ML13338A170

Assistance in Obtaining Information on Dams

ML13338A170
Person / Time
Site:	Peach Bottom
Issue date:	11/22/2013
From:	Massaro M Exelon Generation Co
To:	Geoffrey Miller Office of Nuclear Reactor Regulation
References
Download: ML13338A170 (12)

Text

AwExelon Generation, November 22,2013 Mr. G. Edward Miller,: Project Manager..

Projects Management Branch:

Japan Lessons-Learned Project Directorate Office of Nuclear Reactor Regulation Rockville, MD 20852

REFERENCES:

Iler Mr Millar Assistance in Obtaining Information on Dams:

Peach Bottom Atomic Power Station - Units 2 and 3 NRC Docket Nos. 50-277 and 50-278.

Facility Operating Ucense Nos. DPR-44 and DPR-56

1. NRC Letter, "Request for Information Pursuant to Title 10 of the Code of Federal Regulations 10 CFR 50.54(f) Regarding Recommendations:,.-

2.1, 2.3, and 9.3, of the Near-Term Task Force Review of Insights from the Fukushima Dal-ichi Acciden", dated March 12,2012..

2. JLD-ISG-2013-01, "Guidance For Assessment of Flooding. Hazards Due to Dam FailureP,, Interim Staff Guidance, Revision 0, July 29,2013.

Exelon Nuclear (Exelon) is re-evaluating flood hazards at its Peach Bottom Atomic Power Station (PBAPS) for the purpose of responding to the March 2012 Request for Information (RAI)

(Reference. 1).: As part of this effort, Exelon requests the assistance of the NRC to obtain the information needed to complete the Probable Maximum Flood and Dam Failure: Hazard Evaluations. In particular, Exelon requests that the NRC acts as the interface between the U. S.

Army Corps of Engineers (USACE) and Exelon, as outlined in section 1.5.3 of Reference 2....

This information is needed to support the flooding re-evaluation at PBAPS.

The specific information needed is identified in the attachment to this letter. This information is requested from the USACE by December 15, 2013. To coordinate data transfer, please contact Mr. Jesse Lucas at 717.456.4985.

This letter contajns no new regulatory commitments.

MichaelIJMassro Site Vice President Peach Bottom Atomic Power Station Attachments..

cc:

U.S. NRC Document Control Desk NRC Resident Inspector, Peach Bottom Mr. Chris Cook, U.S. NRC, Rockville MD:

ccn 13-81

..Au.W :

REQUEST FOR INFORMATION ARMY CORPS OF ENGINEERS OWNED DAMS IN SUSQUEHANNA RIVER BASIN Flooding Hazard Reevaluation of the Susquehanna River Basin Peach Bottom Atomic Energy Station I Conowingo Dam Power Station EXELON On behalf of EXELON, ENERCON and Gomez & Sullivan are performing hydrologic evaluations to characterize the Probable Maximum Flood for the Peach Bottom Atomic Energy Station /

Conowingo Dam Power Station.

There are a number of United States Army Corps of Engineers (USACE) flood storage projects in the Susquehanna River Basin. These projects include:

Almond Dam Alvin R Bush Dam

• Arkport Dam Cowanesque Dam Curwensville Dam

" East Sidney Dam George B Stevenson Dam Hammond Dam Joseph Foster Sayers Dam Joseph Foster Sayers Dam Howard Levee Raystown Dam

" Raystown Dam Hesston Dike

" Stillwater Dam Tioga Dam Whitney Point Dam To accurately characterize the hydrologic effects of these USACE storage projects, information is needed related to the storage capacities, discharge capacities, seasonal pool operating controls, and flood control operations. We do not necessarily need detailed information related to the construction of the dams, which might otherwise be considered protected information by homeland security. Rather, we need more schematic information, including:

1) General facility description and layout

2) Operations Manual, or portions of Operations Manual as available for release

3) Spillway information:

a) Gated Spillway(s): No. of gates, dimensions, inverts, discharge rating curves b) Gate Timing: how long does it take to open one gate? All gates?

c) Auxiliary Spillway(s): No. of gates (if any), dimensions, inverts, discharge rating curves

d) Emergency spillway(s): dimensions inverts, discharge rating curves

4) Tailwater Rating Curve (if available, and if the tailwater influences the gate discharge at any stage)

