ML18046B275

Forwards Response to Comments Re SEP Topic III-7.A, Inservice Insp Including Prestressed Concrete Containments W/Either Grouted or Ungrouted Tendons. Review of Topic Completed

ML18046B275
Person / Time
Site:	Palisades
Issue date:	02/10/1982
From:	Crutchfield D Office of Nuclear Reactor Regulation
To:	Hoffman D CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
References
TASK-03-07.A, TASK-3-7.A, TASK-RR LSO5-81-02-055, LSO5-81-2-55, NUDOCS 8202170482
Download: ML18046B275 (50)

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Docket No. 50-255 LS05-8l 055 Mr. David P. Hoffman Nuclear Licensing Administrator Consumers Power Company 1945 W Parnall Road Jackson, Michigan 49201

Dear Mr. Hoffman:

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February 10, 1982

SUBJECT:

SEP TOPIC III-7.A,. INSERVICE INSPECTION INCLUDING PRESTRESSED CONCRETE CONTAINMENTS vJITM EITHER GROUTED OR UNGROUTED TENDONS -

PALISADES We have reviewed your comments to our SER dated August 25, 1981, on the above topic.

Enclosure l is our response to your co1111n:mts which were provided on November 13~ 1981~ and included here as Enclosure 3.

We have incorporated a number of your cow.ments into a revised SER given as Enclosure 2.

Our review of the topic is complete and the revised SER will be a basic input to the Int~grated Assessment of your facility. This assessment may be revised i.1 NRC criteria relating to this topic is modified before the integrated assessment is completed.

Sincerely,

Enclosure:

As stated cc w/enclosure:

See next page NRG FORM 318 (10-80) NRCM 0240 OFFICIAL RECORD COPY

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I' Docket No. 50-255 LS05-81-02-055 Mr. David P. Hoffman UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 February 10, 1982 Nuclear Licensing Administrator Consumers Power Company 1945 W Parnall Road Jackson, Michigan 49201 *

SUBJECT:

SEP TOPIC III-7.A, lNSERVICE INSPECTION INCLUDING PRESTRESSED CONCRETE CONTAINMENTS WITH EITHER GROUTED OR UNGROUTED TENDONS -

PALISADES We have reviewed your comments to our SER dated August 25, 1981, on the above topic.

Enclosure l is our response to your conunents which were provided on November 13, 1981, and included here as Enclosure 3.

We have incorporated a number of your comments into a revised SER given as Enclosure 2.*

Our review of the topic is complete and the revised SER will be a basic input to the Integrated Assessment of your facility. This assessment may be revised if NRG criteria relating to this topic is modified before the integrated assessment is completed.

Enclosure:

As stated cc w/enclosure:

See next page Sincerely,

~?!~h~

Operating Reactors Branch No. 5 Division of Licensing

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Mr. David J. Vandewalle

. cc M.* I. Miller, Esquire

• Isham, Lincoln & Beale Suite 4200 One First National Plaza Chicago, Illinois 60670 Mr. Paul A. Perry, Secretary Consumers Power Company 212 West Michigan Avenue Jackson, Michigan 49201 Judd L. Bacon, Esquire Consumers Power Company 212 West Michigan Avenue Jackson, Michigan 49201 Myron M. Cherry, Esquire Suite 4501 One IBM Plaza Chicago, Illinois 60611 Ms* Mary P. Sinclair Great Lakes Energy Alliance 5711 Summerset Drive Mtdland, Michigan 48640

~alamazoo Public Library 315 South Rose Street Kalamazoo, Michigan 49006 Township Supervisor

• Covert -Townshi

.*Ro-ute 1, Box 10 Van*~uren County, Michigan 49043

.:Office of the Governor (2)

Room 1 - Capitol Building Lansing, Michigan 48913 William J. Scanlon, Esquire 2034 Pauline Boulevard Ann Arbor, Michigan 48103 Palisades* Plant ATTN:

Mr. Robert Montross Plant Manager Covert, Michigan 49043 Palisades Docket No. 50-255 Rev. 2/8/82 U. s: Environmental Protection Agency Federal Activities Branch Region V Office ATTN:

Regional Radiation Representative 230 South Dearborn Street Chicago, Illinois 60604 Charles Bechhoefer, Esq., Chairman Atomic Safety and Licensing Board Panel

u. s. Nuclear Regulatory Commission Washington, D. C.

• 20555 Dr. George C. Anderson Department of Oceanography University of Washington Seattle, Washington 98195 Dr. M. Stanley Livingston 1005 Calle Largo Santa Fe, ~ew Mexico 87501 Resident Inspector c/o U. S. NRC Palisades Plant Route 2, P. o. Box 155 Covert, Michigan 49043 James G. Keppler, Regional Administrator Nuclear Regulatory Commission, Region III Office of Inspection and Enforcement 799 Roosevelt Road Glen Ellyn, Illinois 60137

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I RESPONSE TO CONSUMERS POWER LETTER OF 11/13/81 e*

Enclosure l NOTE:

Identification of CPC0 1s comments will be by the page and paragraph referenced by CPCo.

For example, P4Pl will reference CPCo's comments under the heading Page 4, Paragraph 1.

1.

P3P3 - Agree

2.

P4Pl - Agree.

These comments were in the SER in varying detail on pages 5, l 0, and 6.

3.

P4P3 - A basic requirement of current criteria is to compare measured prestress force with predicted prestress force to assure that actual prestress loss agrees with the loss assumed in the initial design.

Reference:

1) USNRC letter from M. Kehnemuyi to B. Lex of Bechtel Corporation, July 27, 1976 and 2) Regulatory Guides 1.35 Revision 3, 1.35.1 issued for comment to clarify R. G. 1.35, Rev. 2, April 1979.

4.

P5Pl - Agree.

5.

P6P2 - The number of tendons tested, as required by R. G. 1.35, Rev. 2 and currently used by CPCo, was chosen in conjunction with the acceptance criteria that measured prestress force be within limits for that specific tendon (or group of tendons).

The number of tendons required to be tested by R. G. 1.35, Rev. 2 was not chosen with the intention of averaging the values ob-tained.

The predicted value of a specific tendon is not arbitrary. It can be calculated and is one component of the average design tendon prestress force.

The average design force required is the value used in the design of the whole containment and predicted to occur at 40 years.

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• 6. P7Pl - Agree.

The difference in measurement technique was pointed out on page 10 of the SER.

7. P7P2 - The 5-year test results can be plotted on a force vs. time curve without the results of other tests.

As stated, you should compare the measured va 1 ues to predicted 1 imi t*s at the time of the test.

Alternatively, the bar graph shown for the 5-year test could have given the predictedlimitS'for each tendon; however, as presented, it was not comparing the measured values to the acceptance criteria referred to in R. G. 1.35, Rev. 2r

8. P7P3 - This part of the SER is referring to the normalized forces.

Since they are normalized, they should not fall below the minimum effective design force.

The increased ISI inspection frequency to which you refer corresponds to the requirements of R. G. 1.35. It is an increased frequency over your initial Technical Specifications. Therefore, the added credit you appear to be giving it only applies to your initial Technical Specifications; there is no incr~ased ISI frequency when compared to R. G. 1.35, Rev. 2.

9. P8Pl - Page 8, Paragraph in the SER refers to reporting tendon force, not wire force.

As an example, refer to tendon 0335 in your 10 year test results.

Figure 5 implies no problems associated with this tendon since Figure 5 shows the results on a per wire basis.

Referring to Figure 8, tendon 0335 has less force than Figure 5 wouldimpl~.-

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e* Finally, the field test sheets show wire breakage since only 88 continuous wires were found.

Figure 8 gives the most accurate representation of tendon 0335.

10.

P8P2 - Agree.

The point of this paragraph in the SER was that the number of tendons tested during the 1 and 3 year tests does not agree with current criteria.

11.

P9Pl - Agree that measurements made during the one and three year tests should not be compared to later test results because of different methods of measurement.

However, they should not be totally ignored since they do give some indication of tendon force.

As discussed on page 11 of the SER, the original method of testing would prob-ably result in values somewhat lower than if the revised method was used.

12.

P9P3 - The acceptance criteria stated in the draft SER do not represent another change in position by the NRC staff; it reiterates what has previously been stated by the staff.

13.

P9P4 - Item 7 in this letter discusses frequency.

14.

PlOPl-Agree that sample size in the Technical Specifications in effect at the time of the 1 and 3 year tests was met.

The method of measurement for the one and three year is discussed in i tern ll of this 1 etter.

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15.

• PlOP2 - Current criteria (R. G. 1.35, Rev. 2) requires visual inspection of the concrete during the ILRT while containment is at maximum test pressure.

10 CFR 50, App. J requires visual examination of accessible interior and exterior areas of the containment before performing the ILRT.

Since the ILRT is performed at one-half Pa,

the benefits fro~ an inspection of the concrete surrounding the tendon end anchorage are reduced.

As a result of this reduced pressure, it would be acceptable to inspect the surrounding concrete during the ILRT only if cracks are noted during the tendon ISI.

You concluded that inspection during the ILRT was unnecessary because there existed no such requirement in your Technical Spec-ifications. The purpose of III-7.A is to evaluate these Technical Specifications and recommend changes.

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e* 16.

PlOP3 - Page 11 of the SER states how the questionable results from the one and three year test could be used to cfraw the conclusion that dome tendons ar~ losing prestress faster than expected.

As stated in the SER, the new test method would result in higher measured forces than values obtained from the original test method.

Therefore, had the new test method been employed during the one and three ye,ar test, the results would be higher and the slope of the loss curve would be steeper.

(The new method requires shims to be knocked loose with a harmner rather than detecting a change in sound.

To do so requires less normal force on the shims).

I Even after reviewing the 10 year test results~.the dome tendon~

still may be losing prestress faster than the originally predicted7 however, it appears that a faster than normal prestress loss would not jeopardize the integrity of the containment between now and the next (15 year) ISL For the average prestress value to possibly fall beJow the average design prestress at 15 years would requite that: 1) 7 of the 8 dome tendons tested during* the 5 and 10 year ISI's had expected prestress values above the average prestress value; and 2) the measured value for one or more of these 7 fell below expected for that respective tendon.

