ML19319C504

Revised Hydrologic Engineering Summary Input for SER

ML19319C504
Person / Time
Site:	Davis Besse
Issue date:	09/19/1975
From:	Schreiber D, Staley G Office of Nuclear Reactor Regulation
To:
Shared Package
ML19319C498	List: ML19319C490 ML19319C504
References
NUDOCS 8002190939
Download: ML19319C504 (14)

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• REVISED HYDROLOGIC ENGINEERING SU1 DIARY DAVIS-BESSE NUCLEAR POWER STATION UNIT NO. 1 DOCKET No. 50-346 2.4 Hydrologic Engineering 2.4.1 Hydrologic Description - The site for Davis-Besse Nuclear Power Station (DBNPS) is located on the Southwestern shore of Lake Erie.

The major station structures are located approximately in the center of the site area, 3000 feet from the shoreline. All elevations are referenced to the International Great Lakes Datum (IGLD), which was established in 1955 by the U. S. Department of Ccemerce. The low water datum (LWD) for Lake Erie is 568.6 feet ICLD. The original topography of the site was relatively flat with elevations varying from 568.6 feet IGLD to about 575 feet IGLD. The plant area is located on an existing slightly' elevated upland section and is separated from the lake by an adjacent marsh area and a narrow beach ridge between the marsh and lake.

Plant grade is to be 384 feet IGLD with entrance levels to plant structures at 585 feet IGLD. The southern site boundary borders the Toussaint River, which is approximately 3,000 feet from the major plant structures. A wave protection dike has been installed along the north and eastern side of the built-up plant area to an elevation of 591 feet IGLD. All surface water from these elevated areas will be collected and carried in storm drains to ditches that empty into either the narsh area or the Toussaint River.

An intake canal has been installed between the intake structure at the plant site and the beach ridge. The intake canal is connected to-Lake Erie with an eight foot diameter underground and underwater pipe that extends 3,000 feet out into the lake. This is the single water source

• Underlined portion indicates changed material for this revision.

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. of cooling water for the service water system and is utilized for both normal and emergency shutdown conditions. A Category I open forebay arca ahead of the intake structure serves as a reservoir for an insured nource of water in case of an extreme lowering of the lake due to meteorological conditions, or collapse of the intake canal or the submerg'ed pipes.

Lake Eric is the primary source of potable water in the area.

The five nearest lake users are located betueen 3.', and 12 miles from the station discharge.

The Sand Beach community, uith 122 residen:cs, is located along the beach ridge, commencing at the northern site boundary at the shoralina. Approximately 50 percent of these residences cbtain household unter for all purposes from beach wells located in the lahefront sand.

These walls are 3 to 6 feet deep, located 10-20 feet from the lake shorcifne and for all practical purposea would be considered surface water supplies.

2.4.2 Flooding - Several potential flood producing sources were investigated by the applicant. The potential sources include Lake Erie, the Toussaint River, and the site drainage in the vicinity of safety-related structures as follows:

a. Lake Erie - The applicant has investigated probable maximum stillwater lake levels based on record lake levels plus wind tides and transverse seich2.

The maximum lake icvel of 573.5 Ccet ICLD van recorded in June 1973. The applicant has calculated a maximum wind tide of 9.3 feet due to a probabic maximum tieteorological event (PMME) and using a procedure developed by l

~ Platzman (1). A probabic maximum transverse ceiche of one foot was used based on a recorded value of 0.8 foot in the western basin by Hunt (2). These values ucre added to a lake level of 573.4 feet ICLD (0.1 foot lower than record) to yield a maximum stillwater lake level of 583.7 feet ICLD, 0.3 feet Jower than the plant yard grade of 584.0 feet IGLD.

The applicant calculated a maximum uave height of 10.7 feet due to the PMME, however this uave will break of fshore due to limited depth of water. The top of the wave protection dike is based on a 8.5 foot wave generated landuard of the shoreline.

This wave will produce a runup of 6.6 feet on the 3 to 1 dihe slope.

This yields a maximum runup elevation of 590.3 feet IGLD, which is 0.7 feet belou the top of dike elevation of 591.0 feet IGLD.

The lahecide fa-of thm dike will be protected with a 3-foot layer of random placed angular quarry stone on a 6-inch layer of 2-inch minus granular material.

b. The Toussaint Riv'er emptics into Lake Erie southeast of the site.

