ML20199L279

Topical Rept Evaluation Concerning BAW-2244, Demonstration of Management of Aging Effects for Pressurizer. on Basis of Review,Staff Concludes That BAW-2244 Provided an Acceptable Demonstration That Aging Effects Will Be Adequately Managed

ML20199L279
Person / Time
Issue date:	11/26/1997
From:	NRC (Affiliation Not Assigned)
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ML20199L253	List: ML20199L248 ML20199L279
References
PROJECT-683 NUDOCS 9712010369
Download: ML20199L279 (37)

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i FINAL SAFETY EVALUATION REPORT CONCERNING BABCOCK & WILCOX OWNERS GROUP TOPICAL REPORT No. BAW 2244 "DEMONSTRATICN OF THE MANAGEMENT OF AGING EFFECTS FOR THE PRESSURIZER" PROJECT No. 683 C PDR k

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TABLE OF CONTENTS I

t i I NTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 '

2. 2 Effects of Aging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.3 Aging Management Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . s

> 3 STAF F EVALU ATI ON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1 Components and lntended Functions . . . . . . . . . . . . , . . . . . . . . . . . . . 4 3.1.1 Co m po ne nt s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1.2 Intended Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0 3.2 Effects of Aging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.2.1 Pressurizer Pressure Vessel . . . . . . . . . . . . . . . . . . . . . . . . 0 3.2.2 Pressure Vessel Nozzles , . . . . , . . . . . . . . . . . . . . . . . . . . . 10 3.2.3 Other Pressure Retaining Components . . . . . . . . . . . . . . . . 13 '

3.2.4 Pressure Retaining Bolting . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.2.5 Integral Attachments . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . 14 3.3 Aging Management Programs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

' Industry Operating Experience Review . , , . . , . . . . . . . . . . 14 3.3.1 3.3,2 Evaluation of Aging Management Programs . . . . . . . . . . . . . . 15 4 C O N C L U S I O N S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 4.1 Renewal Applicant Action items . . . , . . . . . . . . . . . . . . . . . . . . . . . 31 4.2 Ope n iterr s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , 32 Appendix l - List of References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 Appendix il - List of Correspondence . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 1

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1 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 fixed period not to exceed 40 years. Before expiration of the current operating term, the NRC 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 Federa/ Register on May 8,1995 (Ref.1),

sets forth the requirem3nts for renewing operating licenses for commercial nuclear power phnts. l 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 desenbe 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; q. an applicant demonstrate that the effects of aging will be adequately managed so that the intwed 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 Dabcock & Wilcox Owners Group Topical Report BAW 2244 Dy 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 Evaluation 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 additional informatien (RAls). B&WOG representatives responded in wnting to the staff's RAls and provided further clarification in a number of public meetings held with the staff. Appendix 11 of this SER is a list of correspondence that documents the RAls, meeting surnmaries, 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 staff's evalustion, a v ription of the action items identifieo by the B&WOG and documented in BAW-2244, an jescription of the open items identified by the staff during the evaluation of 1

0 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.

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.

2

SUMMARY

OF TOPICAL 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 mernber plants:

. Arkansas Nuclear One, Unit 1 (ANO-1)

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

. 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 press.urizer-related 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 Vassel (B&PV) Code,Section XI (Ref. 3). These TLAAs will be evaluated on c plant-specific basis.

2.1 Components and Intended Functions The B&WOG topical mport addressed the effects of aging on B&W pressurizers. Section 2 of BAW-2244 containet.1 a detailed description of the pressurizer and its components, and the matenals used in their construction. Within the report, the pressurizer components were divided into the fol!owing five component categories:

(1) pressurizer pressure vessel (2) pressurizer nozzlec (3) other pressure retaining items (4) pressure-retaining bolting (5) integral attachments As reported in BAW-2244, the pressuis 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. Oth?r

,sssure-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).

2

- 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, 2.2 Effects of Aging The B&WOG topical report, BAW4244, evaluated the applicability of the following aging effects on pressurizer components:

. cracking (initiation and growth)-

. loss of fracture toughness e loss of material

. loss of mechanical closure integrity (for bolted connections)

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

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

Comoonent Category Potential Effects of Aaing Pressurizer Vassel Cracking of welded joints Loss of material (external surfaces)

Pressurizer Vessel Cracking of welded joints Nozzles I.oss of material (external surfaces)

Cracking at or near welds Other Pressure- Loss of material i Retaining items Cracking at or near welds Cracking of Base Metal Pressure-Retaining Loss of material

- Bolting Cracking loss of preload/ closure integrity Integral Attachments Cracking of welded joints Loss of material (extemal surfaces) 2.3 Aging Management Programs Table 4.1 in BAW-2244 t,ummarized the specific programs used at ANO, ONS, and TMI 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 (;SI) Program (Ref. 3)

. response to Generic Letter (GL) 88-05 (Ref. 6) on boric acid corrosion 3

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. . response to Bulletin (BL) 82-02 (Ref. 7) on fastener degradation

. information developed from Information Notice 9010 on Alloy 600 cracking (Ref. 8)

. 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.

. 3 STAFF EVALUATION The staff reviewed BAW 2244, as well as additional information 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 ag ag management programs, as described within the report, could adequately manage ths affects 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 r;id not review information relatbg to the individual B&WOG-GLRP plants to determine whether the report accurately reflected their respective pressurizer designs and included all constituent components. Corsequently, when referencing this report, in order to demonstrate that they can adequately man age the aging effects relating to their pressurizer during the period of extended operation, each p articipating B&WOG member plant must demonstrate that its pressurizer design is consistent with BAW 2244. This demonstration, that an applicant's pressurizer design is consiste'1t 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 determineo by the B&WOG to be within the scope of BAW-2244, and the intended function associated with these components.

3.i.1 Components As summarized in Section 2 of this SER, BAW-2244 divided the pr'ssurizer 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 botting, 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 4

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 vent and sample nozzles, pressure relief nozzles, spray nozzle, thermowells, level sensing nozzles, and the surge nozzle and thermal sleeve. The pressure retaini..g 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 bolting for the three heater bundle cover plates. The integral attachments in Category 5 were comprised of the pressurizer vessel support bracket assemblies. The welds within the scope of BAW-2244 were associated 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 pre. 3urizer heaters, internal surge line components, the spray head and internal spray line components, heater bundle assembly components, vessel lifting lugs, internal maintenance equipment support plates, and internal ladder. Section 312 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(e)(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 the acceptability of excluding certain pressurizer compenents 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 presserizer 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 c 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&WOG 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 5

- 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 t.'.aff agreed with the conclusion that the gasket did not require an aging management review; however, the staff conclusin 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 gas'.et exists to minimize leakage and is not solely responsible for providing pressure boundary or supporting a structural load.

