ML20196J219

SER Concluding That Licensee USI A-46 Implementation Program,In General,Met Purpose & Intent of Criteria in GIP-2 & Staff Sser 2 for Resolution of USI A-46

ML20196J219
Person / Time
Site:	Millstone
Issue date:	06/30/1999
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20196J214	List: ML20196J211 ML20196J219
References
REF-GTECI-A-46, REF-GTECI-SC, TASK-A-46, TASK-OR GL-87-02, GL-87-2, NUDOCS 9907070191
Download: ML20196J219 (19)

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4- UNITED STATES j j NUCLEAR REGULATORY COMMISSION

• WASHINGTON, D.C. 2055Mm01

. . . . . ,o SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION EVALUATION OF NORTHEAST NUCLEAR ENERGY COMPANY RESPONSE TO SUPPLEMENT NO.1 TO GENERIC LETTER 87-02 MILLSTONE UNIT 2 DOCKET NO. 50-336 1.0 DACKGROUND in December 1980, the Nuclear Regulatory Commission (NRC) designated " Seismic Qualification of Equipment in Operating Plants" as Unresolved Safety Issue (USI) A-46. The safety issue of concern was that equipment in nuclear plants for which construction permit _

applications had been docketed before about 1972 had not been reviewed according to the 1980-81 licensing criteria for the seismic qualification of equipment, such as Regulatory Guide 1.100 (Reference 1), IEEE Standard 344-1975 (Reference 2), and Section 3.10 of the Standard Review Plan (NUREG 0800, July 1981) (Reference 3). To address USl A-46, affected utilities formed the Seismic Qualification Utility Group (SOUG) in 1982.

The NRC staff issued Generic Letter (GL) 87-02 " Verification of Seismic Adequacy of Mechanical and Electrical Equipment in Operating Reactors," in February 1987 (Reference 4) to provide guidance for the resolution to USl A-46. The staff concluded that the seismic adequacy of certain equipment in operating nuclear power plants should be reviewed against seismic criteria not in use when these plants were being constructed. In 1987, SQUG, representing its member utilities, committed to develop a Generic Implementation Procedure (GIP) for implementing the resolution of USl A-46. SOUG requested a deferment of the 60-day response, as requested in GL 87-02, until after the NRC issued its final safety evaluation report (SER) on the final version of the GIP.

On May 22,1992, the staff issued Supplement No.1 to GL 87-02 which transmitted its final SER (" Supplemental Safety Evaluation Report No. 2 on Seismic Qualification Utility Group's Generic Implementation Procedure, Revision 2, Supplemental Safety Evaluation Report No. 2, SSER No. 2, Reference 5") on the then final version of GIP (GIP Revision 2, as corrected on February 14,1992, or simply GIP-2, Reference 6). In the supplement to GL 87-02, the staff requested that USl A-46 licensees who are members of SOUG either provide a commitment to use both the SQUG commitments and the implementation guidance described in GIP 2, as supplemented by the staff's SSER No. 2, or else provide an alternative l method for responding to GL 87-02. In a letter dated September 21,1992 (Reference 7), the t Northeast Nuclear Energy Company (NN:ICO), the licensee for Millstone Unit 2 sad a member I of SOUG, committed to the implementation of GIP-2 for resolving USI A-46 at the Millstone 1

Enclosure 9907070191 990630 PDR ADOCK 05000336 i P PDR

2 Unit 2 plant. The NRC subsequently approved the licensee's approach and schedule in a letter dated November 20,1992 (Reference 8).

By letter dated January 22,1996 (Reference 9), tne licensee submitted a report summarizing the results of its USl A-46 implementation program, in accordance with the commitments made in its 120-day response (Reference 7) to NRC's Supplemental SER No. 2 (Reference 5). The staff reviewed the report and issued a request for additional information (RAl) on August 29, 1996 (Reference 10). The licensee subsequently submitted its response to the RAI in a letter dated January 17,1997 (Reference 11). The staff reviewed the licensee's response and determined that further information was required from the licensee in order for the staff to {

complete its review The licensee responded to the NRC's request for clarification in a letter dated February 8,1999 (Reference 12). This report provides the staff evaluation of the i licensee's USl A-46 implementation program based on the staff's review of the summary report,  ?

supplemental information and clarification provided by the licensee in response to the staff's RAls.

I 2.0 DISCUSSION AND EVALUATION The staff's reviewed the Millstone Unit 2 USl A 46 summary report (Reference 9) in accordance with the USl A-46 Action Plan, dated July 26,1994 (Reference 13). The effort consisted of a '

screening of specific sections of the licensee's program, with emphasis placed on identification 1 and resolution of outliers, i.e., equipment items which do not comply with all the screening l guidelines provided in GIP-2. The report identifies a safe shutdown equipment list (SSEL) and j contains the screening verification and walkdown of mechanical and electrical equipment. The i report also contains relay evaluations and the evaluation of seismic adequacy for tanks and heat exchangers, cable and conduit raceways, and the identification and resolution of outliers,

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including the proposed resolution schedule.

2.1 Seismic Demand Determination (Ground Spectra and in-structure Resoonse Soectral l The input ground motion for the seismic design (safe shutdown earthquake (SSE)) of Millstone Unit 2 structures founded on rock is a modified Housner spectrum with a peak ground acceleration of 0.17g for the horizontal components and a peak ground acceleration of 0.11g ,

for the vertical component. For analysis of these structures, the SSE ground motion was input j at the rock foundation level. For structures founded on compacted fill, a Newmark spectrum I with a peak ground acceleration of 0.179 for the horizontal components and a peak ground acceleration of 0.11g for the vertical component were used as the input motion (Reference 7).

The licensee used a synthetic time history with a response spectrum that corresponds to the design ground response spectrum (GRS) as input to generate in-structure response spectra (IRS) at various elevations within the structures. The staff reviewed the licensee's commitments and determined that conservative design IRS resulted from this process  ;

(Refercr,ce 8). i The licensee developed median-centered IRS for the auxiliary building (AB). The licensee submitted the details of the process for the generation of these spectra to the NRC (Reference l 14). The staff issued a supplemental safety evaluation documenting the review of these l spectra accepting the median-centered IRS generated for the AB for use in the resolution of l USl A-46 (Reference 15).

3 The licensee used conservative design IRS as the seismic demand for the reactor building (RB), the turbine building (TB), and the warehouse and median-centered spectra were used as the seismic demand for the auxiliary building (AB), the enclosure building, and the control building. The staff finds these characterizations of the input ground motions and the IRS appropriate for Millstone Unit 2 USI A-46 use because they are in conformance with GIP-2.

