REDACTED VERSION WITHOUT PROPRIETARY,

COMPANY CONFIDENTIAL INFORMATION

ENGINEERING RESPONSE TO UNITED STATES

ENVIRONMENTAL PROTECTION AGENCY

CW A 308 LETTER

PILGRIM NUCLEAR POWER STATION

PLYMOUTH, MASSACHUSETTS

PREPARED AND SUBMITTED ON BEHALF OF:

nter,

Entergy Nuclear Generating Company

Pilgrim Nuclear Power Station

600 Rocky Hil Road

Plymouth, MA 02360-5508

By:

Enere.

Oees, 

Inc.

500 TownPark Lane, Suite 275

Kennesaw, GA 30144

Input Provided By:

Normandeau Associates, Inc.

NERA Economic Consulting

June 2008
Pilgrim Nuclear Power Station

Response to United States Environmental Protection Agency CW 308 Letter

Table of Contents

1 Background, Introduction, and Scope..................................................................................... 

Background and Introduction......................................................................................... 

Scope............................................................................................................................... 1

PNPS and Cooling System Description.................................................................................. 2

PNPS Overview.............................................................................................................. 2

Source Water Body......................................................................................................... 2

Cooling Water Intake Structure Description.............. ..................................................... 4

Discharge System.......................................................................................................... 12

Cooling Water Process Flow Diagram ......................................................................... 13

Recent and Planned Plant Modifications ...................................................................... 13

Projected Retirement Plans ........................................................................................... 14

Description of Plant Processes............................... ,.............................................................. 15

Nuclear Steam Supply System Operation..................................................................... 15

Condenser Operation.................................................................................................... 15

CWIS Operation............................................................................................................ 16

3.4 Effluent Treatment Operations..................................................................................... 16

Evaluation of Existing CWIS Technologies and Operational Measures .............................. 17

Evaluation of Existing CWIS.......... .............................................................................. 18

4.2 Percent Reductions from Baseline for Existing CWIS .................................................

Evaluation Methodology for Alternatives....... ................ ............................................. 23

5 Closed-Loop Cooling............................................................................................................ 25

Meteorological Data...................................................................................................... 25

5.2 PNPS Administrative/Continuous Operation Limits .................................................... 26

5 .3 Closed-Loop Operational Parameters...................... .............. ...................... ................. 29

5.4 Closed-Loop Operational Parasitic Losses ...................................................................

PEPSE ModeL............................................................................................................... 30

Baseline Closed-Loop Operation Parameters ............................................................... 31

Reduced Power Operational Parameters.................................. 00.......... ......................... 31

Summary of Reduced Power Operational Impacts....................................................... 33

Alternative Impingement/Entrainment Reduction Technologies ......................................... 35

Modified Traveling Screens and Fish Handling and Return Systems .......................... 35

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6.2

6.3

Screening/Barrier Technologies.................................................................................... 41

Alternative Intake Location.......................................................................................... 43

Flow Reduction..................................................................................................................... 45

7 . Variable Speed Pumps (VSPs)........ .................... ........................ .................................. 45

Assisted Recirculation.................................................................................................. 53

Grey Water.................................................................................................................... 54

Conclusions........................................................................................................................... 56

References.................................................................................................................... ......... 58

List of Attachments

Attachment 1 - Major Components; Vendor Data and References

Attachment 2 - Assisted Recirculation

Attachment 3 - Closed-Loop and Variable Speed Pump Station Performance

Attachment 4 - Cost Assessments

Attachment 5 - Figures

Attachment 6 - Normandeau Biological Input

Attachment 7 - Grey Water Cooling

Attachment 8 - Offshore Intake

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Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Table 1

Table 2

Table 3

Table 4

Table 5

Table 6

Table 7

Table 8

Table 9

Table 10

Table 11

Table 12

Table 13

Table 14

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Response to United States Environmental Protection Agency CW A ~308 Letter

List of Figures

Aerial View of PNPS .................................................................................................. 3

Traveling Water Screen Operation............................................................................. 7

Simplified Schematic ofBWR Plant Operation ....................................................... 15

Turbine Building....................................................................................................... 28

Modified Ristroph Screen......................................................................................... 36

Multi-Disc Screen..................................................................................................... 38

Typical WIP Screen Arrangement................ .................................... ........................ 39

Typical WIP Screen - Side View................ ............................................................. 40

Typical Velocity Cap Flow Direction ............................. .......................................... 44

Incremental Reduction in Annual EA Entrainment Using VSP Operation

Flow Reduction......................................................................................................... 51

Incremental Reduction in Anual EA Impingement Using VSP Operation

Flow Reduction......................................................................................................... 52

List of Tables

History of Key CWIS Components at PNPS ..........."............................................... 13

PNPS Baseline Monthly EA Entrainment and Impingement ................................... 18

PNPS Baseline EA Impingement Survival - Fish Return Sluiceway and Low

Pressure Wash System........ ...................................................................................... 19

PNPS Flow Reduction from Baseline.................... ............................................. ...... 20

PNPS Baseline EA Entrainment Reduction by Month............................................. 21

PNPS Baseline EA Impingement Reduction by Month ...........................................

Net Power Generation Loss ....... ................... ....................................................... ..... 32

Closed-Loop Limiting Operation Parameters................ ........................................... 33

Hourly Maximum Active Power Loss (MW e) Attributed to Flow Reduction

- 118 F Hotwell B Limit.......................................................................................... 47

VSP Operation Achievable Circulating Water Flow Reduction at Specific

Electrical Output Losses - 118 F Hotwell B Limit............................................... 48

PNPS Variable Speed Pump Thermal Discharge ..................................................... 49

Summary ofVSP Operation - Hotwell B Limit c? 118 F ........................................

NPDES Water Discharge Permit Flows ................................................................... 54

Summary of Alternatives.......................................................................................... 56

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Response to United States Environmental Protection Agency CW A ~308 Letter

Summary of Report Conclusions

Pilgrim Nuclear Power Station (PNPS or the Station), owned by Entergy Nuclear Generation

Company (Entergy), consists of one Boiling Water Reactor unit in Plymouth, Massachusetts that

operates subject to and with the benefit of its existing National Pollutant Discharge Elimination

System (NPDES) permit (NPDES Permit MA0003557). This Report has been prepared by

Enercon Services (Enercon), a leading nuclear engineering firm, in response to certain requests

for information from the United States Environmental Protection Agency (EP A) under Section

308 of the Clean Water Act (CWA), 33 U.S.c. ~1318, with respect to cooling water intake

structures (CWIS) under CWA ~316(b), U.S.C. ~1326(b).

This Report relies upon an accompanying report prepared by N ormandeau Associates, Inc.

(Normandeau) that provides impingement and entrainment data used to characterize PNPS'

current impingement and entrainment mortality (I&E) reduction measures (as compared to

baseline), as well as to estimate potential changes in I&E for the potential alternative

technologies evaluated herein.

This Report documents Enercon s preliminary feasibility and engineering analysis of the

customary range of technologies potentially applicable at a large-scale nuclear facility (of the

configuration of PNPS) to reduce I&E. Nuclear safety and technological feasibility

determinations are made, as well as - where achievable - measures of the estimated

effectiveness and cost of the technology in question. The technological feasibility standard

applied by Enercon allows for consideration of only those technologies the installation and

operation of which would be permitted under PNPS' current operating license from the Nuclear

Regulatory Commission (NRC) and within the operating parameters of the nuclear power

industry.

Enercon evaluated several potentially available technologies with respect to their application to

reduce I&E and, based on this assessment, determined that certain technologies are not

technologically feasible at PNPS. First, conversion from the current once-through to closed-loop

cooling would dramatically, and inappropriately, increase Station design parameters above

several basic equipment limitations. Moreover, the Station s net thermal load would have to be

reduced to such an extent that nuclear safety concerns would render the Station completely

inoperable a minimum of 242 calendar days in a typical year (based on historical ambient

conditions), a configuration not acceptable in terms of current nuclear industry operating

standards. As a result, closed-loop conversion ofPNPS represents an infeasible circulating water

cooling technology. Likewise, in addition to the fact that the fragility (i. , a characteristic of

aquatic species that generally are not expected to surive, in any material numbers, impingement

on the vast majority of screening, barrier, barricade or comparable equipment or systems) of the

species historically impinged at PNPS does not support resort to the suite of potential traveling

water screen modifications and screening/barrier technologies potentially available at other

facilities, Enercon determined, as EP already has in its national rulemaking, that these

technologies are technologically infeasible due both to their unproven history as retrofitted

technologies at comparable nuclear facilities and to the nuclear safety concerns presented

specifically with respect to PNPS.

Aside from these exclusions, Enercon determined that only four technologies are either

technologically feasible , at PNPS or potentially so as a general matter with respect to the goal of

potential I&E reductions. The first technology, variable speed pumps (VSPs), is technologically

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Pilgrim Nuclear Power Station

Response to United States Environmental Protection Agency CW A ~308 Letter

feasible at PNPS, provided substantially increased thermal discharge limits are employed. The

remaining three technologies, an acoustic fish deterrent system, an offshore intake and assisted

recirculation, are generally technologically feasible on a theoretical basis for facilities like PNPS

but require further evaluation to determine their site-specific technological feasibility at PNPS

itself.

While an acoustic fish deterrent system is in use at a sister Entergy facility, Enercon cannot

assume without further study that such a system would be effective for the species impinged at

PNPS, as this is a conclusion that Normandeau has yet to assess and determine. Moreover, the

technological feasibility of such a fish deterrent system at PNPS would be highly dependent on

the ability to ensonify the CWIS with the appropriate hardware tolerant of the harsh

environmental conditions present at PNPS. As such, additional engineering studies are necessary

to determine the engineering feasibility of such a system.

An offshore intake, likewise, requires an engineering evaluation of the design and cost of a

viable location, and therefore must follow Normandeau s assessment and identification of the

potential locations, if any, for such a technology to reduce impingement and entrainment

mortality at PNPS.

Lastly, assisted recirculation -- a configuration whereby a portion of the water from the Station

discharge canal would be routed to a cooling tower, cooled, and returned to the CWIS, is

untested at any nuclear facility, making a detailed cost estimate impossible at this time absent a

rigorous design effort not able to be performed in the timeframe contemplated by this response

and unless EP A determines, despite the operational impacts of such a system, that further

consideration is warranted.

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Pilgrim Nuclear Power Station

Response to United States Environmental Protection Agency CW A ~308 Letter

Background, Introduction, and Scope

1.1 Background and Introduction

Pilgrim Nuclear Power Station (PNPS) is seeking a renewal of its existing National Pollutant

Discharge Elimination System (NPDES) permit (NPDES Permit No. MA0003557). This Report

has been prepared to provide PNPS' response to an information request letter from the United

States Environmental Protection Agency (EPA) under Section 308 of the Clean Water Act

(CWA), 33 U. C. ~1318, and to confirm the Station s current compliance with CWA ~316(b),

33 U. C. ~1326(b) (i. , ~308 Letter). In the ~308 Letter, EPA requested certain technology and

fisheries information from Entergy.

1.2 Scope

The following information is contained in this Report:

A detailed description of PNPS' existing cooling water intake structure (CWIS) and other

cooling systems.

A description of the processes employed at PNPS with regard to operation of the nuclear

steam supply system, condenser, CWIS, and effuent treatment.

An evaluation of PNPS' current CWIS technologies and operational measures with respect to

the EP A uniform baseline configuration.

An engineering evaluation of conversion of the PNPS cooling system from the current oncethrough to closed-cycle cooling.

An evaluation of the customary suite of impingement and entrainment mortality (I&E) *

reduction technologies (e. traveling water screen modifications screening/barrier

technologies, and an alternative intake location).