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 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 enntrol for regulated events (except ANO-1) as defined by 10 CFR 54.4(a)(3)."

The B&WOG provided additional clanfication on the component intended functions when they stated that the " pressurizer supports the pressure boundary by the integrity c'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 renewal included 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 heatert were not subject to an aging management review because their function was accomplished through a change of configuration or properties. 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 j

consistent with a change in configuration or properties; thus heaters should be considered active l

! components.

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. 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 component 5 Nt 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 raaintain the RCPB) met the criteria of 10 CFR 54.21(a)(1). The pressurizer heater pressure boundary was maintained by preserving the integrity of the heater sheath (or sleeves) and end caps. Therefore, the 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 niaintained by cycling the pressurizer heaters on and off and, therefore, required a change in the energized state of 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 determined that pacsive structures and components for which aging degradation is not readily monitored are these 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 control is readily monitorable through normal operating pressure and alarms, 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 internal surge hne components included the diffuser, diffuser cap, and diffuser cap support legs. The B&WOG stated that the intended function of the internal surge line components was to provide minor thermal mixing during in-surges 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 internal surge line components were not part of the RCPB. Therefore, these components were not within the scope of license renewal ano 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 head and associated internal 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 ;n 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 without scram (10 CFR 50.62), and station blackout (10 CFR 50.63).

Furthermore, the B&WOG stated that industry experience did not support a scenario in which failure of the spray head or internal spray line items leads to a loss of the pressurizer pressure 7

. boudary, Consequently, the WOG contended that such a scenario was beyond the scope of the p essurizer design anc unerwise hypothetical. The staff agreed that tho spray head and internal spray line items did not support any of the intended functions defined in 10 CFR 54.4(a) and, therefore, were not within the scope of ocense renewal.

The B&W pressurizer was designed with three heater bundle assemblies, each of which consisted of three parallel disks (two referred te as support plates, and one referred to as the diaphragm plate) drilled to hold 39 individual immersion heaters. The heater bundle assembly components included heater bundle assembly support plates, the heater bundle assembly horizontal guide plates or guide rails, and heater bundle assembly support 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. Therefore, the staff determined that these components were not within the scope of license renewal.

The vessel lifting lugs, internal maintenance equipment support plates, and the internal ladder also did not support the pressure boundary or pressure control functions, because failure of these components would not affect 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 laundary function has been extended to the seal welos located between the heater bundle diaphragm plate and the individual heater sheaths or the heater sleeves. Therefore, the staff made the determination that the O' rings between the heater bundla diaphragm plates and heater belt forgings were not within the scope of license renewal.

However, the seal welds that performed the pressurizer pressure boundary function were within the scope of license renawal.

3.2 Effects of Aging 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 (ftr 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 the 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, .he 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 Vesse!

The B&W pressurizer vessel as defined in BAW-2244 consisted of a vertical cylindrical shell with a semi-hemispherical head at both t% top and the bottom. Its dimensions were documented as 8

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. nominally 42 feet, 8.625 inches in height from top to bottom and 96.375 inches in outer 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 5125-inch carbon steel plate. 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 cracking 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 steel jointa (i.e., 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 metal welded joints were potentially susceptible to cracking. The reason for this susceptibility was that the welds contained residual welding stresses, and the associated heat affected zones (HAZ) contained a microstrt.cture 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, pro'vided that the cladding material remains intact. The reason for this was that the base metal itself 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 metal material was susceptible to age-related cracking or loss of materialif exposed to primary coolant at a result of cracking or loss of the cladding material.

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

Strict control of the cladding fabrication end 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 susceptible to cracking. For example, BAW-2244 identified a non-B&W plant that experienced numerous clao 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 e'so noted that welds used to attach items to the vesselinternal clad surfaces could potentially crack and propagate into the vessel walls. The B&WOG did not consider clad cracking an applicable aging effect. Nonetheless, 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 concerns with the integrity of the 9

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.- pressure vessel and its ability to perform its intended function under CLB design loading conditions, in a draft version of this SER, dated September 13,1996, the staff made the potential clad cracking issue Open item No.1. Specifically, the staff stated that the B&WOG must propose a 4 program to address potential cracking of the stainless steel cladding of the pressurizer 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 cladding as a prerequisite to license renewal. This inspection would provide evidence that the cladding had not experienced cracking, if a flaw wem detected, Appendix B to 10 CFR Part 50 would require a root cause determination and corrective measures.

In its responsa to this open item, dated November 22,1996, the B&WOG maintained that, although industry has experienced cracking of the cladding, the incident in question was not applicable to 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 loss 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 embnttlement.

The B&WOG indicated that the loss of base metal material from the extemal surfaces of the pressurizer as a result of boric acid wastage was an applicable aging effect. Experience has

- shown that primary coolant leakage onto the external surfaces of carbon steel components can cause boric acid corrosion that will ultimately result in loss of material. The staff agreed with the fact that the loss of base metal material from boric acid corrosion was an aging effect applicable to license renewal.

i 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 containeJ 18 penetrations. Associated nozzles were fabricated from either Alioy 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 wue 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-retaining partial-penetration welded nozzles were fabricated from Alloy 600. Pressure-retair"ng dissimilar metal welds in vessel nozzles, specifically the surge nozzle and spray 10

.- nozzle, were fabricated from clad carbon 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 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 vescel; i.e., cracking of welded joints and loss of material (external surfaces). With the exception of Open item No.1, the staff agreed that these aging effects were applicable to the clad carbon steel nozzles and manway forgings.

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 internal and external) was not an applicable eging effect because of the low general corrosion rate of austenitic stainless steels.

The staff also agreed that thermal embrittlement was not a significant concern for components fabricated from wrought material and, therefore, was not an aging management concern for license renewal.

The B&WOG identified cracking as an applicable aging effect for the stainless steel safe end attachment welds and other cissimilar metal welds relating to sate ends. This potential cracking can occur in tha 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 the B&WOG assessment that cracking in the HAZ of stainless steel 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 steel safe ends was not an applicable aging effect. In this case, the staff asserted that the water chemistry control program was serving 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. Therefore, the staff determined SCC to be an applicable aging effect that needed to be addressed for license renewal and 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 stainless steel safe ends. The staff agreed 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 effectively resolved.