2.2 Seismic Evaluation Personnel A seismic review team (SRT) comprised of seismic capability engineers as defined in GIP 2 performed the screening verification, walkdown, and outlier identification. GlP-2 describes the responsibilities and qualifications of the individuals who will implement this generic procedure.

For a complete resolution of the USl A-46 issue, the seismic evaluation personnel should include individuals with sufficient exp3rtise to identify safe shutdown equipment, perform the plant walkdown and verify the seismic adequacy of equipment and cable / conduit raceway systems, and to perform the relay screening and evaluation. This involves a number of plant and engineering disciplines including structural, mechanical, electrical, system, earthquake, and plant operations. Based on the information provided in Attachment C to the seismic evaluation report and the licensee's January 17,1997, submittal (Reference 11), the staff concludes that the qualifications of the individuals responsible for implementing the resolution of the USI A-46, including the third party reviewers, meet the criteria of GlP-2 and the staff's SSER No. 2, and are, therefore, acceptable.

2.3 Safe Shutdown Path GL 87-02 specifies that the licensee should be able to bring the plant to, and maintain it in, a hot shutdown condition during the first 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> following an SSE. To meet this provision the licensee addressed in its submittal of January 22,1996 (Reference 9), the following plant safety functions: reactor reactivity control, pressure control, inventory control, and decay heat removal. The licensee identified primary and alternate safe shutdown success paths with their suppod systems and instrumentation for each of these safety functions to ensure that the plant is capable of being brought to, and maintained in a hot shutdown condition for the first 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> following an SSE. Figures 1 through 4 of the submittal provide the safe shutdown paths.

Attachment B of Reference 9 provides the SSEL.

The decay heat removal function is accomplished in two stages by secondary heat removal.

The first stage of secondary heat removal will be accomplished by automatic operation of the main steam safety valves until such time that the decay heat rate decreases to the point where atmospheric dump valves can be used. Makeup water to the steam generators will be supplied by the auxiliary feed water system (AFW) which takes suction from the condensate storage tank. The second stage of secondary heat removal will be accomplished by the operation of the shutdown cooling system, when the reactor coolant system (RCS) temperature has been reduced to 300 "F, by venting the steam generators using the atmospheric dump valves. The shutdown cooling is established by cross connecting a single low pressure safety injection (LPSI) pump to both shutdown cooling heat exchangers. Water is circulated from the RCS hot leg by the LPSI pump and through the shutdown cooling heat exchangers and back into the RCS cold legs via the safety injection lines.

The plant operating department reviewed the equipment listed in Attachment B against the plant operating procedures and operator training and concluded that the plant operating

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i procedures and operator training were adequate to establish and maintain the plant in a safe shutdown condition following an SSE.

l The staff concludes that the approach to achieve and maintain safe shutdown for the first 72 .

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hours following a seismic event is acceptable.

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2.4 Seismic Screenino Verification and Walkdown of Mechanical and Electrical Eauipment l I

The staff's evaluation focused primarily on the licensee's identification and resolution of equipment outliers. GIP-2 screening guidelines are intended to be used as a generic basis for j evaluating the seismic adequacy of equipment. If an item of equipment fails to pass these generic screens, it may still be shown to be adequate by additional evaluations.

I 2.4.1 Eauipment Seismic Capacity Comoared to Seismic Demand As a first screening guideline, the SRT compared the seismic capacity to the seismic demand for the equipment in the SSEL. In accordance with GIP-2 the seismic capacity is based on the SQUG earthquake experience data base as represented by the bounding spectrum (BS),1.5 times the BS, or the generic seismic testing data as represented by the generic equipment ruggedness spectra (GERS). The seismic demand is represented by the plant's SSE GRS and both the conservative design IRS and the median-centered IRS.

There are five GIP-2 methods for comparing equipment seismic capacity to the seismic demand. Method A.1 compares the SOUG BS to the SSE GRS. Method A.2 compares the GERS to 2.25 times the SSE GRS. Method B.1 compares 1.5 times the BS (reference spectrum (RS)) to the conservative design or to the median-centered SSE IRS. Method B.2 compares the GERS to conservative design SSE IRS. Method B.3 compares the GERS to 1.5 times the median-centered SSE IRS.

l For the USl A-46 program at Millstone Unit 2, the licensee determined the seismic capacity of j safe shutdown equipment using: 1

• Earthquake experience data with capacity defined by the SQUG BS or the SQUG RS (1.5 tim',s BS). i e Generic seismic test data which have been compiled into GERS.

• Equipment-specific seismic qualification data, or data from similar equipment.

At Millstone Unit 2, the equipment on the SSEL subject to the USI A-46 review are housed in one of the following structures: the AB, the EB, the RB, the TB, the warehouse, the control house, the intake structure, and the yard structure. All the major structures, with the exception of the warehouse, are founded on rock. The warehouse is supported on compacted structural j backfill at ground level. i f

The licensee used Method A.1 to evaluate the seismic adequacy of equipment located at I elevations less than 40-feet above the effective grade, and Method B.1 for equipment located at elevations greater than 40-feet above the effective grade. For Method B.1, either the newly-developed realistic median-centered IRS, or the original conservative, design IRS, were used to l J

5 define seismic demand. For capacity, the licenseeirsed the GIP-2 BS, when comparing it to the GRS, or the BS multiplied by 1.5, when comparing to the realistic median-centered, or conservative design IRS. In its January 17,1997, response (Reference 11) to the staff RAI question 10 (Reference 10), the licensee stated that, for components that are wall or platform-mounted, the floor response spectrum for the next highest elevation was typically used to define the demand. For one component, a motor control center, the licensee used GlP-2 Method B.2, in comparing the capacity, defined by a GERS, to the demand, defined by conservative design IRS.

In the staff RAI question 2 (Reference 10), the licensee was requested to clarify its statements regarding the seismic demand and capacity of safety valves located on top of the pressurizer in the containment internal structure.' in its response (Reference 11), the licensee stated that a a calculation was performed to qualitatively generate A-46 median-centered spectra for the containment structure and its internals. This was done by using the ratio of the realistic q

median-centered response obtained for the AB to estimate the response of the containment i internal structure at the elevation of interest. In response to a staff request during a teleconference held on November 10,1998, the licensee provind the necessary approximate calculation which indicates that if median-centered spectra were to be generated for these structures they would be enveloped by 1.5 times the BS (Reference 12). The staff reviewed the licensee's calculation and accepts its conclusion regarding the seismic demand and capacity of safety valves located on top of the pressurizer in the containment internal structure because the calculation demonstrates that the seismic capacity is greater than the seismic demand.

