ML20080H570
| ML20080H570 | |
| Person / Time | |
|---|---|
| Site: | Harris  |
| Issue date: | 09/14/1983 |
| From: | Johnston W, Johnston W Office of Nuclear Reactor Regulation |
| To: | Novak T Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20079F427 | List:
|
| References | |
| FOIA-84-35 NUDOCS 8309220302 | |
| Download: ML20080H570 (24) | |
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UNITED F(ATES 8
NUCLEAR REGULA~iORY COMMISSION c.
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j.9 WASHINGTON. D. G. 20556
- )f SEP 141983 Docket Nos. 50-400/50-401 MEMORANDUM FOR:
Thomas M. Novak, Assistant Director for Licensing, DL FROM:
William V. Johnston, Assistant Director Materials, Chemical & Environmental Technology, DE
SUBJECT:
HYDROLOGIC ENGINEERING INPUT N THE SHEARON HARRIS SER Plant Name:
Shearon Harris Nuclear Power Plant Units 1 and 2 Licensing Stage:
OL Responsible Branch:
Licensing Branch No. 3; Bart Buckley, PM Requested Completion Date:
Sept _ ember 1, 1983 Enclosed is our Hydrologic Engineering input to the Shearon Harris SER.
This input was prepared by R. Gonzales who can be reached on extension 28018.
Section 2.4 of this input contains an open item concerning the potential for intense Scal precipitation to flood safety related structures.
We~ prepared questi or the applicant on the issue on August 9, 1983.
Thesejuest' ions were et.quently transmitted by you to the applicant on August 17, 1983.
-In addition, a technical specification defining procedures to assure that sediment deposition does not adversely affect the emergency water supply, is required.
This technical specification will be reviewed at the appropriate time prior to plant operation.
This SER input has been typed on IBM System 6 and stored on a diskette which is available from Wilma Swick (X27972).
QP.
William V. Johns sistant Director Materials, Chemical & Environmental Technology Division of Engineering
Enclosure:
As stated cc:
See next page 736 9 A2 o 30;2.%. $.
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HYDROLOGIC ENGINEERING INPUT TO THE SHEARON HARRIS SER UNITS 1 & 2 DOCKET NUMBERS 50-400/401 2.4 Hydrologic Engineering The staff.has reviewed the hydrologic engineering aspects of the applicant's design, design criteria, and design bases for safety related facilities at Harris.
The acceptance criteria used as a basis for staff evaluations are set forth in SRP 2.4-1 through 2.4-14 (NUREG-0800).
These acceptance criteria include the applicable GDC reactor site criteria (10 CFR 100), an'd standards for protection against radiation (10 CFR 20, Appendix B, Table II).
Guidelines for implementation of the requirements of.the acceptance criteria are provided
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in RGs, ANSI standards, and Branch Technical Positions (BTPs) identified in SRP 2.4-1 through 2.4-14.
Conformance to the acceptance criteria provides the bases for concluding that the site and facilities meet the requirements of 10 CFR 20, 50, and 100 with respect to hydrologic engineering.
2.4.1 Hydrologic Description Shearon Harris is located in east-central North Carolina, about 16 miles southwest of Raleigh, NC and about 7.5 miles north of the confluence of the-l Cape Fear River and Buckhorn Creek.
As shown on Figure'2.6,'the plant is on a peninsula of a reservoir the applicant created by constructing a dam on.
Buckhorn Creek about 2.5 miles north of its confluence with the Cape Fear River.
This dam is identified as the main dam on Figure 2.6.
The reservoir behind the main dam, which will be used for cooling tower makeup requirements, has a surface area of about 4100 acres.
In addition to the main dam, an I
auxiliary das has been constructed on an arm of the main reservoir.
The reservoir behind the auxiliary dam will be used as the primary source of emergency cooling water.
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~2-Plant grade and the tops of the main and auxiliary. dams are at el 260 ft above mean sea level (ms1).
The reservoir behind the main dam will have a normal 2
max'inum pool elevation of 220 ft as1.
Its drainage area is 71.0 mi.
The water level in the auxiliary reservoir will be maintained between 250 ft asl 2
. and 252 ft as1. The drainage area behind the auxiliary dam is 2.43 mi,
At its confluence with the Cape Fear River, Buckhorn Creek drains a watershed' 2
area of about 79.5 mi.
The point of confluence is at Cape Fear River Mile 192.
The Cape Fear River at Buckhorn Das just upstream of its junction 2
with Buckhorn Creek has a drainage area of 3196 mi.
The Deep and Haw Rivers join together to form the Cape Fear River about 6 miles upstream from Buckhorn l
Dam.- The Cape Fear River discharges into the Atlantic Ocean 28 miles down-stream of Wilmington, NC, at Cape Fear.
Th'e estimated average flow for Buckhorn Creek over 55 years (1924-1978) was about 88 cfs.
Likewise, the estimated average flow in the Cape Fear River at Buckhorn Dam over 54 years (1925-1978) was about 3119 cfs.
There are no known surface water users of Buckhorn Creek within the reservcIir area or downstream of the main dam.