. An evaluation of potential flow reduction options (e. , variable speed pumps , assisted

recirculation, and the use of grey water).

This Report relies upon an accompanying report prepared by Normandeau Associates, Inc.

(Normandeau) that provides impingement and entrainment data used to characterize PNPS'

current I&E reduction measures, as well as to estimate potential changes in I&E for the potential

alternative technologies evaluated herein.

. I&E mortality or I&E means impingement mortality and entrainment mortality, as adjusted to reflect site-specific

or otherwise relevant impingement and entrainment survival infonnation detennined to be reasonably representative

by a qualified fish biologist or ecologist.
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PNPS and Cooling System Description

PNPS Overview

The primary activity of PNPS is the generation of electric power. PNPS is located in Plymouth

Massachusetts on the northwest shore of Cape Cod Bay.

PNPS began commercial operation in 1972. The PNPS Boiling Water Reactor (BWR) produces

steam for direct use in the steam turbine, and currently generates at a rated capacity of 711 MWe

(gross) with a nominal capacity of 685 MWe (net). PNPS was designed, constructed, and is

operated to withdraw seawater from Cape Cod Bay via a once-through CWIS. The PNPS CWIS

has a design intake flowt of 467.28 milion gallons per day (mgd).

The current expected operating mode for PNPS over the next ten years is at a capacity utilization

rate well in excess of 15% (the threshold for the applicability of certain requirements of EP A'

Phase II Rule promulgated under CWA ~316(b)), consistent with PNPS' role as a " base load"

supplier (in part, through long-term power purchase agreements) to New England electricity

customers, under the oversight and direction of among other regulators, the New England

Independent System Operator (ISO-New England).

Source Water Body

Description

As described in the PNPS Final Safety Analysis Report (FSAR), the Station is located on the

northwest shore of Cape Cod Bay, a circular embayment of the Atlantic Ocean off the coast of

eastern Massachusetts. The floor of the bay slopes gently to the north where maximum depths of

180 to 190 ft are found along a line between Plymouth Bay and Race Point, the northern tip of

Cape Cod (Ref. 10. , FSAR Section 2. 5.2. 1). The surface area of the Bay is approximately 430

and the volume is approximately 1.6x10 fe. About half the surface area of the bay has

depths greater than 100 ft and the volume-mean depth is also about 100 ft. Except for the

southeast comer of the bay, where Billingsgate Shoal is found, the depths generally increase

rapidly from shore (Ref. 10. , FSAR Section 2.4. 1.1J.

As described previously by ENSR (Ref. 10.4), historical water temperature measurements of

Cape Cod Bay taken together with more recent intake water temperatures recorded at PNPS from

1999-2005 , indicate that the mean annual temperature is approximately 50 F in the vicinity of

t Design Intake Flow or Licensed Design Flow means the condenser cooling water design flow values: (1)

calculated by qualified engineers employing the installed pmnp capacity curves at a typical discharge head (given as

27.5 ft in the PNPS Final Safety Analysis Report (FSAR)) for the condenser cooling water; and (2) reflecting the

addition of service water pumps serving an equipment cooling fuction, both as reflected in and consistent with the

FSAR. Licensed Design Flow equates to the value assigned, during the cooling water intake structue design, to the

expected total volume of water likely to be withdrawn from a source waterbody, consistent with 40 CFR 

125.93.

With respect to PNPS, the Licensed Design Flow is 467.28 milion gallons per day (mgd), or 324 500 gallons per

minute (gpm), including condenser cooling water flows of 447. 84 mgd, or 311 000 gpm, and service water flows of

19.44 mgd, or 13 500 gpm.

t The approximate nature of this area is evident when consulting other sources, such as Emberton (Ref. 10.20),

which describes a surface area of 1300 km (501 mi
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PNPS. Generally temperatures peak in the late summer and early fall with typical maximum

annual temperatures in the range of 68-7 5 F. Mixing between the surface and bottom water in

the fall transfers some heat to deeper layers, causing bottom water to show an annual peak

temperature in late summer/early fall. The water typically becomes isothermal in late

November, and surface water temperatures typically reach their annual low in January-February

(30- F). Bottom salinities are uniform throughout the year (31-32 ppt), while surface and near

shore salinities show seasonal variation due to spring runoff (Ref. 10.4, citing Galya et al. 1997).

An aerial view ofPNPS is shown in Figure 1.

J '

... ;( , , :

Figure 1 Aerial View of PNPS

Hydraulic Zone of Influence

As requested by EP A, the hydraulic zone of influence (HZOI) - which delineates the portion of

the embayment that is potentially affected by the intake flow - at PNPS was considered.

A 1977 study of the HZOI performed by the Massachusetts Institute of Technology Ralph M.

Parsons Laboratory for Water Resources and Hydrodynamics compared the tidal flow pattern

with and without the influence of the intake flow. Within the study, it was determined that

because "the relationship between plant flows and tidal velocities was similar in both situations

the assumption of negligible modification on tidal flow by the plant intake was indeed justified"

(Ref 10. 131).

Because influence of the intake flow is negligible, further delineation of the HZOI is not

necessary .

PNPS Tidal Influence

EP A requested a calculation of the total design intake flow over one tidal cycle of ebb and flow

as a percentage of the volume of the water column within the area centered about the CWIS
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opening, with a diameter defined by the distance of one tidal excursion at mean low water level.

Under 40 CFR ~ 125. , the tidal excursion is defined as "the horizontal distance along the

estuary or tidal river that a particle moves during one tidal cycle of ebb and flow." As a result

such a calculation is only possible where the volume of the water column can be defined with

reference to tidal estuaries or tidal rivers. As PNPS is a coastal facility that draws directly from

Cape Cod Bay, tidal excursion in the vicinity of PNPS cannot be calculated, and the applicable

water column subject to influence by the facility cannot be defined. In any event, PNPS' design

intake flow has virtally no influence on any applicable water column defined with reference to

tidal cycles in Cape Cod Bay.

Cooling Water Intake Structure Description

As detailed below, the CWIS is located along the shoreline9 and consists of several different

components. It begins with an opening created by two large protective breakwaters of a

constrcted embayment which reduce the effects of severe wave action. Seawater is drawn

through the constructed embayment and along a dredged intake channel (Ref. 10. , FSAR

Section 2.4.4. 1). Seawater flowing through the intake channel turns approximately 90 degrees at

the proximal end of the embayment. To restrain the seasonal ingress of horseshoe crabs, four

barriers consisting primarily of 16-inch tall I-beams are inserted into the four stop log guides at

that point ** . As shown in Attachment 5, Figure 5. , after entering the CWIS the seawater must

pass through trash racks before reaching the traveling water screens with their screenwash

pumps. The CWIS ends at the Salt Service Water (SSW)tt pumps, the Circulating Water (CW)H

(also known as the Seawater) pumps, the Fire Protection System pumps , and chlorination

equipment.

A major portion, approximately 96%, of the seawater that passes the traveling water screens is

directed to the CW pumps, which deliver water to the main condenser. A small portion

approximately 4%, of the seawater flows through the sluice gates and is used by the SSW pumps.

Additional flow is supplied, as demanded, to the Fire Protection System pumps; however, this

flow is infrequent and not continuous.

g Note that PNPS does not have a typical shoreline intake as discussed further throughout this section.

.. These horseshoe crab barriers have proven to be an effective obstacle that prevents the crabs, which are unable to

swim, from walking into the intake structue and becoming impinged on the traveling screens.

tt Salt Service Water or Service Water means the water withdrawn from Cape Cod Bay through the CWIS for

safety-related equipment, including facility shut-down systems, via as many as five (5) service water pumps , as

reflected on the PNPS NPDES Pennit Attachment B (Water Flow Diagram). Service Water is included in the

calculation of Licensed Design Flow.

H Condenser Cooling Water or Circulating Water means the water withdrawn from Cape Cod Bay through the

CWIS for the circulating water system, which absorbs heat from PNPS' main condenser and its supported systems

which in turn serve as a heat sink for turbine exhaust steam, tubine bypass steam, and other generating equipment

flow, as reflected on the PNPS NPDES Pennit Attachment B (Water Flow Diagram). Condenser Cooling Water is

included in the calculation of Licensed Design Flow.

gg 

Nonnal water supply for the Fire Protection System pumps is supplied by the Town of Plymouth.
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Physical Description, Location, and Depth of CWIS

The CWIS is located on Cape Cod Bay at coordinates N41 056' 46" and W70 34' 42" . The CWIS

begins with two large breakwaters (also referred to as jetties) that are designed of rubble mound

construction and are protected by heavy capstone. The breakwater on the northwest is

approximately 1400 ft long, and the breakwater on the southeast is approximately 700 ft long.

The top elevation of both breakwaters is at + 11.2 ft mean sea level (MSL) (+ 16 ft mean low

water (MLW)) (Ref. 10. , FSAR Section 2.4.4. 1). The breakwaters provide a first line of defense

from excessive wave action, overtopping due to wave runup, and storm flooding of the site. The

average velocity of flow at the embayment opening is 0.05 feet per second (fps) at mid-tide level

with both CW pumps operating (Ref. 10.4). The breakwater structures represent a difference

from the EP A uniform baseline configuration as defined in Section 4.

The CWIS then transitions to a screenwell that takes in seawater at its northern wall through four

bays, each 14 ft wide and 12 ft high topped by a skimmer wall. These openings to the bays are

fully submerged at mean low water level. The lowest portion of the CWIS is located at an

approximate elevation of 24 ft below MSL. The front of the screenwell includes a skimmer wall

the bottom of which is located at 12 ft below MSL, designed to restrict floating materials at or

just below the surface from approaching the traveling screens (Ref. 10.4). Because the skimmer

wall was designed and constructed to preclude surface withdrawal, it represents a difference

from the EP A uniform baseline configuration as defined in Section 4.

The screenwell of the CWIS is a reinforced concrete substructure, and a superstructure of steel

framing enclosed with precast panels, divided into four bays, one for each traveling screen

assembly. The four CW bays have steel struts on the walls to allow dewatering of the bays (Ref.

10. , FSAR Section 12.2.2.8). The SSW pump compartments are located between the two CW

pumps and are constructed of solid concrete. Refer to Figure 5.7 in Attachment 5 for a schematic

of the screenwell.

Two independent screening systems exist at PNPS. Trash racks (also known as bar racks) are

installed as a primary barricade to retain pieces of debris larger than 3 inches (Ref. 10. , FSAR

Section 11.6.3). Large debris that accumulates in front of the trash racks is manually removed by

plant personnel (divers). Four traveling water screens, two for each CW pump bay, follow the

trash racks. The traveling water screens, discussed in more detail below, are used to remove any

material larger than by y, inch. A dual (high and low pressure) screenwash system, consisting

of two pumps, duplex basket strainers, and associated piping and valves, is used to spray material

off the rotating screens into the fish return sluiceway. The supply to the screenwash pumps

comes from the SSW system, and screenwash water is dechlorinated prior to entering the

screenwash pumps because the SSW system is continuously chlorinated. The low pressure

screenwash system and fish return sluiceway were added as operational and structural controls

for the purpose of reducing impingement mortality. Therefore, they also represent a difference

from the EPA uniform baseline configuration as defined in Section 4.

