetric inspections to tx performed on a sampling basis. In addition, the staff considers the technical specifications primary water chemistry controls applicable to managing the effects of aging of the full-penetration welded noules with a f0PS $ 1 as discussed in Section 3.3.2. Small nonles attached to the vessel with full-penetration welds includes the -

sampling and level sensing nonles at ONS-1, -2 and -3 and TMI-1. Full-penetration welded noules with a NPS s1 were exempt from ASME Code,Section XI, ISI Examination Category B-D.

The B&WOG stated that for full-penetration welded nonles with a NPS si, leakage attributed to cracking would not be of sufficient magnitude to comprise the integrity of the RCPB. Leakage would be minor and apparent during leakage / pressure testing in accordance with ASME Code,Section XI, ISI Examination Category B-P and would result in appropriate corrective actions.

However, leakage detection would not provide adequate assurance that the integrity of the pressure boundary would be maintained under design loading conditions. Consequently, the B&WOG proposed an additional program for renewal, similar to that described for small-bore piping in BAW-2243 (Ref. 4).

The B&WOG defined small-bore nonles as those, including safe ends with a NPS of < 4 and fabricated from stainless steel, Alloy 600, and stainless steel clad carbon steel. In response to RAI No. 21, dated February 20,1906, the B&WOG stated that some additional sample inspections of small-bore noules were appropriate to provide reasonable assurance that the intended function will be maintained during the period of extended operation. In response to RAI 21, the B&WOG committed on behalf of the participating B&W license renewal applicants, that additional volumetric inspections for small-bore nonles will be performed on a sampling basis. The criteria for these inspections will be submitted by the B&WOG GLRP member plants when they submit their applications for staff review and approval.

20

The staff found the commitment to perform additional volumetric inspections of small-bore nczzles and safe ends associated with the pressurizer acceptable for license renewal. The staff based this finding on the presumption that such inspections would provide assurance that potential cracking of small-bore nozzles snd rafe ends would be detected, and corrective action (s) could be taken to ensure that the small-bore nozzles and safe ends associated with the pressurizer can perform theirintended functions during the period of extended operation. The plant-specific applicants would delineate the details of the additional sample inspection program, including the acceptance criteria, for additionalinspection of small-bore nozzles and safe ends. l These inspection activities would be subject to NRC review and approval when the B&WOG GLRP member plants submit their renewal applicatiorts.

The staff found that the ASME Code,Section XI, ISI Examination Categories B-P, in conjunction with technical specifications RCS leakage limits, technical specifications primary water chemistry controls, and a commitment to develop and implement an additional volumetric inspection program to be adequate to manage cracking of small-bore nozzles with a NPS s;1 during the period of extended operation. However, the staff will have to review the details of the additional volumetric inspection program for acceptability when submitted by the applicant.

The second aging effect applicable to full-penetration welds was extemal loss of material caused by boric acid wastage of carbon steel surfaces. Loss of material on extemal carbon steel surfaces can be attributed to leakage of primary coolant onto the extemal surfaces of the nozzles. The B&WOG identified the boric acid wastage surveillance commitments implemented by licensees in response to GL 88-05 as necessary for managing *Se potentialloss of material on the extemal surfaces of the full-penetration welded nozzles. Det' i of the program elements were documented in Section 3.3.2.1 of this SER. With a ration similar to that provided in Section 3.3.2.1 of this SER, the staff found that the elements o s programs developed in tesponse to GL 88-05 were adequate for manag% the loss o .terial on the extemal surfaces of full-penetration welded nozzles within the scope of this repn Juring the period of extended operation.

, 3.3.2.2.2 Safe Ends Associated with Fuil-Penetration Welded Nozzles The B&WOG stated and the staff concurred that cracking, primarily in and around the welded regions, was a possible aging effect associated with the stainless steel safe ends of the surge and pressure relief nozzles, and the Alloy 600 safe ends on the spray nozzle, and the sampling and level sensing nozzles at ONS-1, -2 and -3 and TMI-1, as discussed in Section 3.2.2.1 of this SER. The aging management programs used to manage the effects of cracking I'lating to safe ends were evaluated in Section 3.3.2.2.4 of this SER.

3.3.2.2.3 Pressure-retaining partial-penetration Welded Nozzles BAW-2244 identified three programs necessary to manage the effects of aging associated with pressure-retaining partial-penetration welded nozzles to maintain the RCPB during the period of extended operation. Specifically, these programs included the ASME Code,Section XI, ISI Examinttion Categories B-E and B-P, a boric acid wastage program, and technical specifications RCS leakage limits. The B&WOG has also identified the volumetric inspection program (consisting of inspections on a sampling basis as discussed in Section 3.3.2.2.1 of this SER) for small-bore piping and safe ends as applicable to the components discussed in this section.

