ML20212K978

Safety Evaluation Accepting USI A-46 Implementation Program

ML20212K978
Person / Time
Site:	Cooper
Issue date:	09/30/1999
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20212K971	List: ML20212K966 ML20212K978
References
REF-GTECI-A-46, REF-GTECI-SC, TASK-A-46, TASK-OR GL-87-02, NUDOCS 9910070120
Download: ML20212K978 (12)

Text

_

f e*  %,%

UNITED STATES j

j o e' NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555 0001 4, . . . . . ,o SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION FOR USl A-46 PROGRAM IMPLEMENTATION COOPER NUCLEAR STATION OPERATING LICENSE NO. DPR-46 DOCKET NO. 50-298

1.0 BACKGROUND

On February 19,1987, the NRC issued Generic Letc 3L) 87-02," Verification of Seismic Adequacy of Mechanical and Electrical Equipment ir, sperating Reactors, Unresolved Safety issue (USI) A-46." In the generic letter, the NRC staff described the process for resolving USI A-46, and encouraged the affected nuclear power plant licensees to participate in a generic program to resolve the seismic verification issues associated with USl A-46. As a result, the Seismic Qualification Utility Group (SOUG) developed the " Generic Implementation Procedure (GIP) for Seismic Verification of Nuclear Plant Equipment," Revision 2 (GlP-2, Ref.1).

On May 22,1992, the NRC issued Supplement 1 to GL 87-02, which transrnitted the staff's l Supplemental Safety Evaluation Report No. 2 (SSER-2, Ref. 2) on SOUG's GlP-2. Pursuant to the provisions of 10 CFR 50.54(f), Supplement 1 to GL 87-02 required that all addressees submit either (1) a commitment to use both the SOUG commitments and the implementation guidance described in GIP-2, as supplemented by SSER-2, or (2) an alternate method for responding to GL 87-02. The supplement also required that those addressees committing to implement GlPo submit an implementation schedule and detailed information on the procedures and criteria used to generate the in-structure response spectra (IRS) to be used for USI A-46.

By letter dated September 21,1992 (Ref. 3), Nebraska Public Power Districi (NPPD), the licensee, responded to Supplement 1 to GL C7-02 for the Cooper Nuclear Station (CN3). In that letter, NPPD committed to comply with the commitments made by SOUG in GIP-2, including the clarifications, interpretations, and exceptions reported in SSER-2. The staff indicated its acceptance of the licensee's response by letter dated November 25,1992 (Ref. 4).

By letter dated June 13,1996 (Ref. 5), NPPD submitted a summary report containing the results of the USI A-46 program implementation at CNS. By letter dated January 25,1999

! (Ref. 6), NPPD sent supplemental information and clarifications in response to the staff's request for additional infermation (RAl), dated October 7,1998 (Ref. 7). In the letter of January 25,1999, hPPD notified the NRC that it had completed the resolution of all the USl A-46 outliers for CNS. NPPD also indicated that each outlier was addressed through the plani cor.6ctive action program and was resolved through the utilization of CNS calculations, modification packages, or maintenance work request packages.

9910070120 990930 PDR ADOCK 05000299 P PDR m

r This report presents the staff's evaluation of the licensee's USl A-46 implementation program.

The evaluation is based on the staff's review of the summary report and of the supplemental information, clarification, and documentation submitted by the licensee in response to the staff's RAl.

2.0 DISCUSSION AND EVALUATION The summary reput (Ref. 5) discusses the results of the licensee's implementation of the USl A-46 program at CNS. The report provides a safe shutdown equipment list (SSEL) and documents the screening verification and walkdown of mechanical and electrical equipment and the relay evaluation. The report also (1) documents the evaluation of the seismic adequacy of tanks, heat exchangers, and cable and conduit racaways, (2) identifies outliers, and (3) proposes outliers' resolutions including projected schedules.

