ML17258A901
| ML17258A901 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 03/17/1981 |
| From: | Snaider R Office of Nuclear Reactor Regulation |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML17258A902 | List: |
| References | |
| NUDOCS 8103260376 | |
| Download: ML17258A901 (9) | |
Text
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MAR 1V 198 MEMORANDUM FOR:
Dennis M. Crutchfield, Chief Operating Reactors Branch ¹5 Division of Licensing FROM:
SUBJECT:
Richard P. Snaider, Project Manager Operating Reactors Branch ¹5 Division of Licensing
SUMMARY
OF MEETING l)ITH ROCHESTER GAS AND ELECTRIC CORPORATION AND GILBERT ASSOCIATES TO DISCUSS ROCK ANCHOR DESIGN AT THE R.E.
GINNA NUCLEAR POLlER PLANT e
On Thu'rsday, February 19, 1981, members of the NRC staff met with representatives of Rochester Gas and Electric Corporation (RGSE) and Gilbert Associates (GAI) to discuss the capability of the ru',ck anchor system for the containment building at the R.E.
Ginna Nuclear Power Plant.
A list of attendees is attached as Enclosure l.
The purpose of the meeting was to reach technical resolution regarding the cause of tendon relaxation in the Ginna containment building.
The tendons and associated ro'.ck anchors serve to prestress the concrete containment in order that only compressive loads are applied to the concrete during any accident which could pressurize containment.
They also serve to resist overturning moments during seismic events.
.The Ginna facility utilizes 160 vertical tendons with rock anchors.
The tendons are spaced at approximately 2 foot centers around the circum-ference of the containment building.
These anchors are grouted into rock to approximately 34 feet below ground level of the containment building.
The tendons, each comprised of 90 tensioned wires, are attached to the rock anchors at couplings in the base of the containment building, and are approximately 113 feet in length.
The basis for the present concern which led to 'n earlier site visit and conference telephone calls, is provided in a November 30, 1979 memorandum attached as Enclosure 2.
This memorandum notes that, in
- 1979, as a result of required surveillance, the tendons were found to have lost tension in excess of that predicted to have been lost over the 40 year lifetime of the plant.
The tendons were retensioned to P
meet design requirements and an investigation was begun into the cause of the detensioning including the adequacy and capability of the
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containment building/rock anchor system.
This was the basis for the February 19, 1981 meeting.
Enclosure 3 includes the viewgraphs utilized during the presentation.
The first subject for discussion was the original design calculations versus present design calculations.
A major change is that the present calculations include the dead weight of the four foot thick concrete mat plus a postulated rock failure cone.
The strength of the rock into which the rock anchors are grouted, beyond a postulated failure cone extending from the tip of the rock anchor to the rock surface, is not taken into account.
Tables in Enclosure 3 contain comparison of the original calculations vs. current calculations and the, force and safety factor values derived from current calculations.
After substantial review and discussion of these calculations, and because the in-situ rock does have strength greater than the stress calculated.
the staff concluded that the design of the containment building is satisfactory.
The remainder of the meeting dealt with Che postulated reasons for the loss of tension in the tendons.
Substantial information is--presented in Enclosure 3. including data from original rock anchor testing using 28-wire tendons and a summary of some plausible causes previously rejected and those still under review by the licensee's consultant.
The present conclusion of RGSE and GAI is that the major pot tion of the relaxation can be attributed to the material of the tendon wires themselves.
Substantial laboratory testing of spare wires at different temperatures over several thousand hours lends credence to this conclu-sion.
Information on this testing is provided in Enclosure 3.
Extra-polation of the data points indicates that abnormal detensioning on the order of Chat experienced at Ginna can be attributed to abnormal tendon relaxation.
This is indicative of a material problem and requires increased su< veillance.
The NRC staff did not agree that it is totally attributable to such abnormal materials relaxation.
The staff remains concerned that part of the problem could be due to deformation of the rock into which the anchors are grouted.
Part of the relaxation of tension experienced during the testing of the 28-wire tendons could be attributed to rock deformation, slippage between the rock and the grout, slippage between the grout and the tendon wires, or elongation of the wires.
The staff does agree that massive catastrophic rock failure of the entire rock anchor system is extremely unlikely.
- However, a single rock anchor failure due to bond slippage or rock compression, with resultant inability of the anchor to perform its intended function, cannot be ruled out.