The stream has a drainage area of about 143 square miles and an average slope of about two feet per mile. The stream is ungaged and there are no dana on it.

The lower six miles of the stream is much vider than the remainder and is controlled by the level of the Lahc Erie. The applicant has conservatively estimated the peak flow rate for the Probable Ma::imun Flood (FMF), using the Probable Maximum Pr,ccipitation (PMP), to be 78,500 cubic feet per second (cfs). The applicant conservatively assume? there would be no flow to the lake during the PHE and the maximum stage associated with this " dammed up" condition would be 579.0 feet IGLD.

c. Site Drainane - The applicant proposed that site drainage facilities be designed such that a local PNP uill not constitute a threat to the safety-related facilities.

The applicant has conservatively assumed that all site storm drainage systens are blocked and filled with vater at the start of a local PMP.

Runoff under this assumption vould reach 584.5 feet ICLD, which is 0.5 feet above the high point of all roads and grounds and 0.5 feet below the ficor grade of all cafety-related buildings. All Categcry I structures have a 2.5 foot parapet at the periphery of their roofs.

Those roofs that have penetrations, have a curb around the penetration and horizontal roof drains uith their invert at least 12 inches below the top of curb, in addition to the regular roof drainage system.

The horizontal drain pipes are designed to drain the local PMP should all the regular roof drains become clogged.

The staff has reviewed the applicants flood design considerations and conclude that all safety-related structures are safe from all flood potential up.to probable na:.:imum magnitude.

2.4.3 Ice Floodinz - The applicant has concluded that ice flooding of safety-related structures from either Lake Erie or the Toucsaint River will not present any hazards because of the distance between the plant site and relevant water bodies, and the freeboard between plant grade and the stillrater lake and river levels. He has also stated that even if the ice should reach the dikes on the north and cast side of the plant, they are designed to uith'atand the ice pressures. He concur with the applicants conclusions.

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2.4.4 Water Supply

,21 cooling water requirements are from Lake Erie.

The intake canal forebay is designed as seismic Category I, and will l

be used as a heat sink reservoir in the event of low water or an acci-dent. The applicant has used a procedure developed by Platzman (1) to determine the maximum wind tide fall at.the site due to a PM)E.

The maximum wind tide fall was calculated at Toledo. Since the Davis-Besse site is located about 80% of the way from the wind tide node (Point in lake whe;e no wind tide chango in lake level occurs) to Toledo, wind I

i tide variations at the Davis-Besse site were reduced by 20% from Toledo wind tides. This procedure gives a maximum wind tide drop with WSW winds of 9.3 feet. The maximum variation of record in the mean monthly I

level of Lake Erie is 1.2 feet below the LWD.

The applicant has used i

a value of 1.5 feet below the LUD as an antecedent condition to the

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above procedure. A transverse seiche causing an additional tide drop of 1.0 foot was also assu=ed. These lake level losses total 11.8 feet I

and give a minimum stillwater lake level of 556.8 feet ICLD. The applicant's analysis of low water conditions is acceptable and in the event the lake level drops below the minimum operating level of 562.0 feet IGLD. the plant can be brought to a saf e shutdown condition with the Seismic Category I Ultimate Heat Sink (UHS).

The applicant has estimated that the intake forebay, which is the seismic Category I ultimate heat sink, will have sufficient water and surface area to provide emergency cooling for 39 days at a temperature no greater than 130*F (maximum allowable plant return water temperature). The applicant used the METMIN (Ref. 3) generic transient heat program to analyze

-the forebay te=perature.s. The analyais assumes a seismic event, with f

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A the lake at elevation 562 feet IGLD, that blocks 2/3 of the portion of the intake canal that is not seismic Category I.

The remaining 1/3 of the water volume in the canal plus the volune in the seismic Category I forebay area was used as the initial watar volume for the analysis. The additional surface area in the failed portion of the intake canal was not used for heat transfer. The neolicant's use of the METMIL codel to analvee the UMS is not considered an acceptable precedure for the particular arrangement at Davis Besse 1.

The METMIN mo_ del i d n,tsaded grimarily for use_on_ phal. low, well mined ponds and eniv where the subsequent calculated. maxi _um_ temperatures are well below the raximum desien values.

It is not realistic or conservative trugpEDTilpf_j;hi_s_lUIS. si_nce appIgxistely_1/3 of the total water v.olume_is_in__the_2QQQ_f.ont._renh_o_f_theAt_ake canal, wh_ich is not efficient for heat transfer due to its long narrow geometry.

