ML19283B690
| ML19283B690 | |
| Person / Time | |
|---|---|
| Site: | Yankee Rowe |
| Issue date: | 01/29/1979 |
| From: | Cardone A Office of Nuclear Reactor Regulation |
| To: | Stepp J Office of Nuclear Reactor Regulation |
| References | |
| TASK-02-04, TASK-02-04.A, TASK-02-04.B, TASK-02-04.C, TASK-02-04.D, TASK-02-04.E, TASK-02-04.F, TASK-2-4, TASK-2-4.A, TASK-2-4.B, TASK-2-4.C, TASK-2-4.D, TASK-2-4.E, TASK-2-4.F, TASK-RR NUDOCS 7903060609 | |
| Download: ML19283B690 (5) | |
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e JAN 2 S 1579 MEMORANDUM FOR:
J. C. Stepp, Chief Geosciences Branch, DSE THRU:
R. E. Jackson, Leader Geolcgy & Seismology Section Geosciences Branch, DSE FROM:
A. T. Cardone Geology & Seismology Section Geosciences Branch, DSE
SUBJECT:
STATUS OF REVIEW - SYSTEMATIC EVALUATION PROGRAM, YANKEE ROWE NUCLEAR POWER PLANT Material Reviewed I have reviewed the license application entitled " Yankee Nuclear Power Station FSAR, (Yankee Atomic Electric Co., Westboro, Mass.
USA) January 3, 1974" and an interim report entitled " Geology and Seismology, Yankee Rowe Nuclear Power Plant," dated October 13, 1978 and prepared by Weston Geophysical Corporation.
I also reviewed three dam inspection reports on the New England Power Company Deerfield River Project. Two of the reports dated September 1968 and 1978, were prepared by Chas T. Main, Inc., Boston, Mass-achusetts in compliance with the Federal Energy Regulatory Commission requirements. The third report, " Yankee Nuclear Station Probable Maximum Flood Analysis" by Stephen C. Donet was prepared July 1977 for Yankee Atomic Electric Company.
Site Visit On November 8, 1978, I visited the Yankee plant and toured the site area, the Sherman dam, and the Harriman dam.
I met with representatives of Yankee Atomic Electric Company and their consultant Weston Geophysical Company to discuss the geological and geo~ technical engineering aspects of the site and the dams, and to inspect the safety related nuclear plant structures for evidence'of excessive stress. My Disit focused on the following topics:
1.
Geology of the site 2.
Faulting Investigations of the site area b
790306 C66
JnN "C v3 J. C. Stepp The licensee indicated that the safety related plant structures are founded en the compact glacial till which has a shear wave velocity of 2,200 feet-per-second.
The shear wave velocity of the soils will be verifiei and the engineering properties of the soil and rocP strata will be provided at the conclusion of the Weston seismic refraction survey which was in progress at the time of my visit. The depth to bedrock at the plant site and under the Sherman dam embankment will be determined from the Weston seismic profiling.
We explained to the licensee that this information will be required for our evaluation of the site response spectra and for a stabili*.y analysis of the Sherman and Harriman dams.
Slope Stability I was informed at the site visit that glacial material up to 100 feet in thickness was depcsited on the slopes flanking the reservoirs.
There is a possibility that a gravity slide,of the Vaiont Dam. Italy variety,of these deposits into the reservoit could create a hazard to the plant. The probability of this occuring is small, ho.- cvcr, the licensee should make cn inspection for evidence of creep or tension cracks to be assurred incc Lue sliding of icp; dcposits will not occur or that the slide vill not cause overtopping of the dams.
A. T. Cardone Geosciences Branch Division of Site Safety and Environmental Analysis cc:
R. Denise D. Eisenhut D. Davis C. Hofmayer L. Heller A. Burger T. Cardone PDR
JPN 2 0 nn
- The stability analyses were performed using a computer program bascd on the simplified Bishop =cthod, using cylindrical failure surfaces and ascumed effective stress strength parameters. Where the simplified Bishop method could not be used, the wedge method by H. Bolton Seed presented in a paper to the ASCE Journal of the Soil Mechanics and Foundation Division, Vol. 93, No. SM4, July 1967 was adopted.
In the analysis it was assumed that the glacial till, which was apparently used for construction of the impervious embankment dams, are similar in character throughout the valley.
Since no existing soil test data could be located for any of the embankment dams, it was decided to,.dopt the results of soil tests run for the Bear Swamp Pumped Storage Project (another Federal Power Commission Project) as being typical of the glacial till. On this basis the typical effective stress strength parameters were 35 degrees internal friction angle and zero cohesion. These values were adopted for both the shell and core materials in the embankments. The unit weights were also assumed for the c=bankment fill naterials, the overburden and the rip-rap.