2.1 Seismic Demand Determination (Ground Spectra and in-structure Response Spectra)

The earthquake ground motion used for the CNS plant structural design is presented in page 4 of Attachment 2, "USl A-46 Seismic Evaluation Report , Volume I/V, May 1996" to Reference 5.

The input time history is the N69W component of the Taft accelerogram of the 1954 Kern County earthquake normalized to a peak ground acceleration of 0.20g for horizontal components of motion. Two thirds of the horimntal ground motion was used for the vertical component of ground motion. This is consistent with the information in the CNS Final Safety Analysis Report.

The in-Structure Response Spectra (IRS) were developed by using a mass-spring structural model and performing a time-history modal superposition to calculate floor time histories that were utilized to develop IRS. The IRS were peak broadened by 15% to account for uncertainties in the structural model. During the review of 120-day report (Ref. 3), the staff determined that the licensee's IRS are considered conservative design spectra, as defined in GIP-2. The licensee submitted a report on the deve!opment of median-centered IRS in Attachment 4 to Reference 5. The median-centered IRS were developed following the procedures of GIP-2.

The staff finds the licensee's approach for determining the seismic demand consistent with the provisions of GIP-2 and, therefore, acceptable for use in the USI A-46 program.

l 2.2 Seismic Evaluation Personnel '

The CNS seismic evaluation was conducted by the seismic review team (SRT) which consisted of two Seismic Capacity Engineers (SCE) and included at least one licensed professional i engineer. NPPD stated that plant craft personnel assisted the SCE with the Llant-speHfic information regarding safe-shutdown equipment, their locations, opening equipment for internal inspection and pedorming talts tightness checks. The resumes of the SCE are included in Appendix A to Attachment 2 of Reference 5. They have completed SOUG training in their areas of involvement.

The licensee also indicated that personnel in the CNS operations department reviewed the items on the SSEL to ensure they are compatible with the normal and emergency operating procedures used for CNS. The relays asscciated with items on the SSEL were evaluated by a i

3-lead relay / electrical engineer, whose resume is found in Appendix A to Ref arence 8.

Dr. John D. Stevenson of Stevenson & Associates served as the third-party reviewer for the CNS USl A-46 implementation program.

The staff finds that the qualifications of the licensee's seismic evaluation personnel meet the criteria of GlP-2 and the staff's SSER-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 a safe shutdown earthquake (SSE).

To meet this provision, in its submittal of June 13,1996, the licensee addressed the following plant safety functions: reactor reactivity control, pressure control, inventory control, and decay heat removal. Primary and alternate safe shutdown success paths with their support systems and instrumentation were identified for each of these safety functions to ensure that the plant is capable of being brought to, and meintained in a hot shutdown condition for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> following an SSE. Attachment D of Reference 8 contains the SSEL.

The reactor decay heat removal function is accomplished by relieving steam from the reactor via the automatic depressuritation system (ADS) safety / relief valves into the suppression pool.

The ADS will depressurize the reactor vessel so that the low pressure coolant injection mode of residual heat removal (RHR) can be initiated for reactor coolant inveniory control which takes suction from the suppression pool. The removal of decay heat is achieved by placing the RHR <

system in the suppression pool cooling (SPC) mode of operaticn. During the SPC mode of RHR, the RHR takes suction from and discharges to the suppression pool via the RHR heat exchanger. The service water system provides the capability to transfer the decay heat from the RHR system to the ultimate heat sink.

The plant operatior.s department reviewed the equipment listed in Attachment D of Reference 8 with respect to the plant operating procedures and operator training and they concluded that the plant operating procedures and operator training were adequate to establish and maintain the plant in a safe shutdown condition following an SSE.

The staff concludes that the approach to achieve and maintain a safe shutdown for 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> following a seismic event is acceptable for the USl A-46 implementation program because it meets the criteria of GIP-2.

