LR-N14-0042, SL-012270, Revision 0, Salem Generating Station Flood Hazard Reevaluation, Page 1-8 Through Page 2-5
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PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 1-12 PSEGNAVD 03.07.78.8 2.9HistoricalHighWater(November1950)(a)MeanHigherHighWater(ReedyPoint,DE)(a)NorthAmericanVerticalDatumof1988 MeanLowerLowWater(ReedyPoint,DE)(a)HistoricalLowWater(December31,1962)(a)97.5 92.7 89.8 86.881.0 NottoScale 4.5 10%ExceedanceHighTide(a)94.30.8NationalGeodeticVerticalDatumof1929(0ft.msl)89.09.7SGSNominalSiteGrade99.5 11.7HCGSNominalSiteGrade101.5PSEG Nuclear, LLCFlooding ReevaluationDatum and Water Level RelationshipFIGURE 1.1-9a) Values developed as part of the PSEG Site Early Site Permit Application.
PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 1-13 1.2 CURRENT DESIGN BASIS FLOOD ELEVATIONS
Station structures have been designed to not only withstand extreme recorded water levels, but also postulated extreme conditions. The design-basis flood is the result of the probable maximum hurricane (PMH) surge with wave runup. The resulting estimated maximum stillwater elevation was 113.8 feet PSD (24.8 feet MSL) with maximum wave runup to elevation 120.4 feet PSD (31.4 feet MSL) for safety-related structures inside the sea wall. Maximum wave runup elevation on the service water intake structure was calculated to be 127.3 feet PSD.
The SGS UFSAR notes that the water body to the west of the site is considered to be a tidally affected estuary by the U. S. Geological Survey. As such, water levels are recorded by tidal gauges and no "flood record" is kept. The tidal flow in the site area for the CLB was estimated to
be more than an order of magnitude greater than the average fresh water flow in the site vicinity. Thus, maximum and minimum water levels that may be of concern to plant safety were derived through considerations of coastal environmental conditions rather than riverine conditions. Therefore flooding in streams/rivers and dam breaches and failures were not analyzed.
1.2.1 CLB Local Intense Precipitation
Local intense precipitation (LIP) was considered for design of yard drainage facilities and as a possible loading on critical structures. The Yard Drainage System was designed to pass the drainage associated with a rainfall rate of 4 inches per hour for a period of 20 minutes (based on 90 percent runoff from paved areas and 50 percent runoff from graded areas).
The site drainage system was evaluated to determine if a local probable maximum precipitation (PMP) storm could adversely affect safety-related facilities. Although the design basis selected for site drainage was less severe than a local PMP storm, it was determined that ground slopes in the area are away from safety-related structures, and runoff in excess of storm drainage inlet and piping capacity was not expected to cause water levels greater than a few inches above the ground surface. All doors and penetrations in the Class I (seismic) buildings are watertight up to Elevation 115 feet (PSD). The interior drains in the Auxiliary and Fuel Handling Buildings are independently piped to the Liquid Waste Disposal System and are not connected to the Yard Drainage System. It was concluded that such levels should not constitute a flood threat to safety-related facilities.
Roof drainage systems were designed to dispose of a maximum rainfall rate of 4 inches per hour for a period of 20 minutes through the Yard Drainage System. Roof slabs are watertight to prevent building interiors from being damaged by severe rainstorms. The slabs are designed to withstand a loading equivalent to a depth of water up to the full height of the building's parapet or roof curb. It was determined that the system prevents rainfall accumulations from exceeding the structural design bases of the roofs of safety-related buildings during storms as severe as a local PMP storm and was acceptable.
1.2.2 CLB Flooding in Streams and Rivers
Flooding in streams and rivers is not analyzed in the SGS CLB.
PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 1-14 1.2.3 CLB Dam Breaches and Failures
Dam failure is not analyzed in the SGS CLB.
1.2.4 CLB Storm Surge
Probable Maximum Hurricane (PMH) storm surges were calculated for the site using the bathystropic storm tide theory described by Marinos and Woodward (Reference 1-2). The hurricane surge was computed at the mouth of Delaware Bay and routed up the bay in accordance with a method described by Bretschneider (Reference 1-1).
Components of the stillwater level were 1) the mean low water depth, 2) the astronomical tide,
- 3) the rise in water level resulting from the hurricane's atmospheric pressure reduction, 4) the wind stress component perpendicular to the bottom contours (onshore wind components), 5) the wind stress component parallel to the bottom contours which produces a longshore flow that is deflected to the right (in the northern hemisphere) by the Coriolis forces, and 6) the initial surge (a slow general rise in sea level existing before the actual hurricane winds arrive).