Traveling Water Screens

PNPS has four Rex Chainbelt through-flow traveling water screens, two for each CW pump,

consisting of a continuous series of wire mesh panels bolted to frames and attached to two

matched strands of roller chains. They are each approximately 10 ft wide, and are installed in a

channel with the screening surface oriented perpendicular to the water flow. Each of the screens
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Response to United States Environmental Protection Agency CW A ~308 Letter

includes 53 basket segments (or panels). The chains operate in a vertical path overhead, carring

the panels down into the water, around the foot sprockets, back up through the water, and over

the head sprockets. All the traveling screens use the same stainless steel oblong-shaped mesh

with v"- inch wide by inch tall spacing and are framed in a fiberglass support structure. With

both CW pumps running, the design flow is 81 125 gpm per screen. Using the equation below

(Ref. 10. 7), the design through-screen velocity can be calculated as follows:

Through-Screen Velocity = Q/(BW*L W*POA *K)

where BW is the screen width in feet, L W is the water depth in feet, Q is the flowrate in gpm

POA is the "percent open area" of the screen basket, K is a conversion factor equal to 396, and

the through-screen velocity is calculated in fps (Ref. 10. 7). The POA of the traveling water

screens with v"-inch by inch openings is approximately 68% and the screen basket width

(BW) is 10ft. The water depth (L W) is 19.2 ft and is based on the water depth at ML W. Based

on these inputs, the through-screen velocity at ML W is calculated to be 1.57 fps.

The traveling water screens, which are used to remove aquatic life and/or debris from intake

water, are operated routinely, preemptively, and in response to an alarm - which occurs when

there is a pressure (or level) differential between the upstream and downstream sides of the

screen assembly. PNPS has six scheduled screenwashes per week to monitor fish impingement at

three different times of day: morning, afternoon, and evening. When the seawater temperatures

fall below 30 , the screens are operated continuously to prevent freezing. The screens normally

operate at 5 feet per minute (fpm), but can run at high speed (20 fpm) during heavy debrisloading conditions.

Under normal operation, seawater passes first through the ascending, and then the descending,

screen baskets. The ascending basket is located on the upstream portion of the screen, and

collects fish and/or debris as it passes up through the water. The aquatic life and/or debris are

retained on the upstream face of the wire mesh panels as well as on the horizontal surface of the

basket frame and the lifting lip that forms the lower, or trailing, edge of the mesh frame. The

basket continues to rotate and descends into the water on the downstream side. Aquatic life

and/or debris not washed off the screen basket may be washed off in the flow of water. This is

considered ' carrover' and wil travel into the CW pump bays (and possibly into the SSW pump

bays).

The traveling water screens represent a difference from the EP A uniform baseline configuration

as defined in Section 4.

Figure 2 shows a schematic of the traveling water screen operation.
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Figure 2

Screenwash System

Each traveling water screen uses dual (low and high pressure) spray washing to clean the debris

and/or aquatic life that has been impinged on the screens. Initially, a low pressure jet of water is

used to wash living organisms from the screen and lifting shelves. Then, a high pressure spray is

used to remove debris.

The low pressure screenwash sprays operate at a pressure of 15-20 psi, while the high pressure

screenwash sprays operate at 100- 120 psi. Each of the two screenwash pumps deliver 1000 gpm

where approximately 100 gpm is routed to the low pressure sprays, and 900 gpm to the high

pressure sprays. During normal operations, the spray-wash discharge is routed to the embayment

through the sluiceway on the east side of the CWIS (i. , the fish return sluiceway), which

empties into the embayment approximately 300 ft east of the screens. During severe weather

events (i. , ocean storms characterized by wind-induced wave runup), the spray-wash discharge

is sent to the discharge canal through the concrete sluiceway on the west side of the CWIS (i.

the debris sluiceway) because the increased capacity is needed to handle the debris load caused

by such storm events.

Sodium thiosulfate is added to the spray wash water to ensure that impinged organisms are not

washed with chlorinated water.

Traveling Water Screen Operation

The screenwash system represents a difference from the EP A uniform baseline configuration as

defined in Section 4.
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1.3 Skimmer Wall

The skimmer wall serves to block floating aquatic life and/or debris, and is effective to a depth

approximately equal to the depth of the wall itself. In addition to these benefits, the wall also has

10 inch diameter openings that act as fish escape ports. Fish escape ports are located in the

skimmer wall as well as in each of the four curtain walls, located at the screenwells about 6 ft

beyond the screens. This represents a difference from the EP A uniform baseline configuration as

defined in Section 4. 1.4 Fish Return Sluiceway

As described above, aquatic life and/or debris in wash water from the traveling screens are

discharged into one of two sluiceways. During normal weather conditions, the discharge 

routed through a sluiceway (i. , the fish return sluiceway) that empties into the embayment

approximately 300 ft to the east of the screens sufficiently far from the screens to allow

movement within and outside of the embayment. Throughout the length of the fish return

sluiceway it has several turns that vary from to 27 , and has an estimated slope of 0. 035

1/28) for most of its length (Ref. 10.8). Due to site limitations, shortly before emptying into the

intake embayment, the slope of the fish return sluiceway increases rapidly. The sluiceway was

fabricated from 18 inch corrgated metal pipe forms, which were used as molds to form the 9

inch deep semi-circular trough. The corrgations provide the resistance to flow in order to

maintain a design water depth of 6 inches and a design water velocity less than 8 fps in the

sluiceway. Also, the sluiceway is coated with water-based epoxy resin emulsions that are used to

keep fouling from forming in the sluiceway and provide a smooth surface. The top of the

sluiceway is covered with wire screens or heavy duty 3-inch grating covers in areas where

personnel and vehicles may travel.

As an operational measure, when the weather is severe or there is heavy loading, the screenwash

effuent is directed into the discharge canal via the concrete sluiceway on the west side of the

embayment (i. , the debris sluiceway). This sluiceway is much shorter than the eastern

sluiceway, and therefore does not go through many turns. Using this sluiceway during heavy

loading prevents the fish return system from clogging and prevents recirculation of debris.

The fish return sluiceway represents a difference from the EP A uniform baseline configuration

as defined in Section 4.

CWIS Flow Description

Pump Description

As stated previously, the CWIS houses two sets of cooling water *** pumps which supply all the

once-through cooling water for both the CW and SSW systems. No other seawater is withdrawn

from Cape Cod Bay by PNPS.

The CW system is used for condenser cooling and is supported by two (2) vertical, mixed flow

wet pit type CW pumps, each with an intake flow of 155 500 gpm at a discharge head of 27.5 ft.

The SSW system contains five (5) safety-related pumps with a combined intake flow of 13 500

... Cooling Water means the water withdrawn from Cape Cod Bay through the CWIS, including, with respect to

PNPS, Condenser Cooling Water and Salt Service Water, consistent with 40 CFR S 125.93.
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gpm. Therefore, the maximum continuous combined flow (the licensed design flow, as defined

previously) through the traveling screens is rated at 324 500 gpm (723 cfs or 467 MGD). This

licensed design flow is consistent with EP A' s definition of design intake flow in 40 CFR

~ 125.93.

Due to its status as a baseload facility, and consistent with operational practices in the nuclear

industry, PNPS pump (and CWIS) operation is continuous, except for planned refueling outages

and unplanned reactor shutdowns.
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Flow Reductions

The actual amount of flow entering the CWIS may be reduced when any of the cooling water

pumps are shut off, although a reduction in reactor power to 50% load or less is required to shut

off a CW pump. During a refueling outage at PNPS, the CW pumps are shutdown sequentially at

the beginning of the outage and are restarted before the end. At least one SSW pump is kept on at

all times, even during outages, in order to maintain essential cooling of nuclear safety-related

systems tH

Because refueling outages (and unplanned outages) are an operational measure to reduce flow

they represent a difference from the EP A uniform baseline configuration as defined in Section 4.

ttt Nuclear Safety means conditions, actions or considerations within the customary or exclusive jurisdiction of the

Nuclear Regulatory Commission (NRC) associated with the design, construction, operation and shut down of NRClicensed nuclear electric steam generating facilities, including without limitation any and all conditions associated

with the modified or altered use of equipment, or changes to facility operations, requiring assessment of a station

NRC licensing basis or operating procedures.

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Flow Reliabilty

Intake cooling water at PNPS: (1) promotes the effcient generation of electricity, and (2) ensures

an uninterrpted supply of cooling water for nuclear safety-related systems. Although the

majority of seawater entering the CWIS is pumped through the main condenser via the CW

system, the smaller portion of intake cooling water that also passes through the traveling water

screens flows into SSW pump bays. The SSW system provides the ultimate heat sink for nuclear

safety-related systems, such as Reactor Building Closed Cooling Water and Residual Heat

Removal.

Due to the consequences that have resulted from either a reduction or a temporary interrption of

intake cooling water flow, NRC and the Institute of Nuclear Power Operations (INPO), the

organization that sets performance objectives, criteria, and guidelines industry-wide for nuclear

power plant operations to promote operational and safety excellence, have addressed, through

regulation and mandatory guidance

, 

Intake Cooling Water Blockage." The nuclear industry,

and PNPS in particular, have experienced events in which traveling water screens have failed to

allow an adequate supply of cooling water, resulting in forced plant shut downs and activation of

emergency response systems. Viewed broadly, these requirements proscribe screen systems that

may compromise the ultimate heat sink or otherwise impair water-based nuclear safety-related

systems.

Moreover, these requirements are in a state of flux. In 2007, INPO issued a "Significant

Operating Experience Report" (SOER) mandating that nuclear plants evaluate and address all

possible factors that could lead to Intake Cooling Water Blockage. While PNPS' response to this

requirement has not been finalized yet, INPO' s SOER is expected to cause existing operation

and maintenance practices at PNPS to be re-evaluated and may lead to design changes affecting

CWIS components.

Biocide Treatment

Sodium Hypochlorite Injection

The SSW system is protected from marine growth (micro-fouling, a biofim deposition on heat

exchanger tubes) and mussels (macro-fouling) by continuous injection of sodium hypochlorite.

The CW system is protected from micro-fouling by injecting hypochlorite for 1 hour per day

(normally) per loop. This time limit reflects NPDES Permit requirements. Thermal backwashes

are used to control macro-fouling in the CW System and other areas of the CWIS (excluding the

SSW pump bays).

Measurement of the concentration of total residual chlorine (TRC) in the CW System is required

by the NPDES Permit. Monitoring instrumentation consists of a small sample pump at the

discharge canal footbridge and an amperometric titrator to determine the TRC concentration in

samples drawn from the effuent stream. At least one CW pump must be in operation for

dilution. Total residual chlorine in the SSW System is measured by daily grab samples and

analysis.

A solution of sodium hypochlorite is applied to each CW pump bay alternately to achieve a

maximum effuent concentration of 0. 1 ppm (mg/L) for approximately I hr/day in order 

control slime growth and fouling organisms within pump bays and the CW system. Two

chemical metering pumps supply hypochlorite just downstream of the trash racks 5 to 7 days per

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week during spring, summer, and fall. The frequency is usually reduced in the winter to reflect

the decrease in biofouling potential. The Station s Chemistry staff (Chemistry) samples the

discharge canal during periods of CW System chlorination to verify residual chlorine levels are

detectable but below 0. 1 ppm TRC (Ref. 10.22) to ensure compliance with the NPDES Permit

(Ref. 10. 16).

The SSW chlorination system has three installed metering pumps, two running simultaneously

while the third pump acts as a spare to either of the running pumps. Hypochlorite is injected

inside each of the SSW pump bays.

The SSW System is chlorinated 24 hours per day, 7 days per week. The SSW loops are sampled

by Chemistr just downstream of each Reactor Building Closed Cooling Water heat exchanger.

These samples are analyzed for residual chlorine and the maximum must average': 1. 0 ppm

TRC (Ref. 10.22) to ensure compliance with the limits specified in the NPDES Permit.

Screenwash Dechlorination System

There are two screenwash pumps that are supplied from the SSW headers, which supply high

pressure and low pressure spray headers to keep the traveling screens clean. Debris and any fish

that are sprayed off of the screens are returned to the intake canal via the fish return sluiceway.

