ML17249A985
| ML17249A985 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point, Saint Lucie  |
| Issue date: | 03/14/1980 |
| From: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Robert E. Uhrig FLORIDA POWER & LIGHT CO. |
| References | |
| NUDOCS 8003250565 | |
| Download: ML17249A985 (10) | |
Text
NB'ORAHDUl4 FOR:
D. L. Ziemann, Chief Operating Reactors 8ranch 82 Division of Operating Reactors FROtj:
V. S. Hoonan, Chief, Engineering Branch Division of Operating Reactors
SUBJECT:
REVIEW OF LETTER REPORT DATED DECEMBER 12; 1979 OH TENDON IHSPECTIOH AND LIFT>>OFF VERIFICATIOH FOR GINHA NUCLEAR PONEA STATION (DOCKET NO, GO@44)-TAC 12461, DATED HOVBIBER 202 1979
Reference:
HRC letter to Rochester Gas and Electric. Corporation requesting for Mditional information on Tendon Surveillance.
Our review of the Rochester Gas and Electric Corporation's repeat revealed that the response did not provide adequate information for us to evaluate the conditions at Ginna.
Me therefore request for additional information specifi-cally addressing to the following:
1, Concrete Shrinka e (p.3)
The shrinkage of concrete is an impor tant factor which contributes to the loss of'reStress.
The magnitude of the shrinkage must be calculated with reasonable accuracy.
The best method of estimating the amount of concrete shrinkage for the use of any structural design is through the use of shrinkage tests.
Only in the case where no test has been performed, then, the suggested shrinkage strain presented in Regulatory Guide 1.3$.1 can be used to establish a tolerance;band.
At Ginna, shrinkage tests in accordance with ASTN C-494 have been per'formed by PittsbuLgh Testing Laboratory in 1967 with the results higher than 100 x M"" in/in, Please explain why th'ts has not been taken into the consQeration.-
P'tease also provide the mix design of the in-placed concrete and discuss the significance of the water'uantity and humidity environment.
,- 2.
Time when shrinka e starts (p.4)
It is usually assumed that no shrinkage would take place during curing if concrete is kept wet.
Obviously, to keep it wet is impossible for large constructions.
Regulatory Guide 1.31.6 suggests to consider the shrinkage starts at 10 days after pouring the conc%Le.
Please provide the basis fo' E ~
di scuss the onstruction ime effect o the ygr~ika~
SURNAME&
DATE~
NRC Form 318 t2-76) NRCM 02040 4 U,S. GOVERNMENT PRINTINO ORRICC: 1078 884 782 003880 6 W
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Some specific creep curves were used in the calculhtion of prestress loss due to creep.
Please provide those curves, the associated concrete mix design used for that prospect, and the test results, Tendon stress relaxation (p. 8)
As presented in the report, the steel relaxation seems to be the moor contributor to the prestress, loss.
Therefore, the'ccuracy of the back-up data for the estimate is crucial.
Section CC-2424 of ACI-359 requires a
-minimum of three 1000-hour re]axation tests for the <eire used.
Please submit those data or appropriate back-up data for Figure 3A.
Hinimum desi n re uirements (p. 9)
Please provide the minimum design requirements of the prestress.
tendons in the original design and the associated weld combination.
Possible causes (p. 16)
Man> possible causes were listed in the report.
However, the most important
- factors, losses due to rock and e'fastomeric pad deformation at the base of'he containment wall, were not thoroughly evaluated.
Based upon 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, 3 year s and 8
- years, unusual prestress losses were observed in man/ tendons.
"Time Limitations" may be used as an excuse for not examining the rock deformation for the results of 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> inspection.
But, for such repeatable occurances, it would be rather unthinkable for not looking into these factors.
Especially, the 10-year inspection program did not have any provision to isolate any of the potential causes needs to be crit$zized.
Lift-off rocedures (p. 17, I-1 5 1-A1)
The lift-offprocedure using 1/32 inch shims is stated to be more accurate" than the accoustic method.,
Please provide the bases and all the supporting information.
Also provide the information about the instr umentation and the results of monitoring the initial 5 final tendon positions and discuss the detensioning effects on shims..
Visual ins ection Please provide the results and photographs documenting all the visual inspections on the surrounding concrete of the tendon anchorages and rock anchors..
OFFICE ~
SURNAME~
DATE M NRC Form 3188 {4-79) NRCM 0240
- U.t~ GOVCRNMCRT tRIHTIRG OI'I ICRI Itrt ttt ttl
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D.. L. Ziemann 9.
Rock anchor desi n (5.1.2<<20)
Please provide the design bases for the rock anchors,%he required=~
'~ rock anchor capacity and the factor of safety in the original ilesign
'She records of the installed depths of the rock anchors, the results of the rock anchor tests, drawings of the rock anchor coupling and the records of'he lengths that the anchor heads threaded into the couplings.
Please also discuss the effects of gmup actions, the maximum jack force, the over-stressing on the rock anchor capacities, and the type of the instrument and the observation data obtained.
In summary, we feel that the responses submitted do not provide adequate bases.for their conclusions and the above information, especially item 9, are needed within 30 days for us to evaluate the conditions at Ginna.
