ML20076N271
| ML20076N271 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 07/15/1983 |
| From: | Corley W CONSTRUCTION TECHNOLOGY LABORATORIES, INC., CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | |
| Shared Package | |
| ML20076N260 | List: |
| References | |
| ISSUANCES-OL, ISSUANCES-OM, NUDOCS 8307210266 | |
| Download: ML20076N271 (6) | |
Text
{{#Wiki_filter:. .9 Jttly 15, 1983 State of Illinois SS. County of Cook UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD 'In the Matter of ) ) Docket Nos. 50-329-OM CONSUMERS POWER COMPANY ) 50-330-OM ) 50-329-OL (Midland Plant, Units 1 ) 50-330-OL and 2) ) Affidavit of Dr. W. G. Corley My name is Dr. W. G. Corley. I.have previously been a witness in this proceeding and my professional qualifications are in the record. I swear that the state-ments made in the attached Affidavit are true and correct. k by W. G. Coy. ley. Signed and Sworn before me t'.is 8go . day of July, 1983, Wucu Notary PUblic ily Commission Expires January 14.1081 F h O .PDR, w
~. .c AFFIDAVIT ~* - ~ OF DR.-W. GENE CORLEY .547 name is William Gene Corley. I am Director, Engineering Development Division, Construction Technology Laboratories, a Division of the Portland Cement Association. My qualifications were entered into the record at a hearinq in December 1981. At the request of Consumers Power Company, I visited the Midland Nuclear Power Plant on February 15, 1983 and' inspected reported. cracking visible in Rooms 110 and 116 near intersections of butresses and the slabs in the contain-ments. A copy of my report on this inspection is attached. a-In this affidavit I would like to_ supplement information supplied in the report. h According.to information given to me by represen-tatives of Consumers Power Company and by representatives of Bechtel, both containments had exterior-surface. coatings applied prior to-the time they were prestressed. Containment [ construction was completed above'the 600 ft.---levei, an-elevation higher than the' highest visible crack inspected on s EFebruary 15,71983,1by.early 1975. Coatings were applied to .tne' structures inLJune of 1977. Prestressing: began-in late-1979 and'was. completed.by early 1981. -Dewateringlof-the ' area-'around:the'containmentsiwas first donetthe latter>part- 'of 1979. h 9 "h 4 j,
In my report of' March 1983 (revised April 1983) I noted that coating material was visible in the cracks at the locations I inspected with a 50 power magnifier. I concluded that the' cracks were present prior to the time coatings were applied. As indicated by the construction sequence, the cracks observed on February 15, 1983 must have been present before application of coatings was completed in June 1977. Approximately four years passed between construc-tion of the containments to the 600 ft level and application of prestressing. In general, this time period would be 4 beneficial in that it would reduce the total amount of creep and shrinkage that would occur after prestressing was applied. Reduced creep and shrinkage would mean less loss of com-pressive stress in the concrete after prestress was applied. However, shrinkage that occurred after construction but-before application of prestressing would also add to the-likelihood of surface cracks occurring in the structures. It is not unusual to find cracks in prestressed structures, particularly~if prestressing is done a long time after the concrete has been placed. In'the containment structures at the Midland Plant,. restraint conditions-at'the' intersection between the base and the' walls would be a - place that - some cracking might ~ be-expected. According to Bechtel calculations provided to ape by Dr. Shunmugavel stress caused by dead load and pre-stress force would induce tension at the locations where
O cracks were observed. In combination with shrinkage and temperature stresses, these tensile forces might be expected to be high enough to cause cracking. Based on this infor - mation, it is reasonable to expect that cracks would be found in the locations inspected. Prior to the February 15, 1983 inspection I made of cracking visible in rooms 110 and 116, I had seen time versus settlement records for the containments. !!y inspec-tions of these records disclosed that total settlements were relatively small. In addition, total differential movements measured around the perimeter of the containments were small. Because of the high rigidity of the containments, little differential movement would be expected. My visual inspection of the cracks and review of Sheets 1 and 2 of " Field Engineers Report Form CC-183," dated 12-17-82 which is included in my report entitled " Visual Inspection of Cracks in Containments Near Anchorages in Rooms 110 and 116," disclosed that the pattern of crack-ing did not support the possibility that cracks were caused by settlement of the. structure. The observation that some cracks were approximately horizontal, some approximately vertical, and others were inclined, suggests that the cause was'most likely to be restrained volume changes. For the reasons cited in this paragraph and the preceding paragraph, the possibility of settlement causing the observed cracks 'was not addressed in my report. r.
Subsequent to inspecting cracks in the containments, information was supplied to me that indicated estimated con-tainment settlement caused by dewatering was 0.8 in. This estimate is given in FSAR Subsection 2.5.4.10.3.1.5. As of July, 1983, settlement of the containments has been less than 0.6 in. Based on this information, it is my opinion that the cracks cannot be attributed to differential settle-ment. The observation that coating material is in the cracks also precludes the likelihood that any cracking was caused by the dewatering. The coating was applied in June 1977 while the dewatering started in late 1979. Consequently, the coating could not have entered any crack that occurred after dewatering started. I have reviewed the crack maps recorded by Wiss, Janey, Elstner & Associates in July 1983 in Drawing No. 7220-C198-2857-1 (11 pages) and referred to in Dr. Shunmugavel's affidavit. They do not change my opinion concerning the cause of such cracks. Based on visual inspection of reported cracking in rooms 110 and 116 on February 15, 1983 and on subsequent review of construction schedules, settlement measurements, and other documents, it is my. opinion that the cracks do not affect safety of the containments. In massive structures such as the containments, it is common to have cracks caused by volume changes in the concrete. Cracks inspected are not wide enough to indicate that any structural damage has been done. Consequently, the cracks do not need to be repaired. L.m
e l. As recommended in my report entitled " Visual Inspection of Cracks in Containments Near Anchorages in Rooms 110 and 116," cracks should be monitored by qualified engineers during the pressure testing of Unit 1 and Unit 2. Monitoring of these cracks will give additional assurance of the safety of both units. I have reviewed the Applicant's commitment to containment crack monitoring to be performed in addition to the SIT, as described in Dr. Shunmugavel's affidavit, and I believe it is adequate. + + i i v. - - _ - - _ _ = = _}}