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. The nuclear service water (NSW) system provides cooling to 

nuclear safety components and heat exchangers. [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?] 

The NSW system is not a backup system. The NSW system typically pulls off 

Lake Wylie and the NSW pond is a backup water source to the lake. The NSW 

system is always in service providing cooling to the nuclear safety components in 

the plant. The LPSW system provides cooling water to the non-nuclear safety 

related components in the plant.

• 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 plant 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

involving the loss of Lake Wylie. 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?]

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

the Recirculating Cooling Water (RC) system. Catawba operates six cooling 

towers, three for each unit. The blowdown from the cooling towers flows almost 

continuously at approximately 5,000 gpm via internal Outfall 005, which 

combines with other waste streams into Outfall 001 and is discharged to Lake 

Wylie. 

• Catawba stated that they add sodium hypochlorite and/or Stabrex biocides to 

NSW systems and at the SNSWP intake structure. Sodium hypochlorite is added 

at the LPSW intake structure.

• Catawba adds sodium hypochlorite and/or Stabrex to the NSW system up to four 

hours per day, three to four days per week. Sodium Hypochlorite is added to the 

LPSW system up to 4 hours per day, 2 days per week. The sodium hypochlorite 

and/or Stabrex prevent biofouling and sludge formation on heat exchanger 

surfaces. [QUESTION FOR CATAWBA: Is polyacrylic acid also used for 

biofouling control?] 

Polyacrylic acid is not used for biofouling control. It is used to control solids 

deposition. Biocides and the dispersant are used together to prevent/reduce 

fouling of piping and Heat exchangers 

• Catawba adds a dispersant to the NSW system at the SNSWP intake structure. 

The dispersant increases the efficiency of the biocides. [QUESTION FOR 

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

system?] 

Biocide could be added to the NSW system up to 4 hours per day for up to 4 days 

per week depending on the amount of biofouling. Dispersant is added 

continually. 

• Catawba stated that hydrazine or carbohydrazide are used to lay-up Secondary 

components during refueling outages. This practice prevents corrosion in the 

steam generator tubes due to their ability to act as oxygen scavengers. Catawba 

uses carbohydrazide due to the toxicity of hydrazine. Catawba uses sodium 

hypochlorite to break down the hydrazine or carbohydrazine when wet layup 

chemicals are drained to conventional waste systems. [QUESTION FOR 

CATAWBA: Does the plant add sodium hypochlorite at Outfall 002 or elsewhere 

within the plant?] 

Sodium hypochlorite is added upstream of Outfall 002 for hydrazine control and 

/or for algae control in the conventional wastewater ponds. This wastewater is 

then discharged through Outfall 002 when it is verified that the wastewater is in 

specifications.

• 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 
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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. 

• Catawba stated that during biocide addition to the cooling towers (RC system), 

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

discharge cooling tower blowdown until the chlorine has dissipated). 

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 via RC (reticulating Cooling system).

• 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 diluting 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 

cycle? Please describe how the boron is purged from the system? Which 

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

treated?] 

The source of boron is boric acid. 

The concentration of boron in the primary cooling system at the beginning of the 

fuel cycle varies from about 1600 to 1800 ppm depending on core design. The 

concentration at the end of the fuel cycle is less than 50 ppm.

Water is added to reactor coolant to maintain the desired temperature. The boron 

is diluted and the system volume is maintained by draining the reactor coolant to 

the recycle hold up tanks. Where approximately 80% is reclaimed using an 

evaporator. The remaining 20% is drained to the liquid waste system to control 

on-site inventory of tritium.

Wastewaters from Outfall 004 contain boron. These wastewaters are treated 

using demineralizers and filters. 

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

facility drains. Radioactive liquid waste is segregated. The bulk of the reactor 

coolant drainage is reclaimed and used as makeup to the Reactor Coolant system. 

The remaining radiological wastewaters are transferred to storage tanks in the 

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

containment area. This radioactive liquid waste system processes the water 

through demineralizers and filters.

• Catawba monitors the radioactivity of the wastes stored in the waste collection 

tanks. Catawba then processes the liquid radiological wastes through 

demineralizers and filters to the release tanks. The tanks are then sampled and 

verified in specification for release. [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?]