The B&WOG stated that the pressure-retaining pcdial-penetration welded nozzles attached to the vessel consisted of the thermowells, the vent and sampling nozzles, and the sampling and 21

0 8 i

level sensing nozzles at ANO-1 and CR-3. These nozzles were all fabricated from Alloy 600 and had an NPS s1%. Cracking of the welded joints was most likely to occur in the weld or adjacent base metalin or near the HAZ. Industry experience had shown that through-wall cracking and  !

subsequent detectable leakage can occur in these iocations. In addition, the staff considers the l

stainless steelimmersion heater sheath-to-heater bundle diaphragm plate and heater sheath-to- '

heater sleeve and Alloy 600 heater sleeve-to-heater bundle diaphragm plate (ONS-1 and TMbi) welds to be partial-penetration welded nozzles. Furthermore, since these nozzles had an NPS s4, they would be included in the B&WOG's proposed sample volumetric inspection program to manage cracking of small-bore nozzles.

ASME Code,Section XI, ISI Examination Category B-E included a visual (VT-2) examination of 25-percent of the partial-penetration welded vessel nozzles at every inspection interval. The staff notod that ASME Code,Section XI, ISI Excmination Cctegory B-E contained a provision for examining pressurizer heater penetration welds which was not explicitly discussed in BAW-2244.

In the response to RAI No. 23, dated February 20,1996, the B&WOG stated that the requirement to examine the pressurizer heater penetration welds was not appibable to the B&W de:ign because Examination Category B-E concems pressure-retaining partial-panetration welds associated with nozzles in vessels and they do not consider the heater penetrations to be nozzles. The staff disagreed with this assertion. The B&W pressurizer heaters were inserted through holes in the pressurizer heater bundle diaphragm plates, and the heater sheaths (or heater sleeves at ONS-1 and TMI-1) were attached to the diaphragm plates on the inside by partial-penetration welds. The staff did not believe that the B&W heater penetrations were sufficiently different from other vendor's designs to warrant their exclusion from the requirements of Examination Categcry B-E. B&W heaters were mounted horizontally on the diaphragm plates inserted through the side of the pressurizer shell, while other vendor designs mount the heaters 1

vertically, inserted through the bottom of the pressurizer.

Examination Ca'egory B-E explicitly stated that the pressurizer heater partial penetration welds were to be examined. An apparent inconsistency exists in that some B&WOG plants were performing the inspection, while others were not. Operating experience has shown that pressurizer heater partial-penetration welds may be susceptible to cracking. The staff contended that the pressurizer heater partial-penetration welds perform a pressure-retaining function and, therefore, were subject to the requirements set forth in ASME Code,Section XI, 'GI Examination Category B-E. In accordance with 10 CFR 54.30, the staff had determined that this matter was a current operating plant issue and, therefore, will be addressed for disposition under the current operating license. In addition, the staff noted that, unlike the diaphragm plate-to-heater belt forging seal welds, the heater sheath-to-heater bundle diaphragm plate welds, the heater sleeve-to-heater bundle diaphragm plate welds, and the heater sheath-to-heater sleeve partial-penetration welds were designed to assume the structural loads imparted by the immersion heaters themselves. The industry has experienced cracking of these welds, in the response to RAI No. 25, February 20,1996, the B&WOG stated that the configuration of the individual immersion heater penetrations would limit leakage and prevent catastrophic failure of the pressure boundaryif cracking should occurin the heater sheath-to-heater bundle diaphragm plate welds, the heater sleeve-to-heater bundle diaphragm plate welds, or the heater sheath-to-heater sleeve partial penetration welds. However, the staff believed that the pressurizer partial-penetration heater sheath-to-heater bundle diaphragm plate welds, heater sleeve-to-heater bundle diaphragm plates welds and heater sheath-to-heater sleeve welds (ONS-1 and TMI-1) should be subject to Examination Category B-E inspection. Furthermore, the staff did not believe that visualinspections for leakage of the extemal areas of the heater bundle penetration assemblies alone provided adequate assurance that cracking will be detected.

22

Consequently, a more intrusive inspection program was necessary to manage potential cracking of these wolds. In Open item No. 3 of the draft SER, dated September 13,1996, the staff stated that it would consider accepting an aging management program that included the ASME Code,Section XI, ISI Examination Category B-E, together with an inspection program consisting of surface examinations of these partial-penetration welds to manage the effects of cracking during the period of extended operation for these welds. The criteria for these inspections would be developed at a later date and subject to staff approval. In their response to Open item No. 3, dated November 22,1996, the B&WOG stated that the inspections at each of the member plants were based on the requirements of Examination Category B-P and were identical to or more rigorous than the requirements of Examination Category B-E. In addition, the B&WOG stated that requirements to perform a surface examination of the wolds would result in a hardship that was not commensurate with an increased levelin safety. The B&WOG deferred resolution of this issue, includir.g the decision regarding the performance of a surface examination, to the plant specific renewal applications. This is Open item No. 2 for this SER.

