ML18046B357
| ML18046B357 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 03/12/1982 |
| From: | Vincent R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TASK-03-07.A, TASK-3-7.A, TASK-RR NUDOCS 8203160234 | |
| Download: ML18046B357 (3) | |
Text
consumers Power company General Offices: 1945 West Parnall Road, Jackson, Ml 49201 * (517) 788-0550 March 12, 1982 Dennis M Crutchfield, Chief Operation Reactor Branch No 5 Nuclear Reactor Regulation US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT - SEP TOPIC III-[.A, INSERVICE INSPECTION, INCLUDING PRESTRESSED CONCRETE CONTAINMENTS WITH EITHER GROUTED OR UNGROUTED TENDONS By letter dated February 16, 1982, Consumers Power Company submitted proposals for various actions to resolve issues identified by the SEP reviews of the Palisades Plant.
With respect to Topic III-[.A, this letter stated that action which may be appropriate for this topic was stil.l being evaluated.
This evaluation has now been completed.
The purpose of this letter is to submit the Consumers Power Company proposal for actio~ under this topic.
The SEP review of Topic III-[.A identified two basic issues which have not yet been resolved.
First, the staff felt that the acceptance criteria used to evaluate containment tendon surveillance test results should vary with time to reflect the fact that overall prestress decreases in a reasonably predictable manner with time.
This can be accomplished by imposing limits on the existing predicted prestress loss curves.
Second, to account for variations in initial tensioning of individual tendons, it was felt that some means should be used to correlate individual tendon surveillance test results with the expected prestress value for that tendon.
One way that this can be accomplished is by normalizing individual tendon test results to correlate each tendon with the "average" tendon.
The Palisades Technical Specification currently define a single acceptance criterion for each tendon type which is based on the minimum average prestress required at any time over plant life.
After additional evaluation, Consumers Power Company has concluded that changes to the Technical Specification acceptance criteria would be appropriate to incorporate the two considerations discussed above.
These changes will, therefore, be developed and submitted to the NRC for approval.
In general, the proposed Technical Specification changes will be consistent with Standard Technical Specifications (STS) 4.6.1.[.l.a for Combustion Engineering plants. It is our intent, however, to develop a specification which reflects more current thinking than either the STS or Reg. Guide 1.35 Rev. 2.
The content of the proposed change will be patterned after the
-~- --
.- ~8203160234 820312 PDR. ADOCK 05000255 G
DMCrutchfield Palisades Plant SEP Topic III-7.A March 12, 1982 2
pertinent portion of the January, 1981 draft of the ASME B&PV Code Section entitled "Inservice Inspection of Concrete Containments".
It is our under'.""
standing that this draft is essentially final in, at least, technical content, and that the NRC has participated fully in its development.
The appropriate portions of the draft code on which our proposed change will be based are withdrawn from Article lWX-3210, Tendon Force Acceptance Criteria, and quoted --
below:
"The containment shall be considered to have satisfied the prestressing system examiniation if the following tendon force (average of forces measured at both ends, if applicable) requirements are met:
- a.
The average of all measured tendon forces for each type of tendon is equal to or greater than the minimum required prestress level for that type.
- b.
The force measured in any individual tendon is equal to or greater than 95% of its predicted prestress force at the.time of the test.
- c.
The tendon force measurement of any individual tendon divided by the total area of the effective prestressing elements, as defined in the Construction/Specifications, which comprise the tendon shall not ex-ceed 70% of the minimum specified ultimate strength of the prestressing elements."
"In calculating the average force in part (a), each measured tendon force shall be corrected for initial installation conditions (actual anchorage force and elastic shortening loss during initial post-tensioning, and any other significant effects) so that the measured force is indicative of the average level of prestres s."
"Regarding the criterion of part (c), should the number of ineffective prestressing elements be such as to cause the measured tendon force to not meet this criterion, the tendon force shall be reduced or the in-effective prestressing elements replaced to the extent necessary to meet the criterion.
However, the other acceptance criteria specified by this subsubarticle shall be met."
"If the criterion of part (a) is not met, an investigation of the tendon system and structural integrity of the containment shall be conducted.
The investigation shall include consideration of the design margins available in the containment design."
"If the measured force in an individual tendon does not meet the criteria of part (b), but is equal to or greater than 90% of its predicted force, the force in adjacent tendons on each side of the individual tendon shall be measured.
If the forces in these two tendons are equal to or greater than 95% of their respective predicted forces, the inspection program shall proceed considering the event unique and acceptable.
The measured
DMCrut c hfi eld Palisades SEP Topic III-7.A March 12, 1982 3
forces in adjacent tendons shall be included in the calculation of the average tendon force of part (a) of this section."
"If the measured force in either of the adjacent tendons or in more than one of the original sample tendons is less than 95% of its predicated force, J
but is not less than 90% of its predicted force, the deficient adjacent tendons (s) and the inspection tendon shall be evaluated.
If the reason for the deficiency cannot be determined, these tendons shall have their forces measured as additional tendons in the next scheduled inspection period in order to determine if the rate of force loss is significantly greater than predicted."
"If the measured force in any tendon is less than 90% of its predicted force, the tendon shall be completely detensioned and a determination shall be made as to the cause of such an accurance and corrective action shall be taken.
In addition, all such tendons shall have their forces measured as additional tendons in the next scheduled inspection period."
In addition to the above, two other considerations which will affect future tendon surveillance tests should be noted.
First, current Consumers Power Company practice is to retension a test tendon to its liftoff value -0 + 5%
rather than to the STS criterion of + 3%.
As a matter of philosophy, we do not believe that routine testing sho°U:"ld result in allowable degradation from as-found conditions.
We therefore intend to retain the -0 + 5% criterion.
Second, if liftoff of a test tendon were found to occur below 95% of its predicted liftoff value (code criterion b above), we would expect to retension that tendon to the predicted value -0 + 5% for "average" tendon of that type and not some lower value, while remaining consistent with code criterion c.
As you will note, the above discussion tends toward an overall program description rather than a brief technical specification.
The description is provided to ensure that conceptual agreement between the staff and Consumers Power Company is reached now, prior to the time the proposed Technical Specification change is submitted.
In practical terms, this Technical Specification change will have no effect on the plant until 1985 or 1986 when the next tendon surveillance tests will be scheduled.
In addition, Revision 3 of Regulatory Guide 1. 35 is expected to be is.sued within the next several months.
It would be to the mutual advantage of Consumers Power Company and the NRC to wait for th~s guide to be finalized prior to changing the Technical Specification since it may impact both the Consumers Power Company proposal and the NRC review. *Accordingly, it is expected that the proposed Technical Specification change would be submitted late in 1982 but prior to December 31, 1982.
Robert A Vincent Staff Licensing Engineer CC Administrator, Region III, USNRC NRC Resident Inspector - Palisades