View source for W3P86-1639, Forwards, Evaluation of Findings of Basemat Crack Insp of May/June 1986. Basemat Design & Performance Still Acceptable During All Postulated Loadings Including SSE Loads

{{Adams
| number = ML20211N385
| issue date = 07/01/1986
| title = Forwards, Evaluation of Findings of Basemat Crack Insp of May/June 1986. Basemat Design & Performance Still Acceptable During All Postulated Loadings Including SSE Loads
| author name = Cook K
| author affiliation = LOUISIANA POWER &amp; LIGHT CO.
| addressee name = Knighton G
| addressee affiliation = NRC OFFICE OF NUCLEAR REACTOR REGULATION (NRR)
| docket = 05000382
| license number = 
| contact person = 
| document report number = W3P86-1639, NUDOCS 8607030088
| package number = ML20211N390
| document type = CORRESPONDENCE-LETTERS, INCOMING CORRESPONDENCE, UTILITY TO NRC
| page count = 4
}}

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LOUISIANA           ,4,Oemmo~Oeerneer   .   ,,O noxeOOe P O W E R & L 1 G H T! NEW OALEANS LOUISIANA 70174-6000     9 (504) 3t-it2 .2345 UTILITIES SYSTEM July 1, 1986 W3P86-1639 A4.05 QA Mr. George W. Knighton, Director PWR Project Directorate No. 7 Division of PWR Licensing-B Office of Nuclear Regulatory Commission Washington, D. C. 10555

==SUBJECT:==
Waterford 3 SES Docket No. 50-382 Special Report on Baseiaat Monitoring Prograi. Results

==REFERENCES:==
(1) Letter, W3P85-0464, K. W. Cook to G. W. Knighton, dated February 25, 1985 (2) Letter, W3P86-0111, K. W. Cook to G. W. Knighton, dated January 20, 1986 (3) Operating License NPF-38, License Condition 17 (4) Harstead Engineering Associates (HEA), Report No.
8304-1, dated September 19, 1983 (5) Harstead Engineering Associates (HEA), Trip Report No. 6, dated September 6, 1983

==Dear Sir:==

As part of the Waterford 3 Basemat Monitoring Program (References 1, 2 and 3), a scheduled basemat crack inspection was conducted on May 30-June 3, 1986. Preliminary results of the inspection were reported orally to the NRC on June 2. The enclosed report, " Evaluation of Findings of Basemat Crack Inspection of May/ June 1986," dated June 30, 1986, documents and evaluates the results of the inspection. The report concludes that the inspection results do not affect the previous determinations of the cause of the cracking and the structural insignificance of the cracking.
The scheduled inspection identified hairline cracks which had not been recorded on the original basemat crack maps developed from the basemat crack inspection in 1983, as reported in References 4 and 5. The physical appearance, size, location, and orientation of the previously unmapped cracks indicate that they are previously existing members of the same family of cracks which had been identified in 1983 and formed during the construction of the basemat. This conclusion is supported by basemat settlement data and groundwater monitoring data which indicate that no new loading mechanisms have occurred since the 1983 mapping.
8607030088 860701 ADOCK 05000382 1
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W3P86-1639 Page 2 The report also includes a comparison of the observed crack patterns with the results of a construction sequence analysis which was developed as one of the confirmatory analyses requested by the NRC. The construction sequence analysis results support the previous determination that the entire family of cracks was most likely formed during construction of the basemat.
The inspection revealed no deterioration in the previously mapped cracka.
Because the previously unmapped cracks are similar in appearance, location, and orientation to the originally mapped bairl,ine crackx, their presence bas no effect on the previous determinations that the basemat tracking is not structurally significant and has no detrimental ef fect on the 5.tructural integrity of the basemat.
Most of the previously unmapped cracks are within areas of the basemat which were not mapped in 1983 because they were located in areas which            '
were considered inaccessible at the stage of construction existing at that time. The few remaining previously un. napped cracks which are in previously inspected areas, can generally be discribed as superficial, and it is concluded that they were not mapped previously since, being extremely fine, they were not detected due to concrete surface conditions at the time of inspection or were considered superficial and did not warrant placement on the crack map. This conclusion is supported by the recent experience of LP&L and Ebasco personnel in attempting to assure all cracks have been located. Some of the cracks described as superficial were only detected by one of two inspection teams. Careful examination of these cracks shows that it was not unreasonable for them to have escaped inclusion in the original mapping.
The 1983 mapping of the basemat was performed on nearly all of the basemat area, with the exception of those areas which were considered inaccessible due to structures or equipment placement, surface conditions (e.g. water, dirt, construction debris), temporary storage, construction activities or physical barriers (Reference 5). As is borne out by the characteristics of the previously unmapped cracks, the 1983 mapping effort provided data which allowed the establishment of the pattern and characteristics of the cracking and to allow a thorough evaluation of their structural significance.
To more clearly define the basis for the ongoing conduct of the Basemat Q
Monitoring Program and its relationship to the original crack mapping effort, LP&L initiated several investigations which will assist in normalizing the technical basis for ongoing evaluations, and avoiding possible inconsistencies in the future between baseline and subsequent inspections. These include the following actions:
o    Definition of the extent of the original crack mapping o    Definition of the currently inaccessible areas of the basemat o    Establishment of revised baseline crack map o    Initiation of a photographic survey of the basemat cracks To obtain as accurate a definition as possible of the extent of the original crack mapping effort, LP&L arranged for the original participants in the mapping effort to come to the Waterford 3 site, review the available records NS20552

