3.4 Operational Activities
3.4.2 Plant-Environment Interfaces During Operation
6
This section describes the activities related to structures with an interface to the environment 7
during operation of the proposed Units 1 and 2. 8
3.4.2.1 Water Withdrawals and Transfers
9
Duke has developed and proposed a plan for managing water withdrawal from the Broad River 10
and water transfers between makeup ponds that “… will support operation of Lee Nuclear 11
Station, yet maintain appropriate instream flows in the Broad River during drought conditions.” 12
Duke has requested that the following water-management plan, excerpted verbatim from its 13
NPDES permit application, be incorporated into its NPDES permit conditions (Duke 2011a): 14
“• To minimize withdrawal of water during low-flow periods, a drought contingency pond 15
(Pond C) will be built to complement existing drought contingency Pond B. 16
• During normal flow periods on the Broad River (>538 cfs), Duke Energy will withdraw 17
all of its operational water requirements from Ninety‐Nine Islands Reservoir through 18
the primary section of the river intake into existing sedimentation Pond A. The primary 19
section of the river intake will have a design intake flow of 98 cfs. Pond A will provide 20
water for plant processes and cooling tower makeup. Based on the historical Broad 21
River flow conditions, Duke Energy anticipates this will be the normal withdrawal 22
scheme employed greater than 95 percent of the time. 23
• As the Broad River flow drops below 538 cfs and begins to approach 483 cfs, Duke 24
Energy will proportionally withdraw its consumptive water requirements (≤63 cfs) from 25
Ninety-Nine Islands Reservoir and drought contingency Ponds B and C. Pond B will 26
be drawn down first. If Pond B drawdown reaches 30 feet, drawdown from Pond B will 27
cease and water will be withdrawn from Pond C to a nominal drawdown ≤30 feet. 28
• When Broad River flow is at or below 483 cfs, only non‐consumptive cooling water 29
(approximately 23 cfs) will be withdrawn from the Ninety‐Nine Islands Reservoir. That 30
water will be returned to the reservoir immediately after use in order to maintain 31
adequate flows in the Broad River. The remaining water needed to operate Lee 32
Nuclear Station (≤63 cfs) will be drawn from drought contingency Ponds B and C. 33
Pond B will be drawn down first. If Pond B drawdown reaches 30 feet, drawdown from 34
Pond B will cease and water will be withdrawn from Pond C to a nominal drawdown 35
Site Layout and Plant Description
Draft NUREG-2111 3-36 December 2011
≤30 feet. Based on modeling using worst case droughts over the 85‐year period of 1
record, Duke Energy does not anticipate that any additional drawdown will be needed. 2
However, should it be warranted to support station operations during emergency 3
drought conditions, any additional drawdown or other water management protocols will 4
be performed pursuant to a drought contingency plan to be developed in accordance 5
with the South Carolina Water Withdrawal Law after consultation with appropriate 6
regulatory agencies. 7
• During the period of July through February, and only when the Broad River flows are 8
above 483 cfs, Ponds B and/or C will be refilled, as needed, by withdrawing water from 9
Ninety‐Nine Islands Reservoir through the drought contingency section of the river 10
intake. During this period, the water necessary to operate the station will also be 11
withdrawn from the Ninety-Nine Islands Reservoir via the primary section of the river 12
intake. 13
• The drought contingency section of the river intake will have a maximum design intake 14
flow of 206 cfs. However, the actual refill rate will be determined using a flow-sensitive 15
approach to ensure Broad River flows do not fall below 483 cfs due to refill of the 16
drought contingency ponds. Further, regardless of river flows, refilling of Ponds B and 17
C will not occur from March through June, in order to minimize entrainment.” 18
This proposed water-management plan would guide the water withdrawals and transfers 19