The nearest downstream potable water supply intake on the Cape Fear R'ver is at Lillington, NC, about 12 miles downstream of Buckhorn Dam.
Three other municipalities (Dunn, Fayetteville,,
and Wilmington) draw water from the Cape Fear River further downstream of the plant.
There are also 10 industrial water supply intakes, including the applicant's Brunswick Plant, on the Cape Fear River downstream of Shearon ~
Harris.
The nearest industrial intake is at Fayetteville.
The bedrock units of the Sanford Formation of the Newark Group (Triassic) provide the groundwater source in the site vicinity.
The prioary permeability of this Triassic aquifer is very low; however, fractures provide a secondary permeability.
Fractures are common to a depth of about 100 ft, but below that depth they become tighter.
Below about 400 ft, the fractures are closed and sealed to groundwater flow.
Holly Springs and Fuquay-Varina are the nearest 9
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. communities using groundwater for public water supply.
Holly Springs, 7 miles east of the plant, has two wells supplying a total of about 40,000 gpd.
Fuquay-Varina, 10 miles southeast of the plant, has eight wells supplying about 400,000 gpd.
None of these 10 wells draws water from the Triassic aquifer underlying the plant.
Besides thesa 10 wells, there are 21 other public wells-within 10 miles of the plant.
In addition, there are several houses in Corinth, about 5 miles southwest, that have individual wells drawing water from the Triassic aquifer. The production rates of these wells range from 0.5 to 13 gps.
The applicant has provided hydrologic descriptions of the plant site and 4
vicinity.
The staff has reviewed the applicant's information in accordance with procedures in SRP 2.4.1 and'2.4.2.
The staff concludes that the require-ments of GDC 2 and of 10 CFR Part 100, with respect to general hydrologic descriptions, have been met.
2.4.2 Floods 2.4.2.1 Flood Design Considerations Four potential sources of site flooding were considered by the applicant:
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(1) intense local precipitation on the plant island (2) flooding on Buckhorn Creek and tributaries l
(3) dam failures (4) hurricane-induced wind wave activity Based upon its review of the material presented by the applicant in accordance with the procedures in SRP 2.4.2, the staff concludes that these four flooding sources are the only credible sources of potential flooding at the plant site.
2.4.2.2 Effect of Local Intense Precipitation f
Safety-related structures, systems, and components are flood protected to at least 261 ft asl and no structure has any access openings below this elevation.
Because plant grade elevation is 260 ft asl, water could pond up to 1 ft deep on the plant island before any structures or equipment would be affected.
In addition, a site drainage system consisting of inlet structures and under-ground piping has been provided.
Open ditches and underground pipes are also used along the peripheral areas of the plant island.
The drainage system drains the site to the main reservoir or to the auxiliary reservoir via the emergency service water intake and discharge cl.annels.
The drainage system is designed for a storm intensity of 5'in."per hour.
This is less than the probable maximum precipitation (PMP) for the site, so during a PMF event some water could pond on the site.
PHP is the estimated depth of_ precipitation (rainfall) for which there is virtually no risk of exceeding.
At Harris, the PMP values used by the
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applicant for durations of 6,12, 24, and 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> were 30.0 in., 32.7 in.,
35.0 in., and 38.1 in., respectively.
The applicant estimated that the greatest rainfall intensity would occur during the first hour and would then,
decrease with time.
The following tabulation shows this intensity for the first 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />s:
Duration PMP intensity (hrs)
(in./hr) 1 14.7 2
4.5 3
3.3 4
2.7 5
2.4 6
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' This shows that, during the first hour of the PMP, a total of 14.7 in would fall'on the plant island. The site drainage system is designed for a storm intensity of 5 in. per-hour; therefore, the difference (or 9.7 in.) would pond on the plant island (assuming that no water drains away).
In the FSAR the applicant stated that even in the event of complete blockage of the storm drainage system at the time of the PMP, the plant island is capable of being drained by overland flow on the open roads and ground surface directly to the main reservoir or the emergency service water intake and discharge channels.
At the request of the staff, the applicant furnished a site grading plan.
This plan shows that plant site roads are elevated about a foot above the plant grade elevation of 260 ft as1; consequently, water could pond to at least elevation 261 ft asl before it would be drained by overland flow.
Because exterior
' entrances to some safety-related structure's' are also at elevation 261 ft asl, water could enter these structures.
The staff has requested the applicant to reevaluate the site grading plan and modify it to assure that flood water from a PMP does not enter safety related structures.
The staff has also requested that in determining the magnitude and emporal'.
distribution of PMP, the applicant use the most recent National Weather Service publications as follows:
Hydrometeorological Report No. 51, " Probable Maximum Precipitation Estimates - United States East of the 105th Meridian", June 1978; and Hydrometeorological Report No. 52, " Application of Probable Maximum Preci-pitation Estimates - United States East of the 105th Meridian", August 1982.
In discussing the effects of local intense precipitation on roofs of safety related buildings,.the applicant stated that, with the exception of the emer-gency service water intake structure, screen structure and discharge structure, all safety related buildings have curbs around their perimeters that would allow roof ponding in the event that all roof drains were plugged.