The earthquake loading was assumed at 0.05g or as a resulting horizontal forcc equal to 0.05 times the weight of the sliding mass of the embankment, applied at its center of gravity.
In addition the downstream phreatic surface which is a major factor affecting the stability was estimated.
The combination of low computed factors of safety for the assumed loading conditions and the lack of reliable soil property data result, in my opinion, is insufficient assurance that the Sherman and/or Harriman dams will not f ail and thus create a hazard to the nuclear plant.
I recommend that additional dam stability studies be performed using soil properties measured in the field and from representative soil samples obtained from the dam embank-ments and tested in the laboratory. Because of the material type used in these dams, the analyses must account for the effect of cyclic motion of the Safe Shutdown Earthquake on soil strength parameters. They should reflect standard analytic procedures acceptable to NRC as described in Reg. Guide 1.132.
Settlement of Structures The safety related structures were inspected for indications of settlement of foundations. None were observed. The licensee indicated that 80% of the weight of the containment building was in place for one year prior to the connection of piping, thus the bulk of the settlement would have occurred in the interim. The licensee is searching the files for any settlement records.
JAN 2 9 39 J. C. Stepp.
upstream of the power plant is the Harriman Dam, another in a series of dams along the Deerfield River Valley.
The Harriman Dam embankment also consists of semi-hydraulic fill and is approxi-mately 196 feet in height.
It was built in 1924 by the New England Power Company.
The 1977 report " Yankee Nuclear Station Probable Maximum Flood Analysis" presents the results of hydrologic studies uade to determine the Probable !!aximum Flood (PMF) which would occur at the plant site.
In conjunction with the hydrologic studies, stability analyses were made of the embankment structures.
The flood analysis indicated that the PMF through the Harriman reser-voir results in 0.7 feet overtopping of the embankment dam.
The PMF through the Sherman reservoir results in 0.7 feet of freeboard to the dam crest. The report states that the Harriman reservoir is not breached as a result of 0.7 feet overtopping.
Staff hydrologists are currently evaluating the effects of a PMF on the dams, and at the site.
In the stability analyscs the loading cases analyzed for the embankment dam were:
Case I -
Downstream slope for Maximum Normal Operating Pool Case II -
Case I with 0.05g horizontal carthquake force Case III - Upstream slope for Rapid Drawdowns Case IV -
Case III with 0.05g horizontal earthquake force Case V -
Downstream slope for project flood.
The computed factors of safety against f ailure were:
Sherman Dam Harriman Dam Case I 1.23 1.40 Case II 1.03 1.15 Case III 1.38 1.59 Case IV 1.14 1.30 Case V 1.20 1.32
JAN 'r3 U-
J. C. Stepp -
3.
Dam Integrity 4.
Scttlement of Structures 5.
Slope Stability A presentation on the regional and local geology was made by J.
Rand of Weston Geophysical Company, which summarized the interim report by the Weston Geophysical Company report mentioned above.
Geology and Faulting Investigations The FSAR contained a section (2.5) on Geology and Seismology consisting of less than two pages of text and two figures contain-ing the logs of borings and illustrations of typical soils found at the plant site. The logs indicate that the soils are glacial tills consisting primarily of compact medium to fine sands with gravel end boulders which vere deposited by glaciers and later overriden by them.
The regional and site geology is not addressed in the FSAR.
The interim report, " Geology and Seismology, Yankee Rowe Nuclear Power Plant" is a significant effort undertaken by the licensee to satisfy the need for information, which will provide a basis for our evaluation of the geologic and seismic hazards at Yankee Rowe.
It appears to adequately address the regional and site geology, however, the site soil properties and compressional and shear wave velocitics are based on 1956 data which is question-able. The licensee is developing new soils engineering properties and shear wave velocities for input to the seismic response spectra for the site. The report provideS a soil / rock profile and describes the topography and surficial geology in apparently sufficient de-tail for input to the development of site response spectra. My comments on the geologic model described in the report will be provided with the siesmological comments in a later memo.
Dam Intecrity The power plant is located in the Deerfield River Valley at the southeast abutment of the Sherman Dam. This dam, a semi-hydraulic embankment type, was constructed by the New England Pouer Company in 1927, and has a maximum height of 110 feet. All cooling water, normal operating and emergency service water, is drawn from the pond formed by the Sherman Dam.
Approximately 6 miles