ML20005A430
| ML20005A430 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 06/25/1981 |
| From: | Counsil W NORTHEAST NUCLEAR ENERGY CO. |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TASK-02-03.A, TASK-2-3.A, TASK-RR A01452, A1452, NUDOCS 8106300317 | |
| Download: ML20005A430 (5) | |
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General Of f ces e 5elde,i Street, Berlin, Connecticut i
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Director of Nuclear Reactor Regulation 4
Attn:
Mr. Dennis M. Crutchfield, Chief
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Operating Reactors Branch #5 I
U. S. Nuclear Regulatory Commission Washington, D.C.
20555 Referencess (1)
D. C. Eisenhut letter to SEP Plant Licensees, dated January 14, ?. %.
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W. G. Counsil letter to D. G. Eisenhut, dated February 27, 1981.
Gentlemen:
Milistone Nuclear Power Station, Unit No. 1 SEP Topic II-3.A, Hydrologic Description As part of the redirection of the Systematic Evaluation Program, Reference (1), Northeast Nuclear Energy Company (NNECO) committed to develop Safety Assessment Reports (SAR's) for certain SEP topics which would be submitted for Staff review. NNECO detailed this commitment and provided a schedule for submittal of SAR's in Reference (2).
In accordane. with this commit-ment, NNECO hereby provides the Safety Assessment Report for SEP Topic II-3.A, Ilydrologic Description, which is included as Attachment 1.
We trust the Staff will appropriately use this information to develop a Safety Evaluation Report for this SEP topic.
Very truly yours, l
NORTIIEAST NUCLEAR ENERGY COMPANY 1
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( ( } l.it W. G. Counsil Senior Vice President 8106300 %
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Docket tio. 50-245 Safety Assessment Report SEP Topic II-3.A, Ilydrologic Description e
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June, 1981 l
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i Millstone Nuclear Power Station Unit No. 1 SEP Safety Assessment Report Topic II-3. As Hydrologic Description
1.0 INTRODUCTION
The objective of this topic is to assure that the designs of structures, systems, and components required for safo shutdown reflect consideration of appropriate hydrologic conditions and to identify deficiencies in designs and/or operations that could contribute to accidental radioactive releasen.
2.0 CRITERIA
' Standard Review Plan Section 2.4.1 states:
The description and elevations of safety-related structures, facilities, and accesses thereto should be sufficiently complete to allow evaluation of the impact of flood design bases. Site topographic maps must be of good quality and of sufficient scale to allow independent analysis of pre and post construction drainage patterns. All external plant structures and components should be identified on site maps.
Data on surface water users, location with respect to the site, type of use, and quantity of surface water used are required.
3.0 DISCUSSION The Millstone Nuclear Power Station is located on the north shore of Long Island Sound.
Tc the west is the site is Niantic Bay and to the east is Jordan Cove.
The public water supplies within a 20 mile radius of the site are identified in the Millstone Unit 3 PSAR, Figure 2.4.1-1, included here as Figure 1.
The nearest surface water supply is the New London Water Company's Lake Konomac, six miles north-northwest of the site.
No surface drainage from the site could af fect these reservoirs due to the distance involved, the surface conditions the expected groundwater gradicht from the reservoir areas to the site, and the generally impervious nature of the overbarden on and near the site.
The bedrock surface is exposed at the south end of the site, but covered with a dense glacial till at the north end.
Since both are quite impervious, precipitation does not sink into it readily and much of I.t runs off on the surface directly into Niantic Bay or Jordan Cove. Some surface water collects in depressions in the northern part of the site.
Normal tides at Millstone Point are semidiurnal wi.th a mean range of 2.7 feet and a spring range of 3.2 feet. Tides in excess of the mean high water occur on an average as follows:
in excess of 3 feet about once a year, in excess of 2 feet about five times a year, and in excess of 1 foot about 98 times a year. Mean high' water (MHW) at Millstone Point is 1.73 MSL.
Mean low j
water (MLW) is -0.97 feet MSL.