ASME Code,Section XI, ISI Examination Category B-P consisted of system leakage and hydrostatic tests, as described in Section 3.3.2.1 of this SER, and the related technical specifications RCS leakage limits were described in Section 3.3.2. The boric acid wastage program contains elements that address observation of possible coolant leakage that manifests itself in the formation of boric acid crystalline buildup as discussed in Section 2.3.2. In addition, if leakage was detected,10 CFR Part 50, Appendix B, Sectio.7 XVI, " Corrective Action," required licensees to perform a root cause determination and implement corrective measures.

l With the exception of Open item No. 2 noted above, the staff found the B&WOG proposal l

adequate for managing cracking of the small-bore nozzles associated with pressure-retaining l partial-penetration welds on the pressurizer during the period of extended operation. Specifically, l B&WOG proposal included developing and implementing a volumetric inspection program (consisting of inspections on a sampling basis) for small-bore nozzles, in conjunction with ASME Code,Section XI, ISI Examination Categories B-E and B-P, and the boric acid wastage program.

3.3.2.2.4 Dissimilar Metal Pressure-Retaining Welds in Nozzles and Safe Ends The B&WOG identified two programs necessary to manage the effects of aging associated with pressure-retaining dissimilar metal welds in vessel nozzles and safe ends with a NPS 24 and a NPS >1 and <4 to maintain the RCPB during the pef.od of extended operation. Specifically, these programs included the ASME Code,Section XI, ISI Examination Categories B-F and B-P, technical specifications RCS leakage limits in addition, the staff considered the technical specifications primary water chemistry controls applicable to managing the effects of aging of the dissimilar metal pressure-retaining welded in nozzles and safe ends as discussed in Section 3.3.2.

Pressure-retaining dissimilar metal welds in vessel nozzles with a NPS 24 included the welds between the clad carbon steel surge nozzle and its stainless steel safe end and the clad carbon steel spray nozzle and its Alloy 600 safe end. Pressure-retaining dissimilar metal welds in vessel nozzles with a NPS >1 and <4 included the welds between the clad carbon steel nozzles and the stainless steellong weld necks of the pressure relief nozzles. "Ihe aging effect appiicable to the welds of these nozzles and safe ends was cracking attributable to PWSCC.

ASME Code,Section XI, ISI Examination Category B-F for pressure-retaining dissimilar metal welds in vessel nczzles and safe ends with a NPS 24 consisted of both surface and volumetric examinations performed at the nozzle-to-safe end welds at every inspection interval. Flaws 23

detected during examinetion were evaluated using the acceptance criteria defined in ASME Code,Section XI, Subsection lWB-3514 to determine if continued operation was acceptable or if ,

corrective actions must be taken. By contrast, ASME Code,Section XI, ISI Examination Category B-F for pressure-retaining dissimilar metal welds in vessel no zles and long weld necks {

with a NPS >1 and <4 consisted of a surface cxamination only (volumetric examination is not included) performed at the nonle-to-long weld neck welds at every inspection interval.

In the response to RAI No. 21, dated February 20,1996, the B&WOG also committed to a new program to manage the effects of aging on small-bore nonles and safe ends, for the extended period of operation. As discussed in Section 3.3.2.2.1 of this SER, the B&WOG propos(d an additional sample volumetric inspection program to be developed and submitted by the applicant, which will delineate the acceptance criteria for inspection of small-bore nonles and safe ends fabricated from stainless steel, Alloy 600, and stainless steel clad carbon steel. The new program included an additionalinspection of welded nonles with a NPS >1 and <4. In response to RAls Nos. 21 and 22, the B&WOG also committed to develop inspection criteria using information gathered and an increased awareness of Alloy 600 cracking as a result of PWSCC described in IN 90-10, " Primary Water Stress Corrosion Cracking of inconel 600" (Ref.8). This inspection criteria will be used in any additional aging management programs for small-bore nonles and safe ends. Cracking of Alloy 600 safe sads precipitated the need for an examination of the effects associated with PWSCC, as discussed in IN 90-10. As a rosult, B&WOG plants have catalogued all locations of Alloy 600 within the RCS, along with material susceptibility, operating environment, and component stresses for these locations.

