ML19242D751
| ML19242D751 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 07/10/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML19242D746 | List: |
| References | |
| NUDOCS 7908170548 | |
| Download: ML19242D751 (5) | |
Text
EVALUATION REP.)RT REGARDJf.G THE C0!iCRETE STRENGTli 0F THE REACTOR BUILDIhG EASE MAT WOLF CREEL GENERATING STATION On Les.ccher 12 and 13,1977, the Wolf Creek reactor builcing base mat was placed as a mor.elithic pour of approximately 6600 cubic yards of cor. crete.
At the end of the 90-day curing period, thirty-four out of a total of sixty-six sets of concrete cylinders tested exhibited strengths below ne specified concrr te strength of 5000 pounds per sc,uare inch.
Thirty sets of the concrete cylinders testid at 93 days had strengths which were icter than the strengths previomly determined for the same batch of concrete c.f te r 28 d ej s.
Tbc 5000 pounds per square inch strength for the concrete was specified by Bechtel (architect-engineer for the plant), in conjunction with other design parameters (e.g., base mat thickness and rebar arrange.nent),
in order to satisfy the design criteria specified in the Wolf Creek Pre-l iminary Safety Analysi s Report (PSAR).
These criteria require that the base mat be able to withstand, without impairment of its structural integrity or its safety function, the specified design loads and loading cocinations.
Subsequently, the applicant conducted several investigations to determine the possible causes of the anomaly and submitted the results of the investigations in a report, dated October 26, 1978.
The applicant concluded in it. report that the 90-day strength of the concrete in the reactor building base rat was abave 5000 pounds per square inch and that the apparent low strengtn of a portion of the 90 day cylinders was attributed to errors in testir.g.
7908170sq
,.]
. The matter was investigated by the NRC Office of Inspection and Enforcerent ( E) with the help of an outside consultant. As a result of the Investiga;.v:., ;;
determined that the conclusions rnade by the applicant in its report of October 26, 1978, were not sufficiently supported by the facts cor.tained in the report.
Detailed findings of the investigation performed by IE are described in a report, dated February 16, 1979.
Subsequently, the applicant performed aJditional studies in order to resolve the issues and concerns expressed by the fRC staff. At cur request the applicant also performec a reanalysis of the base mat, based on the concrete strength indicatec by the results of the 90-day cylinder tests, to determine if the design stresses are within allrwable limits and whether the base mat design satisfies all cornitments made in the Wol f Creek, PS AR.
Additional tests were performed by the Construction Technology Laboratcries of the Portland Cenent As.ociation on 48 concrete cylinder remnants pre-viously tested at 90 days and on 26 cylinder rernants previously tested at 28 days. Cement compression strength tests were al so perf ormed on f our cement s riples.
The additional concrete tests consisted of compressive strength tests on two-inch cubes sawed from the cylinder remnants, and petrographic examination and chemical analysis of a selected group of cylinder remnants. All of these test results are described ir. detail in reports aubmitted by the applicant by letters, dated February 28, 1979 and May 3,19 79.
In addition, the Structures Laboratory of the Corps of Engineers, USAE Waterways Experiment Station, Vicksburg, Mississippi, conducted a petrographic examination of concrete thin sections and documented its conclusions -in a report, dated July 2,1979.
. ; '1
. We have completed our review of the results of the tests performed by the Portland Cement Association and the evaluation perf ormed by the Ccrg a Engineers.
Based on our review of the test data, we concl ude that there is no evidence of degradation of cor. crete strength nor is there any sign of substandard or f aulty cement.
However, be cannot concl ude that the low 90-day strenr tos obtained with the cylinder tests are attributed to testing machine f actors or testing conditions as claimed by the app'iicant.
We note that the 90-day cylinder strength test results correlate very well with the two-inch cube compressive strength te t results.
In fact o
if both sets of results are plotted, the two curves would ainost be parallel.
Because of this excellent correlation between the strengths of cubes and cylinders, we conclude that the 90-day cylinder test results should be considered as valid and that these results should be used in assessing the load carrying capacity of the base mat.
