ML20052C429
| ML20052C429 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 04/30/1982 |
| From: | Mulvihill M, Overbeck G, Steven Roberts FRANKLIN INSTITUTE |
| To: | Staley G NRC |
| Shared Package | |
| ML20052C430 | List: |
| References | |
| CON-NRC-03-79-118, CON-NRC-3-79-118, TASK-02-03.A, TASK-02-03.B, TASK-02-03.B1, TASK-02-03.C, TASK-2-3.A, TASK-2-3.B, TASK-2-3.B1, TASK-2-3.C, TASK-RR TER-C5257-422, NUDOCS 8205040793 | |
| Download: ML20052C429 (52) | |
Text
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TECHNICAL EVALUATION REPORT HYDROLOGICAL CONSIDERATIONS (SEP, II-3A, B, B.L C)
NORTHEAST NUCLEAR ENERGY COMPANY MILLSTONE NUCLEAR POWER STATION UNIT 1 NRC DOCKET NO. 50-245 FRC PROJECT C5257 NRC TAC NO. 41366, 41355, 41344, 41333 FRC ASSIGNMENT 16 l
NRC CONTR ACT NO. NRC-03-79118 FRC TASK 422 i
Preparedby Author: S. L. Roberts, G. Overbeck, l
Franklin Research Center M. Mulvihill, J. Scherrer 20th and Race Street FRC Group Leader: J. S. Scherrer Philadelphia, PA 19103 Prepared for Nuclear Regulatory Commission Washington, D.C. 20555 Lead NRC Engineer:
G. Staley April 30,1982 1
This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, or any of their employees, makes any warranty, ex-pressed or implied, or assumes any legal liability or responsibility for any third party's use, or the results of such use, of any information, apparatus, product or process disclosed in this report, or represents that its use by such third party would not infringe privately owned rights.
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. Franklin Research Center A Division of The Franklin Institute De Benprnan Franxhn Pernway, Phe. Pa. 19103(215) 448-1000 y 3[p[ ! / '!9 ;
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TER-C5257-422 CDNT" 475 Section Title Page 1
INTRobow. ION 1
1.1 Purpose of Review.
1 1.2 Generic BacP. ground.
1 1.3 Plant-Specific Background.
1 2
REVIEW CRITERIA.
3 3
TECHNICAL EVALUATION 4
3.1 Hydrologic Description (SEP Topic II-3. A) 4 3.1.1 Topic Background 4
3.1.2 Topic Review Criteria 4
3.1.3 Evaluation.
4 9
3.1. 4 Conc,lusion.
3.2 Flooding Potential and Protection Requirements (SEP Topic II-3.B).
9 3.2.1 Topic Background 9
3.2.2 Topic Review Criteria 10 3.2.3 Evaluation.
10 3.2.4 Conclusion.
25
. 3. 3 Capability of Operating Plants to Cope with Design Basis Flood Conditions (SEP Tbpic II-3.B.1) 25 3.3.1 Topic Background 25 l
3.3.2 Tbpic Review Criteria 26 3.3.3 Evaluation.
26 3.3.4 Conclusion.
31 iii A
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TER-C5257-422 CDNTENTS (Cont. )
Section Title Page 3.4 Safety-Related Water Supply (Ultimate Heat Sink)
(SEP Topic II-3.C) 31 3.4.1 Topic Background 31 3.4.2 Topic Review Criteria 32 3.4.3 Evaluation.
33 3.4.4 Conclusion.
36 4
CDNCLUSIONS.
37 5
REFERENCES.
39 APPENDIX A - CLAPOTIS DURING PROBABLE MAXIMUM SURGE 45 t
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TER-CS257-422 FIGURES Number Title Page 1
Generalized Site Drsinage Map 8
2 Flood Gate and Flo[d Wall Incations.
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3 Flood Gates.
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Site Plan 22 1
l TABLES r
Nuncer Title Page t-1 Roof top Ponding During 6-Hour PMP 12 i
2 Level of Door tills Protected by Flood Gates 17 3
Elevation of Safety-Related Equipment 18 i
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TER-C5257-422 FOR1lNORD This '14chnical Evaluation Report was prepared by Franklin Research Center under a contract with the U.S. Nuclear Regulatory Connaission (Office of Nuclear Reactor Regulation, Division of Operating Reactors) for technical assistance in support of NRC operating reactor licensing actions.
The technical evaluation was conducted in accordance with criteria established by the NRC.
Mr. J. S. Scherrer, Mr. G. Overbeck, Mr. M. Mulvihill, and Ms. S. L.
Rooerts contributed to the technical preparation of this report through a subcontract with WESTEC Services, Inc.
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TER-C5257-422 1.
INTRODUCTION 1.1 PURPOSE OF REVIEW Tne purpose of this review is to evaluate the assumptions, conclusions, and ccanpleteness of documentation in responses by the Northeast Nuclear Energy Company (NNECO) to the U.S. Nuclear Regulatory Commission's (NRC) review of systematic evaluation program (SEP) Topics II-3.A (Hydrologic Description),
II-3.B (Flooding Potential and Protection Requirements), II-3.B.1 (Capability of Operating Plants to Cope with Design Basis Flooding' Conditions), and III-3.C (Safety-Related Water Supply - Ultimate Heat Sink) for the Millstone Unit 1 Nuclear Power Station.
This review includes independent analyses by the Franklin Research Center (FRC) as needed to clarify or resolve issues.
The NRC is reviewing other safety topics within the SEP and intends to coordinate r
an integrated assessment of plant safety after completion of the review of all applicable safety topics and design basis events (DBEs).
1.2 GENERIC BACKGROUND The SEP was established to evaluate the safety of 11 of the older nuclear power plants.
An important element of the program is the evaluation of the plants against current licensing criteria with respect to 137 selected topics, several of which relate to hydrologic assessments of the site.
In a letter dated January 14, 1981 (1], the NRC agreed to the SEP Owners Group's proposed redirection of the SEP, whereby each licensee would submit evaluations of 60% of the SEP topics in time for a review by the NRC staff to be completed by June 1981.
Evaluations of the topics not selected by each licensee were the NRC's responsibility.
1.3 PLANT-SPECIFIC BACKGROUND In a series of letters to the NRC (2 through 5), the Licensee submitted its original evaluation of SEP hydrology topics as follows: O ddhd Franidin Research Center
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s TER-C5257-422 Topic II-3.A Hydrologic Description, dated June 25, 1981 [2]
Topic II-3.B Flooding Potential and Protection Requirements dated June 26, 1981 [3]
Topic II-3.B.1 Capability of Operating Plant to Cope with Design Basis Flooding Conditions, dated June 25, 1981 (4]
Topic II-3.C Ultimate Heat Sink [5].
FRC assessed the Licensee's submittal and identified deficiencies in a formal Request for Additional Information (RAI) sent to the NRC.
That RAI was forwarded to the Licensee and resulted in subsequent responses (6-9] as follows:
Topic II-3.A - dated November 20, 1981 (6)
Topic II-3.B - dated November 19, 1981 [7]
Topic II-3.B.1 - dated November 19, 1981 [8]
Topic II-3.C - dated November 19,.981 [9].
The Licensee responded to further questions from the FRC in Addendum (Draf t) to SEP Topic II-3.B, received February 12, 1982 (10].
This technical evaluation report (TER) incorporates hydrologic inform-ation provided by the Licensee and evaluates the adequacy of flood protection structures at Millstone Nuclear Power Station Unit 1.
FRC has used several other sources of information for this evaluation, including USGS Topographic Maps, U.S. Coastal and Geodetic Survey mapping, a site visit by the reviewers
[11], and information contained in Docket 50-245. A UbFranklin Research Center A OMeson d The Fransen me
TER-C5257-422 2.
REVIEW CRITERIA The reference criteria used for all the hydrology topics were based on the Code of Federal Regulations, Volume 10, Section 50 (10CFR50), Appendix A, General Design Criteria, overall Requirements, Criterion 2, entitled " Design Bases for Protection Against Natural Phenomena." Specific topic review criteria were taken from the following documents:
Standard Review Plan (SRP) [12]
2.4.1 Hydrologic Description j
2.4.2 Floods 2.4.3 Probable Maximum Flood (PMF) on Streams and Rivers 1
2.4.4 Potential Dam Failures 2.4.5 Probable Maximum Surge and Seiche Flooding 2.4.6 Probable Maximum Tsunami Flooding 2.4.7 Ice Ef fects 2.4.8 Cooling Water Canals and Reservoirs 2.4.9 Channel Diversions i
2.4.10 Flooding Potential Requirements 2.4.11 Iow Water Considerations 2.4.13 Groundwater 2.4.14 Tecnnical Specifications and anergency Operation Requirements 3.4.1 Flood Protection 9.2.5 Ultimate Heat Sink Regulatory Guides 1.27 Ultimate Heat Sink for Nuclear Power Plants [13]
1.59 Design Basis Floods for Nuclear Power Plants [14]
1.102 Flood Protection for Nuclear Power Plants [15]
American National Standards Institute N170-1976 Standards for Determining Design Basis Flooding at Power Reactor Sites [16].
