ML18059A668
| ML18059A668 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 02/07/1994 |
| From: | Slade G CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| TAC-M84017, NUDOCS 9402170226 | |
| Download: ML18059A668 (12) | |
Text
consumers Power
~-1111" l'OWERIN&
MICHl&AN"S l'RO&RESS Palisades Nuclear Plant:
27780 Blue Star Memorial Highway, Covert, Ml 49043 February 7, 1994 Nuclear Regulatory Commission Document Control Desk Washington, DC 20555 GB Slade General Manager DOCKET 50-255 - LICENSE DPR PALISADES PLANT - RESPONSE TO NRC REVIEW OF PALISADES CONTAINMENT 20TH YEAR TENDON SURVEILLANCE REPORT - REQUEST FOR ADDITIONAL INFORMATION (TAC NO. M84017)
By letter dated June 16, 1992, Consumers Power Company subm{tted the 20-year containment tendcn surveillance report for the Palisades plant.
By letter dated September 14, 1992, the NRC requested that Consumers Power Company provide additional information to facilitate completion of the NRC review of the report.
Our response to your request for additional information is attached.
Ge~~~~
General Manager CC Administrator, Region Ill, USNRC NRC Resident Inspector - Palisades Attachment 1.50013 9402170226 ~~858~55
, PDR*
- ADOCK
- PDR p
A CMS' E.NER~ COMPANY NUCLEAR PLANT
ATTACHMENT Consumers Power Company Palisades Plant Docket 50-255 RESPONSE TO NRC REVIEW OF PALISADES CONTAINMENT 20TH YEAR TENDON SURVEILLANCE REPORT February 7, 1994 Pages
RESPONSE TO NRC REVIEW OF PALISADES CONTAINMENT 20TH YEAR TENDON SURVEILLANCE REPORT NRC Comment No. 1 In the 1 ast paragraph of section 2 Item II, Sheathing Fi 77er, you stated that grease leaks observed at 30 anchor locations beyond the selected surveillance tendons were repaired and the results are summarized in Table XIA.
We note from the table that the tendon grease cans which needed repair are those of the vertical tendons which were detensioned on one side of the SG transfer opening.
There are similar detensioned tendons on the other side of the steam generator (SG) transfer opening which did not have the same problem.
Explain why there is such a difference.
Besides the grease leakage at the anchor locations, indicate if there are signs of grease leakage at locations away from the anchor.
Discuss the potential detrimental effect of grease leakage into concrete.
CPCo Response:
The repair performed on the additional 30 vertical tendon grease can gaskets for grease leakage as shown in Table XIA were generally the result of an ambient temperature change after hot greasing operations.
In addition, 13 vertical tendon grease can gaskets were repaired following the. steam generator replacement for the same reason.
The tendons repaired were:
V54, V58, V60, V64, V66, V74, V78, V80, V84, V86, V94 and V98.
These tendons are located on the opposite side 0f the construction opening from the tendons listed in Table XIA.
The location of the leakage occurrence did not appear to be related to the construction opening location. Visual inspections on the concrete and liftoff readings.performed during the surveillance have supported the conclusion that grease leakage has no impact on concrete intagrity.
Grease leakage was also found along scattered concrete construction joints.
This is not a unique situation to Palisades, but a generic problem occurring in many other plants.
Palisades evaluated the leakage and determined that no structural problem exists at these locations.
To date, no study exists nor has testing been performed to determine the potential long term impact of grease leakage o~ the integrity of concrete.
The ASME Section XI Working Group IWL on Concrete Pressure Component has been evaluating this situation for a possible solution to address this generic concern.
Also, Palisades performed visual examinations on the 52 tendons that were removed during the Steam Generator replacement project.. The exams indicated that adequate grease coverage existed on the tendons and identified no corrosion.
In addition, during previous surveillances, all tendons examined had adequate grease coverage.
Based on previous examination history, we are confident that the tendons at Palisades are fully protected by tendon grease.
I
NRC Comment No. Z Accardi ng to t '1e information provided to the staff at thi: time of SG replacement, there were fifteen (15) vertical tendons anc.' thirty-seven (37) hoop tendons pHsing through the transfer opening which w.:?re detensioned and removed".
Such an opportunity is rare and more detail.ed and useful information than that from the periodic surveillance can be obtained and used for evaluating the tendon integrity and assessing the adequacy of the current tendon survei77ance program.
