Document ID: EPA-HQ-OW-2008-0667-0055
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2010-11-15T05:00Z

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).

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 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.  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).  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.
      
      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.  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.
      
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)

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

Please see DCN 10-6522A accompanying this document.