The staff has made independent analyses to determine the maximum return water temperature for a plant shutdown due to LOCA and simultaneous loss of 2/3 of the intake canal volume. Our analyses were based on the same parameters used by the applicant.

The results of these analyses indicate that the water in the forebay area will reach a peak tempera-ture of 123'F in about 4 days following plant shutdown for a LOCA.

The staff used several different codels

• .c determine the adequacy of the URS as follous:

(1) A revised HYETA (Ref. 3) program, (HYETA 2), was used to determine the extent of heat diffusion in the long narrow intake canal, as well as to determine a conservative value of the maximum 1

. temperatures at the plant intake. The results of this analysis showed that only 900 feet of the canal (from the end of the seismic Category I forebay) was effective for heat transfer and dissipation.

(2) Simplified stratified pond, mixed pond, and plug flow models were also used as a check on the reasonableness and conservatism of the HYETA 2 analysis.

The stratified pond model (STRAT) is the most realistic approach for the Davis-Basse pond.

This model computed a maximum temperature of about 121*F, 75 hours8.680556e-4 days <br />0.0208 hours <br />1.240079e-4 weeks <br />2.85375e-5 months <br /> after the LOCA.

Since the applicant has not provided sufficient documentation to sub-stantiate that the selected wind speed of 7.4 mph (for maximum pond temperature condition) is necessarily representative of the average wind speed associated with the meteorological data for the worst 30 day period, the staff has analyzed the UHS using a conservative wind speed of 5 mph.

Also, the staff had previously calculated maximum temperatures for the UHS in excess of the 130*F maximum allowable design value. We have since refined our analytical approach and the results now yield lower pend temperatures for the Davis-Besse 1 UHS which is designed to operate at fairly high temperatures. The results of our analyses with the 5 mph wind are maximum pond temperatures of 129*F with the HYETA 2 model and 127'F with the STRAT model.

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~ Based on our independent analyses, the staff has cone.'uded the Ultimate Heat Sink can provide an adequate supply of water at a tegperature less than 130*F, for at least 30 days. Provisions are also availab_1_e.

to obtain a supply of water past 30 days.

2.4.5 Groundwater - The major groundwater sources in the area are the water-bearing Silurian and Dovanonaan formations consisting of thick layers of limestone and dolomite. The major water bearing confined aquifer is between elevations 500 a d 555 feet (ICLD).

Well yields from the carbonate aquifer vary considerably in the vicinity of the site.

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Yields of 150-600 gallons per minute (gpm) can be obtained from wells in the region west of the site (toward Toledo), and as much as 500-1000 gym can be obtained from wells in the region east of the plant site (toward Port Clinton). Approximately 8 miles southwest of the site, the expected yield decreases to 50-200 gpm.

Water from wells in the site locality is used primarily for certain domestic and sanitary purposes, and farm irrigation.

In most instances, as a result of hardness, objectionable odor, and bitter taste, groundwater is not domestically used for washing, cooking or drinking.

In the vicinity of the site the groundwater gradient is about 2 feet per mile touard Lake Erie, which is generally the same slope of streams in the area.

The site is underlain by glaciolacustrine and till deposits (total thickness of approximately 17 feet) which overly the Tymochtee formation. These deposits basically consist of silty clay with very low permeability uhich has created at. artesian groundwater condition in the water-bearing Tymochtee and underlying carbonate bedrock formations.

The applicant hes estimated the average grounduater flow velocity to be about 5 feet per year, assuming the carbonate bedrock aquifer to be homogeneous and isotropic with an average permeability of 1 x 10-2 cm/sce and an average gradient of 2 feet per mile. There are 30 wells uithin a three mile radius of the site, 13 of which are no longer being used and the reamining 17 are only used intermittently for irrigation and sanitation purposes.

The applicant has concluded that the possibility of extensive contamination of the grou'ndwater aquifer is lov because:

(1) the redundant, safety features incorporated into the construction of 1

. the station; (2) the piezometric gradient and corresponding groundwater flow velocities are small at the present time; (3) the grounduater gradient is toward the lake and (4) there are no users betueen the site and the lake and the impervious surface deposits of predo=tnately clay composition vill retard the rate of flow to the aquifer and the dissolved radionuclides will react with the clay.