5) Storage Capacity Curve:

a) Indicate Elevation vs. Storage Curve b) Indicate Elevations of pool levels, such as Multipurpose Pool Level, Flood Pool, Surcharge Pool, Top of Dam (or other such designations, as appropriate for the project)

6) Seasonal Operational Guide Curves

7) Flood Operations Criteria:

a) Flood Storage / Release Criteria b) Flood Operations Curve

8) Inflow Design Flood (IDF) information for each dam

9) Spillway Design Flood (SDF) information for each dam

10) Historical pool level information (daily maximum or time series pool level)

11) Historical discharge information (daily maximum or time series flow discharge)

To provide a better understanding of the information request, some EXAMPLE FIGURES from other hydrologic evaluations are provided.

Note that these figures are for different dams/reservoirs; therefore, there is not a one-to-one correspondence to related elevations.

FIGURE 1 - EXAMPLE SPILLWAY RATING CURVE Figure 1 depicts an example gated spillway rating curve for a multi-gate spillway at a major dam project.

FIGURE 2 - EXAMPLE OPERATING DISCHARGE CURVE Figure 2 depicts how a gated spillway would be operated for the specific operating efficiency of the gates during a specific flood event.

The gate opening levels are adjusted for specific upstream and downstream targets in the dam operations procedures. This figure is provided to demonstrate the importance of understanding dam operations so that accurate simulations can be performed.

FIGURE 3 - EXAMPLE TAILWATER RATING CURVE Figure 3 depicts a tailwater rating curve that would be used to evaluate potential downstream influences on spillway capacities. For elevated spillways, tailwater may not influence spillway releases.

FIGURE 4 - EXAMPLE RESERVOIR STORAGE CURVE Figure 4 depicts the elevation vs. storage capacity curve for an example reservoir. The graph includes the pool elevations of the variously defined pool levels; in this case: the Multipurpose,

Flood, and Surcharge Pools. Note that other projects could use other definitions. Note that this figure also shows an assumed Initial Pool Level at the start of the PMF Event. In this case, the initial pool level was selected based on an applied criteria related to historical maximum seasonal pool levels.

FIGURE 5 - EXAMPLE SEASONAL OPERATIONAL GUIDE CURVE Figure 5 depicts the target curve for seasonal reservoir operations. A reservoir may be drawn down in anticipation spring thaw inflows.

FIGURES 6 and 7 - EXAMPLE FLOOD OPERATING CURVE Figure 6 depicts the operating curves for reservoir storage/discharge operations during an inflow flood. In this case, the reservoir release is prescribed based on the Pool Level Elevation and Flood Inflow Rate. Figures 6 & 7 depict two different flooding scenarios for the same dam. As demonstrated in the figures, the spillway release rates can be significantly different for different starting pool levels and inflow floods. This demonstrates that is very important to know the Flood Operating Procedures to accurately simulate the reservoir discharge during a particular flood event.

Not shown is potential operating criteria related to downstream flow/flooding conditions.

Some operation plans include release criteria based on downstream targets to help mitigate downstream flooding.

FIGURES

Tainter Gate Vernier Readina:

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50,000 100,000 150,000 200,000 250,000 Discharge (cfs)

FIGURE 1 SPILLWAY RATING CURVE

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FIGURE 2 TRAIL - CRITICAL STORM 1 OPERATING DISCHARGE CURVE

605 600 595 590 585 0

580 a,

Mu 575 40 570 565 560 555 550 0

10 20 30 40 50 60 AS&&

110 120 130 140 150 160 170 180 190 200 210 220 Discharge x 1000 (cfs) 230 240 250 260 FIGURE 3 TAILWATER RATING CURVE 0

0 m

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0, 1040 1030 1020 1010 1000 990 980 970 960 950 940 930 E4 10.31 Top ýf 13m E4 102!5.4 To F), of Sui cha rge 10 000

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Surcharge Storage 255,000 acre-ft Available Flood Storage 88,000 acre-ft Total Flood Storage 176,000 acre-ft 0

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100 300 400 age (Thousand acre-ft) 500 600 FIGURE 4 RESERVOIR STORAGE CURVE 02

665 I

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658 CURVE 657

~-656 A

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