2.4 Seismic Screenina Verification and Walkdown of Mechanical and Electrical Eauipment The seismic screening and walkdowr; meluded verification of 316 equipment items that are typical of those found in the SOUG experience database in the 20 classes of equipment covered in Arpendix B of GlP-2 (Ref.1). The tanks and heat exchangers are evaluated in Section 2.5 6. this safety evaluation.

2.4.1 Eauioment Seismic Capacity Compared to Seismic Demand GIP-2 provides five methods for mmparing equipment seismic capacity to the seismic demand.

To verify its seismic adequacy, tha SSEL equipment items' seismic capacity should exceed the Qmic demand using one of the five methods provided in GIP-2. Method A.1 mmpares the

• 4 5

. SOUG bounding spectrum (BS) to the SSE ground response spectrum (GRS). Method A.2 compares the generic equipment ruggedness spectrum (GERS) to 2.25 times the SSE GRS.

Method B.1 compares 1.5 times the BS (bounding spectra or reference spectra) to the conservative design IRS'or to the realistic median-centered SSE IRS. Method B.2 compares the GERS to conservative design SSE IRS. Meinod B.3 compares the GERS to 1.5 times the median center SSE 1RS. The licensee used three methods for comparing the seismic demand to the seismic capacity for the equipment in tho SSEL. These are Method A.1, Method B.1, and the design of the component to the realistic median-centered IRS. Although the third method is not e GIP-2 earthquake experience-based method, it is acceptable for use in resolution of USl A-46 since it compares the seismic design capacity to the seismic demand. The BS exceeds the SSE GRS. Therefore, for USl A-46 implementation, the seismic capacity versus seismic demand comparison is adequate provided the criteria and limitations for use of Method A.1 are met. These criteria and limitations are (1) the equipment should be mounted belcw about 40 feet above the effective plant grade, (2) the equipment's natural frequency should be greater than 8 Hz, and (3) the amplification factor between free-field GRS and the IRS will not be more than about 1.5. Method B may be used for equipment at any elevation and for equipment with any natural frequency.

The structures containing SSEL items are the reactor builuing (RB), the control building (CB),

the diesel generator building (DGB), and the intake stmeture. The effective grade elevation for all buildings is 903 feet. The staff compared the SSE GRS to the IRS for the elevations up to about 40 feet above grade where the licensee used Method A.1 for the seismic demand to seismic capacity comparison and found that the amplification factor is about 1.5 or less.

Therefore, the use of Method A.1 for the capacity to demand comparison is appropriate for these locations for equipment with a fundamental frequency greater than about 8 Hz.

In Reference 5, the licensee provided results of the seismic capacity to seismic demand comparisons. The CB IRS at elevations 873 feet and 903 feet are enveloped by 1.5 times the BS. Therefore, equipment at these elevations meet the GIP-2 seismic capacity versus seismic demand provisions irrespective of their fundamental frequency. The CB IRS at elevations 918 feet and 932 feet exceed 1.5 times the BS. These exceedances are at frequencies below about 8 Hz and the elevations are less than 40 feet above the effective grade elevation.  ;

Therefore, the equipment at these elevations meet the GIP-2 seismic capacity versus seismic demand provision provided their fundamental frequency is higher than about 8 Hz. The DGB t IRS are enveloped by 1.5 times the BS except for an exceedance of less than 2 percent at the maximum of the elevation 917 feet IRS. The staff considers this small exceedance insignificant i because of the conservatism in the plant's design-basis IRS and the licensee's discussion in I Reference 5. The licensee indicated that this small exceedance is an artifact of the broadening I and digitization process, as it became evident from the review of the original plot of the raw (nonbroadened) spectrum; the peak is almost exactly equal to 1.29, the peak of 1.5x BS.

Therefore, equipment at these elevations meet the GlP-2 seismic capacity versus seismic demand provisions irrespective of their fundamental frequency.