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the staff concluded that augmented inservice inspection would be required and that this inspection would satisfy our present concerns.
The licensee will continue its program of repair, installa-tion. calibration and daily monitoring of load cells on four tendons.
In addition, the licensee will submit.
by mid-April 1981, a description of its planned tendon surveillance program to be performed during the outage scheduled to begin in June 1981.
The staff will review the proposed program and recommend changes as appropriate, such as including the monitoring of those tendons on which the relaxation was more pronounced, if such tendons are not already included in the licensee's program.
The staff also stated that the tendon surveillance program at Ginna should be recoomenced as if the building were new, with the assumption that the June 1980 retensioning forms the initial tensioning datum point.
Thus, the June 1981 inspection will be year 1, and inspections will be required at years 3, 5, etc.
The licensee also agreed to investigate another possible phenomenon in the anchorage system, that of mechanical "hangup" of the tendon wires during tensioning, resulting in false indication of tensioning to design requirements and later relaxation to less than allowable limits.
Based upon review of the retensioning information presented by RGSE, the Staff concluded that this concern did not indicate a potential for a catastrophic failure of the containment either.
However, this phenomenon is to be investigated by RGRE and GAI and discussed with the staff prior to the June 1980 tendon testing.
Enclosures:
As stated Richard P. Snaider, Project Manager Operating Reactors Branch 85 Division of Licensing cc w/enclosures:
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MAR 17 1981 cc w/enclosures:
Harry H. Voigt, Esquire LeBoeuf, Lamb, Leiby and HacRae 1333 New Hampshire Avenue, N.
W.
Suite 1100 Washington, D. C.. 20036 Nr. Michael Slade 12 Trailwood Circle Rochester, New York 14618 Rochester Coamittee for Scientific Information Robert E. Lee, Ph.D.
P. 0. Box 5236 River Caopus Station Rochester, New York 14627 Jeffrey Cohen New York State Energy Office Swan Street Building Core 1,
Second Floor Empire State Plaza Albany, New York 12223 Director, Technical Development Programs State of New York Energy Office Agency Building 2 Empire State Plaza
- Albany, New York 12223 Rochester Public Library 115 South Avenue Rochester, New York 14604 Supervisor of the Town of Ontario 107 Ridge Road'West
- Ontario, New York 14519 Resident Inspector R. E. Ginna Plant c/o U. S.
NRC 1503 Lake Road
- Ontario, New York 14519 Ezra !. Bialik Assistant Attorney General Environmental Protection-Bureau New York State Department of Law 2 World Trade Center New York, New York 10047 Director, Criteria and Standards Division Office of Radiation Programs (ANR-460}
U-S. Environmental Protection Agency Washington, D. C.
20460 U. S. Environmental Protection Agency Region II Office ATTN:
E IS COORQ INATOR 26 Federal Plaza New York, New York 10007 Herbert Grossman, Esq.,
Chairman Atomic Safety and Licensing Board U. S. Nuclear Regulatory Coamission Washington, D. C.
20555 0 r.
Richard F. Cole Atomic Safety and Licensing Board U. S. Nuclear Regulatory Comnission Washington, D. C.
20555 Dr.
Emmeth A. Luebke Atomic Safety and Licensing Board U. S. Nuclear Regulatory Comnission Washington, D. C.
20555 Hr. Thomas B. Cochran Natural Resources Defense Council, Inc.
1725 I Street, N.
W.
Suite 600 Washington, D. C.
20006 Hr. John E.'Haier Vice President Electric and Steam Production Rochester Gas and Electric Corporation 89 East Avenue Rochester, New York 14649
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CLOSURE 1
LIST OF ATTENDEES le%
0 2l1 81 Name Dick Snaider Keith Wichman F.L. Moreadith A. Hafiz R. Smith J.F. Fulton R.C. Mecredy D. Crutchfield Kenneth H. Murray D.R. Campbell J.T.
Chen C.A. Forbes T.R. Weis Ken Herring Suresh K. Chaudhary Affiliation NRC/DL/ORB¹5 NRC/DL/DRAB Gilbert Associates, Inc.
NRC/SEP RG&E Gilbert Associates, Inc.
RGSE NRC/DL/C-ORB¹5 Gilbert Associates, Inc.
Gilbert Associates, Inc.
NRC/HGEB RGEE RGSE NRC/DL/SEPB NRC/ IE/RI