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TECHNICAL EVAIDATION 3.1 HYDROIDGIC DESCRIPTION (SEP 'IOPIC II-3. A) l 3.1.1 Topic Background The Licensee's original submittal for Topic II-3. A [2] presented the site hydrologic description.
Further information provided by the Licensee was contained in the submittal of November 20, 1981 [6].
A site visit by the reviewers [11] also contributed to the evaulation of this topic.
3.1.2 Topic Review Criteria The review criteria used for this section are identified in American National Standards Institute N170-1976, Standards for Determining Design Basis Flooding at Power Reactor Sites (16] and Standard Review Plan Section 2.4.1 -
Hydrologic Description [12].
t 3.1.3 Evaluation Location The Millstone Nuclear Power Station is located on the north shore of Iong Island Sound.
The site is bounded on the north by the Millstone Units 2 and 3 site, on the east by an abandoned quarry (and farther east, Jordan Cove), on the south by Long Island Sound, and on the west by Niantic Bay.
l Design Basis The hydrologic design bases are as follows:
Roof Drains - 3 inches in 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />; 7.10 inches in 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
This I
corresponds to a once-every-100-year rainfall [7].
The maximum 24-hour rainfall recorded at Bridgeport, Conn. was 6.89 inches in 1972.
Roof Ioading - design basis live loading is 60 psf [6].
Flood Protection Structures - exterior walls of all safety-related structures are designed to protect against hydrostatic forces to elevation 19 feet mean sea level (msl) through use of emergency procedures to close flood gates.
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TER-C5257-422
.I Hurricane Surge and Wave Height - the design basis hurricane is a transposition of a severe hurricane of September 1944 at Cape Hatteras.
The maximum stillwater level is 14.3 feet mal and maximum runup would reach elevation 18.2 feet mal [22).
Intake Structure - the Licensee states that the design basis hurricane would cause a clapotis to form on the face of the intake structure.
The crest would be at 32.4 feet asl and the trough at 2.4 feet asi.
Stress would vary uniformly from 0 at the crest to 955 psf at stillwater level, which is 13.4 feet mal.
Maximum water level inside the intake would be 15.9 feet mal [22].
Runoff - the design basis rainf all rate for Millstone Unit 1 storm sewers is 2.00 inches per hour for a 30-minute duration (10).
The Licensee has stated that, regardless of the capacity of the storm sewer system, the site would drain naturally so that runoff would flow directly into the Niantic Bay with no measurable accumulation at the plant site.
Groundwater - unavailable.
The Licensee has stated that the original structural design considerations are not available for review. Design criteria used to reflect groundwater-induced loads cannot be verified.
Rivers, Streams, and Drainageways To the west, tne site is bounded by the Niantic Bay, which is approxi-mately 2 miles wide in an east-west direction.
Drainage southward into the Niantic Bay is from the Niantic River. Minor runoff tributaries drain into Jordan Cove to the east of the plant site.
All watershed land that feeds drainageways on Millstone Point is located on the point itself.
Runoff from most of Millstone Point drains directly into the ocean.
There are no dams or other hydraulic control structures on the Niantic River or on other drainageways in the area [18].
Neither are there any stream j
flow gages on adjacent watersheds.
The nearest public surface water users are the Groton Water Department, which serves 27,000 users in Groton; the Mystic Valley Water Company, which supplies 12,000 customers in Stonington and Mystic; the New London Water Department, which supplies 31,906 users in New London and Waterford; the Norwich Water Department, whien serves 41,418 customers in Norwich, Fitchville, l 4
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TER-C5257-422 and Yantic; and the Connecticut Water Company's Guilford-Chester Division, which supplies 8,500 people in Guilford [19].
Coast There Millstone Point is located on tne north shore of Iong Island Sound.
To the west of Millstone Point is Niantic are several small islands nearby.
Bay, which is fed by the Niantic River.
During high tide, water from the bay flows into the Niantic River [18]. West of Niantic Bay is Blackstone Point.
To the east of Millstone Point is Jordan Cove, and to the east of the cove is l
Both Blackstone Point and Great Neck extend farther south into Great Neck.
Long Island Sound than does Millstone Point.
The elevation of the highest point in the vicinity of the plant is 29 feet Plant yard grade varies from 13.5 to 14.5 4
mal on the east edge of the quarry.
feet mal (17].
At Millstone Point,* tides are semidiurnal. Mean high water is 1.73 feet msl and mean low water, -0.97 feet mal (19].
The mean tidal range is 2.7 feet and the spring range is 3.2 feet. On the average, tides more than 3 feet above mean high water occur once a year, tides more than 2 feet above mean high water level occur 5 times a year, and tides more than 1 foot above mean high water occur 90 times a year [18].
The lowest recorded water level at New London,. Connecticut since 1938 was -4.37 feet mal, on December 11, 1943 (19].
When the tide is rising, tidal currents around Millstone Point are In westerly, and when the waters are receding, tidal currents are easterly.
Niantic Bay, flood tide currents move in a northwesterly direction, whereas during ebb tide, flow is southeasterly (20].
Prevailing winds are from the south-southwest in the summer and from the northwest during the winter [20].
Since 1938, six severe hurricanes have caused high seas.
The highest was a still water level of 10.0 feet mal at Niantic, resulting from a storm surge estimated as 7.3 feet high at New Iondon (18].
Earlier reports of high water levels include records of hurricanes from other parts of the North Atlantic At Plymoutn, Massachusetts, a hurricane in August 1635 was reported to coast. _nklin Research. Center
TER-C5257-422 have caused sea levels above 20 feet.
In August 1638, a hurricane produced a tide 14 to 15 feet higher than the spring tides.
Providence, Rhode Island reported a flood mark 16.2 feet above mean low water level af ter a hurricane in September 1815 [20].
Wave runup may f ar exceed still water levels on the New England coast, and there are reports of flood or wave damage up to 25 feet above still water levels (20].
Site Drainage The plant is located on Millstone Point, which is dissected by an abandoned quarry and a harbor, both to the south of the plant structures.
The quarry is filled with water and connected to Long Island Sound by a discharge canal [21].
Natural drainage patterns on the point are into Niantic Bay and Long Island Sound, and a small area drains through the quarry, as shown in Figure 1.
The land north and west of the point drains into Niantic Bay and P
Jordan Cove directly, with no major drainageways passing through the plant site.
Each of the three units of the Millstone Nuclear Power Station is equipped with a storm drain system designed to drain 2 inches of precipitation per nour (10, 17, 19].
The Unit 1 system is composed of a network of catch basins, reinforced concrete pipes, and drainage ditches.
Ita design was based on computations using a rainfall rate of 2 inches per hour for a 30-minute duration [17].
Groundwater Grounawater movement on Millstone Point is extremely slow, as evidenced by the fact that the average water level measured in the granite quarry was 17 feet below mal before the discharge canal connecting the quarry to Long Island Souno was built.
This quarry was worked from 1830 to 1960 only 200 feet from the Sound without a, groundwater flow of sufficient volume to balance the water levels as ref erenced by the Licensee [2].
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TER-C5257-422 Permeability of the bedrock is very low.
Permeabilities of the overlying soils are also relatively low, with the higher layers being more pervious than the lower.
Partial stratification and sand lanses exist in some places near the surf ace.
Most groundwater movement occurs in the upper layers, and groundwater is perened in some areas.
There are substantial seasonal groundwater fluctuations [18].
There are bedrock outcrops to the north and south of the plant. These may act as a groundwater divide, separating the tip of Millstone Point from the soils and groundwater farther inland.
If this is the case, groundwater recharge is from precipitation only or possibly also from the waters of Long Island Sound. Water is ponded in bedrock troughs in some areas (18].
Ice There is no available history of ice or ice jams in Niantic Bay.
r 3.1.4 Conclusion The information provided by the Licensee about groundwater is not adequate to identify either the original design basis or a maximum groundwater elevation.
Also, the Licensee has failed to specify the water sources for local surface water users.
Otherwise, the description of the hydrologic environment of Millstone Unit 1 meets the requirements of SEP Topic II-3. A, Hydrologic Description.
