ML20041F174
| ML20041F174 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 03/12/1982 |
| From: | Devincentis J PUBLIC SERVICE CO. OF NEW HAMPSHIRE, YANKEE ATOMIC ELECTRIC CO. |
| To: | Miraglia F Office of Nuclear Reactor Regulation |
| References | |
| SBN-227, NUDOCS 8203160260 | |
| Download: ML20041F174 (8) | |
Text
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PUBUC SERVICE smaoox swa
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Company of New HW 1671 Worcester Road Framincham, Massachusetts 01701 (617) - 872-8100 March 12,1982 SBN-227
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United States Nuclear Regulatory Commission
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lig9 tu n Washington, D. C. 20555
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N Attention:
Mr. Frank J. Miraglia, Chief i
Licensing Branch #3 Division of Licensing
References:
(a) Construction Permits CPPR-135 and CPPR-136, Docket Nos. 50-443 and 50-444 (b) USNRC Letter, dated February 12, 1982, " Request for Additional Information," F. J. Miraglia to W. C. Tallman Subjec t :
Responses to 240 Series RAIs; (Hydrologic and Geotechnical Engineering Branch)
Dear Sir:
We have enclosed responses to the subject RAIs, which you. forwarded in Re f e re nc e ( b).
Also enclosed are the following figures which supplement the subject responses:
240.33-1, 240.33-2, 240.33-3, 240.33-4, 240.33-5, 240.33-6, 240.33-7, 240.33-8, 240.33-9, 240.37-1, 240.37-2.
Very truly yours, YANKEE ATOMIC ELECTRIC COMPANY John DeVincentis i
Project Manager JDV : ALL : dad l
Enclosure 7
r203160260 B20312 PDR ADOCK 05000443 A
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240:31 In your analysis of potential site flooding due to intense local (2.4.2.3) precipitation, you have not considered the potential for blockage of site drainage features.
You must demonstrate that the design basis from intense local precipitation will not be adversely-af fected by the potential clogging of site drainage features by ice or storm carried debris.
Using the intense local precipitation listed in FSAR Section 2.4.2.3, the 46 acres served by the site drainage system will experience a maximum overland flow of about 400 cfs if infiltration and other losses are neglected and the drainage system is assumed blocked. This situation would result in less ponding than the design basis of 0.6 feet for which the station has been protected as explained in FSAR Section 3.4.1.1.
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J 240:32 ANSI N170, Section 9.2.2 suggests that for drainage basins less 3
(2.4.3) than 300 square miles, the Probable Maximum Flood. (PMF) be combined with the Probable Maximum Hurricane (PMH) plus 'the.10 percent exceedance high tide.
Please perform the analysis for the if design basis flood 'to account for this combination of severe events and other combinations in' ANSI N170.
RESPONSE
FSAR Section 2.4.5' provides the requested analysis except that the i
Standard Project Flood -(SPF) is used rather than the PMF. This analysis was presented and accepted during PSAR review prior to the issuance of ANSI N170 as a guide for determining design basis.
flooding. The difference in the PMH surge level in Hampton Harbor
. with and without the SPF is only 0.4 feet. This shows that the principal' component of the Harbor water level is due to the hurricane. The addition of a PMF rather than an SPF will increase c
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the flood level'only slightly, less than 0.1 feet.
The increased inflow from the PMF does not increase the water level in Hampton Harbor significantly because any incremental increase in the Harbor level is balanced by an increase flow out of the Harbor through the inlet due to the increased hydraulic gradient.
Based on the above discussion, we conclude that the analysis given
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in FSAR Section 2.4 presents a conservative estimate of the j
maximum water level at the site due to any combination of extreme events.
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240'.33 Provide an unreduced post-construction topographic map (s) that (2.4.2.3) clearly shows site drainage features includlag:
1)
Road grade elevations; 2)
Invert elevation and size of drainage ditches; 3)
Culvert invert elevations, cross sectional areas, type, length and inlet and outlet features; 4)
Where drainage water is temporarily ponded provide the area-capacity information for the storage area; and 5)
Show the drainage sub-areas, direction of flow, drainage areas, hydrograph and peak discharge, and method of computation.