It is unlikely that one can randomly select 8 tendons such that 7 of them are supp_osed to have prestress values greater than the average.

The licensee should verify the foregoing judgement that the dome tendons are not losing prestress at an unacceptable rate between now and the

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-Sa-next inspection by comparing 5 and 10 year liftoff values to predicted values at 5 and 10 years for those particular tendons.

The results of the comparison should be provided as part of the bases for the revised Technical Specifications.

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e* 17.

PllPl - The need to change technical specifications to conform with R. G.

1.35 will be made during the integrated assessment.

Any changes as a result of this SER would not involve hardware changes and ISI continuity can still be maintained; only acceptance criteria would differ in future ISI's as a result of implementing changes noted in the SER.

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PALISADES SYSTEMATIC EVALUATION PROGRAM BRANCH TOPIC I II-7.A TOPIC III-7.A INSERVICE INSPECTION INCLUDING PRESTRESSED CONCRETE CONTAINMENTS WITH EITHER GROUTED OR UNGROUTED TENDONS Io Introduction

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This topic reviews the inservice inspection program of all Category I structures including steel 1 reinforced concrete and prestressed _concrete containments.

The objective is to assure that the licensees inspection program will detect any structurally significant deterioration of Category I structures in *order that the structures will be capable of performing their necessary functions.

II. Review Criteria Review criteria for this topic is Regulatory Guide 1.35 1 Revision 21 "Inservice Inspection of Ungrouted Tendons in Prestressed Concrete Con-tainment Structures," as interpreted in the Standard Technical Specifica-tions dated August 15 1 1979. Also, IS! requirements are described in 10 CFR, Part 50, Appendix J, Part V.A.

III. Related Safety Topics

1. Topic III-7.C, 11 Delamination of Prestressed Concrete Containment Structures."

2. Topic III-7.D, "Containment Structural Integrity Test."

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e* IV.

Review Guidelines With the exception of Containment, there currently exists no inservice inspection (ISI) requirements for safety-related structures. 10 CFR, Part 50, Appendix J,Section V.A., requires a general inspection of accessible interior and exterior surfaces of containment structures for any structural deterioration prior to performing Type A leak tests.

No other guidelines are given.

10 CFR, Part 50, Appendix J is currently being rewritten in TAP A-23 to clarify leak testing requirements.

ASME Section XI is currently considering IS! requirements for steel and concrete containments.

The extent to which this section of the code will be implemented on existing nuclear power plants will be determined when the code is issued and receives NRC endorsement.

Generic issue B-49, "Inservice Inspection Criteria and Corrosion Prevention Criteria for Containments" is developing criteria and requirements to prevent corrosion in an types of containments, but has not been completed and does not have a schedule for completl'on.

Therefore, the only applicable

• portion of this topic is that part dealing with IS! requirements of ten.dons in prestressed concrete containments with current criteria

• defined in Regulatory Guide 1. 35, Revision 2.

Since there has been much discussion, disagreenent and interpretation regarding Regulatory Guide 1.35, Revision 2 by licensees and architect~

engineers, the NRC has recently contracted with Oak Ridge National Lab-orator~ (ORNL) to conduct a study and make reconmendations concerning ISI requirements for prestressed contaimtents. The purpose is to use ORNLs results to assist the NRC in issuing a revised Regulatory Guide 1.35. The ORNL report is expected to be completed by the end of 1981

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9: and the reviseJ Regulatory Guide 1.35 is expected to be issued by mid to late 1982.

Implementation of the revised Regulatory Guide 1.35 on existing plants will be determined after the revised guide is issued.

V.

Evaluation Regulatory Guide 1.35, Revision 2 provides guidance on tendon surveillance in the areas of sample selection, visual inspection, prestress monitoring, material tests and inspections and acceptance criteria.

The approximate time frame followed by the licensee concerning the con-tainment at Palisades is shown below:

Initial Prestressing May-September l969 Structural Integrity Test March 1970 1st Tendon ISI (1 year test)

April 1971 2nd Tendon ISI (3 year test)

February 1974 3rd Tendon ISI (5 year test)

September-December 1975 The 10 year ISI was started in-May 1981 and completed during the summer of 1981.

The time intervals between inspections.conform with current criteria. The licensee, after reviewing the results of the 1, 3, and 5 year tests, concluded that the-tendons at Palisades are experiencing no abnormal degradation and are continuing to perform their required function.

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A.

Current Criteria For the 1, 3, and 5 year inspections, current criteria requires the inspection and liftoff testing of 6 dome tendons (2 from each 60° group), 5 vertical tendons randou?ly and representativaely distributed and 10 hoop tendons randomly and representatively distributed. If these results *indicate no problens in the tendons, sample size for the 10 ye5;A ;ind subsequent inspections is decreased to 3 dome tendons, 3 vertical tendons and 3 hoop tendons.

Visual inspection of tendon anchorage assembly hardware and surrounding concrete is required.

The concrete around the anchorage should be checked during the integrated leak testing while the containment is at maximum pressure. Liftoff testing requires measurement of jacking force and elongation and comparison of these to predetermined allow-ables.

Tendon detensioning is required to identify broken or damaged wires.

Wires from one tendon of each type (dome, hoop, vertical) should be remo*!ed for examination for corrosion and tensile testing. Three tensile tests are required from each wire. Sheathing filler grease c

must be inspected for grease coverage of the anchorage system,

influence of temperature variations, voids in the trumpet, and requirements imposed by grease specifications.

Acceptance criteria are that the prestress force for each tendon should be "within the limits predicted for the time of the test."

There should be no more than one tendon value ou~side of these limits.

If one tendon is found outside these limits, one tendon on each side should be tested. If both of these are found acceptable, the low reading tendon is considered unique and not indicative of a problen;

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• • • ~*M-however, if either of these adjacent tendons also reads low or more than one tendon in the entire group of similar (d~me, hoop, vertical) tendons reads below set limits, it is considered un-acceptable. All tensile test values should be greater than or equal to the guaranteed ultimate strength of the material.

B.

Testing Requirements at Palisades The technical specifications at Palisades were originally written before the issuance of Regulatory Guide 1.35. After the three year test, the specifications were changed to conform with Regulatory Guide 1.35 and Standard Technical Specifications in effect in November, 1974 and were used during the five year ISI.

The one and three year ISI's were performed using the original Technical Specifi-cations.

During the one year inspection by the licensee, three hoop tendons, 20 vertical tendons (three initially, two additional to account for one low reading, and 15 chosen at random), and three dome tendons (spaced 120 apart) were tested for liftoff *and wire continuity.

End*

anchorage assemblies were inspected. Wire inspection and mechanical tests were performed on one wire from 11 tendons.

Sheathing filler was laboratory tested for deleterious materia*1.

The three year in-spection by the licensee consisted of liftoff testing 16 vertical tendons, three hoop tendons and three dome tendons.

Eleven of these tendons were the same ones tested during the one year test. Wire inspection and mechanical tests were again performed on wires from the original 11 tendons.

End anchorage assemblies and sheathing filler grease was inspected as before.

\\, In the 5 year inspection, the number and location of tendons tested for liftoff and wire continuity confonned with current criteria.

None of the tendons selected had been tested previously. Wire inspection and mechanical testing was perfonned in accordance withe Regulatory Guide 1.35, Revision 2.

Tendon anchorage hardware and surrounding concrete was inspected. Sheathing filler was labora-tory tested for contamination.

C.

Discussion The tendon surveillance program now in effect at Palisades ;s in substantial conformance with current criteria defined in Regulatory Guide 1.35, Revision 2; however, there are deviations, some of which are not acceptable and discussed below.

For all three tests, acceptable liftoff test limits were the minimum effective design prestress as the lower limit and.73fs as the upper.

The upper limit is required as it is an indication of an abnonnality if tendon prestress*force is too high and also some concrete degrada-tion may occur if tendon prestress is too high. The lower limit is the force relied on to resist design loads. Regulatory Guide 1.35, Revision 2 requires that the prestress force.measured for each tendon be within 1 imits "predicted for the time of the test."

Regulatory Guide 1.35, Revision 3 and 1.35.1 that were issued for cormnent* clarify the intent of the present Regulatory Guide 1.35.

The intent of Regulatory Guide, Revision 2 is that the limits for each tendon vary with time so that one can identify trends in the rate of prestress loss. Measured tendon forces for each tendon should be within these limits and not average tendon force.

The objective is to track prestress force loss with time so that rates of prestress loss can be determined and compar~d to these assumed in design, thus identifying potential problems before they actually occur.

Results of the one year and three year liftoff tests were plotted showing normalized force per wire versus time; however, acceptance criteria remained constant with time.

The normalized liftoff force is the measured liftoff force which has been modified to account for elastic stress loss during initial installation and for liftoff force deviation from the base value.

By normalizing the measured liftoff force, a common base is established for compar.i sons.

The results of the five year liftoff tests were presented in a bar graph, thus losing the time dimension completely. This was done because the method of measurement and Technical Specifications were changed.

For future tests, plant technical specifications do not require acceptance limits which vary with time.

I For Palisades, the minimum effective design prestress value and the predict~d prestress value converge as ti~e progresses. There-fore, the range between the expected 1 oss curves and the minimum effective design prestress curves decreases as time approaches 40 years.

As a result, it is expected that more tendons will exhibit value$ below the minimum effective design prestress value in the future. This may require that future inspections of tendons be conducted at more frequent intervals than currently required. In addition, renedial action may be required if the actual losses were not appropriately enveloped by those considered in the containment design.

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~-'. - As stated, the liftoff test results for the one and three year tests are presented on a graph whose axes are normalized force1per wire versus time.

Presentation of results in this manner does not show problems associated with wire breakage. It is possible to show an acceptable wire force in a tendon that has an unacceptable tendon force by dividing the unacceptable tendon force by the number of effective wires when there is excessive wire brea~age. Therefore, liftoff test results should be shown as tendon force versus time.

Even with wire breakage, wire stress must still be maintained below an upper acceptable limit during any retensioning.