CONTACT:
J. T. Chen 443-5997.
V. S. Noonan, Cl~ief Engineering Branch Division of Operating Reactors CC:
D. Eisenhut, DOR L
- 0. D. Liaw, DOR R.'. Shewmaker, IE J.'Shea, ORPH P.
- SCSB OFFICE M QQP sURNAME,M JTChen BDLi w
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"VSNoona'n OATE IR 2/Z4'/8 80 NRC Form 3188 {4-j9) NRCM 0240
- II,P OOVORNMONT RRINTINO ORRICOI ITIS TIS ITI
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oo UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555
+**++
FEB 21 1980 FROM:
YIEf10RANDUN FOR:
D. L. Ziemann, Chief Operating Reactors Branch 82 Division of Operating Reactors V. S.
Noonan, Chief, Engineering Branch Division of Operating Reactors
SUBJECT:
REVIEW OF LETTER REPORT DATED DECEMBER 12, 1979 ON TENDON INSPECTION AND LIFT-OFF VERIFICATION FOR GINNA NUCLEAR POWER STATION (DOCKET NO. 50444)-TAC 12461, DATED NOVEMBER 20, 1979
Reference:
NRC letter to Rochester Gas and Electric, Corporation requesting for additional information on Tendon Surveillance.
Our review of the Rochester Gas and Electric Corporation's report revealed that the response did not provide adequate information for us to evaluate the conditions at Ginna.
We therefore request for additional information specifi-cally addressing to the following:
1.
Concrete Shrinka e (p.3)
The shrinkage of concrete is an important factor which contributes to the loss of prestress.
The magnitude of the shrinkage must be calculated with reasonable accuracy.
The best method of estimating the amount of concrete shrinkage for the use of any structural design is through the use of shrinkage tests.
Only in the case where no test has been performed, then, the suggested shrinkage strain presented in Regulatory Guide 1.35. 1 can be used to establish a tolerance. band.
At Ginna, shrinkage tests in accordance with ASTYI C-494 have been performed by Pittsburgh Testing Laboratory in 1967 with the results higher than 100 x 10 6 in/in.
Please explain why this has not been taken into the consideration.
Please also provide the mix design of the in-placed concrete and discuss the significance of the water quantity and humidity environment.
2.
Time when shrinka e starts (p.4)
It is usually assumed that no shrinkage would take place during curing if concrete is kept wet.
Obviously, to keep it wet is impossible for large'onstructions.
Regulatory Guide 1.35.1 suggests to consider the shrinkage starts at 10 days after pouring the concrete.
Please provide the basis for assuming that shrinkage starts one hour after concrete placement.
- Also, discuss the construction time effect on the shrinkage.
P D. L. Ziemann 3.
4.
5.
6.
7.
8.
~C (p.6)
Some specific creep curves were used in the calculation of prestress loss due to creep.
Please provide those
- curves, the associated concrete mix design used for that project, and the test results.
Tendon stress relaxation (p. 8)
As presented in the report, the steel relaxation seems to be the major contributor 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.
Please submit those data or appropriate back-up data for Figure 3A; Minimum desi n re uirements (p. 9)
Please provide the minimum design requirements of the prestress tendons in the original design and the associated weld combination.
Possible causes (p.
16)
Many possible causes were listed in"'the report.
- However, the most important
- factors, losses due to rock and elastomeric pad deformation at the base of the containment wall, were not thoroughly evaluated.
Based upon 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, 3 years and 8
- years, unusual prestress losses were observed in many tendons.
"Time Limitations" may be used as an excuse for not examining the rock deformation for the results of 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br /> inspection.
But, for such repeatable occurances, it would be rather unthinkable for not looking into. these factors.
Especially, the 10-year inspection program did not have any provision to isolate any of the potential causes needs to be criticized.
Lift-off rocedures (p.
17, I-1 8 I-Al)
The lift-offprocedure using 1/32 inch.shims is stated to be more "accurate" than the accoustic method.
Please provide the bases and all the supporting information.
Also provide the information about the instrumentation and the results of monitoring the initial 5 final tendon positions and discuss the detensioning effects on shims.
Yisual ins ection Please provide the results and photographs documenting all the visual inspections on the surrounding concrete of the tendon anchorages and rock anchors.
9; L. Ziemann 3
9.
Rock anchor desi n (5. 1.2-20)
Please provide the design bases for the rock anchors, the required rock anchor capacity and the factor of safety in the original design the records of the installed depths of the rock anchors, the results of the rock anchor tests, drawings of the rock anchor coupling and the records of the lengths that the anchor heads threaded into the couplings.
Please also discuss the effects of group actions, the maximum jack force, the over-stressing on the rock anchor capacities, and the type of the instrument and the observation data obtained.
In summary, we feel that the responses submitted do not provide adequate bases for their conclusions and the above information, especially item 9, are needed within 30 days for us to evaluate the conditions at Ginna.
.)
c~. e-S.
Nvonan, Chief Engineering Branch Division of Operating Reactors CONTACT:
J. T.
Chen 443-5997 CC:
D. Eisenhut, DOR L. Shao, DOR R.
H. Vollmer, DOR E. L. Jordan, IE D. N. Crutchfield, SEPB C. Hofmayer, SGPB B. D.,Liaw, DOR R.
E.
Shewmaker, IE J.
- Shea, ORPt4 P.