ML20033A515
| ML20033A515 | |
| Person / Time | |
|---|---|
| Site: | Bellefonte  |
| Issue date: | 11/17/1981 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8111250523 | |
| Download: ML20033A515 (2) | |
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t TENNESSEE VALLEY AUTHORJg CHATTANOOGA. TENNESSEE 37406 TL A t h-t 400 Chestnut Street Tower II i
November 17, M8NOV 20_ A 9 4 7 l
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Dear Mr. O'Reilly:
BELLEFONTE NUCLEAR PLANT UNIT 1 - LOCK 0FF PRESSURE ON POSTTENSIONING SYSTEM - BLRD-50-438/81 THIRD INTERIM REPORT The subject deficiency was initially reported to NRC-0IE Inspector R.-V. Crlenjak on July 17, 1981 in accordance with 10 CFR 50.55(e) as NCR BLN CEB 8104. This was followed by our interim reports dated August 17 and September 18, 1981. Enclosed is our third interim report.
We expect to submit our next report by January 13. 1982. We consider 10 CFR Part 21 applicable to this deficiency.
If you have any questions concerning this matter, please get in touch with R. H. Shell at FTS 858-2688.
Very truly yours, TENNESSEE VALLEY AUTHORITY s
L. M. Mills, Manag e Nuclear Regulation and Safety Enclosure cc:
Mr. Victor Stello, Jr., Director (Enclosure)
Office of Inspection and Enforcement
- U.S. Nuclear Regulatory Commission Washington, DC 20555 OFFICUL C 81112$0523 811117 C
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ENCLOSURE BELLEFONTE NUCLEAR PLANT UNIT 1 LOCK 0FF PRESSURE ON POSTTENSIONING SYSTEM BLRD-50-438/81-49 10 CFR 50.55(e)
THIRD INTERIM REPORT,
Description of Deficiency Inryco, Incorporated, has been contracted (contract 75C53-85380) to supply and install the posttensioning system for the primary containment struc-tures. Allowable lockoff stresses for each tendon have been established by Inryco in accordance with the April 1973 Trial Use Version of the ACI 359 code and the contract specifications. These lockoff stresses are required to provide assurance that the containment structure will have edequate prestress force to perform its intended safety function.
In order to resolve a problem with certain stressing gauges being out of calibration, Inryco performed liftoff tests on several horizontal tendons.
These liftoff tests revealed that, in several cases, lockoff stresses were substantially lower than predicted.
Interim Progress In the first interim report on this deficiency, Inryco's program for investigation was outlined. The second interim report detailed the results of the friction tests.
After the friction tests, four tendons were subjected to a load equaliza-tion test. Three of the tendons were checked for long-term load equali-zation and the other one for short-term load equalization. Following is a brief description of these tests and a summary of the findings to date.
The short-term load equalization test consisted of single end stressing of a horizontal tendon and then monitoring the stress level at either end of the tendon every 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> for 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. The long-term load equalization test was identical except the stress levels were monitored every 2 or 3 days for 10 to 15 days after single end stressing.
The results of these tests were that neither end of any of the tested tendons showed any variation in stress beyond what is normally expected.
Therefore, it is concluded that even if load equalization occurs, it does not occur within a short enough timeframe to explain the low liftoff readings that have been encountered. The theory of load equalization has been removed from consideration as a possible explanation of the low liftoff stress readings.
In the last report on the subject deficiency, it was stated that there was no indication that stressing equipment was the cause of the deficiency.
.._ ___ _ Stressing equipment still has not been identified as the cause of this deficiency in that this deficiency concerns only horizontal tendons.
However, since the last report was submitted, TVA has been notified of a problem with the stressing jack 9366. This jack was used to stress only vertical and dome tendons. TVA has reported this separate deficiency in nonconformance report 1586.