The one and three year inspections deviated by liftoff testing a smaller sample size of dome and hoop tendons and by testing the same tendons in both tests. These tests were in conformance with the Technical Specifications in effect at Palisades at that time.

The sample size was in agreement with current criteria for the five year test.

Current criteria requires visual inspection of the conrete surrounding the tendon anchorages.

The visual inspection is to take place during the integrated leak test while the containment is at maximum test pressure.

The technical specifications at Palisades (section 4.5.5.b) do not require this inspection during the integrated leak test.

VI.

Canel us ions The containment tendon surveillance program at Palisades largely conforms with current criteria but has some unacceptable deficiencies.

A method of checking prestress loss with time and a graphical presentation of the results is necessary.

Force at the time of the. test for each tendon should be compared to that assumed for that particular tendon in the design.

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. -*. **--* ----* -- --* - -*---**- - - Palisades' Technical Specifications, Section 4.5, Page 4-36, state that force-time records will be established and maintained for each tendon group (i.e., dome, hoop, vertical). This was totally disregarded in the five year test for the reasons given above.

The graphs should show tendon force not wire force ver-sus time for reasons given in the evaluation.

The staff has done this from some of the values and shown them in the attached Figures 5-1, 5-2, 5-3. A normalization factor of 0. 97 was assumed for the five year test data by averaging previously given normalization factors for other tendons which had never been liftoff tested. Also, the three year values for vertical tendonswhich were concluded to be questionable due to method of testing were not included.

,Graphs prepared by the licensee should use actual calculated nor-malization f~ctors 1 excluding the term to account for missing wires.

Alternatively, normalization need not be used but actual force should be compared to limits predicted for that tendon.

Acceptance criteria should be established which vary with time.

An acceptable method for future inspections would be to specify upper and lower acceptance 1 imits *for tendon forces which vary with time, envelope the expected loss curve, and maintain the lower limit above the minimum effec~ive design prestress. Current plant technical specifications should be changed to reflect this.

1A factor to bring each tendon to a convnon base such that it would be the same as comparing each tendon to requtred values for each particular tendon.

I Since the expected loss curves approach the minimum effective design prestress at 40 years, more* frequent inspections may be necessary in the future than now required. This should be determined after review-ing the results of each future inspection.

The one and three year inspections liftoff tested smaller samples than currently required, but this deviation is not judged to be significant since all five year test values where higher than the minimum effective design prestress values.

Also, one and three year prestress values would have a larger margin between expected and minimum effective design values.

The one and three year test results should be viewed with caution because the method of determining liftoff was changed from detecting changes in sound when striking shims with a hammer to actually moving a matched or mated pair of shims.

This latter method of measurement was found to be the least subject to interpretation. Additional one and three year data would have been useful to establish trends in prestress loss, but had additional tests been performed the results would have to be viewed with caution also and would be marginally useful since they would have been tested using the original method.

To establish reliable trends, the method of testing must remain constant.

Therefore, using smaller one and three year samples is not judged to be significant.

Concrete surrounding the end anchorage of prestressing tendons liftoff tested during the previous tendon inspection should be visually inspect~

during the integrated leak rate tests while the containment is at maximum test pres~ure if any cracking is noted around the end anchorage during the tendon IS!.

The surrounding concrete should be viewed for any unusual cracking during the tendon !SI. Cracks larger than.01 inch as described

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tn ASME Section u1*. Division 2. Subsection CC-6000 should be noted and evaluated.

Any changes should be noted and evaluated during sub-sequent inspections.

BF-65 and DL-38 appear to be losing prestress at a faster rate than expected.

Even viewing one and three year dome tendon results with caution, it appears that dome tendons may be losing prestress faster than predicted. This would be even more likely if the one and three year results were actually higher than shown as they most likely would be had the 5 year testing method been used.

Results of the 10 year ISI still indicate that dome tendons may be losing prestress at a faster rate than originally anticipated. To assure that the.containment is behavtns; as expected, each tendon should b.e compared to a.ccepta.nce crf-teria for that.particular tendon. Although thts was not done at Palisades, liftoff test values for the three dcme tendons tested during the 10 year ISi were substantially above the average design force.

It appears that a faster than nonnal prestress loss would not jeopardize the.integrity of the containment between now and the next ISi. For

• the average prestress value to possibly fall beJow the average design t'

pr.e_stress at 15 years would require that: l) 7 of the 8 dome tendons

.tested* during the 5 and 10 year ISI' s had expected prestress values above 1;he average prestress value; and 2) the measured va,lue for one or more of these 7 fell below expected for that respective tendon.

It is un-likely that one can randomly select 8 tendons such that 7 of them are supposed to have prestress values greater than the average.

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-lla-The licensee should verify the foregoing judgement that the dome tendons are not losing prestress at an unacceptable rate between now and the next inspection by comparing the 5 and 10 year liftoff values to the predicted 5 and 10 year values for those particular tendons.

The results of the comparison should be provided as part of the bases for the revised Technical Speci fi ca ti ans.

The above changes should be incorporated into the Technical Specifications at Palisades.

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Enclosure* 3

• consumers Power Campany o.ner.i Offlcel: 212 W*t Mlchl1111n Annue, Jeckeon, Ml -'9201 * (517) 788.o&ISO Bovember 13, 1981 Director, Nuclear Reactor Regulation Att Mr Dennis M Crutchfield, Chief Operating Reactors Branch No 5 US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-255 - LICENSE DPR PALISADES PLANT - SEP TOPIC III-7.A, ISI INCLUDING PRESTRESSED CONCRETE CONTAINMENTS WITH EITHER GROUTED OR UNGROUTED TENDONS By ietter dated August 25, 1981 the NRC issued for comment a dra:N; evaluation of SEP Topic III-7.A for the Palisades Plant. Attached are the Consumers Power Company comments on that document.

R A Vincent (Signed)

R A Vincent Staff Licensing Engineer CC Director, Region III, USNRC NRC Resident Inspector - Palisades l-

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• SEP SAFETY TOPIC ~'VAWATION PALISADES PI.ANT REVIEW OF NRC EVALUATION FOR TOPIC III-7.A, ISI INCWD!NG PRESTRESSED CONCRETE CONTAINMENTS WITH EITHER GROUTED OR UNGROUTED TENDONS

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The following information documents our review or the NRC Draf't Evaluation regarding this topic.

Our comments are shown using paragraph designations

• as they appear in the NRC Draf't Evaluation.

V.

Evaluation Page 3, Paragraph 3 The ten-year containment building tendon surveillance (ISI) was started in May 1981 and completed prior to issuance of the draf't evaluation.

The NRC Staff on site, in Washington and Chicago were notified of this inspection.

V.

Evaluation A.

C°'.lI'rent Criteria Page 4, Paragraph l -

The Draft Evaluation needs clarification. The original plant Technical Specifications were wTitten prior to the issue of Regulatory Guide 1.35.

The one-and three-year ISis were conducted u5ing the original plant Technical Specifications which defined the number of tendons to be inspected in these years *

. Subsequent to the three-year ISI, it va.s apparent. the definition of tendon "lift-off" was subject to individual interpretation and needed to be objectively defined, Reference (1).

In the period between th~

three-and five-year ISr'~ the Architect Engi.neer and Consumers Po~e.r Company performed additlonai work to develop a measurement technique that would appropriately define tendon "lift-of:f."

• The tendon lift-off measurement technique that was developed, called "all shims loose," was tound 1i.o be the least subject to interpretation.

During the above period, the overall ISI program was changed to make it consistent with Regulatory Guide 1.35. Specific Technical Specifications revisions were as follows:

(l) 'ro increase inspection frequency of ISI to provide assurance that the tendon syst~m is per:formine as

• desir,ncd or to provide more rapid detection of any deterioration of the tendon system if it should occur.

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2 (2) To increase the data base sample size of tendons

( 21 tendons ) to be inspected in the five-year ISI because of the questionable results found during the one-and three-year ISI.

(3) To change the acceptance criterion for measured tendon li:f't-off force determination:

From:

A previous requirement to plot and extrapolate measured li:f't-off forces to forty years (forming a force/time trend line).

To:

Require measured li:f't-off forces to fall between upper and lower bounds vi thout extrapolation of data points as proposed in Regulatory Guide 1.35 and the Standard Technical Specifications, Ref (2).

Approval for these revisions appeared in Amendment #14 to Provisional Operating License #DPR-20 for Palisades which included Change #18 to the Technical Specifications.

The five-year ISI was based on these revisions.

The ten-year inspection criterion (sample size of nine tendons) is correct as stated in the Dra:f't Evaluation.

Page 4, Paragraph 3 Dra:f't Evaluation states "Acceptance criteria are that the prestress force for each tendon should be within the limits predicted for the time of test.

11 This requirement is questionable since it now makes acceptance and the amount of tendons in the sample a function of the designer's ability to predict very small loss values.

Losses are originally conservative based on testing; and using these losses, the minimum amount of prestress in the average tendon is determined. If prestress limit is too loose, then the criteria may be meaningless; if too tight, the sample may increase by a large amount causing unnec-essary work and difficulties in analysis even though the containment is SOUnd.

B.

Testing Requirements at Palisades Page 5, Paragraph 1 Add underlined information to Dra:f't Evaluation.

11A:f'ter the three':"'y~ar

• tests, the specificatiQlls were changed to conform with Regulatory.Guide 1.35 and Standard Technical Specifications, Reference (2) and were used during the five-year.!§! (test)

• C.

Discussion Page 6 2 Paragraph 2 The tra:f't E"raluation states Measured tendon forces for each tendon

• should be within these limits and not average ~endon i"orce.

11 Our Architect Engineer uses average tendon force.

They feel the acceptance criter~a should be based on (a) the average li:f't-off of the sample since the original design was based on the average tendon and (b) the minimum effective force required and not some artitrary predicted value.

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3 Our records show a difference of opinion between our Architect Engineer and the NRC Staff regarding the average tendon force (and other tech-niques), References (3) and (4).

Resolution of this issue is not known by Consumers Power Company~

Page 7, Paragraph 1 The data resulting from the one-and three-year ISI were considered questionable because of apparent variations in tendon lif't-off force caused by measurement technique, Reference (1).