These curbs are a maximum of one ft high; therefore, water would only pond to this depth before it would begin to overflow.
The applicant estimated the total depth to which water would pond during a PMP event would be about 15 in. except in l
some areas of the Reactor Auxiliary Building which are surrounded by higher walls.
In these areas the applicant estir..-tea that water would pond to a depth of about 2.5 feet.
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. There are other safety related structures where water could pond to an even greater depth.
The Tank Buildings, which house several storage tanks, have areas without roofs that are surrounded by 25 ft high walls; consequently, water will pond on the floors of these open areas.
The applicant estimated s
that water could pond to a depth of 23.4 ft in these areas.
The applicant has stated that the floors of the unroofed areas of the Tank Buildings and the roofs of all safety related buildings where water accumulates are strong enough to withstand the ponding loads in addition to other dead and live loads that can reasonably be expected to occur coincident with the PMP.
The staff has reviewed the applicant's analysis using the procedures described in SRP Section 2.4.2.
Based on this review', the staff concludes that during a PMP event, ponded water levels on roofs and floors of safety related structures will remain at or below the levels determined by the applicant.
However, before the staff can determine whether the plant' meets the requirements of GDC-2 with respect to flooding by intense local precipitation, it must review ' nd concur a
with the site grading plan.
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2.4.3 Probable Maximum Flood on Streams and Rivers i
The probable maximum flood (PMF) is defined as the hypothetical precipitation-induced flood that is considered to be the most severe reasonable possible.
For Shearon Harris, the applicant estimated th'e PMF for the drainage areas'of
-both the auxiliary das and the main dam.
For the auxiliary dam, the applicant determined the PMF that would result from the PMP.occuring over the 2.43-mi2' drainage area upstream of the dam.
This PMF was then routed through the auxiliary dam spillway using appropriate reservoir-storage spillway-discharge relationships.
This analysis showed that a PMF with a peak inflow of 8270 cfs would result in a maximum stillwater level of 256.0 ft asl in the auxiliary reservoir and a peak outflow through the spillway of 5030 cfs.
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. For the maiii dam, a similar procedure was used to determine the PMF, except that'the PMP, which was assumed to occur over the 71-mi2 drainage area up-streen of the main dam, was reduced by 10% to account for irregularities in the shape of the basin and for the improbability that the PMP would be centered exactly over the drainage area.
This analysis resulted in a PMF with a pean inflow of about 162,000 cfs.
In routing this PMF through the main das, the applicant' assumed that 5' days before the start of the PMF, a less severe ante-i cedent storm would have occurred. This antecendent storm, equal to 50% of the PMF, was routed through the main dam spillway.
Five days after the start of this routing, the calculated water level in the main reservoir was at el 225.2 ft as1.
This elevation, which is 5.2 ft higher than the normal water level, uns used as the beginning reservoir elevation at the start of the PMF main reservoir routing.
The peak discharg'e' through the main das spillway during the PMF was calculated to be 14,190 cfs, with a corresponding stillwater surface elevation in the reservoir of 238.9 ft as1.
i The applicant calculated the effects of coincident wind wave activit'ies on the PMF stillwater levels noted above using U.S. Army Corps of Engineers (COE) pro-
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cedures.
This analysis resulted in a maximum water level of 243.1 ft asl in the main reservoir and 258.0 ft ms1 in the auxiliary reservoir.
By com-parison, the elevations independently computed by the staff were slightly higherat243.3ftasland258.6ftaslinthemainreservoir\\andauxi-liary reservoir, respectively.
Based on this, the staff concludes that wind waves superimposed on PMF stillwater levels wi11 not result in unacceptably'
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high water levels because the tops of both the main dam and the auxiliary dam, at elevation 260 ft asl are higher than the maximum water levels computed by both the staff and the applicant.
As described above, the applicant reduced the PMP by 10% in estimating the PMF
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for the main dam.
The staff does not agree that this reduction is justified; however, because the top of the main dam is 16.7 ft higher than the maximum water level computed by the staff and 16.9 ft higher than the applicant's value,-the staff concludes that this margin provides more than adequate storage volume to contain the additional runoff that would result from 10%
more precipitation.
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'The applicant considered that a PMF on the Cape Fear River would have no effect on plant safety because of thL "10 ft difference in elevation between the top of the main dam and the riverbank.
The staff concurs with the appli-cant's appraisal of this issue.
However, there could be backwater effects of the PMF on the Cape Fear River through Buckhorn Creek on the downstream face of the main dam.
The applicant does not expect that any significant wind waves will be generated against the downstream face of the main dam because of the small fetch which severely limits the size of wind generated waves.
Any waves that do form, will not affect the integrity of the main das because the outer zone of the das is rock rather than earth.
During construction of the dam, the larger rocks from the rock zone were placed near the downstream face of the dam to reduce hand-ling of oversize material and to provide additional protection to the down-stream face of the dam.
At the CP stage, the staff reviewed the applicant's PMF analyses and the effects of coincident wind-wave activities.