Provide, if you can, any information on your experience on these tendons.
CPCo Response Consumers Power CJmpany did take advantage of the opportunity to include two tendons (i.e., one hoop tendon and one vertical tendon) that were detensioned and removed in the 20th year surveillance. These tendons were Vl28 and 48AE.
Of the 130 tendon~ detensioned (52 of the 130 tendons were removed) during the steam generator Teplacement, twelve had liftoff measurements performed prior to detensioning.
The attached drawing, number C-3006, Rev. a, indicates the relative locatio~*of these tendons in respect to the Steam Generator construction opening.
The two tendons selected for inclusion into the 20th year surveillance.were not among those twelve that were test~d. Therefore, no liftoff measuremer\\-i:s were performed on Vl28 and 48AE prior tp the'ir detensioning and removal.
Visual inspections were performed! on both tendons during the removal process with no abnormal indications identified.
The following information shows the liftoffs values after r£installation and the liftoff values during the 20th year surveillance.
The results of the liftoff testing v.iere found to meet the acceptable values.
48AE V-128 Liftoff ~fter Reinstallation Shop End Field End Shop End 757 Kips 753 Kips 741 Kips NRC Comment No. 3 Liftoff During 20th Year Surveillanc~
Shop End Field End Shop End 593 Ki.ps
- 711 Kips 680 Kips The tendon survei77ance performed recently is the sixth {'20th year). *On the basis of the data collected from the six surveillances and from the SG replacement operation, a trend in the prestressing forces'* for each group of tendons can be established and any abnormality in the long* term behavior of each group of tendons can be detected.
Provide.this information.
2
.. e I,
CPCo Response Listed below are the average liftoff measurements for each group of tendons during each surveillance and during the SG replacement.
All liftoff forces shown meet acceptance criteria. Attached are graphs of the tendon*liftoff forces for the life of the plant. These graphs are consistent with the graphs provided in the tenth and fifteenth year tendon surveillance reports.
Palisades has concluded that no abnormalities in the long term behavior of the tendons is occurring.
Vertical Hoop Dome Tendons Tendons Tendons First Year Surveillance 672 Kips 678 Kips 682 Kips Third Year Surveillance 703 Kips 673 Kips 694 Kips Fifth Year Surveillance 674 Kips 663 Kips 659 Kips Tenth Year Surveillance 663 Kips 659 Kips 640 Kips Fifteen Year Surveillance 674 Kips 649 Kips 650 Kips SG Replacement 651 Kips 634 Kips N/A Twentieth Year Surveillance 645 Kips 655 Kips 648 Kips NOTE: The average for the Twentieth Year Tendon Surveillance does not include tendons V72, Vl28, 29AE, 48AE and 52AE.
These tendons were detensioned as part of the Steam Generator replacement project and are shown on their own graph (attached).
NRC Comment No. 4a Data sheets 11.V in PSC Procedure SQ.11 tabulate the observed forces and elongation mea*;urements for tendons 02-23, V218 and 29AE.; Since the tendon behavior at tensioning is elastic, the force required for unit elongation for each tendon should be basically linear.
We realize that the preliminary tensioning force (PTF) is used in part to straighten the* slack rather to stretch the tendon.
On the basis of this understanding, the staff made an analysis of the information from the data sheets and the results of the analysis are shown in Table 1.
Of the three tendons detensioned and retensioned, the results for hoop tendon '29AE are most inconsistent.
On the basis of the above observation, your responses to the following questions are requested:
4a. Provide reasons for the inconsistency in the results for hoop tendon 29AE as indicated in Table 1.
Your corrective action as contained in NC/CA 417-002 does not answer this staff's concern.
CPCo Response 4a.
While th~ preliminary tension force is used to straighten the tendon and take :.1p the slack, this force is often not high enough to break any binding or friction point within the tendon void.
This often requires ~ar higher forces, which, upon breaking the friction point, 3
will a 11 ow the force to act over a greater length, c: ;1d that increment will show a significant increase in elongation.
Similarly, the final increment in tendon 29AE is releasing pressure, and, ther!.fore, any binding within the tendon as the: wires try to go back into the void, will show a reduction in the elongation as the reduction in pressure acts over a shorter tendon length than during stressing due to reverse effect of friction.
The lift-off difference of 29AE is considered as fol~ows: Figure I shows the tendon location and layout.
If the tendon,was stressed normally, the force distribution curve would look like Figure 2, which is the curve plot from the steam generator replacement data of 29AE.