Radioactive liquid waste is segregated. The bulk of the reactor coolant drainage 

is reclaimed and used as makeup to the reactor coolant system. The remaining 

radiological wastes are processed through demineralizers and/or filters. 

Periodically 1-2 liters of hydrogen peroxide per 5,000 gallons of wastewater are 

added to the liquid radiological waste system.

• 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 discharge into a 

cove, they need to limit the amount of wastes discharged at one time because of 

limited dilution due to discharging into a cove. 

• 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?]

During innage periods Catawba typically has one discharge of approximately 

20,000 gallon per week. During an outage Catawba has 2-3 discharges of 

approximately 5,000 gallons per week in addition to the 20,000 gallon per week 

discharge.

Metal Cleaning Wastes

• Catawba has performed two metal cleaning operations on the let-down piping of 

its reactor coolant system. Catawba used 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 a portable demineralizer. These cleaning are not normal 
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activities. [QUESTION FOR CATAWBA: Please confirm the information is 

correct.]

• Catawba performed a one time metal cleaning operation on the Nuclear Service 

water side of the NS heat exchanger. Catawba used phosphoric acid to reduce 

fouling in the heat exchangers. This cleaning operation was last performed in 

2000 or 2001 and generated approximately 14,000 gallons of wastewater. The 

waste that did not contain radioactivity was discharged through the conventional 

waste system in small batches to ensure all parameters remained in spec. A 

second portion of the waste was drained to radwaste system due to a leaking 

fitting on the pump skid. This waste was treated and transported to a vendor for 

processing 

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

treated as non-hazardous waste. The Demineralizers were only used on the 

cleaning if the letdown piping not the heat exchangers cleaning using Phosphoric 

acid.

• Some of the wastewaters generated by metal cleaning were 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. (Phosphoric Acid 

cleaning of Heat exchanger)

• 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 batch discharges to Lake Wylie 

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

pH in the ponds. Sodium hydroxide may also be used to control algal growth in 

the ponds.
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• 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?] 

The detection limit used by the plant for cadmium is 0.1 ug/L. Per the rational for 

the current permit there was only one data point to consider in the evaluation and 

an insufficiently sensitive PQL. Therefore, additional data is being obtained to 

perform a reasonable potential evaluation.

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

wastewater treatment ponds. Catawba stated that stormwater runoff from the 

plant’s three yard sumps are typically transferred to the hold-up basins. Catawba 

monitors the effluent from the ponds 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 discharged 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
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• 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 and buried in the landfill. The 

contaminated resins and carbon materials were buried either in steel drums or B25s. IHP sludge was not containerized.

• 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. The 

SCDHEC RP Group reviews the lab analyses and pre-approves each burial. 

• 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 

parameters is the plant monitoring? Please provide the five most recent 

groundwater monitoring reports.] 

 Monitoring reports are attached.

 The monitoring parameters are defined by SC Reg 61-107.19 Solid Waste 

Management: Solid Waste Landfills and Structural Fill.

 While CNS has historically been required to analyze for Appendix III 

constituents, in 2009 the site was required to analyze all wells for 

Appendix V constituents as well. After analyses from a minimum of 2 

sequential samplings showed minimal contamination from Appendix V 

constituents, the site and SCDHEC have agreed the Appendix V sampling 

is no longer required for the existing wells. This subject is discussed in 

detail in the 2009-2010 Annual Report.
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Table 1. Site Visit Attendees

Name Organization (Representing) Telephone E-mail

Tara Myers Catawba (803) 701-3940 tara.myers@duke-energy.com

Darrell Davies Catawba (803) 701-3023 Darrell.Davies@duke-energy.com

Steve Rodgers Catawba (803) 701-3370 Steven.Rodger@duke-energy.com

Gary Sain Duke Energy (704) 382-3819 Gary.Sain@duke-energy.com

David Vaught Duke Energy (980) 373-5302 David.Vaught@duke-energy.com

Kim Hamm (intern) Duke Energy

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

Marshall Huffstetler Duke Energy (803) 701-3334 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.]

Kim Hamm was a co-op student during EPA’s site visit. She is, currently, not employed by Duke Energy.