ML20126A167

Summary of Concrete Problems

ML20126A167
Person / Time
Site:	Wolf Creek
Issue date:	03/05/1979
From:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
To:
Shared Package
ML20126A095	List: ML20126A093 ML20126A097 ML20126A120 ML20126A148 ML20126A167 ML20126A205 ML20126A208 ML20126A242 ML20126A256 ML20126A267
References
NUDOCS 8002140471
Download: ML20126A167 (3)

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Sumary of Concrete Problems Wolf Creek Nuclear Plant O

Cencrete was placed for the reactor ccntainment building base mat in a centinucus caeration on December 12 and 13,1977. The total volume of the 10 foot thick met was nearly 5503 cubic yards. Sample test cylinders of the concnate were taken during the placecent and subsequently tested at 7 and 28 days after placerent to determine he rate of strength gain. Sample cylinders for the final 90-day strength detemination also were obtained. On March 13, 1978, the 90-day cylinders were estec---about 9% failed to meet ene test criterion; about 3Ci failed to meet a sec nd est criterion. The NRC inspector was infemed of the apparent icw cylinder streng:h on March 15, 1978. Inspection Repert. SIN 50- 452/75- 0 4, dated kar:h 31, 1978, noted that the question of the 90-day strength of the concrete for the reactor containment base mat had not been settled.

The licensee, Kansas Gas & Ele:tri: Comoany, inferred the NRC on May 3,1978 that, in the licensee's opinion, the a: parent low test results of the concrete strength were n:t required to be rep:r.ed to the NRC. The licensee agreed

, to send the 5RC for its information. a re? ort about the licensee's investigations which had been initiated. The NRC k provided interim re? ores, dated "ay 3,1978, May 25,1978, August 18, 1975, and September 29, 1978, about the crogress of the li:ensee's investigation. The licensee's final report was subcitted en October 26, 1978.

Review cf the final repcrt by the NE: raised cuestions about the conclusions conuined in the report. On 5:vember 13, 1978, the Region IV (Dallas) Office of the NRC, with tha assistance of a consultan:, began an investigation into the apparent ios strength ccocrete test' cylinders. By December 1, 1978, the investigators had c:ncluded fro the inf:: nation available that the specificati ns the licenses had established for acceptance of the concrete had not been c.e: and that the reac:cr ccc .lir, ment base mat strergth was in qu esti on. The NRC preliminary evaluation of the base mat concrete strength based on the test cylincers indica:ed a value about 10% belos the intended strength of 5,000 pcunds per square inch (osi). '

Cn Decerber 5,1978, a teeting was held by ths Director of NRC Region IV with the lice,see to discuss the status of the investigation and to e :phasize the importance placed on this problem by the NRC.

, Cn December 13,197E, the licenses reported another concrete deficiency, a -

i through-wall void in the concrete wall beneath the equipment hatch in the reactor containant buildinc. Ancther void was found beneath the personnel lock, but was net a throuch-wall void. In a letter issued on Dece:nber 19, 1978, the NRC, through its Regica IV Cffice, informed Kansas Gas & Electric Company cf the NRC's concerns regarding the concrete problems and the actions that the licensee was to address in order to satisfy these concerns. The concerns related to the everall quality assurance pregram including controls and procedures relatef to concrete placement, cuality control, inspection, testing and cualif :ation of persennel, as well as the independence of the inspection and verification or;anizaticas. The NRC aisc :enfir ed a comitment by the licensee to s:co the cia:ement of concre:e ir, safe y related structures until the L cutiiN assfran:e matters outiined in the letter were corrected and de .onstrated l- to the' satisfaction of the NRO.

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On January 4,1979, a resting was called by the NRC to discuss the findings '

cf the NRC investiga:ica and the position cf the licensee on those findings. '

The meeting, held in Set?.esda, Maryland, included representatives of all involved parties and mec.hers of the pubite and the news nedia. ll I As a result of the nesting, the licensee initiated additional testing on cube samples stated to have been cut from the remains of the cricinal 90-day test cylinders. The licensee submitted a report en February 28,1979, describing l the resuits of these additional tests. The NRC in a letter dated February 8,1979, j requested that .5e licensee censider cut cube sarole testine on remnants of l 25-day test :ylir.ders and that an assessment of t'he concret ~ strencth be made l tsing the test data obtained from ali of the :es: cylinders. It was also j requested that the value for the strencth obtained be used to evaluate the  ;

load carryin; capacity of the structure for the required loading combinations.  ;

1 Regien IV, after additional ir.spections at the site curing February 1979, concluded -hit the licer.see had satisf actorily ret the c~n-itments agreed to in the Cecember 19,1975 ist er. On March 5,1979, another letter was issued by Re;ien :V wai:h called for no fur her pla:emert of co.cre:e in the reactor l contain:ent buiidin; until the cuestien on the acceptability of the base mat 1 has been resolved. The licensee wiii, however, complete the necessary repairs

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The licens se resumed pla:e:Ent cf safe y related con: rete except for the reacter containrer.t or. P. arch 6,1979. On March E, 1;79, the licensee stopped vork on safe:y reia:ed concrete a,:er licensee cua,il:y control persennel

bservei that c:ncre:e was beinc coved by vibrat:rs over a greater horizontal

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.nas ce:iciency was o. served cis:ance t.aan cent 1:te.j ov :.ne coverninc coce.

urinc me : t a:emen: ci a wal.: -sectior. c: the auxillarv cuilc..i ng. ine initia:.ve ::r the 5 cp-scrk a: tion was aken by t.ne licensee. .he licensee i

lif ted the s cp-scrk crder ca March 21, 1979, relative to piacement of safe:y related cor.: rete ex:ept for difficult pla:ements and concrete in the reacter cen air.rer.t building.

The licenses lifted the sto;-work ordcr on March 22, 1979, relative to placemer.t of safety related c:ncrete including difficult placements but excludir.g c:ncrete in the reactor centain er.t buildine wall. The stop work order regardir.g pia:emer.t of concrete in the reactor containment building wall is s:1:.1 in er ect.

errer e for approximam ely six weeks, per.crmet an augmentec inspection

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, and running throuch the week of May 14,197", to observe work activities pertaining to placement of safety related con: rete.

The licenses co pisted a reanalysis of the base mat and submitted the resuits te NRR :n May 10, i"79. The reanalysis was performed in 'accordance with the origir.al design cc:r.itrents of the 'n'oif Creek PSAR usinc a calculated concrete

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NRC reccested the U. 5. Amy Engineer Waterways Exoeriment Station (VES),

Vicksburg, v.ississippi, to take a petrographic examination of concrete thin sec:icas prepared by thi FCA and examine fragments of cylinders. WES submitted a report cf their examinatica on July 5,1979.

On July 10, 1979, NRR issued an evaluatier stating that based en their review of the test resti:s and the results of the reanalysis, they conclude that the base ma: co.. crete stren;th has not ret,rogressed, that the strengths of the base mit reets he cri;inal desigr criteria in the 'n'olf Creek PSAR, ar.d that the mat viii withstand the scecified desicn loads and loading combinations wi thout impair dr.: cf i;s s:ructural inteirity or its safety function.

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