RESPONSE
Figures 240.33-1 through 240.33-9 (UE&C Drawings F-101003, F-101004, F-101005, F-101006, F-101007, F-101071, F-101074, F-101078 and F-101079) provide post-construction details.
Obviously, since construction has not been completed, these dratings do not provide as-built details for the entire site.
6 Water is assumed ponded on the entire site (2 x 10 square feet) when the site drainage systeu capacity is exceeded or when the drains are blocked. This ponding is lost through the site drainage system or via overland flow along the site perimeter if the drains are blocked.
The site drainage system discharges to the settling basin which has a maximum storage capacity of 482,740 cubic feet (11 acre feet).
The site drainage system was designed using the rational method and is capable of conveying the runof f from the probable maximum precipitation (PMP) without flooding of ground-level or below grade safety-related buildings or equipment. The drainage system capacity is calculated to be about 310 cfs.
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i 240'.34 Describe the provisions to protect the plant grade immediately i
(2.4.5) behind the revetments and vertical seawall sections from the effects of erosion caused by wave overtopping and/or runoff.
RESPONSE
The only site area subjected to significant overtopping during the hypothetical probable maximum flood is along the veritical seawall on the southeastern side of the site.
It is not anticipated that this overtopping will cause significant erosion because of its short duration.
Additionally, portions of this area will be protected against erosion by a paved road which will be constructed behind the seawall.
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240".35 Describe the toe protection provided at the vertical seawall 1
(2.4.5)
-(Section 5) to eliminate the effects of scour. Toe scour, if not prevented, could result in structural instability of the vertical seawall.
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RESPONSE
The vertical seawall is founded directly on bedrock as shown in Figure 240.37-2 (UE&C F-101037).. This provides adequate protection against toe scour.
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240'.36 Figure 2.4-24 indicates that the vertical seawall was designed for 2
(2.4.5) both breaking and non-breaking wave forces. What are the criteria to which the vertical seawall was designed in relation to the calculated wave and static forces?
RESPONSE
The seawall has been designed to withstand the forces indicated in Figure 2.4-24.
These forces, when resisted by the passive earth pressure acting against the opposite side of the seawall, do not govern the load for design.
- 240I.37 Provide construction details of revetment and vertical seawall (2.4.5) sections with particular emphasis on as-built specifications for f
the revetment.
Include quarry stone size, weight, and placement techniques.
Provida details of vertical sheetpile and vertical seawall pile includit g length, interlock, tiebacks and anchors.
RESPONSE
Construction details of the revetment, vertical seawall pile and vertical sheetpile are provided in Figures 240.37-1 and 240.37-2 (UE&C Drawings F-101023 and F-101037).
All stone had a minimum specific gravity of at least 2.65.
Up to 25 percent of the stone had length greater than 2.5 but not to exceed three times the width or thickness. Construction of the revetment was done by placing the stone.
Tailgating from the top of the slope was not permitted. All types of stone were placed in two layers interlocked with adjacent stones. A-stone and B-stone were placed to provide minimum voids.
The stone was graded at the source and proportioned by weight as follows:
Capstone for Revetment A shall weigh 1-1/2 tons to 3 tons a.
each. At least 50 percent of stones shall be more than 2.0 tons each.
b.
A-Stone for Revetment A shall weigh from 300 to 600 pounds each, except that up to 10 percent stones may weigh less than 300 pounds or more than 600 pounds each. At least 50 percent of all stones shall be more than 400 pounds each.
c.
B-Stone for Revetment A shall weigh from 15 to 30 pounds each, except that up to 10 percent may weigh less than 15 or more than 30 pounds. At least 50 percent of all stones shall be more than 20 pounds each.
d.
Capstone for Revetment B shall weigh from 700 to 1200 pounds each. At least 50 percent of stones shall be more than 900 pound s.
e.
A-Stone for Revetment B shall weigh from 70 to 120 pounds each except that up to 10 percent stones nay weigh less than 70 or more than 120 pounds each. At least 50 percent of all stones shall be more than 90 pounds each.
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