Because the screenwash water originates from the SSW system, which has been chlorinated, the

SSW system water must be treated (dechlorinated) to remove the residual chlorine prior to being

entering the intake canal to comply with the limits specified in the NPDES Permit.

There are two dechlorination pumps, one for each screenwash pump. metered sodium

thiosulfate solution is injected into the screenwash pump suction. The system includes 55 gallon

drums of sodium thiosulfate, two positive-displacement dechlorination pumps, a flow indicator

for each pump, and an event recorder to record operation of the traveling screens, screenwash

pumps, and dechlorination pumps. The pumps are equipped with a variable stroke and frequency

to allow regulation of injection rate.

2.4 Discharge System

The discharge from the condenser and from the SSW System is returned via the discharge canal

to Cape Cod Bay (Ref. 10. , FSAR Section 11.6.3). The discharge structure and canal are to the

northwest of the CWIS. The discharge canal is approximately 870 ft long and is extended over

the beach to mean low water (MLW) by rock-fill jetties. The jetties are of rubble mound

construction and are protected by heavy capstone. The jetties have a nominal elevation of + 

ML W (+ 11.2 MSL) sloping down to a height of 4 ft at ML W. The elevation of the bed of the

discharge canal is 0 ft ML W. The discharge canal jetties also serve to promote rapid mixing in

Cape Cod Bay for heat dissipation and to protect the CWIS and discharge structures from wave

action (Ref. 10. , FSAR Section 2.4.4).

At the CW licensed design flow of 311 000 gpm through the condenser and with the turbinegenerator at full power, the temperature rise through the condenser is typically 29 F. The

maximum allowed temperature rise from the CWIS to the end of the discharge canal is limited to

F in the NPDES Permit, Section A.2. a (Ref. 10. 16). The permitted maximum discharge canal

temperature may not exceed 102 F at the point of discharge to Cape Cod Bay. RTD temperature

sensors are located at the intake and discharge canals to provide input signals to the station

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computer and an alarm display in the main control room for monitoring compliance with the

NPDES Permit limits for the CW system effuent temperature (Ref. 10. , FSAR Section 11.6. 3 J.

Cooling Water Process Flow Diagram

Refer to Figure 1 of Attachment 5, which shows the flow of cooling water through PNPS.

Recent and Planned Plant Modifications

Modifications since January 2001

No significant modifications that changed the design or operation of the CW System, CWIS, or

SSW System have been made since January 2001; rather, only maintenance and preventative

maintenance activities have occurred.

Currently, there are no substantial design changes or modifications to the CWIS planned.

Age of Cooling System Equipment

Table 1 describes the equipment and components used in PNPS' cooling system , over time.

Table 1 History of Key CWIS Components at PNPS

Equipment Originally

Installed Date and Description of Component Replacement

Bar (Trash) Racks 1970 1998 , Replaced in-kind lower and mid sections of racks due to

cOlTosion. Top section was in excellent condition.

Traveling Screens 1970

1992, Replaced X- l08C&D screens wi 2 speed motors head shaft

roller bearings and suspension system, stainless steel baskets with

oblong (Yz x Y4 inch) mesh and stainless steel chains.

1994, Replaced X- 108A&B screens wi 2 speed motors head shaft

roller bearings and suspension system, stainless steel baskets with

oblong (Yz x Y4 inch) mesh and stainless steel chains.

1994- 1996, Installed lifting lips on basket frames.

1998 , Changed from stainless steel basket frames to fiberglass and

Nitronic 60 basket chain rollers/pins/bushings.

2005 , Replaced X-I 08C&D complete assemblies.

2007, Replaced X-I 08A&B complete assemblies.

Spray Wash

(SCREENW ASH) 1970

1994, Replaced P-213A & P-2l3B pumps (and basket strainers) with

100 hp motors and increased impeller size to boost flow from 750 gpm

up to 1000 gpm (reflected in 1994 NPDES permit modification).

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Table 1 History of Key CWIS Components at 

Equipment Originally Date and Description of Component Replacement

Installed

1986, Replaced P-l 05A & B impellers, shroud and pump inner casing

from C-Iron to 316 SS.

Circ Water Pump 2001 , Rebuilt P-l 05B pull out pump section in-kind.

105A & P-I05B

1970 2005 , Rebuilt P- 105A pull out pump section in-kind and replaced four

outer pump columns due to graphitization.

105B is scheduled to have the same columns replaced in 2009

(RFO# 17).

Originally a Screenwash supplied eductor system with no electric

Circ Water driven pumps provided CW Hypo.

Hypochlorite Injection 1970

Pump 1990, Installed two P-I13A and P-I13B positive displacement pumps

and piping.

1986, Installed 2 metering pumps and piping.

SSW Hypochlorite 1986 1990, Installed 3 metering pumps. Injection Pump

2001 , Replaced SSW Hypo piping.

Screenwash

Installed 2 metering pumps at the inlet of Screenwash pumps to de1986 chlorinate SSW supply water.

Dechlorination Pumps

2006, Replaced metering pumps.

Projected Retirement Plans

Currently, and except as provided under applicable NRC law regarding license life, there are no

plans to retire PNPS, which is a baseload source of supply, providing critically needed reliable

affordable power to ISO-New England customers.

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Description of Plant Processes

Nuclear Steam Supply System Operation

At its most basic, a BWR is designed to produce electrical energy through conversion, via a

turbine driven generator, of a portion of thermal energy contained m the steam supplied from the

reactor; to condense the turbine exhaust steam into water; and to return the water to the reactor as

heated feedwater with a major portion of the gaseous, dissolved, and particulate impurities

removed (Ref. 10. , FSAR Section 11. 1 J. The major components of the power generation system

are: turbine generator, main condenser, condensate pumps, condensate demineralizers, reactor

feed pumps, feedwater heaters, and condensate storage system. The heat rejected to the main

condenser (the waste heat inherent in any thermodynamic cycle) is removed by the CW System.

The saturated steam produced by the reactor is passed through the high pressure turbine where

the steam is expanded and then exhausted through the moisture separators. Moisture is removed

in the moisture separators and the steam is then passed through the low pressure turbines where

the steam is again expanded. From the low pressure turbines, the steam is exhausted into the

condenser where the steam is condensed and de-aerated, and then returned to the cycle as

condensate.

A simplified schematic of a BWR plant is shown in Figure 3 (Ref. 10. 19).

ContaiwnellttDty,,-ell

Turbine Building

SteamDlyer

Moisture

Sepamtor

Electrical

Generator

-- Reactor Core condenser

Jet Pump

TofFrom

Ocean

Recirculation

Pmup

Pmup

Containment Suppression Chamber

Figure 3 Simplified Schematic of BWR Plant Operation

Condenser Operation

The pUfJose of the main condenser is to serve as a heat sink (i. , a mechanism for heat removal)

for turbme exhaust steam, turbine bypass steam, and other flow (Ref. 10. , Sections 11. 3.

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through 11.3.3). As such, cooling provided by the condenser to condense steam is necessary to

provide feedwater for the reactor, moderating the neutrons to maintain the nuclear reaction and

thereby generating steam to drive the turbine.

The PNPS main condenser is a twin shell, horizontal titanium tube, seawater cooled unit and is

located in the Turbine Building below the main tubine s low-pressure sections. The location of

the condenser below the main turbine is indicative of its function, whereby the cooling water of

the CW system condenses the steam exhausted from the turbine, which is then retued to the

reactor as feedwater.

Seawater is the heat sink for the main condenser and its supported systems. Each condenser shell

has divided water boxes, which permits isolation of the CW on one-half shell while the other half

remains in operation. The arrangement of CW piping allows backwashing of the condenser by

section to remove possible debris accumulated on the inlet tube sheets.

The main condenser is rated at the following design parameters (Ref. 10. 3):

a. Steam condensed - 4. 85x10 1bm/hr

Heat removed - 957.6 BTU-lbm/hr

Absolute pressure - 1.49 inches Hg Vac

Inlet water temperatue - 48

Sea water flow - 311 000 gpm

Surface area - 400 000 fe

CWIS Operation

Refer to Section 2.3 for a detailed description of the CWIS.

3.4 Effluent Treatment Operations

No chiling or cooling of heated once-through cooling water is performed at PNPS. Discharged

cooling water is monitored for compliance with NPDES Permit limits as described in Section

2.3.3.

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Evaluation of Existing CWIS Technologies and Operational Measures

EPA prescribes a uniform baseline configuration (40 CFR ~125. 93) designed to ensure

consistent decision-making among different facilities nationwide as follows:

Calculation baseline means an estimate of impingement mortality and entrainment

that would occur at your site assuming that: the cooling water system has been

designed as a once-through system; the opening of the cooling water intake

structure is located at, and the face of the standard 318-inch mesh traveling screen

is oriented parallel to, the shoreline near the surface of the source waterbody; and

the baseline practices, procedures, and structural configuration are those that your

facility would maintain in the absence of any structural or operational controls

including flow or velocity reductions, implemented in whole or in part for the

purposes of reducing impingement mortality and entrainment...

This section discusses the following existing CWIS technologies and operational measures at

PNPS that differ from the EP A baseline, as described in Section 2.3:

Breakwaters

Skimmer wall

Fish escape ports

Traveling screens

Low pressure screenwash

Fish return system

Outage schedule/fow reduction

Based on input provided by Normandeau, the low pressure screenwash, fish return system, and

flow reductions produce quantifiable reductions from baseline in I&E. While data is not

available to estimate the impacts on I&E for the other components, Normandeau has provided

assessments of the qualitative features of each component.

The differences in I&E at PNPS, while treated in this Report as percentage reductions, are

characterized by Normandeau in terms of equivalent adult (EA) fish to ensure comparable raw

data is properly understood and evaluated. Table 2, based on information provided by

Normandeau (see Attachment 6), which shows baseline fish losses and monthly fractions during

recent representative years, demonstrates that entrainment accounts for 99.3% percent of the

losses. The four months with the most EA entrainment are March through June, accounting for

more than 80% of the annual entrainment. The four months with the most EA impingement are

April, August, September, and November, which account for more than 75% of the annual

impingement, but only 0.5% of total annual abundance (of combined baseline EA entrainment

and impingement).

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Table 2 PNPS Baseline Monthly EA Entrainment and Impingement

Monthly EA Monthly EA Monthly EA Monthly EA

Month Entrainment Entrainment Impingement Impingement

Losses Fraction Losses Fraction

January 236 324 1.7%

February 161 822 372

March 465 612 17.4% 1529

April 385 340 14.4% 4012 21.4%

May 601 582 22.4% 393 2.1%

June 793 354 29.

July 141 583 0.2%

August 189 3494 18.

September 691 2625 14.

October 1888 495

November 2410 4452 23.

December 2540 0.1% 1012 5.4%

Annual 681 247 100. 788 100.

1.1

Evaluation of Existing CWIS

Traveling Water Screen Low Pressure Screenwash and Fish Return

System

As provided by Normandeau (see Attachment 6), incremental EA impingement survival due to

the sluiceway and the low pressure wash systems are shown in Table 3. The most incremental

EA impingement survival due to the sluiceway occurs in the months of May and July, with an

annual EA impingement survival of 9.7%. The annual incremental EA impingement survival due

to the low pressure wash system is 5.7%, where the months with the most EA impingement

survival are January, May, and November. Thus, the cumulative EA impingement survival is

15.4%, based on the additive nature of the survival data supplied by Normandeau in Attachment

Ht Based on adjustments to design intake flow based on actual flow. Refer to Attachment 6.

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Table 3 PNPS Baseline EA Impingement Survival

- Fish Return Sluiceway and Low Pressure Wash

System

Month Fish Return Low Pressure

Sluiceway Wash System

January 1.%

February

March

April 3.4%

May 28.

June

July 37.

