ML14058A022

TIA - Regarding the Licensing Basis for External Flooding (GDC-2) for the Oconee Nuclear Station Standby Shutdown Facility (Ssf)

ML14058A022
Person / Time
Site:	Oconee
Issue date:	02/28/2008
From:	Office of Nuclear Reactor Regulation
To:
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References
FOIA/PA-2012-0325
Download: ML14058A022 (43)

Text

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i December XX, 2006 TIA Regarding the licensing basis for external flooding (GDC-2) for the Oconee Nuclear Station Standby Shutdown Facility (SSF)

A. Summary Region II NRC inspectors identified an external flood concern at the Oconee Nuclear Site, in that, a failure of the upstream Jocassee Dam could result in significant flooding at the site. Prior to the issuance of the SER for the SSF, the licensee completed several Jocassee Dam failure flood studies, and a full scope PRA with internal and external events, but failed to inform the NRC of the potential of site flooding from this event.

The single train SSF is licensed to mitigate the consequences of an Appendix R fire, turbine building flood, station blackout and security events and although not credited in, the UFSAR, the SSF is relied on by the licensee as the last line of defense for numerous accident scenarios such as aux building flood, control room flooding, high-energy line breaks, tornados, and external flood. During these events, the SSF's safety function is two-fold: 1) the auxiliary service water pump must supply water to the affected units' steam generators; and 2) the reactor building makeup pumps must supply seal injectior, to the affected units reactor coolant pumps' seals.

As an indicator of its potential consequences of a Jocassee Dam failure on the Oconee

'Nuclear Station, 12 of the top 100 external CDF cutsets in the licensee PRA are the result of a Jocassee Dam failure. Per the licensee's December 21, 1995 IPEEE submittal, the random failure frequency of the Jocassee Dam is 1.3 E-05, while the seismic failure frequency is XXX. Assuming that the 5 foot high external flood wall protects the SSF and its equipment from 80% of the random Jocassee failures, the random Jocassee Dam, external flood CDF is XXX. Additionally, if the 5 foot flood wall is assumed to protect the SSF and it equipment from 60% of seismically induced Jocassee failures, the seismic Jocassee Dam, external flood CDF is XXXX (Can Walt check and add more about the risk aspects of the Jocassee Dam Failure?)

The licensee contends that flooding resulting from a Jocassee Dam failure is not a design basis event, and so they are not required to protect against it.

Relevant Correspondence and Details On October 9, 1976, the Oconee turbine building (Unit 1, 2 and 3) was partially flooded to a depth of approximately 24 inches. The event occurred while Unit 3 was in an RFO and Units 1 and 2 were at 100% RTP. The flooding was the result of a loss of the DID static inverter which supplied 125 VAC to the vital instrumentation, thereby resulting in a loss of power to the CCW vacuum priming system which controlled the four way solenoid valves that direct air pressure to the opening or closing side of the condenser isolation valves (pneumatic, piston operated). This resulted in the 6 condenser waterbox cCF3'8 I G3 44

isolation valves attempting to open and override their respective "locked/hold closed" jackscrews. The opening force applied to 3CCW-20, the discharge isolation valve for waterbox 3A1, was sufficient to bend the "locked/hold closed" jackscrew resulting in flooding via the open condenser manways.

On May 18, 1978, the NRC sent the licensee a RAI regarding the proposed SSF design.

Question 6 asked, "Some equipment appears to be below grade. Provide the design features needed to prevent flooding. Provide the maximum limiting flood elevation at the structure location."

On June 19, 1978, the licensee responded to question 6 of the May 18, 1978, RAI as follows:

"Normal groundwater infiltration of the Safe Shutdown Facilities Equipment Enclosure will be limited by standard waterproofing techniques. Flood studies documented in the Oconee FSAR, Section 2.4.3 show that Lake Keowee and Jocassee are designed with adequate margins to contain and control floods so as to pose no risk to the Oconee Station site. The Safe Shutdown Facility is within the site boundary, southwest of the Unit 2 Reactor Building, therefore, it is not subject to flooding from lake waters. The Safe Shutdown Facility will be waterproofed to an elevation slightly above yard grade to prevent inflow of yard surface waters."

A May 16,1980 licensee memo to file, subject: ONS Meeting to Discuss PRA, documented a May 15, 1980 meeting between Duke, NSAC and consultant representatives to outline the schedule and scope of the oconee PRA. "The major objectives will be to (1) develop a meaningful assessment of the risk associated with oconee, rather than supporting NRC's IREP; (2) provide a benchmark for PRA's incorporating the advances made since WASH-1400; and (3) improve nuclear utility capabilities in this area.

A February 2,1982, licensee study, found in OSC-631 (Standby Shutdown Facility),

using the National Weather Service DAMBRK program concludes that a Jocassee Dam failure would overtop the Keowee Dam bY, 4 feet for 2.4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />, resulting in 32.5 feet of flood water on site. However, the Keowee Dam, an earthen structure, was assumed to remain intact despite being significantly overtopped for such a long period of time.

A March 15, 1982, licensee memo to file regarding "OPRA - Jocassee Dam Failure" stated that, "Additional studies have recently been completed on the most reasonable failure of Jocassee Dam and its effect on Oconee Nuclear Station." This statement implies that other studies have been completed on this subject (not just the February 2, 1982 study mentioned above). Case 2 of the study concludes that the a failure of the Jocassee Dam withg-number of non-conservative assumptions and inputs could overtop the Keowee Dam by, 1.2 feet and flood the Oconee Nuclear Station.

An April 4,1982, licensee memo to file regarding "OPRA - Jocassee Dam Failure" stated that, "... the extreme cases ... are not detailed because they are not based on valid Official1 ,t i.u., qXh

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assumptions and would not provide a basis for interpretation of likely events." As such, the Keowee Dam is deemed to be capable of withstanding a Jocassee Dam failure without flooding the Oconee nuclear Station.

An April 26, 1982, licensee letter discussed the Duke/NSAC PRA Project and the Preliminary Results of the Core Melt Frequency Analysis. The letter stated that, "On February 26, 1982, the Oconee PRA project team presented the preliminary results of the Oconee 3 probabilistic risk assessment study at a Duke management briefing session." During the meeting Duke management requested that NSAC provide Duke with summary report of the core melt accident sequences. "Accordingly, NSAC has issued to us the enclosed report for our consideration."

Section 8 of the enclosed NSAC report documented the Core Melt Accident Sequences resulting from External Flooding, that is, both precipitation induced external flooding (Section 8.1) and flooding due to a failure of the Jocassee Dam (Section 8.2). Section 8.2 of the report stated that the conditional frequency of Oconee site flooding given a failure of the Jocassee Dam is quite complex, as is the conditional probability of core melt given site flooding. In the end, assuming a Jocassee Dam failure, a conditional probability of site flooding oý 0.5 was assigned, while the conditional probability of core melt given site flooding was assigned to be 1.0 A July 2, 1982, licensee memo to file documented the "Oconee PRA - Evaluation of Jocassee Dam Failure", and stated that, "The purpose of this memo is to summarize recent efforts in evaluating the likelihood that core melt could occur at Oconee as a result of Jocassee Dam failure, and to resolve the treatment of this issue relative to the Oconee PRA."

The memo discussed in detail, "The May 15, 1982 verison of Section 11.11.4 of the Oconee PRA draft report (penitent portion attached) provides a detailed summary of the derivation of the frequency of catastrophic failure of the dam. This evaluation goes to (and perhaps slightly beyond) the limits of the data and assumptions available for characterizing this failure rate, and the value oi 2.5E-5/yr represents p best estimate of this frequency."

r'he memo also concluded that the conditional probability of site flooding of 0.5 discussed in Section 8.2 of the NSAC Core Melt Frequency Analysis ( see April 26, 1982 item, above) was incorrect and should have been 1.0. This is due to:

- the short warning time available for an impending Jocassee Dam failure,

- no rapid, effective mitigating actions (i.e., lowering lake levels),

- initial lake levels have little overall impact, and

- the time to failure is relatively short.

rhe attached, draft Oconee PRA, dated May 15, 1982, discussed numerous points of interest including: Dam Failure, Frequency of Dam Failure, Dam Failure Data, Method of Estimating Dam Failure Frequency, Results and the Jocassee Dam Failure's impact on Core-Melt Frequency. Specifically, the Dam Failure portion of the draft PRA stated that, U . Informa io d~3~s 33 G3 Gf3 44 44

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• Alca Sa..u,.ty Rulaied linrurmajIu*l "Ifa sudden failure of Jocassee Dam were to occur, and a rapid enough release of the impounded water from Lake Jocassee into Lake Keowee resulted, the flood wave generated in lake Keowee would overtop Keowee Dam and the Oconee intake dike, flooding the plant."

On July 17, 1982, the NRC sent the licensee a RAI regarding the SSF. Question 8 of the RAI asked, "State the elevation of the grade level entrance to the SSF. If this elevation is below the maximum lake levels, provide a discussion of the means by which the equipment within the SSF is protected from the effects of flooding caused by an unisolable break of the non-seismic CCW system/piping located in the Turbine Building.

The discussion should also state the maximum expected water level within the site boundary should such an event occur."

(Comment) Following the TB flood of 1976, numerous communications between the licensee and the NRC occurred concerning possible flooding of the TB and the potential loss of safety-related equipment located in the TB basement. As such, the licensee had convinced the NRC reviewers that the only flooding of concern would be from a turbine building circulating water pipe failure. So during the licensing of the SSF (a facility which was supposed to mitigate. fte consequences of losing safety-related equipment located in the TB basement)., bhe reviewers never, directly inquired about flooding from a Jocassee Dam failure, nor did the licensee provide the information despite possessing it.

Question 19 of the RAI asked "Describe those features of the design that assure that single failures within SSF components or that design basis events do not result in consequential failures of the SSF that would lead to conditions which exceed that for which safety systems have been designed."

On September 20, 1982, the licensee responded to question 8 and 19 of the July 17, 1982, RAI, as follows:

Q8) "The elevation of the grade level entrance to the SSFys EL 797 + 0. This elevation is below Keowee full pond elevation of 800 as well as the maximum lake elevation of 808.kRef. Oconee FSAR, Section 2.4.3). In the event of flooding due to a break of the non-seismic CCW system/piping located in the Turbine Building, the maximum expected water level within the site boundary is EL 796.5. Since the maximum expected water level is below the elevation of the grade level entrance to the SSF, the structure will not be flooded by such an incident."