For Alloy 600 safe ends, the B&WOG asserted that ioss 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 is corrosion resistant. In contrast, B&WOG asserted that Alloy 600 was susceptible ;o cracking. Industry experience had shown a potential for primary water stress corrosion cracking (DWSCC) of Alloy 600 components to occur when high tensile stress, and a 11

. susceptible microstructure were simultaneously present. Although Alloy 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 steel thermal 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 failure. 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 limitad 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 alternating 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 tnermal sleeves were not sub;ect to the vibratory loadings and resultant thermal transient effects desenbed 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 stainlecs 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 considers the water chemistry control program to be applicable to all stainless steel components within the scope of BAW-2244. Therefore, 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 we" 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.

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 and level sensing nozzles at ONS-1, -2 12

. and -3 and TMI 1. These nozzles were fabricated frorn clad 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 base metal near the HAZ. The staff agreed with this assessment based on the applicable discussions regarding cracking of stainless steel cladding and Al'oy 600 welds in Sections 3.2.1 and 3.2.2.1, respectively.

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 internal surface by the presence of a stainlet s steel manway insert and a manway gasket. The external surface, however, was susceptible to corrosion from leakage of boric acid onto the external carbon steel surface. The staff agreed that a loss of material was an applicable aging effect for the external 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 carben steelin 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 gasket fail, the intemal surface of the carbon steel manway including the bolt holes would be exposed to a corrosive environment and, therefore, would be susceptible to loss of matenal 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 steelimmersion heeter sheaths and end plugs may be susceptible to cracking because operating conditions may result in an environment conducive to SCC. For example, energized pressurizer heaterc 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 indicates 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 t.nd plugs was an applicable aging effect. In addition, B&WOG noted operating 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 13

. staff agreed with the B&WOG assessment that the partial-penetration welds were susceptible to cracking at the heater sheath to-diaphragm plate, the heater sleeve-to-diaphragm plate, the heater sheath-to-heater sleeve, and the diaphragm plate-to-shell forging seal welds.

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

3.2.4 Pressure-Retaining Botting The pressure-retaining botting included 2%- and 2-inch diameter SA-320 Grade L43 low alloy steel studs and nuts for tN manway closures and heater bundle closures, respectively. l'he

' 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 turn, may expose the bolting materiale nd 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 subject 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 weldeo 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. Le staff agreed that cracking and loss of materialwere potential aging effects for the pressurizet integral attachments.

3.3 Agina 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 components 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 Experience Review in preparing BAW-2244, ;he 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 communications conceming the effects of aging on the pressurizer components:

. Information Notice (IN) 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 (P.ef. 7)

. BL 88-11 on the effects of thermal stratification of surge line (Ref. 9; 14

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- 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 opf ating experience described in these generic communications represents relevant aging effects on the pressurizer components that should be addressed by aging management programs for the period of extended operation. However, the B&WOG stated that BL 88-11 addresses fatigus, which was determined to be outside the scope of this report and will be addressed separately by individual applicants, 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 boundary comporents, were necessary to maintain the applicable intended functions during the period of extended operation. In addition, the B&WOG indicated that licensee actions taken in response to IN 90-10 provided information usefulin the development of the additional sample inspection program proposed by the B&WOG.

The staff recognized that the B&WOG had completed a review of presserizer-related industry operating experience. The staff found that the B&WOG had identified the appropriate generic communications relevant to pressurizer component aging effects and had developed appropriate aging management programs for the period of extended operation.

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 volumetric inspection of a representative sample of small-bore nozzles and safe ends. These additionalinspection 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 experience, which showed no evidence of aging fc 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&WOG had agreed 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.

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. 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

- Tecnnical specifications primary water chemistry control requirements

. Category 2 Components - Pressure Vessel Nozzles

- Full-Penetration Welded nozzles with a nominal pipe size (NPS) >1 l

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 Welded Nozzles with a NPS s 1 o ASME B&PV Code,Section XI, ISI Examination Category B-P o Response to GL 88-05 o Technical specifications primary coolant leakage limits o Additional sampled volumetric inspection program (to be deveicped) o Technical specifications primary water chemistry control requirements

- Safe Ends of Full-Penetration Welded Nozzles - See Prcgrams for Dissimilar Metal Welds

- Pressure-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 sampbd volumetric inspection program (to be developed)

- Pressure-Retaining Dissimilar Metal Welds in Vessel Nozzles with a NPS 2 4 o ASME BF.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 16

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 prirnary water chemistry requirements o Additional sampled volumetric inspection program (to be developed)

- Pressure-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 specific *tions primary water chemistry control requirements

. Category 3 Components - Other Pressure-Retaining items o ASME B&PV Code,Section XI, ISI Examination Category B-P o Response to GL 88-05 o Technical specifications primary coolant leakage limits o Technical specifications primary water chemistry control requirements

. Category 4 Components - Pressure-Retaining Bolting

-- Pressure-Retaining Boiting > 2 inches in diameter o ASME B&PV Code,Section XI, ISI Examination Categories B-G-1 and B-P o Response to GL 88-05 o Response to BL 82-02 o Technical specifications primary coolant leakage limits

- Pressure-Retaining Botting s 2 inches in diameter o ASME B&PV Coda,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 t

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 critena, and procedures were described in Subsection IWB of Section XI.

Pressurizer exarrination activities were divided into " Examination Categories." If flaws

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- - 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) fMoonse 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 external 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)

. Resoonse to BL 82 All PWR licensees had responded to the BL 82-02 describing

" their maintenance procedures for threaded fasteners (bc4ts 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 90-19, all PWR licensees were informed of the potential for PWSCC of Alloy 600 materials. Alllicensees were required to evaluate the applicability of information provided in generic communications to their facilities and were required to taken appropriate actions. (Ref. 8)

. Technical soecifications, orimary coolant leakaae limits - Plant-specific technical specifications contained surveillance requirements to monitor and trend primary coolant leakage, to require specific limits for identified and unidentified primary coolant leakage, 3

and to require no leakage from the RCPB. Exceeding any of the RCS leakage limits required a licensee to enter a limiting condition of operation that may result in plant shutdown, NRC notification (10 CFR 50.72), and/or reporting (10 CFR 50.73), as appropriate.10 CFR Part 50, Appendix B, 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 to quality, 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 docuemented 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 action (s) taken to prevent recurrence.

