ML20054F247
| ML20054F247 | |
| Person / Time | |
|---|---|
| Site: | Perry  |
| Issue date: | 06/07/1982 |
| From: | Davidson D CLEVELAND ELECTRIC ILLUMINATING CO. |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8206150361 | |
| Download: ML20054F247 (4) | |
Text
THE CLEVELAND ELECTRIC ILLUMIN ATING COMPANY P o box 5000 m CLEVELAND. oHlo 44101 e TELEPHONE (216) 622-9800 e ILLUMINATING BLOG e 55 PUBLIC SOUARE Serving The Best Location in the Nation D:lwyn R. Davidson vlCE PRESIDENT SYSTE M E NGINEERING AND CONSTRUCiloN June 7, 1982 Mr. James G. Keppler Regional Administrator, Region III Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137 RE:
Perry Nuclear Power Plant Docket Nos. 50-440; 50-441 Final Report on Biological Shield Walls Concrete, Units 1 and 2 [RDC 34(81)]
Dear Mr. '(eppler:
This letter serves as the Final Report required by 10CFR50.55(e) concerning the low density heavyweight. concrete in the Biological Shield Walls of both Reactor Buildings.
Initial notification that this condition was under evalua-tion by The Cleveland Electric Illuminating Company was made by Mr. R. L.
Vondrasek to Mr. L. McGregor of your office on July 15, 1981. This condition was subsequently detailed in our Interim Reports dated August 14, 1981, and December 18, 1981.
This report includes a description of the deficiency, an analysis of the safety implications, method of evaluation, and the corrective action taken.
Description of Deficiency Light, chalky material, up to three inches (3") thick, was observed at the top I
construction joints of the heavyweight bioshield concrete placements, for Reactor Buildings 1 and 2 at elevation 654'.
This material has a bulk specific gravity of approximately 75 pounds per cubic foot, rather than 195 pounds per cubic foot per the specified design requirement. Due to inaccessability, direct inspection could not determine that this material was at the top construction joints of the previous heavyweight placements. This condition was documented on Nonconformance Report CQC 2314
,Y 8206150361 820607 JUN I O 1982
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PDR ADOCK 05000440 g
Mr. Jcmes G. Kcpplcr Juna 7, 1982 Analysis of Safety Implication The Biological Shield Wall is a protective shield wall surrounding the reactor vessel designed to limit radiation damage to drywell equipment during operation and permit personnel to work in the drywell during reactor shutdown. If the shield deficiency had gone undetected and the reactor had gone into full power operation, the radiation levels outside the deficient locations would have exceeded the drywell environmental design conditions and potentially compromised drywell equipment integrity. However, this eventuality is unlikely because if the deficiency had gone undetected during the plant's construction phase, it would have been discovered during the low power testing radiation survey.
This shield deficiency does not compromise the structural integrity of the l
Biological Shield Wall because the steel portion of the wall does not rely on the interior high density concrete for support.
Method of Investigation A radiographic survey employing gamma spectrometry techniques has been per-formed on the Unit 1 and Unit 2 bioshield walls. Measurement location criteria were initially based upon construction joints between concrete pours and points most likely to exhibit reduced concrete densities (i.e., below hori-zontal stiffener plates, beneath penetrations, etc.).
Subsequent measurement locations were specified to account for structurally similar areas which were identified as deficient in the inf.tial radiographic survey.
... Unit 1 Survey Results A total of 233 measurements were taken at 152 locations on the Unit 1 bioshield wall. Multiple measurements were taken at some locations to envelope areas of reduced density. These measurements indicate that normal attenuation factors and concrete densities are present at 123 of the 152 locations. Attenuation factors greater than those expected are present at 4 locations. Reduced attenuation factors are present at 10 locations and extremely reduced attenuation factors are present at the remaining 15 locations.
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... Unit 2 Survey Results A total of 205 measurements were made at 134 locations on the Unit 2 bioshield wall. These measurements indicate that normal attenuation factors and concrete densities are present at 119 of the 134 locations.
Attenuation factors greater than expected are present at 2 locations.
Reduced attenuation factors are present at 6 locations and extremely reduced attenuation factors are present at the remaining 7 locations.
The attentuation factors discussed above have been evaluated by the Engineer and the following conclusions have been postulated. Attentuation factors greater than those expected are due to increased steel thickness at the identified locations. Reduced or extremely reduced attenuation factors represent bioshield wall configurations with insuf ficient densities or quan-tities of concrete between the inner and outer wall plates.
t Mr. J; mea G. K:ppist Jun2 7, 1982 The deficient areas identified in the radiographic survey were then categorized as follows:
1 Areas in the core region, which is defined as 5 feet above and below the core active fuel (Elevation 617 '-0" to 640'-0").
2.
Areas outside the core region.
Corrective Action This report deals primarily with one aspect of a two-part problem. Specifically, we are defining the plan for repair of areas of the bioshield wall which contain low density concrete. Another report, RDC 42(81), covering the issue of extremely reduced attenuation in the bioshield walls, will follow later this month.
The low density areas have been defined and enveloped for evaluation and specification of appropriate corrective action on the basis of the following criteria:
1.
Core Region - a minimum nominal density of 180 lbs./cu. ft. is acceptable.
However, a local minimum nominal density of 140 lbs./cu. ft. is acceptable if the area does not exceed 1% of the interior core region surface area (approx. 2,000 sq. ft. area).
2.
Outside Core Region - a minimum nominal density of 140 lbs./cu. ft. is acceptable.
Areas in the bioshield walls identified as having less than acceptable minimum nominal density will be repaired by cutting access holes in the one inch steel wall plate, removing the low density material and replacing it with a high density grout (nominal 210 lbs./cu. ft.).
This grout has been successfully tested at the manufacturer's lab and on-site.
Test placements at the manufacturer's lab provided the acceptable ranges for variables such as water percentage, temperature, unit weight (densities), etc.
The on-site testing was performed using a mockup of the bioshield wall. Grout pour holes and venting holes were located in the mockup to simulate probable field conditions. The mixing and placement of the grout was controlled and monitored during the tests and the grout was allowed to cure for two days.
The forms were then pulled and the grout was shown to have exceptionally uniform coverage throughout the mockup. A radiographic survey was performed on the mockup and the resultant density ranged from 200 to 210 lbs./cu. ft.
Implementation of this corrective action will provide the minimum nominal densities necessary to assure that radiation levels outside the bioshield walls will not exceed the drywell environmental design conditions.
Mr. James G. Kcpplsr Juna 7, 1982 We presently anticipate repairs will be completed by December 31, 1982, for Unit I and July 1, 1983, for Unit 2.
Sincerely, 891 Dalwy R. Davidson Vice President System Engineering and Construction DRD:pab cc:
Mr. M. L. Gildner NRC Site Office Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, D.C.
20555 U.S. Nuclear Regulatory Commission c/o Document Management Branch Washington, D.C.
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