ML20126A256
| ML20126A256 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 07/10/1979 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20126A095 | List: |
| References | |
| NUDOCS 8002140520 | |
| Download: ML20126A256 (5) | |
Text
.
E'iALUATIO;' REFORT REGARD!!!G THE CONCRETE STRENGTH OF THE h
REACTOR SU!LDING BASE MAT b'OLF CREEK GENERATING STATION On Decer.ber 12 and 13,1977, the K'oif Creek reactor buiicing base ma: was placed as a conclithic pour of approximately 6603 cubic yards of cor.: rete.
At the end cf the 90-cay curing period, thirty-four out of a to ai cf sixty-six sets cf ccncrete cylinders tested exhibited strengths belen he specified ccncrete strength of 5000 pounds per square inch. Thirty sets of the cor. crete cylinc'ers tested a t 90 c'ays had strengths which were lower than the streng;hs previously determined f or the sane batch of concrete af te r 25 c ays.
The SC30 pounds per scuare inch streng r. for the con: rete wa s specified b;. Bechtel (architect-engineer f or the plan:), in ccn;ur.: tion with ctber cesign carameters (e.g., base me. thickness anc re:ar arrar.ge er.t),
in order to satisfy the design criteria spe:ified in the h'ol f Creek Pre-l iminary Sa fety k.a'ys i s F.epor t (PS '? )'.
inese criteria require tr.a: the base mat be able to withstand, without ir.pairmen: of its structurei integrity cr its safety func:icn, the specified design loads and loadinc contina.icns.
Subsequently, the a;piicant condu:ted several investications to determine the possible causes of the anomaly and suber.itted the results of the investicatiors in a report, ca;ed 'k:cber 26, 1978.
The applicant con:l uded in its re;:rt that the 90-day strength cf the con: rete in the reactor builcing base ma; was above 5000 pounds per square in:h and that.he apparent low strength of a portion of the 93 day cylinders was attributed to errors in.estinc.
8002140 Q
A
-c-The matter was investigited by the,'i-~ Offi:e of Inspection and Enforcerert (:E )
with the help of an cutside consultant. As a result of the investiga: 1cn, :(
d ete nninec: tha: the ccn:lusions made by the applicant in its report of Octcber 26,197E, were,.ct sufficien:iy sup:or:ed by the f acts contained I n. h e re p o rt.
setal,i e. tindings c; the investigation per,.ormed by 1 are described ir. a report, cated Fe:ruary 15, 1579.
Subsecuently, the applicant pe rferci, acy;;;ona studies in crder to resos ve the issues and concerns a
expressed by the NRC staff. At our request the applicant al so performed a reanalysis c# the bas = ca, bisec cr. :he c:rcrete strength inoicate by :h e r e s ui: s c f : he 9 r. - cay c y'. i..c e r : s s s, t o d e t a rm i r.e i f t h e d e s i c n stresses are within all:wable I frits and he:her the base mat desien sa:isfies c)]
c....j........s
,2.s.:.
e.,m....o w)
. r =.. c.
41 C.
n.
r~s... a :e.. '.. c..e. e.,,
e- --. : o.... s u.,... u. =.... s. u 1 C n..
o
~l ;. /...e. n. ) C C ;.
>asw,et.-
les w
e..i u
y.
u C. '.ne.r r iar:,e ~i n. e s s C-i a t i c P :n,3 :Cr:re'.e cyl i n"e r remna nt s p ra-V i C'.'s l y : e s '. e C a n.
cays and On :
C yl '..r. e" r erna r..s p re Vlously t est ed
.s.
....e
- r.. :.. - e..... : e e 1' n,
..r2. - a e
.e..
v. e z. c i s p e. e. c..e. c n :. e t, s
s a.
. v........
Cement s37.es.
- ne ac 1t1Cnal con:r:te tes:s Consisted Of Compressive streng:n tests en two-irch cubes sa red fro- }.he cylinder remnants, anc' petrocraphic exar.inatior and chemical analysis of a selected group of cy:1nce. remnan:s. r >.1 c. : ness test resul:s are described in ceta11 in rep;rts subri::ed by the applican; by letters, cated February 2c, 1979 a nd F'ay 3, 19 79.