Indices used to calculate maximum storm surge were taken in part from HUR 7-97 (Reference 1-5), where values were grouped according to defined coastal zones and by latitude within each zone. The parameters and characteristics were based on empirical observations, assumptions, and experience.
The PMH used in the analyses was a large radius, moderate forward speed hurricane which generated the maximum surge on the open coast. The quantitative meteorological parameters describing the PMH were: Central Pressure: 27.09 inches Hg Peripheral Pressure: 30.72 inches Hg Radius of Maximum Winds: 39 nautical miles Maximum Wind Speed: 132 miles per hour Forward Speed: 27 knots
A computer program developed by Dames and Moore was used for analysis. It is described by Marinos and Woodward (Reference 1-2). Input data to the computer program describing the storm and the bathymetric conditions included the basic parameters of the hurricane, an initial surge of 1 foot, wind friction factor, bottom friction factor (0.008), wind speed at various radial distances and angles of wind direction relative to the translational velocity vector of the hurricane, bathymetric traverse data and astronomical tide (5.6 feet).
As the PMH was moved along its postulated track, wind speed and direction at the site changed because of the effects of friction and filling over land and also because of the position of the storm center with respect to the site. The cross-wind effects were calculated for the six wind directions chosen for analysis. The six wind directions or fetches radiated downbay from the site at 15-degree intervals from the east bank of Delaware Bay. The calculations consisted of determining the corrected wind speed along the fetch, the cross-wind component of the wind speed, and the resulting cross-wind setup or drawdown. The wind speed was corrected to include the effect of the fetch distance from the storm center and also for friction and filling overland.
PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 1-15 The computed maximum surge elevation at the mouth of the Delaware Bay was 21.9 feet above mean low water. This surge included the effects of the astronomical high spring tide. The model surge hydrographs for Delaware Bay computed were then used to determine hurricane surge values at the Salem site as a function of time. The maximum stillwater elevation at the site was determined using a combination of the storm surge and the crosswind setup or drawdown for the 6 fetches chosen.
Independent surge estimates were developed for the SGS SER by NRC consultants. Their estimated maximum stillwater was at elevation 113.8 feet PSD, considering the complete range of PMH parameters coincident with the local high spring tide. The site hydrologic design parameters were developed using the recommended value.
The primary factors influencing maximum wave runup was the maximum wind speed over the water, the effective fetch length, and the average depth of water along the fetch. The values of these parameters used in the computations of wave heights and periods were determined for the fetches analyzed by: Determining the location of the center of the storm required to produce winds along the fetch, Calculating corrected wind speeds to account for friction and filling over the land and distance from the storm center to the fetch center, Calculating the still water elevation at the center of the fetch due to storm surge at the time the storm center is located to produce the maximum wind speed along the pre-selected fetch, Computing the average depth along the fetch.
The basic assumptions used in the analyses were: Storm generated waves from the open sea are dissipated at the mouth of Delaware Bay Steady state waves are generated along each fetch (these waves are independent of time) Only the area northwest of Ben Davis Point generates significant wave energy at the site
The PMH was located so as to produce maximum waves. In the vicinity of the site, the PMH winds had a maximum sustained wind velocity of 85 miles per hour from the southeast. With the surge level at 113.8 feet PSD, wave runup elevations on safety-related structures inside the sea wall were calculated to be a maximum of 120.4 feet PSD. Maximum wave run up elevation on the service water intake structure was calculated to be 127.3 feet PSD.
1.2.5 CLB Seiche
The CLB describes that resonance was not a necessary consideration due to the nature of the estuary upon which the site is located.
PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 1-16 1.2.6 CLB Tsunami
The CLB describes that the occurrence of tsunamis is infrequent in the Atlantic Ocean. There was no evidence of surface rupture in East Coast earthquakes and no history of significant tsunami activity in the region. Hence, the UFSAR concludes that the plant site would be subjected to any significant tsunami effect. The maximum expected tsunami would result in only minor wave action, and the maximum expected storm wave (PMH) effect was the critical factor in design.
1.2.7 CLB Ice Induced Flooding Ice barriers are provided for the service water intake structure. Surface ice jams do not exert direct structural loading. The barrier also enables the intake components to operate normally without the effect of ice.
1.2.8 CLB Channel Migration or Diversion
As the source of cooling water is the Delaware Estuary, no channel diversions need be considered.
1.2.9 CLB Combined Effects
Combined effect of different flood causing mechanisms is discussed in Subsection 1.2.1 through 1.2.8, where applicable.