(Comment) Despite possessing information that a Jocassee Dam failure could inundate the Oconee Nuclear Station and flood the same safety-related equipment as a rupture of the non-seismically qualified CCW system piping located in the TB, the licensee failed to disclose this accident scenario and its details to the NRC.

Q19) "Interconnections to essential plant systems have been inherently minimized by the SSF design objective (alternate means to achieve hot Offci,:-' Onl -,.,.,, KedL "nom~~ cF44 M3 4

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~iIklaI Use Unly becurity Kelattni M~rmatinr' shutdown). The only ties to essential systems are the interconnection of the power and control "swap over" for selected valves and the piping tie to the Emergency Feedwater System and reactor coolant pump seals. SSF ties to the existing plant are such that no SSF failure will result in consequence more severe than those analyzed in the FSAR.".

A January 17, 1983, licensee memo to file documents that a Jocassee Dam failure would overtop the Keowee Darn jv 2.45 feet, resulting in 4.71 feet of water on site- The flood study was completed as part of the Oconee PRA study, NSAC-60. Thememo also states that, "Similar dam failure studies were done for the Oconee PRA study

[NSAC-60 study] as documented in the March 15, 1982 Memo to File and April 5, 1982 letter to K S Canady."

(Comment) This study was performed with the use of numerous non-conservative assumptions, as will be described in several 1993 and 1994 memos. Two of which are:

For all cases studied, Lake Jocassee and Lake Keowee were not assumed to be a full pond levels.

For all cases studied, the minimum Keowee Dam elevation used was 815 feet msl. However, in 1996 it was discovered that the intake dike elevation is actually 813.5 feet above msl.

On April 28, 1983, the NRC sent the SSF SER to the licensee, which contained the following:

Section 4.8 Flooding Review DPC has concluded that the most likely reason for flooding of the turbine buildinq would be from a condenser circulatinQ water pipe break resultinq from a seismic event. The licensee therefore decided that the SSF would be a seismic Category 1 structure [which implies it is designed to withstand the effects of tornadoes]. The missile & spectrum upon which their analysis is based, is in conformance with the guidelines of the SRP Section 3.5.1.4, Revision .1, for a tornado Zone 1 site. The grade level entrance elevation of the SSF it_797.0 feet above mean sea level (msl). This elevation is below Keowee full pona elevation of 800 ft. as well as the maximum lake elevation of 808 ft. ( However, in the event of flooding due to a break in the non-seismic condenser circulating water (CCW) system piping located in the turbine building, the maximum expected water level ci -aedn.- d......5iG3ae44

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within the site boundary' is 796.5 ft. Since the maximum expected water level below the elevation of the grade level entrance to the SSF, the structure will not be flooded by such an incident. In addition, the structure will be water proofed to prevent infiltration of normal ground water. Thus, the structure meets the requirements of GDC 2, and the guidelines of Regulatory Guide 1.102 with respect to protection against flooding.

Per OSC-631 (Standby Shutdown Facility) rev. 8, the initial design of the North and South, SSF exterior flood walls (NSM ON-2347) was completed on June 8, 1984 and checked on November 29, 1984. Per drawing O-320-Z-3 and O-0320-Z-5, NSM ON-2347 was implemented on June 26, 1986.

(Comment) The licensee considered the Jocassee flood threat significant enough to install flood barriers around the SSF, but not significant enough to inform the NRC prior to licensing of the SSF despite possessing all of the information over a year before the SSF's SER was issued.

A January 11, 1984 licensee letter contained an attached SSF Commitment index. The letter stated that, "Attached is a marked copy of the oconee SSF Commitment Index indicating additions for the Civil Environmental Divisions. If you have any questions concerning these additions, place call ....." Commitment # CAEA00058 stated that, "Provide the Maximum limiting flood elevation at the structure location and the design features needed to prevent flooding." The source document is given as the RCS RAI dated May 18,1978.

In June of 1984, NSAC-60, A Probabilistic Risk Assessment of Oconee Unit 3, was completed by Duke Power and the Nuclear Safety Analysis Center of Palo Alto, CA.

The study was a complete PRA with both internal and external events (including the Jocassee Dam failure and the resultant flooding of the Oconee Nuclear Station).

An August 14, 1985,. NRC letter to the licensee acknowledging the review of the Oconee PRA (with internal and external events). The cover letter stated that, "Particularly, we focused on the analysis of core damage sequences and dominant contributors, to core damage accidents to check whether the results, as published, provide any new insights of safety significance. Although the PRA includes both internal and external events analysis, our overview focused only on core damage accident sequence analysis."

The Dominant Sequences to Core Damage portion of the letter contained a section on an External Flooding Sequence, which stated that, 'The sequence involves large scale flooding of the entire Oconee site due to the failure of Jocassee Dam located about 12 miles upstream from the Oconee site. -. Although initial cold shutdown is achieved successfully, site flooding is expected to cause a loss of the ability to maintain long term decay heat removal. The sequence mean frequency is about 2.5 x10-5 per reactor year."

The Overview on Generic Safety Concerns portion of the letter stated that, "An initial reading of the PRA dominant sequences and systems failures contributing to the

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S n y -Security Relae n dominant sequences has highlighted the relative contribution to core damage from large scale external flooding. A seismically induced failure of the upstream Jocassee dam could cause a large scale flooding of components required for long term decay heat removal from the core. The dam is located 12 miles upstream of the Oconee site at a higher elevation than turbine-building safety equipment. Using very simple and approximate techniques to assess the impact of such dam failures at the Oconee site, the PRA has obtained an estimate of 2.5x1 0-5 per reactor year (10%) for the external flooding contribution of the core damage frequency. Although, the above estimate seems to, hav@ a very large uncertainty, the potential exists that of external flooding could be significant at other nuclear facilities depending on the plant construction, its elevation relative to upstream dams, and the seismicity at that site."

On October 9, 1987, IN 87-49, Deficiencies in Outside Containment Flooding Protection was issued.

This IN was "...provided to alert recipients to a potentially significant problem pertaining to the flooding of safety-related equipment as a result of the inadequate design, installation, and maintenance of features intended to protect against flooding."

The IN discusses "... the potential for the loss of safe shutdown capability as a consequence of potential flooding of safety-related equipment outside containment."

The IN goes on to state that, "Serious consequences may result if the design features of the plant are not adequate to direct the resulting flood water safely away from important equipment. Such design inadequacies may result from (1) the inadvertent use of non-conservative assumptiops in the flooding design analysis, (2) the failure to recognize all possible flooding flow paths, (3) the failure to install flood protection features that have been determined- to be necessary, or (4) the failure to properly maintain installed flood protection features."

A March 3, 1988, licensee letter concerning Fire, Flood and Pressure Boundaries drawings, stated, "As requested by your letter of February 11, 1988, please find attached a set of red-marked drawings showing the flood boundaries. The four identified boundaries are as follows: ... 2) Barriers around the standby shutdown facility doors. 3) The Sump Pump discharge piping in the SSF between the exterior wall and the check valve. 4) The SSF cable trench where it enters the SSF. In addition, at the suggestion of RC Bucy, please show the maximum water height in the Oconee yard due to a Jocassee Dam break as 4.71 feet."

An October 30, 1989, licensee letter to the NRC discussed GL 88-20 and it supplement.

Specifically that, "...in June 1984 Duke and EPRI completed a Level 3 PRA, with external events on Oconee Unit 3. This PRA (NSAC-60) has been reviewed by NRC and its contractors. Subsequently, in 1987 Duke began a program to update the NSAC-60 PRA to take into account a number of changes made to the plant since 1980, the original PRA baseline. For satisfying the IPE requirement, Duke intends to utilize the updated Oconee PRA, which is a level 3 PRA with analysis for external events."

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A March 20, 1990, internal licensee letter and a April 16, 1990, followup internal licensee letter document the Duke sites attempt to use IN 87-49 and design studies to identify flooding deficiencies. Oconee's design study is identified as ONDS-268, Identification of Outside containment Flood Protection Barriers.

• A June 21, 1990, internal licensee letter discusses the scope of Oconee's effort for ONDS-268, and that the results of the study will be used to create a DBD on flooding.

The letter specifically states that, "A review of all applicable design documents (drawings, specifications, calculations, etc.) will be made in order to compile a list of flooding protection features. A review of the applicable Station Probabilistic Risk Assessment (PRA) will be made to determine flood sources or flood events associated with each flood protection feature. Features identified will have their function described and their relation to flooding states." The letter goes on to state areas of responsibility and a schedule for completion of the study with a final due date of December 31, 1991.

On November 30, 1990, the licensee submitted a complete level 3 PRA to the NRC with a systematic treatment of internal and external events. The submittal discusses the failure of the Jocassee Dam and its expected impact on the various PRA sequences, which range in frequency from 1.6E-06 per year to 2.9E-05 per year The submittal also discusses actions which have been taken due to the NSAC-60 study.

In that, "...Duke recognized certain vulnerabilities to severe accidents which were identified by the dominant sequences. Therefore, Duke implemented plant modifications to improve Oconee's ability to respond to severe accident events. These modifications include hardware/configuration changes and procedural changes. While most of these changes were implemented to reduce the likelihood and effect of Turbine Building flooding sequences, the likelihood and effect of other sequences have also been reduced. The major modifications implemented to date are described below:

13. The maximum credible, water height in the Oconee yard following a Jocassee Dam break is 4.7 feet. To ensure SSF survivability following an external flood of this magnitude, 8 foot high hydostatic barrier walls have been installed around the grade level doors. Platforms and stairways enable entrance to and exit from the SSF."

A February 15, 1991, internal licensee letter documents the completion of identifying the flood events for ONDS-268 (Identification of Outside containment Flood Protection Barriers) and high risk areas derived from the Oconee PRA. With respect to the SSF, the letter states that, 'The SSF is equipped withL5 ft., flood barriers at its two entrances, and has otherwise been made impervious to site flooding. Therefore, the SSF ýivould be available to mitigate all external flooding sequences. Two sump pumps in the basement of the SSF building eliminate interior flooding of the SSF safety related equipment."

