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Site Description Report

Cooper Nuclear Station

1200 Prospect Road

Brownville, NE 68321

March 2, 2009

1.0 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 typical 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. As part of its site visit to the Nebraska City Station, EPA also 

collected information on Nebraska Public Power District’s (NPPD) Cooper 

Nuclear Station (Cooper).

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2.0 Facility Description

Cooper is located about 3 miles south of the town of Brownville in eastern 

Nebraska on a 1300 acre site. The facility operates under NPDES permit 

NE0001244; the permit expired June 30, 2006.

3.0 Electricity Generation and Transmission

Cooper is a nuclear generating station with one reactor capable of generating 800 

MW.

4.0 Cooling Water System and Intake Structure

Cooper withdraws once-through cooling water from a CWIS on the shoreline of 

the Missouri River. The facility’s design intake flow (DIF) is 964 million gallons 

per day (mgd) and the average actual intake flow (AIF) is 747 mgd.

Water passes through a trash rack and then into 9 intake bays; each intake bay has 

a dual flow coarse mesh (3/8”) traveling screen and each pair of bays feeds a 

circulating water pump with a capacity of 229 mgd (or 159,000 gallons per 

minute [gpm] each). One bay feeds the service water pumps, which have a total 

 

1 NPPD is a different branch of the state electricity generation agency than Omaha Public Power District 

(OPPD) but operates in concert with OPPD.
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capacity of 43.2 mgd (or 30,000 gpm). The design through-screen velocity ranges 

from 1.7 to 2 feet per second (fps).

To better handle debris and sediment loading, the facility has taken several steps 

in the past. See Section 7.0 for more information.

5.0 Impingement and Entrainment Information

Facility representatives noted that impingement counts at Cooper are very low 

and that many of the collected organisms were shad. They also stated that many 

of the pre-approved impingement approaches in the 2004 Phase II rule were 

unappealing. For example, the 0.5 fps threshold is likely infeasible on large rivers 

and barrier nets would likely be destroyed by debris. Entrainment has not been 

studied in any detail.

6.0 Cooling Tower Feasibility

Facility representatives noted that they have explored converting to close-cycle 

cooling; the cost was estimated to be $400 million, largely due to nuclear safety 

procedures. They did not identify any insurmountable technical hurdles. Water 

consumption was also raised as a potential problem.

7.0 Debris Handling

Cooper installed a sloping weir wall in the early 1970s to better control sediment 

loading at its CWIS.2 The design was based on river flows typical of time and 

was reviewed by the Army Corps of Engineers and the Iowa Institute of 

Hydraulics. The wall begins on the upstream side of the screenhouse and extends 

slightly above the water’s surface. The wall gradually becomes shorter as it 

extends downstream; this design was expected to shield the CWIS from excessive 

sedimentation by channeling suspended sediment beyond the CWIS. In the past, 

sedimentation caused pump shutdowns from clogging and requires mechanical 

excavation every 6 months (usually by divers).3 Sediment has also significantly

increased the maintenance required for the traveling screens, increased the 

frequency of backwash cycles, and has restricted intake flow piping. Facility

representatives noted that Fort Calhoun is considering installing a similar wall.

The facility also added turning vanes along the river bottom to steer flow (and 

sediment) away from the CWIS. Sonar sensors were also added in the 

screenwells to measure the amount of sedimentation.

 

2 The weir wall also diverts some ice in the winter.

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Sonar sensors in the screenwells detect sediment levels. Backwash cycles (using divers) lead to a 

reduction in generation (derating), as well as additional concerns over thermal discharges due to the lower 

volume of cooling water being withdrawn.
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Cooper also has problems with debris loading. Debris carryover from the 

traveling screens clogs the condenser tubes, requiring frequent cleaning. Facility

representatives noted that the condenser must be backwashed on approximately a 

weekly basis, requiring a temporary shutdown.4 Some debris remains and must 

be manually cleaned out during the next regularly scheduled outage.

In the past 2 years, Cooper has replaced its single-entry traveling screens with 

dual-flow screens to reduce the debris carryover. This conversion cost 

approximately $6 million. By the time the installation was completed, 

maintenance was required on the first set of screens that were installed.

Despite the changes, condenser backwash and sediment removal remain as 

operational challenges, although problems are now less frequent.

Ice has been a historic problem at Cooper as well. Ice floes in the river often 

break into smaller parts that can clog the open area of the screens, leading to as 

much as a 5 foot differential across the screens. Cooper installed an ice deflector 

in the river to divert surface level ice away from the CWIS.

8.0 Repowering/Future Uses

EPA did not collect any information about repowering at this site.

9.0 Cooling Ponds

There are no cooling ponds onsite.

10.0 Ownership

NPPD is a public utility that is owned by the state of Nebraska. The entire state is 

supplied by public power.

11.0 316(a)

EPA did not collect any information about thermal discharges at this site.

12.0 Ash Handling

Cooper does not use coal as a fuel and therefore has no ash ponds.

13.0 Air Emissions Controls

EPA did not collect any information about air controls at this site.

 

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Facility representatives noted that 3220 MWhrs were lost in 2002 due to 45 condenser backwash cycles.
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14.0 Additional Information

Cooper had intended to comply with the 2004 rule by installing modified Ristroph 

screens with a low pressure spray and separate fish return.

Facility representatives noted that they had considered a sedimentation pond at 

the CWIS, but were concerned about the ability to maintain a consistent flow, the 

need for constant dredging, and the ability of such a system to adapt to the large 

changes in river level.

Facility representatives stated that, at another facility (Gerald Gentleman, located 

on an inland lake) the state fish and game agency has expressed an interest in 

maintaining once-through cooling, as there are too many shad in the waterbody

and the cooling water withdrawals are helpful in culling the population of less 

desirable fish. Additionally, the canals feeding the lake are completely drained 

every 5 years per Federal Energy Regulatory Commission (FERC) requirements, 

killing any remaining fish or invertebrates.

Attachments

Attachment A PowerPoint Presentation (March 2, 2009)
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Attachment A—PowerPoint Presentation (March 2, 2009)

Please see DCN 10-6522A accompanying this document.