The one-and three-year ISI shows normalized tendon lift-off results because of the requirement in the Technical Specifications in effect at that time.

The five-year ISI was based on using the acceptance criteria set forth in the revised Technical Specifications.

Reference our comments under Section V-A, Page 4, Paragraph 1.

Consequently, normalization was not necessary.

Page 7, Paragraph 2 We agree with the draf't evaluation that a force/time graph should be maintained.

However, because of the variations found in the tendon lif't-off forces caused by measurement technique in the one-and three-year ISI, the force/time graph was not maintained.

The lif't-o~f forces for the five-year ISI were presented in bar graph form because this represents the only set of data available using our current accepted measurement technique, "all shims loose."

As the ten-y~ar, fif'teen-year, etc, ISI tendon lif't-off results become available, they will be plotted with the 5-year results using a force/time graph.

Page 7, Paragraph 3 The ~aft Evaluation states "the minimum effective design prestress

.value and the predicted prestress value converge as time progresses.

Therefore, * * *

• As a result, it is expected that more tendons will. exhibit values below the minimum effect.ive design prestress value

. in* the future." If this proves to be correct, then the approach taken

. by the* Architect Engineer in Reference ( 3) would be appropriate and would still provide assurance that the contaiillllent is sound.

Furthermore.,

our Technical Specifications already specifies that measured lif't-off forces should fall between absolute upper and lover bounds with the lower bound providing a minimum effective prestress value for tendon types.

This minimum value is fixed (not a variable) and could not be changed without a further evaluation of ISI program. If, for some reason, the ISI shows the lif't-off force of.a given tendon~ a.ropping below the minimum value, an evaluation is required for the tendons on either side of tlte one in question to provide resolution. Furthermre, we have already.

increased the ISI inspection frequency to provide a more rapid detection,**

of' any deterioration in the tendon system if it should occur, Reference C5)

• 4

. =*

It is believed our current ISI requirements in the Technical Specifi-cations are more conservative than those shown by the Architect Engineer, Reference ( 3), and probably as conservative as the theoretical ISI requirements shown in the Draf't Evaluation by the NRC and in Reference (4).

Page 8, Paragraph 1 Problems associated in the one-and three-year ISI were discussed earlier;

~eference our comments under Section V-C, Page 7, Paragraph 2.

Norm-alization of tendon lif't-off values was addressed earlier; reference our comments under Section V-C, Page 7, Paragraph 1.

Page 8, Paragraph 2 It is our understanding that the sample size for the one-and three-year ISI was within the requirements of the Technical Specifications in effect at that time.

VI.

Conclusions Page 8, Paragraph 2 (cont'd Page 9)

A graphical presentation of the tendon lif't-off results will be made in future ISI reports; reference our comments under Se~tio~ V-C, Page 7, Para-graph 2.

Page 9, Paragraph l Contrary to the Draft Evaluation, we believe the one-and three-year ISI data (regarding tendon lif't-off force) should be ignored because of ques-tionable results caused by measurement techniques, Reference (1).

Therefore, this data should not be plotted on the same graph.

The data base for tendon lif't-off forces should only include results from the five-year ISI (1975) and later ISI which use our acceptable measurement technique of "all shims loose." Normalization has already been addressed.

Page 9, Paragraph 2 Normalization has already been addressed.

Page 9, Paragraph 3 During the development of Qur current ISI, many differences of opinion nave surfaced over the past decade regarding acceptance criteria. Examples.. of

• these differences are shown in References (3), (4) and (5).

The acceptance criteria specified in this Draf't Evaluation represents* another change in position by the NRC staff which is confusing to Consumers Power Co and our Archiotect Engineer.

Contrary to the Draf't Evaluation, we believe that no changes should be made to the current Technical Specifications until Revision 3 to Regulatory Guide 1. 35 is issued.

Our current ISI program is adequately performing its intended function and no specific safety concerns are outstanding at this point in time.

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Page 9, Paragraph 4 We have already increased our inspection freque~cy during ISI to provide a more rapid detection of any deterioration of the tendon system if it should occur.

Reference our comments under Section V-A, Page 4, Paragraph 1 and Reference (5).

Page 10, Paragraph 1 It is our understanding that the sample size for the one-and three-year ISI was within the requirements of the Technical Specifications in effect at that time; reference our comments under Section V-C, Page 8, Paragraph 2.

We agree with the Drafi Evaluation that the one-and three-year ISI prestress values should be viewed with some caution; in fact, they should be ignored because o'f the change in measurement technique.

The five-year ISI program used a measurement technique of "all shims loose," ie, the moving o'f a matched or mated pair of shims to determine tendon lifi-of'f 'force.

Page 10, Paragraph 2 The ILRT and ISI are not completed in the same time 'frame (period).* This makes the request in the Draft Evaluation for inspection of cracks in the concrete surrounding the end anchorage of tendons (tested in the previous ISI), a safety concern and extremely costly because ISI requires work high above the ground level and special equipment.

A crane, skyclimbers, etc are necessary to provide access for the tendons to be inspected; special rigging of this equipment is necessary.

We are inspecting 'for cracks in the concrete during ISI, Reference (6),

and believe from our findings that this additional inspection is not warranted and would have little value in determining containment integrity. It should also be noted that the ILRT is conducted at approximately one-hal'f containment design pressure (Pa), not at maximum (test) pressure as shown in the dra~

evaluation.

Because of the above and with no requirement for this additional inspection in the Technical Specifications, we conclude this requirement is not necessary.

Please note the Dra~ Evaluation also addresses the-ILRT in two previous paragraphs; reference Section V-A, Page 4, Paragraph 1 and Section V-C, Page 8, Paragraph 3 Page 10, Paragraph 3 The ten-year ISI was completed prior to issuance of this Drafi Evaluation; reference our comments under Section V.

• ISI is now completed every five years and normally performed in good weather conditions while the II.RT is performed during a refueling outage which is not contingent on weather conditions.

---

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We agree with the Dra:rt Evaluation to include tendons BF-65 and D l-38 in the next ISI inspection.

We do not, however, agree to select an additional randem tendon as proposed, as VP. have already completed our ten-year ISI which includes tendon selection on a random basis. All the tendons inspected in the ten-year ISI met the li:rt-off acceptance criteria in the Technical Specifications.

A report to the NRC is forthcoming.

-Page 10, Paragraph 3 -(Cont ' d Page 11)

The Dra:rt Evaluation states "BF-65 and D 1-38 appear to be losing prestress at a substantially faster rate than expected.

Even viewing one-and three-year dome tendon results with caution, it appears that the dome tendons may be losing prestress faster than predicted." Even though ve have committed to inspecting tendons BF-65 and D 1-38 above, we believe these conclusions could not have been reached based on data from the one-and three-year !SI because of questionable results from measurement techniques; reference our comments under Section VI, Page 9, Paragraph 1. The data base for tendon

• li:rt-off forces should start 'With the five-year !SI (1975) results; reference our comments under Section VI, Page 9, Paragraph 1.

Page 11, Paragraph 1 We agree with the Dra:rt Evaluation that any proposed changes should wait until Revision 3 of the Regulatory Guide 1.35 is issued.

However, we do not agree with all the proposed changes in the Dra:rt Evaluation (the changes agreed to have been so stated) and strongly feel the NRC Staff shoUld allow older plants certain flexibility when changing Regulatory Guides so that they can maintain continuity in the current !SI program if there are no safety concerns for the general public. Apparently, our containment meets this requirement; reference Section VI, Page 8, Paragraph 1 in the Dra:rt Evaluation.

We believe that because of our very conservative containment design the current ISI program which conforms to the early Regulatory Guide 1. 35 and the standard Technical Specifications, Reference (2) and the satisfactory results obtained from the five-and ten-year ISI, that our current inspection program should be maintained at this time.

As shown in our comments under Section VI, Page 9, Paragraph 3, there are no sart!ty concerns outstanding at this point in time.

.. ~ -

(1)

REFERENCES Consumers Power Company letter Sewell to O'Leary NRC discussing Containment Building Post Tensioning System Surveillance Report dated February 1974, letter dated April 29, 1974.

( 2)

USNRC informal memorandum C Tramell to DABixel Containment Systems Con-tainment Structural Integrity (Standard Technical Specifications) dated 11/21/74.

(3) Bechtel Power Corporation letter from B L Lex to R M Minogue of NRC; *subject, "Regulatory Guide 1. 35, January 1976, Revision 2, 'In-Service Inspection of Ungrouted Tendons in Prestressed Concrete Containments' - Comments,"

• dated May 6, 1976.

(4)

USNRC letter from M K"ehnemuyi to B L Lex of Bechtel Power Corp; subject, "Your Comments on Revision 2 of Regulatory Guide 1. 35, dated May 6, 1976."

dated July 27, 1976.

• ( 5)

USNRC letter R Purple to RYoungdahl, Issuing.Amendment #14 to Provisional Operating License #DPR-20 for Palisades Plant dated 4/24/75.

Includes Change #18 to Technical Specifications and Safety Evaluation Supporting

.Amendment #14.

• (6)

Consumers Power Company letter DABixel to*R Purple, NRC "Enclosing Containment Building Tendon Survellance - Five-Year Surveillance Palisades Nuclear Plant dated March 1966," letter dated March 26, 1976.

• Not enclosed * *

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I eeneret omces: :u2 west Michl;*"-.-*.,,.ckSOft. Mlchlgen *9201

• are. COCle IH7.,***O&&O Mr. J C\\hn F. 0 'Leary, Director Directorate of Licensing.

US Atomic Energy Commission Washington; DC 20545

Dear Mr. O'Leary:

.Apri1 29, 1974 Re: Docket 50-255

• License DPR 20 Attached is a copy of report titled "ConsUJDers Power Company Palisades Nuclear Power Plant Containment Building Post Tensioning System Three-Year Surveillance," dated February 1974.

This report, pre-.

pared by Bechtel Corporation,- describes the surveillance of the Palisades containment building post tensioning system.

!bis report bas been reviewed in detail by Consumers. Power Canpany.