1.2.10 CLB Associated Effects Reference 1-6 defines "Flood height and associated effects" as:
"The maximum stillwater surface elevation plus the following factors: wind waves and run-up effects; hydrodynamic loading, including debris; effects caused by sediment deposition and erosion; concurrent site conditions, including adverse weather conditions; groundwater ingress; and other pertinent factors."
Inclusion of wind waves and run-up effects is discussed in Subsection 1.2.9; discussion of the remaining items, as addressed in the CLB, is provided below.
1.2.10.1 Hydrostatic and Hydrodynamic Loads
The current licensing basis for SGS (Reference 1-7) includes evaluation of the effects of hydrostatic and hydrodynamic loads on all critical safety related structures. The loading combinations evaluated in the current design basis are presented in Table 1.2-2. Per SGS UFSAR Section 3.4.3.1 (Reference 1-7), "All watertight doors and structural walls can withstand the static and dynamic effects associated with a storm that produces a stillwater level of Elevation 113.8 feet PSD with wave runup to Elevation 120.4 feet PSD". In addition, SGS UFSAR Section 2.4.5.6 states "maximum wave runup elevation was calculated to be 120.4 feet PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 1-17 PSD on critical structures inside the sea wall and 127.3 feet PSD on the service water intake structure." Therefore, it is considered that external watertight doors can withstand the same wave loading combinations the respective walls experience.
1.2.10.2 Debris Loads
Impact loads from floating flood borne debris are not analyzed in the SGS CLB.
1.2.10.3 Erosion and Sedimentation
Effects of erosion and sedimentation during extreme flooding events are not analyzed in the SGS CLB.
1.2.10.4 Concurrent Site Conditions
The current licensing basis for SGS (Reference 1-7) does not specifically discuss evaluation of concurrent site conditions, such as storm conditions during the event. However, as discussed in Section 1.5, the flood protection features for SGS do not require operator action outside of flood protected structures concurrent with the severe storm event. All outside actions (e.g., traveling to the service water intake structure and closing watertight doors) take place prior to the onset of the inundation portion of the flood event.
1.2.10.5 Groundwater Ingress
The current licensing basis for SGS (Reference 1-7) indicates the nominal groundwater level is 96 ft. PSD. Below grade structures at SGS are designed to mitigate the effects of the continuous presence of groundwater through the use of flood protection features including penetration seals, waterproofing and waterstops. The SGS flood protection features are rated to elevations greater than the design basis flood, further discussed in Reference 1-3.
1.2.10.6 Other Pertinent Factors The other pertinent factor for flood causing mechanisms at SGS is the flood event duration.
Flood event duration is defined in Reference 1-6 as the length of time the flood event affects the site, beginning with conditions being met for entry into a flood procedure or notification of and impending flood (e.g., a flood forecast or notification of dam failure), including preparation for the flood and the period of inundation, and ending when water has receded from the site and the plant has reached a safe and stable state that can be maintained indefinitely. The flood protection features at SGS are designed as permanent features and therefore, are not affected by the period of inundation and recession of flood waters from the site. The preparation for a severe weather event is covered both administratively via procedure and through Technical Specification Action Statements at SGS. Further discussion of the action levels associated with implementing flood protection features is provided in Subsection 3.10.6.
PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 1-18 Table 1.2-1 Postulated Flood Producing Phenomenon Flooding Mechanism Still Water Height (PSD) Max Flood Height (PSD) SGS UFSAR Section Local Intense Precipitation (PMP) Evaluated as Not Applicable - Design rainfall rates for site drainage system provided.