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e' observations of the water levels in the granite quarry at the site show that the water level in the quarry, before the existing discharge channel opened it to the ocean, typically were approximately 17 feet below the level of the adjacent Long Island Sound.
It is significant that this quarry was worked for over 100 years (1830 to 1960) at distances of as little as 200 feet from the waters of Long Island Sound without experiencing notable inflows of water.
These observations suggested, and it was further documented during the Unit 2 construction phase, that the permesbilities of the bedrock and the overlying soil mass are extremely low, with little or no groundwater or seawater seepage having occurred.
Both the basal till and the overlying ablation till (drif t) are relatively impervious. The ablation till soils are more pervious than the basal tills and occasiona'<ly exhibit partial stratification, including sporadic sand lenses; accordingly, the upper portions of the soil will transmit water more readily than the underlying (.ense basal tills. Groundwater levels appear to be subject to considerable seasonal fluctuations.
Localized perched groundwater conditions exiated because of the irregular distribution of ablation till materials with varying gradation and porosity. Shallow, ponded water existed in localized bedrock troughs.
s Bedrock outcrops to the north, northwest, and south of Unit 2 suggest that bedrock acts as a groundwater divide, isolating the soils of the top of Millstone point from soils further inlands accordingly, ground-water recharge would primarily be due to absorption of local precipitation, with the possible migration to the waters of the immediately adjacent Long Island Sound. As previously described, little or no groundwater is present in the crystalline bedrock, and virtus11y all of the groundwater movement is restricted to the soil overburden. Measurements taken during previous investigations in August 1969 showed average influx rates into 2 feet by 12 feet by 10 feet deep test pits of about 8 gallons per hour.
Within a five mile radius of the plant, public water supplies originate from ground sources, most of which are shallow wells and distant from the site.
The two nearest water wells are both owned by NNECO and are about three quarters of a mile northeast of the containment structure.
One is used as a backup for the fire protection system and the other is used to water a nearby baseball field and to supply a drinking fountain at the field. There are ridges in between the unit location and the wells which are undoubtedly underlaid by rock. They create a drainage divide, the groundwater flowing to the east and west and to the south.
It is highly improbable that water or chemicals accidentally released during operation or accident conditions to the site surface could reach the wells. The possibility of accidental waste discharges affecting public groundwater supplies is even more remate for wells serving those communities located beyond a 1 1/2 mile radius of the site since the Niantic River and Niantic Bay lie to the west and northwest of the site while the Jordan cove drainage basin is to the east of the site. Any accidental spillage in the soil or rock column at the site would be interrupted by these bodies of water and would prevent contamination of distant groundwater sources. ' Elevations exceeding those of the site and at surface' bedrock ridges preclude migration of contaminated groundwater to the north. Groundwater publically used within a three mile radius is I
presented below:
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Consnunity Distance of Well System Water System )wner Served From Site East Lyme Water Comm.
Niantic 2 miles E J. P. Thompson Waterford 2 miles NE East Lyme Water Conun.
East Lyme 3 miles NW (two wells)
In the event of any accidental releases 'of waste on the site outside the normal flow paths, investigation of possible diffusion in the groundwater will be made by detailed sampling of wells to detect the presence of specific isotopes. This will extend the normal periodic sampling program.
3.1 ASSOCIATED SEP MPICS o
ll-3.B Flooding Potential and Protection Requirements o
ll-37B.1 Capability of Operating Plant to Cope With DBF Conditions o
11-3-C Safety-Related Water Supply (UHS) o 111-3-A Effects of High Water Level on Structures
4.0 CONCLUSION
S NNECO concludes that sufficient information has been compiled on hydrologic considerations to assure that the designs of structures, systems, and components required for safe shutdown reflect consideration of appropriate hydrologic conditions. No significant changes since the original licensing stage (including from the construction of Units 2 and 3) have resulted to impact the original design bases and as such, no further work on this topic is required.
5.0 REFERENCES
1.
Regulatory Guide 1.59, " Design Basis Floods for Nuclear Power Plants" 2.
Standard Review Plan Section 2.4.1 Hydrologic Description 3.
10 CFR, Parts 20, 50, and 100 i
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