We feel that.the testing performed demonstrates that the exist-iD& tendon forces are in accordance with the desig.~ objective3 cf t!ie containment structure. In addition, there were no broken wires since the last inspection and there were no signif:i.cant cha.?Jges in ~he corrosion con-ditions or grease properties. However, the *testing perfonned to date bas not been adequate to determine a force-time trend line for each tendon ~s required by Technical-Specification 4.5.4d2.

• Studies were performed to determine variations that might be expected due 'f!o the measurement technique used in the tendon surveillance.

!he measurement technique used in the first year surveillance as well as the scheduled three-year surveillance showed ten percent variations in stress in tendons, except that the stress in Tendon V 2o4 was measured to be 1'4 percent below the predicted stress.

(Tendon V 204 was. evaluated to be below 1hc required force level in the first ye~r surveillance as well.)

'!he ori(;inal. testing techniques provided for increasing the tension in a tendon until one of a pair of shims came loose. 'The variations were-in part due to the differenc~s in thickness of' the two shims.in o. pair.. The thiMer shim would be reUeved of load while the thicker shim stiil".. c!!"-

ried a portion of the tendon load. A description or the probl~s assst?i-ated with this test method is contained in Appendix F of the report. ~

(,C)

Because of the apparent variations in tendon lif't-01'1" forc8',

caused by the measurement technique, an addi tiona.l tendon surveill.nn~

.effort l:ns W1_d:crts.ken in the fnll of 1973. This effort included detc:>-

minins the lift-oi1'. forces of the ~ack when all shims in the sto.clt b.ecamc.

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Mr. J obn F. O'Leary-, Director Docket 50-255 License DPR 20 April 29, 1974 loose as well as veri:!'ication of the lift-off' measurements 'b:I' deter-mining sase pressure versus tendon elongation..Consumers Power com,Pany

~eels li:ft-o:r:r forces measured by the "all shims loose" method indicate

• that the tension in the tendons varies less than 3.0 percent above or

. below the expected tension. This range of measurements is relatively

• ir.maJ.l considering the tolerances in the measuring and calibrating devices (expected to be about t~) and considering the judgment factor inherent in the testing method itself. Al though it has been concluded tha.t the.

containment prestress is at adequate levels, the methods used to date do not pennit predicting trends, since their results do not tend to be re-peatable. It is our intention t.o develop a measuring technique that will eliminate human error insofar as it is possible. The results of measure-ments ltlll hopeful.1.y pem5 t extrapolation of the' force-time curves in the

1. Utur~ when the tendon surveillances are made at five-year intervals.

~cause of. the inability to detennine a force-time trend line *

~~~don the pne-year and.three-year surveillance tests already performed, the tendon surveillance program ll'ill be changed to include surv.eillance

~~sting in 1974 and.1976 before adopting a five-year interval. Testing i;ecbniques are being reviewed in an attempt to develop a techriique that giyes repeatable results with an acceptable degree of accuracy

• The attached report has been reviewed by the Safety end Audit

~eview Board.

Thei;r findings are also attached.

Yours very truly.1 Balph B. -Sewell (Signed)

ImS/pb.

Balph B. Sewell Nuclear L~censing Admini,strator CC:

JGKeppler, USAEC r:*

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!'endon Surveillance Report

c. A. Hunt reported.on tbe Tendon Surveillance RepOTt published by Bechtel Corporation. The principal. results were discussed.

SARB eX8l!l-ined the report in light of the requirements contained in Section 4.5.4 of the Palisades Plant Technical Specifications.

Surveillance for Pl'estressing System 11a. The nine surveilla.nce tendons shall be periodically inspected for symptoms of material deterioration or force reduction.

'fhe surveillance tendons consist of three horizontal tendons, one in each of three 120° sectors of the conte.inm!?nt; three 0

vertical tendons located at e.pproximatgly 120 apart; and three dame tendons located approxima. tely 120 apart."

• **SARB Finding - The testing satisfied this requirement.

"b. The inspection intervals, measured from the date of the initiai structural test, shall be as follows:

(1) One year.

(2).!l'bree years.

(3) Every five years thereafter."

• • SABB Finding - The testing met the letter of the interval*requirement but, since the tests were not exactly comparable, the data generated mu.st be considered new* baseline data.

• c. Ea.ch surveillance tendon shall be inspected for the following:

(l) The number of broken wires.

(2) The surveillance tendon force at the end anchor.

(3) The corrosion and other physical conditions for the tendons, including bearing plates and end anchor assemblies *. The inspection procedures include removal, inspection and test-ing of specimens from not less than one nor more than five wires from each of the nine tendons.

'rbe grease will be sampled and tested. n

• • SARB Finding - The testing satisfied this requirement.

"d.

Comparisons shall.be ma.de between the quality control r~cords and each of the surveillance inspection records for each o~ t.lie slirveillance_ tendons. Acceptance criteria for paragraph ( c) i.l_

• as follows:

c (1) Ho additional. broken wires since last inspectfon.

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(2) The force-time trend line for each tendon*as extrnpolated.n sha1l not intersect eith~r the !JJ?per or lower bowids of c.c the predicted dcsiGU band.

(3) No unc~-pectcd ch!lnse. in corrodon conditions or gease a, properties."

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• ff.sARB Fincling - 'rhe testirie showed.that acceptance cri terin. (1) and (3) had been met. It was doubtfUl that acceptance critc:-ion

• (2) was met. It w.s pointed out in the discussion that it may be a meaningless criterion. A study on this point appeared to be necessary.

ae. If the criteria stated i.n paragraph (d) are not met, an inves-.

tigation shall be undertaken to determine and correct the cause for the changes e.nd a report made to the AEC as specified in Section 6.6.

11

• • S.h.RB Finding - It. was not absolutely clear that all the criteria in (d) had been met...

SA.~B Conclusions

1. The c9ntainment tensioning is adequate and the facility can be used i'or the purpose intended *.

2. Sufficient information was not presented to verify the

_adeq~cy of the stress versus time trends.

SARB Recommendations

1. The AEC should be notified of* the ~sults of the testing *

2. An acceptable test method, especially with regard to repeat-ability, should be developed to comply with the Technical Specifications requirements.

3. Retesting should be done one year and three years from the latest test date, using.the acceptable test method in 2 above.

4..

C. J. Maynard should be assigned to follow and coordinate the contacts* 'to *be made with Bechtel Corporation on 'this issue, and report be.~.to SARB on its disposition

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.6.1.7 The structural i!"lt2grity of the contair.m!nt shall b~ r.aintain!"'J t a leva1 comparabie to tr.e original acc~ptance stand~rcls.

rPPUC::.3ILI'!Y:

t-:OOES 1. 2. 3 and 4.

• tTIO~i

llith the struc:ural ir.t~".!rity of th~ :or.t;i ir=:ent n:>t eo:ifor::ii:i.1 to !~~

brigi::-!l ac::~;:>::rc~ 'it<lr.C':!r:s, restJre th!! s;:r~ctural in::;:-ity to *.1i~:i

~r. the li'1its ;Jrior to incr~asing t~e R~actor Cooiclrat S.:;ste:: te::::;:erat:.:-~

rbove 2co,;);:.

~t~~*.

1 :! l t.~. ~~: ?. ~ :':J !~ ?-.:'~2JiS r.

~ ---------

I I. r:_ l ~* l

,.,,...*.:-::.~- T,.... *"r."

Thn C.,.,..,.;.,_,,,.... '""n<1"l"'S 1 **r.......... _.l

!"'*:,)* ****

~_

.. ::~--*.:_-__...;..*.:-:..... '"'-'...,.

,1 -

~*-

"""--*-*I;*

-~>.:r~rit:** ~::~.a L~.::.. ::;::::~.. \\.:.~ ~:zri:-:~~ :;l~*zt~:l:*'l ~:ti:*.~ c:r.:J of !l~*~. r:ir~"i'

~.:r.:j. ii*1e._.:::.:-~

fo:r.,~:1:? :-:-:~ in~ti.;l ccr;r.1ir*~:-n!: str:Jct:.:r-,:,1

~rt*:!:;rf~y

~*st ~r.~.

?t fi*1e yr,.!r 1n

:?r-.*~l:; th'~,-~.:lft~r.

T;~..? ttnC::rns' str!lc.tura1 r;r~!::-;r'lty !>hail be C~!"OT:Stri:tCd t-y; I

a. re::e:-::iinir.g t~at a r~presentativ~ sa~~le of at l~ast 21 t!ndons (ci co:r.e, !i \\'c:?r-tical, ~nd 10 hcop) c~::1 have a lift off force of bet:*;eeri

(;:lirii~1::::) end (r;?icir.*.::i) po:..inds.

If !.h'! lift off force or u:.v one tt>r.don"l'ilth~ totJl S&:::'l:lle po;:iuli!tic.n i~

c;it of t!t! r-r~dictc:J ho:;:'l:!S (lt?ss t.':an r:1inir:w;1 O!" gr~.:?ter th.Jn r..!xi:::1..":1j, an edjac:?nt terc:in on each si\\!~ cf th!! d~f;-C'tive

!~r:dJn sh::l l.:lso !:~ cbl:;<?c! icr 1 ift of<f fore:~. If b:.!'i of th~e i:?n~or.s.::re foi:~d accM::able, the surveillance prCJ:;r&i::rni!:'

i:rec:eed cor.siti=-rir.3 the sin;le c!2ficic.'ICj' as ur.iqu! ami acc:t?;l":-

!ble.

r-:~'re th.:m one cefei:tive t.:-ndo:i out of t!'l~ ori9ir:3~ s~~pl~

p!)~ulation is evicenc:~ of <?b::nr.:ial d~gr~daticn of th;? cor.tJ'in-

~ent struc:t~r:?.

c~1~ss there is cvider.cc of..abn~:7-:~i c~;racJ!:~~

of the cont~ ir":'.?nt Struc:t:Jr:? d11ring the first t.1re?t! t~sts of..::..:-

ti-neons, the r.nb!r of c~r~cns chec~ed for '1 ift off" fore!! <!uc:r.~ -

su~s<?quent t~sts r.:ay be reduc~d to,. r-:?~resentative Sl\\',1;')lQ o~

at 1east 9 t~r.:ons (3 d:ir.e, 3 vertical and 3 hoop).

v. -- '

f *t-.o.r.:JSP:if:HC 3/4 6-lOF co.

0)

CD

0)

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,,,~

t

--*~-*--------***-- ****~----......... _,, __ *.. --

I

• *.. r;_*-

J--------

• see

. uo..

.... !'!4 *. 41.

. *.:**. -r I l

• f I j I

I l r* l

t r t I.

t i

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I r

i '

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t f

i I

• 1 '

1 i 1

i I l t

l i I J 1 4

l l 1 I

' i l t l I

i I

(

. {

I *r.*1r* ~--*:-**r s**sT:--*~

I.

,)

~.

r.~r.:cvir.:; cme '1ire or strand frr, each of A C:o:':".e, vertical and h\\>Op tc:i:hn c!i:.-ck~d for lift off force ar.d cfoteminir.~ that ov~r t:1~ entite ler'lt!l of t.~a rerove.! wire or strar.d that:

1. The tendon uir:?s or s :rar:c!s ilre @of corrosicn.

2.

3.

,. *. *- *.... * ~,.:"'",....,... *" ***s1*--.1

• • • • -*- -*\\:"'**-**-'*-*--*,,,..........

sl.?.:. ti1 ;r.; 1 i l i e:r c;re-4se.

A ~ini:'"!;~ tensile strcnr.th of Doun~s for at le3St thrt':? u~rP or strar.~ !>a~;;les (c.re fri::1 f:.!th er.j !.m! one at r1i.:-h-r.c;th) cut. frcr: earn ri:;'."',;wed tc:r.:!on.

!".~nure cf any c_~"Jof tr.e tc:i,'on s~:-:pk;o t.' :-~?t t!1: ~'ini~:"": ::nsilfl str*:.:.~t:i ~~H ~s P.\\':*. ::;.:~ uf a~no1-r:al dcr.raJation of t!1e cent.: ;.~.:.:r.~ str:ict"r~.

~.G. l.7.2 [!'.d :.-::~".'r**-""!> :-r:.:I :..*1t*.c<?'lt :-::~i::rnt? ~*J~fac:t?s

'rh~ $truct:.irl1

-=-:-:-:;;-.::=*..... r.....,.' ::...,,~*;..

",...,,. * ------,.--..;--;:.z"" """'S * "'"11 b*"'

.n~c:.r*~.:r c..... :...

~**-............. '-'_:. _1.:.i..... i.... e:n.. tcn.. rC!t_ s.. r.r... _.......

!,:-:'~=.i.t~::.:: !:.,*

~*:-;.:.~.~:iir*: t::r~*..::=!1 i:-s,:~: ti:n t:~~t r.:J ac.:ar~r.: ch.ln~:ts

