ML20128B687
| ML20128B687 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 06/14/1985 |
| From: | Van Brunt E ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR |
| To: | Kirsch D NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V) |
| References | |
| REF-PT21-85-298-000 ANPP-32832-TDS, DER-85-12, PT21-85-298, PT21-85-298-000, NUDOCS 8507030318 | |
| Download: ML20128B687 (7) | |
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RECEIVED HRC Arizona Nuclear Power Project P o. BOX 52014 e PHOENIX, ARIZONA 85072-2034 3i REGION yIM June 14, 1985 ANPP-32832-TDS/PJC U. S. Nuclear Regulatory Commission Region V 1450 Maria Lane - Suite 210 Walnut Creek, CA 94596-5368 Attention:
Mr. D. F. Kirsch, Acting Director Division of Reactor Safety and Projects
Subject:
Final Report - DER 85-12 A 50.55(e) Evaluation Relating to Cracking in the Auxiliary Building Walls File: 85-019-026; D.4.33.2
Reference:
A) Telephone Conversation between R. C. Sorensen and T. R. Bradish on April 1, 1985 B) ANPP-32451, dated April 19, 1985 (Interim Report)
Dear Sir:
Attached is our final written report of the Deficiency referenced above, which has been determined to be not reportable under the requirements of 10CFR 50.55(e) and 10CFR 21.
Very truly yours,
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E. E. Van Brunt, Jr.
Executive Vice President Project Director EEVB/PJC/j b Attachment cc: See Page Two 8507030318 850614 PDR ADOCK 05000528 S
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ANPP-32832-TDS/PJC Mr. D. F. Kirsch DER 85-12 Page Two-cc:
Richard DeYoung, Director Office of Inspection and Enforcement U. S. Nuclear Regulatory Commission Washington, D. C.
20555 D. B. Karner W. E. Ide D. B. Fasnacht A. C. Rogers L. A. Souza D.~E. Fowler T. D. Shriver C. N. Russo B. S. Kaplan J. R. Bynum J. M. Allen D. Canady A. C. Gehr W. J. Stubblefield W. G. Bingham R. L. Patterson R. W. Welcher H. D. Foster D. R. Hawkinson R. P. Zimmerman M. L. Clyde
-B..T. Parker-8e T. J. Bloom D. N. Stover-J. D. Houchen J. E. Kirby Records Center Institute of Nuclear Power Operations 1100 Circle 75 Parkway, Suite 1500 Atlanta, CA 30339
L FINAL REPORT - DER 85-12 DEFICIENCY EVALUATION 50.55(e)
ARIZONA NUCLEAR POWER PROJECT (ANPP)
PVNGS UNITS 1, 2, 3 I.
Description of Deficiency On February 18, 1985, Bechtel Construction personnel observed several cracks in the Unit 2 Auxiliary Building interior walls between elevation 70'-0" and 88'-0".
An inspection was per-formed during the week _of March 11, 1985, and some of the cracks were measured to be as large as 0.050 inches. As a result of these findings, NCR CA-5071 was initiated on March 15, 1985, to document the noted conditions. All cracking exists in the area included in pour _ number 2A047 which was made on November 17, 1978.
Evaluation All cracking documented in NCR CA-5071 occurred in walls which were placed as part of concrete pour number 2A047 (see figure 1).
Pour number 2A047 utilized concrete mix design C-Z-K-405-Y (4000 psi at 28 days, 1-1/1/2" MSA, without pozzolan). According to batch plant records, pour number 2A047 consisted of 261 cubic yards of concrete mix C-Z-K-405-Y and 9 cubic yards of starter mix (grout) -for " slicking" the pump lines.
During the inspection by Bechtel Engineering, all of the above identified walls were crack mapped and excessive crack widths were measured using a magnifying comparator. Crack widths are generally considered excessive when they are greater than 0.015 inches. All crack mapping and crack width data are' included in the documentation for NCR CA-5071. The walls which demonstarated the most significant cracking are on column line A9 between AB and AC; on column line A7 between AB and AC; and on column line AB between A8 and A9.
The maximum crack width was 0.050 inches (A9 between AB and AC).
Several investigative steps were taken in order to collect data and are listed below:
1.