3.2 FIDODING POTENTIAL AND PROTECTION REQUIREMENTS (SEP TOPIC II-3.B) 3.2.1 Topic Background The Licensee's original submittal for Topic II-3.B [3] presented the flooding potential and requirements for protection of the site.
Fur ther information provided by the Licensee was contained in submittals dated November 19, 1981 [7] and February 12, 1982 [10].
A site visit by the reviewers [11] also contributed to the evaluation of this topic. _nklin Rese_ arch _ Center
TER-C5257-422 l
3.2.2 Topic Review Criteria Criteria for the review of flooding potential and protection requirenents were taken from the following sources:
Standard Review Plan (SRP) Sections 2.4.2 Floods 2.4.3 Probable Maximum Flood (PMF) on Streams and Rivers 2.4.4 Potential Dam Failures 2.4.5 Probable Maximum Surge and Seiche Flooding 2.4.7 Ice Effects 2.4.10 Flooding Potential Requirements NRC Regulatory Guides 1.59 Design Basis Floods for Nuclear Power Plants
- 1. 10 2 Flood Protection for Nuclear Power Plants 1.13 5 Normal Water Level and Discharge at Nuclear Power Plants American National Standards Institute (ANSI) N170-1976 Standards for Determining Design Basis Flooding at Power Reactor Sites.
3.2.3 Evaluation Introduction The flooding mechanisms which will be addressed in this section are roof ponding, local flooding, hurricane storm surge, and groundwater ponding.
No otner sources of flooding are known to exist at the Millstone site.
Design bases for protection against these flooding mechanisms are specified in Section 3.1.3.
Further protection is provided by an emergency procedure, OP 514A [8], which directs closing of flood gates upon receipt of nurricane, tornado, or flood warnings, or upon observations of high winds or water levels.
This procedure is reviewed under Topic II-3.B.1.
l Probable Maximum Precipitation The 10-square-mile prooable maximum precipitation (PMP) at the Millstone site is 25.53 inc' es of rainfall in 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />, 28.29 inches in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, and h
30.59 inches in 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> 123].
The distribution of rainf all during the 6 U@J Franklin Research Center A DMeson of The Fransen insatues
TER-C5257-422 hours of heaviest precipitation i.* 12.51 inches, 3.84 inches, 2.81 inches, 2.55 inches, 2.04 inches, and 1.78 inches [24].
]
Roof Ponding Current NRC criteria require that roofs of safety-related structures be able to safely support the load resulting from the PMP with roof drains completely blocked.
The design basis roof live loading for safety-related structures at the Millstone plant is 60 lb/ square foot [6), which is the pressure exerted by 11.53 inches of water.
The southwest area of the reactor building and the gas turnine building roofs are acceptable under current criteria because their parapets are not high enough to retain the depth of water wnich would exert 60 psf [10).
All other safety-related structures (the turbine building, the intake structure, the radwaste/ control building, and other areas of the reactor building) fail bi meet current NRC requirements because they must rely on roof drains to prevent ponding of rainwater from exceeding the roof's l
structural design basis (see Table 1) (10).
If the roof drains were fully blocked, tnen the heaviest single-hour precipitation,12.51 inches, would be sufficient to exceed the roof design capacity by 8.5%.
All the building drains are designed to discharge 3.00 inches per hour of rainfall [6].
Table 1 shows the hourly accumulation of storm water with three drain conditions. With the roof drains functioning to full design capacity, the 2 highest hours of PMP occurring consecutively would result in ponding of 10.35 inches of rainwater on the roof. This is 1.18 inches of water or 10.2%
less than the design basis roof loading, and no further accumulation of rainwater would occur on the roof tops.
After 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.of PMP, ponding would be reduced to 7.53 inches.
If the roof drains were blocked so that they functioned to half of design capacity,16.53 inches of water would pond during the highest 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> of PMP; this is 5 inches or 43% above the roof design loading. The design loading could be exceeded in less than 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.
These values represent the average loading over the entire roof. Clearly, storm nklin Research Center
TER-C5257-422 Table 1.
Rooftop Ponding During 6-Hour PMP Inches of Average Ponding with Roof Drains Hou.'
Inches of Fully 50%
Fully of PMP Hourly PMP Open Blocked Blocked 1
12.51 9.51 11.01 12.51*
2 3.84 10.3 5**
13.3 5*
16.35 3
2.81 10.16 14.6 6 19.16 4
2.55 9.71 15.71 21.71 5
2.04 8.75 16.25 23.75 6
1.78 7.53 16.53 25.53
- At this time, loading exceeds design basis.
- This is the highest level of ponding resulting with roof drains fully functional.
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r TER-C5257-422 water would be deeper in low parts of the roof, where the roof slopes down to the drains, and in these places, roof design loads would be exceeded af ter an even shorter duration of rainfall.
The roofs of the gas turbine building and the southwest area of the reactor building are acceptable by current NRC standards.
Roofs of the intake structure, the radwaste and control building, the reactor building, and all areas of the turbine building do not meet NRC criteria because their roof drains must be more than 50% functional to prevent the design basis roof loading from being exceeced during local PMP.
Possible solutions to this problem are scuppers in the parapets, removal of sections of the parapets, and an inservice inspection program.
Local Plooding The safety-related structures at the Millstone plant are protected against flooding by their exterior walls, which are constructed of concrete and have been analyzed and determined able to withstand hydrostatic loads to elevation 19.0 feet mal.
These walls are called flood walls [7].
All door openings in these flood walls are equipped with flood gates (see Figure 2),
j which can be closed when a flood is anticipated.
These gates extend from the doorsills to elevation 19.0 feet mal (see Figure 3) and provide a uniform level of protection with the flood walls [22]. The only exception is the intake structure, where doorways have no flood gates.
Instead, service water and emergency service water pump motors are at elevations 21.5 and 19.25 feet msl, approximately (3], and two large drainage pits are provided in the floor (111 The plant area storm drain system is designed to remove water at the rate of 2 inches per hour (17].
The Licensee has stated that even if this drainage system were incapacitated, natural drainage into Niantic Bay would prevent measurable accumulation of storm water around the plant structures.
No analyses have been performed to support this claim (7].
Review of flood protection features shows that closing of flood gates during a local heavy rainstorm cannot be ensured.
Heavy precipitation is not A Nbranklin Research Center A Dheen af The Frennen anssente
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Note: Numbers in figure refer'to flood gate identification numbers in Table 2.
Figure 2.
Flood Gate and Flood Wall Incations
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TER-C5257-422 included as an initiating event in OP 514A, " Natural Occurrences" [8].
Further, storm water would accumulate almost immediately on the paved surfaces around the plant, and flood gates could not be closed in time to prevent inflow of water.
For these reasons, the plant level of protection against local flooding from heavy rainf all must be considered the door sills instead of 19.0 feet asi (see Table 2).
Inspection of site topography and drainage patterns failed to corroborate the Licensee's claim that natural drainage would prevent ponding of water on the plant site.
The plant' yard is flat, which delays runoff; and numerous features sucn as curns at roadsides, walkways, and railroad tracks (10] could prevent storm water from running off to the quarry and Niantic Bay.
Storm water from west of Units 2 and 3 flowing toward the quarry would also contri-bute to ponding around Unit 1.
The turbine building east door, the solid radwaste building west door, the fire pumphouse door, the warehouse southside door, the machine shop door, and the gas turbine building doors all appear to be susceptible to flooding (see Table 3) (10).
Conclusively confirming or disproving this conclusion is impossible without legible, current topographic maps of small contour interval.
However, analyses performed based on the only maps available, using the rational method, showed that with drains occluded, water would pond around tne gas turbine generator building, the warehouse, the radioactive waste and control building, and the fire pump house to about elevation 15.5 feet mal during PMP.
This elevation is slightly above the door sill levels in these buildings (see Table 2).
The equipment which could be affected by a foot of ponded water in the radioactive waste and control building is unknown; elevation of safety-related equipment in some other structures is noted in Table 3.
Wires and electric bus to the diesel generator and gas turbine would De af fected by ponding to 15.5 feet mal [11].
Since the Licensee has failed to provide adequate maps, flooding potential during local PHP must be considered an open item.
The effects on the fire pump house, the radwaste and control buildings, and the A-6 switch gear of poncing ddring local PMP are unknown and should be determined.
Results as drastic as flooding during PMH or roof top failure are not Udij Franklin Research Center A DMeson of The Fransen ineande
TER-C5257-422 Table 2.