August 12. 1.%

September 1.4% 2.4%

October 12.

November

December 1.0%

Annual

1.2 Breakwaters

The breakwaters creating PNPS' intake embayment provide a relatively protected area from the

often dynamic environment of southwest Cape Cod Bay, particularly during periods of easterly

winds. Per Normandeau (Ref. 10.23), the prevailing counterclockwise net flow in Cape Cod Bay

is also deflected by the breakwaters, and fish that might otherwise be disoriented in the Bay

turbulent waters, or carried along in the strong current, are less likely to be impinged due to the

presence of the breakwater.

Skimmer Wall

The skimmer wall along the leading edge of the CWIS extends approximately 12 ft below the

water s surface at mean sea level. Per Normandeau (Ref. 10.23), fish traveling individually or in

schools near the surface encounter and are deflected by the wall and are therefore less

susceptible to impingement on the traveling screens. 1.4 Fish Escape Ports

The PNPS intake includes a number of 10-inch fish escape ports, located in the skimmer wall of

the CWIS. Per Normandeau (Ref. 10.23), fish that pass under the skimmer wall can escape

encounters with the traveling screens by passing through the openings. 1.5 Outage Schedule/Flow Reduction

PNPS has an annual flow reduction of 5.4% from the baseline flow (licensed design flow) of

324 500 gpm, and the greatest reductions in flow occur in April and May due to the timing of

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refueling outages. The other reductions from baseline flow correspond to periods of lesser flows

through the SSW system due to reduced cooling demands and to unplanned outages. The

monthly baseline flows (in milions of gallons per month) and the actual monthly flows are

shown in Table 4 along with the corresponding flow reduction percentages

!?!?!?

Table 4 PNPS Flow Reduction from Baseline

Month Baseline Flow Actual Flow Flow

(MG/month) (MG/month) Reduction

!?!?!?

January 486 14,104

February 084 667

March 486 970

April 018 298 26.

May 486 524 13.

June 018 682 2.4%

July 14,486 262 1.5%

August 486 300 1.%

September 018 809 1.5%

October 486 942

November 018 692

December 14,486 144 2.4%

Annual 170 557 161 394 5.4%

Percent Reductions from Baseline for Existing CWIS

As discussed previously, not all of the existing CWIS technologies have data available to

quantify I&E. The EA entrainment reduction from baseline is calculated based on information

provided by Normandeau, solely from the reduction in flows due to the refueling outages and

reduced cooling demands. Similarly, the EA impingement reduction and EA impingement

mortality reductions are calculated based on flow reduction attributable to refueling outages

(with respect to impingement reductions), as well as on the reductions due to the sluiceway and

the low pressure spray wash (with respect to impingement mortality reductions). While the

remaining technologies do not have quantifiable reductions in entrainment and/or impingement

This Report assumes that a direct linear (1: 1) relationship between flow reductions and the number of fish

entrained and impinged exists; however, the reductions in impingement and entrainment due to flow reduction

reported by Nonnandeau in Attachment 6 are slightly more conservative than the actual flow reduction from

baseline and, therefore, wil be used throughout this Section. Percentage reductions in entrainment and impingement

due to flow reduction differ slightly due to the conversion of sampled life stages per unit volume to total monthly

life stages, and the consolidation of species and life stages into a single entrainment or impingement number per

month.

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mortality, each technology does have an associated reduction in entrainment and/or impingement

mortality as discussed in qualitative terms above.

Entrainment Reduction from Baseline for Existing CWIS

Reduction percentages from baseline for EA entrainment are comprised of actual flows divided

by baseline flows, multiplied by the monthly entrainment distribution, as shown in Attachment 6.

Because entrainment is not uniform throughout the year, flow-weighted annual entrainment

reductions were calculated based on the results of the actual pattern of intake flows in each

month throughout the year.

The EA entrainment reduction, shown in Table 5, is the product of the monthly flow reductions

given in Attachment 6, Table 6.4 and the monthly EA entrainment abundance from Table 2.

The months with most significant portion of EA entrainment reductions are April and May,

while the EA entrainment reduction from September through January is minimal, due to the fact

that each of these months experience less than I % of the annual entrainment.

Existing operations reflect a cumulative quantified reduction of EA entrainment from baseline of

approximately 8. , based on a six-year averaging of monthly EA entrainment reductions.

Table 5 PNPS Baseline EA Entrainment Reduction by Month

Month Monthly EA Flow EA Entrainment

Entrainment Reduction Reduction

January

February 3.2% 0.2%

March 17.4%

April 14.4% 26.

May 22.4% 13.

June 29. 2.4%

July 1.%

August 1.2%

September 1.5%

October

November 2.3%

December

100.

Annual

(Total) (Average) (Total)

Impingement Mortality Reductions from Baseline for Existing CWIS

Unlike entrainment, where reductions from baseline are computed based solely on the product of

the flow reduction (i.e. the difference between baseline or licensed design flow and actual flow)

and the monthly entrainment distribution, impingement mortality reductions from baseline

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include the effects of the fish return sluiceway and low pressure traveling screenwash as shown

in Attachment 6, Table 6. 13.

The incremental EA impingement mortality reductions from Table 3 (fish return sluiceway and

low pressure wash system) and Attachment 6, Table 6. 13 (flow reduction) are combined (based

on the additive nature of the survival data supplied by Normandeau in Attachment 6) to create a

cumulative EA impingement reduction. The EA impingement reduction is the product of this

cumulative monthly EA impingement reduction (in Table 6) and the monthly EA impingement

from Table 2.

The months with the most significant portion of cumulative monthly EA impingement reduction

are April through July, while the months with the most significant portion of the monthly EA

impingement abundance are August through November. The average cumulative monthly EA

impingement reduction is 20.8%. For each month, the cumulative EA impingement reduction is

applied to the monthly EA impingement abundance to determine the amount of the annual EA

impingement reduction that occurs within that month. For example, in April there is a

cumulative EA impingement reduction of 38.4%. This reduction in EA impingement is

subsequently applied to the April EA impingement abundance of 21.4% to yield an annual EA

impingement reduction of 8.2% within the month of April.

The months with the greatest EA impingement reductions are April, August, and November

while the EA impingement reduction in June and July is at a minimum due to the fact that each

of these months experience less than 1 % of the annual impingement.

Existing operations reflect a cumulative quantified reduction from baseline of approximately

18. , based on a six-year averaging of monthly EA impingement reductions.

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Table 6 PNPS Baseline EA Impingement Reduction by Month

Monthly EA Impingement Reduction

Month Monthly EA Impingement Impingement Flow Fish Return Low Pressure

Reduction Sluiceway Wash System Cumulative Reduction

January 1.% 12.1 %

February

March

April 21.4% 26. 3.4% 38.4%

May 13. 28. 9.1% 51.% 1.%

June 0.3% 2.4% 19.4%

July 0.2% 1.0% 37. 44.4%

August 18. 1.% 12. 1.% 14.

September 14. 1.5% 1.4% 2.4%

October 12. 6.2% 22.

November 23. 13.

December 5.4% 2.4% 1.0% 11.0%

100. 20. 18.

Annual

(Total) (Average) (Average) (Average) (Average) (Total)

Evaluation Methodology for Alternatives

The assessments detailed in the following sections review potential alternate technologies and

operational measures for reducing I&E. The evaluation criteria focus on engineering

considerations, though noting biological factors where significant. The engineering factors

include technological feasibility and reliability, proven installation at comparable nuclear

facilities, and modifications conflicting with the Station s licensing basis or implicating nuclear

safety concerns. After considering engineering factors, the evaluation addresses the estimated

ability of the technology to demonstrably reduce I&E (as determined by Normandeau based on

PNPS site-specific data, relevant literature, or both).

Where an alternate technology or operational measure satisfies the engineering and biological

criteria, capital and operational costs are then estimated under a conceptual model appropriate at

this stage of the analysis, but likely understated in terms of site-specific costs, unkown at this

time, that may substantial increase costs. Thus, for instance, the preliminary estimates provided

in this Report do not account for several complicating factors, including radiological

contamination and the limitations on development necessitated by the zoning and agricultural

(forestry) restrictions in place at Entergy s property.

Potential modifications to the CWIS for a nuclear facility such as PNPS, which has a combined

CW and SSW intake, are complicated by the fact that SSW flow is related to nuclear safety, and

must be available at all times (i. , for normal operations, shutdown, and postulated accident

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conditions). Per the PNPS Salt Service Water / Chlorination Reference Text (Ref. 10.2), the

safety design bases of the SSW system are as follows:

I. SSW is designed so no single system component failure can prevent it from providing a

heat sink for RBCCW

 .

2. SSW continuously supplies adequate cooling water to the RBCCW heat exchangers

under transient and accident conditions.

Therefore, any potential technology that introduces new failure modes into the SSW system, or

could interfere with maintaining SSW supply, would implicate nuclear safety concerns and be

therefore judged as technologically infeasible.

In summary, technologically feasible means a baseline determination that a particular technology

likely can be implemented in general at comparable steam-electric generating stations and, as

qualified, in a site-specific manner at PNPS to reduce entrainment or impingement without

implicating nuclear safety considerations. Site-specific technological feasibility may 

qualified, and therefore, not technologically feasible if the technology is unprecedented (i. , not

demonstrated at any comparable facility).

*... Reactor building closed cooling water.

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Closed-Loop Cooling

PNPS is water-dependent - meaning both that it requires a specific quantity and quality

(measured by temperature) of water, here consistently cold seawater. Closed-cycle cooling

reduces water use with respect to the temperature of that water. Thus, any analysis of closedcycle cooling requires consideration of how these changes in water temperature will affect plant

systems, operation, and output. The retrofitting of nuclear facilities of comparable size, age and

configuration to PNPS to closed-loop cooling is untried. Thus, this assessment is subject to the

caveats that it is performed without any actual confirmatory data, and reflects the inherent

uncertainties with novel applications of a technology intrusive to fundamental station operations.

Additionally, PNPS, as with all nuclear power plants, is designed to operate on a continuous and

consistent basis, and is not configured to allow frequent dramatic short-term power reductions.

Significant power reductions at PNPS require initiating and concluding procedures varying in

length but often extending over numerous hours. In other words, dramatic reductions in power

while short in duration, may have longer-term operational ramifications, effectively extending

the power reduction period.

With these caveats, this section provides a preliminary engineering evaluation on the potential

impact of converting PNPS from a once-through cooling water system into a closed-loop cooling

water system. For this evaluation, the basic plant operational parameters are first defined and

then applied to calculate the effects, including the expected power generation loss, associated

with PNPS operating under a retrofitted closed-loop cooling water design.

More specifically, Enercon obtained, reviewed, and analyzed local (meteorological) data for use

as an input to the state-of-the-art site performance evaluation of power system effciency

(PEPSE) model. The PEPSE model is a power plant performance modeling software that uses

among other things, cooling water intake temperature and flow rates to calculate plant

operational parameters and the resulting net power generated. The PEPSE model provides the

expected plant operational parameters and power reductions necessary to theoretically operate

PNPS without exceeding equipment limitations resulting in nuclear safety considerations.

Likewise, the PEPSE model is used to analytically define the hypothetical circumstances in

which PNPS is incapable of mitigating nuclear safety concerns through operational measures

(i. , where the Station is rendered inoperable).

