Document ID: EPA-HQ-OW-2008-0667-0009
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2009-11-05T05:00Z

Site Visit Report

	Constellation Energy—Nine Mile Point Nuclear

	348 Lake Rd

Scriba, NY 13126

April 2, 2008

Background and Objectives

The Environmental Protection Agency (EPA) is in the process of
developing 316(b) cooling water intake structure requirements that
reflect the best technology available (BTA) for minimizing adverse
environmental impact for all existing power plants and manufacturing
facilities. As part of this process, EPA staff is visiting electric
generators and manufacturers to better understand the cooling water
intake structure (CWIS) technologies in use at facilities, including the
site-specific characteristics of each facility and how these affect the
selection and performance of CWIS technologies.  EPA is also visiting
facilities to better understand cooling water use and specific issues or
technologies that can affect 316(b) compliance.  Nine Mile Point Nuclear
Station (NMP) was selected for a site visit due to its use of an
offshore intake location (with a velocity cap) and its large intake
flows.

Facility Description

The Nine Mile Point nuclear facility is operated by Constellation
Energy, which is also the principal owner. The two unit boiling water
reactors (BWR) are located in Oswego, NY on a large industrially-zoned
site approximately 900 acres in total size on the southern shore of Lake
Ontario. The total developed area of the site dedicated to buildings,
roads and other improvements relate to facility operations is
approximately 200 acres; the remaining portion is undeveloped.
Undeveloped areas border the facility to the south and west, with the
James Fitzpatrick Nuclear Station adjacent to the east (see Attachment
A). 

Cooling water withdrawals from and discharges to Lake Ontario for Units
1 and 2 are permitted under SPDES Permit No. NY0001015, which has been
administratively extended pending adoption of a new permit.  The
facility discharges to the west of the intakes.  Discharges from Unit 1
are approximately 600 feet off-shore and discharges from Unit 2 are
approximately 1800 feet offshore.  

Electricity Generation and Transmission

NMP Unit 1, a BWR nuclear unit, came online in 1974 and has a rated
capacity of 609 MW. NMP Unit 2, also a BWR nuclear unit, came online in
1987 with a rated capacity of 1,148 MW. Both units are baseload
facilities providing electricity to the Niagara-Mohawk grid. As a
baseload facility, NMP’s capacity utilization rate is high with recent
years averaging more than 90 percent. 

Refueling outages occur every 18 to 24 months, typically in the spring,
and last approximately 20-30 days. Each unit is refueled every other
outage.  NMP Unit 2 was in the middle of a refueling outage during the
site visit. Because outages are routine, facility-wide maintenance
activities, including those related to the intake structure, are
scheduled to occur at the same time. 

Cooling Water Intake Structure

Each unit at NMP has a dedicated cooling water intake structure that
operates independently. 

The intake structure for Unit 1 is located approximately 850 ft offshore
in Lake Ontario.  The terminal end of the intake conduit is fitted with
a hexagonally-shaped concrete velocity cap, the top of which rises 6
feet off the lakebed and is approximately 14 feet below the lake
surface.  The velocity cap measures 32 feet in total diameter. Each of
the six sides has a water inlet slot measuring 5 feet high by 10 feet
wide. Galvanized steel bars spaced 10 inches apart prevent large objects
from entering the system. Intake velocity at the velocity cap is
approximately 2 feet per second (fps). 

Two circulating water pumps draw water through a 120-inch concrete
tunnel to the onshore pump house at a maximum velocity of 0.85 feet per
second. Trash racks remove larger debris from the instream flow. The
intake divides into three interconnected bays in the screen house, each
fitted with vertical stainless steel traveling screens with 3/8 inch
mesh panels. Screens are rotated periodically based on a pressure
differential between the upstream and downstream faces and washed with a
high-pressure spray. Any accumulated debris, including impinged fish,
are emptied to a collection basket and discharged to Lake Ontario with
the plant effluent through the main outfall. 

The maximum design flow rate is 418 million gallons per day (mgd). As a
baseload facility, NMP Unit 1 withdraws water at its maximum capacity
during normal operations and does not moderate flows based on climate or
operating conditions. The facility does moderate intake water
temperatures during winter months by recirculating a portion of the
heated discharge water to the intake to maintain the desired condenser
water temperature. This reduces the total volume of water withdrawn from
Lake Ontario by as much as 10 percent depending on water temperatures. 

The Unit 2 cooling system is a closed-cycle, recirculating wet cooling
tower with makeup water drawn from Lake Ontario through two offshore
intake structures extending approximately 1,000 feet from the shoreline.
The Unit 2 wet cooling tower is a single cell natural draft model with a
total height of 541 feet. 

The terminal ends of each offshore intake are fitted with a velocity cap
approximately 28 in total diameter. Each of the six sides has a water
inlet slot measuring 3 feet high by 7.5 feet wide. Galvanized steel bars
spaced 10 inches apart prevent large objects from entering the system.
Intake velocity at the velocity cap is approximately 0.5 feet per second
(fps). 

Each intake structure is independently connected to the onshore
screenwell by 4.5-foot diameter concrete intake tunnel. At the onshore
screenwell, each intake tunnel connects to a separate vertical shaft.
After passing through the two vertical shafts, the water enters the
onshore screenwell building. Water from both vertical shafts merges into
a common intake forebay, which is divided at its downstream end into two
4-foot wide screenbays. An angled, flush-mounted traveling screen and
two trash racks, one upstream and one downstream from the traveling
screen, are located in each screenbay. 

Unit 2 is equipped with a fish diversion system. Fish entering the
screenbays pass through the trash racks and are guided by the angled,
flush-mounted traveling screens into 6-inch bypass slots at the
downstream end of the screen. At this point the fish are transported
through a funnel-shaped transition to two pipes that merge into a single
pipe leading to a jet pump. The bypass flow and fish are then
transported by the jet pump through this pipe to a vertical riser that
discharges into the lake parallel to the lake bottom.