Level of Door Sills Protected by Flood Gates [26]
Level of Door Sills Number Location (feet mal) 1 Turbine Building 14'11" East Door 2
Solid Radwaste Building 14'11" West Door 3
Solid Radwaste Building 14'11" 4
Stairway (inside building) 4 Solid Radwaste Building 14'11" North End (inside building) 5 Solid Radwaste Buidling 14'11" South End (inside building) 6 Fire Pump House 14'7" 7
Reactor Building Railroad unknown Access Door l
8 Reactor Building unknown i
Personnel Door 9
Boiler Room 14'7" 10 Warehouse East Side 14'7" 11 Gas Turbine Building North Side 14'7" 12 Gas Turoine Building West Side 15' 13 Gas Turbine Building South Side 15' 14 Warehouse South Side 14'7" l
15 Machine Shop 14'7" 16 Turbine Building Railroad 14'11" Access to Decondenser Room 17 Turbine Building Railroad 14'11" Access to Turbine Building 18 A-6 Switchgear 15' nklin Research Center A o==aa # n. r-m.
TER-C5257-422 Table 3.
Elevation of Safety-Related Equipment (11]
Structure Equipment Elevation Intake ESW pump motors Approx. 5' above floor Approx. 19.25' mal Gas Turbine Building Turbine 5.5' above floor 20' mal Wires 6" abcVe floor Turbine Building Feed pumps 2' above floor Electric bus to diesel generator SR equipment 17 1/2" above floor Warehouse Sill of door No sill; floor to turbine building level r
l l
l nklin Research Center
. - ~. - -.
TER-C5257-422 anticipated from local ponding.
However, to ensure compliance with current NRC criteria, a thorough study of local runoff should be performed using current maps, acd safety-related equipment located below 15.5 feet mal should be raised or protected.
There are no rivers, streams, lakes, or reservoirs near enough to Millstone Point to affect flooding at the site.
Thus, there are no dans whose failure might result in flooding at the Millstone plant.
Hurricane Flooding Current NRC criteria for hurricane flooding require that all safety-related structures and equipment be protected from the probable maximum hurricane (PMH). The PMH is the event with the highest water level, resulting from the sum of the following components:
initial rise (also called forerunner or sea level anomaly), lot exceedance high spring tide, pressure setup, wind setup, and wave activity associaced with the winds generated by the hurricane.
Stillwater Level The Licensee has provided a " Study of Flood Potential from Probable Maximum Hurricane" [7].
The components of the high water level from the PME in this study, and the corresponding values cited in Regulatory Guide 1.59
[14], are as follows:
Unit 1 FSAR Reg. Guide 1.59 Initial rise O ft 1.0 ft Rise due to atmospheric, 2.0 ft 2.2 ft pressure reduction Wind setup 12.5 ft
- 12. 41 f t Tide
_1_.5 ft msl 2.83 ft ms1*
Total still water level 16.0 ft msl 18.44 ft ms1*
- Converted from mean low water (m1w), which is -0.97 msl.
nklin Research Center A Cwamon of The Frerman wusue
I e
TER-CS257-422 The Licensee's values for rise due to atmospheric pressure reduction and wind setup are, in sum, so close to the values in Regulatory Guide 1.59 that they are acceptable without scrutiny.
Regulatory Guide 1.59 requires the use of 10% exceedance high tide, defined as "the predicted maximum monthly astronomical tide exceeded by 10% of the predicted maximum monthly astronomical tides over a 21-year period." The value used by the Licensee,1.5 feet mal, is labeled " astronomical tide peak."
Mean high water at Millstone Point is 1.73 feet asl [19], so it is clear that l
(
l.5 feet mal is a far less conservative design basis than that required by Regulatory Guide 1.59.
Another difference between the Licensee's PMH study and the calculations for the probable maximum surge in Regulatory Guide 1.59 is the 1.0-foot initial rise, which is used in the Regulatory Guide but omitted by the Licensee.
Initial rise is defined as "an anomalous departure of the tide level from tne predicted astronomical tide" [16].
The Licensee presented a discussion challenging khe use of an initial rise at the Millstone site or elsewhere in Connecticut or New England, stating that, between 1919 and 1961 along the New England coast, the monthly mal has varied less than 1 foot [3].
According to ANSI N170-1976, "the sea level anomaly need not be included when 10 percent exceedance high tide is based on recorded tides.
If 10 percent exceedance high tide is based on predicted tide levels sea level anomaly shall be added.
Whichever is lower may be used."
Since the Licensee's astronomical tide peak is inadequate by the standard of Regulatory Guide 1.59, the Licensee is required to use a 1.00 foot initial rise.
In sum, the Licensee's PMH estimate of 16.0 feet asl stillwater level does not meet the criteria of Regulatory Guide 1.59.
A second calculation of PMH stillwater level was made by the Licensee using more conservative assumptions.
The resulting value, 19.17 feet asl [3], is in compliance with Regulatory Guide 1.59.
No PMS elevation lower than that in Regulatory Guide 1.59 (18.44 feet mal) has been presented which meets the criteria of ANSI-N170. Therefore, the PMH stillwater level is 18.44 feet asl. The NRC has accepted the value of 18.11 feet asl PHM stillwater surge for Millstone
._nklin Research_ Center
4 TER-C5257-422 Unit 3 (19 ].
Since the Millstone Unit 3 PMB stillwater level is only 1.77%
lower than the value in Regulatory Guide 1.59, it should meet the NBC current criteria.
Wave Action 1
Regulatory Guide 1.59 specified that " Coincident wave heights and wave runup should be computed and superimposed on the PMS [ probable maximum surge]
stillwater level." No values are provided in Regulatory Guide 1.59 for wave runup at Millstone Point.
The Licensee provided a study of wave effects with the 16.0 feet mal PHH stillwater level.
Since this PMH estimate has been shown to be inadequate, above, the associated wave heights are not appropriate design bases.
No calculation of wave heights and wave runup coincident with a 19.17 feet mal storm surge was provided by the Licensee [3]. Wave effects must be computed and added to the stillwatpr level before the PMH estimate can be accepted.
In the Millstone Unit 3 PSAR, a hydrograph for the 18.11 foot PMS is provided, but concurrent wind angles are not tabulated [19].
The study of wave ef fects for Millstone Unit 3 has only limited application to Unit 1, because of the diff erent locations and elevations of all safety-related structures, including intake structures, for the two units.
There are two conditions for wave effects on Millstone Unit 1.
The first l
condition is wave action on all structures durinc the peak surge from waves transmitted over the Point.
The second condition is wave action on the intake structure, shown in Figure 4, which is built on the edge of the Point, facing deep water. Wave effects from each of these two conditions will be presented l
separately, followed by a discussion of the design basis levels of protection.
All PMH studies for Millstone Point show that the highest waves will break before they reach the plant area, dissipating most of the wave force and resulting in only about a foot of runup at the plant walls.
The Licensee also claims that the hig' hest waves which could be transmitted through the quarry without breaking would break at the edge of the quarry.
These analyses can be confirmed, but these conditions do not provide the limiting wave effects. nklin Research Center A Chuson af The Frannhn insomme
Os 9
TER-C52 57-422 I
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TER-C5257-422 Non-breaking waves could be transmitted through the quarry or across lower areas of the point up the plant wall, where a standing wave could be formed.
At a stillwater level of 16.5 feet mal incident waves with heights of 1.3 feet would form a clapotis with a crest at 19.0 feet asl, overtopping the floodwalls, and at a stillwater level of 18.0 feet asl waves 2.3 feet high would form a clapotis reaching 22.1 feet as1.
These calculations are presented in detail in Appendix A.
Resultant loading on the plant walls at elevation 14.5 feet asl from a clapotis which would form at stillwater level 18.11 feet is a horizontal force of 1334.5 pounds per linear foot of wall and a bending moment of 3342.1 foot-pounds per linear foot [27].
This is the maximum loading on all safety-related structures except the intake structure from wave action during PMH.
The Licensee has stated d2at all safety-related structures are designed to withstand hydrostatic loading to elevation 19.0 feet msl [4].
Though exact values are not specified, this is probably less than one-third of the PMH loading provided aoove. PThis loading configuration should be investigated under Topic III-3.A, Ef fects of High Water Level on Structures.
Overtopping of the flood walls by 3.3 feet (15%) would occur during a hurricane surge of 18.11.
These conditions are unacceptable under current NRC standards.
The intake structure is subjected to a different type of wave action than other structures.
It is built on the edge of the point, fronting the relatively deep water of Niantic Bay.
The Licensee states that during the PMH l
I when the wind is in the direction to cause wave attack on the intake structure I
(190* clockwise from north), the stillwater level would be substantially l
recuced from the peak surge, and that the operation of the service water and emergency service water pumps would not be seriously threatened [7].
