ML20094J441
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b;.d 4 9 b Per use of 19He form, ese AR 340 f 5: the armt essecy 6s TAGo, F96FEREfeCE OR oFPICE SYM5aL SU5JEc7 Midland Nuclear Power Pisnt. Meeting for reviewing the NCDED-G preliminary design of the proposed remedial measures for
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the Service Water Pumping Structure (SWPS).
To FILES PROM HaRI SINGH oATE 18 dept 81 CMT 1 NCDED-G SINGH/af/35733 1.
Date and place of the meeting.
The meeting was held on 17 September 1981 at the Nuclear Regulatory Commission's (NRC) office in Bethesda, MD.
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Attendees:
Darl Hood NRC Joe Kane NRC Liman Heller NRC Ross Landsman NRC Hari N. Singh Corps of Engineers, NCD Dennis Budzik Consumers' Power Company (CPCO)
N. Ramanuzan CPC0 Rajdan CPC0 Thiruvengadam CPC0 Bimal Dhar Bechtel Corporation Ed Burk Mueser, Rutledge, Wentworth and Johnston, (MRWJ) 3.
General Information about SWPS.
Service Water Pump Structure is a category-I structure.
is essential for safe operation and safe shutdown of the plantIts satisfactory performance in shape with overall dimensions of 106' x 86', and is built in two parts on split el vatiThe A main part, with a approximate size of 86' x 72', is rounded on a stable foundation of e
ons founded on compacted fill (el= 617.00). natural soil (el= 587.00), and subsidiary pa The subsidiary part is built monolithic with the main part along their common dimension of 86'.
cracks appeared on the cross walls of the sub2idiary structure. Subsequent to the construction, CPC0 to determine the cause of the crackings, revealed that the fill materials which prov An investigation by the support to the subsidiary part are not adequately compacted.
Based on this finding, the NRC and the Corps of Engineers concluded that own weight and under the foundation pressure.the inadequately compacted soil settled under its loads and change in the structural behavior of the subsidiary structure (from a supported on mat foundation to a cantilever structure supported on elastic foundation) which caused the crackings.
The existing cracks and their further propagation, and development of new cracks under the continued settlement of the fill materials are considere dangerous to the safe operation of the plant.
Several alternate methods to provide a stable supportThe remedial ture are needed.
part were considered by the CPCO, but they did not meet to the subsidiary the design requirements of the state-of-the-art methods of static and dynamic design, and as such, were not acceptable to the Corps of Engineers and the NRC.
foundation walls; the meeting of 17 September 1961 was held to discuss proposal.
8408140319 040718 PDR FDIA RICE 84-96 PDR g,F g g g Previous Eo:TioNS WILL BE USEo 0 U.S. G.P.O.
1980-665841/288
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New Proposal to Stabilize the Structure.
.Mr. Ed Burk of MRWJ, a soil and foundation consulting engineering firm, New York, explained the new remedial measures to correct the subsidiary part i
of the SWPS. The explanations included the followings:
(a) Provide foundation walls under the outer walls of the subsidiary structure. The foundation walls will be built from the underside of the existing foundation slab, through the inadequately compacted fill, to the natural soil-(El 587.00), and as such, will transmit the structure load directly to the natural material.. Mr. Burk exhibited preliminary drawings showing that the foundation walls will be built in sequence of sections so that no temporary support would be needed during the construction. Excavation for the construction of first section of the wall in the sequence, will be such that the remaining soil support will provide adequate support to the structure for the short period of time needed to build the first section. After the first section is completed.. excavation for the second section in the sequence will be mede, and the load of the structure will be carried by the completed first section and the remaining soil support.
In this way, the entire foundation wall will be completed without costly temporary support.. Drawings for accesa shafts and excess tunnels needed for the construction were exhibited.
(1.) The site will be dewatered to elevation 587.00. Because of this dewatering, there will be additional settlements in the compacted fill, causing further reduction in soil support to the subsidiary structure which, in turn, might cause additional crackings in the structure. To aliviate this problem, the subsidiary structure will be tied up with main structure with post tensioned cables (see Figure...).
(c)
Mr. Burk also touched the theoretical design aspects of the new proposal (underpinning). He pointed out that there will be some differential settlements between the underpinning walls and the" main portion of the struc-Effects at such differential settlements are not critical to the struc-ture.
These differential settlements constitute three parts; (i) settlement ture.
due to shrinkage of new concrete wall, (ii) creep in new concrete wall, and (iii) settlements in foundation soils due to additional load transmitted to them through the new walls.
Mr. Burk showed graphs of the settlements versus t ime.
(d)
Mr. Dewar of the Bechtel Corporation stated that when the underpinning walls will be completed, and the structure loads will be transferred to them, the existing foundation slab of the subsidiary structure will act as simply supported between the main structure and the underpinning walls. The slab has b2en checked for such new redistribution of loads and is found to be structurally adequate.
Mr. Dhar also pointed out that "fo/L 59pr6 CONST4NT,5 eve #E uMD
-Inf THE SrRUCTUR/FL RNALVS/S TO 'Ceivf/baW Tiff GFFECT of SdTTLEMENI5 -
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Discussions by Messrs. H.N. Singh, Joe Kane and Liman Heller.
(i)
Mr. H. N. Singh stated that the CPCO proposal, to construction the underpinning walls in sequence of sections and to use them to temporairly sup-port loads many times more than they are intended to carry on long term basis, might cause shear failure in foundation soil. CPCO should perform analysis, determine factor of safety against shear failure in foundation so-1 under the
' maximum load an individual section-of underpinning walls is likely to be sub-jected during construction, and furnish the analysis for review.
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(ii)
Mr. Hell:r ccked, "Whnt alttrnativs method th2 CPCO would adopt if ths foundation under an individual section of the underpinning walls fails in shear"?
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He requested CPCO to furnish the details of alternatives to be followed in case of such failure.
(iii) Messrs. Kane and Singh requested CPCO to furnish the details of static zi and dynamic spring constants used in analysis of the Strac+ure The
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details should include: method used in determination of spring constants, magni-tude of spring constants and assumptions, in any, made in determination of the spring constants.
(iv)
In regards to the CPC0 proposal of tieing the subsidiary structure with main structure with post tensioned cabics, Mr. Singh stated that such arrangement would bring additional vertical load on the main structure. CPCO should determine the additional foundation pressure under the main structure, 3
determine resulting f actor of safety, and furnish the results for review.
I (v) The NRC staff and the Corps of Engineers are of the opinion that information provided in the meeting should be properly documented by CPCO and should be forwarded to the staff and the Corps of Engineers for detailed r
review. The material presented in the meeting were not ad uate to make final decision regarding the adequacy of this proposal to stabil.ee the Service Water Pump Structure.
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Copy Furnished:
RARI N. SINGH, P.E.
Mr. Otto, NCEED-'f Civil Engineer, NCDED-G Mr. Kane, NRC f
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