2.4.3.1 Flooding in Streams and Rivers (PMF) Evaluated as Not Applicable 2.4.3 Dam Breaches and Failures Evaluated as Not Applicable 2.4.4 Probable Maximum Surge 113.8 120.4 (Powerblock) 127.3 (SWIS) 2.4.5 Seiche Evaluated as Not Applicable 2.4.5.5 Probable Maximum Tsunami Not subject to any significant tsunami effect 2.4.6 Ice Induced Flooding Evaluated as Not Applicable 2.4.7 Channel Migration or Diversion Evaluated as Not Applicable 2.4.9 PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 1-19 Table 1.2-2 Storm Surge Wave Loading Sheet 1 of 3 Building Wall ID Breaking Wave Loads (kips/ft) Broken Wave Loads (kips/ft)
Static load Dynamic load Total Load Static load Dynamic load Total Load AB 9.82 20.00 29.82 13.19 1.31 14.50BC 12.60 53.90 66.50 16.93 3.24 20.17CD 9.82 20.00 29.82 13.19 1.31 14.50DE 12.60 53.90 66.50 16.93 3.24 20.17AF 9.82 20.00 29.82 13.19 1.31 14.50FG 9.82 20.00 29.82 13.19 1.31 14.50GH 9.82 20.00 29.82 13.19 1.31 14.50Unit 1 Fuel Handling HJ 9.82 20.00 29.82 13.19 1.31 14.50AB 9.82 20.00 29.82 13.19 1.31 14.50BC 12.60 53.90 66.50 16.93 3.24 20.17CD 9.82 20.00 29.82 13.19 1.31 14.50DE 12.60 53.90 66.50 16.93 3.24 20.17AF 9.82 20.00 29.82 13.19 1.31 14.50FG 9.82 20.00 29.82 13.19 1.31 14.50GH 9.82 20.00 29.82 13.19 1.31 14.50Unit 2 Fuel Handling HJ 9.82 20.00 29.82 13.19 1.31 14.50AB 9.82 20.00 29.82 13.19 1.31 14.50BC 12.60 53.90 66.50 16.93 3.24 20.17 Unit 1 Penetration Area CD 9.82 20.00 29.82 13.19 1.31 14.50 PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 1-20 Table 1.2-2 Storm Surge Wave Loading Sheet 2 of 3 Building Wall ID Breaking Wave Loads (kips/ft) Broken Wave Loads (kips/ft)
Static load Dynamic load Total Load Static load Dynamic load Total Load AB 9.82 20.00 29.82 13.19 1.31 14.50BC 12.60 53.90 66.50 16.93 3.24 20.17 Unit 2 Penetration Area CD 9.82 20.00 29.82 13.19 1.31 14.50AB 3.66 14.55 18.21 N/A N/A N/A (b)BC 9.82 45.90 55.72 13.19 3.00 16.19CD 3.66 14.55 18.21 N/A N/A N/A (b)DE 3.66 14.55 18.21 N/A N/A N/A (b)EF 3.66 14.55 18.21 N/A N/A N/A (b)GH 12.60 53.90 66.50 N/A N/A N/A (b)HI 9.82 20.00 29.82 13.19 1.31 14.50IJ 3.66 14.55 18.21 N/A N/A N/A (b)KL 3.66 14.55 18.21 N/A N/A N/A (b)LM 3.66 14.55 18.21 N/A N/A N/A (b)MN 3.66 14.55 18.21 N/A N/A N/A (b)Auxiliary Building AN 3.66 14.55 18.21 N/A N/A N/A (b)AB (a)49.93 31.47 81.40 N/A N/A N/A (a)BC 13.51 76.00 89.51 N/A N/A N/A (b)CD 9.82 2.60 12.42 13.20 0.17 13.37 SWIS AD 2.01 6.24 8.24 N/A N/A N/A (b)
PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 1-21 Table 1.2-2 Storm Surge Wave Loading Sheet 3 of 3 a) Non-breaking wave forces are considered on the full length of SWIS West wall. b) Breaking wave force values used for the full length of the wall.
PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 1-22 1.3 FLOOD-RELATED CHANGES AND FLOOD PROTECTION CHANGES
The plant design features and their functional requirements that provide protection against the design basis external flood mechanisms are provided in the UFSAR (Reference 1-7). The credited flood protection related attributes of the overall plant configuration that support the design for mitigation against external flooding have not changed from the time of initial licensing.
Enhancements to procedural guidance supporting the implementation of protective actions against external flooding have been made over time. The SGS Flood Protection Feature Inspections (Reference 1-3) found that the SGS flood protection active and passive features, e.g., walls, floors, roofs, penetration seals, doors, sump pumps, check valves, etc., were confirmed to be installed per design, functional, in good material condition, and appropriately controlled procedurally to ensure continued functionality. Changes to the hydrosphere around
the PSEG Site and physical changes to the PSEG Site (e.g., security changes, buildings, etc.) are discussed in Section 1.4.
PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 1-23 1.4 CHANGES TO THE WATERSHED AND LOCAL AREA
Local area changes have been minimal since plant operation began at the site. Offsite areas within 5 miles of the plant to the east remain dominated by the open waters of Delaware Bay and low coastal wetlands to the east and west of the bay. Much of these coastal wetlands are under state ownership and managed as wildlife areas that are protected from future development. Additionally, most of the land on the New Jersey side within 2 miles of SGS is owned by PSEG, the USACE, or the New Jersey Department of Environmental Protection. Most of the privately owned land within 5 miles is managed for agricultural production and/or private
access hunting/fishing.