The RB IRS at elevations where there are SSEL items are enveloped by 1.5 times the BS at frequencies greater than about 3.5 Hz. Section 4.2 of GIP-2 states "The seismic capacity spectrum needs only to envelop the seismic demand spectrum for frequencies at and above the conservat'vely estimated lowest natural frequency of the item of equipment being evaluated."

Therefore, SSEL equipment at these elevations in the RB meet the GlP-2 seismic capacity versus seismic demand criteria provided their fundamental frequency is greater than 3.5 Hz.

The staff concludes that the seismic capacity to seismic demand comparisons used by the licensee for implementation of the USl A-46 program are adequate because they meet the GIP-2 criteria.

2.4.2 Acsessment of Eauioment " Caveats" The licensee indicated in Reference 5 that the SCEs verified that the caveats listed in Appendix B to GIP-2 for each equipment class were met for CNS. The caveats are the inclusion and exclusion rules, which specify characteristics and features particularly important for seismic adequacy of a specific class of equipment when the equipment seismic capacity is determined by the experience-based data. The phrase " meeting the intent of the caveats" applies to equipment that does not comply with the specific wording in certain caveats but is deemed seismically adequate based on the judgment of the SCE.

The licensee findings for equipment whose seismic adequacy was verified by meeting the caveats were documented in Column 11 of Appendix B to the summary report (Ref. 5). NPPD considered items of equipment that did not comply with the GlP-2 caveats as outliers and these

.were documented in Section 3.3 of the summary report. If the licensee judged an item of equipment to comply with the intent of the caveats, the item was considered to have met the caveat rule, in accordance with GIP-2. NPPD listed equipment items that met the intent rather than the specific wording of the caveats in Table 3.1 of Reference 5.  :

In its response dated January 25,1999 (Ref. 6), to the staff's RAI dated October 7,1998, the licenseo presented supplementalinformation for some equipment items to demonstrate how the intent, if not the wording, of certain caveats was met. For instance, the SCEs noted that j hydraulic control unit racks CRDACC-125 and CRD-ACC-128 deviate from the typical racks in I the experience data base, but the SRT judged that the structure and anchorage are at least as j strong as those racks included in the data base. The licensee later indicated in Reference 6 J that this statement was inappropriate in that the racks' anchorage was not evaluated based on judgment, but specially analyzed as part of the review and found to satisfy provisions of GIP-2.

For valves SW-AOV-857AV and 858AV, whose bodies are made of cast iron, the licensee demonstrated that the stress in the valve body is about 1700 psi which is less than 10 percent of the minimum tensile strength (about 20,000 psi) for cast iron and, therefore, satisfies the 20-percent requirement criterion in GIP-2. The licensee also indicated that if a component did not meet the wording of a caveat, and was not found to be an outlier, the assessment and justification for meeting the intent of a caveat were noted on the screening and evaluation work sheets. j l

In general, the staff finds that NPPD's determination of the seismic adequacy for equipment I identified in Section 3 of the CNS summary report conforms with GIP-2 guidance on the  ;

caveats and is acceptable in those instances in which the intent rather than the wording of the caveats was met.

2.4.3 Eauioment Anchorace l The licensee discussed equipment anchorage verification in Section 3.1.3 of the sumrnary l report (Ref. 5). To verify the adequacy of equipment anchorage, the licensee performed field inspections (walKdowns) and analytical calculations in accordance with GlP-2, Section 11.4.4 and Appendix C. NPPD performed bounding calculations to verify equipment anchorage l

l l

adequacy for the worst loading condition. Appendix G of the summary report (Ref. 5) contains the anchorage evaluation. The licensee identified those items that did not meet the GIP provisions as outliers. The resolutions of the outliers is discussed in Section 3.3, Table 3.2 of the summary report. .

The staff concludes that the licensee's evaluation equipment anchorage is acceptable for USl '

A-46 because it meets the GlP-2 provisions.