On December 18, 1991, the licensee responded to the NRC regarding supplement 4 of C'ffiu~.al Usz Only Seu.iarity R3~z~t~a iiiruiii.at;3r. d3'~s 88 G3

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0Wm4i*s9-U0*-O- .ecurit GL 88-20. The response stated that, "As described in our November 1, 1989 response to the IPE program, Duke has completed Level 3 PRAs with analyses of external events for all three of the Duke plants. The Oconee and McGuire IPE submittals have been completed with updated PRAs."

A December 20, 1991, internal licensee letter documents the discovery of an unsealed flood penetration surrounding the C02 piping entering SW comer of the SSF. The deficiency was discovered during the Oconee Design Study, ONDS-268, Identification of Outside containment Flood Protection Barriers. PIR (Problem Investigation Report) 4-092-0052 was generated for the deficiency, on March 30, 1992.

An attachment to the letter discusses "Features for Protection from External Floods" and states that, "The Oconee PRA identifies two potential events that could lead to external flooding of the Oconee site. The first is a general flooding of the rivers and reservoirs in the area due to a rainfall in excess of the Probable Maximum Precipitation (PMP). The FSAR addressees Oconee's location as on a ridge 100' above maximum known floods. Therefore, external flooding due to rainfall affecting rivers and reservoirs is not a problem. The second source of external flooding is a failure of the Jocassee Dam. Failure of the Jocassee Dam would result in a postulated wave height oll 4.71 feet in the yard at the Oconee site. The SSF provides Oconee's most secure method of safely shutting down the plants following an external flood due to a Jocassee Dam failure." With regards to the SSF, the attachment also discusses the 5 foot flood wall at the North and South entrances to the SSF, along with the SSF sump and its pumps and level control switches..

A December 10, 1992, Jocassee Dam Failure Inundation Study (FERC Project No.

2503) was completed and predicted that a Jocassee Dam failure could result in flood levels at the Keowee Dam (815 feet msl elevation) of:

1) 823.28 feet msl for a random/"sunny day" failure of Jocassee (overtopped by 8.28 feet)

2) 824.13 feet msl for a PMF induced failure of Jocassee (overtopped by 9.13 feet).

As such, the Keowee Dam is expected to fail; consequently, the study predicted flood levels at the tailrace (0.6 miles downstream from Keowee) to be:

1) 808.51 feet msl for a random/"sunny day" failure of Jocassee

2) 812.82 feet msl for a PMF induced failure of Jocassee.

The Oconee Nuclear Site yard grade elevation is 796 feet msl.

On December 31,1992, the licensee implemented a FSAR update which added the Jocassee Dam failure to SSF portion of the FSAR (applicable pages of December 31, 1992 have been provided as part of attachment 2 of this TIA).

The update stated, among other things, that, " The second source of external flooding is a rapid failure of the Jocassee Dam. Failure of the Jocassee Dam would result in a

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O~fiz~aI U~ Ordy Security t'~eIati~d Info~rnntki, postulated wave height of A.71 feet In the yard at the Oconee site. The SSF protect's Oconee's most secure method of safely shutting down the plant following an external flood due to a Jocassee Dam failure.

Protection from flood at the SSF is provided by live foot flood walls at the entrances to the SSF supplemented by a watertight door at the south end entrance of.the SSF."

Taken from the SSF Flood Design section of the FSAR (section 9.6.3.1).

"The SSF will not be affected by the following postulated flood events: .... 3. Jocassee Dam Failure. The structure meets the requirements of GDC 2 and the guidelines of Regulatory Guide 1.102 with respect to protection against flooding." Taken from the SSF Flooding Review section of the FSAR (section 9.6.4.7).

A December 14,1993, licensee memo to file documents the results of the Jocassee Dam Failure Inundation Study and discusses the differences in predicted flood levels between-the January 1983 flood study and the December 1992 flood study. The memo discusses the differences between the 1992 FERC and the 1983 PRA studyýl 2.5 to 16.8 feet of water on site, compared with 4.71 feet of water). The memo also states that the Oconee FSAR and PRA will be revised to reflect the potential loss of the SSF during a Jocassee Dam failure.

Some key differences discussed in the memo are as follows:

1) "For the PRA study, routing of flood wave was predicted by a step approach using an older verison of National Weather Service DAMBRK program."

2) "For the FERC study, a later version of the DAMBRK program was used for routing the flood wave, using a full dynamic routing that makes use of downstream information."

3) "The PRA study takes full credit for the Little River basin acting as a storage basin in the event of a Jocassee Dam failure. Flooding of the Oconee yard would result from overtopping of the Oconee intake dike from the Little River basin. Keowee Dam is also overtopped but assumed not to fail. The FERC EAP [Emer-gency Action Plan] study assumes the flood wave from the Jocassee dam failure will overtop and fail the Keowee Dam before a significant amount of the flood volume can be spread into the Little River basin. Water from both the Jocassee and Keowee reservoirs will flood the Keowee tailrace area and enter the oconee yard prior to dissipating downstream."

4) "The 4.71 feet fIood heights in the PRA study cannot be duplicated with the current models. 'The backup documentation and calculations for the work supporting the PRA study cannot be found to verify previous modeling, assumptions, and calculations, etc."

5) " Warning time to lower water levels in the reservoirs will not significantly affect flood height unless the time is in terms of days rather than hours."

6) "Depth of failure will not affect the flood height since most of the water is released above mid-height of the dam."

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7) "The FERC study predicts the Keowee Dam will fail as a result of the Jocassee dam failure while the original PRA study did not predict failure of the Keowee Dam. It should be noted that previous FERC studies also predicted a Keowee Dam failure."

8) "The FERC study considered consequences of flow restrictions downstream of Keowee Dam while the PRA study did not."

The memo concludes by stating that, "More exhaustive studies could be undertaken to address this problem but were deemed inappropriate from a cost/benefit perspective.

Therefore, the Oconee PRA and FSAR will be revised to reflect potential loss of SSF function resulting from a Jocassee Dam failure. PIP Number O-G93-0181 has been written to document this process."

Comment: December 1993 memo states that, "...previous FERC studies also predicted a Keowee Dam failure." The licensee has not provided any previous FERC studies for this event.

On December 14,1993, PIP O-G93-0181 was generated, which documented that, "The latest Jocassee Dam failure study indicates the maximum credible water height could be much higher than the 5-foot wall."

Proposed corrective action #1 states that, "The external flood portion of the oconee PRA will be revised to reflecd Dotential loss of SSF function,.:esulting from a Jocassee Dam failure. The actual conrective action was a "Re-anaiysis is scheduled by Dec. 1995."

On February 11, 1994, the NRC issued a Notice of Violation and Notice of Deviation (Report number 50-269,270,287 / 93-25). This report contained a discussion of the Jocassee Dam failure. The discussion centered around two points:, :) the inability of the SSF to mitigate the worst case Jocassee Dam failure per the recently completed FERC study and-the inaccurate IPE submittal, which stated that the SSF flood walls were 8 feet in height.

A March 14, 1994 licensee response letter to Service Water Inspection, report dated February 11, 1994. The response states that, "Duke's Fossil/Hydra Department conducted an inundation study of Duke dams in 1993, in response to the FERC Emergency Action Plan (EAP) requirement. This study utilize, the latest computer models for inundation evaluation, including a number of FERC required conservative assumptions. In this analysis, the Keowee Dam was also assumed to fail due to overtopping of Keowee from the Jocassee failure. The resulting Oconee yard level flood was estimated to be: 12 ft. This result is understandably different from the assessment made as part of the'P'RA-study. An attempt was made to reproduce the results of the PRA study using assumptions consistent with original Civil Engineering evaluation in support of the PRA. This was unsuccessful since the details of the analysis could not be located and the responsible engineer was no Ionger employed at Duke. Key differences in the methodology and assumptions used for the two studies are as follows:

Of I & only -S_" ,rit- R-ela:ted_ Info--." on _cf'31 I1 G3 44

• se Onl- ". a**i,* i atn For the PRA study, routing of flood wave was accomplished by a step approach using an older version of National Weather Service DAMBRK program. For the FERC study, a later version of the DAMBRK program was used for routing the flood wave, using a full dynamic routing that makes use of downstream information. The FERC study considered consequences of flow restrictions downstream of Keowee Dam while the PRA study did not.

The Keowee reservoir consists of the Keowee basin and the Little River basin that are connected by a man-made channel. Fifty-six percent of the storage volume for the Keowee reservoir is in the Little River basin. The man-made channel is located immediately upstream and west of the Keowee Dam. The PRA study takes full credit for the Little River basin acting as a storage basin in the event of a Jocassee Dam failure.

Flooding of the Oconee yard would result from overtopping of the Oconee intaki dike from the Little River basin. Keowee Dam is also overtopped but assumed not to fail.

The FERC EAP study assumes the flood wave from the Jocassee dam failure will overtop and fail the Keowee Dam before a significant amount of the flood volume can be spread into the Little River basin. Water from both the Jocassee and Keowee reservoirs will flood the Keowee tailrace area and enter the Oconee yard prior to dissipating downstream.

In summary, a recent analysis for the Jocassee Dam failure using FERC-required modeling and assumptions produced more severe flooding than the magnitude considered in the PRA analysis. The Oconee yard flood level estimated in the PF-A analysis cannot be reproduced as stated above. Nevertheless, it is believed thatltbe 5 ft. SSF flood wadl would provide some protection for best estimate types of dim failure modes. Considering that the estimated dam failure frequency is very small 11.58E-OA 5/yr.),j additional analytical effort to more precisely quantify the flood level is considered not ýiarranted."

A March 28, 1994 licensee letter discussed a commitment to the NRC "...to complete a reanalysis of a postulated Jocassee flood with the available information on flood frequency, SSF availability, and SSF serviceability, as part of the IPEEE effort."

On March 31, 1994, IN 94-27, Facility Operating Concerns Resulting From Local Area Flooding was issued. This IN was issued "... to alert addressees to emergency preparedness, equipment operability and radiological control problems that may result from local area flooding."

The IN discusses that, "This event demonstrates that flooding problems and degradation of equipment may be caused by water inleakage even though flood waters are not above grade elevations. Water leaking through underground walls may impinge on electrical equipment or may enter radiologically controlled areas and spread contamination to other areas. Underground cable and pipe tunnels may become flooded and serve as pathways for water to enter plant buildings. Management and plant personnel attention to these conditions is important to ensure that equipment is protected and unsafe facility conditions are not created."