The USACE is authorized by Congress (Water Resources Development Act of 1992, modified in 1996) to deepen the existing Delaware River Federal Navigation Channel from 40 ft. to 45 ft.
from Philadelphia, PA, and Camden, NJ, to the mouth of the Delaware Bay, with appropriate bend widening. This project is partially completed with a target completion in 2017.
On site, major changes include the addition of HCGS, the Materials Center, Low Level Radwaste, Nuclear Department Administration, Processing Center and Security Entrance buildings. Additionally, a security Vehicle Barrier System (VBS) has been added around the plant as well as the Independent Spent Fuel Storage Installation (ISFSI) storage area, which is inside the VBS and north of the HCGS Reactor Building. There have been no changes to site grade.
PSEG Power, LLC, and PSEG Nuclear, LLC (PSEG) submitted an ESP Application for a new plant located north of HCGS. The location and design of stormwater management systems for the new plant have not been determined, as discussed in the PSEG ESP Application. In general, the stormwater management system developed for new plant facilities will be integrated with the existing facilities. The new plant would modify the current site layout but the changes are not expected to impact the flooding behavior of the site.
PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 1-24 1.5 CURRENT LICENSING BASIS FLOOD PROTECTION AND MITIGATION FEATURES
Passive and active flood protection features are credited in the CLB. Details of these features
are provided in Reference 1-3. The SGS flood protection features are primarily designed to be permanent.
Passive incorporated flood protection features include the following: The containment is watertight and can withstand the static and dynamic loads associated with a storm producing stillwater level of 113.8 feet PSD and the corresponding wave runup to 120.4 feet PSD The portion of the service water intake enclosing the pumps, motors, and vital switchgear is watertight up to Elevation 126.0 feet PSD with wave runup protection to Elevation 128.0 feet PSD. The service water intake can also withstand the static and dynamic effects of the storm. The Auxiliary Building is watertight up to Elevation 115 feet PSD. All doors in the outer Auxiliary Building walls below Elevation 120.4 feet PSD are watertight. All watertight doors and structural walls can withstand the static and dynamic effects associated with a storm that produces a stillwater level of Elevation 113.8 feet PSD with wave runup to Elevation 120.4 feet PSD. Conduit penetrations above Elevation 115 feet PSD and below Elevation 120.4 feet PSD are packed to eliminate gross inleakage during the storm. The main steam and feedwater pipe penetration area is watertight below Elevation 120.4 feet PSD. The structural walls and watertight doors are also capable of withstanding the static and dynamic effects of the storm which produces a stillwater level of Elevation 113.8 feet PSD and wave runup to Elevation 120.4 feet PSD. All flood barrier penetrations in the Class I (seismic) buildings are watertight up to Elevation 115 feet PSD. The buoyancy effect of ground water has been included in the assessment of the sliding and overturning potential of the Category I structures. Hydrostatic loadings from the hurricane condition were applied to the structures to check their stability. The design and placement of the protective rockfill dike located along the portion of the Delaware estuary is such that it is subjected to maximum wind wave forces, thereby limiting the wave runup levels at the safety related structures and equipment to Elevation
120.4 feet PSD. The protective dikes are south of the power block between the Salem barge slip and the Salem circulating water intake structure, between the Salem circulating water and service water intake structures, and North of the Salem service water intake structure. The shoreline protection and dike system is inspected by station operating personnel prior to storms and hurricanes and following the passage of such storms and hurricanes.
Additionally, a more complete annual inspection is conducted both by boat and from the dike itself. The station security forces also make regular patrols of these areas as part of their surveillance duties, and are instructed to report any abnormalities observed in the
structure.
Active incorporated flood protection features include watertight doors. In the event of rising water levels, all watertight doors will be closed to maintain watertight integrity. SGS Technical Specifications specify the flood levels at which (1) watertight integrity will be established (at which time flood protection procedures will be initiated on a site-wide basis to protect the plant PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 1-25 from flood waters) and (2) plant shutdown will be initiated. All flood barrier doors in the Class I (seismic) buildings are watertight up to Elevation 115 feet (PSD). Closure of the Technical Specification Protective Doors is controlled administratively when the River Water Level
exceeds Elevation 97.5 feet PSD.
Temporary passive and active flood protection features are not credited in the SGS CLB.
PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 1-26 1.6 ADDITIONAL SITE DETAIL
There are no additional site details.
PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 1-27 1.7 References
1-1 Bretschneider, C.L., Hurricane Surge Predictions for Delaware Bay and River , Beach Erosion Board, U.S. Army Coastal Engineering Research Center, Misc. Paper No. 4-59, November 1959.
1-2 Marinos, G. and Woodward, J. W., Estimation of Hurricane Surge Hydrographs , American Society of Civil Engineers, Journal of Waterways and Harbors Division, Vol.