GIP-2 places limitations on the use of Method A.1. These limitations are that the SSE GRS can be used for comparison to the BS when:

e The equipment is mounted in the nuclear plant at an elevation below about 40-teet above the effective grade.

1 e The equipment, including its supports, has a fundamental natural frequency greater than about 8 Hz.

e The a',1plification factor between the GRS and the IRS is not more than about 1.5.

The licensae did not provide information in the seismic evaluation report (Reference 9) showing cociornience with the limitation that the amplification factor between the effective grade level GRS and the IRS not be more than about 1.5 in the use of the GIP-2 Method A.1 for evaluations of equipment located within about 40-feet above effective grade. The staff addressed this deficiency with RAI question 3 (Reference 10). In its response (Reference 11),

the licensee stated that "It is NNECO's understanding that the NRC staff and representatives of the Seismic Qualification Utility Group (SOUG) are jointly seeking resolution of this issue." ]

l However, subsequently, in response to the above teleconference on November 10,1998, the l licensee agreed to provide the necessary information to justify the use of Method A.1 for l evaluation of equipment within 40-feet above effective grade. This information was  ;

subsequently provided in Reference 12.

j For the purpose of determining the 40-feet above grade elevation, the effective grade for each building must be determined. At Millstone Unit 2, the effective grade for most structures, which are founded on rock, was taken at the base of these structures (typically, elevation -25.5 feet).

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6 The effective grade for the turbine building is 12.5 feet which is the bottom of the steel columns where they are anchored to spread footings bearing on concrete backfill. For the warehouse, and the storage tanks in the yard which are founded at plant grade, the effective grade is elevation 14.5 feet. ,

The locations where Method A.1 was used to compare seismic demand to seismic capacity are:

e AB elevations -45.5, -25.5, -5.5,14.5 feet e EB elevation -5.5 feet

• RB elevations -22.5, -3.5,0.014.5 feet

• TB elevations 1.5,14.5,36.5 feet e Warehouse 14.5,38.5 feet e intake structure elevation 14 feet e Yard structure 4.5,14.5 feet To evaluate the appropriateness of the use of Method A.1 at these locations the staff estimated the amplification factors between the GRS and the IRS. Since the original licensing basis IRS were generally developed for the operating basis earthquake for 0.5% and 1.0% of critical damping and GIP-2 criteria are based on SSE spectra developed using 5% of critical damping, if the licensee did not provide values for the 5% of critical damping SSE IRS, the staff performed calculations using the licensing basis IRS to estimate the conservative 5% of critical damping SSE IRS.

A conservatism in the original design of the Millstone Unit 2 structures founded on rock is the fact that the response spectrum of the time history which was used to generate the design IRS significantly exceeds the SSE GRS at frequencies above about 3 Hz. This is shown in Figure 5.8-8 of the Millstone Unit 2 updated final safety analysis report (UFSAR). Therefore, in evaluating the amplification factor between the GRS and the IRS for rock founded structures the staff used the higher amplitude GRS of the time history. For structures founded on compacted fill, the staff used the GRS in the Millstone Unit 2 UFSAR Figure 5.8-4 for evaluating the amplification factor.

As was previously stated, the licensee developed median-centered IRS for the AB. It compared the median-centered IRS to the conservative IRS for the elevation of 14.5 feet, which is 40-feet above the effective grade, and found a factor of conservatism of about 2.4 associated with the licensing basis IRS at about 8 Hz which is where the maximum in the spectra occurs. The auxiliary building is a reinforced concrete shear wall building. Based on the staff's engineering judgement, it is reasonable to expect that this conservatism is similar to that in the other Millstone Unit 2 buildings of this type of construction.

For the AB at elevation 14.5 feet, the staff calculated the amplification factor by dividing the median centered IRS by the appropriate GRS. The amplification factor for frequencies above 8 Hz is about 1.5 or less. The staff considers the amplification factor between the IRS and the GRS at this elevation and lower elevations in this structure appropriate to justify the use of Method A.1.

The TB is a steel frame structure. The steel columns are anchored to spread footings bearing on concrete backfill extending down to bedrock. The effective grade is at elevation 12.5 feet which is the bottom of the steel columns. The licensee used the GRS for compacted fill

7 founded structures for the design of this building. The highest elevation at which Method A.1 was used in this structure is 36.5 feet which is 24-feet above the effective grade. The IRS at this location have amplifications factors of about 1.5 for frequencies above 8 Hz. The staff considers the amplification factor between the IRS and the GRS at this elevation in this structure appropriate to justify the use of Method A.1.

For the warehouse at elevation 38.5 feet, the licensee states that the maximum acceleration of the 5% of critical damping conservative IRS is 1.82 g at about 10 Hz. At 10 Hz, the amplitude of the appropriate GRS is 0.38 g and the amplification factor for the conservative IRS is 4.79.

Using a factor of 2.4 to account for the conservative IRS to median centered IRS comparison, the amplification factor for the warehouse is about 2. The staff considers that there is enough conservatism in the way the median centered IRS were developed to accept this amplification factor. The staff considers the amplification factor between the IRS and the GRS at this elevation in this structure appropriate to justify the use of Method A.1.

The intake structure is a reinforced concrete shear wall structure which is founded on bedrock.

The top of the slab is at elevation -27 feet which is considered as the effective grade level elevation. The operating floor where the SSEL components are located is at elevation 14 feet, about 40-feet above the effective grade. The maximum acceleration in the 5% of critical damping design IRS at elevation 14 feet is about 5.7 g in the frequency range of 7 to 9 Hz. The amplification factor over the appropriate GRS in this frequency range is about 14. Using a factor of 2.4 to account for the conservative IRS to median-centered IRS comparison, the amplification factor for a median-centered IRS in this frequency range would be about 5.8. At higher frequencies the amplification factor is much lower. The staff, therefore, concludes that the amplification factor at 8 and 9 Hz is too high to allow the use of Method A.1. Therefore, the licensee should classify any SSEL component in the intake structure that has a fundamental natural frequency in the range of 8 to 9 Hz, for which Method A.1 was used, as an outlier.

These items should be dispositioned as part of the outlier resolution. For components in the intake structure with fundamental natural frequencies above 9 Hz the amplification factor between the IRS and the GRS at this elevation and lower in this structure is appropriate to justify the use of Method A.1.