For pressure-retaining dissimilar metal welds in vessel noules and safe ends with a NPS s i, the B&WOG identified three programs necessary to manage the effects of aging to maintain the RCPB during the period of extended operation. Specifically, these programs included the ASME Code,Section XI, ISI Examination Category B-P, technical specifications RCS leakage limits, and a sampled volumetric inspection program (to be developed). An additional description of this new program was provided in Section 3.3.2.2.1 of this SER. Pressure-retaining dissimilar metal welds in vessel nonles and safe ends with a NPS si included the welds between the carbon steellevel sensing nonles and sampling nonles and their Alloy 600 safe ends at ONS-1, -2 and

-3, and TMI-1. The aging effect applicable to the welds of these nonles was cracking in and around the welded joints of Alloy 600 material.

Cracking of the welded joints that have propagated to the point of through-wall penetration and subsequent leakage can also be detected by examination using ASME Code,Section XI, ISI Examination Category B-P, Examination Category B-P consisted of system leakage and hydrostatic tests, including visual (VT-2) inspection, as described in Section 3.3.2.1 of this SER.

Technical specifications RCS leakage limits were also described in Section 3.3.2 of this SER.

The staff found that the programs proposed by the B&WOG were adequate to manage cracking of the pressure-retaining dissimilar metal welds in the vessel nonles and safe ends within the scope of this report during the period of extended operation. Specifically, these programs included ASME Code,Section XI, ISI Examination Categories B-F and B-P, in conjunction with technical specifications RCS leakage limits, technical specifications primary chemistry controls, and a commitment to develop and implement an additional inspection program consisting of volumetric examination on a sampling basis of small-bore nonles with a NPS s4. However, the staff will review the details of the new program for acceptability when submitted by the individual applicant.

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3.3.2.3 All Other Pressure Retaining items The B&WOG identified three programs necessary to manage the effects cf aging of all other pressurizer pressure-retaining components within the scope of the report to maintain the RCPB during the period of extended operation. Specifically, these programs included the ASME Code,Section XI, ISI Examination Category B-P, the program devaloped in response to GL 88-05, and technical specifications RCS leakage limits in addition, the staff considered the technical specifications primary water chemistry controls applicable to managing the effects of aging of all other pressurizer pressure-retaining components as discussed in Section 3.3.2. ISI Examination Category B-P, c6nsisted of system leakage and hydrostatic tests as described in Section 3.3.2.1 of this SER. Technical specifications leakage limits were descr; bed in Section 3.3.2 of this SER.

The items addressed in this section included the manway cover, the heater bundle diaphragm plates, heater bundle cover plates, welds associated with these components, and immersion heaters, sheaths, sleeves, and end plugs.

The manway cover was fabricated from carbon steel and susceptible to loss of material resulting from boric acid corrosion. The B&WOG identified the boric acid wastage surveillance programs committed to by licensees 1,1 response to GL 88-05 as necessary for managing the potential loss of material of carbon steel components during the period cf extended operation. Details of the program elements were described in Section 3.3.2.1 of this SER. Similar to the rational discussed in Sections 3.3.2.1 and 3.3.2.3 of this SER, the staff found the commitments made by licensees in response to GL 88-05 to be acceptable for managing the loss of material from the carbon steel manway cover during the period of extended operation.

Programs to n j the effects of boric acid corrosion for the bolted manway connection included ASME Code.Section XI, ISI Program (Examination Category B-G-1), the boric acid wastage program implemented in response to GL-88-05 (Ref. 6), and the program developed for the pressure retaining botting in response to BL 82-02 (Ref. 7), as described in section 3.3.2.4 of this SER.

In addition, to preclude the effects of boric acid corrosk,n from affecting the ability of the surrounding components to perform their intended function (s), the B&WOG proposed that pressurizer integrity and leakage control be addressed to minimize the potential of beric acid corrosion from affecting component intended function (s). A program to monitor for leakage and initiate corrective actions when it occurred (which may include gasket replacement) would provide additional assurance that applicants can ma5tain the pressurizer's intended function.

Such programs included ASME Code,Section XI, ISI Program (Examination Category B-P),

system leakage and hydrostatic testing, and technical specifications leakage limits. .herefore, the staff concluded that the programs proposed by the B&WOG to manage the effects of aging relating to boric acid corrosion resulting from leakage were adequate for the bolted manway connection, and provided reasonable assurance that the pressure boundary intended function would be maintained. Specifically, these programs included ASME Code,Section XI, ISI Program (Examination Category B-G-1), the boric acid wastage program implemented in response to GL-88-05 (Ref. 6), and the program developed for the pressure retaining bolting in response to BL 82-02 (Ref. 7), as well as a leakage monitoring program comprised of ASME Code,Section XI, ISI Program (Examination Category B-P), and technical specifications RCS leakage limits.