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Comment: The licensee should've used this IN to ensure that the flood protection studies commissioned in response to IN 87-49, Deficiencies in Outside Containment Flooding Protection, were adequate. No evidence on this could be found. If the licensee verified the earlier flood protection studies, it is likely that the inadequate SSF sanitary system design (URI 2006002-02) would've be identified by the licensee and corrected some 13 years sooner.

On June 2, 1994, OSC-5781, USQ. Evaluation for Change in FSAR Concerning SSF and Jocassee Flood (see attachment #2), was approved. The calculation discusses the rationale behind using 50.59 to remove information in the SSF portion of the FSAR with regards to external flood protection of the site during a Jocassee Dam failure (using 1983 PRA study flood level of 4.71 feet on site). The calculation states that, "FSAR Section 9.6 was revised in the 1992 Update of the FSAR to address external flood protection of the yard as a result of the rapid failure of the Jocassee Dam. The information was determined to describe a PRA study and is not part of the design basis for Oconee. The FSAR statements are to be revised or removed to correct the information in the FSAR and reflect the existing licensing basis of Oconee."

On June 13, 1994, Flooding from External Sources Design Basis Document was issued by the licensee. Section 2 discusses GDC 2 and that SSCs important to safety shall not be effected by flooding and maximum precipitation. Section 3.2.6, Potential Dam Failure, states that, "Dam breaks have no bearing on the design basis flood."

A December 16. 1994 licensee memo to file regarding the "Seismic PRA Analysis -

Jocassee Dam Flooding Factors" states that, "The current Oconee seismic PRA analysis includes the failure of the Jocassee Darm.as a sequence leading to core-melt. Based upon a calculation .performed in Jan. 1983 for the PRA analysis, a maximum resulting yard level of 4.71 ft. was determined using 'best estimate' - type assumptions. As a plant safety enhancement, a 5ft. wall was erected at the SSF doorway to provide flood protection. The wall was deemed adequate to protect the SSF from the more likely flood scenarios but was not intended to bound all flood scenarios. Following completion of the SSF wall installation, credit for SSF operation followingqa Jocassee Dam failure was taken for random and seismic failures of Jocassee since the flood analysis was not performed using conservative assumptions." The memo also states that, "An attempt was made to reproduce the results of the PRA study using the assumptions made in that analysis. This was unsuccessful since the details of the analysis could not be located and the responsible engineer was no longer employed at Duke."

On February 2, 1995, the licensee generated PIP 0-95-0139, which discussed the fact that the requirements for mitigating a Jocassee Dam break are unknown.

The PIP stated that, "At the time of the writing of the MS DBD, requirements for mitigating the failure of Jocassee dam are being re-investigated. The upcoming SSF DBD will provide the details on the investigation."

0:11ic.Lýýý- ý' ýýn ýrm o aýio =Cf3,6 13 G3 44

On December 28, 1995, the licensee submitted the IPEEE Submittal Report to the NRC.

The submittal discusses the postulated Jocassee Dam failure and its impact on the site.

Section 5.2.1.2, External Flooding From Jocassee Dam Failures tates that, "The Jocassee Dam is an earth-rockfill structure approximately 400 feet high. The dam was completed in 1972 and the reservoir was filled by April 1974." The section goes on to state that, "Size, type of construction, realistic failure modes, period of construction, and age were the major consideration used to define a data base for use in estimating te failure frequency of the Jocassee Dam." After collecting data from various sQurces and excluding non applicable data, the random failure frequency is estimated to be 1.3x10'r "To the extent that this is ....representative of the Jocassee Dam, these results Can be interpreted as the predicted annual random failure frequency of the Jocassee Dam from causes other than earthquakes or overtopping.

The Oconee external flood core damage frequency is dominated by floods that exceed kthe 5 ft. SSF flood barriers, and thus render the SSF inoperable. The estimated external iflooding core damage frequency from this analysis is 7.OE-6/yr. The dominant cut set involves floods that exceed the 5 ft. SSF flood barriers, thus rendering the SSF

ýinoperable.

On February 13, 1996, the licensee generated PIP 0-96-0298, which documented the discovery of a low point in the dike which forms the Oconee intake.

The detailed problem description discusses that the top of the intake dike was found to be at 814 feet above msl instead of 815 feet msl. The description goes on to state that,"Flood routing Studies performed by Hydroelectric Engineering Group for Keowee only predict that the water can rise to elevation 809 at the Intake Dike under Maximum flood conditions which would result from a Probable Maximum Flood (PMF) of the Little River ARM of Lake Keowee. Elevation 814 still provides 5 ft of Freeboard which provides an adequate margin of safety. However the PRA analysis group uses an outdated analysis based on the failure of Jocassee Dam that calculates the overtopping of the Intake Dike at the 815 elevation with a resulting flow across the Plant Yard at a depth of 4.72 ft. The 814 elevation would result in a much deper flow at th0 SSF than the previously calculated 4.72 ft for the same flooding analysis."

The remarks section of the PIP states that, "The change in the Oconee Intake Dike crest elevation from el. 815' to el 814' will not have any significant impact on he PRA flood analysis pertaining to a Jocassee Dam failure."

The PIP was closed with no corrective actions taken.

UFSAR Section 2.4 states that the Keowee Dam and associated dikes were constructed to 815 ft. msl.

In December 1996, Revision 2 of the Oconee Station PRA Summary Report was issued.

The External Flood portion of the report (section 3.3.4) stated that, "The second source of external flooding is a possible random failure of the Jocassee Dam.

Random dam failures include all causes other than a rain-induced failure or an

~jjfj~,i~I U~e Only So'"riy R.I~1ted 'nform:ti~.~- cf3~E 14 14 G~3 G3 44 44

=cf3,s

• ~~-ecurit lelaea normin earthquake-induced failure." The report lays out the Top 100 CDF Cut Sets for External Initiators, with 12 of the top 100 being Jocassee Dam failure-related events.

Appendix B of the report, External Events Analysis, goes on to state that, "The seismic capacities of most plant structures and components were developed by Structural Mechanics Associates for the original PRA. That study (Ref. B-3) gives a detailed description of how the seismic capacities were derived. The seismic capacities of the Keowee and Jocassee Dams were developed by Dr. Daniel Veneziano of MIT, a consultant to Law Engineering Testing Company. The results of that study are reported in Reference B-4. References B.3 and B.4 were published in 1981 and included in NSAC 60, the original Oconee PRA. References B-5 and B-6 are later revisions to some of the original capacities based on additional data and a more in-depth evaluation."

Appendix Section B.4 discussed, at great lengths, the possible failure of the Jocassee Dam and its ramifications on the Oconee site.

Appendix B of the Summary Report also cited several flooding and dam failure-related references ranging in date from 1966 to 1995.

On December 18, 1997, the licensee submitted a Supplemental IPEEE Submittal Report to the NRC which discussed the results of the USI A-46 relay review as it affects the previously submitted seismic analysis as well as other enhancements to the seismic analysis. The report documents, in several locations, that a failure of the Jocassee Dam would result in significant site flooding with a large portion of the r'smically-induced core melt frequency being dominated by flood heights greater than the 5 foot SSF flood walls (i.e. 40%).

On January 5, 1999, the NRC sent the licensee a RAI on regarding the licensee's IPEEE submittals.

Question 3 stated, "Cut sets obtained from the updated seismic analysis are presented in Table 5-1 of the 1997 Supplemental Report. However, analysis result summaries which could provide insights on dominant contributors to the IPEEE are not provided in the report. Please provide summary information for the updated results similar to that provided in Table 3-6 of the 1995 IPEEE submittal for sequence CDF, and to that discussed in Section 3.1.5.4 of the 1995 IPEEE submittal for dominant contributors (e.g.,

the contribution of dam failure to total CDF). If the results have changed due to the response to Question 1 above, please provide these revised results as well."

While Part C, HIGH WINDS, FLOODING, AND OTHER EXTERNAL EVENTS, of the RAI stated, "As noted in NUREG-1407, Section 2.4, the latest probable maximum precipitation (PMP) criteria published by the National Weather Service calls for higher rainfall intensities over shorter time intervals and smaller areas than have previously been considered; this could result in higher site flooding levels and greater roof ponding levels. Please assess the effects of applying these new PMP criteria to Oconee.

Additional information is given in Generic Letter 89-22."

On March 31, 1999, the licensee responded to question 3 and part C of the January 5, OrIELIdI Us~ Only C~drit1 R~IaL~d Inforrn~L~n _cf3~E~

_cf_ý-s 15 15 G~3 a3 44 44

OffivM Use Only Ser~uri~y Pelatod Inform~ticui 1999 RAI as follows:

Q3) "The total annual seismicallv-induced core damage frequency, as reported in the 1997 submittal, i, 3.47E-05 / yr. '\ flooding event (resulting from the seismically-induced failure of the Jocassee Dam), wl-,ich exceeds the 5 ft. SSF flood barriers, makes up the dominant cut set. The greatest concentration of failures is shown to occur approximately between 0.6g ard 0.9g. Sequences involving a total loss of power coupled with the 3SSF response comprise approximately 70% of the core damage .

frequency. (Cut sets with Jocassee Dam failures resulting in flood levels less tharJ....5 ft._\

make up represent 4%, while cut sets with the failure of power system components roughly 66%.) . Sequences involving the SSF (both seismically-induced and independent failures) contribute approximately 72% to the seismic core damage frequency. Cut sets involving the Auxiliary Building and SSF surrogate events contribute 5% and 30%,

respectively. Recall also that several sensitivity studies were performed on the seismic results to determine the effects of various factors, components, and fragilities (see Table 5-2 of the 1997 submittal). These results, combined with the information above, provide several insights into the analysis. Even though no one failure truly dominates the results, clearly, sequences involving a total loss of power (station blackout events) as well as th6.SSF -nake up a majority of the seismic core damage frequency. A plot of the mean plant fragility is shown in Figure 2. This chart shows the cumulative probability of failure vs. ground acceleration level as well as the mean failure acceleration levels for the top two seismic cut sets. The above results have NOT changed due to the response to Question 1 above".

Part C) "An updated flood study for the Oconee site, which includes the Keowee dam and reservoir, was performed in 1995 [Ref' 151]. This study used the criteria contained in the hydrometerological reports listed in Generic Letter 89-22. The results of this study were comparable to the results of the previous study referenced in the Oconee IPEEE report. Both studies demonstrated that the Keowee reservoir could accommodate the reservoir flooding that could result from a PMP."