~~~~ =~~*.**--~ i~ :~-

~~~:1 ~;::~.*:~:~ ~~ :~~en~ :~:~:~:;~ cc~:rct~

~~t::*::r* :~rf::~s ~,. t~~ ct~:r~:! er~:~ ~~t:~~~5 ~~~:c~~: t~ t~~ ~nd

~r::~::*.. ~Ji.

i~s::t:iens cf;*:~ ~c~:rc:~ s~lll t! ~~rfc~*!~ d~rin] the i:*r!? ;, c::-~Jir.-~r:; i.:.l~.'.*]! rat:.- ti?sts (r:f~:-~r:ce S;.;?::ific~tion 4.6.l.2)

• .. nil:_A ti:e c:cn:afrr*ent is at its r.:axir.:~1::1 test ~ressurc.

~.6. l.7.:?

~-k~.....?_1"':~ The str~ct!.lral int~~r-ity of th~ cont~ir~~!nt lint-r *

il~~t? ~*~Ji i.JJ ;.' ** *r::'!t:'lo::>d

urin~ *ti;e shu~~o:*ll'I for e3ch T~e :. con~?in~ent

'"'"' "",.,.,, *-.s* (.................. c:.....,*z,*..,.*1*on

• G 1 2) '"1 " **1's.... l ir... ""'C-1... "

-~**

• .~.,

L.

lo.

__....,I

'-'W~

e ti~

illllil

• * "'.: ***.,.. 1....,... j....,,. :v*r.......... p.,~rc*1* "h"ni-as in,... ~.., r~nc 0 or b*~-it ***.... _,...... ~-...

• ~

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u I"'~

b w !I""

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I l:1er.!~*":l'.>r-::"...!1

~-;r.::dat1on

• l

.6.1.7.1,

~:~!"~'"..r.n initi31 r~port of any a!lnomal ~egra~Jtion of t~!?

~c!1t::ir... ::::t s-.:-~1:~.;r:? :J~:~:t~r! dJrin:i t":!?

~~':l*te rcq~ired :~sts ind insp2c-u~ir.> s:::!ll =~ -::.e,;it!iir. ill i!a*p. after cc-~letfon of th~ s~r'leillilr.::e 1r~-.::ir:*:*1ts ~f *.*:1s ~:'l~cifi:.i~i~n llr.d J S~cicfol ~!?;.:>rt shall t:i? sub-

!*:it:~*j ;~:*s~J?lt t.> ~~~:ifi:Jti~n ~.9.2 \\lftn1~ 90 days aft~r c~~pletion.

I-... r. ',. '1.,... ~.** -**Jll,....,... :> "' "'"C'"~.. *ion of. t'.,D C"'"""'ition of the

• 1.1~ *""**-*I 1111:,. *. _...

~I*

........ --... U

\\,iC,:;t I t;J*

a.;1-.1

,*cr.:r~t-:-

(.::~;-,~1;,liy.:t t:ir.~::n.:l!!:h:rag~s}. lh~ jns~tc:tion,rocc-Jure

• tiii! t~~c1*:l:~:<?s c;1 cr<;c~in~. dllJ ti~e correc:ive actions taken..

~

Q en c..n U;>

en co I

ct-.\\1:::.s:ih:P.lt 3/4 t-llF llovc::iber 11

• 197 4 J-~---*

't **

di. 0

~.

I

i

• i I

I r- *.

I L

I I

I I I I I i

L r

t L I I I I

.I ' I I

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• 1 l '

j

• j

• c i

i J 1 I j I

j

-*'!911.,,... ___ _

Thi~ limitJtion er.sur~s :h!t th~ stn:ctural f~tegr;ty of the contain-rknt. ve~s~l \\-till L!' r:afo:ain;;-d cc*~ua~h to the orioinal desirin st;rndarrls for l't!.' Jifo of t!*e 'f.1~iiit::.

Str~c!~ral int~r;rity h r~riuir('d to ensure lii:tt :..'H? \\"l'sscl l!ilJ "li!:"'!S~.~"d t~;c ;'1tt;dr::u-, pres!:ure of {l:O) p:>i!l in the

v.. :it of a l!:C~. it-.

0 :-e!s:;rr-*1ent of con!ainr.ent tc11~c., 1 ift off *force, t;:~ vh*Ml.:;11d r:et.?JJ:ir*:rfcJi <'X!'1lr.atfon of tcmdcns1 iit:ChClrl'!~es t?nd liner,

-~nd t:'it> Tj-pe,~ leaklge t~s:s are ~~fffcbnt to de::ionstrate t:ifs Cilpabfl ity

• The S*Jrv~illdnc~ r:.-!;uir::~:.-nts for cfo,~n!>tratinq th~ ccnta.inrr:~nt's st,.,.;c~.:Jr-.?1 ht~~:-i~7 u~ fo c:--;:ilhr:ce ui:h the r~co:-r.:>!::datfons of

~~U:JlJt~rr ~~i~e 1.35 h!ns~rvicP S;r1~ili~nce of Ungro~ted i~ndons in f>rcstrrssd Cc:icr~t~ CcntJi:i~:nt S:ructures".*

I I

--~

.. &..:....o.:i **

-~

I

~

-* -__ __,......_:-_ ___. _____, __ ~...:......._ ___________._ ____ ::.:::::::::-:-~**::*:-:-~:-:-:--::-::~~=-=====*=-=*-===-==-==*~~

t..

i;~.*

Mr. Robert n. ?Unoi;uc Director Office of St~ndard5 Dcvclop~cnt Nuclc;,r Rc~ulatory Cornr.issicn

~hillips Buildinc 7920 ~orfolk Avenue Bethesda, HD 20014 9 REF.J Bechtel Povver Corporation-Engincr:rs-con:;1ruc1ors Fifty Bcnlc Slrcet San Francisco, California

.~*

. (JJ!Jj **

Meil llddtt.':SS:. P.O. llOll :l9G!i, San Francisco, CA 94119 Mny 6, 1976

Subject:

Regulatory Guide No. l.35, Janunry 1976, Revision 2 1In-Servicc Inspection of Ungrouted Tendons in Prcstrc~~~d Concrct~ Containment~' -

Comments

Dear Nr. 1-linogue:

'. ~ :.

We sub;::.it the follow:in!~ inforn!ltion on in-sc~rvice inspection of unr,routed tendons in prcscressed concr~tc contnin~cnt structures.

Your Regulatory Guide 1.35,

.:January 1976, Revision 2, st;itr.s det<lilcd surveillance requirements.. Uowcvcr, in

- Section D, "lmplcrner.::~tion", it states tlu1t tlic applicant may develop an acccpt.iblc:

.nlten:atiYc c:cthod.

We request your rP.vic::w of t11c

!ollm:in~ matcr:i:al on a ecncric-basis for all !t:turr::

COPt<:Jr.;~~~:-:t:;.

In the fnllo*,.:in:z \\,'r-'

ntrc~19tr;cl t.o cor::?}Y \\..'j th the intent of Rer,11!;.rory Gui clc 1.35 C!'1d, in ;;c!d:iticn, w:; r.m.*e CO:'l~idcY".::d' the k;'lC.O\\.'l*'.!dJ:;C WC h<l\\.'t! r,;dn.:-d in p:i!:t tE:nCon. inspt*c:tiCJ:'"!S *

.Attc;chcd for your infor.:i:it~.cn is a Suo:-.:r.::?ry of Tendon Surveillance Dnta for Bechtel de:;.it~n.::d cont:iim::cnts :i.n which W~ Suj-;">li cd tc:chnic.:Jl r,uici~!nCC during in-.sc:rvic.:

. _,,in.r.p~ctio:-i.

I.

TEN!JO:*: LIFT-OFF 'FORCE ACCE!'l',\\f~CE CRITERIA

t.

\\

TI1e containment~ arc oricinolly d~signc~ for an avcrncc preRtres~ force from nll t.:?ndons in a p:lrticul:ir rct;ion and our past expcri~ncc hn:; r.hm... -n varintion :in lift-o!f for a &roup of trm1ons._

Lift:~o!f Tl!&Jdinr,s must he corrected t 0 T'C'fl CCt t)~t! l*oncJ:i t] cin Of &JO £'&VC?r:1r,c tP.ndon, therefore, '1.*C h&JvL' nonn:Jl :i.:.'.,.,;

the.~ lift-off rc:~hlinr,~ to cnrrc:ct for initi.ul clm:ti*c lo~scs.:lnd ":tl!;o the initi:il.nctu.:il t"*mlon *snclH~.:Jgc value. sinc-c all t.c-n-dons c:mn1H be.incho1c!d :it thl!.<:>::1ct.so.ir:u: v.ilu<:.* After norm:"lli;:in~ *.H: h:.ivc dctcrmlnccl th.it Lhe-vnri,,tion in lift-off c.:.n*bc :ihout ~(2 co 5%).

This*

v&1ri:it~un j~; due Lo n:cnsurcmcnc error and other unknowns.

D'~c to this :

vari."Jt ion a::

th~ cun toii m::c!l t nc.:irr. end or lif c, about hnlf the m.:?oi!:urc:r-wn :.:-;

vill be above th<? rcl1ui red vnluc nncJ the: oth<?r h:ilf will be below, wl{ii:la :i ~

.an &Jcc1:pt.,hlc l"l'l1ditjun, providi.*d that rh~ :>Vt'r.:lr,u o( th..: sample is nbLJV"'

or cqu:1l to ll1** n*r1td n.*J V.:lluC'.

This :oiLuntion JS illu:.;Lr~L<<:d in tl11.: *

!ol lu1.*ini; fikc*t,*:..

- *-----*---****--*----*----------~-----..,...--------------"""'"'"**

......... ?

---

'-----~---------*----~.

~-*-,.. ~-*

. Bcc&r Power corr)oriiH~ff i~

ti

. ~

Hr. l\\obrrt U. Hit11'ii;ul'

~ ~-.

JlucJ car Rt'1;ul:it"'ry Cor:;:ni!l~ion Uay 6, 1976 J*.:itr. 2 8.0 ~

Expected prc~trcss (S

Spccific mcllsurements x

.K t:

---

~ >:

x t

~x x

~

j x

~--

-J

7.0 :1_,..'\\

x x

i:

. x --....__

~

~ ~

}linimum required prestress

~

0:

I I

I l

5 10 20

~o Time a!t~r initial ten~ioni~s (years) lnstc:.d of r.c~quir:i.ng thnt all vnluc~s must be abo,*c the minim:..:r:i rc*qui r.:~cl v:iluc: 1 we con!;5tlcr Lht> follc\\..*in2 a r.iorc: renlistic acccpt~ncl'.' criteria.

