ML20213E697
| ML20213E697 | |
| Person / Time | |
|---|---|
| Site: | Diablo Canyon  |
| Issue date: | 12/15/1983 |
| From: | Heller L Office of Nuclear Reactor Regulation |
| To: | Kuo P Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20213E357 | List: |
| References | |
| FOIA-86-151 NUDOCS 8312230075 | |
| Download: ML20213E697 (5) | |
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UNITED STATES '
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DEC 151983 MEMORANDUM FOR: Pao-Tsin Kuoi.._Section Leader Structural Engineering Section B Structural and-Geotechnical Engineering Branch Division of Engineering THRU:
George Lear, Chief k
Structural and Geotechnical Engineering Branch gy k
Division of Engineering FROM:
Lyman W. Heller, Leader i.
Geotechnical Engineering Section Structural and Geotechnical Engineering Branch Division of Engineering 5
SUBJECT:
GEOTECHNICAL INPUT FOR SUPPLEMENTAL SAFETY EVALUATION REPORT #20 - INDEPENDENT.
DESIGN VERIFICATION PROGRAM T
l Plant Name: Diablo Canyon Nuclear Power Plant, Unit 1 i
Applicant: Pacific Gas and Electric j
Licensing Stage: Reinstatement of low powur lice 6se Docket Number:
50-275 i
j Responsible Branch:
LB-3, H. Schierling, LPM j
Status: Review completed l
Documents Reviewed:
1.
Interim Technical Report, Diablo Canyon Unit 1, Independent Design Verification Program,. Verification i
of HLA Soils Work - ITR #68, Revision 1, by Robert L. Cloud Associates Inc., October 4 '1983.
j-HLA memo by Steve Korbay, Intake Structure Excavation 2.
Inspection, February 17, 1972.
(RLCAFileNo.
P105-4-449-128).
)
3.
HLA memo to file by Steve Korbay, Site Inspection.
Intake Structure, Diablo Canyon, March 2, 1972.
(RLCA File No. P 105-4-449-129).
i 4.
HLA, memo to file by Henry Taylor, PG&E, Diablo Canyon file, Visit on March 3,1972. Memo dated i
March 16, 1972.
(RLCA File No. P 105-4-449-130).
5.
Safety Evaluation Report, related to the operation of Diablo Canyon Nuclear Power Plant, Unit 1 Supplement No. le, NUREG-0675, August 1983.
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Pao-Tsin Kuo DEC 151983 Attached is the geotechnical input for Section 3.5 of the subject SSER #20 based on our review of the documents referenced above (References 1 through 4), several telephone conversations with Robert L. Cloud Associates (RLCA) and an audit of references (2, 3 and 4) by Dr. C. Costantino of Brookhaven National Laboratory on October 25, 1983. RLCA prepared ITR #68 in response to the staff's concerns stated in Section 3.5.1 of SSER No.18 (Reference 5).
The attachment presents our evaluation of the sliding stability of the intake structure.
We concur with RLCA that the intake structure is stable under Hosgri loadings and meets the licensing criteria.
In arriving at this conclusion, we used the HLA geologist's field visit memos (References 2, 3 and 4) to judge that the shear strength of the bedrock is at least 8.3 ksf; whereas, the shear strength measured in a laboratory test on a weathered tuff sample was only 7.5 ksf. The higher shear strength was justified using the qualitative infomation documented in the geologist's memos. The staff should require that RLCA docket references 2, 3 and 4.
During our telephone conversations, RLCA stated that they will be issuing an errata to ITR #68, (Reference 1);
the staff should also require that the errata to Reference 1 be docketed.
This SSER was prepared by Banad Jagannath, Geotechnical Engineering Section (49-28368) and incorporates comments from NRC's consultant, Brookhaven National Labcratory.
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-f Lyman W. Heller, Leader Geotechnical Engineering Section Structural and Geotechnical Engineering Branch Division of Engineering
Enclosure:
As stated cc: w/o enclosure w/c..losure R. Vollmer J. Knight D. Eisenhut G. Lear L. Heller H. Polk H. Schierling B. Jagannath
Diablo Canyon Nuclear Power Plant, Unit 1 Docket No. 50-275 g
SSER Input - Geotechnical Engineering Prepared by: Banad Jagannath, SGEB, DE i
l Section 3.5 summarizes the staff's geotechnical engineering review of Diablo j
l Canyon Nuclear Power Plant, Unit 1 (DCHPP), as presented in ITR #68 prepared l
by Robert L. Cloud Associates Inc.(RLCA). This ITR #68 was prepared in response to staff's<cmments presented in Section 3.5.1 of SSER #18 (NUREG 0675). The staff had the benefit of a technical audit of some referenced material and telephone discussions with RLCA. The sliding stability of the intake structure has been evaluated against the design criteria used in the safety' evaluation of DCNPP safety evaluation report and its supplements (SSER #'l through 8).
l 3.5 Other Seismic Desien Verification Tooics Open Item 25:
Intake Structure Lateral Forces The staff stated in SSER 18 (page C.3-86) that the total lateral forces, the total resistance to sliding and the factor of safety againsti sliding of the intake structure should be fully evaluated.
