Draft Notes from Site Visit at Duke Energy's Catawba Nuclear Station on October 19, 2009

EPA conducted a site visit at Duke Energy’s Catawba Nuclear Station (Catawba) located in 

York, SC on Monday, October 19, 2009 to learn about the operations at the plant and the 

wastewaters generated at the plant. Table 1, located at the end of this memorandum, identifies 

the site visit participants. The presentation that the Catawba personnel gave during the site visit 

is provided as Attachment 1 to this memorandum. An overall water balance diagram for the 

plant is included within Attachment 1.

This memorandum describes the information collected during the site visit and the pre-site visit 

phone call, which was held on October 13, 2009.

Plant Overview

• The Catawba plant is located on a 500-acre site next to Lake Wylie. Lake Wylie 

has a total surface area of 13,443 acres with 325 miles of shoreline. The plant 

intake from the lake is approximately 110 MGD.

• Catawba operates two identical nuclear-fueled electric generating units. 

Information on the two nuclear units is summarized in the table below.

Unit Installation 

Date

Gross 

Capacity 

(MW)

Reactor Type Fuel

1 1985 1,129

Westinghouse 

Pressurized water 

reactor (PWR)

Uranium dioxide

2 1986 1,129 Westinghouse PWR Uranium dioxide
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• Units 1 and 2 are both fueled by uranium dioxide. Both reactors are refueled 

approximately every 18 months. Units 1 and 2 are refueled on staggered intervals,

refueling one unit approximately every 9 months so that only one unit is nonoperational at a time. 

• Catawba stated that the next refueling cycle is scheduled to begin in late 

November 2009 and takes approximately 30 days to complete. During refueling 

outages, the plant may have as many as 1,800 contractors on site.

• Catawba stated that the analog equipment in the control room of Unit 1 will be

upgraded to a digital control system during the upcoming refueling outage. The 

digital control system will be the first of its kind in the United States. Catawba 

plans to upgrade Unit 2 to a digital system in Fall 2010.

• Each unit has a separate spent fuel pool and fuel storage area. 

• Catawba has 1,270 employees. The plant typically has an additional 450-500 

contractors on site. 

Nuclear Service Water (NSW) and Low-Pressure Service Water (LPSW) Systems

• Catawba stated that there are two service water systems at the plant, both of 

which use water from Lake Wylie. The low-pressure service water (LPSW)

system is the primary water system that is used to provide cooling for the steam 

turbine cycle and cooling water for the nuclear reactor. The nuclear service water 

(NSW) system is a back up water system that can be used if there are issues with 

the LPSW system. Although the NSW system is a back-up, the system operates 

continuously, but not at full capacity. [QUESTION FOR CATAWBA: Please 

confirm that the NSW is primarily used as a back-up system. Is the NSW used to 

as cooling water for processes that the LPSW system does not cool?]

• As an added safety measure, the NSW system has the capability of withdrawing 

intake water from either Lake Wylie or the plant’s standby nuclear service water 

pond (SNSWP). The SNSWP is maintained by the plant and the plant uses water 

from Lake Wylie to keep the pond at an acceptable level in case of emergencies. 

Therefore, if the water level in Lake Wylie was too low for the plant to withdraw 

water, then the plan would use the water reserve in the SNSWP. Catawba stated 

that they have never had to use the SNSWP water as a result of an emergency. 

However, the intake pumps are tested periodically. The plant has an outfall for 

the transfer of water from the SNSWP to Lake Wylie in case the SNSWP 

becomes to full, which is Outfall 006. [QUESTION FOR CATAWBA: What is 

the volume of the SNSWP?]

• Catawba operates cooling towers to recirculate the steam turbine cooling water in 

the LPSW system. Catawba operates six cooling towers, three for each unit. The 

blowdown from the cooling towers flows almost continuously at approximately 
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5,000 gpm via internal Outfall 005, which commingles with other waste streams 

into Outfall 001 and is discharged to Lake Wylie. 

• Catawba stated that they add sodium hypochlorite and/or sodium bromide 

biocides to the LPSW and NSW systems and at the SNSWP intake structure. 

• Catawba adds sodium hypochlorite and/or sodium bromide to the LPSW system 

approximately four hours per day, three to four days per week. The sodium 

hypochlorite and/or sodium bromide prevent biofouling and sludge formation on 

heat exchanger surfaces. Catawba stated that during biocide addition, the plant 

isolates the blowdown from the cooling towers (i.e., they do not discharge cooling 

tower blowdown). [QUESTION FOR CATAWBA: Is polyacrylic acid also used 

for biofouling control?]

• Catawba adds a dispersant at the NSW and SNSWP intake structures. The 

dispersant increases the efficiency of the biocides. [QUESTION FOR 

CATAWBA: What is the frequency and duration of biocide addition for the NSW 

system?]

• Catawba stated that hydrazine or carbohydrazide are used to prevent corrosion in 

the boiler tubes due to their ability to act as oxygen scavengers. Catawba stated 

that the Occupation Safety and Health Administration (OSHA) recommended the 

use of carbohydrazide as an alternative to hydrazine due to hydrazine’s toxicity.