. Technical soecifications crimarv water chemistrv recuirements - 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 coolant chemistry concentration limits required a licensee to enter a limiting condition of operation and may have resuned in plant shutdown, NRC notification (10 CFR 50.72), and/or reporting (10 CFR 50.73), as 4 appropriate. A. )pendix B of 10 CFR Part 50, Criterion XVI required licensoes to establish

' measures to assure that conditions adverse to quality and nonconformances were 4

promptly identified and corrected. In cases of significant conditions adverse to 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

- 18 i

.- y r-% ,-- - -- - - -. y _ +-

-- y ,

' 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 action (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 credited edition of the ASME Code,Section XI, for this topical report. The Section XI examination categories relevant to this report included categories 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 the examination categories of this edition wss 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 thts 1989 edition of the ASME Code (including Appendices Vil and Vill) in order to take credit for the programs delineated in BAW 2244.

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 retaining items, pressure retaining botting, 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, ISI Examination Categories 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 primary 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 i foot of alllongitudinal 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 usE.d techniques such as ultrasonics or radiography.

Examination Category B B inspection was conducted for all applicable weids every 10 years.

When an indication or flaw was detected, the component was evaluated according to Article IWB-34101 of Section XI to determine if the component was acceptable for continued service (that was, if the component can maintain its structural integrity under ASME " Service Levels A, B, C, and D*). If the evaluation reveals that the flaw was unacceptable, corrective actions and root cause determinations 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 we e described in Section 3.3.2 of this SER.

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- 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 potentiaPy susceptible to cracking as was discussed in Section 3.2.1 cf 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 extending beyord 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 component. 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 operatii,g experience, these periodic volumetric examinations provided reasonable assurance that cracking would be detected and corrective actions should be taken before cracking results in loss of the RCPB. For these reasons, the staff fcund 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 vessel was 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 acceptable aging management program to maintain the RCPB function of the pressurizer vessel. The staff's concern was that partial through-wall cracks, which were not self revealing because they may not be leaking, may not have the structural integrity 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 external surfaces. The P&WOG identified the boric acid wastage surveillance programs implemented by licensees in response to GL 88-05 as being necessary to manage the potentialloss of material from the external surfaces of the susceptible carbon steel ano 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 pessurizer vessel for the period of extended operation.

3.3.2.2 Pressurizer Vessel Nozzles 20

• The B&WOG described five basic programs necessary to manage the effects of aging of pressurizer 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 fimits, the technical specifications primary water chemistry requirements, snd an additional sample volumetric inspection program (that is to be developed).

3.3.2.2.1 Full-penetration Welded Nozzles As discussed in Section 3.2.2.1 of this SER, full-penetration 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 hydroctatic

• nsts. Examination Category B-P was described in Section 3.3.2.1 of this SER. Technical vecifications 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-penetration welds with a NPS 21. Volumetric inspection of the welded regions can be used to detect significant cracking originating from the inside surface of the component, as well as at the nozzle-to-vessel welded joints. Should cracking be detected,Section XVI, " Corrective Action,"in Appendix B to 10 CFR Part 50 required that the licensee performs a root cause detennination and implement corrective measures.

Similar to the staff's determination in Section 3.3.2.1 of this SER, the staff found that these periodic examinations provide reasonable assurar,ce tMt cracking would be detected a d c.orrective actions should be taken before loss of tne 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 loading stresses attributed to attachment piping.

As a result, the aging effects on the other full-penetration attachment welds subject to volumetric inspection would be considered bounding. Additionally, the staff found that Exarnination Category B-P, technical specifications leakage limits, and technical specifications primary water 21

i chemistry requirements provided defense-in-depth and v'ere acceptable to complement the volumetric inspection program of Examination Category L D.

For full-penetration nozzles with a NPS si, the B&WOG desciit*d the three prograrm necessary to manage the effects of cracking at the welded joints to maintain the RCPB during the period of extended operation. Specifically, these programs include ASME Code,Section XI, ISI program Excmination Category B-P, technical specifications RCS leakage limits, and a program of addttional volumetric inspections to be 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 nozzles with a NPS < 1 as discussed in Section 3.3.2. Small nozzles attached to the vessel with full-penetration welds includes the sampling end level sensing nozzles at ONS-1, -2 and -3 and TMI-1. Full-penetration wclded nozzles 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 nozzles 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 appropriaie corrective actions.

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

The B&WOG defined small-bore nozzles 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 20,1996, the B&WOG stated that some additional sample inspections of small bore nozzles 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 nozzles 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.

The staff found the commitment to perform additional volumetric inspections of small-bore nozzles 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 and safe ends would be detected, and corrective action (s) cculd be taken to ensure that the small-bore nozzles and safe ends associated with the pressurizer can perform their intended 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 additional inspection of small-bore nozzles and safe ends.

These inspection activities would be subject to NRC review and approval when the B&WOG GLRP member plants submit their renewal applications.

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 22

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 si 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 externalloss of material caused by boric acid wastage of carbon steel surfaces. Loss of material on external carbon steel t urfaces can be attributed to leakage of primary coolant onto the external surfaces of the nozzles. The B&WOG identified the boric acid wastage surveillance commitments implemented by licersees in response to GL 88-05 as necessary for managing the potential loss of material on the extemal surfaces of the full-perd. ration welded nozzles. Details of the program elements were documented in Section 3.3.2.1 of this SER. With a rationale similar to that provided in Section 3.3.2.1 of this SER, the staff found that the elements of the programs developed in response to GL 88-05 were adequate for managing the loss of material on the extemal surfaces of full-penetration welded nozzles within the scope of this report during the period of extended operation.

3.3.2.2.2 Safe Ends Associated with Full-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 3.2.21 of this SER. The aging management programs used to manage the effects of cracking relating 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 prograrns included the ASME Code.Section XI, ISI Examination 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 t 'ed that the pressure-retaining partial-penetration welded nozzles attached to the vessel consisted of the thermowells, the vent and sampling nozzles, and the sampling and level sensing nozzles at ANO-1 and CR-3. These nozzles were all fabricated from Alloy 600 and had an N ?S 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 detectabfe leakage can occur in these locations. In addition, the staff considers the stainless steel immersion 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 TMI-1) welds to be partial-penetration welded nozzles. Furthermore, since these 23

nozzles had an NPS 54, 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 noted that ASME Code,Section XI, ISI Examination Category B-E contained a provision for examining pressurizer heater penetration welds which was not explicitly discussed in CAW-2244. In the response to RAI No. 23, dated February 20,1996, the B& WOC stated that the requirement to examine the pressurizer heater penetration welds was not applicable to the B&W i

design because Examination Category B-E concerns pressure-retaining partial-penetration 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 prr ssurizer 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 Category B-E. B&W heaters were mounted horizontally on the diaphragm plates z

inserted through the side of the pressurizer shell, while other vendor designs mount the heaters vertically, inserted through the bottom of the pressurizer.