The staff concurred then with -
the applicant's analyses and concluded that the two safety related dams will not be overtopped and the plant island will not be flooded during a PMF on the Buckhorn Creek drainage.
The staff has reviewed the FSAR. material presented by the applicant in accordance with procedures'de'scFibed in SRP 2.4.2 and 2.4.3.
Based on this review, the staff conclu' des that the plant meets,the guidelines of RG 1.59, " Design Basis Floods for Nuclear Power Plants", and the requirements of GDC 2 with respect to flooding from the Buckhorn Creek drainage. - In addition, the staff concludes that a PMF on the Cape Fear River will not affect the integrity of the main dam.
Thus, the plant meets the requirements of GDC-2 with respect to flooding from the Cape Fear River.
1 2.4.4 Potential Das Failures There are no existing dans or water control structures in the Buckhorn Creek drainage basin other than the main dam, auxiliary separating dike, and auxi-liary dam, which have been constructed specifically for Harris.
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-g-The applicant postulated failure of the auxiliary dam and analyzed its effect on the main dam, even though both dans are seismic Category I.
It was con-servatively assumed that the auxiliary dam would fail instantaneously and that the flood wave would travel downstream through Tom Jack Creek into the main reservoir without any attenuation in height or velocity.
This analysis showed that the water level in the main reservoir would only rise about 1.5 ft and that no significant woe action would result.
I Using the procedures described in SRP 2.4.4, the staff has reviewed the applicant's methods of analyzing the flooding effects of potential das failures.
The staff concurs that conservative procedures have been used and that potential dam failures pose no threat to safety-related structures
- or systems.
Thus, the staff concludes that the plant meets the requirements of GDC-2 and 10 CFR 100, Appendix A with respect to flooding by potential dam failures.
2.4.5 Probable Maxim a Surge and Seiche Flooding
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The probable maximum hurricane (PMH) could cause water level changes in both the auxiliary and main reservoirs.
However, because the plant is not located right on or near the coast, the only dynamic mechanism that can credibly be considered for producing high water levels is the probable max 1 mum wind asso-ciated with a PMH.
The maM aum wave runup was,, estimated by the applicant u, sing l
a 133-sph wina speed on normal water levels in the two reservoirs.
Because there is a-40-ft difference in elevation between the top of the main dam at el 260 ft asl and the normal vater level of 220 ft asl in the reservoir, I.
wave action on the main dam was not considered to be a problem.
On the auxi-liary reservoir, this difference is 8 feet (260 - 252 ft as1).
Thus, for this reservoir, the applicant did consider the effects of wave action during a PMH.
Using a wind speed of 133 mph directed toward the auxiliary dam, the applicant determined values of wave runup and wave setup using the COE Engineering Technical Letter No. 1110-2-221, November 29, 1976, and Shore Protection l
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P 10-1 Manual, 1977.
The values determined were 3.0 ft and 0.6 ft, respectively.
Adding these to a normal water level of 252 ft asl resulted in a maximum vater level of 255.6 ft asl, which is 4.4 ft below the top of dam.
Using similar procedures but assuming that the wind direction is toward the plant island, the applicant determined a wave runup of 2.2 ft and wind setup of 0.2 ft.
These values, added to the normal water level of 252.0 ft as1, resulted in a maximum water level of 254.4 ft asl, which is 5.6 ft below plant grade elevation of 260 ft as1. Both of these water levels are less than the PMF and wind wave elevationa computed by the staff and the applicant (see Section 2.4.3).
The staff used the procedures descibed. in SRP 2.4.5 to review the applicant's
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methods of analyzing surge and siiche flooding effects of a PMH.
Based on this review, the staff concledes that the plant meets the requirements of GDC 2 and 10 CFR 100 with respect to surge and seiche. flooding because the maximum water levels resulting from a c"u are less than the PMF levels for the plant.
2.4.6 Probable Maximum Tsunami Flooding Since Shearon-Harris is located 140 miles inland.from the Atlantic coast, no credible tsunami event could threaten the plant.
j 2.4.7 Ice Effects i
Because of the geographical location of Shearon Harris, ice formation is not expected to be severe enough to affect the operation of the plant.
As described in Section 2.3.1, the maximum ice thickness observed in the area is approximately 0.75 in.
Minimum average temperatures recorded at the Raleigh, NC airport for the months of December, January and February are 30.5*, 30.0* and j
31.1*F, respectively.
Water from the auxiliary reservoir flows to the emergency service water screening (ESWS) structure through the ESWI channel.
The auxiliary reservoir 4
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. level is maintained at a minimum elevation of 250 ft rsl by pumping from the main reservoir.
The ESWS structure is protected from ice entering the intake bays by means of a concrete baffle that extends below the auxiliary reservoir level to elevation 247.5 ft.
In addition, the ESWS structure has stationary and traveling screens to remove any ice fragments that do enter.
The inlet of the gravity pipes that take water from the ESWS structure to the emergency service water and cooling tower (ESW and CT) makeup water intake structure are located at elevation 235 ft asl which is 15 ft below the minimum operating level in the auxiliary reservoir.
The minimum water level in the main reservoir at which the plant will be shutdown is elevation 205.7 ft as1.