Meteorological Data

The performance of any closed-loop cooling water system is primarily driven by the ambient

weather conditions at the site and the inlet water temperature values. Cooling towers define their

performance via an approach to wet bulb temperature. The wet bulb temperature, a

meteorological measurement which incorporates both moisture content and temperature of the

ambient air, is necessary for closed-loop cooling analysis, as cooling towers utilize an

evaporative process to remove heat from the continuously recirculated cooling water. The

approach to wet bulb describes the number of degrees above the ambient wet bulb temperature

by which the cooling tower can be expected to reduce the cooling water temperature, whereby a

lower approach equates to lower cooling water temperature exiting the cooling tower. The

approach to wet bulb is a value that is based on the size and effciency of the cooling tower, and

essentially represents the cooling ability of the equipment. Any data set used to predict the

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performance of PNPS relies heavily on the presence of either historical wet bulb temperature

measurements or a combination of values that can be used to calculate the wet bulb temperature

(e. , dry bulb temperature and relative humidity, dry bulb temperature and dew point, etc. 1.1 Meteorological Data Sources

Wet bulb temperature data has been recorded for over a decade at a first order National Weather

Service (i. , staffed by National Weather Service employees) observatory located less than 10

miles from PNPS at the Plymouth Municipal Airport. This site-representative data was retrieved

from the National Weather Service (NWS) via the National Climatic Data Center (Ref. 10. 5). 1.2 Meteorological Data Analysis

The NWS records meteorological data both hourly and during special weather conditions. Once

the data is retrieved from the NWS, a thorough review is conducted to normalize the hourly data

ensuring that a uniform hourly data set with no erroneous data is used as the basis for analysis.

As even minor errors present in the meteorological data would propagate throughout the

analysis, particular focus is paid to the review and acceptance of the meteorological data.

Furthermore, there is almost always some degree of data loss attributed with meteorological

monitoring. This data loss may be due to a number of causes (equipment failure

biological/human interference, etc.); however, a general guideline for meteorological data

acceptance is that the data maintain an average 90% data recovery rate (Ref. 10. 14). The average

recovery rate for the ten year period analyzed (1997-2006) was 99. 1 % as shown in Attachment 3

Table 3. 1; therefore, the data gathered from the Plymouth Municipal Airport greatly exceeds the

threshold for validity. 1.3 Inlet Water Data Analysis

PNPS supplied ten years (1997-2006) of measured CW inlet temperatures identical to that

provided for NPDES permit compliance. This data was normalized into hourly segments to

create a uniform hourly data set with no erroneous data used as the basis for analysis. The

average recovery rate for the ten year period analyzed was 97. , representing an extremely

robust data set. The monthly recovery rate per year is shown in Attachment 3 , Table 3.2.

PNPS Administrative/Continuous Operation Limits

PNPS equipment operation is governed by a set of administrative limits tttt used to ensure

adequate reliability and safety. Specifically, BWRs are subject to nuclear safety constraints on

operations of various Station equipment, including pump net positive suction head requirements

overall plant control characteristics, core thermal power limits, and core thermal-hydraulic

stability. PNPS equipment operation must be thoroughly analyzed in regard to the modifications

required to convert PNPS from once-through to closed-loop cooling, in order to ensure these

administrative limits are not exceeded. If it is expected that these administrative limits may be

exceeded, PNPS is required to operate atypically under various levels of restriction that decrease

the net power generated by PNPS and ultimately implicate nuclear safety concerns. Because

tttt Administrative limits are PNPS-proceduralized limits used to prevent encroachment ofNRC licensed limitations

(e. , technical specification limitations, FSAR limitations, etc.), which require a documented Limited Condition of

Operation when exceeded.

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these administrative limits implicate nuclear-safety concerns, a slightly more conservative

continuous operation limit is used to ensure that these administrative limits are not exceeded.

This approach is consistent with longstanding plant and industry operational practices, and meets

industry expectations for established safety and nuclear margins.

PNPS Cooling Water Equipment

Changes to the PNPS cooling water equipment that would result in performance gains are

restricted by the size and configuration of the equipment within the turbine building, particularly

the condenser and the surrounding components. PNPS' condenser was sized to reflect the

intended use of a stable and cold seawater source. The net result is that conversion to closedcycle cooling would require modification (through a size increase) of the condenser. 

condenser modification of this sort is unprecedented (i. , implementation of a condenser

redesign of this magnitude has never occurred at an operational nuclear power plant). Due to the

magnitude of this redesign and the lack of any history of a nuclear plant undertaking such a

modification, it is concluded that the current cooling water equipment configuration could not be

modified in such a way that enhances its cooling performance.

As shown in Figure 4, the orientation of the PNPS main condenser is such that the entire turbine

building is built on top of, and around, the main condenser. The net result of the main condenser

location is that any increase to the size of the condenser would require a complete disassembly of

the turbine building, along with the accompanying modifications/additions to the turbine

building following condenser modification. Because the turbine building contains the second half

of the reactor power conversion system (the reactor itself being the first half), the scale of a

turbine building modification/addition of this kind is also unprecedented (i. , implementation of

a complete turbine building redesign has never occurred at an operational nuclear power plant).

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.....

Figure 4 Turbine Building

Main Condenser Vacuum

The objective of the main condenser is to provide a heat sink for the tubine exhaust steam

turbine bypass steam, and other related flows. The main condenser is of the single pass, divided

water box, de-aerating type. It consists of two shells, one for each low pressure turbine cylinder

and is a seawater cooled unit located directly beneath the low pressure cylinders of the main

turbine as shown in Figure 4 (Ref. 10. 1) The administrative limit given in the PNPS Main

Condenser Vacuum System Procedure (Ref. 10.6) requires that the main condenser vacuum be

below 4 in-Hg absolute.

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Hotwell Temperature

The main condenser hotwells provide the input flow for the condensate demineralizer system.

Variations in hotwell temperature have a direct impact to the performance and longevity of the

condensate demineralizer system. The hotwells have an average administrative limit of 120

As hotwell temperatures approach the 120 F administrative limit, the condensate demineralizer

resins are subject to reduced service life and impeded performance. According to the Main

Condenser Vacuum System Procedure (Ref. 10. 6), if these administrative limits cannot be

maintained the power must be reduced in accordance with the Station Power Procedure (Ref.

10. 17).

To provide an operational margin against the administrative limit, a continuous operation limit of

118 F is evaluated in the PEPSE analysis to ensure instantaneous ambient variations are not

capable of causing the administrative limit to be exceeded. This continuous operation limit is

consistent with sound nuclear engineering practice and industr standards.

2.4 Power/Flow Operating Map

To satisfy nuclear safety constraints, BWRs must operate under numerous restrictions, including

pump net positive suction head requirements, overall plant control characteristics, core thermal

power limits, and core thermal-hydraulic stability considerations. The power/flow operating map

for PNPS is included as Attachment 5, Figure 5.2. Constraints imposed by equipment, alarms

reactor scrams initiated by protective instrumentation, and operator actions based upon written

operating procedures maintain PNPS within the bolded boundary lines shown on this map for an

allowable region of operation, bounded by a monitored region that prevents high power/low flow

conditions that increase the likelihood of a thermal-hydraulic instability resulting in power

oscilations (transients), which are generally proscribed because they require the use of control

rods as a remedial measure. Using control rods to regulate reactor power implicates nuclear

safety concerns due to the increased potential for transients and could not be employed under

normal or acceptable operational conditions. Thus, monitored operations are not considered

allowable on a routine basis, and therefore may be employed only on a limited basis, such as

weekly control rod swaps or more infrequent condenser backwashing, both typical of industrywide operations.

A reactor power level of greater than approximately 80% is necessary to operate within the

allowable region of operation, i. , outside the monitored region, thereby preventing the use of

control rods to regulate reactor power.

Closed-Loop Operational Parameters

As stated in Section 5.2. , conversion of a nuclear power plant designed for once-through

cooling to closed-loop cooling has never occurred. Nonetheless, the theoretical effect on PNPS

converting from once-through to closed-loop cooling is evaluated herein and requires that certain

closed-loop operational parameters be defined. Due to their lower effciency, evaporative ponds

spray ponds, cooling canals, and dry cooling towers are not capable of providing suffcient

cooling to support the condenser temperature required by the PNPS turbine design. Therefore

none of these are considered feasible technologies. As such, evaporative cooling towers are the

most appropriate potential closed-loop cooling mechanism for consideration at PNPS.

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SPX Cooling Technologies, a leading cooling tower design vendor, was consulted on similar

northeastern United States power plant installations and subsequently supplied baseline

performance of evaporative cooling towers considered here for use at PNPS. Utilizing this range

of performance and taking into account the site conditions and operational restrictions present at

PNPS, a tower with a 12 F approach was considered appropriate for evaluation purposes.

5.4 Closed-Loop Operational Parasitic Losses

All forced draft cooling towers require input electricity to perform their cooling operation. This

resulting loss of electricity, referred to as a parasitic loss, is extremely taxing to the net electrical

output of a plant, and increases as a function of the cooling provided. Cooling tower parasitic

losses include those losses directly attributed to the cooling tower fans and any required

additional CW pump horsepower necessary to overcome the increase in static head added by the

cooling tower.

Taking PNPS' site-specific characteristics into account, complete closed-loop conversion of

PNPS utilizing a 12 F approach to wet bulb hybrid cooling tower would include a continuous 20

MWe aggregate parasitic 10ss

PEPSE Model

The performance evaluation of power system effciency (PEPSE) model is a state-of-the-art

power plant performance modeling software used by the nuclear power industry to estimate plant

operational parameters and net power generated using system inputs such as CW inlet

temperature. The most recent PNPS PEPSE model was reviewed, updated, and run to produce

the results discussed herein. A diagram of the PNPS PEPSE model has been included in

Attachment 5 , Figure 5.

PEPSE Analysis - Baseline Closed-Loop Operation

As described above, the current PNPS PEPSE model was updated and run over a bounding range

of CW inlet temperatures (32 F to 94 , in 2 F increments) to calculate the baseline closed-loop

operation of PNPS (i. , the theoretical performance of PNPS if it were to be converted to closedloop operation). At each CW inlet temperature, the net power generated (MWe), hotwell

temperatures (OF)/condenser backpressures (in-Hg) for each main condenser shell, and the

condenser output temperatures (OF) were recorded. These outputs were in turn used to correlate

quadratic fit equations for each output as a function of continuously variable CW inlet

temperatures (see Attachment 3, Figures 3.2 and 3.3). These correlations ultimately allow for the

limiting PNPS operational conditions to be calculated for all feasible CW inlet temperatures.

PEPSE Analysis - Reduced Power Operation

The PEPSE model allows for the calculation of system outputs and operational conditions as a

direct function of various system inputs; however, these system outputs are fixed and may not be

used as an input variable to calculate operating conditions of the system (i. , the PEPSE model

is limited to the unidirectional calculation of operational conditions via system input). To

UU This estimate utilizes components and operating procedures typically selected for 12 F ilpproach to wet bulb

cooling towers.

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evaluate performance in the full range of operating conditions, the net thermal input (MWt) for

the system was iterated over a series of CW inlet temperatures to define quadratic correlations

used to calculate the system output and operational conditions (i. , net power generated (MWe),

hotwell temperatures (OF)/condenser backpressures (in-Hg) for each main condenser shell, and

the condenser output temperatures (OF)). Overall, the CW inlet temperature for each hour is input

into a set of quadratic correlations, which in turn allows for the calculation of the limiting

operational parameters.

Baseline Closed-Loop Operation Parameters

Using the NWS meteorological data to calculate the hourly closed-loop cooling tower

performance, and following the baseline PEPSE analysis methodology described above, the

bounding baseline closed-loop limits are described below.

Condenser Vacuum

As stated in Section 5.2, the limiting parameters for a theoretical closed-loop conversion of

PNPS are a condenser vacuum of 4 in-Hg and a continuous operational hotwell temperature of

118 F. At baseline conditions, the condenser vacuum and hotwell temperature are highly

correlated (see Attachment 3 , Figure 3. 1). As a result, comparisons between the two can be made

on general basis to define the limiting parameter. According to Attachment 3 , a condenser

vacuum of 4 in-Hg is comparable to a hotwell temperature of approximately 125 F. As such, the

hotwell temperature of 118 F is determined to be more bounding than condenser vacuum, and

therefore used as the continuous operation limit in this analysis.

