ML19309G510
| ML19309G510 | |
| Person / Time | |
|---|---|
| Site: | Ginna  |
| Issue date: | 03/26/1980 |
| From: | Ziemann D Office of Nuclear Reactor Regulation |
| To: | White L ROCHESTER GAS & ELECTRIC CORP. |
| References | |
| NUDOCS 8005070067 | |
| Download: ML19309G510 (3) | |
Text
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UNITED STATES 8 0 05 0700 6'T 77 f % v d',g NUCLEAR REGULATORY COMMISSION g
C WASHING TON, D. C. 20555
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ffarch 26, 1980 m,<
~ 3cket !;o. 50-244
- r. Leon D. White, Jr.
Vice President Electric and Steam Production Rochester Gas & Electric Corporation 89 East Avenue Rochester, New York 14649
Dear fir. White:
SUEJECT: TENDON INSPECTION AND LIFT-0FF VERiFICATI0fl FOR GINNA NUCl. EAR POWER STATION.
He tre continuing our review of the report attached to your letter dated Decen-ber 12,1979 relating to tendon inspection and lift-off verification for Ginna and have found that the following information is needed within 30 days of your receipt of this letter.
1.
Concrete Shrinkage (p.3)
The shrinkage of concrete is an important factor which contributes to the loss of ;,restress. The magnitude of the shrinkage must be calculated with reasonable accuracy.
The b?st method of estimating the amount of concrete strinkage for the use of any structural design is through the use of shrink-1;e tests.
Only in the case where no test has been performed, can the sug-gested shrinkage strain presented in Regulatory Guide 1.35.1 be used to establish a tolerance band. At Ginna, shrinkage tests in accordance with ASTMC-494wereperformedg. Pit'burghTestingLaboratoryin1967withre-sults greater than 100 x in/in.
Explain why this has not been taken into the consideration. Also provide the mix design of the in-placed con-crete and discuss the significance of the water quantity and humidity en-vi ronment.
2.
Ti e when shrinkage starts (p.4)
It is usually assumed that no shrinkage would take place during curing if ccncrete is kept wet.
This may be impcssible for large placements. Regu-latory Guide 1.35.1 suggests that shrinkage starts 10 days after pouring the concrete.
Provide the basis for assuming t:1at shrinkage starts one hoar af ter concrete placement. Also, discuss the construction time effect On the shrinkage.
2.
Creen curves (p.6) i 5: e specific creep curves were used in the calculation of prestress loss 4 e,to creep.
Provide these curves, the associated concrete mix design ned for the Ginna contain ent and the test results.
7 4
4 Mr. Leon D. White, Jr. -
March 26,1980 i
4.
Tendon stress relaxation (p.8)
As presented in the report, the steel relaxation seems to be the. major con-i tributor to the prestress loss.
Therefore, the accuracy of the back-up data for the estimate is crucial.
Section CC-2424 of ACI-359 requires a minimum of three 1000-hour relaxation tests for the wire used.
Provide this data or appropriate back-up data for Figure 3A.
j 5.
Minimum design requirements -(p.9) t i
Provide the minimum design requirements of the prestress tendons in the
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original design and the associated weld combination.
6.
Possible causes (p.16)
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Many possible causes were listed to explain the reduction in tendon prestress.
However, the most important factors, losses due to rock and elastomeric pad j
de, formation at the base of the containment wall, were not evaluated.
Based cocn the results of the previous inspections: 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br />, 6 months,1 year, j
3 years and 8 years, unusual prestress losses have been observed in many tendons.
A suitable explanation should be provided since the 10-year in-spection program recently completed did not address any of the potential Causes.
1 i
7.
Lif t-off proceduens (p.17.1-1 & I-A1)
The lift-off procedure us'.ng 1/32 inch shims is stated to be more " accurate" than the accoustic methoa.
Provide the bases and all the supporting infor-4 ration including information about the instrumentation and the results of canitoring the initial aad final tendon positions and discussion of the
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cetensioning effects on shims, a
j 8.
Visual inspection l
Provide the results and photographs documenting all the visual inspections on the surrounding concrete of the tendon anchorages and rock anchors.
4 9.
Rock anchor design (5.1.2-20) f Provide the design bases for the rock anchors, the required rock anchor.
I capacity and the factor of safety in the original design, the records of the i
installed depths of'the rock anchors, the results of anchor tests, drawings of the rock anchor coupling and the records of the lengths 'that the anchor heads thread into the couplings. - Also discuss 'the effects of group actions,-
the maximum jack' force, the over-stressing on the rock anchor capacity, and the type of the instrument and the observed data.
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Mr. Leon D. White, Jr. March 26, 1980 Please contact us if any clarification of this request is required.
Sincerel V.,
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DennisL.Ziemann,(Ghief
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Operating Reactors Branch #2-Division of Operating Reactors t
cc: See next page i
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. March 26, 1980 Mr. Lecn D. White, Jr.
cc Harry H. Voigt Esquire Director, Technical Assessment LeBeevf, Lamb, Leiby & MacRae Division 1757 1. Street, N. W.
Office of Radiation Programs Washington, D. C.
20036 (AW-459)
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Region II Office P. O. Box 5236 River Campus ATTN: EIS COORDINATOR Station.
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