The RB consists of a prestressed reinforced concrete cylinder and dome supported by a reinforced concrete foundation slab. The interior strgures are primarily chield walls, concrete floor slabs and structural steel. This structure is founded on bedrock at a depth of 38.5 feet which is elevation -24 feet, the effective grade of the structure. The equipment in the SSEL is mounted on the internal structure. The maximum of the 5% of critical damping conservative IRS at elevation 14.5 feet is about 2.2 g in the frequency range of 8 to 10 Hz. The amplification factor over the appropriate GRS in this frequency range is about 5.5. Using the factor of 2.4 for the conservative IRS to median-centered IRS comparison, the amplification factor in this frequency range for a median-centered IRS would be about 2.3. Considering that there is conservatism in the manner in which the median centered IRS were developed and the limited frequency range,8 to 10 Hz, of the higher amplification factor, the staff concludes that the use of Method A.1 is appropriate for this structure at elevations of 14.5 feet and less.

The EB IRS are the same as those of the AB. Therefore, the staff considers the amplification factor between the IRS and the GRS at elevation -5.5 feet in this structure appropriate to justify the use of Method A.1.

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8 I The effective grade of the yard structures is elevation 14.5 feet. All SSEL equipment on these structures are at or below grade. Therefore, the use of Method A.1 is acceptable for these structures. -

l A few equipment items have been found to have conservative design IRS exceeding 1.5 times BS. These include equipment items,225-MCC, B52,22E, and UBS, which were identified as )

i outliers. The updated version of Table 4.1 contained in the licensee's letter of October 9,1998 I (Reference 16), provides the description of the outliers' condition and their resolution. The licensee reevaluated and regenerated conservative IRS using the guidelines of NUREG-0800,

" Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants," I and they were shown to be enveloped by 1.5 times BS as documented in S&A Calculation No. l 97C2973-C-001, which is referenced in the above updated Table 4.1. In other cases, such as j B52 MCC, the equipment capacity curve was reevaluated based on original MCC shake table tests. The licensee found that the resulting test response spectrum curve enveloped the conservative IRS, as documented in Calculation 97-ENG-01806C2.

Except for SSEL components in the intake structure, with a fundamental natural frequency in the range of 8 to 9 Hz, the staff finds the comparison of the seismic capacity to the seismic demand consistent with GIP-2 and adequate for the resolution of USl A-46. Method A.1 for j SSEL equipment with fundamental natural frequencies of 8 to 9 Hz is not justified. The I licensee should consider components with this characteristic as outliers and they should be i dispositioned as part of the outlier resolution.

1 2.4.2 Assessment of Eauioment 03 efs l l

As a second screening guideline, ino licensee verified the seismic adequacy of an item of mechanical or electrical equipment by confirming that (1) the equipment characteristics are generally similar to the earthquake experience equipment class or the generic seismic testing equipment class, and (2) the equipment meets the intent of the specific caveats for the '

equipment class. This process is necessary only when the BS or the GERS is used to represent the seismic capacity of equipment, if equipment-specific seismic qualification data are used to verify the seismic adequacy of an item, then only the specific restrictions applicable to that equipment-specific qualification data need be applied.

The " caveats" are defined in GIP-2 as a set of inclusion and exclusion rules, which are established to represent specific characteristics and features particularly important for seismic adequacy of a particular class of equipment. Appendix B of GIP-2 contains a summary of the caveats for the earthquake experience equipment class and for the generic seismic testing equipment class.

Another aspect of verifying the seismic adequacy of equipment included within the scope of this procedure is explained by the " rule of the box." For the equipment included in either the earthquake experience equipment class or seismic testing equipment class, all of the components mounted on or inside this equipment are considered to be part of that equipment and do not have to be evaluated separately.

The licensee found only a few equipment items with characteristics outside the bound of the

, above defined caveats. The anchorage for the emergency diesel generator (EDG) day tank, T48ATT48B, uses Wej-It Nose Cone non-removable type of anchors as opposed to the GIP-2

9 requirement for cast-in-place anchors for tanks. Also, Tank T3 does not meet the GIP-2 screening criteria since it is a large vertical tank supported by legs. A detailed evaluation for Tank T3 (VECTRA Calculation No. MP2 ORT 3, Section 5.1, Rev. 0) indicated that the tank anchor bolts would fait due to insufficient tension capacity, the tank legs would fail in bending, and the concrete floor punching shear capacity would be exceeded. The licensee identified these equipment items as outliers in Table 4.1 of Reference 9 and in an updated Table 4.1 of Reference 16. In Reference 16, the licensee confirmed that the tanks, T48A/T48B, have been evaluated and found to be adequate in calculation 98-ENG-02653C2 The licensee also confirmed in Reference 16 that they had completed permanent modifications for tank T3 under PDCR 2-95-040 using Calculation No. 95-ENG-1198 M2.

When evaluating an item of equipment, the licensee often used engineering judgment to determine whether the specific seismic concern addressed by the caveat was met. The licensee evaluated each item of equipment to determine whether it meets the specific wording of the applicable caveats or their intent. If an item of equipment as judged to have met the intent, but not the specific wording of the caveats, that item would still be considered to have met the caveat.

At Millstone Unit 2, the licensee had a very few situations where the intent of GIP-2 caveats was used rather than the actual wording. The licensee provided those interpretations or measures taken to meet the intent of the caveat in Section 4.1.2 of the seismic evaluation report. The staff has reviewed the information provided in the table and found that the SRT's interpretations and measures meet the intent of GIP-2 and therefore, the caveats are acceptable.

2.4.3 Eauioment Anchoraaes Section 4.1 of the seismic evaluation report (Reference 9) provides a summary of equipment screening and anchorage verification. The licensee verified equipment anchorages during the walkdown of SSEL equipment and documented the results of the walkdown inspections in the screening evaluation walkdown sheets (SEWS), Attachment E to the seismic evaluation report.

The licensee further condensed and summarized the results of the screening and walkdowns on screening verification data sheets (SVDS), Attachment F to the seismic evaluation report.

The licensee states, in the seismic evaluation report, that plant equipment were found to have good original seismic design. Electrical cabinets were generally welded to embedded steel members or secured with expansion anchors for smaller wall mounted components.

Mechanical equipment was typically anchored with cast-in-place or J bolts.

The licensee evaluated the seismic adequacy of equipment anchorages in accordance with Section l1.4.4 of GlP-2, and obtained the nominal capacities and reduction factors for anchorage elements from Appendix C of GIP-2. The evaluations were performed by the SRT which conducted the walkdown of the SSEL equipment and documented the results on the SEWS. The SRT performed tightness checks for concrete expansion anchors in accordance with the GIP-2 criteria. Evaluations of Cast-in-place or J-bolt used the embedment values given in the construction drawings. The licensee used minimum embedment values from the GIP-2 for expansion anchor bolts, if the tightness check was acceptable. The licensee used reduction factors for " reduced inspections" in cases where the tightness checks could not be performed.

The licensee included seismic capacity versus demand comparisons, BS, GERS, anchorage and interaction caveats, anchorage evaluations, where applicable, and field notes in the SEWS.