The elongation calculation from this curve provides.an elongation of 4.7 inches shop of the shop end and 4.7 inches of the field ends.
However, if we were to consider the possibility of a tendon binding at 10 to 15 feet from buttress E shop end, (during tendon replacement, this area was reported difficult for rabbit movement on tendons above 29AE), it would change the force distribution curve to Figure 3.
The estimated 1elongation for this curve is 4.5 inches for the shop end and 4.7 inches for the field end.
The approximate 11As Left" data is. 4.25 inches for the shop end and 4.3 inches for the field end.
In addition, we have plotted the theoretical forces value for Points A, B, and C.
Over ti me, the tendon wi 11 try to reach equilibrium over its length.
Friction slows this process and binding distorts even more.
BtDding prevents the tendon from being equallJ distributed.
Therefore ;
1 from shop end to point A, the average for,ce is going to be higher t~an lockoff due to the short length and highiforce level of point A. 1This assumes binding does break free.
(Ref. red color curve for avg. force.)
In turn, the -Opposite effect occurs to the field end.
The force drops quickly trying to raise point B~ Therefore, without considering losses, the predictable force for the shop end is 756.5 Kips and 673 Kips for the field end.
The actual "As Found" force, after losses, was 685 Kips for the shop end.
This is a theoretical loss of 71.5 Kips for th~ shop end from the average force.
We estimate that 60% of the loss would have occurred* on the field end due to the length involved.
Projecting total losses from this gives 178.75 Kips total and 107.25 Kips for the field end.
The average force for the field end of 673.00 Kips would drop to 565.75 Kips, which is ~bout equal to the "As Found" average force value of 564 Kips.
Therefore, this possible binding fits the conditions" found.
Figure 4 shows the curve after losses (blue) and the estimated average curve that would have been closer to (the red curve) actual at this time.
Note that the tendon would not have been able to re~ch equilibrium in 4
one year.*, Since the tendon was re-stressed and its average was greater than the minimum design, no further action w~s deemed necessary.
We consider this an isolated case.
l NRC Comment No. 4b 4b. In DS 11.0 item (9.9.6.2) elongation variation for tendons 02-23, V218 and 29AE are given as -3.1%, -10.3%, and -1.7% respectively.
Indicate the significance of these variations, in view of the fact that friction plays an important role and cannot be accurately evaluated, especially for the curved tendons.
CPCo Response 4b.
Ref. NCR 417-004 addresses the correction of the wrong parameters in the original calculation of the elongation of V218.
The correction results in the elongation being -1.3%, not -10.3% as previously reported.* There is thus no significant variation between tendons 02-23, V218 and 29AE which are given as -3.1%,
-1.3~ and -1.7%
respectively.
NRC Comment No. 4c 4c. Without taking friction into consideration, provide the force required per unit elongation for each of three tendons.
Indic~te the length of each tendcn.
CPCo Response 4c.
An indication of wire elongafion per unit of force can be seen from the wire test results which act similar to a friction~ess tendon.
These results are given on data sheets SQ 10.3. for the three wire samples.
We believe it is inappropriate to remove friction from consideration for comparison as it will greatly effect the force requir~d per unit elongation.
It will vary, not only per unit of elongation, but also from tendon to tendon as it bre~ks free at indeterminate friction points.
Listed below are the approximate tendon lengths for the tendons in question.
Vertical Tendon V218 - 190.47 feet Hoop Tendon 29AE - 135.51 feet Dome Tendon 02 135.64 feet 5
NRC Comment No. 5
- 5.
Indicate how the lift-off force for each tendon surveillanced is determined, noting that only the force at the instant when the tendon is lifted from the seating is to be counted as the lift-off force.
The procedure d*scribed in item 9.7 in PSC Procedure SQ 9.0 appears to be inadequate.
CPCo Response The forces indicaied in item 9.7 of PSC Procedure SQ 9.0 ar~ to provide a range of operation within which the lift-off value will be found.
This is to maintain forces below 80% of the ultimate strength of the tendon to ensure safety.
Actual lift-off force is measured according to section details procedures for using the feeler gauge method.
follows that described in the "Evaluation of lnservice Prestressed Tendons," NRC Fin. No. A9044.
