ML18047A513
| ML18047A513 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 08/12/1982 |
| From: | Vincent R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0820, RTR-NUREG-820, TASK-03-07.A, TASK-3-7.A, TASK-RR NUDOCS 8208160258 | |
| Download: ML18047A513 (7) | |
Text
consumers Power company General Offices: 1945 West Parnell Road, Jackson, Ml 49201 * (517) 788-0550 August 12, 1982 Dennis M Crutchfield, Chief Operating Reactor Branch No 5 Nuclear Reactor Regulation US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-255 -
LICENSE DPR PALISADES PLANT - SEP TOPIC III-7.A~ INSERVICE INSPECTION INCLUDING PRESTRESSED CONCRETE CONTAINMENTS WITH EITHER GROUTED OR UNGROUTED TENDONS In the Integrated Plant Safety Assessment for the Palisades Plant, NUREG-0820, one of the items identified as point of disagreement between the staff and Consumers Power Company concerns the inspection of containment tendon end anchorages.
Although we believe that conceptual agreement has existed on this item, we have been concerned that the final wording in the SER was not explicit enough to avoid future misinterpretation.
Additional discussions have now been held with the staff and we believe that a mutually acceptable resolution for this item has been obtained.
The purpose of this letter is to document that resolution as a formal proposal from Consumers Power Company.
As we have discussed previously, the concrete surrounding tendon anchorages is examined in conjunction with the normal tendon inspections performed under Technical Specification 4.5.4.
The results of the most recent concrete inspections were reported to the NRC as part of the tendon surveillance test report submitted by Consumers Power letter of 11/17/81.
These inspections of tendon anchorages will continue to be performed in the future.
In conjunction with the anchorage concrete inspections, Consumers Power Company agrees to formally incorporate the following additional provisions into the surveillance program for containment tendon testing:
- 1.
Cracks observed in the immediate vicinity of the tendon anchorages being inspected (pursuant to T.S. 4.5.4) which exceed a maximum width of 0. 010" will be mapped and evaluated.
The value of
- 0. 010" is consistent with the draft section of the ASME B&PV Code,Section XI, entitled "Inservice Inspection of Concrete Containments" (dated January, 1982).
8208160258 820812 PDR ADOCK 05000255 G
DMCrutchfield, Chief Palisades Plant SEP Topic III-7.A August 12, 1982 2
- 2.
Each required evaluation will consider, as applicable, crack location, crack size, crack depth if known, location and arrangement of rebar in the vicinity, comparison with previous maps of the same crack if available, concrete temperature as well as experience with the behavior of other typical concrete structures.
- 3.
If an evaluation concludes that an observed crack may be severe enough to potentially degrade containment integrity, that crack will be inspected again with the containment under pressure during the next ILRT.
Final resolution of the condition then would be based on the crack's behavior during pressurization as well as the other factors discussed above.
In support of the above program for end anchorage inspections, it is relevent to discuss two related items.
First, the staff has calculated that the increase in a "typical" tendon force (ie, load on its concrete anchorage) would be approximately 9 kips due to the containment being pressurized to half design pressure during an ILRT.
This value represents only an approximate 1-1/2%
increase in tendon force on the anchorage.
This small increase would not be expected to cause any significant change in crack size or configuration when compared to the unpressurized condition.
Second, it is pertinent to look at the attached plots of strain v containment pressure and compare them with the containment exterior surface temperature variations.
These plots have been extracted from the original containment Structural Integrity Test report for the Palisades containment.
It is interesting to note that the variation in measured strain values due to daily temperature variations of up to 10°C were of the same magnitude or larger than strains resulting from pressurizing containment to approximately 112% of design pressure.
When one considers strain variations resulting from annual changes in concrete temperatures (perhaps 6o0 c) and the. very small strains which result during an ILRT at half design pressure, the value of end anchorage c'oncrete inspections at pressure must be questioned.
The condition which might cause crack growth in concrete tendon end anchorages would appear to be much more frequent and severe due to the natural environment than due to ILRTs.
In summary, both of the above discussions would suggest that tendon end anchorage concrete inspections at any time, regardless of containment internal pressure, would be equivalent for detecting crack growth.
There would appear to be,iittle if any value to performing those inspections with the containment at pressure.
For Palisades, the expense and difficulty associated with routinely combining end anchorage inspections with an ILRT would not be warranted.
As discussed, the above end anchorage inspection program defines the inspection requirements, a threshold crack size at which some action would be taken and evaluations which would be required to justify anomalous conditions which may be identified.
This program is considered to be complete and adequate to monitor end anchorage conditions.
DMCrutchfield, Chief Palisades Plant SEP Topic III-7.A August 12, 1982 As a final comment, it must also be pointed out that current Palisades Technical Specifications require Consumers Power Company to submit the final report on containment tendon ISI activities to the NRC.
In addition, it has been standard NRC practice to assign a special inspector from the Region to ~onitor these activities, including the witnessing of selected tests and the review of the test results.
Regardless of the provisions in Technical Specifications or any other document the fact remains that all containment surveillance activities*are subject to NRC review.
Robert A Vincent Staff Licensing Engineer CC Administrator, Region III, USNRC NRC Resident Inspector - Palisades Attachment
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