In actition, the 5:ruc ures Laboratory of the Corps of engi ne'ers, U g. -
c.:.'z;erveys,txperimen; s,tatien,
\\,;.
sburg, Mis si ss i ppi, conduct ed cx e
a petrographic exar..ination cf cer.: rete thin sections and documented its c on:l us i o r.s i r, a re p ort, da t e d J t'y 2, 19 7 9.
v
=
We have completed our review of the results of the tests performed by the Portland Cement Association and the evaluation perfcrmed by the Corps c:
Engineers.
E,ased on our review of the test data, we concl ude that there is no evidence of degradation of concrete strength nor is there any sign of substandard cr f aulty cement.
Hcaver, ite cannot concl ude that the lov SG-day strencths cbtained with the cylinder tests are attributed to testing machine f actors er testinc ccnditions as claimed by the applicant.
We note tha; the 90-day cylinder streng:h tsst results correlate very well with the twc-inch cube compressive screncth test res u' ts.
In fact i
if So.h s ets of results are plottec, th!
w: c u ves would almost be parallel.
Eecause of :his excellent correla*.icn betwetn :ne s.rencths of cubes and cylincers, we con 1ude that the 90-day :y;inder test resuits shouid ce censicered as valid and that these resul.s shoulc be used in assessing the load carrying capacity cf the base a.
Tne ap;iicant c;m;ieted the requested reena~ysis of the base mat and.the results were suomitted by letter, datec' May 10, 1979.
In crder to perform the reenalysi s, the a:plicant first detemi.ed I ccncret.e strength for the met based en the 90-day cylinder test risul.s by utilicine the established ecceptance criteria in Section 4.3 of Americ2n Concrete Institute ( ACl)
{
St andard 313-71.
We concur with the applicant that the resultant strencth is 4450 pounds per scuare inch.
Tne reanalysis of the base mat was then pedormed in accordance with the criginal cesign comitments of the 'sif Creek P3AP, by using the calculated concrete strencth of 4450 pounds per scuare inch.
A seismic soil-strue:ure interaction analysis was performed by using the co ?vter code FLUSH based 1
4-en a finite el ement approach.
Since the We'.f Creek plant is one of the five SZ?PS standard plant units, the SNUPPS envelope design earthquak e ground motior.s of 0.209 for the safe shutdown earthquake (SSE) and 0.129 for the c;eratir; basis earthcuake (OEE) were used c generate the seismic cesign forces for the base mat.
Tne SSE ard OEE fer the Wolf Creek site are 0.129 and O.Cr.'c, respectively.
The seismic f orces generated by the finite element apprcach were compared wit'. th:se cenerated by another established metroc cf analysis, the fixed r
- ase a;; cach, to cemenstrate that :ne seisric icads usec in the reanalysis a re cc ns erva t i ve ior the 'r.'ol f Creek pi a nt.
For the fixed base approach, the '.icif Creek site specific design sar;hcuike ;rcund m:tions of 0.12 c f or
- he ES E and 0.0'g for the OEE were used as 'n;u: mo. i ons.
Tne es'.its of the reanalysis by bo:h a;proa:hes i ncica:e that the case mat mes:s the desien criteria for the W:1f Creek. f acility and that the tensile stress es cf the reinfcrcing steel are cen:r:liir.c.
Thus, the base cat cesi;r. is ::ntrolled by tension ar.d the lead carryng capacity of the ma: is ;cverned primarily by the am:ur.: cf reinforcing bars provided in the bas e mat.
Lowering the specific concrete desion strength f rom 5000
- o 4460 pcunds per square inch has very lit:le effe:t on the load carrying capacit;. cf the base mat.
Eased on cur review of the test results and the results of the reanalysis,
. we conc ude that the base met concrete strer.gth has not retrogressed, tha*. the strength of the base mat meets the original design criteria
.5-in the V:if Creek PSAR, and that the me; will withstand the specified design leads and Icading ccmbinatior.s witho;t impairment of its structural integrity or its s afety function.
4 1
1 I
1 I
I l
9 l
l
!