The emergency service water pumps take.
suction at ar. elevatior of 191 ft-8 in'. msf.
Thus even at the minimum operating level in the main reservoir, the water level is over 14 ft above the pump inlets.
Because of the location of Shearon Harris and because gravity pipe and pump inlets are located 15 and 14 ft below minimum operating water levels respec-tively, the staff concludes that any ice that forms in the auxiliary or mai,n f
reservoirs should not affect the safe operation of Shearon Harris.
To further
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assure this, the applicant has provided a plan to minimize ice formation.
Briefly, this plan consists of starting the emergency service' water pumps whenever the auxiliary reservoir water temperature drops below 35'F.
The heated water from pump operation will be disch'arged into the emergency serv' ice water discharge channel.
The formation of ice in the emergency service water l
intake channel will be prevented by the water flowing to the pumps.
As stated above, the suction inlets for all pumps are located more than 14 ft below the low water level.
Heated hoods will prevent ice buildup on the traveling screens, which will be run continuously if potential icing conditions are prevalent.
The staff has reviewed this plan and concurs that its implementa-tion will protect safety-related equipment during periods of extremely cold weather.
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-u-2.4.8 Cooling Water Canals and Reservoirs Cooling water canals and reservoirs related to safety consist of the main das and reservoir, auxiliary das and reservoir, auxiliary separating dike, emergency service water intake (ESWI) channel, emergency service water discharge (ESWD) channel and the auxiliary reservoir channel.
The hydraulic design of these structures, which are shown on figure 2.6, was determined to be adequate to supply cooling titer to a four unit plant, during the CP review.
Because two of the four units have been concelled, the staff concludes that the canals and reservoirs are more than adequate for a two unit
. plant.
i As described in section 2.4.3, the main and auxiliary dams will not be overtopped during a PNF.
However, to protect against potential erosion by wind waves in the reservoirs, the main dam has a 4 ft thick layer of riprap on the upstream face. The downstream face is protected as described in I
Section 2.4.3.
The upstream and downstream faces of the auxiliary dam and.
l the auxiliary separating dike are also protected by a 4 ft thick layer of I
riprap.
The riprap, which has been sized to obtain a dense well graded mass, is founded on a bedding of crushed rock graded to prevent movement of the bedding material into or through the riprap.
A description oft tests that were conducted to determine the suitability of the riprap is given in Section 2.5.6.3.4.
The ESWI channel, ESWD channel and the auxiliary reservoir channel do not have slope protection because the expected maximum velocity of 2 fps is considered
-to be less than the velocity which would cause scour of the channels.
As des-cribed in Section 2.5.6.5, the slopes of these channels have been determined by the staff to be stable under all anticipated loading conditions.
The staff has reviewed the information provided by the applicant, using procedures described in SRP 2.4 8.
Based on this review the staff concludes that safety-related canals and reservoirs. meet the requirements of GDC-2, l
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GDC-44 and 10 CFR 100 with respect to the r ability to provide an adequate i
supply of cooling water.
2.4.9 Channei Diversions There is no historical evidence of any diversion of Buckhorn Creek or the Cape Fear River.
Because of the steep topography adjacent to these streams future realignment or diversion is considered extremely remote.
Regardless of the availability of runoff to the main and auxiliary reservoirs, the safety of the plant will no<
t juopardized because a technical specification requires shutdown of the plant when water levels reach designated low points.
At these levels, which are described in Section 2.4.11.2, there will be sufficient cooling water available to safety shut'down"the plant.
The staff thus concludes that potential channel diversions, although extremely remote, present no safety-related hazard to the plant and that the requirements of 10 CFR Part 100 relative to channel diversions have been met.
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2.4.10 Flood Protection Requirements As described in Section 2.4.3, the staff determined maximum water levels of _,
258.6 ft asl in the auxiliary reservoir and 243.3 ft asi in the main reservoir.
Corresponding levels computed by the applicant were 258.0 and 243.1 ft asl respectively.
With the exception of the ESWI channel, the ESWD channel and the auxiliary reservoirs, which by design are located below these water levels, all safety-related. structures are flood protected to at least 261 ft ms1.
Because of their location above maximum water levels, safety-related structures do not require any flood protection from floods due to ponded water in the reservoirs.
In Section 2.4.2.2, the staff determined that local intense precipitation could pond on-site and enter safety-related structures. The applicant will I
be required to reevaluate site flooding and modify the site grading plan to assure that ponded water does not enter safety-related structures.
Resolutit,n of this issue will be addressed in a supplement to this SER.
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. 2.4.11 Cooling Water Supply 2.4.11.1 Normal Water Sypply Under normal operating conditions, the plant will be cooled using natural draft cooling towers.
Makeup water will be supplied to the cooling towers
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from the main reservoir and blowdown will be returned to the main reservoir. '
t Water losses from the cooling towers and the two reservoirs are to be made up from local natural runoff in the Buckhorn Creek drainage during operation of Unit 1.
For operation of Units 1 and 2, diversion of water from the Cape Fear River will be required.