10 For anchored components, the SVDS specifies the building and elevation where a component is anchored, the applicable capacity and demand spectra and the results of the capacity versus {

demand and anchorage checks. The licensee provided this information for all SSEL j components. As summarized on the SVDS, ten components did not meet the seismic capacity {

versus demand check while seven components did not satisfy the anchorage check (Reference i 9). However, the licensee has subsequently reported that all outliers regarding anchorage have been resolved, and that they will submit the completion report required per GIP-2 after completion and closure of the planned actions related to the outliers (Reference 16). l The licensee stated in its response (Reference 11) to staff RAI question 16 (Reference 10), that the issue of masonrv block walls in the battery rooms and warehouse areas were evaluated in the IPEEE review for Millstone Unit 2, and their seismic capacities were concluded to be adequate. The licensee further stated, in the teleconference on November 10,1998, that safety-related masonry block walls were previously evaluated under IE Bulletin 80-11. In addition, the licensee addressed the staff concern regarding the seismic ll over I interaction by performing additional analysis which was acceptable to the staff (Reference 12). j The staff finds the evaluation of equipment anchorages to be consistent with GIP-2 guidelines,-

and adequate for the resolution of USl A-46.

1 2.4.4 Seismic SoatialInteraction Evaluation 1 As a part of the screening provision for verifying the seismic adequacy of an item of mechanical or electrical equipment, the licensee addressed potential spatial interaction effects for the equipment in Section 4.1 of the seismic evaluation report. This serves to ensure that there is no adverse seismic spatial interaction between the equipment under consideration and nearby i equipment, systems, and structures which could cause the equipment to fail to perform its l intended safe shutdown function. The interactions of concern are (1) proximity effects, (2) structural failure and falling, and (3) flexibility of attached lines and cables. Appendix D of GIP 2 contains the guidelines for judging potential interaction effects, when verifying the seismic adequacy of equipment.

The licensee's equipment screening process included evaluation for potential seismic l interaction concerns following the requirements of GlP-2, Section l1.4.5 and Appendix D. The licensee identified those items that did not meet GIP-2 interaction requirements as outliers and included them in Attachment G of the seismic evaluation report (Reference 9), in the form of outlier seismic verification sheets (OSVS).

During the plant walkdowns at Millstone Unit 2, the SRT identified a few interaction concerns which were later resolved. For example, a number of cabinets were not bolted together in addition, a line of lockers 43 inches south of the C08 and C08R cabinets may result in seismic interaction with the cabinets. The licensee has resolved these outliers, as indicated in Tab;e 4.1 of the seismic evaluation report.

In RAI question 14 (Reference 10), the staff requested that the licensee indicate through analysis the effect of potential impact between the auxiliary and turbine buildings, on the buildings, as well as, on the equipment. The licensee responded (Reference 11) that the adequacy of structures is not a part of the A-46 review. Regarding equipment, however, the licensee had performed an analytical study in which they concluded that the building interaction

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t did not adversely affect the AB floor response spectra at elevation 54.5 feet and therefore there was no adverse effect on equipment (Reference 12). Therefore, the licensee concluded, based on its analytical study and the judgement of the senior seismic peer review members, that there is no adverse effect of potential impact between the auxiliary and turbine buildings, on the buildings, as well as, on the equipment.

.The staff finds that the spatial interaction evaluation performed by the licensee meets the GIP-2 requirements and is appropriate for the resolution of USl A-46.

2.5 Tanks and Heat Exchanaers The licensee listed and evaluated a total of nine tanks and fourteen heat exchangers as SSEL components in the A-46 program. The seismic evaluation report states that the evaluations

- were performed by the SRT using the general methodology and acceptance criteria described

, in Section 11.7 of GIP-2. The SRT reviewed any existing analyses and performed supplemental

^ evaluations consistent with GIP-2 and summarized the evaluation results on the SEWS.

In RAI question 11 (Reference 10), the staff requested the licensee to discuss the way the seismic adequacy of the largest vertical steel tank was evaluated, in its response (Reference 11), the licensee summarized the review effort for both the condensate storage tank (CST) and the refueling water storage tank (RWST). The licensee upgraded the CST for missile protection and there is now a 20-foot high concrete ring wall connected at the base and the top of the tank shell with18 chairs utilizing 11/4-diameter Maxi-bolts. The SRT reviewed the existing seismic calculations. Based on this review, and the walkdown inspection, the SRT judged the CST to be seismically adequate.

The licensee performed a similar review for the RWST. The results of that review indicated that the tank did not satisfy the GIP-2 criteria for anchor bolt edge distance, stiffener thickness and effective tank shell thickness. Because of these deficiencies, the licensee performed a detailed calculation to determine the seismic adequacy of the tank. Based on the results of the calculation, the SRT judged the RWST to meet the GIP-2 criteria.

The staff reviewed a sample SEWS for a tank. The form included a simple checklist for the four features, specified in Section ll.7.2 of GIP-2, to be evaluated for tanks, and a fifth check for ring type foundations of vertical tanks. The licensee did not provide other information regarding the parameters that enter into these checks or the equations used to assess compliance. In response to a concern that the level of detail provided in the summary report and the response to the staff RAI is insufficient, the licensee stated in a teleconference on November 10,1998, that the level of detail provided satisfied the GIP-2 requirements, and that additional documents are available for staff review, if needed. The licensee further stated that all tanks and heat exchangers were examined during the walkdown, and that any deviations or omissions of i

existing calculations were supplemented by evaluations performed as part of the A-46 project

- (Reference 12). The staff accepted these representations by the licensee.

The staff finds the evaluation of the tanks and heat exchangers meets the GIP-2 guidelines and is adequate for the resolution of USl A-46.

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2.6 Cable and Conduit Raceway Suocorts I The licensee performed the cable tray and raceway support reviews in accordance with the -

criteria given in Section 11.8 of GIP-2. As stated in the seismic evaluation report, the reviews j consisted of plant walkdowns performed on an area basis and docurnented in sixteen area '

summary sheets. In the walkdowns, the SRT confirmed as-built details and reviewed seismic performance concerns in accordance with the GIP 2 guidelines. The licensee originally reported the limited analytical review (LAR) results for four selected worst case supports in References 9 and 11, and found no outliers. Subsequently, however, the licensee revised its I

response to RAI question 12, and reported that its previous statements of "no outliers were l

identified from the raceway reviews" was no longer valid, in addition, they increased the i number of LARs in support of the raceway evaluations from four to sixteen. As the licensee l

indicated in the updated Table 4.1 (Reference 16), they identified outliers for cable tray  !

supports in the cable spreading room, where Wej-It wedge anchors at the ceiling have gaps up l

to 0.5" between the support posts and the stops at the floor such that, during a seismic event, i and in the direction of the gap, the anchor bolt capacity may be exceeded before the post  ;

comes in contact with the stop, in the updated Table 4.1, the licensee proposed to reduce the loads on the anchor bolts by installing shims to fill in the gaps and ensure that the posts are  ;

laterally restrained at all affected supports.