Six intake pumps draw water through the Unit 2 intakes at a maximum rate
of 53,600 gpm, or 77 mgd. This includes service water flows in addition
to makeup water for the cooling tower. A separate pump system circulates
water between the condensers and the cooling tower at a maximum rate of
580,000 gpm, or 835 mgd. Blowdown discharge is driven by the need to
maintain dissolved metals, primarily copper, at concentrations that meet
existing effluent limitations.  

The Unit 1 and Unit 2 velocity caps have been retrofitted to included
electric heaters to reduce the formation of frazil ice during cold water
months.

Nine Mile experienced a significant influx of zebra mussels beginning in
1995.  Nine Mile indicated zebra mussel attachment is most problematic
in the intake tunnel for Unit 2.  Because Unit 1 intake’s tunnel is
larger and has a higher flow, the mussels aren’t as prone to attach to
it.  To reduce zebra mussel attachment in the intake tunnel for Unit 2,
twice a year, Nine Mile Nine Mile applies EVAC (a quaternary ammonium
compound) to the tunnel.  While Nine Mile does not apply EVAC to the
tunnel for Unit 1, it reverses the flow in the intake tunnel.  The hot
water from the reverse flow appears to prevent zebra mussel attachment
in that tunnel.  

Nine Mile also indicated that zebra mussels have greatly improved the
clarity of the lake and that the increased clarity has lead to the
proliferation of cladophora (i.e. seaweed) in the past five years. 
While the cladophora has not impacted Nine Mile’s operation, an
adjacent and similar facility with an off-shore intake structure,
Fitzpatrick, had to shut down its operation due to cladophora intrusion.
 Nine Mile noted the significant safety concerns associated with a loss
of intake flow and the need to maintain a certain amount of incoming
flow to cool the reactor even when it is in shut down mode.

Impingement and Entrainment Information

Constellation Energy has conducted weekly impingement and entrainment
sampling at the Unit 1 intake and surrounding locations as part of its
Comprehensive Demonstration Study to meet Phase II and SPDES
re-application requirements. The sampling will also allow Constellation
Energy to evaluate the relative effectiveness of its current intake
configuration (offshore with velocity cap) to an estimated baseline
configuration that would be representative of a nearshore, unprotected
intake structure. 

The in-plant portion of impingement sampling involves collection and
identification of fish and macroinvertebrates impinged on the traveling
screens on a weekly basis over a two-year period. To establish a
calculation baseline and to demonstrate impingement reductions resulting
from the off-shore intake, gill nets are also set weekly at several
locations in the nearshore area and at offshore locations near the
velocity cap (at sufficient depth in the water column). Gill nets are
set for a 24-hour period and compared to the in-plant impingement rates.

Entrainment sampling is conducted in a similar manner as impingement
sampling on the same weekly schedule. In 2006, Nine Mile conducted
sampling from April to October (entrainment season), but shortened its
sampling from April to August in 2007 based on its 2006 results that
indicated little to no entrainment in the fall months.  In-plant samples
are collected in the screen house prior to the traveling screens using
4-foot diameter bongo nets. To establish a calculation baseline and to
demonstrate entrainment reductions resulting from the off-shore intake,
entrainment is simulated at a nearshore location.  Nine Mile collected a
one-hour composite sample from multiple depths (surface, bottom, and
middle) from a boat located at a near shore location.  Nine mile
collected the samples via a pump and then processed the sample using the
same equipment as described above.  

A final analysis of all collected data has not been completed, but
preliminary findings show a significant difference in the number and
relative species abundance between the actual intake and the offshore
location. 

Facility representatives indicated that Lake Ontario’s aquatic
biology, specifically the number and relative abundance of various fish
species, has changed dramatically over the last 10-15 years.
Biologically-productive areas have moved further offshore from their
historical settings, with invasive and introduced species playing a
significant role in these shifts. 

Cooling Tower Feasibility

The Unit 2 cooling system employs a closed-cycle, recirculating wet
cooling tower. 

Facility representatives stated that retrofitting Unit 1 to closed-cycle
would be difficult given the available space and additional aesthetic
impacts. They noted that the Unit 2 cooling tower is 541 feet tall and
is not plume-abated, meaning a significant visual plume may occur during
colder or more humid months and be visible for long distances. 

Facility representatives noted that the existing condenser, designed for
the current BWR unit, may not have sufficient capacity to handle the
water volume necessary to reject the required thermal load. 

Facility representatives stated that impacts to the unit’s thermal
performance would increase the operating heat rate. Any generating
shortfall would have to be obtained from other sources, potentially
increasing air emissions if fossil fuel plants are used.

Facility representatives noted that a nuclear plant retrofit may involve
significant downtime. 

Attachments

Attachment A		List of Attendees

Attachment B		Aerial Photo

Attachment C		Facility Layout

Attachment D		Site Photo

Attachment E		Onshore CWIS Schematic

Attachment A--List of Attendees

Paul Shriner, EPA

Jan Matuszko, EPA

Tim Havey, Tetra Tech

Kent Stoffle, Constellation Energy

Mary Ellen Dangler, Constellation Energy

Dean Discenza, Constellation Energy

John Walden, Constellation Energy

Terry Syrell, Constellation Energy

Paul Muessig, EA Science

Gary Prye, EA Science

Fred Gillette, NY DEC

Attachment B—Aerial Photo

Please see DCN 10-6510A accompanying this document.

Attachment D—Site Photo

Please see DCN 10-6510B accompanying this document.

Attachment C--Facility Layout

Attachment E--Onshore CWIS Schematic

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