described in the remainder of this section. 20
Broad River Intake Structure
21
The Broad River would be the primary source of water for cooling and other plant water 22
systems. As described in Section 3.2.2.2, the Broad River intake structure comprises two 23
subsystems: (1) the river water subsystem and (2) the makeup pond refill subsystem (see 24
Figure 3-12). The river water subsystem would supply raw water to Units 1 and 2. It would 25
operate continuously as long as flow in the Broad River meets the consumptive water use 26
needs and the Federal Energy Regulatory Commission (FERC) minimum continuous flow 27
requirement from Ninety-Nine Islands Reservoir. Under normal operating conditions for both 28
units, two of the four river water subsystem pumps would be running, and the withdrawal rate 29
would be 35,030 gpm (78 cfs). About 2000 gpm (4.5 cfs) would be used for the screen wash 30
system and thus return to the river at the intake location; the remaining 33,030 gpm would be 31
pumped to Make-Up Pond A to serve as the source of water for the CWS and other station 32
water systems (Duke 2009b). Occasionally, one or both standby pumps would be used to 33
maintain the water level in Make-Up Pond A if additional water was being withdrawn to recover 34
the level of Make-Up Pond B, to fill the cooling tower basins, or for other CWS system 35
maintenance. If all four river water subsystem pumps were operating, the maximum withdrawal 36
rate would be 60,000 gpm (134 cfs). 37
Site Layout and Plant Description
Figure 3-12
. Diagram of Water-Supply and Water-Transfer System (Du
Site Layout and Plant Description
Draft NUREG-2111 3-38 December 2011
When flow in the Broad River is unable to meet the consumptive use and the FERC minimum 1
flow requirement, water would be transferred from Make-Up Pond B to Make-Up Pond A, and 2
proportionally less water would be withdrawn from the Broad River, so that Lee Nuclear Station 3
operations would not cause flow in the Broad River to drop below the required minimum 4
release. When flow in the Broad River is at or below the FERC minimum flow requirement, the 5
river water subsystem withdrawal would be limited to the blowdown and screen wash volumes, 6
or about 23 cfs (Duke 2009b, 2010k). 7
The makeup pond refill subsystem would operate infrequently and intermittently, primarily to 8
refill Make-Up Pond C when its level is low and when river flow and water withdrawal permit 9
conditions allow the additional water to be withdrawn from the Broad River. The refill subsystem 10
also could be used to transfer water directly to Make-Up Pond B. Withdrawal from the Broad 11
River via the refill subsystem (up to four pumps operating) could range up to 92,200 gpm 12
(205 cfs) with 2500 gpm (5 cfs) returning to the river as screen wash water. The remaining 13
87,900 gpm (200 cfs) would be routed to Make-Up Pond C or Make-Up Pond B as needed to 14
restore the ponds to normal operating levels (Figure 3-12) (Duke 2009b). Refill subsystem 15
withdrawal rates would be variable and intermittent because of the dependence on river flow 16
conditions and consideration of fish spawning periods or seasonal minimum flows. 17
Make-Up Pond Intakes, Discharges, and Water Transfers
18
Make-Up Pond A 19
Under normal plant operating conditions, four of the six pumps in the Make-Up Pond A intake 20
structure would operate continuously to supply the CWS, SWS, demineralized treatment system, 21
and fire protection systems at a rate of 33,030 gpm. Occasionally, one or both of the standby 22
pumps would be used during system maintenance or to refill Make-Up Pond B after Make-Up 23
Pond B had been drawn down to refill Make-Up Pond A during periods when there were 24
limitations on water withdrawal from the Broad River. The maximum withdrawal rate from Make- 25
Up Pond A would be about 57,500 gpm. The standby pumps could be used to transfer water to 26
Make-Up Pond B at up to 24,814 gpm (Duke 2009b, 2010a). Duke does not plan to draw down 27
Make-Up Pond A; the water level in Make-Up Pond A would be maintained by transferring water 28