94, No. WW2, pp. 189-216, 1968.
1-3 PSEG Nuclear LLC, "Salem Generating Station Response to Recommendation 2.3: Flooding Walkdown of the Near-Term Task Force Review of Insights from the Fukushima Dai-lchi Accident," Letter No. LR-N12-0370, dated November 26, 2012.
1-4 PSEG Power, LLC and PSEG Nuclear, LLC (PSEG), Early Site Permit Application-PSEG Site , Revision 2, 2013.
1-5 U.S. Dept. of Commerce, Interim Report Meteorological Characteristics of the Probable Maximum Hurricane, Atlantic and Gulf Coast of the United States: Environmental Science Services Administration, Memorandum HUR 7 97, May 7, 1968.
1-6 U.S. Nuclear Regulatory Commission, "Guidance for Performing the Integrated Assessment for External Flooding," JLD-ISG-2012-05, November 30, 2012.
1-7 PSEG Nuclear LLC, "Salem Generating Station Updated Final Safety Analysis Report,"
Revision 27, 2013.
1-8 PSEG Nuclear LLC, "Calculation of PMH Flood Wave Forces," Calculation 6S0-1807, Revision 0, 1995.
1-9 U.S. Nuclear Regulatory Commission, Request for Information Pursuant To Title 10 of The Code of Federal Regulations 50.54(f) Regarding Recommendations 2.1, 2.3, And 9.3, of The Near-Term Task Force Review of Insights from The Fukushima Dai-ichi Accident, March 12, 2012.
PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 2-1 1. 2.0 FLOODING HAZARD REEVALUATION Flooding hazards from various flood-causing mechanisms were evaluated for Salem Generating Station (SGS) Units 1 and 2 in accordance with Enclosure 2 of the NRC's March 12, 2012, 50.54(f) Request for Information Letter, which identifies the requirements for the flooding hazard reevaluations associated with NTTF Recommendation 2.1. The flooding hazard reevaluation for SGS follows, where appropriate, the hierarchical hazard assessment (HHA) process described in NUREG/CR-7046. As explained in Attachment 1 to Enclosure 2 of the NRC's 50.54(f) letter, HHA is a progressively refined, stepwise estimation of the site-specific hazards that evaluates the safety of the site with the most conservative, plausible assumptions consistent with available data. Consistent with the HHA approach, flooding mechanisms that are determined to not be the controlling factors for external flood hazards will be screened out using order-of-magnitude analysis or qualitative assessments, where appropriate, with conservative assumptions and physical reasoning based on the physical, hydrological and geological settings of the site. The flooding hazards that can potentially affect the PSEG Site are well understood and in cases where it is known external flooding can exceed site grade (e.g., local intense precipitation and storm surge) a detailed analysis was undertaken without progressing through the stepwise HHA
approach.
The SGS flooding reevaluation applies the flooding hazard analysis approaches, regulatory guidance, and methodologies used in support of the preparation of the PSEG Site Early Site Permit Application (ESPA) Site Safety Analysis Report (SSAR) for a future unit at the site, which are also augmented by recent regulatory guidance. The principal regulatory guidance related to flooding hazard evaluations include:
Regulatory Guides 1.59, 1.102, and 1.206 Standard Review Plan (NUREG-0800) Sections 2.4.1 to 2.4.7 and 2.4.9 to 2.4.10 NUREG/CR-7046 NUREG/CR-7134 NUREG/CR-6966 ANSI/ANS-2.8-1992 JLD-ISG-2012-06 JLD-ISG-2013-01
PSEG submitted an application for an ESP for the PSEG Site on May 25, 2010. The application is revised annually and is currently under NRC revi ew. As part of this review, in October 2012 NRC requested PSEG reevaluate their storm surge hazard in light of the Fukushima events. The PSEG response to this request, submitted in November of 2013, forms the basis for Section 2.4 of this report. The flooding causal mechanisms and design basis flood elevations described in the PSEG Site ESPA are applicable to the flood reevaluation for SGS because SGS and the PSEG Site are located physically adjacent to each other and share a common site. The analyses described here are performed for the entire site, including HCGS, as the flooding events impact the entire site area. Throughout this report the term PSEG Site is defined to mean the entire property, including SGS, HCGS and the potential new plant.
This chapter describes in detail the reevaluation effort for each plausible flooding mechanism and the potential impacts to the safety-related SSCs of the plant: flooding impacts due to local intense precipitation (Section 2.1), flooding in streams and rivers (Section 2.2), dam breaches PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 2-2 and failures (Section 2.3), storm surge (Section 2.4), seiche (Section 2.5) tsunami (Section 2.6), ice induced flooding (Section 2.7), channel migration or diversion (Section 2.8), combined flood effect (Section 2.9), and associated effects of flooding (Section 2.10).
PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 2-3 2.1 LOCAL INTENSE PRECIPITATION
Local Intense Precipitation (LIP) is the measure of the extreme precipitation (high intensity/short duration) at a given location. Generally, for smaller basin areas, shorter storm durations produce the most critical runoff scenario as the amount of extreme precipitation decreases with increasing duration and increasing area. Also, for small areas, short times of concentration result in high intensity rainfall which creates a larger peak runoff. Therefore, the shorter storm over a small watershed will result in higher flow rates for the SGS LIP analysis. The LIP
analysis prepared for SGS is part of an overall analysis prepared for the PSEG Site, including the entire property on which SGS and HCGS are co-located.
2.1.1 LIP Intensity and Distribution
As prescribed in NUREG/CR-7046 (Reference 2.1-1), the LIP used in the analysis is the 1-hour, 1-square mile probable maximum precipitation (PMP) at the SGS site location. Parameters to estimate the local intense precipitation are from the Hydrometeorological Report 52 (HMR-52, Reference 2.1-2). Point rainfall (1-square mile) LIP depths for durations of one hour and less are determined using the charts provided in HMR-52. HMR-52 is used to determine the 1-hour duration LIP estimates based on the location of the drainage basin. Using Figure 24 in HMR-52 and the site location, the 1-hour, 1-square mile precipitation depth estimate is 18.1 inches. HMR-52 Figures 36, 37, and 38 are used to estimate the 5-minute, 15-minute, and 30-minute 1-square mile precipitation depths. The LIP depths for the site are presented in Table 2.1-1.
A cumulative rainfall distribution curve is then plotted from the 5-minute, 15-minute, 30-minute, 1-hour 1-square mile precipitation depths as shown on Figure 2.1-1. A synthetic hyetograph for the 1-hour LIP is developed from cumulative precipitation depths shown in Table 2.1-1, in accordance with methodology presented in NUREG/CR-7046. A five-minute time step is used such that the most intense 5-minute interval is placed at the beginning of the distribution, and then the successively diminishing depth intervals are placed on after the initial high point of the distribution. The rainfall distribution synthetic hyetograph for the 1-hour (60-minute) LIP is presented graphically in Figure 2.1-2.
2.1.2 LIP Model Development
Two-dimensional modeling is often the most accurate approach for assessing hydrologic and hydraulic conditions in areas where flood volume dictates the area of inundation or when flow is unconfined with a high degree of flow path uncertainty. It is appropriate for this LIP analysis, which is characterized by shallow, overland flow in a developed area with walls, building obstructions, and flow path uncertainty resulting from a LIP event.
FLO-2D (Version 2009.06, Reference 2.1-3) is used to conduct the LIP analysis. FLO-2D is a process-based physical model that routes rainfall-runoff and flood hydrographs over unconfined flow surfaces or in channels using the fully dynamic wave approximation to the momentum equation. It has a number of components that makes it capable of simulating sheet flow, obstructions, sediment transport, spatially variable rainfall, infiltration, floodways, and many other flooding details. Predicted flow depth and velocity between the grid elements represent average hydraulic flow conditions computed for a small time-step (on the order of seconds). Typical applications have grid elements that range from 10 ft. to 500 ft. on a side and the number of grid elements is unlimited (Reference 2.1-3).
PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 2-4 The PSEG Site topography is based on the recent 2008 site survey (Reference 2.1-5). A walkdown of the PSEG Site in 2013 further refined the 2008 data to document any significant changes to structures or buildings since the topography data was acquired. The topographic mapping was created using Light Detection Radar (LiDAR) with a resolution of 1-foot. The 1-foot contour dataset is used to establish grid elevations in the model. Several data processing steps are performed using ArcGIS to convert the contour data into a representative surface in FLO-2D. First, the contour dataset is converted to a triangulated-irregular-network (TIN) to represent the bare ground surface of the site using 3D Analyst Tools in ArcGIS. The TIN is then converted to an ASCII raster dataset with a resolution of 5 x 5 feet. The ASCII raster format is fully compatible with the FLO-2D model. Using the ASCII raster, an average grid cell elevation was computed and assigned to each grid cell in the model (i.e., one elevation value per grid cell to represent the average ground elevation in that cell).