On October 4, 1999, the licensee submitted additional information concerning part C of the January 5, 1999 RAI. The response was silent with respect to potential failure of I the Keowee or Jocassee Dams and resultant site flooding.

On March 15, 2000, IPEEE was reviewed (no SER was issued by the NRC).

On September 3, 2002, the licensee generated PIP 0-02-4678, which documented a Level 2 assessment to improve the design basis of the plant.

The PIP's executive Summary states that, "The objective of the design basis focus area at Oconee is to identify improvements that will reduce plant risk, increase design margins, and reduce regulatory risk. The objective of this assessment was to perform a broad review of the design basis to determine if new areas, not currently in Oconee design basis or system health plans, require review. As is evident from the assessment, the scope of design work at Oconee since the Recovery Plan has been extensive. Most of the significant differences between Oconee and a Standard Review OffeiIal O~nly - eettrit'Related !rfo~f~.r 4taiaivc3'-,1- -d3,p, 16 m 4 44

Gffk.J U-O.4ý-Securit~y Rea Yed Inoma"i Plan (SRP) plant were evaluated through these initiatives. The assessment considered insights from a DC Cook design basis benchmarking trip and a review of nonconforming item (NCI) PIPs. In addition, an industry consultant (Mr. Don Prevatte) performed an independent review of the Oconee design basis. Recommended focus areas from Mr.

Prevatte's independent review are factored into this Level II assessment."

"No strengths, findings, or deviations were identified through the assessment. Although many areas of the design basis have been or are being addressed at Oconee, this assessment identified sixteen items that warrant additional review. These sixteen items are listed as areas for improvement (AFIs) in the assessment results section."

"It is believed that completion of the currently identified design work at Oconee, along with resolution of the sixteen AFIs from this assessment, will achieve the objectives of the Oconee design basis focus area."

"The Assessment purpose and scope state that, "Also, based on a recommendation from the Oconee Engineering Manager, an industry consultant performed an independent review of the Oconee design basis. The consultant selected for this review was Mr. Don Prevatte, president of Powerdyne Corporation. Mr. Prevatte is a registered professional engineer with more than 30 years of engineering and management experience in the nuclear industry. He has participated in 82 technical team assessments of a wide variety of designs and vintages of nuclear power facilities for the NRC, utility licensees, and the DOE over the last 15 years. Of these 82 assessments, 59 were as a contractor for NRC team inspections. Recommended focus areas from Mr. Prevatte's independent review are factored into this Level II assessment."

"The following Areas for Improvement were noted in the PIP (related to the issue at hand)."

"1) Seismic risk should be assessed. The SQUG project is significantly improving Oconee's shutdown capability by resolving many seismic outliers through modifications.

However, as with the tornado PRA model, it appears justified to focus on a detailed review of the seismic PRA model to determine if any further improvements to the risk calculations or plant are warranted. A SITA would be a good mechanism to evaluate seismic risk, including engineering design elements such as response spectra for the Turbine Building and Auxiliary Building, procedures for achieving shutdown, and the primary sequences that contribute to core damage. The Design Review Board has requested a SITA on seismic risk in 2003."

"2) The SSF is critical in terms of risk reduction."

"1kI External flooding is a very high risk event that hp! not been analyzed in detail.

The scenario of interest is the Jocassee dam failure. t is recommended that all facets of this event be revisited, including credible causes, flood levels and associated consequences, methods of analysis, preventative and mitigative measures, and updated risk analyses. It is recommended that the DBG develop a project plan to thoroughly review external flooding risk."

=da' 17 G3 44

offk;ica Uc Only ý-U~ecuty ReaedI.rmio The assessment conclusions section states that, "This assessment has performed a broad review of the Oconee design basis. As is evident from the assessment, the scope of design work at Oconee since the Recovery Plan has been extensive. Most significant differences between Oconee and an SRP plant were evaluated through these initiatives.

The assessment also considered insights from a DC Cook design basis benchmarking trip and a review of NCI PIPs."

"No strengths, findings, or deviations were identified through the assessment. Although many areas of the design basis have been or are being addressed at Oconee, the following areas for improvement are identified:

12. External flooding is a very high risk event that has not been analyzed in detail. The scenario of interest is the Jocassee dam failure. It is recommended that all facets of this event be revisited, including credible causes, flood levels and associated consequences, methods of analysis, preventative and mitigative measures, and updated risk analyses.

It is recommended that the DBG develop a project plan to thoroughly review external flooding risk."

"In summary, the objective of the design basis focus area at Oconee is to identify improvements that will reduce plant risk, increase design margins, and reduce regulatory risk. The objective of this assessment was to perform a broad review of the design basis to determine if new areas, not currently in Oconee design basis or system health plans, require review. It is believed that completion of the currently identified design work at Oconee, along with resolution of the sixteen AFIs from this assessment, will achieve the objectives of the Oconee design basis focus area."

Proposed Corrective Action #12:

'"External flooding is a very high risk event that has not been analyzed in detail. The scenario of interest is the Jocassee dam failure. It is recommended that all facets of this event be revisited, including credible causes, flood levels and associated consequences, methods of analysis, preventative and mitigative measures, and updated risk analyses.

Based on the 9/16/02 DRB meeting, a completion time of 12/31/03 is requested."

Actual Corrective Action #12:

Priority: 03c Actual CAC: E Status: Closed Due Date: 07/06/2006 "This issue is being addressed by PIP 04-863." [see below]

Originated By: GKM7309: MC ANINCH, GEORGE K Team: GKM7309 Group: DBG Date: 05/11/2006 On February 21, 2004, the licensee generated PIP 0-04-0863, which again documents the licensee's belief that a Jocassee Dam failure is a beyond design basis event.

The PIP goes on to state that, "...readily available engineering documentation does not Offioia,11Uac Only -.-- it" Riteu htnr.Ihrratf _cd3,s 18 Gr3 44

clearly capture the various potential failure modes of the dam, the resulting water release rates, the potential impacts to the surrounding geography and any necessary plant response to this beyond design basis event.

Engineering should review the existing analyses and documentation to determine what, if any, upgrades in analyses, procedures and other documentation should be made.

The PIP's only corrective action has been delayed 8 times "due to other higher priority work". The latest due date for this corrective action is April 25, 2007.

On July 20, 2004, the licensee generated PIP 0-04-4733, which documents a Level 2 Assessment from a Regulatory Brainstorming Workshop on April 22 and 23, 2004. The workshop was led by the former Reg Compliance Manager, and attended by the new Reg Compliance manager, the SSF system Engineer, 2 GO PRA experts, and the Oconee Design Basis Group Manager among others.

One item proposed by the. "SSF Team", considered by the attendees and documented in the PIP was item "E(4). Raise the SSF flood wall to handle the maximum Jocassee Flood. (ENG)

Benefit - SSF would be available to mitigate the "worst case" Jocassee dam failure. This would improve margin in PRA calculations.

Action - SAA Group should provide the maximum elevation of the Jocassee flood. This elevation should be used as an input to a design study that determines the options for providing SSF flood protection. Based on the results to this study, a modification should be installed to protect the SSF from the worst case Jocassee dam failure" The PIP contains no corrective actions related to this item.

On September 29, 2004, the licensee generated PIP 0-04-6365, which documents the discovery of the need for a calculation to validate the adequacy of the SSF sump during an SSF event concurrent with the loss of the SSF sump pumps (discovered by a Cornerstone Inspection Calculation Team review).

Proposed corrective action #8 states that,!"The flood wall surrounding the SSF provides protection from some but not all postulated J-"cassee Dam failures. SSF Risk Reduction Team recommendations to increase the height of the flood wall surrounding the SSF should be considered when the replacement sump pumps are chosen."

However, actual corrective action #8 states that,"Based on discussions with the Severe Accident Analysis Group, modifications toVlincrease the height of the flood wall around the SSF will not be pursued at this time. Therefore, the proposed replacement SSF Sump pump should be based on operating with flood levels up to the height of the existing flood wall surrounding the SSF.'

cd3l 19 G3 44

iaUse On urity Re-dlanformaition On August 3, 2005, the licensee generated PIP 0-05-4978, which documents, for the second time, that the SSF CO 2 access cover is breached.

The PIP's detailed problem description states that, "The SSF access port for CO 2 delivery is normally covered by a bolted on cover. During SSF Housekeeping tour it was noticed that the panel was swung away in order to route temporary power cables into the SSF. The access port if located about waist high which is below the top of the flood barriers. Engineering was consulted to determine if there is an operability issue with the access port open. There is no SSF Operability issue but Engineering stated that from a PRA standpoint, it is not good to have the access port open unnecessarily.

Maintenance is removing the cables and replacing the access panel today."

PIP Corrective action #2 states that, "Based on discussions with Lee Kanipe (Sever Accident Analysis Group), the bolted cover over the CO 2 supply pipe should be installed because it is part of the flood barrier that protects the SSF. While this flood barrier is not required for SSF operability, it is important to PRA (similar to flood gate at the South Entrance to the SSF). Therefore, a sign, that states the importance of the bolted cover over the CO 2 supply pipe, should be installed."

PIP corrective action #3 states that, "The SSF ASW DBD describes why the watertight door at the South entrance to the SSF is important. The CO 2 supply pipe flood barrier should be included in this discussion."

Proposed corrective action #4 states that, "Perform expert panel review of MR function 8094.3, Provide flood protection barrier (external flood) for SSF, to determine if bolted cover over CO 2 supply pipe in SSF Response Room is included. Also, review risk significance of flood barrier. Assign additional corrective actions as needed to revise MR function 8094.3."

Actual corrective action #4 states that, "In its meeting on 10/05/05, the Maintenance Rule expert panel determined that function 8094.3 should be changed to High Safety Significant (HSS). Also, the panel agreed that the bolted cover is included in this function. The SSC Function Scoping database was updated accordingly."