2.4.4 Seismic Soatial Interaction Evaluation l As part of the equipment screening evaluation, the licensee considered ;he potential for seismic i interaction between SSEL items and between SSEL and non-SSEL items following the provisions of GlP-2 (Section 11.4.5 and Appendix D). NPPD screened enclosures containing l

essential relays for interactions that might cause relay chatter, e.g., adjacent panels not bolted taether. The licensee identified those items that did not mcet GIP-2 interaction provisions as outliers. They discuss these outliers in Section 3.3 of the summary report (Ref. 5). The l

identified interaction concerns were associated with suspended lights in contact with relay cabinets, and unanchored tables and copiers located near SSEL components. NPPD resolved these outliers by modifications, maintenance actions, and the removal of unsecured items from the area containing the items on the SSEL. The licensee provided the evaluations and I resolutions of the outliers in Table 3.2 of the summary report.

The staff finds the spatial interaction evaluation consistent with GIP-2 and adequate for the resolution of USl A-46 for CNS.

l 2.5 - Tanks and Heat Exchanaers The licensee listed tank and heat exchanger reviews in Table 4.1 of the summary report. In Reference 6, the licensee stated that large horizontal tanks, such as the diesel generator fuel oil day tank were evaluated in accordance with the provisions of GIP-2, Section 7.4. The summary report also stated that no outliers resulted from the tank and heat exchanger reviews.

The staff finds the licensee's evaluation of the tanks and heat exchangers adequate for the resolution of USI A-46 because they meet the GIP-2 criterb.

2.6 Cable and Conduit Raceways The licensee stated that the raceway review was performed as specified in GIP 2, Section 8.

The review included walkdowns, limited analytical reviews of the 12 representative worst-case raceways as well as examination of seismic spacial interaction with adjacent equipment and structures. Tha enalysic was based on the as-built dimensions. The licensee identified several outliers. Ihe ncensee's evaluation of the outliers used the median-centered IRS which were developed following the GlP-2 procedures. In a request for additionalinformation, the licensee was asked to explain how out-c! Sane structural stability analyses were performed for the outlier cable trays. NPPD responded that out-of-plane analyses are not required by the GIP-2 procedures. The licensee stated that the outliers were resolved using the GIF-2 lateralload evaluation and the realistic median-centered IRS using the criteria of GlP-2, Section 8.4.8.

After review of the configuration of the outlier cable trays, the staff agrees with the licensee's position that longitudinal stability in the direction of cable run and vertical buckling of the support

@ embers can be prevented when the braces located every 20 feet along the cable trays are considered. This issue was discussed in Reference 6 (page 10).

The staff concludes that the licensee's evaluation of the cable and conduit raceways followed GIP-2 criteria and is acceptable for the resolution of USl A-46.

2.7 Essential Reisvs The licensee identified 254 essential relays, which ma'; each have been associated with one or more SSEL components. These are listed in Appendix H of Reference 8. The licensec indicated that the relay evaluation was performed in accordance with GIP-2 (Ref.1) and Electric Power Research Institute (EPRI) report NP-7148-SL (Ref. 9). The staff did not identify any significant deviations from the GlP-2 methodology.

The licensee stated that relay spot checks were performed by the SRTs during the equipment walkdown and during the separate relay evaluation walkdown. According to the GIP-2 procedure, the purpose of spot checks is to verify the relay mounting, orientation, model number, load path, possible interaction, and ceble slack. Accordiagly, essential relays were checked to confirm tnat they were mounted as recommended by ihe manufacturer and to identify any abnormal or atypical relay mounting configurations. Mounting bolts were visually inspected to ensure that the relays were well secured, and relay model, manufacturer, and equipment r urpners were checked against the designations listed on the electrical schematic

' drawinai The licensee indicated that no abnormal mountings or damaged relays were found and that the relay mountings are standard and adequate. The relay types were found to ta i consistent with identifications shown on electrical drawings.

