ML17256A540
| ML17256A540 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 03/08/1983 |
| From: | Crutchfield D Office of Nuclear Reactor Regulation |
| To: | Maier J ROCHESTER GAS & ELECTRIC CORP. |
| References | |
| LSO5-83-03-012, LSO5-83-3-12, NUDOCS 8303100301 | |
| Download: ML17256A540 (8) | |
Text
March 8, 1983 Docket IIo. 50-244 LS05-83-03-012 tb. John E. Maier, Vice President Electric and Steam Production Rochester Gas and Electric Corporation 89 East Avenue Rochester, Ne'er York 14649
Dear Ilr. Haier:
SUBJECT:
CONTAINMENT VESSEL TENDON EVALUATION PROGRAM DISTRIBUTION Docket NRC PDR Local PDR ORB Reading NSIC DCrutchfiel d HSmith GDick OELD ELJordan JMTaylor ACRS (10)-
SEPB J.
Chen
- 0. Rothberg Your letter dated:February l, 1982 transmitted GAI Report 2347 outlining the results of the investigation of problems relating to the containment prestressing tendons.
Our review of the r eport indicates that there is still staff concern regarding the reasons for loss of tension in the Containment Vessel Tendons.
Our comments and recommendations are contained in the enclosure.
Please provide your response Mithin 90 days of receipt of this letter.
Sincerely, Original signed by
Enclosure:
As stated cc r</enclosures:
See next page Dennis IP. Crutchfield, Chief Operating Reactors Branch 05 Division of Licensing 8303100301 830308 l
PDR ADOCK 05000244 P
PDR OFFICE/
SURNAME/
DATEf D
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<'a
ter. John E. Maier March 8, 1983 CC Harry H. Yoigt, Esquire
- LeBoeuf, Lamb, Leiby and t/acRae 1333 New Hampshire
- Avenue, N.
W.
Suite 1100 Washington, D.'.
20036 ter. tlichael Slade 12 Trailwood Circle Rochester, Hew York 14618 Ezra Bialik Assistant Attorney General Environmental Protection Bureau New York State Department of Law 2 World Trade Center Hew York, Hew York 10047 U. S. Environmental -Protection Agen'cy Region II Office ATTN:
Regional Radiation Representative 26 Federal Plaza New York, Hew York 10007 Herbert Grossman, Esq.,
Chairman Atomic Safety and Licensing Board U. S. Nuclear Regulatory Commission Washington, D. C; 20555 Ronald C. Haynes, Regional Administrator Nuclear Regulatory Commission, Region I 631 Park Avenue King of Prussia, Pennsylvania 19406 Resident Inspector R. E. Ginna Plant c/o U. S.
NRC 1503 Lake Road
- Ontario, Hew York 1'4519 Director, Bureau of Nuclear Operations State of Hew York Energy Office Agency Building 2 Empire State Plaza
. Albany,.New York 12223
'upervi sor of the To~(n of Ontario 107 Ridge Road West
- Ontario, Hew York 14519 Dr. Emmeth A. Luebke Atomic Safety and Licensing Board U. S. Nuclear Regulatory Commission Washington, D.
C.
20555 Dr. Richard F. Cole Atomic Safety and Licensing Board
.U. S. Huclear Regulatory Commission Washington, D. C.
20555
ENCLOSURE R.
E.
GINNA NUCLEAR POWER PLANT REVIEW OF CONTAINMENT VESSEL TENDON EVALUATION PROGRAM
References:
(1)
Letter from J.
- t1aier, RG&E to D. Crutchfield,
- NRC, on Ginna Tendon Evaluation
- Program, Feb.
1, 1982.
(2) f5emo from E. Jordan, IE to L. Shao, HRR, dated Nov. 30, 1979 (3)
Letter from L. White, Jr.,
RG8E to D. Ziemann,
- NRR, on Tendon Inspection and Lift-OffVerification, Dec.
12, 1979 (4)
Letter from D. Ziemann, NRR to L. White,
- RG8E, on Tendon Inspection, March 26, 1980 (5)
Trip Report from A. Hafiz and J.
Chen to J.
Knight on Field Observation of Tendon Surveillance, Nov. 25, 1980 (6)
Letter from J. Maier, RG8E to D. Crutchfield,
- NRR, on Tendon Surveillnce Program, April 29, 1981.
At the Ginna Nuclear Plant in 1977, as a result of required surveillance, the tendons were found to have lost tension in excess of that predicted to be lost over the 40-year lifetime of the plant (Ref. 2).
The tendons and associated rock anchors serve to prestress the concrete in order that only compressive loads are applied to the concrete during any accident which could pressurize containment.
In order to assure resistance to overturning moment during seis-mic events, in 1980 the tendons were retensioned to meet design requirements.
An investigation was made to determine the cause(s) of the detensioning and evaluate the adequacy and capability of the containment building/rock anchor system (Refs.
3 thru 6).
The subject report (Enclosure to Ref. 1)~ describes the results of that investigation.
Based on the review of the licensee's submittals in above references and in particular the enclosure to Reference 1,* the staff has concluded that the licensee has not demonstrated conclusively that the stress relaxation of the tendon wires is the only single cause for the larger-than-predicted force loss in the tendons (as the licensee concludes) because:
(1)
The small scale. rock anchor tests cited by the licensee as the proof of the bond capacity between the grout plug surrounding the rock anchor and the rock indicate that the design bond strength is adequate.