Examination Category 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 g contended that the pressurizer heater partial-penetration welds perform a pressure-retaining L function and, therefore, were subject to the requirements set forth in ASME Code,Section XI, ISI 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 tc .nssume 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 boundary if cracking should occur in 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 external areas of the heater bundle penetration assemblies alone provided adequate assurance that cracking will be detected. Consequently, a more intrusive inspection program was necessary to manage potential cracking of these welds. 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 24

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 core rigorous than the requirements of Examination Category B-E. In addition, the B&WOG stated that requirements to perform a surface examination of the welds would result in a hardship that was not commensurate with an increased levelin safety. The B&WOG deferred resolution of this issue, including the decision regarding the performance of a surface examination, to the plant spe 'ific 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 9ER, 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 Section XVI, " Corrective Action," required licensees to perform a root cause determination and implement corrective measures.

With the exception of Open item No. 2 noted above, the staff found the B&WOG proposal adequate for managing cracking of the small-bore nozzles associated with pressure-retaining partial-penetration welds on the pressurizer during the period of extended operation.

SpecificQ B&WOG proposalincluded developing and implementing a volumetric inspection program pnsisting 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 tne period of extended operation. Specifically, these programs included the nSME 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 wlth 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 thc stainless steellong weld necks of the pressure relief nozzles. The aging effect applicable to the welds of these nozzles and safe ends was cracking attributable to PWSCC.

25

ASME Code,Section XI, ISI Examination Category B-F for pressure-retaining dissimilar metal welds in vessel nozzles 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 detected during examination were evaluated using the acceptance criteria defined in ASME Code,Section XI, Subsection IWB-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 nozzles and long weld necks with a NPS >1 and <4 consisted of a surface examination only (volumetric examination is not included) performed at the nozzle-to-fong 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 nozzles and safe ends, for the extended period of operation. As discussed in Section 3.3.2.2.1 of this SER, the B&WOG proposed 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 nozzles and safe ends fabricated from stainless steel, Alloy 600, and stainless steel clad carbon steel. The new program included an additionalinspection of welded nozzles 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 desenbod 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 nozzles and safe ends. Cracking of Alloy 600 safe ends precipitated the need for an examination of the effects associated with PWSCC, as discussed in IN 90-10. As a result, B&WOG plants have catalogued alllocations 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 nozzies and safe ends with a NPS s1, 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 lin,its, 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 nozzles and safe ends with a NPS s1 included the welds between the carbon steellevel sensing nozzles and sampling nozzles and their Alloy 600 safe ends at ONS-1, -2 and -3, and TMI-1. The aging effect applicable to the welds of these nozzles 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 nozzles and safe ends within the scope of this report during the period of extended operation. Specifically, these programs included ASME Coda,Section XI, ISI Examination Categories B-F and B-P, in conjunction with 26 l

l

were found that exceed acceptance criteria and the flawed components were determined to be unacceptab!e for continued service,Section XI provided repair and replacement procedures. (Ref. 3)

. Besoonse 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)

. Resoonse 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 90-19, all PWR licensees were informed of the potential for PWSCC of Alioy 600 materials. Alllicensees were required to evaluate the applicability of information provided ia generic communications to their facilities and were required to taken appropriate actions. (Ref. 8)

. Iechnical soecifications crimary coolant leakaae limits - Plant-specific technical specifications c intained surveillance requirements to monitor and trend primary coolant leakage, to require specific limits for identified and unidentified primary coolant leakage, and to require no leakage from the RCPB. Exceeding any of the RCS leakage limits required a licensee to enter a limiting condition of operation that may result in plant shutdown, NRC notification (10 CFR 50.72), and/or reporting (10 CFR 50.73), as appropriate.10 CFR Part 50, Appendix B, 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 to quality, 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 docuemented 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 action (s) taken to prevent recurrence.

. Technical soecifications orimarv water chemistrv reauirements - 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 coolant 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), and/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 to 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 con "tions adverse to quality, the cause of the condition, and the corrective action (s) taken shall be 18

i J

I l

documented and reported to appropriate levels of management (root cause analysis).

o As prescribed under 10 CFR 50.73, licensees are also required to provide a description of the action (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 credited edition of the ASME Code,Section XI, for this topical report. The Section XI-examination categories relevant to this report included categories B-8, 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 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 4

components were in accordance with the 1989 edition of the ASME Code (including Appendices i Vil and Vill) in order to take credit for de programs delineated in BAW 2244.

Specific programs for managMg the effects of aging during the period of extended operation to maintain the functionality of the pressurizer vessel, pressure vessel nozzles, other pressure retaining items, pressure 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, ISI Examination Categories 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 primary 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 alllongitudinal 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.

Examination 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 structural integrity under ASME

• Service Levels A, B, C, and D*). If the evaluation reveals that the flaw was unacceptable, corrective actions and root cause dettsrminations 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. Techrdcal specifications primary coolant leakage limits were described in Section 3.3.2 of this SER.

19

. 1-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, Cnterion XVI," Corrective Action" required a root cause determination and corrective msasures be implemented. Corrective action (s) may have involved activities extending beyond the welded region, as appropriate.

Operating experience showed that cracking of carbc? 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 component. 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 penodic volumetric examinations provided reasc.lable assurance that cracking would be detected and corrective actions should be taken before cracking results in loss of the RCPB. For these reasons, the staff found inat 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 vessel was maintained during the period of extendeo operation.

f The li&WOG also proposes a leakage detection program under Examination Category B-P.

4 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 acceptable aging management program to maintain the RCPB function of the pressurizer vessel. The staff's concern was that partial through-wall cracks, which were not self revealing because they may not be leaking, may not have the structuralintegnty to ensure the RCPB function of the pressurizer vessel for all design !oad conditions.