l Appendix l of the USl A-46 relay evaluation report (Ref. 8) identifies 32 outtar essential telays, of which 16 relays encompassing approximately 5 different manufacture models were identified as outliers because their seismic capacity could not be established from existing EPRI GERS l (Ref.10). Of the remaining 16 outliers,2 were GE 12HFA151 A and GE 12CEH12B2A low ruggedness relays (as identified in Appendix E of Reference 9) and 14 were essential relays with a seismic demand that exceeds their capacity. Appendix 1 also includes outlier seismic verification sheets (OSVS) for resolution of relay outliers. On page 11 of Reference 6, the licensee stated that all outlier relays have been addressed and resolved. A summary table that addresses the individual relay outliers and their specific resolution is provided on pages 11 and 12 of Reference 6.

The staff finds that the licensee's seismic relay evaluation meets the GlP 2 criteria and is acceptable for the USI A-46 resolution.

2.8 Human Factors Aspect As part of the resolution to USl A-46, GlP-2 contains provisions for use by licensees to ensure that adequate procedures and training are in place for plant operators to mitigate the conscquences of an SSE.

t 8-GIP-2 describes the use of operator action as a rwans of accomplishing those activities required to achieve safe shutdown. Section 3.2.7, " Operator Action Permitted," states, in part, that timely operator action is permitted 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 Equipment 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.

Section 3.7, " Operations Department Review of SSEL," of GIP-2 describes three methods for accomplishing the operations department reviews of the SSEL with respect to the plant operating procedures. Licensees were to decide which method or combination of methods was to be used for their plant-specific reviews. These methods included:

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

2. Use of a simulator to model the expected transient, 1

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

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 information which outlined the use of the " desk-top" and simulator methods by the operations department 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 licensee determined that the systems and equipment selected for seismic review in the USI A-46 program are those for which normal, abnormal, and emergency operating procedures are available to bring the plant from a normal operating mode to a cold shutdown condition. The shutdown paths selected were reviewed by the CNS operations staff and they determined that the procedures would i provide adequate guidance to the operators in response to a seismic event. The licensee provided assurance that ample time existed for operators to take the required actions to safely shut down the plant. This was accomplished during validation of the pertinent plant operating procedures related to the licensee's validation of the SSEL shutdown paths as part of the USl A-46 program. NPPD selected the loss of offsite power transient with nearly simultaneous failure of all non-safety shutdown systems as the scenario of interest to exercise the USl A-46 shutdown paths. They also used two scenarios during the validation of the safe shutdown sequences. The first scenario involved loss of high pressure feed with emergency depressurization and subsequent level recoverv. The second scenario involved failure to scram with emergency depressuiization and subsequent level recovery during the validation of the safe shutdown sequences.

The staff verified that the licensee had considered its operator training programs and verified that the training was sufficient to ensure that those actions specified in the procedures could be accomplished by the operating crews. The operations department verified that all actions i

E 9

necessary to safely shut down the plant were included in existing normal, abnormal, and emergency operati.79 procedures. Additionally, they verified that control capability and status indications for all credited USI A-46 equipment as well as indication from credited process-monitoring instrumentation would be available to the operators from within the control room.

The licensee verified that no additional operator actions, beyond those associated with the safe shutdown paths, must be performed to bring the plant from a normal operating mode to a cold shutdown conditions.

The staff requested verification that the licensee had adequately evaluated potential cnallenges to operators, such as lost or diminished lighting, harsh environmental conditions, potential for damaged equipment interfering with the operators tasks, and the potential for placing an operator in unfamiliar or inhospitab'e surroundings. The licensee provided information to substantiate that potential challenges to the operator were explicitly reviewed during validation of the pertinent plant operating procedures related to the licensee's desktop and simulator evaluations and as part of the USl A-46 reviews. The review determined that no local operator actions were required for the safe shutdown of the plant. In addition, the licensee explicitly evaluated the potential for local failure of architectural features and the potential for adverse spacial interactions in the vicinity of safe shouown equipment, where local operator action may be required, as part of the GIP-2 process.