Inordertodeterminetheeffectsofl'owf5owsonnormalplantoperation,the applicant performed several reservoir operation simulation studies.
For a one 4
unit plant operation, no make-up capability from the Cape Fear Rive'r was assumed.
For a two unit plant operation, it was assumed that the Cape Fear River would be used to augme,nt Buckhorn Creek natural inflow.
In both cases, forced svapo-ration water losses from the cooling towers were based on a plant load factor i
of 75 %.
Streamflow records are available for Buckhorn Creek for only_ a seven year period between 1973 and 1981.
Because short streamflow records can result in frequency determinations that are relatively unreliable, the applicant synthe-sized a long term record for Buckhorn Creek by conducting a frequency corre-lation study using streamflow data from nearby streams with similar hydrologic characteristics. This study showed that the recorded Buckhorn Creek flows for 1973 to 1981 were slightly less than the flows estimated for the same period using the synthesized record.
Thus, it was considered that using the actual 1973 to 1981 record in a reservoir operation study to simulate average flow conditions, would be conservative.
For the one unit operation simulation, the main reservoir water level was found to fluctuate over a range of 5.5 ft during the seven year period.
The minimum and maximum water levels were 216.3 ft as1. and 221.8 ft ms1 respectively; and the average reservoir level was 219.4 ft as1.
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'The staff has reviewed the applicant's analyses and agrees th'at using the recorded short term streamflow data from Buckhorn Creek in the reservoir simu-lation study, instead of the synthesized record, is conservative.
The staff considers the assumptica of a 75% load factor during the driest and probably hottest months to be unconservative.
However, increasing the load factor to 100% would only increase the maximum drawdown by less than 1 foot.
In addition to performing a reservoir operation for average conditions, the applicant also considered an extreme drought condition having an exceedence interval of 100 years.
The minimum starting reservoir level at the beginning of the drought period was assumed to be the lowest level determined during the 7 year normal flow period (el 216.3 ft as1).
The minimum water level determined from the 100 year drought analysis was'el E11.0 ft as1.
The applicant also performed a simulation study using historical measured flows during the period of May 1980 to May 1982.
This period represented the.most critical period for low flow in Buckhorn Creek.
As with the 100 year drought simulation the applicant used el 216.3 ft asl as the starting elevation for the reservoir.
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The minimum reservoir water level determined for this critical two year per.iod was el 209.4 ft asl which is lower than that determined for the 100 year drought simulation.
The staff has reviewed the applicant's analyses for a one un d plant operation and concludes that normal inflow from Buckhorn Creek is sufficient for a one l
unit operation without makeup from the Cape Fear River.
The staff also
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concludes that the reservoir level would not fall below a minimum operating ele-vation of 205.7 ft.ms1 (See Section 2.4.11.2) except during the occurrence of an unusually severe drought (more severe than the drought of record) coupled with l
high power demand.
I The applicant's analysis for two units under average conditions is similar to i
that performed for one unit operation except that the evaporation from two units at 75% load was used to determine water losses and pumping from the Cape Fear River was used to augment Buckhorn Creek natural inflow.
The seven year streamflow record period that was used for the one unit study was
.also used for the two unit study although Cape Fear River flows for that period,
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-were slightly above average.
The effect of the above average flows on the simulation is minor, however, because the makeup pumps withdraw only a small percentage of the water that is actually available.
Pumping from the Cape Fear River was assumed to be limited as specified in the applicant's NPDES permit so as not to exceed 25% of the river flow nor reduce the river flow I
to below 600 cfs as measured at the Lillington gage.
The maximum pumping capacity assumed was 300 cfs.
For the two unit operation simulation, the main reservoir water level was found to fluctuate over a range of 4.2 ft during the seven year period.
The minimum and maximum water levels were el 217.7 ft asl and el 221.9 ft asi respectively.
The mean inflow and outflow rates were 90 cfs and 48 cfs, respectively.
To determine the maximum expected drawdown during a coincident 100 year drcught in both Buckhorn Creek and the Cape Fear River, the applicant presented the analysis for a four unit operation at 100% load factor.
The lowest reservoir level determined from this analysis was el 205.7 ft as1.
If the water level in.the main reservoir should drop to this elevation during operation, the ".
plant will be shut down according to procedures described in a technical specification.
This technical specification will also define the average water temperature and the level in the auxiliary reservoir at which the plant will be shut down. The staff will review this technical specification prior to plant operation.
The staff has reviewed the applicant's analyses for a two unit plant operatica ar.d concludes that the water supply including the Cape Fear River Makeup System l
is adequate for a two unit plant operation.
The staff further concludes that reservoir drawdown due to severe droughts for both a one and two unit plant operation will not unduly restrict the availability of cooling water for normal operation as required by GDC-44.
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' 2.4.11.2 Emergency Water Supply
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The prefered source of emergency cooling water if the nonsafety-related cooling towers are unavailable is the seismic Category I auxiliary reservoir, which is located on an arm of the main reservoir adjacent to the plant (see Figure 2.6).
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The main reservoir, which is also seismic Category I, provides a backup source of emergency cooling water.