The second aging effect applicable to the pressurizer vessel was loss of material from external

,F 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 potentialloss of material from the external 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 4 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, imp,ementing methods for conducting visual examinations, performing evaluations, and taking appropriate corrective actions wnen leakage was detected to prevent recurrence. On the basis of the above discussion and operatiag 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 external surfaces of the pressurizer vessel for the period of extended operation.

t 3.3.2.2 Pressurizer Vessel Nozzles 20 i

s

. - . . _ , , e, __ -

1 The B&WOG described five bas;c programs necessary to manage the effects of aging of pressurizer nozzles to maintain the intended function of the RCPB during the period of extended l operation, Specifically , these programs included the ASME B&PV Code,Section XI, ISI .

Uxamine' ion Categories B 8, B D, B E, B F, and B P, tne programs developed in response to GL 88-06, the technical specifications primary coolant leakage limits, the technical specifications primary water chemistry requirements, and an additional sample volumetric inspection program  ;

(that is to be developed). l 3.3.2.2.1 Full penetration Welded Nozzles As discussed in Section 3.2.2.1 of this SER, full penetration welded nozzles were susceptible to l two aging effects; the first was cracking and the second was loss of material. l 4 -

j For full penetration nozzles with a NPS of >1, the B&WOG identified the ASME Code Section XI i

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

' i specifications primary water chemistry controls applicable to managing the effects of aging of

• the full penetration weldad nozzles as discussed in Section 3.3.2. Large nozzles attached to the '

vessel with ful'.penetratbn welds include the surge nozzle, the spray nozzle, and the pressure relief nozzle. The mariway forging was also attached with a full-penetration weld.

ASME Code,Section XI, Examination Category B D consists of system leakage and hydrostatic te=ts. Examination Category B P was desenbod in Section 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 9xamination Category B D included a volyrpetric examination of the 1

nozzle to vessel welds and nozzle inside radius section pe: formed at every inspection interval for full penetration welds with a NPS 21. Volumetric inspection of the welded regions can be used to detect significant cracking originating from the inside surface of the component, as well as at the nozzle to vessel welded joints. Should cracking be detected,Section XVI, " Corrective Action,"in Appendix B to 10 CFR Part 50 required that the licensee performs a root cause [

' determination and implement corrective measures.

< Similar to the staffs 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

%rrective 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.

Tha maoway welds were exempt from Examination Category B D volumetric examination 4 because the manway welds were not subject to loading strest es attributed to attachment piping.

As a result, the aging effects on the other full penetration attachment welds subject to volumetric inspection would be considered bounding. Additionally, the staff found that Examination Category B-P, technical specifications leakaga limits, and technical specifications pnmary water 21 i

---,w.._ ...~,e -, , , . - . . , . . . , , , _.-_m.e.-.,--+ m.-.,.- ew-.,,m-,. . - ,-.m.-.. . , - ~...-_.,r-._,-.ro---- ,_..-.m.-, x,-... . - - ,-.v,

chemistry requirements provided defense in-depth and were acceptable to complement the

• volumetric inspection program of Examination Category B D.

For full penetiution nozzles with a NPS si, the B&WOG described the three programs necessary to manage the effects of cracking at the welded joints to maintain the RCPB during the period of extended operation. Specifically, these programs include ASME Code,Section XI, ISI progum Examination Category B P, technical specifications RCS leakage limits, and a program of additional volumetric inspections to be 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 nozzles with a NPS_< 1 as discussed in Section 3.3.2. Small nozzles attached to the vessel with full penetration welds includes the sampling and level sensing nozzles at ONS 1,-2 and 3 and TMI 1. Full-penetration welded nozzles 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 nozzles with a NPS si, !eakage 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, IS6 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 nozzles 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 20,1996, the B&WOG stated that some additional sample inspections of small-bore nozzles 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&vVOG committed on behalf of the participating B&W license renewal applicants, that additional volumetric inspections for small bore nozzles will be performed on a sampling basis. The enteria for these inspections will be submitted by the B&WOG GLRP member piar ts when they submit their applications for staff ieview and approval.

The staff found the commitment to perform additional volumetri: inspections of small bore nozzles 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 and safe ends would be detected, and corrective action (s) could be taken ta ensure that the small-bore nozzles and safe ends associated with the pressurizer can perform their intended functions during the period of extended operation. The plant specific applicants would delineate the details of the cdditional sample inspection program, including the acceptance enteria, for additionalinspection of small bore nozzles and safe ends.

These inspection activities would be subject tc 1RC review and approval when the B&WOG GLRP member plants submit their renewal appinations.

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 22

controls, and a commitment to develop and implement an additional volumetric inspection o prograir to be adequate to manage cracking of small bore nozzles with a NPS si 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 extemalloss of material caused by boric acid wastage of carbon steel surfaces. Loss of material on external carbon steel surfaces can be attnbuted to leakage of primary coolant onto the external 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 the potential loss of material on the extemal surfaces of the full-penetration welded nozzles. Details of the program elements were documented it. Section 3.3.2.1 of this SER. With a rationale similar to that provided in Section 3.3.2.1 of this SER, the staff found that the elenients of the programs developed in response to GL 88-05 were adequate for managing the loss of material on the external surfaces of full-penetration welded nozzles within the scope of this report during the period of extended operation.

3.3.2.2.2 Safe Ends Associated with Full 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 surgs and pressure relief nozzles, and the Alloy POO 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 3.2.21 of this SER. The aging management piograms used to manage the effects of cracking relating 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-retainirg partial-pen, tration welded nozzles to maintain the RCPB during the period of extended operation. Specifically, these programs included the ASME Code Section XI, ISI Examination Categories B-E and B-P, a boric acid wastage program, and technical specifications Rr',S leakage limits The B&WOG has also identified the volumetric inspection program %isisting of in:pections 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 partial-penetration welded nozzles attached to the vessel consisted of the thermowells, the vent and sampling nozzles, and the sampling and level sensing nozzles at ANO 1 and CR 3. These nozzles were all fabricated from Alloy 600 and had an NPS s 1%. 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-wnll cracking and subsequent detectable leakage can occur in these locations. In addition, the staff considers the 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 TMI 1) welds to be partial-penetration welded nozzles. Furthermore, since these 23

o 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 noted that ASME Code,Section XI, ISI Examination Category B E contained a provision for examining pressurizer heater penetration welds which was not explicitly discussed in BAW- l 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 applicable to the B&W

, design bec9use Examination Category B E concerns pressure retaining partial-penetration 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 Examinatior' Category 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 vertically, inserted through the bottom of the pressurizor.