W3P86-1639 I    '
pcge 3 and their notes, walkdown the basemat, and develop a map showing the areas which were inaccessible in 1983. The results of this effort are included in the attached report as Figure 1.
Figure 4 of the attached report presents a map of the basemat identifying the areas which are not currently accessibic and could not be mapped in the revised baseline inspection described below. Figure 4 will be used as the reference baseline to define the areas to be examined in future inspections.
The areas defined in Figure 4 for future inspections include some areas which were not accessible at the time of the revised baseline inspection mostly because of radiation levels, but which had been accessible during the May 30-June 3, 1986 inspection. These areaa will be included in the surveillance procedure for inspection.
In evaluating the results of the basemat crack sutveillance, it becane clear that the potential existed for inconsistencies during future inspections since the 1983 baseline map did not include all areas currently inspectible, and apparently superficial cracks have been identified which were not on                +
the original crack map. Although the original mapping effort was not limited in scope by a specific criterion on size or characteristics, the principal investigator for the original mapping has stated that some of the cracks being identified today would not, in his opinion, have warranted                  ,
mapping in 1983. To avoid such inconsistencies, LP&L undertook in June a                '
thoreugh reinspection of all accessible areas of the basemat to provide a new baseline against which future inspections will be conducted. The goal of the reinspection was to locate and map all identifiable cracks, irrespective of size and superficiality. To enhance the accuracy of the reviced baseline, the reinspection process included the use of two teams which provided redundant inspections in the areas considered to be the most critical to the mapping effort and included the majority of the uncoated basemat areas. The uncoated areas were chosen for this redundant inspection since superficial cracks, which are difficult to detect, were observed in these areas. The reinspections were conducted using the guidelines included as Appendix B in the attached repcrt. The reinspections were not limited to documenting cracks which met the surveillance criteria of 10 feet or greater in length or greater than .015 inches in width. Therefore, the revised baseline crack maps include short cracks found in the inspected areas, despite the conclucion that only long cracks or wide cracks are critical to the basemat monitoring effort.    (No cracks approaching the .015 inches limit were found).
It is important to note that even these exacting efforts cannot assure that all existing cracks have been identified in the accessible areas. In areas wbere the basemat is covered with an epoxy floor coating (Figure 5 of the attaehed report), cracks have been identified through the coating, and new cracking would also be expected to be identified despite the presence of the coating. However, the type of cracking described as superficial would not be expected to be detectable through the coating, and therefore some of these may exist at this time but are unobservable. Even where the re is no floor coating, the difficulty of identifying and verifying some of the cracks specified as superficial makes it impossible to assure that all such cracks have been located and mapped. These superficial cracks, however, are not considered to be of significance to the evaluation of the structural capability of the basemat.
NS20552

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  . W3P86-1639 Prg: 4 As noted on Figure 4 of the report, several areas were temporarily inaccessible during the reinspection but were included in the surveillance inspection. In these areas, mapping of observed cracks would be limited to those which exceed the 10 feet or longer criterion of the surveillance procedure. Two of the rooms in the temporarily inaccessible areas are uncoated and could potentially allow for observation of superficial cracks during future surveillances.
The revised baseline crack map is intended to be developed depicting all current observable cracks, with cracks identified by a unique number, to the extent feasible, and all inaccessible areas identified on the drawing. This baseline drawing can then be utilized during future surveillances. Future updates will include cracks identified during future surveillances which meet either the length or width criteria agreed to previously with the NRC.
As an additional method of attempting to define the cracks as completely and accurately as possible for future comparisons, LP&L intends to initiate a photographic survey of the basemat areas with identified cracks. It should be recognized that such an effort does not assure that all the cracks can be readily photographed due to the lighting and concrete surface difficulties and, in some instances, the lack of well defined crack indications. This effort should be a useful supplement for comparative purposes, but will not be considered as a substitute for the baseline crack map.
As documented in the attached report, the identification of previously unmapped cracks in the basemat does not conflict with the postulated and analyzed loading mechanisms for the basemat. The previously unmapped cracks are considered to be members of the same family of cracks formed during the construction sequence. The basemat remains an acceptable design, was constructed in an acceptable manner, and is capable of performing its safety function during all postulated loadings including safe shutdown earthquake loads.
If you have any questions or need additional information regarding the items discussed in this letter and the attached report please call me.
Very truly yours,
[(/     -
K. W. Cook Nuclear Support & Licensing Manager KWC/jal cc: B. W. Churchill, W. M. Stevenson (w/o attachment), R. D. Martin, J. Wilson, NRC Resident Inspector's Office (Site), D. M. Crutchfield,            i P. T. Kuo (4) l NS20552 l
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