The heater bundle diaphragm plates were fabricated from Alloy 600 at ONS-1 and TMI-1, and from stainle ss steel at ANO 1, CR-3, ONS-2 and ONS-3. The B&WOG stated that the heater bundle diaphragm plates were susceptible to cracking at or near the diaphragm-to-heater belt 25

0 e forging seal welds. The seal welds were not credited for structuralintegrity and used for sealing purposes only. The heater bundle diaphragm plates were secured by the cover plate boiting and form the bolted connection structural pressure boundary that was analyzed to support the design loads associated with this penetration assembly. Cracking of the seal welds could result in leakage and degradation of the bolted connection (i.e., the heater bundle cover plates, diaphragm plate bolts / studs, and pressurizer vessel) because of boric acid corrosion, and c ' tid threaten the pressure boundary function.

Programs to manage the effects of boric acid corrosion for the diaphragm plate bolted connection included ASME Code,Section XI, ISI Examination Category B-G-1, the program (s) for the pressure retaining bolting developed in response to BL 82-02, and the program (s) for boric acid wastage developed in response to GL 88-Of in addition, the programs addressing boric acid corrosion leakage must be considered. Leakage resulting from a through-wall crack of seal welds was limited by the close tolerances and tortuous path that the leaktge would have to take through the heater bundle penetration assembly. However, it should be addressed before the effects of boric acid corrosion become apparent. This will preclude the effects of boric acid wastage from affecting the surrounding components ability to perform their intended functions.

Accordingly, a program that monitors for leakage and provides measures to correct the leakage when it occurs, would provide additional assurance that the pressure boundary intended function would be maintained. The B&WOG proposed a leakage detection program comprised of ASME .

Code,Section XI, ISI Examination Category B-P, and technical specifications RCS leakage l hmits.

, The staff concluded that the aging management programs proposed by the B&WOG were l adequate to manage the effects of boric acid corrosion resulting from leakage. Specifically, these programs included ASME Code,Section XI, ISI Examination Category B-G-1 and the program (s) developed in response to BL 82-02 specifically for the pressure retaining bolting, and a boric acid wastage program (response to GL 88-05) together with a leakage monitoring program comprised of ASME Code,Section XI, ISI Examination Category B-P, syvem leakage and hydrostatic testing, and technical specifications RCS leakage limits. Together these programs would adequately manage the effects of aging for the bolted heater penetration assembly, thereby providing reasonable assurance that the pressure boundary intended function will be maintained.

The heater bundle cover plates were fabricated from carbon steel and were determined to be susceptible to loss of material resulting from boric acid corrosion. The B&WOG identifie d the boric acid wastage surveillance programs committed to by licensees in response to G'. 88-05 as necessary to manage the potentialloss of material of carbon steel components during the period of extended operation. Details of the program elements were described in Section 3.3.2.1 of this SER. Similar to the rationale discussed in Sections 3.3.2.1 and 3.3.2.3 of this SER, the staff found the commitments made by licensees in response to GL 88-05 to be acceptable for managing loss of material for the carbon steel heater bundle cover plates during the period of extended operation.

The immersion heaters (sheaths and end plugs) were fabricated from stainless steel and were determined to be susceptible to cracking in the heater sheaths and end plu0s. The B&WOG stated that, should cracking occur in the heater sheath itself or in the end plug, the presence of the hermetic sealin the receptacle end, welded to the heater sheath (extemal to the pressurizer) would act as a secondary pressure boundary. The hermetic seal was designed for the heater sheath design pressure. However, should leakage occur,Section XVI, " Corrective Action,"in Appendix 8 to 10 CFR Part 50 would require a root cause determination of the leakage source 26

0

• o-and corrective actions. These corrective actions would prevent leakage from corroding the surrounding components. The staff agreed that ASME Code,Section XI, ISI Examination Category B-P, together with the implementation technical specifications RCS leakage limit were adequate to manage the effects of aging on the immersion heater sheaths and ends plugs for the period of extended operation.

3.3.2.4 Pressure Retaining Bolting The B&WOG identified the ASME Code,Section XI, ISI Examination Categories B-G-1, B-G-2, and B-P, responses to GL 88-05, BL 82-02, and technical specifications RCS leakage limits as programs necessary to manage the effects of aging of the pressurizer pressure-retaining bolting components to maintain the RCPB during the period of extended operation.