Hotwell Temperature

Hotwell A and B temperatures were evaluated at the continuous operation limit of 118 F. Per

this PEPSE model analysis, the baseline closed-loop operation of hotwell B bounds that of

hotwell A. Therefore, throughout the following analysis, the more limiting hotwell B

temperature has been selected as operative.

Reduced Power Operational Parameters

Similar to the baseline closed-loop operational parameters, the reduced power operational

parameters use the NWS meteorological data, along with the hourly inlet water temperature.

These parameters are used to calculate the theoretical power generation lost in order to maintain

plant operational parameters below their continuous operation limits. Per the methodology

described in Section 5. , the CW input temperature is used to create a quadratic correlation

allowing for the calculation of the limiting system operational parameters. The power reduction

is calculated hourly by deducting the theoretical power produced at the closed-loop continuous

operation limit from the operating power level generated under the current once-through

configuation.

PNPS, as with all nuclear power plants, is not configured in such a way that enables dramatic

short-term power reductions. Significant power reduction at PNPS requires initiating and

concluding procedures varying in length but often extending over beyond the stated hourly

power loss event. This manner of operation is disruptive of station operations and may extend

power losses. As a result, calendar days (i. , days experiencing at least one hour of power loss)

are more representative of the power loss duration likely to be experienced at PNPS.

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Hotwell Temperature

As previously discussed, the hotwell B temperatue bounds the hotwell A temperature and the

condenser pressure. Limited to the bounding hotwell B operation, Table 7 was created, and

contains the number of hours and calendar days with a net power generation loss experienced by

PNPS.

Table 7 Net Power Generation Loss

Hotwell B :5 118

Power Loss Required

Hours Calendar Days

Power;: 20 MWe 8083 356

Power;: 40 MWe 8054 356

Power;: 60 MWe 7604 346

Power;: 80 MWe 7040 330

Power;: 100 MWe 6411 308

Power;: 120 MWe 5816 285

Power;: 140 MWe 5240 262

Power ;:160 MWe 4716 240

As shown in Table 7, an ambient power reduction greater than 20 MWe (i. , those times with an

active thermal reduction 9m) occurs an average of 8083 hours at the continuous operation limit

of 118 F. The limiting power reduction necessary to maintain hotwell B' s temperature less than

118 F is 441 MWe. Likewise, an active thermal reduction occurs an average of 356 calendar

days per year to maintain the continuous operation limit of 118

For determining the time in which active power reduction is required to limit hotwell B below

the continuous operation temperature, Tables 3.3 through 3.6 of Attachment 3 were created to

list the frequency of consecutive occurrences requiring active power reduction. Per Attachment

, continuous active power reduction is required for an average of 304 days per year to limit the

hotwell B temperature to 118

Power/Flow Operating Map

As discussed in Section 5.2.4 a BWR must operate with certain restrictions, whereby the

constraints imposed by equipment are used to create a power/fow map for the operation of

PNPS, included as Attachment 5, Figure 5.2. The PNPS power/fow operation map mirrors the

PEPSE model results such that a decrease in core flow rate yields a proportional decrease in net

thermal load, which in turn yields a decrease in net power generated. As such, the power/fow

operating map validates the PEPSE results obtained and provides baseline operational values for

the core flow rate pump.

m Active power reduction is defined as the time at which power losses are beyond the summation of parasitic

losses and those directly associated with higher inlet temperatures.

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In addition to analyzing the reduction in net power generation, analysis of the hours of operation

at less than 80% net thermal load (i. , the monitored region threshold) is conducted. To this end

hotwell B experiences an average of 4787 hours per year at 118 F operating at less than 80% net

thermal load. Additionally, hotwell B experiences an average of 242 calendar days limited at

118 F operating a minimum of one hour at less than 80% net thermal load. Exceeding the 80%

thermal limit would implicate nuclear safety concerns and ultimately result in a shutdown of the

plant. As a result, the calculated calendar days with active power reduction provide a

conservative estimate that includes the extensive time required to bring the Station to normal

operation after a shutdown.

Seasonal/Daylight Closed-Loop Power Reduction

As the operation of cooling towers is driven primarily by ambient environmental temperatures

seasonal and daylight conditions have a significant impact on PNPS closed-loop operation.

Attachment 3 , Section 2 defines the net power loss attributed to conversion to a closed-loop

cooling system on a monthly and hourly basis (i. , monthly figures/tables are provided listing

average closed-loop power loss for each I-hour period of the day).

On average, July and August experience the greatest power reduction, with an average monthly

power loss of approximately 291 MWe occurring at a hotwell B limit of 118 F. Examining July

and August further, the greatest hourly power reduction occurs between 9am and 4pm, with an

hourly power loss of approximately 309 MWe occurrng at a hotwelllimit of 118 F during this

time period.

Summary of Reduced Power Operational Impacts

The limiting operational parameter (hotwell B temperature) for PNPS baseline closed-loop

operation was analyzed using the PEPSE model and the results displayed in Table 7.

Conversely, to evaluate the effect exceeding these limits has on PNPS operation, the overall heat

load was varied to calculate the power reduction necessary to maintain parameters at or below

their operational limits. The power reductions necessary to limit hotwell B temperatures below

the primary bounding and power/fow map thermal limits are summarized in Table 8 below.

Table 8 Closed-Loop Limiting Operation Parameters

Hotwell B :: 118

Operational Limit 1997-2006 Average

Description Hours Calendar Days

Power Loss )0 100 MW e MIl 308

Heat Loss 0: 80% MWt 4787 242

As shown in Table 8, the overall effect of a closed-loop conversion on plant operation, examined

using the PNPS power/fow operating map, is a net thermal load reduction of such an extent that

nuclear safety concerns occur during a significant portion of the year. Taking into account the

extensive amount of time required to return the Station to operation after a plant shutdown, the

calculated calendar days of active power reduction are conservatively understated. To this

extent, operation of PNPS below a net thermal load of 80% is not feasible, and operation of

PNPS near the conditions above increases the likelihood of transients, implicating nuclear safety

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concerns. Based on this analysis, closed-loop conversion of PNPS represents an infeasible CW

cooling technology.

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Alternative Impingement/Entrainment Reduction Technologies

This section evaluates the following alternative technologies in three categories, with the primary

focus of the technology (reducing either impingement mortality or entrainment mortality)

indicated.

1) Modified traveling screens and fish handling and return systems

a. Upgraded fish return trough (impingement)

b. Coarse mesh Ristroph screens (impingement)

c. Fine mesh Ristroph screens (entrainment)

d. Dual-flow conversion traveling screens (impingement)

e. Multi-disc screens (impingement)

f. WIP screens (impingement)

g. Angled traveling screens and modular inclined screens (impingement)

2) Screening/barrier systems

a. Fish net barriers (impingement)

b. Wedgewire screens ( entrainment/impingement)

c. Aquatic micro fitration barriers (impingement)

d. Behavioral barriers (impingement)

3) Alternative intake location (impingement/entrainment)

Modified Traveling Screens and Fish Handling and Return Systems

According to Normandeau (Ref. 10.23), ten different species of fish account for approximately

98% of recent (i. , 2002 through 2007) impingement events at PNPS. Approximately 89% of

this impingement involves two species (Atlantic menhaden and silversides) that Normandeau has

advised do not, and are not expected to, survive screen impacts associated with impingement, no

matter the screening technology employed. Therefore, reductions in impingement mortality with

modified traveling screens are expected to be minimal at PNPS. Nonetheless, for completeness, a

suite of alternative screening technologies are evaluated below.

Moreover, as discussed below, the fish return trough is consistent with the current industry

standard. Therefore, consideration of additional fish return technology is not warranted.

1.1 Upgraded Fish Return Trough

During normal (i. , non-severe weather event) operations, the fish return sluiceway, which was

added in 1980 and designed to maximize survivability of the impinged fish (Ref. 10.8), is used.

As explained previously, the existing fish return sluiceway was designed to minimize the stress

to impinged fish and maximize their surivability through the sluiceway, and remains consistent

with standard industry specifications for such sluiceways, given site constraints at PNPS.

Therefore, no upgrades to the fish return sluiceway are warranted.

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Coarse Mesh Ristroph Screens

Modified Ristroph buckets can be and, in certain instances, have been retrofitted onto existing

traveling water screens, including at nuclear facilities, to work in conjunction with the debris

removal function of the existing traveling water screens.

With the addition of Ristroph screens, shown in Figure 5, the fish trough for the sluiceway would

need to be restructured. The Ristroph screen would unload the impinged fish to a location

opposite to where they are currently unloaded. This is because the current traveling screens

unload fish while they are ascending, but the Ristroph modified screens are unloaded while the

screens are descending. Therefore, a new trough would need to be constructed to collect the fish

and carr them down to the fish return sluiceway.

Lo, ; Pr swre spra,s

Fish FlelurnTrough

Captured

Fish/De bris

High

Pf' sS:lJre 

Spray, 

Debris Trough

Figure 5 Modified Ristroph Screen

Approximately 89% of the impinged aquatic organisms would not experience decreased

impingement mortality by adding Ristroph buckets. Thus, Ristroph buckets are not further

considered here.

1.3 Fine Mesh Ristroph Screens

At certain facilities, traveling water screens can be further modified to incorporate screen meshes

with openings as small as 0.5 mm to collect fish eggs and larvae and return them to the source

water body. As Normandeau indicates (Ref. 10.23), for many species and early life stages, mesh

sizes of 0. 5 to 1. 0 mm are required for effective screening. Such screening presents several

biological and engineering concerns.

Per input from Normandeau, the primary biological concern with fine mesh screens is that they

function by impinging early organism life stages that are entrained through coarse mesh screens.

Depending on species and life stage, mortality from impingement can exceed entrainment

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mortality. In order for fine mesh screens to provide a meaningful benefit in protecting fish

impingement survival of target species and life stages must be substantially greater than survival

through the CW system, circumstances not demonstrated here.

Generally and at PNPS in particular, to accommodate fine mesh screens while maintaining

existing head loss across the screen, the size of the intakes would need to be greatly expanded

because a much larger fine mesh screen would be required to provide the same total open area as

the coarse mesh screens. The primary engineering concern implicates nuclear safety. Although

EP A references the Brunswick Nuclear Plant as though fine mesh screens have been successfully

applied there (Ref. 10. , Chapter 4, Section 2.3.2), their application has been limited. As stated

in the Brunswick 2000 Environmental Monitoring Report (Ref. 10. 21), " (d)uring periods of high

vulnerability resulting from extreme lunar tides or increased sediment and debris loading, the

NPDES permit allows for removal of a portion of the fine-mesh screens to prevent plant scrams.

High vulnerability conditions existed for most of the year. Installation of non safety-related

components with the potential to increase reactor scrams (shutdowns) is contrary to current

operational standards in the nuclear industry.

For these reasons, fine mesh screens are not considered technologically feasible for

implementation at PNPS.

1.4 Dual-Flow Conversion Traveling Screens

At some facilities, including at nuclear facilities, existing through-flow traveling screen

installations can be retrofitted to use dual-flow traveling water screens (Ref. 10. 7), which

because of the increased area used to pass water through the screens, can reduce the throughscreen velocity. Conceptually, a dual-flow traveling water screen is mechanically similar to a

through-flow screen that has been rotated ninety degrees in the flow channel. The modification

consists of the installation of a special wall plate mounted perpendicular to the flow in place of

the existing screen. The dual-flow screen is then lowered into the well, with baskets parallel to

the flow, on the upstream side of the wall plate. An inlet opening in the wall plate allows

screened water to pass to the pumps. An alternative arrangement uses a specially constructed

screen mainframe that includes a wall plate made as an integral part of the screen frame with

extensions or "wings" that fit into existing embedded guides.