Examination Category B E explicitly stated that the pressurizer heater partial penetration welds were to be examined. An apparent inconsistency exists iri 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, ISI 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 bundic 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.

l In the response to RAI No. 25, February 20,1996, the B&WOG stated that the configuration of the individual immersion heater penetrations would lim ! leakage and prevent catastrophic failure of the pressure boundary if cracking should occur in the heater sheath to-heater bundlo 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 bundit diaphragm plate welds, heater sleeve-to heater bundle diaphragm plates welds and heater sreath-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 external areas of the heater bundle penetration assemblies alone provided adequate assurance that cracking will be detected. Consequently, a more intrusive inspection program was necessary to manage potential cracking of these welds. 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 24

l e

included the ASME Code, Sect % VI, JSI Examination Category B-E, together with an inspection program consisting of surface oon : nations of these partial penetration welds to manage the effects of cracking during theese J of extended operation for thene welds. The criteria for these inspections would be dewaped 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 piants were based on the requirements of Examination j Category B-P and were identical to or more .igorous than the requirements of Examination f

Category B-E. In addition, the B&WOG sta%d that requirements to perform a surface examination of the welds would result in a haioship that was not commensurate with an increased levelin safety. The B&WOG deferred resolution of this issue, including the decision regarding the performance of a surface examination, to the plant speofic renewal applications.

This is Open item No. 2 for this SER.

ASME Code,Section XI, ISI Examination Category B-P consisted of systern 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, Section XVI, " Corrective Action," required licensees to perf rm a root cause determination and implement corrective measures.

With the exception of Open item No. 2 noted above, the staff found the B&WOG proposal adequate for managing cracking of the small-bore nozzles associated with pressure retaining partial-penetration welds on the pressurizer during the period of extended operation.

Specifically, B&WOG proposalincluded 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 period 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 dissimiler 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. The aging effect applicable to the welds of these nozzles and safe ends was cracking attributable to Fm/ SCC.

25

_ ~. . . . _ . . _ _ __ _

4 ASME Code,Section XI, ISI Examination Category B-F for pressure-retaining dissimilar metal welds in vessel nozzles and safe ends with a NPS a4 consisted of both surface and volumetric examinationi performed at the nozzle to-safe end welds at every inspection interval. Flaws  !

detected during examination were euluated using the acceptance criteria defined in ASME Code,Section XI, Subsection IWB 3514 to determine if continued operation was acceptable or if i l

corrective actions must be taken. By contrast, ASME Code,Section XI, ISI Examination Category B-F for pressure retaining dissimilar metal welds in vessel nozz!ts and long weld l necks with a NPS >1 and <4 consisted of a surface uxamination only (volumetric examination is not included) performed at the nozzle 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 nozzles and safe ends, for the extended period of operation. As discussed in Section 3.3.2.2.1 of this SER, the B&WOG proposed an additional sample volumetric in*pection program to be developed and submitted by the applicant, which will delineate the acceptance criteria for inspection of small bore azzles and safe ends fabricated from stainless steel, Alloy 600, and stainlecs steel clad carbon steel. The new program included an additionalinspection of welded nozzles 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 l PWSCC described in IN 9010, Primary Water Stress Corrosion Cracking of inconel 600" (Ref.8). This inspection enteria Will be tised in any additional aging management programs for small-bore nozzles and safe ends. Cracking of Alloy 600 safe ends precipitated the need for an examination of the effects associated with PWSCC, as discussed in IN 9010. As a result, j l

B&WOG plants have catalogued alllocations of Alloy 600 within the RCS, along with material susceptibility, operating environment, and component stresses for these locations.

For pressure retaining dissi ailar metal welds in vessel nozzles and safe ends with a NPS si, 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 nozzles and safe ends with a NPS si included the welds between the carbon steellevel sensing nozzles and sampling nozzles and their Alloy 600 safe ends at ONS-1, 2 and -3, and TMI 1. The aging effect applicable to the welds of these nozzles was cracking to 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 M the vvssel nozzles 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 t.onjunction with 26

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 nozzles with a NPS 54. However, the staff will review the details of the new program for acceptability when submitted by the individual applicant.

3.3.2.3 All Other Pressure Retaining items The B&WOG identified three programs necessary to manage the effects of 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 developed 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, consisted of 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. The items addressed in this section included the manway cover, the heater bundle diaphragm plates, heater bundle cover plates, wolds associated with these components, and immersion heaters, sheaths, sleeve *,, 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 in response to GL 88 05 as necessary for managing the potential loss 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 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 macway cover during the period of extended operation.

Programs to manage 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 bolting 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 bonc acid corrosion 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 boric 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 maintain 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. Tnerefore, 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 27

- - .- _--_ __ .. .. .- - - . - . =

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 botting 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 stainless 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 forging seal welds. The seal welds were not credited for structural integrity and used for sealing purposes only. The heater bundle diaphragm plates were secured by the cover plate bolting 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 could 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 88-05. 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 leakage would have to take through the heater bundle penetration arsembly. 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 leabge limits.

The staff concluded that the aging management programs proposed by the B&WOG were 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 botting, 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, system leakage and hydrostatic testing, and technical specifications RCS leakage limits. Together these programs would adequately manage the effects of agii.g for the bolted heater penetration assembly, thereby providing reasonable assurance that the pressure boundary intended funct on 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 identified the boric acid wastage surveillance prcgrams committed to by licensees in response to GL 88-05 as 28

o necessary to manage the potentialloss of material of carbon steel components during the period of extended operation. Details of the program elements were desenbed in Section 3.3.2.1 of this SER. Siniilar 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 plugs. The D&WOG stated that, should cracking occur in the heater sheath itself or in the end plug, the presence of the hermetic seat in the receptacle end, welded to the heater sheath (external to the pressurizer) would act as a secondary pressure boundary. The hermetic seal was designed for the heater sh3ath design pressure. However, should leakage occur,Section XVI, " Corrective Action."in Appendix B to 10 CFR Part 50 would require a root cause determination of the leakage source 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 specificatioris RCS leakage limit were adequate to manage the effects of aging on the immersion heater sheaths and endo 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 es described in Section 3.3.2.1 of this SER. Technical specificativns 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 Categoly Comoonent Descriotion { inches) Examination B-G 1 Pressure retaining >2 Volumetric and visual, (VT-1) of all bolting bolts, studs, nuts, bushings, cnd flange surfaces BG2 Pressure retaining botting s2 Visual (VT-1) of all bolts, studs, and nuts Examination Categories B-G-1 and B-G-2 were required to be conducted every 10 years.