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In the teleconferences held on June 3,1999, the licensee confirmed to the staff that the required modification (MMOD M2-97535) was completed on November 23,1998.

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The licensee contends that the cable and conduit raceway structures at Millstone Unit 2 are  !

very robust. The results of its A-46 evaluation revealed that none of the systems were found to '

be deficient. The staff finds the evaluation of the cable and conduit raceway supports meets j the GIP-2 criteria and are appropriate for the resolution of USl A-46.

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2.7 Essential Relavs l A review of relays associated with safe shutdown equipment is required as part of the resolution of USl A-46 program. The purpose of the relay review is to determine if the plant's safe  !

shutdown systems could be adversely affected by relay malfunction in the event of an SSE.  ;

The licensee's relay evaluation report, Attachment 2 to Reference 9, indicated that the SRT '

relay review was conducted utilizing data obtained from the SSEL which contained a list of '

electrically operated USl A-46 components that require relay reviews. This list is called the safe I shutdown relay review SSEL and is a subset of the SSEL. The safe shutdown relay review SSEL includes equipment that must change position or start in order to perform a safe i shutdown function, as well as equipment whose inadvertent actuation due to contact chatter 1 may compromise a safe shutdown function or provide misleading indications in the control room. i The SRT performed the relay screening for the associated relays on the safe shutdown relay '

review SSEL, based on the following steps: (1) identify the associated relays for each I electrically operated component; (2) identify relays with contacts that are inherently rugged or  ;

which are solid state and are considered not vulnerable to contact chatter (such as the mechanically actuated limit and torque switches on motor-operated valves), and exclude them i from the relay review SSEL; (3) identify the normal and required states of the components for a i

13 safe shutdown; (4) further screen those relays whose contact chatter is acceptable, that is, relay chatter does not result in an unacceptable consequence or prevent the affected system from carrying cut its required function; and (5) determine if operator action is an acceptable way of screening out certain relays, and describe what operator action is needed. Relays which remain in the relay SSEL after the above screening evaluations are classified as " essential."

The SRT corr; pared the essential relays' manufacturer, type and model number with those identified in Appendix E of EPRI NP-7148-SL (Reference 17), to determine if there are any seismically sensitive relays. For the remainder of the essential relays, the SRT compared the capacity of the relays to their seismic demand, in accordance with the provision of GIP-2.

Of a total of 1682 contacts identified for Millstone Unit 2, the SRT identified 479 contacts as

, essential relays. Among them, six contacts were identified as seismically sensitive relays (" low ruggedness relays"), which are listed in Attachment D of the relay evaluation report. All essential relays with known make and model and available capacities based on GERS or other acceptable methods were evaluated.

The licensee provided a listing and description of outliers, totaling 101, as a result of the evaluation, in Attachment G of the relay evaluation report. These include the above stated seismically sensitive relays and relays with unknown makes and models or with unknown seismic capacities. Note that relays contained in cabinets with potential interaction concerns are not being tracked as outliers; cabinets / panels which house these relays are tracked as outliers in the seismic evaluation report.

In Attachment 1 to its October 9,1998, submittal (Reference 16), the licensee provided an updated version of the relay outliers table (updated Table 4.1) which was originally included in the above Attachment G. It describes the resolution for all the contacts / relays previously identified as outliers in the licensee's January 22,1996, submittal (Reference 9). The licensee has since determined numerous relays to be acceptable in their present configuration based on further review. As indicated in Reference 16, and in the licensee's May 21,1998, submittal (Reference 18), the licensee determined that nine relays require operator actions from the control room after an SSE. The licensee has added eight new entries, all associated with the 4.1 kV switchgear, to the table containing the outlier list. In addition, the licensee determined l that six relays previously identified as " low ruggedness relays" are not in that category. As the j licensee committed in its May 21,1998, letter (Reference 18), that these six relays will be relocated to a lower seismic demand location so as to meet the capacity levels identified .

through GIP-2. As indicated in the updated Table 4.1, the required modifications were still in I progress. The updated table also indicates five (5) essential relays for which the qualifications, I based on seismic shake table tests, were stillin progress. All other relays have been resolved by the licensee.

I In a teleconference held on June 3,1999, the licensee confirmed that they have completed I revision of procedure AOP 2562," Earthquake," for the purpose of highlighting the need for the operators to reset the above mentioned nine (9) relays. The licensee has committed to {

i complete the above qualification tests and hardware modifications by plant refueling outage 14, as stated in Attachment 2 to Reference 16.

The staff finds the licensee's relay evaluation and planned corrective actions described above to be consistent with GIP 2 guidelines and appropriate for the A-46 program.

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14 2.8 Human Factors Aspect GIP-2 describes the use of operator action as a means of accomplishing those activities required to achieve safe shutdown. Section 3.2.7, " Operator Action Permitted," states, in part, that timely operator action is perrnitted as a means of achieving and maintaining a safe shutdown condition provided procedures are available and the operators are trained in their use. Additionally, Section 3.2.6, " Single Equipmnt Failure," states that manual operator action of equipment which is normally power operated is permitted as a backup operation provided that sufficient manpower, time, and procedures are available. Section 3.2.8, " Procedures,"

states, in part, that procedures should be in place for operating the selected equipment for safe shutdown and operators should be trained in their use. It is not necessary to develop new procedures specifically for compliance with the USl A-46 program.

In Section 3.7 of GlP-2, SOUG also described three methods for accomplishing the operations department review of the SSEL against the plant operating procedures. Licensees were to decide which of the following methods, or combination thereof, were to be used for their plant-specific reviews.

1. A " desk-top" review of applicable normal and emergency operating procedures.

2. Use of a simulator to model the expected transient.

3. Performing a limited control room and localin-plant walk-down of actions required by plant procedures.

The staff reviewed the licensee a submittal (Reference 9) regarding the verification of seismic adequacy of mechanical and electrical equipment in operating reactors. The staff requested additional information regarding operator actions specified in the licensee's report in a letter dated February 24,1998, (Reference 19). By letter dated May 21,1998, (Reference 18), the licensee responded to the staff's RAl.

The staff's review focused on verifying that the licensee had used one or more of GIP-2 methods for conducting the operations department review of the SSEL, and had considered aspects of human performance in determining what operator actions could be used to achieve and maintain safe shutdown (e.g., resetting relays, manual operation of plant equipment).