In Board Notification 83-179, the staff provided the status, basis and schedule for the resolution of the concern as fellcws:
"The staff concern was that the total lateral forces on the intake structure were not completely evaluated.
These forces consist of lateral static and dynamic earth pressure, hydrodynamic pressures and seismic forcers.
The structure is keyed into the unoerlying rock material and sliding at the structure rock interface is of concern.
The staff is concerned about sliding occurring in possible clay seems in the rock foundation.
Some additional boring data have becer.e available that can be used to address these concerns.
The 12/14/83 C.3-23 DIABLO CANYON SSER 2.J SEC C.3 n
IDVP will use this data in the evaluation and r'eview the findings and report them in a revision to ITR 40.
It is expected that the results i
l of this additional investigation will show the intake structure is stable against sliding. Any modifications which may be necessary t
will not likely affect syitems or components needed for fuel load or otherwiseinterferewithactivities'associatedwithfodes.5and6.
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Therefore it is acceptable to the staff to defer the resolution of the factor of safety against sliding to Step 2."
The staff concern was that the IDVP had not" evaluated the sliding stability of the intake structure as reported in Interim Technical Report ITR-40 M
- L.Me 311% b i nance," $ch--9r-198-3.
The structure is keyed into the underlying bedrock 'a'nW the staff was concerned about the structure sliding along either the structure-r.ock interface or along a possible clay seam within the bedrock.
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_ __ In response to the staff comments, the IOVP issued ITR-68,
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('erification of HLA Soils Work [uev.0[5eptember 20, 1983) and Rev. 1, p
October 4, 1983.
This report addresses the geotechnical concerns stated in Section 3.5.1 of SSER 18.
The staff has completed its review of ITR-63.
During an audit on October 25-26, 1933 in San Francisco the staff also reviewed three field visit memos (1972) by r
the HLA geologists which document the condition of the bedrocMexoosed., The k
staff performed an independent analysis of the sliding of the intake structure and concurs with the IDVP that the shear strength of rock re. quired to result in a minimum factor of safety of 1.1 against sliding of the intake structure is 8.3 ksf.
This is only 10 percent higher than the 7.5 ksf shear strength measured in the laboratory test on a sample of weathered tuff.
The field visit p
im si memosg d:cument the results of four Airtrac holes drilled at the bottom of the 4,-(
founcation excavations.
These did not reveal any soft zones or voids in the bedrock beneath the foundation.
Geophysical tests in these holes resulted in an average compressional wave velocity of 7000 fps.
Thememofdescribe6herock 7.
as blocky to massive, moderately hard, moderately strong tuff / shale with minor u athering.
The geologists noted that some minor blasting was necessary to
. n. u.
n,:
s
,::catethebedrockandthatthebedrockdippedsteeplytothewest.), Based
- ne above and the strength of tuf f quoted in the li,terature, the-s<taff con-c-
ciudes that the in situ shear strength of the bedrock is higher than 8.3 ksf 12/1?/33 C.3-24 DIABLO CANYON SSER 20 SEC C.3 I
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and will result in a minimum factor of ~ safety of at least 1.'1 against sliding..
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Since the bedrock dippe~d steeply to the west and the borings did not reveal any soft zones, sliding along a critically oriented clay seam within the bedrock is not a likely mode of failure. The staff therefore concurs with the IOVP that the intake structure is safe aga-t'nst sliding.
i The staff has reviewed the stability of'the intake structure against bearing and overturning modes of failure an'd concurs with the IDVP that the intake y
structure foundation is stable against bearing and overturning.
The IDVP has used the results of the structural analysis' presented in ITR-58c r b akh Structure," Rev. 11 October 1,19M its sliding analysis of the a
structure. The staff concludes that the intake structure is stable under Hosgri loadings and satisfies the. licensing criteria. The staff considers this open item resolved.
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1 12/14/33 C.3-25 OIABLO CANYON SSER 20 SEC C.3
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