This report 9.8 of SQ 9.0 which This 'procedure closely Inspections of Greased concludes:
"The use of a feeler gauge placed between the shims and the bearing plate.
is a reasonably accurate method that leads to highly reproducible results. '
Once the tendon stress has been completely removed from the shims and transferred totally to the stressing equipment, the change in stress corresponding to a small elongation (e.g., the thickness of a feeler gauge) is very small and may be considered negligible.
This is because the tendon length is quite large compared with the elongation."
The~efore, we conclude that the procedures used are adequate for determining liftoff forces.
.1.,
6
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It is lent to the recipient for his ccnfidsntml ue;e ai1u. 11nd LPJn the ccn:::littms 11nd ~<;Temenh; fo 11.ow!rg.
Jn ccnsidel'!ltiai of tlJe 'lo!ln of this d~wl.rg. the r-ec:lpient i:ranlsei; 11nd !llT986 to peh..rn it LCXJl r-eQJBSt. !Ind th11t it sh!l 11 not be r-ei:rod..ced. ooi:daj, lent a' otherwise dlspoeed or dlr-ectlu er irdl.r-ectlu wl.ttwt PSC's written cooe;ent. ncr be used 1n 11nu W!IU cletMment!ll to the 1nter-E16ts of PSC.
FIGURE 1 PSC E
PRECISION SU RV EIL LAN CE CORPORATION DAAWING NO. p AL ISA DE
1048 811 717.7 530 SHOP ENO BUTTRESS E Th15 dl"l!lwirg ha6 not been ~li!Shed it is the sole prwertu of Frec::lsl.on SU"\\lelllarce Cc:rDCJ'aticll (F9;), It ls lent to the rec:lpient for his ccnfidenti!ll lJ08 on lu. md l.P)n the caditl.clls md QJl;TElments fo 11.owirg, 1n ccnsideration of the loan of this dl"l!lwirg. the recipient i:rc:m!s815 ard ll'1'886 to rehrn it LPJn reQ.JBSI". ard that it sl'llll not be rei:roci.ced. ooi:;:ded. lent c:r otherwise dll;poeed of dl.rectlu er indl.rectlu wittout rSC\\i written consent. nc:r be used in '!lnU wQJ detMmental to the intere5ts of rsc.
FIGURE 2 PSC PRECISION SU RV Ell LAN CE CORPORATION 1048 811 721.8 530 FIELD ENO BUTTRESS A N:VISED D.&.TE1
,1..rffiCNED Dl..TE1 D~WING NO. PAL2
1048 BIND POINT (A) 811 796
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Tills dr!lwl.rg hae; not been p.bli5hed 1 t is the sole prcpertu of Precision SLrVe111llrce Ccrpcratial !PSCl.
It is lent to the rec:lpisnt for his cxnfidsnttill use ool,u. md LP-Jn the coodittoos md aQgeme~
fo 11.ow!rg, Jn cxnsideratioo of the lam of tills dr!!wl.rg. the reclp;lent prcmisee; ard ag-ees to reh.rn it LP-Jn rec:iJBSt. ard that it sh!!U not be reprod.r;)ed. copied. lent er otherwise disposed of dlrectlu er irdlrectlu wl.ttout PSC's written coosent. ncr be used 1n anu W!IU detMment!ll to the interests of PSC.
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72 1.8 530 FIELD END FIGURE 3 BUTTRESS A ORA~ B'l1 DATE1 l\\EYISED DATE1 PRECISION PSC SU RV Ell LAN CE APl'R<NED DATE1 CORPORATION DRAWING NO. PAL3
1048 811 717.7 685 530 SHOP END BUTTRESS E Tills drawirg his not been i:xbllwd. it is the i;ole prcpertu of Prec::lslon Su-veillarce Ca-!Xl'atioo <PSC), It ls lent to the rec:lplent for his ccnfidsntml l.198 oolu. and l.PQn the cooditioos and "J<;rements foll.a>"1irg.
In ccnsider!ltioo or the lo:!n of this drawirg. the recipient i:r-anlses ard ar;.reee; to rehrn it L.POO reQJBSt. ard that it shall not be rei::rod£ed. copied. lent er otherwise disposed or dlrectlu er irdlrectlu witta.Jt PSC'S written coosent. ncr be used in anu W!l,J d6tr:lment'lll to the interests or PSC.
FIGURE 4 PSC PRECISION SURVEILLANCE CORPORATION 1048 811 721.8 564 530 FIELD END BUTTRESS A REVISEQ DATE1 DAAWING NO. p AL 4