The licensee provided inforrr.: 'on which outlined the use of the " desk-top" review method by the operations departrnent to verify that existing normal, abnormal and emergency operating procedures were adequate to mitigate the postulated transient and that operators could place and maintain the plant in a safe shutdown condition. The staff verified that the licensee has considered its operator training programs and verified that its training was sufficient to ensure that those actions specified in the procedures could be accomplished by the operating crews.

The licensee stated that the shutdown paths selected for USI A-46 are similar to those used to shut down the plant in the event of a fire. During development of the shutdown paths for this program, existing procedures were reviewed and found adequate to address the shutdown requirements of this program. The only additional operator actions identified from the " desk-top" review wore associated with resetting nine (9) relays associated with the 4.1 kV breakers due to chatter. The associated operator actions would be carried out from the control room and procedure AOP 2562," Earthquake," would be revised to highlight the need to reset the relays.

In addition, the licensee determined that for six (6) essential relays, GERS did not presently envelope the seismic demand for these relays. Therefore, a modification was in progress to

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15 move the relays to a location of lower seismic demand which is enveloped by the relay capacities. As previously stated in Section 2.7 of this evaluation, the procedure change and l operator familiarization have been completed prior to unit startup from the recent outage. The h required relay modification, however, will be completed before the end of refueling outage 14.

In addition, the staff requested verification that the licensee had adequately evaluated potential challenges to operators, such as lost or diminished lighting, harsh environmental conditions, I potential for damaged equipment interfering with the operators tasks, and the potential for j placing an operator in unfamiliar or inhospitable surroundings. The licensee provided information regarding their evaluations to substantiate that operator actions could be accomplished in a time frame required to mitigate the transient. Specifically, the licensee provided assurance that ample time existed for operators to take the required actions to safely j shut down the plant and based this analysis on the Appendix R evaluation previously ,

performed. The licensee verified that existing procedures, availability of lighting equipment, and operator training were adequate to ensure that the operators could perform the required actions credited in the submittal (Reference 9). The licensee stated that Appendix R lighting had been installed in areas of the plant where local operator actions were required. The licensee verified that all required actions were located in structures which had been seismically analyzed for the safe shutdown earthquake and as a result, no major in-plant barriers would be expected in the areas or in the routes to where local operator actions would be required. The licensee performed seismic interaction reviews which eliminated any concems with the plant components and structures located in the immediate vicinity of the components which had to be manipulated. Therefore, the potential for physical barriers resulting from equipment or structural earthquake damage which could inhibit operator ability to access plant equipment was considered, and eliminated as a potential barrier to successful operator performance.

The staff determined that the licensee has demonstrated conformance with the GIP-2 requirements and the human factors aspect is, therefore, acceptable.

2.9 Outlier Identification and Resolution I

An outlier is defined as an item of equipment which does not comply with the GIP-2 screening i guidelines. An outlier may be shown to be adequate for seismic loadings, by performing an ]

additional evaluation using attemate methods or seismic qualification techniques acceptable to '

the staff. Based on the screening criteria stated in Section 2.4. a number of equipment items were identified by the SRT as outliers during the walkdowns. Table 4.1 of the seismic l evaluation report A provides a detailed description of each equipment outlier. The licensee updated this information in Attachment 1 of the submittal of October 9,1998 (Reference 16),

where the outliers are grouped by equipment class and the type of identified concern.

In Reference 16, the licensee documented the resolution status for each of the 41 equipment <

outliers. The licensee stated that, with the exception of the cable tray supports in the cable spreading room, where shims were to be installed to fill the existing gaps to reduce the loads on the anchor bolts, all other electrical and mechanical equipment outliers have been resolved.  !

The licensee has since confirmed in a teleconference held on June 3,1999, that the cable tray l support outliers have been resolved. The licensee has stated that, of the 101 essential relay )

outliers identified in the relay outliers table (Reference 16),11 relays were still being resolved and this would involve relocation of relays and relay seismic shake table tests, and nine would require operator action through the revision of procedure AOP 2562. The licensee has stated 1

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16 in its letter of October 9,1998, (Reference 16) that the hardware modifications and seismic shake table tests identified in the updated Table 4.1 were either complete or on-going, and has committed to complete their resolution by the end of Refueling Outage 14. The licensee further confirmed in a teleconference held on June 3,1999,'that the above procedure change of AOP 2562 was completed prior to unit startup from the recent outage.

Attachment D to the seismic evaluation report is a copy of the peer review report. Attachment D states that a sample of SEWS was reviewed by the peer reviewers after their independent walkdowns and was generally found to be in good order. A vast majority of the findings by the peer reviewers had already been identified and documented by the SRT. The peer reviewers, therefore, judged the USl A-46 walkdown to have been generally conducted in a thorough and professional manner. During the peer review walkdowns, a number of independent observations were made by the peer reviewers to enhance operating conditions. In its January 17,1997, submittal (Reference 11) the licensee provided a list of action items and the results of their resolutions. The staff reviewed the information and found that all the action items have been satisfactorily resolved by the licensee.

In regard to the use of the seismic margin assessment (SMA) methodology, described in the EPRI report, NP 6041 (Reference 20), the staff indicated in its RAI of August 29,1996, (Reference 10) that the methodology may yield analytical results which are not as conservative as those which could be obtained by following GlP-2 guidelines. Because of the uncertainty of its conservatism, the methodology has not been endorsed by the staff for the analysis of safety-related systems and components, including the resolution of mechanical, electrical, and structural component outliers in the USl A-46 program. The licensee stated in its January 17, 1997, submittal (Reference 11) that SMA methodology was not used to screen out any equipment components, and it had not yet used it to resolve any A-46 outliers. The licensee should verify in its A-46 completion letter that this methodology has not been used for equipment outlier resolutions.

In its January 22,1996, (Reference 9) and January 17,1997, (Reference 11) submittals, the licensee indicated that of all the outliers identified, they found only two which did not comply with the plant design basis. These two outliers are associated with the RB component cooling water (RBCCW) surge tank (T3), where the original frequency calculation was in error, and with a low voltage switchgear (22F) which was missing plug welds. Both conditions were reported in accordance with plant procedures by using the adverse condition report (ACR) process. The licensee dispositioned the two components as being operable and determined that they do not present any increased risk to public health and safety. As the licensee stated in its January 17, 1997, submittal, the required rework and modifications for these two components have been completed. Therefore, with the dispositioning of the two outliers that did not comply with the licensing basis, and no other A-46 outliers that are deficiencies with respect to the plant's licensing or design basis, the licensee contends that the committed schedule for resolving the remaining unresolved outliers wiii not lead tu a potential safety impact on p! ant safety. This is acceptable to the staff.