from Make-Up Pond B during low flow periods when withdrawal from the Broad River is limited. 29
During normal operation, continuous discharge would occur at the Make-Up Pond A discharge 30
structure because Make-Up Pond A is continuously providing water to the station cooling system. 31
Make-Up Pond B 32
The intake pumps at Make-Up Pond B would operate only when low-flow conditions limit 33
withdrawal of Broad River water for plant use. As noted above, once Broad River flows drop 34
below the minimum flow requirement, proportionally less water would be withdrawn from the 35
Site Layout and Plant Description Broad River and proportionally more water would be transferred from Make-Up Pond B to
1
Make-Up Pond A, up to 24,814 gpm (Duke 2009b). Table 3-1 shows that Make-Up Pond B can 2
be drawn down a maximum of 30 ft. 3
Duke estimated the frequency, magnitude, and duration of Make-Up Pond B drawdown events 4
by applying proposed operational withdrawals for Units 1 and 2 to daily flows in the Broad River 5
over an 85-yr period (January 1926 through December 2010). Duke assumed a minimum 6
continuous flow requirement of 483 cfs plus a 60 cfs allowance for future water demands in the 7
Broad River. In that 85-yr period of record, Duke calculated that Make-Up Pond B would have 8
been drawn down 191 times, and that five of those events would have reached the maximum 9
drawdown of 30 ft (Figure 3-13,Table 3-6) (Duke 2009b, 2011e). 10
11
Figure 3-13. Estimated Number of Make-Up Pond Drawdown Events Based on 85-Year 12
Historical Flow Record for Broad River (adapted from Duke 2011a) 13
Site Layout and Plant Description
Draft NUREG-2111 3-40 December 2011
Table 3-6. Estimated Frequency, Magnitude, and Duration of Make-Up Pond B Drawdown 1
Events Based on 85-Year Historical Flow Record for the Broad River 2 Drawdown Range (ft) Estimated Number of Events Highest Magnitude Event (ft)(a) Longest Duration Event (days)(b) 0–0.5 47 0.5 2 0.5–1 56 1.0 3 1–2 43 2.0 4 2–3 15 3.0 6 3–4 7 3.5 10 4–5 6 4.8 9 5–6 2 5.3 27 6–20 8 17.3 62 20–30 3 30.0 61 ≥30 4 30.8 139
Source: Duke 2010k, Duke 2011a
(a) Only the largest drawdown event in Figure 3-13 is shown for each range of drawdown. Magnitudes of drawdown greater than 30 ft are due to evaporation loss when pond has no usable storage.
(b) Duration is sum of days to reach lowest elevation, days at lowest elevation, and days to refill to full pond elevation of 570 ft above MSL, assuming refill begins on the first day that water can be pumped from the Broad River into Make-Up Pond B.
During periods when withdrawal from the Broad River is reduced, the Make-Up Pond B intake 3
pumps would operate continuously to pump water to Make-Up Pond A. Figure 3-14 shows the 4
change in surface area and storage volume as the water level in Pond B is drawn down. 5
Historically, more than 90 percent of Make-Up Pond B drawdown events would have been 5 ft 6
or less and lasted 10 days or less (duration includes time to refill) (Table 3-6). 7
Duke’s longest modeled drawdown event within the capacity of Make-Up Pond B (meaning 8
the event would not have required pumping from Make-Up Pond C) was 22 days, followed by 9
17 days to refill to its normal elevation of 570 ft above MSL, for a total duration of 39 days (Duke 10
2009b, 2010k). Maximum drawdown events (more than 30 ft) would have occurred infrequently 11
in Make-Up Pond B, but their duration would have been prolonged, at least 25 days plus time to 12
refill (Table 3-6, Figure 3-14). Maximum drawdown events would require pumping water from 13
Make-Up Pond C to maintain the minimum elevation in Make-Up Pond B. The water level of 14
Make-Up Pond B would be restored as soon as flow and permit conditions allowed withdrawal 15
from the Broad River. 16
Site Layout and Plant Description p 0 20 40 60 80 100 120 140 160 500 510 520 530 540 550 560 570 580 Elevation (ft MSL) S u rf ac e A rea ( a c) 0 500 1000 1500 2000 2500 3000 3500 4000 4500 V o lu m e (a c -ft)
Stage-Area Maximum Drawdown Stage-Volume 20 d
10 d 5 d
15 d
25 d
Average Rate of Decline for Elevation Range*:
560-570 ft, 0.94 ft/d 550-560 ft, 1.21 ft/d 540-550 ft, 1.65 ft/d
* Average rates of decline used to calculate days of drawdown indicated on graph, assuming no
contribution to pond volume from refill or precipitation. 1
Figure 3-14. Stage-Area and Stage-Volume for Make-Up Pond B, Showing Area at 5, 10, 15, 2
20, and 25 Days of Transfer to Make-Up Pond A (data sources: Duke 2009b, 3
2010k) 4
The Make-Up Pond B discharge structure would be used whenever water was pumped in from 5
Make-Up Pond C, and whenever Make-Up Pond B was refilled. Refill events would be 6
associated with each drawdown event, but would be intermittent and variable because of their 7
dependence on Broad River flow conditions. Based on the historical flow record, the duration of 8
refill would typically be up to 2 days for drawdowns of 5 ft or less (91 percent of events), but 9
could be more than 30 days during extended periods of Broad River water limitations (Duke 10
2009b). 11
Make-Up Pond C 12
The intake pumps at Make-Up Pond C would operate even less frequently than those in 13
Make-Up Pond B. Water would be withdrawn from Make-Up Pond C when low-flow conditions 14
in the Broad River are prolonged to the point that the usable storage in Make-Up Pond B is 15
depleted (Table 3-6). Water would be pumped from Make-Up Pond C to Make-Up Pond B at up 16
to 24,814 gpm (55 cfs) (Duke 2009b). Based on the 85-yr historical record, Duke estimated that 17
water would have been transferred from Make-Up Pond C to Make-Up Pond B five times 18
(Figure 3-13), and that the Make-Up Pond C drawdown would not have exceeded 20 ft during 19
any of those events. Figure 3-15 shows the change in surface area and storage volume as the 20
water level in Make-Up Pond C is drawn down. The discharge portion of the Make-Up Pond C 21
combined intake/discharge structure would only be used during refill operations. 22
Site Layout and Plant Description
Draft NUREG-2111 3-42 December 2011
0 100 200 300 400 500 600 700 500 520 540 560 580 600 620 640 660 Elevation (ft MSL) A rea ( a c) 0 5000 10000 15000 20000 25000 V o lu m e (a c -ft)
Stage-Area Maximum Drawdown Stage-Volume
15 d 30 d 60 d
120 d
Average Rate of Decline for Elevation Range*: 640-650 ft, 0.24 ft/d 630-640 ft, 0.29 ft/d 620-630 ft, 0.36 ft/d 610-620 ft, 0.44 ft/d 605-610 ft, 0.57 ft/d
* Average rates of decline used to calculate days of drawdown indicated on graph, assuming no
contribution to pond volume from refill or precipitation. 1
Figure 3-15. Stage-Area and Stage-Volume for Make-Up Pond C, Showing Area at 15, 30, 60, 2
and 120 Days of Transfer to Make-Up Pond B (data sources: Duke 2009b, 2010k) 3
3.4.2.2 Other Plant-Environment Interfaces During Operation
4
Cooling Towers
5
Waste heat is a byproduct of normal power generation at a nuclear power plant. Excess heat in 6
the cooling water would be transferred to the atmosphere by evaporative and conductive cooling 7
in the cooling tower. In addition to evaporative losses, a small percentage of water would be 8
lost in the form of droplets (drift) from the cooling towers, potentially causing visible plumes. 9
Water lost to evaporation and drift is considered consumptive use because the water is not 10
available for reuse. As with water withdrawal, the normal case assumes the cooling towers are 11
operating at four cycles of concentration. The cycles of concentration refers to the number of 12
times that water circulates through the closed-cycle cooling-water system before some of it is 13
discharged as blowdown. This is done to limit the amount of dissolved solids in the water; the 14
number of cycles of concentration is used to calculate the concentration of dissolved solids in 15
the effluent. Duke provided the following typical consumptive use rates (Duke 2009c): CWS 16
normal and maximum evaporation rates would be 24,270 and 28,026 gpm (54 and 62 cfs), 17
respectively; SWS normal and maximum evaporation rates would be 368 and 1248 gpm (0.8 18
and 2.8 cfs), respectively; and drift rates of 3 gpm for the CWS and 1 gpm for the SWS would 19