(1)

All Jift-o!f v.*l~c!; n:iir.t be cotT~ctc:t1 fc.,r in:i.ti.::il ini>talJ:trion

. (2)

(3) condi t io:1s (::c tll::.l

.:;.nd;:rr~1f,C f c~*cc end cl.::ir.tic lo~!:l'S du1~:.n!! ini t.:i ::.J po~t-tc:1r,:i.c-0 :1it~E; ant! ~:1y ot lic;r si~nific:;mt c! fcct!i) so th:it the V.'.lluc is indic~tive of th~ av~r~~c level cf prcstre~~

• The avcl*:11~e of nll corrcctt:d lift-of!s shal.1 be cqu:il to or ubovc the miniffiurn required prc~trens.

t Lift-off :-:h.111 be obr:lincd* on ac~jaccnt tC!ndons for any tendon which is below 90~~ or the r.ii11imur.1 required prestress.

II.

DET:C~srm:rnG OF TENDO!*iS Tl1e R~~u]nt~ry Gui<l~ n~parcntly r~quirc5 ~hat the tendon~ be d~t~nHJoncd durin~ LhL! sur\\*c.ill.:mc_!! to check wire or str:uuh.c:ont:inui ty.

Since the RcJ!ul&Jtory C:uitlc only r.:.*c1uirc;; wlrc or stnmcl rcmov.il from one tendon froni each cr"up durini; cnch lnripc~ction. then only a sinclc wire or scr01ml tcndOR ~ill be dclcn~ioncd from ~ach t;roup ~C O&lCh in~pcction for purp~~~S o! str:md or wire rc.:inv:il ;ind continuity chcckin&*

Our pnst in::pl?ctil~uh have only dct~ct~d :lhout O.lZ lci::s of wire continuity out of :i !:*m;llc!*:;j:-:c of lJ,)00 \\.drr.:;.

Thcrr?forc-. th.:T'C *lppc:.an> to be in!iigni!ic::Jnt :iu**~L~rv.icc

\\lire brc!;al~;IJ~~ :inc! s)ncc.! tht: hrc~;1k:ict! would occur,-~1rly in lir<~

(.:.,i:icc*!;trc.*~::

dccrc.:rnc:; with tiP1l*). it i:* our conclur.inn tJwt continuity 111*1*1! l1ur.

hi~

chc-c:kNl cm :ill ll'lllfc,n:> clul" in;~ :in!>J'<-'Ct ion.

1-"oT' tr~ncJun:o which ;111; "'"'t 111*-

tcn:;imH'J, it i& only nl*L*c:~*:;oir)' to obr.:1in li!t-o!! r~adini;:; ninu~ '-'lont~:Hion 111cm*urL:i11cnt:; do not: :JJ<.I *my nc*cc:o.r.:iry inforu.oition.

.Gccl 9 Pov1erCorporall(;(ii~}!~~-

. : <<~),:Z~f..

• Mr. Rohe rt ll. Minor;11P.

~uclcDr R~Eulntory Cot~is!':ion JI..:&)' 6 I 197 (,

~ '

J*.,i;c 3 III.

/inotl1cr :iltcrn;Jtj.vc th..-1t ~c cc:n~:"irlc:r :~ccr.ptnblr. is the use or lo3d mc;.isurinr: dcvicc:s ::uch a!> ln<.id cells, and, in this c:rnc, the sat:iplc is*,

prr:dctc:rillii:cd. -

INTERrF.ETATIC!~ Or SPECIFIC F..EG'JJ..J.TORY GUIDE REQUIR~HENTS

• We interpret P.cr;ul3tory Position Section 6(3), "procedure to u.""lcO\\fcr possible voids in grease in the truI!:pct *** " to.1T1ctm th3t the volume of grease removed prior to detensionin£ and reinstalled after rctcnsioninz be csti~ated to assu~e that the rccoved volume is replaced.

I Section n niZC:\\l!;!)~On states It *** To the fullc!:t e::-:tt!nt prnctic.::il it shou] d also cover the ducts thrit cont:iin tl1c tendons."

We propc1!::r. t:o implcr.icnt this requ:i;r.l.!~.cnt by r:~rfor~i.ng :l v:i.:::u~l i."'l!;p~c:t:io-r: or the c:ont;;,imr.cnt striictm:-e to cfoter-"':inc* c:-:cr~::s.:!.vc gn~."'.l~C! (t.en.:inn duct filJ er) l caku~e fro=i the tcn~on t1uct!i and le reco;;..:z.**:nd cor:r:ect::i.vc: actio.n if requirer!

• l'lc~!::c not~fy us r<>r..::cdinc the.:iccc:pt'~.;.bilit:y of t.he pro?c5cd tendo:i 1ift-off force accept:mc:? critt!rL:i and our. int.::rprctaticn of Spt!cif:i.c Rc:;ul:1tc:*!"Y Gu:i cfo rc:quirc-mcnt~.

~hould our pro~o~~d ncc~ptnnc~ critcrin nnd intcrprctnt~cns*be not fully nc:1;cpt;::hJe to )"Nl, plc::~c.ac!-,*5.sc us :is t:o w1.ich p.::rt!> arc ;;cccpt;rblc.

BLL/BHP I Sm;)

• Att.cl1. (1)

Very truly yc~rs,

.... ~~/. /Ju*

(£),,t.,,L--~~,,,, r;::;.t:\\;t:tK Durton L. Le:>;

Mlm:tECr of Enr:i ne t~r:;.n e

• t

• . r" R

... (..... *

~1 4/06/7G...

. \\

sm*:r~... or TJ:r:mm Sl!!:V l.l l.T.AliCE DAT.t..

The follo~::in~; :;ur..:~nt"y or tendon !iU.TVC"illancf! d:it::i ;irr. bnr.cd on tendon :;urvc:lll::nccr.

performed hntwl~~n 197) ;1:-id 197(;.

Durin1; th:it time, J\\cchtC'l provill~d technical 1:uidatncc for tcnclon ~ur*.:rill~11rl~ work <.*n PnH.:~.'?di:~; Nucl.t:ar l'uwer l'lunt; Point Bc:ich Nuclcnr 1'01..*cr l'lilnt, lh:its l ;ind* 2: Turl:r.y Point Nuclcur. l'owcr Pl:int, Units 3 Drui 4; and Arknn!laz Nuclc~r One, Unit l.

l.

SURVEILLJJ*:cE l'HOCEDlmE 1.1 1.2 1.3 1.4 1.5

• 1.6.

1.7 Inspection *of An'C:l~or J.ssemblies Visual and Laboratory Examihation of Sheathinc Filler Measuring Lift-Of£ Force Detensioning Tendotw and Chc;ckin;; Wire Conti11uity Wire Remov'11, E>:atai";"lDtion nnd Test in~

Rctensi~ning of Tc~dons Evaluation o! Test and Inspect.ion Results

2.

SURVEILLANCE S/~H!'LE SIZE Dcscrir:tion (1) lhirn~,~r cf tc:1dons c!e~cns1.oncd du-r:i.ng l-yc:ir S\\.1rvclJ Janee 79 (2)

Nu~hcr of ter.C.o.ns cct:c*n;.joned du:-inc 3-yca.r survcillnncc 56 (3). lhi~hcr of tcnc!ons dcrcnnioncd during 5-yc:ar surveill~ncc

• 21

(/1)

Nui;il.'<:r of li!t.-o ff de t c rm in;; t ion:; duririg 1-yc:<ir su rvr.:ill.1ncc (5)

Nu~b~r of lift-off dctcr~inntion~ durin~ 3-ycnr survcill;mce (6)

(7)

( 13)

(9)

(10)

(11)

(12)

Nli::it~r of lift--o!"f rl:: t~n.--:in:itiom; durin~ 5-yc;ir su:-vci.lJ.:mc ~

Volunc of shcathinr, filler vi.!"=11.'.llly c:>:nmincd Ccnllom:)

Nu::-.bcr of ).aborc::t cry r cst~J shc:l t h:in~ f ilJ.er samples

'Nur.:ber of "ires inclividu:Jll)* ch.:-ckcd for co:-t:.inuit)

Nuclier of buttonhcnds checked for size an~ splits Uuchcr of tendon ~nd-nnchnr~c~s i~~pcctcd

?Jumhcr of continuous wires removed for cxc:imin3tion and tr.sting

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SURVEII.LANCE lmSUJ.TS 3.1 Tendon Lift-O!f F.nrcc

3.1.1 One-Year

79 tcnJons dct~n~toncd

.t!. adtlition.al. tendon:; lift-c,rr only 148 104 37 3,800 178 13,300 26;600 312 123 93 tcmlon:;.survl"'Y*!~: i..::.-:.*l!L"l' J c>:!lccrcJ lift-off force by ;11\\

nv~racc or 2.472 A-1

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56 tc:111k*11:; tit* t r*n:. j. *** i J_Q Dcl1l i l i c111ill tc*ah:.**

• lift-off only 6&

t*c111lc*11:~ :;11rvl'yr*d

..!~:ccL*c!r*il t.*>:p1!Ctcd avcr:ii;c of :,

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~v,1r,;;1@f '::'.'.~~

u ft-off fore* 'by,d~l~j};~

22 tendon~ dc*ten:;ioncd The :.ivcr;!;~~ l ifr-uf f force wos 0.13% be lo\\J the expr.ct*cd lift-o!f

• foi*cr., lrnL \\."t:ll,.,}JovC' t11~ rctJuirc:d min:ir~um ef fc*1.:tivr. dc!:i~n pr.<.-~trc:;!..

3.2 Tendon \\.lire-Inspecticm

. 3.2.1 3.2.2 3.2.3 3.2.4 Continui.ty -

.17. discontinuou~

Duttonheads - 1.4% off-size or s~lit*

Corrosion -

minor Pl1ysical properties -

unchan&cd

3. 3 End Anchor~zc lnspcc ti on J~o flaws or cracks; sornc minor corrosion.

3. 4 Shea tMnz Filler I:x;iwination So~~ srr.all air poc~ct~.

3.4.l 3.'4.2 178 samples niiairnurn of chlorides, nit:::-ates, and. su1f:i.de::s.

Tendon:; H'.Jvr: not

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l*Jirc i.rC';;1::-;:\\'!