As a result of the review, the licensee identified a potential control room interaction source associated with non-restrMned equipment (e.g., an unsecured worl: table and copier) and with the control room light diffuser pansls. The licensee stated that these issues have been corrected and procedural controls have been implemented to control potential interaction sources. The licensee performed seismic intcraction reviews which eliminated any concerns with the plant components and structures located in the immediate vicinity of the components that had to be manipulated. Therefore, the potential for physical barriers resulting from equipment or structural earthquake damage that could inhibit operator ability to access plant equipment was considered and eliminated as a potential barrier to successful operator performance.

The licensee has provided the staff with sufficient information to demonstrate conformance with the NRC-approved review methodology outlined in the GIP-2 and is, therefore, acceptable for USl A-46 implementation at CNS.

2.9 Outlier Identification and Resolution The staff discussed the identification and resolution of essential relay outliers in detailin Section 2.7 of this safety evaluation. The licensee did not identify any outliers as a result of the tank and heat exchanger reWews. The staff discusses the significant outliers associated with anchorage and the cable tray and conduit raceway supports in Sections 2.4.3 and 2.6 of this safety evaluation.

NPPD identified items of equipment as outliers for three reasons: equipment class caveats, anchorage adequacy, and seismic interactions. In Table 3.2 in Section 3.3 of Reference 5, the licensee lists 30 items of equipment outliers identified during the USI A-46 implementation effort at CNS, of which 13 items ware associated with small (about 11b) light fixtures (EE-LTG-B1 through B11), and strainers (SW-STNR- A & B), that were identified as class 0 since they are not covered by the 20 SOUG equipment classes. Of the remaining 17 items,13 were due to

1 1

=

\

l l

anchorage defichnce,3 were due to interaction concerns, and 1 had a loose bolt. The licensee I also included descripSons of the associated defects or inadequacies and methods for reso'ving outliers in the documentation. Appendix E to Attachment 2 of Reference 5, contains the i corresponding OSVS.

Based on its review of the licensee's resolution of outliers, as discussed in Table 3.2 of the summary report, the staff noted that 16 outliers were considered to be resolved by corrective actions. The licensee indicated in Section 3.3 of the summary report that resolution of the remaining 14 outliers required further actions as recommended in Table 3.2. The resolution was scheduled to be completed by the end of Refueling Outage (RO) 18 which was scheduled to commence October 1998. By letter dated January 25,1999 (Ref. 6), the licensee notified the NRC that it has completed the resolution on all the USI A-46 outliers for CNS.

The staff concludes that the resolution of USl A-46 for CNS is acceptable because it meets the GlP-2 criteria.

3.0

SUMMARY

OF STAFF FINDINGS The staff's review of the licensee's USI A-46 implementation program, as discussed above, did not identify any significant or programmatic deviation from GIP-2 regarding the walkdown and the seismic adequacy evaluations at CNS.

4.0 CONCLUSION

The licensee established its USl A-46 program at CNS in response to Supplement 1 to GL 87-02 in response to a 10 CFR 50.54(f) letter. The licensee conducted the USl A-46 implementation in accordance with GIP-2. The licensee's submittal on the USI A-46 implementation indicated that the SSEL contained 316 equipment items that were assessed during the walkdown to verify their seismic adequacy. The licensee identified 30 equipment items as outliers. The licensee's limited analytical review of the cable tray and conduit raceway supports identified eight outliers. In its June 13,1996, submittal, the licensee stated that it planned to complete the resolution of the unresolved outliers by the end of RO 18 which was scheduled to commence October 1998. By letter dated January 25,1999 (Ref. 6), the licensee notified the NRC that it has completed the resolution on all the USl A-46 outliers for CNS. The licensee's implementation report did not identify any instance in which the operability of a particular system or component was questionable. As described in Section 3.0, the staff's review did not identify any areas where the licensee's program deviated from GIP-2 and the staff's SSER-2 on SOUG/ GIP-2 issued in 1992.

