ML20010C703

Final Deficiency Rept Re Lamination of Soil in Essential Raw Cooling Water Spray Pond,Initially Reported on 810204.No Significant Lamination to Cause Adverse Impact on Seepage or Structural Integrity of Liner

ML20010C703
Person / Time
Site:	Yellow Creek
Issue date:	08/11/1981
From:	Mills L TENNESSEE VALLEY AUTHORITY
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
10CFR-050.55E, 10CFR-50.55E, NUDOCS 8108200328
Download: ML20010C703 (3)

Text

-

y .

TENNESSEE VALLEY AUTHORITY '[9,'.g. f '

CH ATTANOOGA. TENNESSEE 374ot s .

400 Chestnut Street Tower II AI ' % bl hl[] 3<

August 11, 1981 .

YCRD-50-566/81-03 T '

/,

Mr. James P. O'Reilly, Director s N

[ \j' . . I ',

Office of Inspection and Enforcement c N(L J;4 i 9 gg,)

U.S. Nuclear Regulatory Commission 0._

Region II - Suite 3100 ,

101 Marietta Street y n.5 g ',,'@^'" -,

Atlanta, Georgia 30303  ?'

Dear Mr. O'Reilly:

3 YELLOW CREEK NUCLEAR PLANT UNIT 1 - LAMINATION OF SOIL IN ERCW SPRAY POND -

YCRD-50-566/81 FINAL REPORT The subject deficiency was initially reported to NRC-0IE Inspector R. W. Wright on February 4, 1981, in accordance with 10 CFR 50.55(e) as NCR YC-144. This was followed by our first interim report dated March 5, 1981. Enclosed is our final report.

If you have any questions concerning this matter, please get in touch with D. L. Lambert at FTS 857-2581.

Very truly yours, TENNESSEE VALLEY AUTHORITY l

L7 M. Mills, Manager Nuclear Regulatilon and Safety Enclosure cc: Mr. Victor Stello, Jr., Director (Enclosure)

Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, DC 20555 5 527 S

j 8108200328 810811 PDR ADOCK 05000566 S PDR An Equal Oppertunity Employer

e

• 3 .

ENCLOSURE YELLOW CREEK NGCLEAR PLANT UNIT 1 LAMINATION OF SOIL IN ERCW SPRAY POND YCRD-50-566/81-03 FINAL REPORT DESCRIPTION OF DEFICIENCY As part of TVA's construction control testing, earthfill block (undisturbed) samples are required to ba taken from Category I earthfill placement. Laminations have becn observed in several block samples taken from the earthfill liner in the unit i ERCW spray pond. Most of the laminations occurred at a depth of 1 to 3 inches from the top of the block samples. This deficiency was deemed reportable since the presence of laminations could adve?sely affect the seepage or structural integrity of the spray pond.

Laminations in the earthfill liner, were possibly caused by overcompaction, excessive speed of hauling equipment, or failing to scarify the top surface of any previously placed layer of fill.

SAFETY IMPLICATIONS The spray pond liners are designed taking into account permeability and shear strength of earthfill among other factors. Laminations may have some effect on the seepage and the shear strength of the liner. If the laminations are significant and remain uncorrected, this could cause an increase in permeability and could reduce the shear strength. This would result in additional seepage losses and reduced safety factors for the spray pond slope stability, CORRECTIVE ACTION TVA has conducted an evaluation to determine if the 1"minations would significantly affect seepage or the structural integrity of the spray pond.

Five additional block samples have been taken in the vicinity of the earlier block samples which indicated laminations. The samples and the walls of the trenches excavated to obtain the samples were inspected for laminations. In general, no significant laminations, shear planes, cracks, or weak zones were observed in the samples or the trenches. Sample 5, which was taken from the bottom liner, contained a few minor and localized zones of laminations near the top surface of the block. In addition to the unconsolidated-; ndrained (Q) and consolidated-undrained (R) triaxial shear test, this sample was selected to conduct a vertical permeability test to simulate vertical seepage through the bottom liner of the pand. Sample 8, which was taken in the slope of the pond liner contained two minor localized laminations: one at the top and the other near the bottom of the block. In L.uition to the normal Q and R shear strength testing, this sample was selected to conduct a horizontal perseability test to simulate lateral seepage through the slope liner. The test results of the additional block samples are'shown on the attached table. The horizontal and vertical permeabilities of block samples are lower than the design value indicating that there would be-less seepage or at least no adverse impact on seepage losses through the liner.

a 44 -

The apparent shear strength values for R tests are higher than the design -

value and therefore should not have an adverse impact on the slope p stability of the pond.

The effective friction angle values for both block samples are relatively higher than the design value. Sample 5 indicated slightly lower cohesion than the design value, but this should not have a significant effect on the long-term slope stability.

The Q-test friction angles are higher than the design value. Although the Q-test cohesion values are relatively lower, no significant impact on the stability is anticipated since there is an ample safety factor (= 7.45) for during construction and end of construction cases. Moreover, the liner construction is almost complete, and there is no sign of sliding or stability problems to date.

Based upon the field observations and the laboratory test results, it is concluded that there is no significant lamination to cause any adverse impact on the seepage or the structural integrity of the unit 1 spray pond liner. Therefore, no corrective potion is required on the inplace earthfill. To lessen the probability of laminations occurring in the future, TVA has included a table with recommended compaction guidelines for earthrill in TVA construction. specification N8C-882. This table lists the rollers which have been tested, the corresponding loose-lift thickness,

, and the number of roller passes which should be used in compacting the earthrill to meet the required compaction criteria.

If the surface of any previously placed layer of earthfill is too smooth, TVA also requires the surface to be scarified to create a rough contact before placing subsequent earthfill layers. This has been incorporated into TVA conatruction specification N8C-882.

This problem has not been found at other TVA nuclear olants.

l l

t l

l l

. .