The Maintenance Rule functional failure portion of the PIP states that, "The problem identified in this PIP is related to Maintenance Rule Function 8094.3-Provide a flood protection barrier (external flooding event). When the flood barrier for the CO 2 supply pipe located inside the SSF Response Room is not installed, the SSF is vulnerable to external flood water that exceeds the height of the resulting opening. Since.the height of the opening that is present when the flood barrier (bolted cover that surrounds the CO 2 supply pipe in the SSF Response Room) is removed is below the height of the flood gate provided at the South entrance to the SSF, a functional failure of the SSF flood protection barrier would occur for flood levels that reach the height of the opening. The bottom of the opoling that is present when the C0 2 supply pipe flood barrier is removed is approximatelN. 43.5" (-800.625') jabove the floor in the SSF Response Room. The cial Us - rity Rel dIn rmatio _d3,s 20 G3 44

top of the flood gate installed at the South entrance to the SSF is 801.75' (Ref O-320Z-3)."

On October 5, 2005, the MR expert panel re-examined the safety significance of function 8904.3. V'Lee Kanipe proposed that the SSF flood barrier (function 8094.3) should be high safety significance based on the external flood frequency and the fact that the SSF is the only mitigating system for this event. 'Since the Civil representative was not available, this decision must-be reviewed 'oy him. Update: On 10/17/05, the Civil representative on the expert panel (Bob Hester) agreed that this function should be HSS

[high safety significance]."

On April 26, 2006, Oconee Integrated Inspection Report 2006002 was issued. The report contains two URIs related to the SSF and this initiating event- namely:

URI 05000269,270,287/2006002-01, Failure to Maintain Design Control of SSF Flood Protection Barrier URI 05000269,270,287/2006002-02, Failure to Promptly Identify an Inadequate SSF Building Sewer System Design On October 5, 2006, the licensee submitted a written response to a choice letter for a preliminary white finding in lieu of a regulatory conference (see IR 50-269,270,287/2006002 and 2006016). The violation concerns the failure to effectively control maintenance activities, and therefore assess and manage the risk, associated with removing the CO 2 access cover (a passive NRC committed flood protection barrier as indicated on Oconee drawing 0-310 K-22) in the south wall of the SSF to facilitate installation of temporary electrical power cables.

The background portion of the licensee's response letter discusses the SSF, its flood barriers and the January 1983 flood study. Specifically, the letter states that, "As stat-d in the UFSAR, as a PRA enhancement, the SSF is provided withla 5 foot external wall_,

which is equipped with a water tight door near the south entrance oT the SSF.

Additionally, the UFSAR states that maximum expected water level, caused by a break of the non-seismic Condenser Circulating water system piping, located in the turbine Building, will be below the elevation of the grade level of the entrance to the SSF."

"Flood walls were not part of the original SSF structure upon completion in the 1983 time frame. Flood walls were added to both the north and south entrances of the SSF in 1988 as a result of insights from an NSAC-60 relative to externally initiated flooding events."

Once again, per licensee calculation, OSC-631 (Standby Shutdown Facility) rev. 8, the Initial design of the North and South, SSF exterior flood walls (NSM.ON-2347) was completed on June 8, 1984 and checked on November 29, 1984. Per drawing O-320-Z-3 and O-0320-Z-5, NSM ON-2347 was implemented on June 26, 1986.

The letter goes on to state that, "In 1983, an internal Duke study was completed which calculated a flood height of 4.71 feet)above grade in the Oconee yard. This ffici 0 - curi ea Info "3~ 1 3 444

-d.,:n 21 G3

OficiU Us ýec ui Rel e d ln ý 3n evaluation is referred to as a "best estimate" calculation because it assumed many inputs to be at their nominal values. The use of this "best estimate" method of evaluation is in accordance with EPRI PSA Applications Guide, EPRI TR-1 05396, and the ASME Standard for PRA."

"In 1992, Duke's hydro department conducted an inundation study of Duke dams in response to the FERC Emergency Action Plan Requirement. This evaluation used many conservative, worst case assumptions. The results of this study showed that flood heights in the Oconee yard could reach a level as high as 12 feet above grade." The letter also states that, "The best estimate calculation performed in 1983 established a worst case flood height of 4.71 feet above grade."

(Comment) If the "best estimate" study used many inputs at their nominal values, flawed, non-conservative assumptions, outdated computer modeling techniques and can not be replicated, then that study can not accurately predict the worst case flood height (i.e.,

4.71 feet above grade).

Currently revision 23 of the SSF ASW System DBD, Section 2.1.2.2.2, External Flooding Due To Jocassee Dam Failure states the following verbatim:

The SAR documents for the SSF contain no specific requirements, commitments, or statements concerning the need for external flood protection features for the SSF.

(Reference 2.5.2.1.20) Therefore, there is currently no commitment for the SSF ASW System to provide flow to the SG's for decay heat removal if flooding from a Jocassee Dam failure disables the feedwater and the emergency feedwater systems.

Based on information from the Oconee Probabilistic Risk Assessments (PRA), a 5' external flood wall was added around the SSF entrances to reduce the consequences of a Jocassee Dam failure. (Reference 2.5.2.4.6) This 5' wall was not intended to bound all flood scenarios but was deemed adequate to protect the SSF from the more likely flood scenarios. A recently completed flood analysis indicates that a Jocassee Dam failure could result in an external flood height of at least 10'. (Reference 2.5.2.1.20) Since the SSF ASW System is located inside the SSF Building, the SSF ASW System is not protected from a Jocassee Dam failure which results in an external flood height > the 5' wall.

Oconee had several PRAs performed and submitted to the NRC which addressed the Jocassee Dam failure. The NRC's review of the first PRA (Reference 2.5.1.9.38) addressed the potential for core damage from a Jocassee Dam failure. No commitments concerning the construction of an SSF wall to reduce Oconee's vulnerability to a Jocassee Dam failure were mentioned.

A second PRA (Reference 2.5.1.9.59) was submitted to the NRC in response to Generic Letter 88-20. The Generic Letter requested each licensee submit Individual Plant Examinations (IPE) and the Generic Letter states that the licensee's examination was to Se -Seci

/Mooll44 ela*te foatio _=d3's 22 3 44

o ia - ly ecuri a for "

initially be for internal events only. The Oconee PRA that was submitted addressed both internal and external events. The NRC's review of this PRA addressed internal events only. In the NRC's response, the NRC stated that their review of external events would be reviewed separately, within the framework prescribed in Generic Letter 88-20, Supplement 4. (References 2.5.1.9.59 and 2.5.1.9.81) Generic Letter 88-20, Supplement 4 (Reference 2.5.1.9.94) addresses Individual Plant Examination of External Events (IPEEE).

The potential for th6-ýSF to withstand an external flood due to the Jocassee Dam failure was also addressed by the NRC in their notice of violatin'- and deviation for the Service Water Inspection. TbW NRC noted as a finding that thf -SF could not withstand the Jocassee Dam failure. Which they stated. was i-consisterii with the IPE submittal. Their conclusions were based on the SSF having ai..5' external wallj and Duke's recently completed flood analysis which resulted in flood heights of at least 10 feet- .*Vhe NRC indicated that their concerns were with the Oconee IPE submittal. (Reference 2.5 1.9.88) The Duke response to this finding (Reference 2.5.1.9.89) indicated that thet5' wall was not intended to bound all flood scenarios, but was deemed adequate to protect the O'SF from the more likely flood scenarios. (Reference 2.5.1.9.89)

A third PRA (Reference 2.5.1.9.98, IPEEE Submittal Report) was submitted to the NRC on December 21, 1995 as Oconee's response to Generic Letter 88-20, Supplement 4.

Per the IPEEE Submittal Report, there is a significant reduction in core damage frequency due to successful operatinn of the SSF for Jocassee Dam failures which result in flooding that does not exceed the 5' flood barrier which protects the SSF. A Jocassee Dam failure that results in flood leveis which exceed the top of the 5' SSF flood barrier is the dominant accident sequence (2.6 E-06) leading to core damage resulting from an external flooding event. The estimated core damage frequency due to all external flooding sequences is 7.OE-06/yr .The IPEEE submittal concludes that the Oconee plant risk due to external flooding does not pose a severe accident vulnerability since a 7.OE-06/yr core damage frequencylis of the same magnitude as other potential accidents

-'uch as seismic event, fires, tornadoes, and other events.

The estimated core melt frequency due to a seismically induced Jocassee Dam failure which results in flood levels that exceed the top of the 5' SSF flood barrier is of the same order of magnitude as core melt frequencies caused by external flooding. Therefore, a eismically induced Jocassee Dam failure does not pose a severe accident vulnerability.

n order to protect the SSF from flooding due to a Jocassee Dam failure which results in

'lood levels < the 5' SSF flood barrier, the following flood barriers are required:

I. The water tight flood door located at the South entrance to the SSF must be closed vith all seven dogs latched before flood water reaches the SSF.

?. The bolted cover that surrounds the C02 supply pipe located in the Southwest corner f the SSF Response Room must be installed. The bolted access panel that is located n the CO 2 supply pipe bolted cover must also be installed.

ici Us - ýurRelat In r tion _d3s 23 G3 44

Ifthe 5' flood barrier which protects the SSF becomes inoperable, the SSF is not considered to be inoperable. However, the 5' flood barrier should be repaired in a timely manner to ensure that assumptions made in the Oconee PRA analysis remain valid.

Could you please provide answers to the following questions in relation to the licensing basis for external flooding of the SSF?

Question 1. Should the licensee have provided any known information regarding the potential to flood the Oconee Nuclear Station from the failure of the Jocassee Dam prior to the issuance of the April 1983 SSF SER?

Question 2. If the licensee had submitted the information regarding the potential to flood the Oconee Nuclear Station from the failure of the Jocassee Dam, would the licensing basis have included a Jocassee dam break and the resulting Oconee Nuclear Station flooding?

Question 3. Does the failure to provide all flooding related information to the NRC prior to issuance of the SSF's SER constitute a violation of either 10 CFR 50.9, the Atomic Energy Act, or the Atomic Energy Act for failure to provide complete and accurate information?

Question 4. Should the failure of the Jocassee Dam and resulting flooding scenarios of the Oconee Nuclear Station, postulated in the licensee's IPE with external events or the licensee's IPEEE, constitute an "analysis requested by the Commission" which would require the updated information be included in the next update to the UFSAR?

Question 5. The failure of the Jocassee Dam and resulting flooding scenarios of the Oconee Nuclear Station were included in the attached 1992 update to the UFSAR. This update also discussed the of the 5 foot walls at the entrances to the SSF to preclude flooding of the SSF..._ Was it appropriate to use the 50.59 process to remove the Jocassee Dam failure flood from the UFSAR in 1994?