The applicant completed the requested reanalysis of the base mat and the results were submitted by letter, dated Fay 10, 1979.
In order to perfore the reanalysis, the applicant first determined a concrete strength f or the mat based on the 90-day cy'iinder test results by utilizing the established acceptance criteria in Section 4.3 of kierican Concrete Institute (ACI)
Standard 318-71. We concur with the applicant that the resultant strength is 4460 pounds per square inch.
The reanalysis of the base mat was then performed in accordance with the original design comitments of the Wolf Creek PSAR by using the calculated concrete strength of 4460 pounds per square inch.
seismic soil-structure interaction analysis was performed by using the computer code FLUSH based Q
J
On a finite
-4.
elvr five SNUPPS stan ent approach.
motions dard plant unit Sir.ce t he Wolf Cr of 0.20 eek 6
operating basis 9 for the s, t he SNUPPS e plant is one safe of t i.
shut down nv lope design e
forces for the b earthquake (OBE) 5 earthquake (SSE) earthquart ase ere 9
to gen and 0.12 mat.
us d and 0. 06, respect i The $5L and OSE f erate the 9 for t t
\\
e p,
v ly.
e The or the Wolf seismic desig:
seismic forces 9 Creek s i te with ar thos terated e C.1.
e gener ted by an by the finite a
base other elem approach, to demon conser strate thatestablished m thodent a are e
ere compa red the Wolf vative for the Wol seismic loadsanalysis, the fixed of the Creek site Creek f
plant.
usec in tne the SSE and 0 specific design For the fixed b eana lys is r
06g for the OBE wr.arthquake grou approa h, ase The c
ere nd motions res lts used as input m ti 0.12 g for u
of of the r
m eets the design eanalysis by both o
ons.
criteria for the W approaches indicat stresses of the olf design is reiriforcing ste l Creek e that facili the base controll.d by tensi ontrolling.
that e
are ty and mat mt c
a is gov the tensile on in the bas ern d primarily by tthe load carryi hus, the bas e
and T
mat.
he e mat e
to 4460 pounds p Lowering the ount of ng capacity of am sp?cific reinforcing bars the er capacity of squar concrete provided e inch has cesign the base ver.
- ttle strength mat; Based on effect on the load from our rev iew conclude that the test r carrying we of that the base esults and the a
the r strength of m t concrete esults str of the base ength has the panalysis mtm a
eets the not retrogr original
- essed, design criteria I
D to 1 3 e
in the Wolf '
Creex PSAR, end design loads that the integrity or itsand loading combinati n t will withstand o
ons the
(
safety funct ion.
without impair speci fica ment of its s t ruc t t. r c
t mm
=
J s,
+
515 N 1st StreetMs. Wanda Christy Burlington, KS i
66839
Dear Ms. Christy:
William H. Ward the Mid-America,Coaliti by petition dated Dece bby petitions dated Jan m er 27, 1978on for Energy Alternativuary 11 an Project, and other pe Wolf Creek Generating Srevoke Construction Pe on behalf of the Criticales (MC tation Unit No. 1m t No. CPPR-14
. Pollack, at the Commission suspendMa For the reasons A copy of stated in the enclosed de i orizes construction or of the its review in accordthe decision will be fil c sion, these petitions As also provided in 10 CFwith 10 CFed with the Secreta are denied.
ance action of the Commission t R 2.206(c)R 2.206(c) of the Comm the Commission the Co
- 20) days, the decision will constitut s r time.
wenty on its own motion (institutes r n
after the date e th of issuance,e final eview of the decision within th unless at Sincerely, Victor Stello, Jr Director
Enclosure:
Office and Enforcementof Inspection Director's Decision 'fod 10 CFR 2.206 er t O3(S on3 WPU:SM 7/12/79 Office b]
RCI d~
JOB K Su~rnan:e q
Date JBH
- IE derson XOOS 7/ /79 Thornburg 7/g /79 GCGower ELD $
V JPMubray D:lE 7/ /79 7/ /79 VStello 8
7/ /79
. lL t
,J
'