The staff concludes that the licensee's USI A-46 implementation program has, in general, met the purpose and intent of the criteria in GlP-2 and the staff's SSER-2 for the resolution of USI A-46. The staff has determined that the licensee's already completed actions will result in safety enhancements, in certain aspects, that are beyond the original licensing basis.

Accordingly, the licensee's actions provide sufficient basis to close the USI 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 to the USl A-46 implementation may be subject to NRC inspection.

^ -

i  ; .

Regarding future use of GIP-2 in licensed activities, the licensee may revise its licensing basis in accordance with the guidance in Section 1.2.3 of the staff's SSER-2 on SOUG/GlP-2 (Ref. 2) and the staff's letter to SOUG's Chairman, Mr. Neil Smith, on June 19,1998 (Ref.11). Where

, plants have made specific commitments in the licensing basis with respect to seismic qualification, those commitments should be carefully considered. The licensee should assess the overall cumulative effect of the incorporation of the GIP-2 methodology, considered as a whole, in making a determination under 10 CFR 50.59. An overall conclusion that no unreviewed safety question is involved is acceptable as 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 an unreviewed safety question is involved, incorporation of the GIP-2 methodology into the licensing basis would require the licensee to seek an amendment according to the provisions of 10 CFR 50.90.

Principal Contributors: C.Wu S. Kim K. Desal R. Rothman G. Galletti Date: September 30, 1999 I

)

i

)

l I

5.0 References

1. Seismic Qualification Uiility Group, " Generic Implementation Procedure (GlP) for Seismic Verification of Nuclear Power Plant Equipment," Revision 2, corrected February 14,1992 (Accession No. 9212140073).

2. U.S. NRC, " Supplemental Safety Evaluation Report No. 2 on Seismic Qualification Utility Group's Generic Implementation Procedure, Revision 2, correctea February 14,1992,"

transmitted by GL 87-02, Supplement 1, May 22,1992.

3. NPPD letter to U.S. NRC Document Control Desk, " Response to Supplement 1 to Generic Letter 87-02 Supplement No.1 on Seismic Qualification Utility Group (SOUG)

Resolution of USl A-46, Cooper Nuclear Station," September 21,1992.

4. U.S. NRC letter to NPPD, " Evaluation of Licensee's 120 Day Response to Generic Letter 87-02, Cooper Nuclear Station (TAC No. 69439)," November 25,1992.

5. NPPD letter to U.S. NRC Document Control Desk, " Submittal of the Unresolved Safety issue (USI) A-46 Summary Report, Cooper Nuclear Station, NRC Docket No. 50-298, License No. DPR-46," June 13,1996, and Attachment 2," Cooper Nuclear Station, USI A-46 Seismic Evaluation Report"- May 1996.

6. NPPD letter to U.S. NRC Document Control Desk," Response to Request for Additional Information Related to USI A-46 and Notification of Outlier Resolution,"

January 25,1999.

7. U.S. NRC letter to NPPD," Request for Additional Information Related to Unresolved Safety issue A-46,' Verification of Seismic Adequacy of Mechanical and Electrical Equipment in Operating Reactors,' Cooper Nuclear Station (TAC No. M69439),"

October 7,1998.

8. Engineering and Planning Management, Inc., "Nobraska Public Power District, Cooper Nuclear Station, USNRC USl A-46 Resolution SSEL and Relay Evaluation Report,"

April 1996 (Attachment 3 to the C'!O oummary report for USl A-46 resolution (Ref. 5)).

9. EPRI NP-7148-SL," Procedure for Evaluating Nuclear Power Plant Relay Seismic Functionality," December 1990. (Proprietary information. Not publicly available.)

10. EPRI NP-7147-SL," Seismic Ruggedness of Relays," August 1991. (Proprietary information. Not publicly available.)

11. Letter from Brian W. Sheron, NRC, to Neil Smith, SQUG, dated June 19,1998.

j