h::!~ i:ot CC".:lffT.t'c.!.**

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• l,. l 4.2 4.3 4.4 4.5 4.6 4.7 4.6 Fhy.::ic:i l p1*0~* c:T t f l*S of ti* m!...,,~ t.*:i re.~

~r.c.> rr*m::! ini. ~i !?S!3Cn ti;1 ll y con5 tCl'l". t.

Slir::1t?d.:1[; f.ijJcr ha~ r:::>t.

unc~cr~on:.: drtcrior.it:ic.)n.

Corrc-c*i.o:-. r:--.t:: 01* wirer, :!!:d cl:':::i;r,ncr.ts h<:5 been in::icn:if:i.r:.:mc.*

No strc~s cor~o6ion or hy~roccn c~brirtlcmcnt h~s be~n observed.

Ti::u,lons.:!r:d t'nd <?ncl:orati::s h.:1ve :;l:own no si~ns of proe:-cssi vc de tc~r:i ora t il,n

• t Minor split; ~~re :icc~pr~~lc durinc initial inst~ll~tion.

Th<' <!Vidc*ncc in1Uc."lles th:1t the d:iuconllnuou~ Yirc:;. per Sec. 3. 2.1 (0.1%) :>.re the rl~Hult Of V.il'C bn!01\\:&12:c \\.'hich cu:curn*d durin;; the imaalJ~tion of lhl! rust-l't'!l!'dotiin& !>)'!':lt*m. 1'hc 0.1! lor.r.*or prc::;trc.:!.is (c.ih;cnntinuou!i virc:;.) ir. well twlow the 2.0:~ lo~:!': of prcstn~S,!; ;illowcrl b)' ACI-71, Scctio11 18.19.3.

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o' JUL 2 7 1976 I

1 Hr. Burton*L. Lex Manager of Engineering Bechtc 1 Power_ Corilora ti on P.O. Box 3965 San Francisco, Californiu*94119

Subject:

Your Coir~11ents on Revision 2 of Regulatory Guide 1.35, dated May 6, 1975 Dea*r r.~r*. lex:

We have revieww! your comments and suggestions and the following are clarificutions of the guide relating to your comments:

I.

This corrm1ent ruises various questions regarding the

_prestressing OReration and methods of keeping track of the initial prestre~sing force, sequence of prcstressing of tendons and their effects on loss of prestress due to elastic shortening, method of computing the time

• ~ependent losses and determining the predicted forces.

It is the intent of the guide that the applicants construct a tolerance band bounded by two concurrent prestressing force curves against time, i.e. one using anticipated small amount of time-dependent losses (upper bound) ahd one usin~

large amount of time-dependent losses (lower bound) for each tendon using the ac_tual initial prestressing force measured by accurately calibruted pressure gages (or load cells) a.pd checked by elongation.

Depending upon the sequence of prcstressing,. the ~nticipated elastic.

shortening loss c~n be allowed for*as a~non-time-depcndcnt loss. If other tendons in a subgroup are expected to have

.the same time dependent characteristics (giving d~e

• considcrntion to the effect of age of concrete at prestressing), with variation only in the actual initial prestrcssing force and in the loss due' to elastic shortcni_ng,

. the same tol era nee band may be used with some means of tracking the variation.

When a tendon iSr,randomly selci:t'cd during an :i:~::1c(tion from these tendons, its lift-off value should he chPcke~ to see* if it is withtn the predicted

.-. tol erancc band i or that tendon.

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I Mr. Burton t: ilcx.

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• . Ju-1 1976 II.

The practice indic~led in your letter is not acceptable as it mixes up the initially dctcrminJblc parameters (i.e. initinl anchorage force, loss due to elastic shortening) with the parameters which cnn not be determined so accurately and are ti~c-dcp~ndcnt. Such a practice reduces the effectiveness of the in~pcction pro~rnm. However, the criteria that you have suggc~tcd m(1~* be modified r.s fo1lo\\*1s:

(1)

(2)

(3)

All curve~ of predicted tol~rancc bands should be con:""ected for initial i"nstallation conditions such as actual anchorogc force and loss due to elastic shortening.

All lift-off values should be within the corrected tolerance b~nds of respective tendons.

Lift-off shall b

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.r.f e 0 1.a 1 ne~1 0:1 ouJu\\.Cll I. 1.11u01;S I ul 011.)'

1.t:11~1an 11 i.-0 I value which is outside tlie limits predicted for the time ~f the test.

The average of the lift-off values from all ten~on: in a particular region !:ihil 11 be equa 1 to or above the

.mini~um required prcstrcss.

We recocnizc the cost and inconvenience invol~ed in detens i or. i ng the te;1dons to verify the wire or strand disc;ontir.uity.

Since the conclusion of insignificant inservicc wire brea~~qc is based bn what still must be ccnsidcrc-d as lir.1itec(e,.:pericncr., \\'lire or strand discontinu*ity should st*ill be checked by detcr.sior.ing the \\*:hole tendon during each lift-off tc:!:;L lf met!ns other than d!;tensioning are availc:iblc to check discontinuity, \\*1e \\*muld be interested in reviewing them.

Only a single wire or strand frcim one tendon of each type need be removed for testing and examination over the entire length.

~

As pointed o~t in your C0:71rncnt, the randomness of the sampling will be lost if load cells are s~bstitutcd for the

• lift-off testing. Therefore, the use of load cells m~y

. only be practical for the one tendon from each group wl1ich may be kept uncha~gcd after the initial s.~lection.

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• Mr~ Burton JUL 2 7 1976 III. The intent of this recor.r~i:?ndntion was to nrnke sure that the variations in temperature during the jnspcction interval has not created voids in the tendon duct thus exposing the tendon to the possib1e influence of the outside environment.

To verify the full cove:rt;oe of anchorugc components, the procedure indic~tcd in your letter is adequate.

However, after dC::!tcn~ioning it will be prudent also to check tlrnt the tendon duct is filled with grc~se from bearing plate to bearing plate.

The procedure of performing the visual examination of the containment structure fer the purpose of determining the 9rease-lcakcge fro~ the tendon duct is acceptable.

Because of the expected variations in the ~aterials of prestrcssing systc:ms, cons true-:.. ion proccdt.-rcs, site dcper:d:2nt factors, and method of implcrr,::;ntin9 the guide rcccmmendations, we have not yet determined to \\'/hat extent \\*Je shculd accept the statistics btlsed on lum?ed data fro~ various groups of tendons and various containr:::;nts.

Hm:eve:r, \\*112 appn:c*iate your having sent your surr.;;;:?ry of tendon surveil l.:.1;ce data.

cc: Public Document Room Sincerely, 1;1,lf tr<O.., -.,,,..,;;

/ 1/~ l/::-~n-*n..:::*11i.c...,jl-,,

M. Kehncmuyi, Assis~~nt Director for General Engineering Standards Division of Engineering Standards Offic~ of Standards Development t

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