ASME Code,Section XI, ISI Examination Category B-P, included system leakage and hydrostatic tests as described in Section 3.3.2.1 of this SER. Technical specifications leakage limits were described in Section 3.3.2 of this SER. ISI Examination Category B-G-1 and B-G-2 were defined as follows:

Examination Size Cateoory Component Description (inches) Examination B-G-1 Pressure retaining >2 Volumetric and visual, (VT-1) of all bolting bolts, studs, nuts, bushings, and flange surfaces B-G-2 Pressure retaining bolting s2 Visual (VT-1) of all bolts, studs, and i nuts Examination Categories B-G-1 and B-G-2 were required to be conducted every 10 years.

l Volumetric examination may be performod using ultrasonic or radiographic techniques to look for subsurface flaws. Flaws were evaluated using the acceptance criteria defined by ASME Code,Section XI, Subsection IWB-3515. Subsection IWB-3515 also provided acceptance criteria for evaluating condition or surface flaws discovered during visual (VT-1) examination. The components examined using Examination Category B-G-1 were the manway fasteners. The components examined using Examination Category B-G-2 included the heater bundle cover plate fasteners. V;sual VT-1 examination was conducted to determine the condition of a given component or surface, including such conditions as cracks, wear, corrosion, erosion, or physical damage. Flaws detected using Examination Category B-G-2 may be acceptable for continued service if they meet the standards in ASME Code,Section XI, subsection IWB-3517.

The first and second applicable aging effects were cracking of the bolting and loss of bolting preload, each of which could result in loss of closure integrity. The staff found that the ASME Code,Section XI bolting examination proposed by the B&WOG was adequate to manage potential cracking and loss of preload. Mechanical closure integrity could also be monitored through Examination Category B P system leakage and hydrostatic tests, and technical specifications RCS leakage limits. Additional discussion of the programs necessary to maintain the pressure boundary function of the manway and diaphragm plate bolted connections was documented in Section 3.3.2.3 of this SER.

The third applicable agrg effect was loss of material of carbon and low-alloy steel botting. The B&WOG stated that the boric acid wastage surveillance programs committed to by licensees in 27

F 4 l ..

6*  :

response to NRC GL 88-05 was necessary in managing the potential loss of material of carbon and low-alloy steel botting during the period of extended operation.

In addition, licencees have programs that respond to BL 82-02, " Degradation of Threaded -

Fasteners in Reactor Coolant Pressure Boundary of PWR Plants." BL 82-02 indicated that there should be additional dements of bolting maintenance programs, such as maintenance procedures for threaded fasteners and the establishment of quality assurance measures for use of lubricants and sealants associated with threaded fasteners. The actions taken in response to BL 82-02 included the development and implementation of procedures that included personnel training, installation and maintenance procedures, and measures that would ensure the selection of lubricants and sealant compounds that would minimize fastener susceptibility to SCC. The

- B&WOG indicated that the response to BL 82-02 was necessary for license renewal.

The staff found the commitments made by licensees in response to GL 88-05 and BL 82-02 to be acceptable for managing the aging effect of loss of material for carbon and low alloy steel bolting within the scope of this report. These commitments provided reasonable assurance that the integrity of the manwayflosure and the heater bundle cover plate bolted closures will be maintained during the period of extended operation.

3.3.2.5. Intearal Attachments in BAW-2244, the B&WOG identified the ASME Code,Section XI, ISI Examination Category B-H and the program developed in response to GL 88-05 as necessary programs to manage the effects of aging of the pressurizer integral attachments during the poriod of extended operation.

The B&WOG determined that the integral attachment's welded regions are subject to cracking and their carbon steel material surface is susceptible to loss of material due to boric acid

. corrosion resulting from leakage of neighboring components.

ASME Code,Section XI, ISI Examination Category B-H includes volumetric or surface examination of essentially 100 percent of the attachment-to-vessel welds. Flaws detected during examination are evaluated using the criteria set forth in lWB-3516 and appropriate corrective actions must be taken. In addition,10 CFR Part 50, Appendix B, Section XVI, " Corrective

~

Action," requires licensee to perform a root cause determination and implement corrective measures.

- BAW-2244 contains a description of the boric acid wastage surveillance programs, committed to by licensees in response to GL 88-05, as necessary for managing the potential loss of material associated with carbon steelintegral attachments during the period of extended operation.

However, in RAI No. 26, the staff noted that the commitments made in response to GL 88-05.

may not be applicable to the presturizer integral supports. In the response to RAI No. 26, dated February 20,1996, the B&WOG stated that although GL 88-05 addressed RCS boundary materials, the programs established at participating licensee sites included provisions for tracing coolant leakage to its source, the identification and evaluation of carbon steel components exposed to the leskage, and the implementation of applicable corrective actions.

The staff found that the programs committed to by licensees were adequate to manage the effects of cracking and loss of material associated with the pressurizer integral attachments

- within the scope of this report throughout the period of extended operation. Specifically, these programs included the ASME Code,Section XI, ist Examination Categories B-H in conjunction with the commitments made by licensees in response to GL 88-05 as clarified by the B&WOG in response to RAI No. 26.