5 Under emergency conditions, the service water supply would be switched from the cooling towers to the emergency service water pumps, which would take suction from the auxiliary reservoir via the ESWI channel.
Heated water would be discharged back to the auxiliary reservoir through the ESWD channel.
Valving is provided so that suction can be switched from the auxiliary reservoir to the main reservoir if necessary.
In this cooling mode, heated water would also be returned to the auxiliary reservoir via the ESWD channel but would return to the main reservoir by flowing through the auxil'iary das spillway.
The applicant analyzed the ability of the auxiliary reservoir to provide a 30-day supply of cooling water for the plant by postulating a loss-of-coolant accident (LOCA) in one unit and simultaneous shutdown of the bemaining three.
l units.
(Note that since this analysis was performed, two of the four units l
were cancelled).
This analysis resulted in a ' maximum service water inlet ~
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' temperature of 91.5'F, assuming the most severe meteorological conditions of record. This temperature is 3.5'F lower than the 95'F design-basis temper-ature'of the service water system heat exchangers.
The applicant's analysis also showed a maximum 30-day water loss of 286 acre-ft in the auxiliary reser-voir. At a full pond elevation of 250 ft as1, the auxiliary reservoir contains about 4400 acre-ft.
Thus after 30-days, approximately 4114 acre-ft of water remain in the reservoir.
Based on this analysis the applicant concluded that the plant meets the. suggested criteria of RG 1.27, " Ultimate Heat Sink for Nuclear Power Plants".
j j As stated above, the applicant's analysis assumed that Shearon Harris consisted of four units.
Because two of the four units originally planned have been can-celled, the applicant concluded that for an accident in one unit and shutdown of the other, the maximum temperature would be less than the 91.5'F determined for a four-unit plant.
At the CP stage, the staff concluded that the auxiliary reservoir would have sufficient capacity to provide cooling water for four units for the 30-day period suggested in RG 1.27.. The staff has reviewed the material presented in the FSAR in accordance with procedures described in SRP 2.4.11 and concludes that there is no information that would result in a change in that earlier conclusion (that the auxiliary reservoir is, capable of supplying a minimum of
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30 days of emergency cooling water to the plant at or below the design-basis temperature), especially because the plant will only have two units operating.
The staff, therefore, concludes that the plant meets the requirements of GDC-44 with respect to thermal aspects of the heat transfer system.
Because plant site drainage, including overland runoff, flows into heESWh and ESWD channels, there is a potential for sediment to build up in these channels, and in the auxiliary reservoir channel and the auxiliary reservoir, especially.while heavy construction is still in progress.
The applicant has.
furnished cross-sectional and profile data for the channels. " These data show very little sediment build up except in the ESWD channel where as much_
as 3.5 ft of sediment has accumulated close to the discharge structure.
The
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staff however, expects that this sediment will not accumulate once the plant j
is in operation and there is flow through the channel.
In order to preclude sediment from building up to an unacceptable level during L
operation, the applicant has committed to monitor the channels for sediment buildup in accordance with the precedures of RG 1.127, " Inspection of Water-Control Structures Associated with Nuclear Power Plants, Revision 1".
Details of the monitoring program have not been provided; however, the details which will deH ne the depth of which sediment will be allowed to accumulate before l
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19-removal is necessary and a procedure for removal will be included in a Technical Specification which will be required by the staff at the appropriate stage of staff review prior to plant operation.
2.4.12 Groundwater The overburden in the plant area consists of up to more tiian 15 ft of dense, low permeability, clayey soils and saprolite.
Below the overburden are the bedrock units of the Sanford Formation of the Newark Group (Triassic), which are the sources of groundwater in the site vicinity.
The Triassic rocks consist of claystone, shale, siltstone, conglomerate, and fanglomerate.
Thin diabase dikes are found intruded in the Triassic rocks.
Even though
. the primary permeability of the Triassic r~o'cks is very low, secondary permeability is provided by fractures that are filled with water below the water table.
These fractures are common to about 100 ft in depth, becoming less prevalent below that.
The fractures are closed and sealed to water flow below about 400 ft.
Recharge to the Triassic rock aquifer by percolation of water from the surface is slow and controlled by the location of joints and fractures. The larger reserves of groundwater are found near the diabase dikes.
In the vicinity of the plant site, groundwater supplies have been developed.neaiseveral small dikes for plant construction use.
The applicant has installed a total of 15 small-capacity wells, which yield a total with~drawal of about 450 gpm.
The' applicant does not intend to use groundwater for plant operation.
Groundwater use will cease after the plant's potable water system becomes operational.
The general groundwater movement in the plant area before plant construction began was to the southeast.
Because of pumping during construction, water levels have been changed significantly, but the general direction of movement is still toward the southeast.
The groundwater table gradient varies considerably at the site, but the maximum gradient is about 0.06 ft/ft.
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During the CP review, the staff concluded that the design-basis groundwater level of-251 ft asl was conservative and acceptable and that the auxiliary reservoir water surface elevation, which will be maintained between 250 and 252 ft as1, would not affect groundwater levels at the plant.
Since that time, Units 3 and 4 were cancelled.