3.0

SUMMARY

OF MAJOR STAFF FINDINGS Based on the information provided by the licensee, the staff found that the licensee's USl A-46 program has, in general, followed GIP-2 guidelines, and that no programmatic or significant deviations from the guidelines were made during the USl A-46 resolution process at Miliatone

17 Unit 2. As stated in Section 2.9, the licersee has adequately resolved all the identified outliers, l with the exception of those essential relays, for which either hardware modifications or seismic qualification tests will be completed by the end of refueling outage 14.

The use of Method A.1 for SSEL equipment with fundarnental natural frequencies in the range of 8 to 9 Hz, located in intake structure, is not justified. Therefore, any component located in the intake structure with these characteristics should be considered an outlier and resolved.

The licensee's completion letter of the USl A-46 implementation program should confirm that such equipment outliers (if there are any) have been resolved.

4.0 CONCLUSION

S In general, the licensee conducted the USl A-46 implementation in accordance with GIP-2. The licensee's A-46 Implementation program did not identify any instance where the operability of a q

particular system or component was called into question. The staff's review of the licensee's implementation program did not reveal any significant findings that would suggest inadequacy of the licensee's A-46 program in light of the GIP-2 guidelines. The staff concludes that the licensee's USl A-46 implementation program has, in general, met the purpose and intent of the criteria in GIP-2 and the staff's SSER No. 2 for the resolution of USl A-46. The staff has determined that the licensee's already completed actions will result in safety enhancements which, in certain aspects, are beyond the original licensing basis. As a result, the licensee's f

actions provide sufficient basis to close the USl A-46 review at the facility. The staff also concludes that the licensee's implementation program to resolve USl A-46 at the facility has adequately addressed the purpose of the 10 CFR 50.54(f) request. Licensee activities related i to the USl A-46 implementation may be subject to NRC inspection. '

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, Regarding future use of GIP-2 in licensing activities, the licensee may revise its licensing basis in accordance with the guidance in Section 1.2.3 of the staff's SSER No. 2 on SOUG/ GIP-2, and the staff's letter to SOUG's Chairman, Neil Smith, on June 19,1998, (Reference 21). It should be noted that the primary consideration in the staff's determination to permit the licensee to incorporate GIP-2 in the licensing bas;s is the licensee's completion of all the identified outliers, in accordance with the GIP-2 requirements. Where plants have specific commitments in the licensing basis with respect to seismic qualification, these commitments should be carefully considered. The overall cumulative effect of the incorporation of the GIP-2 methodology, considered as a whole, should be assessed in making a determination under 10 CFR 50.59.

An overall conclusion that no unresolved safety questions (USO) are involved is acceptable so long as any changes in specific commitments in the licensing basis have been thoroughly evaluated in reaching the overall conclusion, if the overall cumulative assessment leads a licensee to conclude a USO is involved, incorporation of the GlP-2 methodology into the licensing basis would require the licensee to seek an amendment pursuant to 10 CFR 50.90.

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5.0 REFERENCES

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1. Regulatory Guide 1.100," Seismic Qualification of Electric and Mechanical Equipment for Nuclear Power Plants," Revision 2,1987

2. IEEE Standard 344-1975,"lEEE Recommended Practices for Seismic Qualification of Class 1E Equipment for Nuclear Power Generating Stations," dated January 31,1975

3. NRC SRP (NUREG-0800), Section 3.10, " Seismic and Dynamic Qualification of Mechanical and Electrical Equipment," Revision 2, July 1981

4. NRC GL 87-02," Verification of Seismic Adequacy of Mechanical and Electrical Equipment in Operating Reactors, Unresolved Safety issue (USI) A-46," February 1987

5. " Supplemental Safety Evaluation Report No. 2 on Seismic Qualification Utility Group's Generic implementation Procedure, Revision 2, corrected February 14,1992"

6. " Generic implementation Procedure (GIP) for Seismic Verification of Nuclear Power Plant Equipment," Revision 2, corrected February 14,1992, Seismic Qualification Utility Group

7. Letter, J. F. Opeka (NNECO) to Document Control Desk (NRC), " Response to Supplement 1 to Generic Letter 87-02, SOUG Resolution of USI A-46," dated September 21,1992

8. Letter, G. Vissing (NRC) to J. F. Opeka (NNECO)," Evaluation of Millstone Unit 2120-Day Response to Supplement No.1 to Generic Letter 87-02," dated November 20,1992

9. Letter, E. A. DeBarba (NNECO) to Document Control Desk (NRC), " Millstone Nuclear Power Station, Unit No.2, USl A-46 Walkdown Summary Report and Proposed Expansion of Licensing Basis for Verification of Equipment Seismic Adequacy," dated January 22, 1996

10. Letter, D. G. Mcdonald (NRC) to T. C. Feigenbaum, dated August 29,1996

11. Letter, M. L. Bowling, Jr. (NNECO) to Document Control Desk (NRC), dated January 17, 1997

12. Letter, R. P. Necci (NNECO) to Document Control Desk (NRC), dated February 8,1999

13. Memorandum, B. W. Sheron to A. C. Thadani," Task Action Plan for Performing Plant-Specific Review of the implementation of the Resolution for Unresolved Safety issue (USI)

A-46," dated July 26,1994

14. Letter, J. F. Opeka (NNECO) to Document Control Desk (NRC), dated July 7,1994

15. Letter, G. Vissing (NRC) to J. F. Opeka (NNECO), " Generic Letter 87-02, Supplement No.1," dated March 22,1995

16. Letter, M. L. Bowling, Jr. (NNECO) to Document Control Desk (NRC), " Millstone Nuclear Power Station, Unit No. 2, Identif: cation of he Resolution for Unresolved USI A-46 Mechanical, Electrical and Structural Outliers," dated October 9,1998

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17. EPRI Report NP-7148-SL, " Procedure for Evaluating Nuclear Power Plant Relay Seismic Functionality," dated December 1990

- 18. Letter, M. L. Bowling, Jr. (NNECO) to Document Control Desk (NRC), dated May 21,1998

19. Letter, NRC to NNECO, dated February 24,1998

20. EPRI Report NP-6041-SL,"A Methodology for Assessment of Nuclear Power Plant Seismic Margin (Revision 1)," dated August 1991 21 Letter, B. W. Sheron (NRC) to Neil Smith (SQUG), dated June 19,1998 Principal Contributors: A. J. Lee, DE/EMEB R. Pichumani, DE/EMEB R. Rothman, DE/EMEB Date: ~ June 30, 1999 L

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