Coincident wind directions are not tabulated with the 18.11 foot PMH hydrograph (19), but transposition of the 16.0 foot PMH hydrograph shows that when the wind shifts to 190', the surge level will have dropped to 9 feet mal i
and the wind speed to 70 mph [22].
Both of these values are lower than the 1
corresponding values (stillwater 13.4 feet mal, wind 90 mph) which would cause the maximum clapotis during the design basis hurricane [22),
i
_nklin Research._ Center
=
TER-C5257-422 The Licensee has stated that the intake structure has been analyzed and determined able to withstand a clapotis to. 32.4 feet mal, generated from a stillwater level of 13.4 feet asl, and a windspeed of 90 mph.
The loading resulting from this clapotis would be 955 psf at elevation 13.4 feet asl and would vary linearly to 0.0 psf at 32.4 feet mal.
Capability of the intake structure to withstand the design basis loading should be confirmed under Topic III-3. A, Effects of High Water Level on Structures; or during integrated assessment.
Based on review of all available information, the following conclusions were reached.
The PMH stillwater level is 18.44 feet asl.
The value of 18.11 feet mal, as presented in Millstone Unit 3 PSAR, might meet the NCR criteria.
Windwaves during peak surge could cause a clapotis to form on the walls of 22,.7 Unit 1 safety-related structures, which could reach elevation Strf9 feet mal and exert loading which far exceeds the design basis loading on the floodwalls. This condition violates current NRC requirements.
The maximum clapotis on the intake structure, however, would be substantially lower than the clapotis which would occur during the design basis hurricane.
Groundwater There is no indication that groundwater loading was an original design basis for Millstone Unit 1 structures.
Further, no records of groundwater levels at the Millstone site are available for review.
Current design basis groundwater level should be plant grade elevation for all future investigations.
The Licensee has stated tnat safety-related structures were designed to resist hydrostatic and uplif t pressures that would result from groundwater rising to plant grade, plus water above ground to elevation 19.0 feet msl
[7].
No information has been provided which states whether the plant structures can withstand groundwater to plant grade in combination with seismic loads. g h) Franklin Research Center A Quesan af The Frarmen rumane
TER-C5257-422 3.2.4 Conclusion The PMH study provided by the Licensee (7] is inadequate.
The PMH stillwater level has been established by the NRC as 18.44 feet asl (14), and the elevation of 18.11 feet asl has been accepted by the NRC for Millstone Unit 3 (19].
Independent analysis shows that a clapotis formed by non-breaking waves during the peak surge is the maximum loading condition from waves during PMB.
This loading far exceeds the Licensee's design basis of a hydrostatic load to elevation 19.0 feet mal.
Review confirms that the Licensee's design basis clapotis on the intake structure will not be exceeded during the PMH.
During PMP, building drains could prevent water from ponding on the roofs of safety-related structures beyond the levels those roofs can support. With roof drains 50% or 100% blocned, roof ponding can exceed design capacity.
This situation is not in compliance with current NRC standards.
Resolution of this problem might be ach.ieved through removal of parapets, construction of scuppers, or an inservice inspection program, such as is addressed in SEP Topic III-3.C.
A site visit (11] and review of topographic site maps (17] have failed to confirm the Licensee's contention that natural site drainage is adequate to remove PMP from, the site with no measurable accumulation.
Several areas have been identified in this review where ponding might exceed the level of l
protection for safety-related structures. They should be investigated with 1
information which only the Licensee can provide.
3.3 CAPABILITY OF OPERATING PLANTS 'IO COPE WITH DESIGN BASIS FIDOD CONDITIONS
(
(SEP 'IOPIC II-3.B.1) 3.3.1 Topic Background The Licensee's original submittal for Topic II-3.B.1 (4] presented information on the ability of the plant to cope with the design basis flood.
Further information provided by the Licensee was contained in the submittal dated November 19, 1981 (8).
A site visit by the reviewers (11] also contributed to the evaluation of this topic.
nklin Research Center A Osmimon ad The Fransen insumme
TER-C5257-422 3.3.2 Topic Review Criteria The following references were used as review criteria o ANSI N170-1976 o NRC Regulatory Guide 1.59 o Standard Review Plan, Sections 2.4.3, 2.4.4, 2.4.5, 2.4.7, and 2.4.14.
3.3.3 Evaluation The surge from the PMH has been determined to reach elevations above the level of the doors to the Millstone plant structure when they are not protected by flood gates.
A procedure exists to ensure that the required flood doors are in place in the event of a hurricane.
This procedure plus the emergency instructions for tornado and high winds are combined in a document entitled " Natural Occurrences" OP 514A [8].
The purpose is as follows:
?
"1.
OBJECTIVE To provide the operator witn instructions for actions to be taken upon receiving hurricane, tornado, or flood warnings from CONVEX, or l
upon site observation of high winds or high tides.
l 2.
DISCUSSION Normally there will be ample warning of approaching storm conditions wnich might result in high winds and/or high tides.
This advance warning will allow time for the plant to be placed in a state of l
standby readiness."
1 Tne protection procedure is implemented when any of the following conditions is met:
"3.
SYMPTOMS I
3.1 The water level, including wave crest height, is exceeding plant l
grade level (14.0 feet).
l l
3.2 The' measured fifteen minute average wind speed at nominal elevation 142 on the meteorological tower exceeds 60 MPH.
_nklin Research_ Center
TER-C5257-422 3.3 Receipt of a hurricane warning from CDNVEX.
3.3.1 CONVEX will provide the following information to the station.
i 3.3.1.1 Position of storm, latitude and longitude when the storm center is 400-500 miles from us.
3.3.1.2 Storm direction.
3.3.1.3 Speed of center.
3.3.1.4 Forecasted storm pressure - start reporting when storm is in general direction of some land mass.
NOTE:
Calls between CDNVEX and the station as to the storm progress must be at least every two (2) hours.
3.4 South / Southwest winds greater than 30 MPH (sustained) as measured at elevation 142 on the site meteorological tower."
l When any of the above-listed symptoms from Section 3 of OP 514A occurs, r
the following procedure is implemented:
l "4.
AU'IOMATIC ACTIONS f
4.1 None l
{
5.
IMMEDIATE ACTION Hurricane 5.1 Notify higher plant supervision of weather conditions and plant status.
5.2 Notify all department heads of the situation and ensure enough personnel are brought in or placed 'on-call' to cover all areas requiring assistance.
5.3 Dispatch personnel to secure all loose equipment and materials.
5.4 Place all traveling screens on continuous wash at high speed.
5.5 Close all plant flood gates, i
nidin Research Center A Opuienen af The Frannen insumme
TER-C5257-422 5.6 Station personnel in the main transformer yard who will be able to assess any arcing problems and recommend action to be taken before any damage can occur.'
5.7 Increase surveillance at the intake structure.
5.8 Secure the chlorine system at the tank car.
5.9 Reduce load as follows:
5.9.1 Hurricane Forecast Winds Less Than 90 MPH NOTE:
If conditions change and it is apparent that hurricane winds will reach or exceed 90 MPH, proceed to action step 5.9.2.
If it is apparent that the maximum hurricane wind speed will remain less than 90 MPH, carry out the below action steps.
5.9.1.1 Reduce power below 45% interlock.
This will protect the reactor in the event of a turbine trip from other than a line fault.
5.9 l.2 If loss of all circulators is iminent commence a f
shutdown to hot standby.
5.9.1.3 If transformer arcing increases to a point that the plant is in danger commence a shutdown to hot standby.
5.9.2 Hurricane Forecasted Winds Less Than 90 MPH in Four (4) Hours 5.9.2.1 Shutdown to hot standby.
5.9.3 If conditions result in a plant trip, refer to Emergency Procedure 502.
5.10 Sustained Winds of Thirty (30) MPH or Greater 5.10.1 Increase surveillance at the intake structure.
5.10.2 Increase surveillance in the main transformer yard.
5.10.3 If intake screen fouling becomes excessive, reduce power to 60% so two circulators can carry the load.
5. l'0. 4 If loss of all circulators is iminent commence a shutdown to hot standby. nklin Research Center A Ofween cd The Frannan Insense
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TER-C5257-422 5.10.5 If transformer arcing increases to a point that the plant is in danger cQamence a shutdown.
5.10.6 Notify higher plant supervision of deteriorating weather conditions and plant status.
6.
SUBSEQUENT ACTION Hurricane 6.1 Monitor all flood gates for evidence of gross leakage.