Catawba uses sodium hypochlorite to break down the hydrazine or 

carbohydrazine. [QUESTION FOR CATAWBA: Does the plant add sodium 

hypochlorite at Outfall 002 or elsewhere within the plant?]

• The plant adds sodium bisulfite at Outfall 001 to dechlorinate the water before 

discharging into Lake Wylie. Catawba operates two sodium bisulfite pump trains, 

one of which is a back up system. Catawba has oxidation reduction potential 

probes that are used to determine the amount of sodium bisulfite needed. Catawba 

stated that the required contact time for the dechlorination reaction is 30 minutes. 

Nuclear Unit Operations and Wastewaters 

• The energy from fission of uranium dioxide fuel heats the primary reactor cooling 

system. The primary cooling system is pressurized to ensure that the coolant in 

the primary loop does not boil. Pressure, temperature, and flow rate are adjusted 

to enable the efficient transfer of heat from the reactor to the coolant. The primary 

cooling system then transfers heat to the secondary system which generates steam. 

The steam is used to generate electricity and then Catawba uses water from Lake 

Wylie to condense the steam.

• Boron is a neutron moderator and is used in the primary cooling system to 

maintain the desired rate of fission within the reactors. As the uranium fuel starts 

slowly losing its reactivity, the plant begins purging some of the boron from the 

system because less is needed to control the reaction. [QUESTION FOR 

CATAWBA: What is the source of boron (e.g. boric acid)? What is the 

concentration of boron in the primary cooling system at the beginning of the fuel 
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cycle? Please describe how the boron is purged from the system? Which 

wastewaters generated at the plant contain boron? How are these wastewaters 

treated?]

• Catawba’s reactor cooling system and radiological liquid waste processing system 

are designed to minimize the release of radioactive liquids to unrestricted parts of 

the plant.

• The liquid radiological wastes generated at Catawba include wastewaters from 

drains from the contained nuclear reactor area including reactor cooling system 

equipment drains, floor drains, decontamination drains, and laundry and shower 

facility drains. These radiological wastewaters are transferred to storage tanks in 

the auxiliary building and waste monitor tank building, adjacent to the reactor 

containment area.

• Catawba monitors the radioactivity of the wastes stored in the tanks. Catawba 

then transfers the liquid radiological wastes to the radiological waste treatment 

system, which consists of demineralization and filtration. [QUESTION FOR 

CATAWBA: Does the plant treat all the radiological wastes through the 

demineralizers and/or filters? Does the plant perform any chemical treatments on 

the liquid radiological wastes? If so, what chemicals and amounts are used?]

• The treated liquid radiological wastes are then discharged via internal Outfall 004 

to Outfall 001, which discharges to Lake Wylie. The liquid radiological wastes 

generated at the plant are discharged in batches. Catawba performs calculations to 

determine the amount of waste which can be released to the discharge canal 

according to NRC regulations. Catawba stated that because they operate a 

recirculating cooling water system, they need to limit the amount of wastes 

discharged at one time because they don’t have as much dilution water as a oncethrough plant. 

• Catawba stated that they typically discharge a batch of liquid radiological wastes 

twice a week; however, it is more frequent during outages because they are 

draining a lot of the equipment. [QUESTION FOR CATAWBA: How does the 

frequency of the discharge vary from the beginning of the fuel cycle to the end of 

the fuel cycle? What are typical volumes discharged?]

Metal Cleaning Wastes

• Catawba performs metal cleaning operations on the let-down piping of its 

electrical system. Catawba uses nitric acid and EDTA to perform the cleaning. 

This cleaning was last performed in May 2008 and September 2007, and each 

occurrence generated approximately 500 gallons of wastewater, which were 

treated by the demineralizer. [QUESTION FOR CATAWBA: Please confirm the 

information is correct.]

• Catawba performs metal cleaning operations of the heat exchangers from the 

reactor primary cooling system. Catawba uses phosphoric acid to reduce fouling 

in the heat exchangers. This cleaning operation was last performed in 2000 or 
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2001 and generated approximately 14,000 gallons of wastewater, which was 

diluted significantly and then hauled off site by a vendor. 

• The spent resins from the demineralizer are monitored for radioactivity and 

treated as hazardous waste. 

• Some of the wastewaters generated by metal cleaning are discharged in small 

batches from Outfall 002 (conventional wastewater treatment plant effluent) or 

Outfall 004. The effect of discharging in batches is that the plant can dilute the 

metal cleaning wastewater and not exceed its permit limits.

• Catawba does not perform metal cleaning operations on the turbines. 

Other Plant Wastewaters and Treatment Systems

• Outfall 001 is the largest flow outfall at the plant and discharges once-through 

cooling water, nuclear service water, cooling tower blowdown (via internal 

Outfall 005), and liquid radiological wastes (via internal Outfall 004) to Lake 

Wylie. There are no dilution specifications for Outfall 001.