not change with the number of cycles of concentration (Duke 2009c). Actual cooling tower 20
consumptive use rates would vary with atmospheric conditions (temperature and relative 21
humidity). In its analysis of plant water use and pond drawdown, Duke used the monthly 22
consumptive use rates shown in Table 3-7 (Duke 2010k). 23
Site Layout and Plant Description Table 3-7. Consumptive Water Use Rates by Month for Proposed Lee Nuclear Station Units 1 1
and 2 2
Month
Total Plant Consumptive Use for Two Units (gpm)
Total Plant Consumptive Use for Two Units (cfs)
January 22,846 50.9 February 23,384 52.1 March 24,775 55.2 April 26,122 58.2 May 26,975 60.1 June 27,783 61.9 July 28,276 63.0 August 27,962 62.3 September 27,109 60.4 October 25,763 57.4 November 24,506 54.6 December 23,294 51.9
Source: Duke 2010k, 2011e
Discharge Structure
3
The cooling water that does not evaporate or drift from the towers would be routed back to the 4
cooling-tower basin at the base of each tower. The closed-cycle cooling-water loop is 5
completed when cooled water is pumped from the cooling-tower basins back to the condenser 6
and heat exchangers. Evaporation of water from the cooling tower increases the concentration 7
of dissolved solids in the cooling-water system. To limit the concentration of dissolved solids, a 8
portion of the cooling water would be removed as blowdown and replaced with makeup water. 9
Some waste heat would be removed from the cooling system with the blowdown water. 10
Blowdown water represents 98 percent of effluent discharged to Ninety-Nine Islands Reservoir 11
via the diffuser on the upstream side of the dam. The average blowdown temperature is 12
expected to be 91°F and the maximum blowdown temperature was estimated to be 95°F. Duke 13
estimated the normal CWS blowdown flow rate to be 8087 gpm for both units (maximum 14
28,023 gpm) and the normal SWS blowdown flow rate to be 121 gpm for both units (maximum 15
410 gpm). Blowdown from the SWS serves as makeup water for the CWS so it does not 16
contribute to the total volume of water discharged to the reservoir. Discharge from other plant 17
systems including the demineralized water treatment system, fire protection system, and others 18
would be collected in the wastewater retention basin and discharged with the blowdown yielding 19
discharge to the reservoir of 8216 gpm (18 cfs) under normal operating conditions and 20
maximum discharge to the reservoir of 28,778 gpm (64 cfs) (Duke 2009b). 21
Site Layout and Plant Description
Draft NUREG-2111 3-44 December 2011
Power Transmission System
1
During plant operation, there are potential continuing impacts from electric fields, noise, and 2
corridor maintenance. Duke has established procedures for transmission system inspection 3
and maintenance that include aerial inspections two times per year. Transmission corridors 4
would be maintained to control vegetation using herbicides or mechanical cutting and removal 5
methods where herbicides cannot be applied (Duke 2009c). Routine maintenance activities 6
such as right-of-way clearing, structure repair and replacement, and other activities are also 7
expected to be consistent with all applicable local, State, and Federal guidelines. 8
Emergency Diesel Generators
9
Proposed Units 1 and 2 would each have two 4000-kW standby generators located in the 10
AP1000 diesel-generator building and two 35-kW ancillary diesel generators located in the 11
AP1000 annex building. The back-up fire pumps for each unit also are diesel-powered. One 12
750-kW diesel generator would provide back-up power to the Lee Nuclear Station technical 13
support center. Combustion emissions from these diesel generators and secondary fire pumps 14
would be released to the atmosphere only during emergency operations and periodic testing. 15
Emissions include particulates, sulfur oxides, carbon monoxide, hydrocarbons, nitrogen oxides, 16
and carbon dioxide (Duke 2009c). Gaseous releases would need to comply with levels 17
permitted by the South Carolina Department of Health and Environmental Control (SCDHEC). 18