6.2 Should CONVEX call for an emergency load pick-up during the storm, attempt to respond if plant conditions allow.
6.3 Monitor wind velocity on meteorological panel in the control room.
If at anytime the Unit Superintendent or his designee feels that the present environmental conditions could jeopardize the safety of the plant, he may order an orderly plant shutdown in accordance with general plant operating procedures or if he deems necessary an emergency shutdown in accordance with Emergency Procedure 502.
6.4 Af ter hurricane, tornado, and/or flooding conditions subside, inspect the station for damage and report the conditions to the Unit Superintendent or his designee who will provide instructions for further action.
Sustained Winds of Thirty (30) HPH or Greater 6.5 If storm conditions have forced load reduction, increase power when weather conditions have stabilized to within acceptable limits."
This procedure is not designed to protect against local PMP.
Advance warning of such a local event might not be available, and there would be no opportunity to place the plant in a state of standby readiness. Therefore, a procedure should be developed to ensure that all flood gates are closed and equipped with alarms.
The water level (14.0 f t as1) at which emergency procedures are to begin is too high.
Once water exceeds plant grade, several of the specified actions could be performed only with great difficulty, specifically:
5.3 Dispatch personnel to secure all loose equipment and materials, and 5.7 Increase surveillance at the intake structure.
_nklin Resear_ch Center
TER-C5257-422 At water level 14'7" mal, unprotected openings would begin to admit flood water into the plant structures. Water ins'ide the plant would inhibit the performance of subsequently required actions and would begin to fill the space between the floors and safety-related equipment. This space might be needed to store water entering the plant later from leaking flood gates or over-topping of the flood walls by waves. Flood waters pouring in through the doors could also inhibit the closing of flood gates, provided in Section 5.5.
The time required to perform the procedures is not specified. The Licensee should perform a trial of OP 514A and define the time required to perform it.
The time between PMH stillwater levels of 14.0 ft asl and 14.6 ft asl is approximately 15 min [7], and wave heights might rise in a shorter time. This does not allow for an acceptable margin of safety, and actions should be initiated at a level several feet lower.
A comparison should be made between the PMH hydrograph and the time required to implement the procedure.
An appropriate water level would allow time to perform all immediate actions (OP SidA, Section 5) before water reached plant grade.
A l
marker should be established at that level, and responsible personnel l
specified for monitoring water level and alerting the plant.
In the event of a hurricane, flooding, high winds, and heavy rain would be experienced over a wide area and could cause interruption of communication witn (I)NVEX.
Although CDNVEX may be relied on to give advance warning of a hurricane, calls every 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> between OONVEX and the station should not be necessar'y for successful completion of the emergency procedures.
l l
Item 5.2 snould specify the number of personnel required to cover all areas requiring assistance.
It is recommended that a comprehensive checklist be developed for all appropriate procedures, such as procedures 5.3 and 5.5.
f Actions to be performed and equipment to be used should be listed to prevent any misinterpretation of procedure.
All items and conditions requiring surveillance should be identified, and checklists should include the titles or names of personnel to be informed of plant conditions and status of completion of all tasks.
_nklin Rese_ arch Center
TER-C5257-422 Actions should be developed and specified in Item 6.1 for gross leakage at a flood gate.
3.3.4 Conclusion A procedure should be developed to ensure that flood doors are closed at all times to protect against local PMP.
A lower water level than presently specified should be used as an initiating event in OP 514A.
Other modifica-tions described aoove should be Laplemented.
A trial run of the procedure should be exercised to identify any other problems that might exist.
Resolution of some items may be achieved during integrated assessment with the use of technical specifications.
3.4 SAFETY-RELATED WATER SUPPLY (SEP 'IOPIC II-3.C) 3.4.1 Tbpic Background This topic reviews the acceptability of a particular feature of the cooling water system, namely, the ultimate heat sink (UBS).
The review is based on current criteria contained in Regulatory Guide 1.27, Rev. 2, which is l
an interpretation of General Design Criterion (GDC) 44, " Cooling Water," and
(
GDC 2, " Design Bases for Protect' ion Against Natural Phenomena," of 10CFR50, l
Appendix A.
GDC 44 requires, in part, that suitable redundancy of features be provided for cooling water systems to ensure that they can perform their safety function.
GDC 2 requires, in part, that structures, systems, and components important to safety be designed to withstand the effects of natural phenomena without loss of aoility to perform their safety functions.
The NRC's l
Regulatory Requirements Review Committee has stated that the requirements of Regulatory Guide 1.27 must be addressed for all backfitting operating reactors.
This guide is used in judging whether the facility design complies with current cri teria.
The UES as reviewed u. der this topic is the complex of water sources, including necessary retaining structures (e.g., a pond with its dam or a UJJJ Franklin Research Center i
A Chemen d The Frannan w
a TER-C5257-422 cooling tower supply basin), and the canals or conduits connecting the sources to the cooling water system intake structures, but excludes the intake structures themselves.
The UHS performs two principal safety functions:
(1) dissipation of residual heat af ter reactor shutdown and (2) dissipation of residual heat af ter an accident.
Availability of an adequate supply of water for the UHS is a basic requirement for any nuclear power plant.
Since there are various methods of satisfying the requirement, UHS designs tend to be unique to each nuclear plant, depending upon its particular geographical location.
Regulatory Guide 1.27 provides UHS examples that the NRC staff has found acceptable.
The UBS must be able to dissipate the maximum possible total heat accumula-tion in the plant, including the effects of a LOCA under the worst combination of adverse environmental conditions.
The maximum tolerable temperature of an UHS such as a cooling pond may significantly limit its ability to dissipate the heat load following a LOCA or plant shutdown, whereas, for a UHS such as a large lake, river, or ocean, iaximum temperature may not be a significant concern.
Because of the importance of the UHS, it should be able to perform its safety function during and following the most severe natural phenomena or accidents postulated at the site.
In addition, the UBS safety functions should be ensured during other applicable site-related events that may be caused by less severe natural phenomena and accidents in reasonable combination.
l 3.4.2 Topic Review Criteria The criteria by which the UHS was evaluated in this topic review are taken from Regulatory Guide 1.27, " Ultimate Heat Sink for Nuclear Power Plants."
l Regulatory Guide 1.27 criteria are as follows:
"1.
The ultimate heat sink should be capable of providing sufficient cooling for at least 30 days (a) to permit simultaneous safe shutdown and cooldown of all nuclear reactor units that it serves and to maintain,them in a safe shutdown condition, and (b) in the event of an accident in one unit, to limit the effects of that accident safely, to permit simultaneous and safe shutdown of the remaining '
Ubbhranklin Rese_ arch Center
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TER-C5257-422 units, and to maintain them in a safe shutdown condition.
Procedures for ensuring a continued capability after 30 days should be available.
2.
The ultimate heat sink cczaplex, whether composed of single or multiple water sources, should be capable of withstanding, without loss of the sink safety functions specified in regulatory position 1, the following events:
a.
the most severe natural phenomena expected at the site, with appropriate ambient conditions, but with no two or more such phenomena occurring simultaneously, b.
the site-related events (e.g., transportation accident, river diversion) that historically have occurred or that may occur during the plant lifetime, c.
reasonably probable combinations of less severe natural phenomena and/or site-related events, d.
a single failure of manmade structural features.
3.
The ultimate heat sink should consist of at least two sources of water, including, their retaining structures, each with the capability to perform the s'fety functions specified in regulatory position 1, a
unless it can be demonstrated that there is an extremely low probability of losing the capability of a single source.
4.
The tecnnical specifications for the plant should include provisions for actions to be taken in the event that conditions threaten partial loss of the capability of the ultimate heat sink or the plant temporarily does not satisfy regulatory positions 1 and 3 during operation."
In addition to Regulatory Guide 1.27, clarifications are contained in Standard Review Plan (SRP), Sections 2.4.11, "Iow Water Considerations," and 9.25, " Ultimate Heat Sink."
3.4.3 Evaluation The ultimate heat sink for Millstone Unit 1 is Iong Island Sound. The service water and circulating water systems draw water from Niantic Bay, which is fed from Iong Island Sound.
The intake structure is situated along Niantic Bay west of Millstone Unit 1.
The discharge structure is situated at one end of a quarry to the southeast of Millstone Unit 1.
The discharges from Units 1 A branklin Research Center A on=.an am. r n n %
TER-C5257-422 and 2 flow into the quarry, which is connected to Niantic Bay by a discharge ch annel.
In Reference 5, NNECO provided a safety assessment report for SEP Topic II-3.C, Safety Related Water Supply (Ultimate Heat Sink).