Eighteen 1 and 2-inch diameter core drills were taken at various locations to determine the depth of cracking and quality of concrete. Core samples taken revealed that cracking' extended through the full wall thickness in most cases where significant surface cracking was noted. Core samples also revealed a significant lack of coarse aggregate
Page.2 in the' lower 3 to 4 feet in walls AB between A8 and A9, and in wall A9 between AB and AC.
These were the two areas which experienced the most significant cracking.
- 2..
Floor coating was removed adjacent to walls AB and A9 in areas where the most significant wall cracking occurred in an effort to reveal any signs of structural distress.
No floor cracking was noted in these areas.
3.
Compressive strength tests were taken on five of the eighteen core samples taken..All core samples tested exceeded the minimum strength requirement for Class C-2 as defined in Specification 13-CM-101.
(See NCR CA-5071 for lab test documentation.)
-4.
Crack width growth monitoring was implemented at selected locations. No significant growth was noted after a 30-day monitoring period.
(See NCR CA-5071 for documentation of crack growth readings.)
5.
Jm inspection was performed of walls and slabs in the upper elevations of the Unit 2 Auxiliary Building in a further effort to. find any inication of overali structural distress.
No other significant cracking was discovered during this inspection.. In addition, an inspection was performed in Units 1 and 3 of the Auxiliary Building < walls between elevacions 70 and 88 to determine if similar cracking exists.
Although some sLailar cracks existed in both Units 1 and 3, crack widths observed were in the range of 0.010 to 0.015 inches, and are typically attributable to drying and/or thermal. shrinkage.
6.
All backfill records for this portion of the Unit 2 Auxiliary-Building were reviewed by a Bechtel Soils Engineer to deter-mine if all backfilling and compaction was performed in accordance with all project specification requirements, and if any peculiar occurrence took place during backfilling which might have. created ^a potential for building settle-ment. The results of this review indicated that nothing unusual occurred during backfilling, and that all backfilling and compaction operations were completed in strict accordance with all project specification requirements.
7.
All building settlement data was reviewed to determine if actual settlement could have in any way created a condition of. structural distress.
Results of this review failed to
-indicate anything which could have contributed to structural cracking in the subject walls.
Page 3 As a result of all the investigations performed, it can be concluded that the cracks documented in NCR CA-5071 are not of a structural nature and were not caused by any structural overload condition.
-The cracks are instead due to drying, shrinkage and thermal move-ment. Shrinkage and thermal cracks generally penetrate the full section thickness, as demonstrated by the Auxiliary Building cracks, whenever the tensile stress, induced by the change in concrete volumes, exceeds the tensile stress of concrete. Pour number 2A047 appears to have concentrated amounts of starter mix (grout) in some locations, particularly in the wall along column line AB.
Starter mixes have a greater tendency for higher drying shrinkage and greater cracking potential. The concen-tration of starter mix in the areas where the cracks occurred is concluded to be the root cause for this condition. Prior to May, 1981, there was no formal criteria for the amount of starter mix permitted at a given concrete placement, but rather good workmanship principles were relied upon to limit the amount of starter mix used.
II.
Analysis of Safety Implications Since the cracking has been determined to have been caused by drying shrinkage and is: not attributable to any structural overload condition, it is concluded that the existence of these cracks does not have any adverse effect on the structural in-tegrity of the walls and will not prevent the walls from ade-quately carrying the required loads. This condition is eval-uated as not reportable under the requirements of 10CFR50.55(e) or 10CFR Part 21, since if this condition were to remain uncor-rected, it would not represent a significant safety condition or substantial safety hazard.
III. Corrective Action The cracks noted in this condition have been determined to have no significant adverse effect on the structual integrity of the walls; however, as a mater of good workmanship, cracks 0.015 inches or greater in width shall be repaired by epoxy injection, in accordance with the final disposition of NRC CA-5071.
In order to control the amount of grout used at the beginning of l
any concrete placement, Specification 13-CM-365 was revised by SCN No. 2673 in May, 1981, to limit the depth of grout to 3 inches maximum at any location when placing grout at a construc-tion joint. All major concrete placements have been completed and the only remaining concrete work is pour-backs at block-outs and repair work; therefore, no additional action is required.
Additionally, to insure that these items will be continually identified in the future, Construction Field Engineering and
- r Page 4 Resident Engineering will be directed (via an Interoffice Memorandum) to continually monitor, during normal' tours and walkdowns of the plant, for abnormal or suspicious cracks which may appear and require evaluation.
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