Volumetric examination may be performed using ultresonic 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 IV H 3515 also provided acceptance 29

enteria 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. Visual VT-1 examination was conducted to determine the condition of a given component or surface, including such conditions as cracks, wear, corrosion, erosion, or physleal damage, Flaws detected using Examination Category B G 2 may be acceptable for continued service if they meet the ctandards 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 bss of closure integrity. The staff found that the ASME Code,Section XI botting examination proposed by the B&WOG was adequcte 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 aging 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 response to NRC GL 88-05 was necessary in managing the potentialloss of material of carbon and low alloy steel bolting during the period of extended operation.

In addition, licensees 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 elements 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 sealani 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 integnty of the manway closure ano the heater bundle cover plate bolted closures will be maintained during the period of extended operation.

3.3.2.5 Integral 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 period of extended operation.

The B&WOG determined that the integral attachments' 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.

30

l l

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 IWB 3516 and appropriate corrective actions must be taken. In addition,10 CFR Part 50, Appendix D.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 {1 by licensees in response to GL 88-05, as necessary for managing the potentialloss of material associated with carbon steelintegral attachments during the period of extended operation. l However, in RAI No. 26, the staff noted that the commitments made in response to GL 88 05 may not ce applicable to the pressuitzer 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 leakage, and the implementation of applicable corrective actions.

The staff found that the programs committed to Dy licensees were adequate to manage the effects of cracking and loss of material associated with the pressurizer integral attachments withiri the ecope of this report throughout the period of extended operation. Specifically, these programs included the ASME Code,Section XI, ISI 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.

4 CONCLUSIONS The staff has reviewed the subject B&WOG topical report, BAW 2244, and additional information 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 mana0ed 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 providing a demonstration that the effects of aging on the pressurizer components within the scope of this reoort 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 When licensees participating in the B&WOG GLRP reference BAW-2244 in their license renewal application, these applicants must address the action items listed below.

(1) The renewal applicant is to venfy that its plant is bounded by the topical report. This 31

, includes confirming that the design of the precsurizer is consistent with that described in '

e the report such that no important pressurizer components exist that have not been

addressed in the report. .

(2) T.Se renewal applicant is to commit to programs identified as necessary in the report to  ;

manage the effects of aging or'.the functionality of the pressurizer.

(3) A summary description of tnese 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 at  :

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 i 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 referencing this topical report, the renewal applicant will have to provido 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 aplicable to the pressurizer from the

! scope of the topical report arid indicated that they will be 'esolved on a plant specific basis, any renewal applicant referencing this report will have to evaluate TLAAs applicable to the pressurizer in its renewal application in accordance with the '

, requirements of 10 CFR 54.21(c).

4.2 Open items When licensees participating in the B&WOG GLRP reference BAW 2244 in their license renewal application, these applicants must address the open items listed below. ,

(1) Cracking of Stainless Steel Cladding inside the pressurizer vessel (discussed in Section 3 2.1 of this SER) 1 The staff notes that cracking in cladding could potentially propagate into the base metal ,

material and should be addressed by an aging m&nagement program. Industry experience at one site has shown that this is a potential aging effect. The staff maintains that cracking of the stainless steelis a potential aging effect that must be addressed by an aging management program for the period of extended operation. A program to provide a reasonable demonstration of the integrity of the pressurizer cladding could be a one time inspection for license renewal. The inspection should include the cledding and any attachment welds to the cladding. The additionalinspection would provide information on the condition of the cladding or, if cracking is discovered, the condition of the underlying base metal as a result of the cracked cladding. The staff notes that the 32 t

r m -,-m. . - -em<-,. . , n.w o n m m , - , - - = . .w w. . -,,,,,,e,m.,we r ,-n -.ww-y, , ..,,,i-ewr.e,s.,v w.v.wiv--- -- - . , - . - - ,w sw- . . - - - . , -

i 4

> inspection 1:chnique chos:n (o.g. visu:1, surtce, or volumItric) must be c:p ble 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) Aging management of pressurizer heater penetration welds (discussed in Section 3.3.2.2.3 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 applicat:') to the B&W design because Examination Category B E 4

concems pressure retaining partial penetration welds in vessels. The B&WOG stated l that,"Although the ' Parts Examined' listing under item B4.20 of Examination Category B 5 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 disagraes with the B&WOG assessment. The B&W pressurizer heaters are inserted through holes in tha pressurizer heater bundle diaphragm plates and the heater sheaths (or heater sleeves at ONS 1 and TMl 1) are attached to the diaphragm plates on the inside by partial-penetrat!on 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 a e mounted horizontally on the diaphragm plates inserted through the side of the pressurizer shell, while other vendor designs mount the heaters ,ertically, 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 co siders the pressurizer heater partial penetration welds pressure-retaining, and subject to the 'equirements set forth in ASME Code,Section XI, ISI Examination Category B-E. Operating experience has also shown that pressurizer heater pedW.

penetration welds are susceptible to cracking. To provide reasonable assuranc inM cracking of the heater penetration welds and the heater sheath-to siceve welds (ONS 1 and TMI 1) will be managed during the period of extended operation, the staff is requesting an additional, more intrusive inspection 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 neater sheath to-heater sleeve welds acceptable for managing the effects of cracking for the period of extended operations.

Primary Contributor: Christopher M. Regan 4

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A e

Appendix I- List of References

(

1. Part 54," Requirements for Renewal of Operating Lictnses for Nuclear Power Plants," l EndtraLReaisteI, Vol. 00, No. 88, May 8,1995, pp. 22461-22495.

i l

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 Snciety of Mechanical Engineers 1989 edition.

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

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

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

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

7. Bulletin 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.

9. Buwin 8811. " Pressurizer Surge Line Thermal Stratification," NRC, December 20, 1968.

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i I

Appendix 11 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 cf NRC dated December 13,1995,

• Request for Additional Information Regarding the B&W Owners Group Topical Report BAW 2244."

j 3. " Summary of Meeting Between the U.S. NRC and B&WOG representatives to discuss their proposed responses to the staff's Request for Additional Information 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 BaWOG Generic License Renewal Program, dated 1 t

February 20,1996, transmittal of B&WOG responses to the staff's 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, oated May 1,1996, transmittal of modification to their April 17,1996 letter.

4

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

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