28

O

• 6 4 CONCLUSIONS The staff has reviewed the subject B&WOG topical report, BAW-2244, and additionalinformation submitted by the B&WOG. On the basis of this review, the staff concludes that, subject to approval of the additional volumetric inspection program committed to by the B&WOG and upon resolution of the open items discussed in Section 4.2, BAW-2244 provided an acceptable demonstration that the aging effects within the scope of the topical report will be adequately managed such that there is reasonable assurance that the pressurizer will perform its intended function in accordance with the CLB during the period of extended operation. Any B&WOG GLRP member plant may reference BAW 2244 in their license renewal application to satisfy the requirements of 10 CFR 54.21(a)(3) for provioing a demonstration that the effects of aging on the pressurizer components within the scope of this report will be adequately managed. The staff also concludes that, subject to completion of the actions items described in Section 4.1 and resolution of the open items of Section 4.2, referencing BAW-2244 in a license renewal application will provide the staff with sufficient information to make the necessary findings required by 10 CFR 54.29(a)(1) for components within the scope of this report.

4.1 Renewal Applicant Action items Before licensees participating in the B&WOG GLRP can reference BAW-2244 in their license renewal application, these applicants must complete the action items listed below.

(1) When incorporating the B&WOG topical report in its renewal application, the license renewal applicant is to verify that its plant is bounded by the topical report. This includes confirming that the design of the pressurizer is consistent with that described in the report such that no important pressurizer components exist that have not been addressed in the report. )

(2) The renewal applicant is to commit to programs identified as necessary in the report to manage the effects of aging on the functionality of the pressurizer.

(3) A summary description of these programs is to be provided in the license renewal final safety analysis report supplement in accordance with 10 CFR 54.21(d).

(4) Any deviations from the aging management programs described within this report as necessary to manage the effects of aging during the period of extended operation to maintain the functionality of the pressurizer or other information presented in the report, such as materials of construction and edition of the ASME section XI code (including mandatory appendices), will have to be identified by the renewal applicant and evaluated on a plant-specific basis in accordance with 10 CFR 54.21(a)(3).

(5) Since the B&WOG defers the development of details of the additional sample volumetric inspection program of small-bore nozzles and safe ends to the renewal applicant 5

referencing this topical report, the renewal applicant will have to provide details of the additional sample inspection program in its renewal application for staff review and approval.

(6) Since the B&WOG elected to exclude TLAAs applicable to the pressurizer from the scope of the topical report and indicated that they will be resolved on a plant-specific basis, any renewal applicant referencing this report will have to evaluate TLAAs applicable to the 29 1

4 pressurizer in its renewal application in accordance with the requirements of 10_CFR 54.21(c).

4.2 ' Open items Before licensees participating in the B&WOG GLRP can reference BAW-2244 in their license renewal application, these applicants must resolve the open items listed below.

(1)- . Cracking of Stainless Steel Cladding inside the pressurizer vessel (discussed in Section 3.2.1 of this SER)

The staff notes that cracking in cladding could potentially propagate into the base metal  !

material and should be oodressed by an aging management program. Industry experience at one site has shown that this is a potential aging effect. The staff maintains

that cracking of the stainless steel is a potential aging effect that must be addressed by _

an aging manegement program for the period of extended operation. A program to =

provide a reasonable demonstration of the integrity of the pressurizer claoding could be a one-time inspection for license renewal. The inspection should include the cladding and any attachment welds to the cladding. The additional inspection would provide information on the condition of the cladding or, if cracking is discovered, the condition of the undertying base metal as a result of the cracked cladding. The staff notes that the inspection technique chosen (e.g. visual, surface,'or volumetric) must be capable of -

determining the condition of the cladding and must be submitted for staff review and

- approval. Without such additional aging management program activities, the staff cannot conclude that all aging effects applicable to the pressurizer vessel cladding have been adequately addressed by the aging management programs delineated in BAW 2244.

(2)- A

' ging management of pressurizer heater penetration welds (discussed in Section 3.32.2.3 of this SER)

The staff regards the provision for examination of pressurizer heater penetration welds in ASME Code,Section XI, ISI Examination Category B-E as applicable to pressurizer heater partial-penetration welds. The B&WOG considers the Examination Category B-E requirement not applicable to the B&W design because Examination Category B-E concems pressure-retaining partial-penetration welds in vessels. The B&WOG stated

that, "Although the ' Parts Examined' listing under item B4.20 of Examination Category B-E uses the term ' Heater Penetration Welds,' the ' Extent and Frequency of Examination' specifically requires only 'All Nozzles' to have examination." "There are no heater

- penetration nozzles or pressure-retaining heater nozzle partial-penetration welds in the vessels of the B&W pressurizer design."