Due to this cancellation, the reactor auxiliary buildings, the containment buildings and the tank buildings for Units 3 and 4 will not be built and a 400 ft long retaining wall west of the fuel handling building will be constructed.
The applicant has not indicated whether a full groundwater hydrostatic level of 251 ft asl will be used for design of the retaining wall.
Consequently, the staff is unable to complete its review at this time.
. The applicant has not classified.the retaining wall as a seismic Category I structure.
However, as stated in Section 2.5.4, the staff will review the retairiing wall as a seismic Category I structure because a postulated failure could affect the safety of the fuel handling building. The stability analysis of the wall, which was recently submitted by the applicant, will be evaluated and addressed by the staff in a supplement to this SER.
Details regarding the number of existing groundwater users are provided in Section 2.4.2 of this SER.
Because of low population density in the plant vicinityandlowwellyields,thenumberoffuturegroundwatehusersisnot
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expected to increase significantly. The low yields are a result of low permeability and limited storage capacity in the proximity of diabase dikes'.
The applicant has provided descriptions of regional and local groundwater aquifers, regional and local groundwater use, hydrostatic design levels, and construction monitoring programs. The staff has reviewed the applicant's information in accordance with the procedures in SRP 2.4.12 and concludes that the applicant's descriptiens and analyses are sufficient to meet the requirements of 10 CFR 100, 10 CFR 100 Appendix A, and GDC 2, except for the retaining wall, which will be constructed to replace several seismic category I structures which will not be built because two units of the Shearon Harris plant have been cancelled.
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' 2.4.13 Accidental Release of Liquid Effluents SRP 2.4.13 sets forth criteria and procedures for the analysis of accidental releases of liquid effluents in groundwater and surface water.
Using these, the staff analyzed a postulated failure of the waste evaporator concentrate tank to determine the potential for radioactive contamination of surface water and' groundwater supplies.
This tank was selected for analysis because it contains the highest potential concentration of release.
The waste evaporator concentrate tank, which is located in the waste processing building, was postulated to fail, spilling its contents on the floor.
The 1
4000 gal contained in the tank were then assumed to instantaneously and
.nonsechanistically leak through the building floor and/or walls into th'e surrounding groundwater where they would be dispersed and transported downgradient in a south-southeast direction about 3000 ft to the Thomas Creek arm of the main reservoir.
There are no water supply wells along this route, which is entirely within the site boundaries, nor are there apt to.be in the future.
Inaddition,-theapplicanthascommittedtousingnogroundwater; after construction is completed.
Because of the fractured nature of the Triassic rock formation, the staff conservativelyassumedthattheaccidentalreleasewould. move (theentire
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2000 ft to the reservoir through a fracture, which the applicant estimated to be 50 times more permeable than the Triassic rock itself.
Based on field t'est data, the applicant determined the permeability.of the Triassic rock to be about 10 ft per year.
Thus, the permeability of the fractures was estimated I
to be about 500 ft per year.
The staff concurs in the applicant's value for permeability and in the value of the groundwater gradient, which was determined to be 0.06 ft/ft.
The latter is based on field measurements made before con-struction.
The staff concludes that the preconstruction groundwater table L
configuration will also be representative during operation, after the applicant i-ceases pumping from the construction water supply wells.
The staff concurs in the applicant's assumed value of 0.30 for the porosity of the fracture materials.
Using a conservative value of 0.05 for effective porosity (obtained from the literature for similar materials) and the applicant's values of permeability
a M gradient, the staff determined that as a result of radioactive decay,
- oispersion, and sorption, concentrations of all nuclides attributable to a postulated failure of the waste evaporator concentrate tank would be well below 10 CFR 20, Appendix B concentrations at the point where they would enter the Thomas Creek are of the main reservoir.
The staff therefore concludes, based on the guidance of SRP 2.4.12 and 2.4.13, that the plant meets the requirements of 10 CFR 100 with respect to potential accident releases of liquid radioactive affluents.-
2.4.14 Technical Specifications and Emergency Operation Requirement
.The applicant has committed to establishing ~a program to monitor sediment build-up in channels which are required for emergency plant shutdown.
Details
, of this sediment monitoring program will b,e included in the applicant's technical specifications. The applicant ha's submitted a technical specifica-tion which defines reservoir levels at which the plant will be shut'down.
This technical spe'cification will be reviewed by the staff prior to plant operation.
2.4.15 Conclusions According to procedures outlined in the SRP,*the' staff has rev,iewed the
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design of the Shearon Harris plant in regard to hydrologically and hydraulically-related plant safety features. On the oasis of this review,'
the staff concludes that any large-scale river flooding, either naturally occurring or seismically induced, poses no threat to the safe operation of
-the plant or the integrity of the site.
The staff, however, is unable to conclude that local flooding will not threaten the plant.
The staff concludes that Shearon Harris meets the requirements of GDC 2 with respect to potential flood hazards except for the outstanding item concerning local flooding.
The staff has analyzed the availability of water for normal cooling purposes during diminished flow periods and concludes that adequate storage is present in the main reservoir to maintain safe plant operation over any reasonable
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