Approximately 89% of the curently impinged aquatic organisms at PNPS would not experience

decreased impingement mortality by replacing the existing through-flow screens with dual-flow

screens. Thus, dual flow screens are not further considered here.

It must be noted that the existing penetrations in the CWIS deck for the traveling screens are not

of adequate size to accommodate a reduction in velocity if retrofitted with dual-flow traveling

screens. As stated in Section 2. , the through-screen velocity with the existing through-flow

traveling screens is 1.57 fps, which would increase to 1.77 fps with dual flow screens of the same

mesh sizing (due a reduction in screening width from 10 ft to 4.75 ft). Alternatively, a reduced

velocity with dual flow screens would require a new CWIS or extensive modifications to the

existing CWIS; such an implementation would require an extended forced outage.

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Multi-Disc Screens

Multi-disc screens can, and in certain instances, have been retrofitted onto existing traveling

water screens at nuclear facilities. However, the use of such screens has been targeted from the

perspective of Station performance (debris removal) rather than as a fish protection measure.

Multi-disc screens, shown in Figure 6 (Ref. 10. 9), are oriented the same way as traditional

through-flow screens. Multi-disc screens are comprised of circulating sickle shaped mesh panels

that are connected to a frame via a revolving chain. The linked mesh panels are guided on each

side forming a unit together with the support. The forces applied by the flowing water to the

center of the mesh panels are transmitted via supporting beams into the supporting structure. In

the center, the mesh panels are supported by rollers. Raw water flows directly through the mesh

panels. The debris retained at the face of the ascending mesh panels is transported with debris

carriers to floor level. There, it is removed by means of a spray-water device. This reduces the

amount of carrover into the condenser intake stream.

Figure 6 Multi-Disc Screen

Approximately 89% of the currently impinged aquatic organisms at PNPS would not experience

decreased impingement mortality by adding multi-disc screens. Thus, this technology is not

further considered here.

1.6 WIP Screens

At some facilities, existing through-flow traveling screen installations can be retrofit to use WIP

screens; however, there have been no instances of such a retrofit at a United States nuclear

facility, and therefore the technology is unprecedented in the domestic nuclear industry.

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screen face that fish may avoid as they are directed to the escape bypass. Modular inclined

screens (MIS) are a variation of the angled screens whereby modules are provided which consist

of an entrance with trash racks, dewatering stop logs in slots, an inclined screen set at a 10-

degree angle to the flow, as well as a bypass to direct fish back to the source water body.

In order to install angled traveling screens or modular inclined screens at PNPS, the entire CWIS

would have to be replaced because all of the components of the intake are oriented perpendicular

to the shoreline. Moreover, the bypass system is an integral part of the intake. The installation of

modular inclined screens requires a nearly complete CWIS replacement because modular

inclined screens are only supplied as complete systems. In addition, an extended forced outage

would be required to modify/replace the CWIS and install the modular inclined screens.

Because of the unproven nature of this kind of CWIS change, retrofit of the PNPS CWIS to

accommodate the installation of angled traveling screens or modular inclined screens is

considered technologically infeasible.

Moreover, approximately 89% of the currently impinged aquatic organisms at PNPS would not

experience decreased impingement mortality by adding angled traveling screens or modular

inclined screens. Thus, these technologies are not further considered here.

Screening/Barrier Technologies

Fish Net Barriers

Fish net barriers are wide-mesh nets that are installed in front of CWISs. The water entering the

CWIS must first pass through the openings in the mesh. The size of the mesh openings limits the

size of the organisms that can pass through the net. According to Normandeau (Ref. 10.23), in

order to be successful, the nets must have a large surface area such that the velocity through the

net is very small (usually :s 0. 5 fps). Otherwise, organisms would become impinged on the

screen.

Barrier nets have not been used at nuclear facilities, due to nuclear safety concerns associated

with the deployment of such a net. Dunng a heavy ocean storm, the net may become loose

and clog the intake, cutting off the SSW supply required for safe shutdown of the plant.

Therefore, the deployment of a barrier net at PNPS is considered technologically infeasible

because it implicates nuclear safety concerns.

Cylindrical Wedgewire Screens

Cylindrical wedgewire screens are designed to reduce entrainment and impingement in two

ways. First, organisms susceptible to entrainment cannot pass through the small slot size in the

***** The installation of equipment either in the embayment or lodged to the protective breakwaters has proved

diffcult at PNPS. For example, during the summer of 2002, in response to an order from the NRC mandating

security enhancements to address concerns arising from September 11 , 200 I , PNPS installed barrier booms across

the entrance to the intake embayment and across the discharge canal. The intake boom was anchored in stone at

each end of the of the embayment jetties and was also anchored to the bottom of the embayment from buoys located

at 100-foot intervals on the boom. The discharge boom was anchored in stone at each end but was free floating in

the canal. A strong Northeaststorm that year destroyed both booms, which NRC did not require PNPS to attempt to

replace.

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Pilgrim Nuclear Power Station

Response to United States Environmental Protection Agency CW A 9308 Letter

screen. Screen mesh sizes range from 0.5 to 10 mm, with the most common slot sizes in the 1.0

to 2. 0 mm range. Wedgewire screens have two principal configurations: wide-slot screens with

larger screen mesh sizes that primarily seek to reduce impingement mortality, and narrow slotscreens with small screen mesh sizes that primarily seek to reduce entrainment mortality.

EP A has expressed significant reservations about the application of wedgewire screens at nuclear

facilities comparable to PNPS. As stated in Section 2.2.3 of EPA's TDD (Ref. 10. 12), " (fJinemesh wedgewire screens (0.5 - 1 mm) also have the potential for use to control both

impingement and entrainment. EP A is not aware of the installation of any fine-mesh wedgewire

screens at any power plants with high intake flows (:: 100 MGD). However, such screens have

been used at some power plants with lower intake flow requirements (25 to 50 MGD), which

would be comparable to a very large power plant with a closed-cycle cooling system. With the

exception of Logan, EP A has not identified any full-scale performance data for these systems.

They could be even more susceptible to clogging than wide-mesh wedgewire screens (especially

in marine environments). It is unclear whether clogging would simply necessitate more intensive

maintenance or preclude their day-to-day use at many sites.

In the current CWIS configuration, a nuclear safety concern is associated with the installation of

wedgewire screens. During severe ocean storms, the wedgewire screens may be dislodged

damaged, or clogged due to excessive debris. This would likely lead to the intake becoming

clogged, which would cut off the SSW supply, which is required for safe shutdown of the plant;

as EPA noted at page 4-13 of its TDD (Ref. 10. 12), there are no full-scale data regarding

wedgewire screens available for marine environments where biofouling and clogging are

significant concerns.

For all of these reasons, the installation of wedgewire screens at PNPS is considered

technologically infeasible. In any event, to address these concerns, a new CWIS or extensive

modifications to the existing CWIS would be required to isolate the SSW supply from the

wedgewire screens used for the CW system. An extended forced outage would be required to

implement these changes to the CWIS.

Aquatic Microfiltration Barriers

Aquatic micro fitration barrier systems (e. , Gunderbooms) are barriers that employ a filter

fabric designed to allow for passage of water into a CWIS, but to exclude aquatic organisms.

These systems are designed to be placed some distance from the CWIS within the source

waterbody and to act as a filter for the water that enters into the cooling water system. These

systems may be floating, flexible, or fixed. Because these systems generally have such a large

surface area, the velocities that are maintained at the face of the permeable curtain are very low.

Similar to a fish barrier net, a nuclear safety concern is associated with the deployment of aquatic

micro filtration barriers. During a severe ocean storm, the net may become loose and clog the

intake, cutting off the SSW supply required for safe shutdown of the plant. Therefore, aquatic

micro fitration barriers are not considered technologically feasible for use at PNPS ttttt

tttt For these nuclear safety-related reasons, the New York State Department of Environmental Conservation

(NYSDEC) has adopted the conclusion that aquatic micro fitration barriers and similar technologies are not feasible

at Indian Point Energy Center, a nuclear facility with a CWIS along the Hudson River in Buchanan, New York (Ref.

10.24, p. VII-43, as adopted by NYSDEC in Ref. 10.25).

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Pilgrim Nuclear Power Station

Response to United States Environmental Protection Agency CW A 9308 Letter

Behavioral Barriers

Behavioral barriers use a fish's natural reactions to stimuli to deflect it away from intakes. The

three main behavioral barrier systems are bubble barriers, artificial lighting arrays, and

underwater acoustic fish deterrence systems. There are at least two installed operating acoustic

fish deterrence systems: one at the D.C. Cook Nuclear Plant in Bridgman, Michigan (Lake

Michigan), and the other at the Entergy s J.A. FitzPatrick Nuclear Power Plant (JAFNPP) near

Oswego, New York (Lake Ontario).

JAFNPP operates a state-of-the-art Fish Deterrent System (FDS) deployed at the offshore CWIS

typically from the first week in April into October of each year. The sonic FDS consists of nine

projector housings symmetrically installed on top of the offshore velocity cap and employed

during the spring, summer, and fall months. The projectors are removed for the winter months

due to the potential damage from ice packs, then redeployed in the spring.

The FDS system emits a high frequency broadband sound (122 - 128 KHz) at a source level of

190 decibels. According to Normandeau (Ref. 10.23), alewife, and perhaps other clupeids, may

avoid this high frequency broadband sound, because Clupeiformes have swim bladders and inner

ear specializations that enable these fish to detect sounds (Ref. 10. 10), with the result that the

high frequency sound of the FDS triggers an avoidance mechanism in such species.

The site-specific feasibility of a FDS is highly dependent on the impinged species and their

contribution to historical impingement, as well as their response to sound, and the engineering

constraints associated with the harsh marine environment. Extensive further study is required to

ascertain the feasibility of this technology.

Alternative Intake Location

As discussed in Section 2. , the CWIS at PNPS draws water from Cape Cod Bay through an

embayment formed by two substantial breakwaters. EP A has asked PNPS to consider extending

its intake fuher offshore.

Offshore intakes typically draw in water via vertical inlets with velocity caps placed on top.

These intakes are located far from the screen house and slightly above the floor of the source

body of water. Velocity caps are covers that are placed over vertical inlets at offshore intakes;

they are used to reduce I&E by reducing fish, eggs, and larvae drawn into the intake system. As

shown in Figure 9, a velocity cap slows and converts vertical flow into horizontal flow at the

entrance of the intake (Ref. 10. 11).

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Pilgrim Nuclear Power Station

Response to United States Environmental Protection Agency CW A 9308 Letter

SEA

BED

(II

. .. . ...

' : ''' . . t . . VELOCITY

1'1" '1" 1'"

FLOW FLOW

'01 

:::. .. . 

Figure 9 Typical Velocity Cap Flow Direction

Velocity caps are sized to achieve a low intake velocity between 0.5 and 1. 5 fps, which may

reduce impingement (Ref. 10. , Chapter 4, Appendix A). In order to connect the velocity cap to

the screenwell of the existing CWIS, a large diameter intake tunnel would need to be constructed

underneath the floor of the bay. The design, location, and depth of such an offshore intake would

be dependent on technological limitations and the site-specific location selected with respect to

potential biological benefits.

Per Normandeau (Ref. 10.23), no site-specific fisheries data are available with which to assess

potential I&E at an offshore intake location. Detailed field studies of ichthyoplankton and local

fish distribution are required to establish whether an offshore location is preferable and what that

location would be. The engineering feasibility of an offshore intake cannot be evaluated without

first establishing this location.

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