An evaluation of NNECO's assessment of the Millstone Unit 1 UBS against each of the review criteria is provided in the following paragraphs.
Critericn 1 of Regulatory Guide 1.27 was established for heat sinks where the supply may be limited and/or the temperature of plant intake water from the heat sink may become critical.
NNECO stated that, due to the type, size, and location of the water supply, the ability of the UHS to dissipate the total essential station heat load, the effect of environmental conditions on the capability of the UBS to furnish the required quantities of cooling water for extended periods of time af ter shutdown, and the sharing of cooling water with other units do not require further consideration. NNECO's assessment that the UHS is sufficiently large that the supply and temperature of the intake water will not become criticai is acceptable.
Criterion 2 of Regulatory Guide 1.27 was established to ensure that the l
heat sink function would not be lost due to natural phenomena, site-related events, or a single failure of manmade structural features.
NNECO indicated that the occurrence of natural events that may reduce or limit the availability of the cooling supply is not applicable at Millstone Unit 1.
The effect of earthquakes on Niantic Bay and Long Island Sound is not considered to pose a signifi' cant threat to the availability of the water source. Other natural phenomena such as tornados and floods do not endanger the water source.
The minimum low water level at the intake structure resulting from the occurrence of a PMH oriented so as to cause maximum depression of the water surface was reported in Reference 9 to be -6.3 feet asl.
NNECO has indicated that both the service water pumps and the emergency service water pumps are designed to
- c. c operate at a minimum of '-TdL feet asl.
Icing is not considered a threat to the water source at Millstone Unit 1.
Warm water recirculation is provided in the front of the intake structure to prevent the buildup of frazil ice during the winter.
The effects of site-related events (e.g., a transportation
_nkDn Research Center
o TER-C5257-422 accidient) are not considered a threat to the availability of the Millctone Unit 1 water source.
In addition, no singl'e failure of any manmade structure will adversely affect the UHS.
Based on this discussion, it can be concluded that the UHS at Millstone Unit 1 complies with Criterion 2.
Criterion 3 of Regulatory Guide 1.27 was established to provide a high level of assurance that a plant's UHS would be available when needed.
Specifically, the Guide is concerned that, for once-through cooling systems, there should be at least two aqueducts connecting the source with the intake structure and two discharge aqueducts to carry the cooling water away to preclude flooding. At Millstone Unit 1, the intake structure is located along Niantic Bay, the discharge structure empties into a quarry, and aqueducts are not used.
The UHS at Millstone Unit 1 complies with Criterion 3 in that the probability of losing the capability of Niantic Bay and Long Island Sound to supply the intake structure and to accommodate the discharge is extremely low.
Criterion 4 requires that the plant Technical Specifications include provisions for actions toI be taken in the event that conditions threaten partial loss of the UHS.
This criterion was established to ensure that plant technical specifications specify that the plant should be placed in a safe l
condition or other provisions should be implemented if a condition exists which threatens the availability of the UHS.
An example of such a condition would be a severe flood, which would japardize a UBS dike or retaining structure, a severe drought with the potential to reduce the capacity of. a cooling pond, or severe river icing conditions, which could preclude or inhibit the flow of water for a once-through cooling system.
In each of these situations, technical specifications requiring the plant to be placed in a safe condition I
or implementation of procedures to mitigate the consequences of a threatened partial loss of the UHS would be prudent.
Since Millstone Unit 1 is not susceptible to a partial loss of the UHS, technical specifications addressing such a concern are not required.
Tb ensure that the ultimate heat sink is available to the plant, the intake structure should be analyzed for structural integrity.
Loading configurations to be considered are roof ponding during PMP, loading
_nklin Research._ Center
a TER-C5257-422 conditions enumerated in Topic II-3.B which occur during PMB, and the combination of groundwater elevation to plant grade and a seismic event.
Topic III-3. A, Effects of High Water Level on Structures, and the Integrated Assessment are the proper framework for these analyses.
3.4.4 Conclusion The following is a summary of the degree of conformance of the Millstone UHS to the criteria of Regulatory Guide 1.27:
Criterion 1 - complies with no exception or clarifications Criterion 2 - complies with no exceptions or clarifications Criterion 3 - complies with no exceptions or clarifications Criterion 4 - not applicable.
In summary, NNECO's conclusion "that an appropriate supply of cooling water during normal and emergency shutdown procedures will be assured," is justified. The UHS at Millstone Unit 1 is a dependable design that complies with Regulatory Guide 1.27.
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ODNCLUSI0NS 4.1 FID0 DING POTENTIAL The Millstone site is not " flood dry," i.e.,
the site is shown to be inundated by a probable maximum flood (PMF) event and consequently must be protected by structural or other measures (such as emergency procedures). The effects of PMF from a hurricane and local probable maximum precipitation (PMP) are significant.
Groundwater fluctuations up to plant grade (14.5 feet asl) should be considered in further evaluations of safety-related structures (SEP Topic III-3.A, Ef fects of High Water Level on Structures).
The initial rise and tide values used to compute the 16-foot mal storm surge in the Licensee's PMH study (19] are not in compliance with the require-ments of Regulatory Guide 1.59 or ANSI N170-1976.
PMH stillwater level is 18.44 feet ms1.
The Licensee's PMH study includes a discussion of the effects of an increased stillwater level to 19.17 feet asl, but no analysis of wave runup is included in the study. This does not fulfill the requirements of Regulatory Guide 1.59 (12] and ANSI N170-1976. [13 ].
An analysis has been performed for wave effects at the PMH stillwater level, including the effects of (1) a clapotis'at the flood wall and (2) waves that do not break before they reach the flood wall.
Loading and wave height on safety-related structures both far exceed the design basis; however, the design basis clapotis for the intake structure has been determineo to be conservative.
The Licensee should perform a structural analysis of tne flood walls to determine wnether they can withstand the dynamic and static forces caused by waves which would act on the walls during the surge.
This analysis is included under SEP Topic III-3.A, Effects of High Water Level on Structures.
During PHP, the roof drains could prevent water from ponding on the roofs of safety-related structures beyond the levels those roofs can support.
nidin Rese
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TER-CS257-422 Structural modifications are recommended.
The roof drains should be considered safety-related water control structures. Their inspection should be addressed under SEP Topic III-3.C.
4.2 EMERGENCY PROCEDURE AND TECHNICAL SPECIFICATIONS The Millstone flood emergency procedure OP 514A outlines a plan for maintaining control of critical safety operations; however, the procedure is deficient in its present form.
The efficient execution of emergency procedures will be impaired because inadequate direction is provided.
There are presently no plant technical specifications which incorporate flood emergency procedures.
4.3 SAFETY-RELATED WATER SUPPLY NNECO's conclusion "that an appropriate supply of cooling water during normal and emergency shutdown procedures will be assured" is justified.
The UHS at Millstone Unit 1 is a dependable design that complies with Regulatory Guice 1.27.
! 4 b) Franklin Research Center w ao m remen u.ama
e TER-C5257-422 5.
REFERENCES 1.
Systematic Evaluation Program (SEP) Owners Group Letter to D. Eisenhut (NRC)
January 14, 1981 2.
W. G. Counsil (NNECO)
Letter D. M. Crutchfield (NRC)
Subject:
Transmittal of SEP Topic II-3.A June 25, 1981 3.
W. G. Counsil (NNECO)
Letter D. M. Crutchfield (NRC)
Subject:
Transmittal of SEP Topic II-3.B June 26, 1981 4.
W. G. Counsil (NNECO)
Intter D. M. Crutchfield (NRC)
Subject:
Transmittal of SEP Topic II-3.B.1 June 25, 1981 5.
W. G. Counsil (NNECO)
Letter D. M. CrutchfiLeld (NRC)
Subject:
Transmittal of SEP Topic II-3.C April 28, 1981 6.
W. G. Counsil (NNECO)
Letter to D. M. Crutchfield (NRC)
Subject:
Transmittal of Mditional Information on SEP Topic II-3.A November 20, 1981 7.
W. G. Counsil (NNECO)
Lettier D. M. Crutchfield (NRC) t l
Subject:
Transmittal of Mditional Information on SEP Topic II-3.B 1
November 19, 1981 8.
W. G. Counsil (NNECO)
Letter D. M. Crutchfield (NRC)
Subject:
Transmittal of Mditional Information on SEP Topic II-3.B.1 November 19, 1981 9.
W. G. Counsil (NNEQ)
Letter D. M. Crutchfield (NRC)
Subject:
Transmittal of Mditional Information on SEP Topic II-3.C November 19, 1981 10.