The staff made an independent analysis of the potential for groundwater contanination from an accidental liquid radcaste spill and concluded the following:

(1) The foundation of the raduaste building is at elevation 545 feet ICLU and the top of the confined aquifer, in the plant area, is at elevation 555 feet ICLD.

Consequently, any postulated accidental liquid raduaste spill from the radunste tanks in the ralwaste building would be leaked to the confined aquifer, if leakage uns possibic. The hydrostatic pressure associated uith the confined aquifer in the vicinity of the radwaste building would be about elevation 570 feet IGLD. This positive pressure on the radwaste building foundation would preclude leakage from the building into the confined aquifer, and in fact would induce leakage of grounduater into the radcaste building in the event of a scismic disturbance that could cause cracking of the struct.re.

(2) Additionally, the drounduater gradient is about ? feet per mile toward Lake Eric and there are no wcils between the plant site and Lake Eric that drau from the confined aquifer.

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. In the interest of conservatism, travel times and dilution factors were calculated for three points, as described below.

(1) The Lake Erie near field release point. The interface between Lake Erie and the confined aquifer was conservattvely assumed to be 3000 feet from the lake shore.

Consequently, grounduater (postulated to be contaninated) uould travel 6000 feet horizontally from the plant to Lake Erie and then vertically 30 feet to the lake surfaca.

The dilution factor and travel tiec are estimatad to be 2750 and 72 years respectively.

0 (2) The beach walls. The dilution factor of 5.5 n 10 and travel tiac of 72 years core based on the assumpttnn that ena.aata., voul.d have to travel f rom the radwaste building, through the confined aquifer to the Lake Eric interface (appronimately 6000 feet), then 3000 feet through Lake Eric to the beach wells, since the beach vells are not hydraulically connected to the confined aquifer.

(3) The Lake Eric Industrial Park.

This is a curface water source located about 3.6 miles east of the plant site.

The values for dilution factor and travel time frem our analysis are estimated to 6

be 9.8 n 10 and 72 years respectiv21y.

s The maximum probable static uater level is elevation 583.7 (see section 2.4).

The manimum water level due to unvc runup en the break vall is calculated to be elevation 590.5.

The station is protected along th'e' north, east, and partially on the south side by an earthen breakwall built up to elevation 591.0.

There will be no effective dynamic force applied on the critical structures

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associated with the maximum probable hydrodynamic water level and waves except the front vall of the intake structure which is designed for this loading condition. All seismic class I structures are designed for a maximum probable static water level of elevation 584.0.

2.4.6 Hydrologic Related Technical Specifications. The applicant's analysis of the UHS is based on a water level of 562.0 feet IGLD.

Should the lake level fall below this level, shutdown of the station will be required and described in the technical specifications.

2.4.7 Conclusions. We have reviewed the applicent's flood analysis for the Davis-3 esse Site, including taximum wind tide and wind waves on Lake Erie due to a PMME; PMF levels for the Toussaint River; ice effects on Lake Erie and the Toussaint River; and flood conditions at the site and on rooftops due to a local PMP and have concluded that the analyses and flood protection measures are acceptabic.

We have made an independent analysis of the potential for contamination of groundwater wells and surface water intakes in the vicinity of tha site and have concluded that in the event of an accidental liquid radwaste spill, leakage to the groundwater aquifer is improbable, however, even if leakage to the aquifer were to occur, effects at the nearest

. 0 water user would be negligibic.

We find the applicant's analysis of low water conditions at the site to be acceptable. Although extreme low lake levels would preclude the use of the intake crib as a source of water, the plant can be brought to a safe shutdown condition with the Seismic Category I UHS.

Our review and independent analyses pf the ultimate heat sink indicates that the present heat sink design and conditions of operation are adequate to provide plant cooling water at a temperature less than 130*F (maximum allowable for equipment design) for a 30 day period.

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• REFERE!!CES 1.

PJatzman, G.

U.,

A Procedure for Operational Prediction of !!ind Setup on Lake, Erie, Technical Report !!o.11, to the Environ =cntal Science Service Administration, the University of Chicago, Nov. 1967.

2.

Hunt, I. A., Winds, Wind Set-Ups and seiches on Lake Erie, U.S.

Lake Survey, Research Report 1-2, Corps of Engineers, January 1959.

3.

Generic Emergency CoolingiPond Analysis, U.S. Atonic Energy Co=nission, May 1972 - October 1972, Revised Program dated August 1975.

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