Question 6. Currently, the Oconee Nuclear Site is unable to defend against a Jocassee Dam failure which results in flood waters of greater than 5 feet on site. Such an event would result in meltdown of all three Oconee units due to the loss of all safety-related equipment in the Turbine Building, Auxiliary Building, and SSF.

The licensee has asserted that the currently installed SSF flood barriers are not required to maintain SSF operability, as they were only installed as a PRA enhancement. Should a backfit analysis be performed for the Jocassee Dam failure?

\Q Mal 'sý OnI ý- r e

ýeedlnf ýrmatiý _c3k-s 24 G3 44

Qffiý" se O - c~urity Rý dIn mabf Attachment #1, Section 9.6 of Oconee FSAR prior to 1992 update 4 icia Iy - ýcu ri elI d I nfmma t =d3-s 25 Gr3 44

ni curt 46d Informa "on

-TSA?I U l doe 5tn f EnTie, t'O raviaiW this inlbrMati dn4 The`-annual TSA~R uptt o 1 will bý4 iatisIbuted::In ope 0

-4ýiký '~dtb nh chag3 ~~ Iicti~n evr,

" ~ ~iJ~

f~~~xno age Jaat ttl- uar~isoix,.

se1 '+/-na46 ciieonaoi thps next~ ýaubtmj I deL Ma-.

1%anks for your NhJP.' Call. me at 34-19 if yoU 'hav~q ank qestl'ns.

0#. £,.'iarriet 0 44

--ý ýUs~eýQni olýSecu Rela rmati I I

~'Z.

P~ot~tion 4~'C-R~t5 ~a~nt n Enqirt4 :on d. -~d~

a~~q g~jt Att~tt t Dcuvan neA riter dh

ýeOniy-, ýRdla d in ýai ýn

.........  ! l eE~FK~T1O~~F~N NER.IrtZ RA1iCUAIQ I

STATIWN ADN if4j.4T PM~M8~Ijgge~ .ttt1Qfl ut VMn~S t an, -3I CACULATtor NIJmvpI vs 78..

TOTAt,S41#M"m Tý, MCAEr

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t__Tbr__tr-___________i__

r_____TP4__T___DATE IRYCNEbiVE DO6VMUMEFNTCONTR OL ST___________

I R~ H-~ A H;;IMbTV LUST.'llýý, U.1' Avm a b A~DD $ftVMCU rEI.U1OP Im3f XFAZL AID I 1m k 1 Au, Dom.r~~

- - P - - - - - F -

.4

.Attachment,#2, 10 CER 50.59 Evaluation to remove Jocassee Dam Failure language from the SSF portion pWýO, IsO IaUlthlof it tý detarm1neif 1, ~d 3F) ý............................,.....................

A~terzinegw thinr~ecPoý te eeCr .

qg~tscrrin of choanc 12*1r3 P-r-ing

ýittgmaitz ar to ba revised or x"' ved tn c-oiract the infoxmatic n~ in the FSARý and 1~niq- Set~h Ipbi tb$i ct buxon a, A mark up olf th1e p~r4c4ý.st Si h~~ si~31e in,.7,s any a;jo

ýA he'SS TII CA'efeXty Ivl~to Rpot~

~i~fiooding x tcL-A'41 &I tubn vkxIdinof~ig~

T~ference i dtmt Far1i2 ityhflo dtnI-t~d~eS'ws iaaond id ino~ainfriEu tth-ezoondo-cl '- tubu;.I~ie jpiiskn Alossirig. TheA C~onee hdevmral. PRA5 erort4 sbýitadt the; UkC ~ix" FLoOD. I(ws

i

... ur/iat d&~fid Datew~n ..

~at~ed~os~ooJ~

te fflur. * ~ NR'c revi-evwsfth The. :Pcbtential for ccor 4-anage I rm+/--thie f ~re- di the jobweo 4?m as addt rsftiaut e the VRCld,0 ,vptrespba any SSF waiiql as

~ cntiPRA ia uettt the ..NRC in-!reapoIM%00eto. ýer Generio t OTte 14; qkr tat e~bu Wed' 6ioenea uutI4'iu1 l al~nd'nex (IPT "This r.4Dzij andtf7 netr~ai~t~

II and, 9), Cenatiic Lette 88-20,~ ZSup?1mez 4

-The.pctanti~a I Z~ theý ýPF to 3witiltand: a.T3, external. f loca due tri the zlccawiee D~am faillure wa-,a 6 zifrsssedee'y t~b~e .#C in. thiiir nr~liwe o.f Iitl 66o a"di devvitiý,n -t the Ser.vico a:*itO+/-

withct'an ýEi5h J cateý;a Dta7i fallurceý, wohit tbay. stated was 66hznistc, t vith ltheý T~, sub i tt a I. a.eiwocniosere bae nthe 3SF hawtingý a 5 f oot. extonal floc wai 41 n& uý x

of atit leatt 10 f . i-J 'Tb4 WIX:Laindiat .ad tha.t th4Eix;cn .ooiern~ .s r V i th zthp. 06oi ee 4PS sxbmitittal- m~ereli. '12).. DThue re!;Pioxidedý =40 014~. iiýhdlhg ir. ref Lrew~e' l~~i T1i:'heDi~ct--ro5sfra fiio31at. ;that tihe lr IDo wall,'Twas 1not. intandea. to bo"ntid al 1.100d encrioz.,

but Q-S ~ie~~qa~ op'iet h SoF fran the 'it cI floo acnaros eanzL  ;ýoxp'0 rsponse f,,= "the NR nr te Duke' a 'zesporiae 6,ufmiftal hAS bea grneceivpd. Aqoý n tat, In,~

-sukait al. fro'iii ukse ýnna ~.t ne Ma iVs 6r -he 1E.

A revieow -of other Satety Ana lysis Report:~S~jdcmet rslo ta' r"4 uiett,;

.1.n

-o -ef~ ~Ion i-e, o. 'sae0e

~ri~ the. ned r etmmnal f ladd- Protet~i&_~ Xetrc a;Puina t0 'SSF.' ThW :'t16t Vitwmev ýCp itments ,ah j~eht~jicaij-pe il a tiors W.re Irevie6Wed z's~~I,repl +/- qAR rale n ý

~rt~o for the' 8q' TRferenýe9 '2 ~~d3 tfie T6cass~ee dairn isee~4 n the FSAI I 'frenct 1.)_ Effect&

oqf.'an uipgtrea~m darn Thilure pro add 'sse +a cnaigthe efltect Of ihb~ failu're 6n. o .Tlhis: ifrmpatin was in re~tpcrna to,

ane'rdc Letter ag'-- ca- _Jih4o,,a dtite~ abovews~iy e~~e

-ythe K for ript alna evtt (-di ) awSM TAr~t 'eaing. talle SBY .qdiingth mft~ is Mai th6 TAS~AR ante 2 ") reane. the'P ýalb t2i3y6f a6_oiet e in the t~.The:: YZAR chainge9 I` t to qirqe;t: tih6 F-Sm wamd'ing to 95F. Thea %kRClias- hmt iwt~o~ thnil a iO

?assutý7tion's and. protection: ire for the qSF..

2) Increase -the.!Gon eque~nces. of an, accident fivalualted in the g~o. Sao t c respnet uetoi1

~) reto hs poýR~t o akacdn f a ditfertnt t Ell W* ~hy eva trn tthdeiS t.;

Ho 'No acdidiirjtz difrittpai ~~e4 vablted in the i.1 inareasie the eprobAbilfity of. af %u-funatiao:,Df equipment in~pprtinnt to saf ety .&.zutAe in. tlh~ Sa~i ao. Thbe designo t~e. JO.ase CFA 5n ~ Dam*

, sec. ~ b obhiiqa. Th0.Ot bii hasb!ea ealtuated 'by the WRC f 6r ceirtar evdne.

design davign :eyent" do ~it erren¶tj.; iuV derin. eebt.T 0 o u.

1ob.- xWr TLt

di, 4hat 4ae.

&V44OW Y 44V&Qt h

aXce~

ramli~wit e fur th' c r.. +/-ncý e udpm Tomdanets that-:a~re 'ed fcr? the ~SF .tcr tq~t idlrt

.6C C~atc! the Wpoosib~tY fa VAlfmntuncdi-q' f;'d~~iei ~

No new~ fri1ur u~e ~a 1a~

t~1 Wilthze -FAkX'. 641~B

• ND. ~rhjs . M.~ aes Safty~a1%r4ys-tzii ].n s angeoints, ncr ai2 iq0* ln teý the nX nwnal.~ t.1000 P'~te;GIon feat.'ra tbrthe SSIer zfv -I depcribed clianea, to S ta .1an 9,*. 4.7 okO invbive any~ US~s br s~ftev 66inoerna. !4oý ý*17ic~

pp,- ci fiwti oft dhavgr',ýi arre raqL 16 pZCh" ~Ichme r FshR Sectioner.9.-.3.1 anifd%9.,6 .477 arpe to be chaftged to refhe-at tho- exis~tig liik~ntin b"Ii ýs dof n-e i n q an i iwa flcdn~~vn an~ -tt~tip--'Suha,SF zrh' ~this Ovent..

purrt-,tit' thdo ?SMRh soydral stiatements: eow~eening ~aacsee

-1664in evalts Mrnd iSF evr~~~~nts.ad pritectiorJ .6.r~ta ~t~n4I~n

~ as~4edin

.6 ;theý . ýTjjni~t6 of theI5~t aAdress exKl~lter# kailod PrntLtiOll~ of:-r Yar us- resut i h ri4pý :failurd Of -the-jpca.Fý-ee Dam- The Tfj~t~n~a d4.t -ne t o dAescribýe ýa FlýObac Istirc Fd1t'a:;n sud FLDD-MTws

iivtanýgrt Q d6s" go 'othe taxt beofto The Jýr ocw'be T~eiu~eaiýo rlatton -L cor'chti* infoirvatiom~ I nmtd t4v) reisf,ý at "tion e Bx

• A.2Ot

-ag Thb Qcn- Nlc~ham St'50-o -betxen 94.cno 6.a. 1 A t.