Once the initial grid elevations were established, the grid cell elevations within many of the building footprints were raised to a nominal roof elevation, well above potential LIP flood levels, to represent an obstruction to overland flow. This was done for large and small buildings that are located near critical doors and buildings or directly in critical LIP flow paths. Small buildings located far away from the area of interest, on high ground above LIP flow paths, or upstream of the critical plant areas were not represented in the model as obstructions to flow, and no adjustments were made to the ground elevation at these locations.
The PSEG Site FLO-2D model domain is presented as Figure 2.1-3. Figure 2.1-3 presents the location of all of the buildings that were represented in the FLO-2D model as obstructions to LIP
runoff.
Floodplain outflow grid elements were established in FLO-2D around the entire model domain. These outflow grid elements totally remove flow volume from the model. The west and south model boundaries are located along the Delaware River and Delaware Bay, while the north and east boundaries were established at a buffer distance beyond the watershed boundary impacting the site. The boundary condition considered at the outflow grid elements in the FLO-2D model is based on normal depth. This is appropriate for the LIP analysis since the surrounding topography directs runoff away from the site beyond the model domain, and the normal depth boundary condition will not be affected by water levels and flow conditions
downstream of the model boundary. Additionally, the site is elevated above the Delaware River and the Delaware Bay, and there are no combined events criteria that require consideration of elevated flood levels in adjacent bodies of water coincident with the LIP event. Thus, the water levels resulting from the LIP analysis will not be impacted by backwater from the Delaware River and Delaware Bay. Refer to Figure 2.1-3 for an overview of the model domain and outflow
boundary.
2.1.2.1 Surface Infiltration Per NUREG/CR-7046 recommendations, the following assumptions were applied to the LIP
analysis:
Runoff losses were ignored during the local intense precipitation event (i.e., no infiltration) in order to maximize the runoff and resulting flood elevations from the event.
PSEG Nuclear LLC Salem Generating Station Flood Hazard Reevaluation
SL-012270 Revision 0 Project No.: 12800-213 Page 2-5 Conservatively, all active and passive drainage system components on the site were considered nonfunctional or clogged for the analysis of LIP flooding. The model is based primarily on overland flow over the whole plant site and does not credit any flow through gravity storm drain systems, roof drains, pipe networks, culverts, etc.
2.1.2.2 Surface Roughness Manning's roughness coefficients (n-values) are assigned to the model grid cells based
primarily on aerial imagery and site survey described in Subsection 2.1.2. The Manning's n-values and classifications were verified based on local land cover and land use observed during the on-site field investigation. The land use classifications and Manning's n-values are shown in Table 2.1-2, which are based on guidance from the FLO-2D Reference Manual (Reference 2.1-3).
The n-values used in the FLO-2D model are different than n-values used for steady, uniform flow in prismatic channels. The n-values in a FLO-2D model account for two dimensional flow, vegetation, surface irregularity, and non-uniform, unsteady flow. All three of the land use categories in Table 2.1-2 have been assigned Manning's n-values that are on the lower end of the range provided in the FLO-2D reference manual. This is primarily due to observations during the site visit and the fact that the site is developed and actively maintained, rather than being in a naturally vegetated or undeveloped condition.
The grass near critical buildings is short and only located in a few isolated locations. Grass and vegetation located far away from critical buildings is not essential in the analysis or results.
Developed/paved areas are highly compacted and covered with gravel or pavement/concrete.
Since gravel has a higher roughness coefficient than concrete, an average Manning's n-value was used from the range of values. The debris/obstruction land use category was used in a relatively small area at the southern end of the site at the Salem barge slip area to represent obstructions that were identified in this area during the site visit, such as jersey barriers, fencing, large boulders, etc. Since there were some gaps and openings where flow can still be conveyed, a lower n-value in the range of values was selected.
It is important to note that the area of inundation and flood levels in a FLO-2D model are much more dependent on the volume of the rainfall/runoff rather than on the peak discharge or Manning's n-values. Thus, the model is relatively insensitive to slight variations in Manning's n.
The Manning's n-value classifications in the FLO-2D model domain are shown on Figure 2.1-4.
2.1.2.3 Obstructions and Impediments to Flow
As discussed in Subsection 2.1.2, the buildings in the model domain were represented by raising the grid cell elevation within the building footprint. Rainfall was applied to these building locations and runoff was allowed to flow off the roof onto adjacent ground. Storage on top of the roofs and routing through roof drainage systems is conservatively neglected, and runoff from building roofs contributes directly to overland flow adjacent to the buildings. The elevated grid cells prevent overland flows from being routed "through" the buildings.
Area and width reduction factors (ARFs, and WRFs, respectively) were used to represent the HCGS cooling tower location in the model. These reduction factors were appropriate in the cooling tower area since rainfall in this area will not contribute to overland flow because