M. Bain (NNE)
Mdendum (Draf t) to SEP Topic II-3.B, Millstone Unit 1 February 12, 1982 nklin Research Center A Oneman of The Fremtn meneme
e TER-C5257-422 11.
- Scherrer, J.,
Roberts, S.
(FRC), Persinko, D.
( NRC), Bain, M. and Biboy, J.
(NNE)
Site Visit Report, Millstone Unit 1 March 5, 1982 2.
NRC Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants, LWR Edition July 1981 NUREG-0800 13.
NRC Ultimate Heat Sink for Nuclear Power Plants Revision 2 January 1976 Regulatory Guide 1.27 14.
NRC Design Basis Floods for Nuclear Power Plants Revision 2, August 1977 Regulatory Guide 1.59 15.
NRC Flood Protection, for Nuclear Power Plants Revision 1 September 1976
't Regulatory Guide 1.102 16.
American National Standards Institute Standards for Determining Design Basis Flooding at Power Reactor Sites New Yor k:
1976 N170-1976 17.
Ebasco Services, Inc.
Millstone Nuclear Power Station Unit 1 Drawings No Date 25202-10003 Plot Plan 25202-11005 Plant Area Grading and Drainage - Plan 25202-11009 Plant Road - Plan and Sections l
25202-11020 Roof Level Plans Architectural Plumbing l
25202-11023 Wall Sections - Sheet 1 25202-11024 Wall Sections - Sheet 2 25202-11026 Miscellaneous - Sheet 1 25202-11031 Office Area Details - Sheet 2 25202-11037-11040 Circulating Water System Intake Structure Mas. Sheets 1-4 25202-51005 Reactor Building Roof and Crane Runway - Framing l
25202-54008 Flood Gates and Miscellaneous I
l nklin Research Center A Onneson d The Fw insense
=
TER-C5257-422 18.
Millstone Nuclear Power Station Unit 2 Final Safety Analysis Deport (FS AR)
Section 2.5 Amendment 15 August 31, 1973 19.
Millstone Nuclear Power Station Unit 3 Preliminary Safety Analysis Report (PSAR)
Sections 2.1.4.2, 2.3, 2.4, 2.5.1.2.3 and -4, 2.5.4.6.4 through -15, and
- 9. 2.6.5 through -8 Amendment 20 April 5, 1974 20.
United States Department of the Interior Geology and Hydrology of the Proposed Millstone Nuclear Power Reactor Site New London County, Connecticut Geological Survey l
21.
The Millstone Point Company, Subsidiary of Northeast Utilities Millstone Nuclear Power Station Unit 3 Drawings Stone & Webster Engineering Corporation, No Date 25212-10001 Site Plan 25212-11000 Station Plan 25212-11008 Finished Grading, Roads and Walkways - Sheet 1 j
l 25212-11009 Finished Grading, Roads and Walkways - Sheet 2 l
25212-11040 Station Plan 25212-25001 Yard Storm & Sanitary Sewers - Sheet 1 23212-25001 Ya. ' Storm & Sanitary Sewers - Sheet 2 22.'
Millstone Nuclear Power Station Unit 1 Final Safety Analysis Report (FSAR)
Sections 2 and 4 April 8, 1968 l
23.
J. T. Riedel, J. F. Appleby, and R. W. Schloemer Seasonal Variation of the Probable Maximum Precipitation East of the 105th Meridan for Areas from 10 to 1000 Square Miles and Duration of 6, 12, 24 and 48 Hours l
Hydrometeorological Report No. 33 U.S. Department of Commerce Weather uureau April 1956 24.
Bureau of Reclamation, U.S. Department of the Interior l
" Design of Small Dams" 1977 25.
Millstone Nuclear Power Station Unit 2 Drawings 25203 - 10005 Plot Plan 25203 - 10008 Sheet 745 Drainage Plan - Area East Between Units 1 and 2 25203 - 10008 Sheets 58542-44 Site Plan "As-Built" 25203 - 113C3 Paving, Drainage and Fencing Plan and Details 25203 - 11006 Railroad Plan 25203 - 11007 Railroad Profiles and Details nidin Research
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Millstone Nucleaf Power S'iEion Unit 4 + s;9 Monthly Flood Gate Check SP682.1
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July 14, 1977 t
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U.S. Army Coascal Engineering Researdh Center '
Shore Protection Manual 1977
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3 APPENDIX A o
CLAPOTIS DURING PROBABLE MAXIMUM SURGE i
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TER-C5257-422 APPENDIX A - CLAPOTIS DURING PROBABLE MAXIMIM SURGE The following analysis is based on a maximum surge elevation of 18.11 ft mal.
The area between the plant and the quarry has been filled, with the high point graded to elevation 14.5 ft and the low point to 14.0 ft.
Assuming that the elevation at the bottom of the reinforced concrete wall is +14.5 f t and the top is +19.0 f t, a standing wave could develop during maximum storm surge periods.
The wave height that would occur is the sum of the incident wave height, H and the reflected wave height, H.
If re le tion is perfect g
r and complete, the amplitude of the wave reflected by the structure would be the same as the incident wave.
Therefore, a maximum clapotis of 2 H is g
possible.
The reflection coefficient (defined as X = H /H ) is dependent r
g on the wave and wall characteristics.
Parameters such as geometry, wall roughness, wave steepness, and wave height to depth ratios are all influencing factors.
For the Millstone seawall, a reflection coefficient X of 0.9 is assumed due to the lont) fronting slope with natural roughness.
For a surge level of +17.5 ft, the following parameters are given:
Maximum non-breaking wave height = 0.78 x (17.5-14.5) = 2.3 ft (say 2.0 ft)
(depth limited)
Wave period = 4.6 sec [22]
Depth at structure = 17.5 - 14.5 = 3 ft Reflection coefficient = 0.9.
The height of the free water surface above the bottom for the wave crest j
and trough can be calculated using the procedure given in the Shore Protection j
Manual, volume II, pages 7-138 to 7-14 9.
The mean water level at the wall l
above stillwater level can be determined by using Figure 7-72 of the Shore Protection Manual [27].
H /d = 2.0/3 = 0.67 H /T = 2.0/(4.6)
= 0.95 g
i I
Therefore, h /H = 0.88 from Figure 7-72 nklin Research Center
TER-C5257-422 or h = 0.88 x 2 = 1.76 ft.
The height of the clapotis crest above the bottom is given by Eq. 7-71
[27]. That is:
yc = d + ho + [(1 + X)/2] x Hi yc = 3 + 1.76 + [(1 + 0.9) /2] x 2.0 = 6.7 f t.
The elevation of the clapotis crest is therefore 14.5 + 6.7 = +21.2 ft as1.
This indicates that the southeast wall could be overtopped by approximately 2.2 ft.
The height of the clapotis trough above the bottom is given by Eq. 7-71
[27] :
yt = d + ho - [(1 + X)/2] x Hi yt = 3 + 1.7 6 - (1 + 0.9/ 2) x 2 = 2.9 ft.
r The elevation of the clapotis trough is 14.5 + 2.9 = +17.4 ft mal.
Calculations of clapotis crest and trough elevations are shown in the following table.
Tabulation of Clapotis Crest and Trougn Elevations l
Clapotis Surge Crest Trough Overtopping 2
H /d H /T ho/Hi ho Yc Yt Elev.
Elev.
Elev.
Hi d
i i
+18.5 2.6 4.0 0.65 0.123 0.81 2.11 8.6 3.6 23.1 18.1 Yes
+4.1
+18.11 2.35 3.61 0.65 0.111 0.83 1.95 7.79 3.33 22.3 17.83 Yes
+3.3
+18.0 2.3 3.5 0.65 0.108 0.83 1.91 7.6 3.25 22.1 17.7 Yes
+3.1
+17.5 2.0 3.0 0.67 0.095 0.88 1.76 6.7 2.9 21.2 17.4 Yes
+2.2
+17.0 1.7 2.5 0.68 0.08 0.90 1.53 5.6
- 2. 4
.20.1 16.9 Yes
+1.1
+16.5 1.3 2.0 0.65 0.061 0.92 1.20 4.4 2.0 18.9 16.5 No
-0.1 This analysis indicates that overtopping of the southeast wall will commence at a surge elevation of approximately +16.5 f t.
This condition will exist for an estimated 210 minutes [19].
It is recommended that the Licensee consider remedial measures to eliminate probable overtopping of the southeast wall during maximum storm surge.
Several measures which may be used to eliminate the overtopping:
nklin Research Center
TER-C5257-422 o increase the existing wall height o add a splash guard on the wall o Place a rubble mound at the base of the wall to decrease the reflection.
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