However, '
GAI Report No.
- 2347, February 1982.
Unless otherwise
- noted, comments apply to that document.
(2)
(3)
(4) the test results (FSAR Figures 5.6. 1-6 thru 8) reveal that the slip took place at random loading levels and a slip may take place at a load level somewhat lower than the design bond capacity.
These results also. show
'hat the load-deformation relationship varied in a wide r ange and the ultimate bond capacity becomes lower when the effective grout depth increases.
No discussion about this unusual behavior is provided in the report.
The time effect on the bond capacity has not been investigated.
The small scale anchor. test results indicate the load-deformation relation-ship of the rock anchor bond is nonlinear; therefore, the time effect on bond capacity may be significant.
Four full-size rock anchors tested during installation indicated that bond slip at the grout-rock interface did occur (p. 2-3).
The ratio of measured to predicted elongation of the rock anchors varied from 1.68 to 2.02, indicating that the elongation prediction could be off by as much as 100 percent.
The causes for this, i.e.,
because of in-situ rock con-ditions, grout-rock interface conditions or other reasons, have not been investigated.
The comparison of measured to predicted elongations for "rock anchored ten-dons" and "non-rock anchored tendons" (Table 2.1-1) indicates that the prediction of the elongations for "rock anchored tendons" is much more uncertain than for "non-rock anchored tendons."
(5)
The stress relaxation tests conducted at Lehigh University (Section 3) indicate that two of the three sample wires exhibit greater stress relax-ation properties than what was used in the original design while one sample wire exhibits less relaxation.
This does not totally support the licensee's contention that stress relaxation is the sole cause of pre-stress loss.
(6)
The 1981 tendon surveillance results (Table 5-2) show that the ratio of measured to predicted tension loss of same type tendons (from same heat) varied in'a wide range, from 1.0 to 3.2.
~
The 1981 prediction of the tendon 'force loss should have used the Lehigh test results.
For the above reasons, the staff remains concerned that part of the loss of prestress could be due to the rock anchor system or other factors (see comments below) in addition to stress relaxation of the wire.
Since the rock anchors are not accessible, direct investigation of the rock anchors contribution to the tendon force loss is impracticable, if not impossible.
Therefore, in order to assure the sa'fety function of the tendon
- system, more frequent monitoring'of tendon force is required.
Our additional comments concerning the report forwarded by reference (1) are as follows:
(7)
The proposed future surveillance, Section 7.0, is not adequate in light of the Lehigh test results which indicate that two-thirds of the tendons may lose their design safety margin in about 10,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> due to stress
(8)
(9) relaxation alone.
Therefore, a more frequent inspection, on an annual
- basis, is required for this reason as well as that noted above.
The licensee should provide the NRC staff with a schedule which indicates when the Lehigh tests for tendon wire relaxation will be available
- and, based on that schedule, when the licensee will provide an assessment of relaxation predictions by the factor method.
The schedule should be pro-vided immediately.
That assessment should be inc'luded in the next tendon surveillance report and integrated with the data collected during the next surveillance.
It is expected that a significant portion of the Lehigh test data will be available before the report of the summer 1983 tendon surveillance is required to be forwarded to the staff.
Therefore, there should be sufficient data available in order to construct curves of tendon force vs. time, including tolerance bands of allowable upper and lower bounds for the tendons surveyed as outlined in Reg. Guide'.35. l.
It is expected that the next forthcoming surveillance report will contain such curves so that an extrapolation can finally be made of the tendon forces to be expected in the future.
It is assumed that the next tendon
'surveillance will be conducted on tendons which include at least some of the same group as those surveyed in the 1981 inspection.
In the discussion of the effects of the neoprene pads on the tendon pre-stress loss, it appears that this unique feature of the prestressed con-crete system was rather summarily dismissed as a contributing factor to tendon losses.
Specifically, a visual inspection of the pads should be performed even if some removal of concrete is involved.
The thickness of the pad material should be measured and samples obtained for evaluation of the condition of the elastomeric material.
The assumptions made in the report concerning pad deformation were extrapolated from handbook values and must therefore be considered optimistic especially since the pads are overstressed for such material.
Since each O. 1 inch of inelastic deformation in the pads would reduce the tendon force by about 9 KIPS (at the 742 KIP design load), the contribution of the pads to loss of tendon force cannot be readily dismissed.
Also, since these pads are designed to function as a hinge mechanism in the event of an accident that causes containment pressurization, specific information of their condition should be obtained rather than assuming that they are in serviceable condition.
(1O) The report does not reference the load history which may have been collected by monitoring the four load cells which are installed in the tendon system.
These load cells were used to record tendon force losses collected in original containment leak rate test (GAI Report No.
1720 dated October 3, 1969) and subsequently to continuously monitor tendon forces.
The licensee should provide available data from the load cell readihgs taken since the retensioning of the tendons and since the 1981 surveillance along with a critical assessment of the information.
The licensee should provide predictions about the expected behavior of the retensioned wire for the following potential conditions:
(a) If the tendons should ever need to be retensioned again in order to maintain prestress.
(b)
Expected behavior of the retensioned wire in the event of contain-ment pressurization.
Such predicted behavior should be confirmed,'o the extent possible, during the next integrated leak rate test.*
(12) The long-term effects of variation of temperature on the stress relax-ation properties of the wire and the tendon system have not been sufficiently addressed.
~
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