The staff disagrees with the B&WOG assessment. The B&W pressurizer heaters are inserted through holes in the pressurizer heater bundle diaphragm plates and the heater sheaths (or heater sleeves at ONS-1 and TMI-1) are attached to the diaphragm plates on the inside by partial-penetration welds. The staff does not believe that the B&W heater

- penetrations are sufficiently different from other vendor designs, except that the B&W.

heaters are mounted horizontally on the diaphragm plates inserted through the side of the pressurizer shell, while other vendor designs mount the heaters vertically, inserted through the bottom of the pressurizer, in addition, Examination Category B-E explicitly--

states that the pressurizer heater penetration welds are to be examined. Therefore, the

. staff considers the pressurizer heater partial-penetration welds pressure-retaining, and 30

< . l subject to the requirements set forth in ASME Code,Section XI, ISI Examination Category B E. Operating experience has also shown that pressurizer heater partial-penetration -

wolds are susceptible to cracking. To provide reasonable assurance that cracking of the heater penetration welds and the heater sheath-to sleeve welds (ONS-1 and TMI 1) will be managed during the period of extended operation, the staff is requesting an additional, more intrusive inspechon technique. Specifically, the staff will consider ASME Code,Section XI, ISI Examination Category B-E together with an inspection program consisting of surface examinations (the criteria and technique of which would be developed at a later date and subject to staff approval) for the pressurizer partial-penetration heater sheath-to-heater bundle diaphragm plate welds, heater sleeve-to-heater bundle diaphragm plates welds and heater sheath-to-heater sleeve welds acceptable for managing the effects of cracking for the period of extended operations.

Primary Contributor: Christopher M. Regan 31 m

0

• e.

Appendix l- List of References

1. Part 54, " Requirements for Renewal of Operating Licenses for Nuclear Power Plants,"

Federal Reaister. Vol. 60, No. 88, May 8,1995, pp. 2246122495.

2. BAW 2244, " Demonstration of the Management of Aging Effects for the Pressurizer,"

Babcock & Wilcox Owners Group, August 1995.

3. Boiler and Pressure Vessel Code,Section XI, " Rules for Inservice inspection of Nuclear Power Plant Components," The American Society of Mechanical Engineers 1989 edition.

4. BAW 2243, " Demonstration of the Management of Aging Effects for the Reactor Coolant System Pipirig," Babcock & Wilcox Owners Group, March 1995.

5. Safety Evaluation by the Office of Nuclear Reactor Regulation conceming BAW-2243,

" Demonstration of the Management of Aging Effects for the Reactor Coolant System Piping," March 21,1996.

6. Generic Letter 88-05, " Boric Acid Corrosion of Carbon Steel Reactor Pressure Boundary Comoonents in PWR Plants," NRC, March 17,1988.

7. Balletin 82-02, " Degradation of Threaded Fasteners in the Reactor Coolant Pressure Boundary of PWR Plants," NRC, June 2,1982.

8. Information Notice 9010, " Primary Water Stress Corrosion Cracking (PWSCC) of Inconel 600," NRC, February 23,1990.

i 9. Bulletin 88-11, " Pressurizer Surge Line Thermal Stratification," NRC, December 20,1988.

32

e-b Appendix ll- List of Correspondence 1.

Letter to U.S. NRC, attention D.M. Crutchfield, from D.K. Croneberger of B&WOG Generic License Renewal Program, dated August 31,1995, transmittal of,

" Demonstration of the Management of Aging Effects for the Pressurizer," Topical Report BAW.2244, March 1995.

2. Letter to D.K. Croneberger of B&WOG Generic License Renewal Program from John P.

Moulton of NRC dated December 13,1995, " Request for Additional Information Regarding the B&W Owners Group Topical Report BAW-2244."

3. " Summary of Meeting Between the U.S. NRC and B&WOG representatives to discuss their proposed responses to the staffs Request for AdditionalInformation on the Pressurizer Topical Report," dated February 1,1996, prepared by John P. Moulton of the NRC for a meeting between the NRC and B&WOG held on January 24,1996.

4. " Summary of Meeting Between the U.S. Nuclear Regulatory Commission and B&WOG Representatives to Discuss their future Reactor Vessel Topical Report," dated February 15,1996, prepared by John P. Moulton of the NRC for a meeting between the NRC and B&WOG held on February 6,1996.

5.

Letter from D.K. Croneberger of B&WOG Generic License Renewal Program, dated February 20,1996, transmittal of B&WOG responses to the staffs December 13,1995, RAls on B&WOG Topical Report BAW 2244.

6.

Letter from D.K. Croneberger of B&WOG Generic License Renewal Program, dated April 17,1996, transmittal of modification to B&WOG responses contained in their February 20,1996, response.

7.

Letter from D.K. Croneberger of B&WOG Generic License Renewal Program, dated May 1,1996, transmittal of modification to their April 17,1996 letter.

8. Letter from D. Firth of B&WOG Generic License Renewal Program, dated November 22,1996, transmittal of response to DSER open issues.

33 l

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