ie~~~de~~fe t to~/9~£ter 5~

-Cha~~o

.-!.c ~ ~ ~ o~. ~G~re o~'A ar2e stings~~~~~~~

tc:SR~rt tvtijkri 00ng 7)N1ft'cler d ~1$i~oni Sat~ J-6A. .to (el 464~ to 1.s D-aam~endd Oconee'Nc oear stt~mpiTo~ rf~~ ýtdcddnb the-C i~Iip Tito angab o-tt it.Q aintoiatioii o(Attahevnt. Jvn~~PE ozSv$aAce 5i) Letter dated 4/29/93 fromi a. T.. .9#01ce (DN*ke rto-ftr B TO~np

. LOOtD Y3Y

cfly

- c ib, I Date to'h~ ~ndxqproj;ýto, subi tta14-l da'zfor the ieojimso tr eneric Letter~ s9o, ~pple~ment A fXEE=

(DukeP-0 Povkr (to~), Ge v~io 1~) eter d'.Te /14/.94 frait R.4~

apvt (fl)ke~ 1owd. 'Coiipany)

~t6tb- NRC', xosiig ep.Onue to'era i4 fmTe a ligtt-o. dated~ ~ .Tzkimp~ la/1 (owke ~w~Cmc~y

..to th6'11RC prvidi4 rev.~~~t ~R ~~oe~ oei

15) M4emo 44e ~~4by.~.R~n Fil~ O~l9~w n'ttacie4 ela1.twiwib 02,-2.'l -OIab P_=Ate onziokI Ct'Z0Et.tv..

t); ivso FLOM D JWT

ý icialý ýniy -Sec ity ýtedlI o ti n Iti SeI6 -0104 Opeud9 vd-ns a ib w Pawijxe aana P"~n 7

j ~ i ~~fU h S~~~~~~~~~~~~~te dA SS~ilFld4 2 Mc i u 91Ii yilWk.~C'4Tee~MC u captbl o i sa d ar imethret E t ei.j 2 . bed~c4~

te MC'~ bak~Tb~ bke~-p0dc p~in ~ t~~ ~wur 1.p dto

-2 .'S Q'I4 4- NoLrm4., ind.opait& i~4 ~ owdfo aw-S~ od ~ taS Pm2=Pý-'t= od lTi~~

A fIt S~ bs ad ~~i ~ h S4e4~~ i h S~I~

2edi fitaoaS'-Vi 95rM~ bzwt'Lomtcm SY U the ast*EM i :wiR)th IONSz ý!6.-

14

A44k4tk4 Seoiovpmw.63A $yw'- '4t oeadepthioftfuucu, n I o flhoin'Rtviowal Se~ thOCdto z-I64.7 iýpoe~

>LOTRLv oatruak

~tugtitdb £lapsW94 d~nn eu~bypn ith-Mr71

~~~~~~~o~ tfMazonTr&~

m~ h eldn t~~i~~rzingm cxeta.Fddt to ..b orheyida aWEI:d Chop flre o Sbhriocsupn 1 st Ž

~~veengh 4ý&aii r4ont thet~fl ":6ti4onqc D il 1993 Statement:

(9ý6J in~~ Loin S"t (tn ocr

GWicia seOrl-ýurit~y " " "

i'd Iri c tigwvane WPId... -,with 2 .. Roti aw.i.

a s 2~~~~~~

4 T lortl

=ýt~szod Wn 6 2 w ..

3. ..... ....... cI..... m ~~

" s of thbe Vrof lc M ....m= . p..ai..?MP. . . . T. FSAR &Itrmsm"o n t

.2 ZrL-A t=nish~

n on itSE $wti tis ehafdr n .tkstnhmlsrs iS tb nTab= D 2 Looin~~m I.ewat.c

'T enathe diem Pr4 b S, tontrC lJi't' v*ý j ltsfrltattrTei 2 &iidias Mhe ioxMi 4tvolIe SS

'weti .Mci tmwaxy .7 Si t. shi*ihF pmavnim 2 aat*u~ i I* vza h IlTe SSE7"wil mba*blc 'itv 0ints mt hOzesbintdoiw cobdition, Punipt s a =w othve 'iJovuiiiieoia nto zw u lbd*I*i fr71=dw he*rAhzamd a'd ens* i*wl reinLfoiwuintech Mu dzeiiFlood;ic4'4diium o~4am tanidat#st{

2 Tbets skis L51,ixtorad geneka niieike mi ADt p=a(6~tsr-.wi bts she tu te 'penenion mn-hsI ileuthr&

'kphs kn nssm e

• ~Uz IT.,M lig Of-.***

SSEISMIC DESIGN

, , ,r * . r . . .ewrit n sp t L1 m m

T etsoneez'dcclpt seea. i acodenewilh Th.; pnnednnd ( -Guti £O. The mnoAf

- cainptvm MUntewrs

Attachment:

3, Applicabl~e portions of the current !Oconee FSAR with the regards to'the SSF and a Jocassee Dam failure. (5:pages total)

=JO .~m ..

2 Vow Ah -S~F wthk6w O'$~tMSL'=CUad; mo'b GLd1~SS ZIoi wmt, 0 Van~Oiirn 6yta rzn i~n w'

' SA.64 RepsmifMK w thi~ e n.%e Rt~i~~~l 2~~ ~ ~ ~ ~~ 4 ~o~~~~~~P a ~ddaad~utw n ~

o I--~o f

• 2. or~e~x0%m i dcn oiem lA~nmIQ6 ý;Ystb at ~ a~t mum ~ h

~ LflitioS I-P mqLFSW bv tta* rd a

2. ~ o parh bw.Ut~ mshr. rnýTr bpuaa rrm= tho fuvpýHO.¶ rO)211 %bus tFl iO,- th pand

~' 4ý iRii~

fi vI~t 29.6;5 OPERATION AND TESTING hT i3~ ao~nr w~ n~i~o ~p~1dt~~~wz

sikl u/tyit(*el ~itp~

~ ~ p ~~nfv~ihe diiPi~u~~) oir iubI mad's1 r( CC4O. LQO to'f~amri" ucnu~ or 5 ~ ~ ~ I mhIIalhl~kd brekeIi the Nic. C ud 4~

.hz f~rm MCC ýp; fcad~f~ ~~paf ~nn~i Pc~I 6_i hn iarUM IP in SDis i DI.oItw l.i qpcnnatw. UISC I PU erd konii a nirmql..(im4SS) to-ad xi~wy vladxSS Darig'kperm- 6" ole TIh'fmSkidi Ar pqIvror 4trfhi Ow 5:SF didseIlimnmrifor viultbc, SSF kxad

.IuStweUkn SS TJm~iuhtidby:Jkl& Ftlilcvilitnj(Ssv ý ~is mifa~innItc'nniie

.in i of4 d~ivMe genernwa rhciý S.SF hIm a neliCi f Cý:fvul oiiI~mT I Tvite WI iving Iliac co'ndiionsmtarc m)the 4, Wiid mq W.INt)AND TOf)NM)DO.LOADWS TL- ztnijgn wM4nduv~oiry for dri.i SSF, 11 95 mph.i at 10 tI. iibciv dw iom~ioal grotnd. 1h Taiima wvkcfly T:!fln"-isq'l- wind w iffi '.)rm'uniinn ituava LWJO.!1 emr; A gual5 fiLwlW ofmoitO di. uiikd fa rtcvhlni v~nd fiin,' I~h-- dcii lonuldo uwtd in Caii-dIlt lonlur~ido I-oil m"ig l' b~meue oufon wimd ktilm;ýwv Ciui'(k 17i wntv iv~, fbji~o Ciýti ui:

2. Tmi imbomwili qpwtj orlaron~die ii 64" m~ph

4. Tn~ indUC Liild PIUSLOt.initkiiii iis psi, mm r in aiirfs'eh

ý"W-IJE?.: 101YSI

aciUse ly -Se ýrity, atediýrm~at n

.UF~t Cisupwtr 9iOot4 Nksdear, SMifiw#

Th~ r~isdnar ti. tVfl*ew s mitso rolviim hWerim this ~sec1iatt Flooii Sqites -Ahw thm. Lý.ai KCOWtCnd' "_=: sitt dimtigncd will adeuawtc rnsigis to cnmr~n Mk;t',lhw PrsbLIN't mt P p1sknP Thc PSAR-add "IssisOoe~ ~ a:a ~

rijeln Il busvt maysin k vsflods Tj .to rinila nffct1;iw "iVerS, Wdue~n~dOshgd 3nd erusruirý ig.n p~b hc ',4F i%WiWE[it tbc tiw~bowsdnwy hs~oe Ln s 6 su'~si Ilannds wipi-s w!pv towJtW TiirdC iie r~sa~~i ihcS~Fst qTh1 Lbavg.nc -seaiaelfCmsl. In tk. co-wnt o flm~dk~h uc dv taxlu wtr cl -ihi heuitbwiLt is. 7,96:,ý 11 Sorwetb thc fnrurni eprectrr wasr .s1, j"b t'kth~ecmli

- inn s~~r~ lve~l r nstn hd S,51%. tr ~znic-ture 4will zul be inv~ will '41.11 s~ tha plans w:mpthe 3: wub an warm'np Reacoa wx pawcmu :25.A

• .111LA caatmm t, qSiT prvdcl .withf flm.xn cgiuual[louid Ma~lwhih ki ispqpt ith i vei~satcr 0A.i"O d i VhaSrI u be imri% u !fbtiSýPi A suirwzu onvcr,4w~ w"'I provid mv*8Anilm floen~rh kltsMfk ImOTE C-ION

• Theonhe pmstul ted sasos~zgIhy riatuwsj. Phwsnimmi merIosis rwtkr s .opsssie.5TeS~ r

&SlcdILI rvitsau 512 Ity' of lvilttih) gvrwmic nlii~st~Im tbisia~it cc as~xs TsblcqI

• Pesseihtiod are esksloaidw~icn deplss ~

rdd~d~ in cwsstsil vAismlIs iidifwhet loading 'abrn rurnssutfidPmyfiimua 6tudiieceN farmulaC t~pls Paietulno f1K N1Wdf f xd I dor M 2.0 K 1001 1171c-1P A prosm,i~v avansssci Amua~ iD Mndilipst Petry Frm'iuL--s 44

to :f ... Se d. n .t .Ro 9aht61 Firs Protection Cclus*ion Th.ONt lngi ' panuidd owne1tauin O~SrstalrIs ntratn schi&vc aii antuauin ifr .Shuldfvwn tunditnir&, by+otL{ig naakma ISv a im*iOl!i .r o-om*i.,por

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