• Catawba operates a conventional wastewater treatment system to treat the 

wastewaters collected in sumps at the plant that are not located within the nuclear 

containment area. 

• The conventional wastewater treatment system consists of two ponds, each 5 

million gallons in volume. The ponds alternate between discharging and receiving 

wastewater. Catawba stated that the plant switches between the ponds every one 

to two weeks. Catawba stated that it takes approximately three and a half days to 

drain one of the ponds and the flow rate from the pond is approximately 1,500 

gpm. 

• The conventional wastewater treatment system discharges directly to Lake Wylie 

via Outfall 002. Catawba can add sodium hydroxide or sulfuric acid to adjust the 

pH in the ponds.

• Catawba stated that Outfall 002 has “monitor and report” requirements for a 

number of pollutants, including cadmium, zinc, hydrazine, and 

pentachlorophenol. Catawba stated that the plant is required to monitor for 

cadmium even though the plant has never detected cadmium in the effluent. 

During Catawba’s permit application Form 2C data collection requirement, they 

reported cadmium as less than the detection limit. However, the detection limit 

was not less than the concentration necessary to avoid to the requirements for

monitoring and reporting cadmium as determined by the permit writer.

[QUESTIONS FOR CATAWBA: What is the detection limit of cadmium for the 

method used by the plant? What was the concentration required by the permit 

writer?]

• Catawba operates two hold-up basins adjacent to the two conventional wastewater 

treatment ponds. Catawba stated that stormwater runoff from the plant’s three 
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yard sumps are transferred to the hold-up basins. Catawba monitors the effluent 

from the basins for pH and radiological activity (curies). The discharge of the 

hold-up basins is combined with the discharge from the conventional wastewater

treatment ponds and discharge via Outfall 002. Catawba stated that the plant only 

discharges from the hold-up ponds when the plant is also discharging from the 

conventional wastewater treatment ponds. 

• Catawba performs whole effluent toxicity (WET) tests on Outfalls 001 and 002 

quarterly and must meet discharge limitations on Ceriodaphnia dubia survival 

from these outfalls as required by the plant’s permit. In the summer of 2008, 

Catawba had a failure in its WET test for Outfall 002. Catawba stated that the 

issue didn’t occur in September of 2008, but they failed another WET test in the 

summer of 2009. At the time, Catawba believed that blue-green algae growth in 

the hold-up ponds is likely responsible for these difficulties. Prior to these recent 

failures, Catawba had not experienced a toxicity failure for 10-15 years.

• Catawba stated that the hold-up ponds are aerated to keep the ponds from being 

stagnant. Additionally, Catawba is using sodium hypochlorite to reduce the 

amount of blue-green algae in the ponds.

• Catawba stated that they used to discharge treated sanitary wastewater via Outfall 

003; however, the plant now transfers the sanitary wastewater to the county for 

treatment. 

• Outfall 006 discharges water from the SNSWP into Lake Wylie in the event of 

overflow.

Landfill

• Catawba operates a landfill for the storage of low-level radiological wastes and 

sludges and asbestos from old piping insulation. The landfill is not lined and 

therefore does not collect leachate. Additionally, the landfill is relatively small 

and flat, compared to coal combustion waste landfills at coal-fired power plants. 

• Radioactive wastes are stored in containers (barrels) and buried in the landfill.

• Low-level radioactive wastes consist of material that has become radioactive due 

to neutron radiation at any point during plant operations and meet low-level 

criteria established by the Nuclear Regulatory Commission (NRC). This includes 

material previously classified as high-level radioactive waste that has been stored 

on site long enough for the material to decay to low-level classification. 

• Catawba stated that the wastes stored in the landfill are not significantly more 

radioactive than the background radiation levels found in nature.

• Catawba is required to monitor the groundwater around the perimeter of the 

landfill semi-annually (during March and October). However, there are no water 

quality requirements for the groundwater. [QUESTION FOR CATAWBA: What 
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parameters is the plant monitoring? Please provide the five most recent 

groundwater monitoring reports.]
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Table 1. Site Visit Attendees

Name Organization (Representing) Telephone E-mail

Tara Myers Catawba (704) 747-5001 tara.myers@duke-energy.com

Darrell Davies Catawba

Steve Rodgers Catawba

Gary Sain Catawba

David Vaught Catawba

Kim Hamm Duke Energy

Robert Wylie Duke Energy (704) 382-4669 Robert.wylie@duke-energy.com

Marshall Huffstetler Duke Energy (864) 630-7856 david.huffstetler@duke-energy.com

Josh Hall EPA/Office of Water (202) 566-1003 hall.josh@epa.gov

Jezebele Alicea EPA/Office of Water (202) 566-1755 alicea.jezebele@epa.gov

TJ Finseth ERG (Contractor to EPA) (703) 633-1698 thomas.finseth@erg.com

Kurt Blohm ERG (Contractor to EPA) (703) 633-1675 kurtis.blohm@erg.com

Donna Hill UWAG (205) 257-5234 dbhill@southernco.com

[QUESTION FOR CATAWBA: Please provide the missing phone numbers and e-mail addresses.]