ML18017A653

Discusses Suitability of Rockfill Characteristics for Main Dam Per NRC 781227 Request & Subsequent Telecon W/Oo Thompson

ML18017A653
Person / Time
Site:	Harris
Issue date:	09/05/1979
From:	Mccormick W ARMY, DEPT. OF, CORPS OF ENGINEERS
To:	Knight J Office of Nuclear Reactor Regulation
Shared Package
ML18017A652	List: ML18017A653
References
SADEN-F, NUDOCS 7910040392
Download: ML18017A653 (3)

Text

)EPARTNENT OF THE ARQY g>%bi<<b~~. South Atlantic Oivision, Corps ol Engineers 5IO Title Suilding, 30 Pryor Street, S.I.

w~. ~it pV Atlanta, Georgia 30303 SADEN-F 5 September 1979 Mr- James P. Knight Assistant Director for Engineering Division of Systems Safety Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission, Washington, D. C. 20555

Dear Mr. Knight:

Reference is made to the request in the Nuclear Regulatory Commission letter dated 27 December 1978 and subsequent telephone request by Mr.

Owen 0. Thompson of the Geosciences Branch, NRC, for assistance in evaluating the rock Harris Nuclear Power fill characteristics for the main dam of the Shearon Plant.

We have reviewed the "Report on Rock Fill Test Sections" for the main dam and our Mr. Gregory R. Baer has participated in an on-site visit to the test fills and quarry with representatives of NRC, EBASCO, and CP 6 L on 13 August 1979. The following comments are offered concern-ing the quality and characteristics of the rock fill with respect to gradation, strength and permeability. The comments were discussed by telephone with Mr. Thompson and other representatives of NRC, EBASCO, and CP g L on 17 August 1979.

The gradation curve with the minimum D5 of 3-inches presented on Figure 12 of the "Report on Rock Fill Test Section" represents the minimum acceptable gradation for the xock 'fill. Our review of the test fill fill free of report and site visit indicates that a well graded rock segregation, and meeting the minimum gradation, as well as density, can be achieved utilizing the proposed placement and compaction procedures. The requirement, however, of specifying the maximum stone size for the rock fill based on the average of the 3-dimensions for each stone is not entirely understood. It is anticipated that such a require-ment will be difficult to control during construction. The accepted practice within this agency is to specify the intermediate dimension as the maximum particle size which is directly related to the gradation.

a SADEN-F 5 September 1979 Mr; James P. Knight Results of the field permeability tests indicate a permeability of 10 cm/sec in the test fills. A permeability of this order of magnitude is normally considered free draining. Assuming the fines are uniformally distributed throughout the fill, as was the case in the test fills, and the fines are non-plastic, as sta)ed by representatives of EBASCO at the site visit, a permeability of 10 cm/sec pppears to be representative of the rock fill.

Caution should, however, be exercis'ed during construction to insure uniform distribution of .fines in the fill and to avoid the use of weathered rock containing plastic fines. Mr. Thompson has recommended that the first 3

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lifts of rock fill in the downstream section of the dam (in the valley) be limited to a maximum of 5 percent fines. Mr. Thompson also has recom-mended that field permeability tests be conducted as part of the normal-quality assurance testing program and that a minimum permeability of 10 cm/sec be required for all rock fill. Implementation of these recommenda-tions

!. should insure adequate drainage of the rock fill.

A 15-inch triaxial test, R, was conducted on the rock fill with a gradation representative of the lower gradation which will ge allowed. The results design, an effective strength the rock fill.

p'f P'f of the test show an effective strength 40.5 and no cohesion.

40 and no cohesion was assumed for It is noted in the "Report on Rock Fill Test Sections" In that, as the excavation progresses, fresher granite of coarser gradation will be encountered. Based on this fact and the fact that the gradation of the material tested was the lower limit of gradation to be used, believed that the test results are representative of the strength of the it is rock fill. It is recommended, however, that a minimum of two additional triaxial tests be conducted on representative samples of the rock fill during the early stage of construction to substantiate the design values.

It has been a pleasure for the South Atlantic Division, Corps of Engineers, to be of assistance to the Nuclear Regulatory Commission. If we can be of any further assistance or offer any further clarification on the above comments, please contact Mr. Gregory R. Baer at FTS 242-4696.

Sincerely, l(ILLIAMN. McCORMICK, P%.

Chief, Engineering Division