ML19289C829
| ML19289C829 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 01/12/1979 |
| From: | Hood D Office of Nuclear Reactor Regulation |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7901250252 | |
| Download: ML19289C829 (11) | |
Text
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JAN 121979 DOCKET NOS. 50-329 50-330 APPLICANT:
Consumers Power Company FACILITY:
Midland Plant, Units 1 & 2
SUBJECT:
SUMMARY
OF DECEMBER 4,1978 MEETING ON STRUCTURAL SETTLEMENTS On December 4,1978, the NRC staff met in Midland, Michigan with Consumers Power Company (CPC0), Bechtel Associates, and consultants in geotechnical engineering to discuss excessive settlement of the Diesel Generator (DG) Building and pedestals, and settlement of other seismic Category I structures. These technical discussions followed a site tour on December 3,1978 during which the NRC staff obs6rt d each of these structures. Attendees for the tour and technical dis-cussions are listed in Enclosure 1. is the agenda used during the technical discussion.
===1.
Background===
Pursuant to 10 CFR 50.5:,(e), CPC0 notified Region III of the Office of Inspection and Enforcement (I&E) on September 7,1978, that settlement of the Midland DG Building foundation and generator pedestals was greater than expected and that a soils boring program had been started to determine the cause and extent of the proble;a. An interim status report was provided I&E by CPC0's letter of September 29, 1978.
I&E conducted inspections on this matter on October 24-27, 1978 and issued inspection report number 50-329/78-12; 50-330/78-12.
2.
History The Bechtel representative identified the Category I structures and the type of material supporting the structure:
a.
Containment - Glacial Till
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b.
Borated Water Storage Tank - Plant Fill Diesel Generator Building and Pedestal - Plant Fill c.
d.
Auxiliary Building - Part Glacial Till & Part Plant Fill Service Water Intake - Glacial Till (Completed portion only) e.
- Plant Fill (Small portion yet to he' constructed)
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JAN 121979 The settlement monitoring program began in June 1978; to date the measured settlements are as follows:
Containment - 1/4" to 5/8" over last 1-1/2 years Auxiliary Building - Approximately 1/8" (central portion)
Service Water Pump House - 0 to 1/8" Diesel Generator Building - 3 to 4" since footing was poured October 1977 and walls in Spring 1978, The four electrical duct banks rising into the DG Building, and which extend downward into the glacial till, were cut loose to remove the settlement restriction on the north side of the DG Building. When the duct banks were cut loose, settlement on the order of 2" occurred on the north side of the DG Building at a rapid rate. The east wall exhibited rapid settlement (1/8" in one week), but the west wall showed very little subsequent settle-ment. This indicates that the east wall was being held up by the duct pedestal.
3.
Soils Exploration Bechtel discussed the soil exploration program, including the boring program and laboratory testing of the foundation materials.
The conclusion that was made by Bechtel is that the material varies across the site in strength properties, i.e., unconfined compressive strength from 200 PSF to 4000 PSF and shear strength from 100 PSF to 2000 PSF. The soils classification ranged from Cl to M1.
Bechtel also discussed possible causes based on input from a con-sultant, Dr. R. Peck. Some of these causes were:
(1) Variable quality of material used in the plant fill, however, the quality control records do not indicate the variation.
(2) Fill may have been placed on the dry side of optimum moisture, and then when the water table rose inundating the fill, the material may have become " soft."
(3) Initial fill may have been placed satisfactorily but after installing pipe trenches and duct banks, the fill may have been disturbed.
- 3. -
JAN 121979 4.
Consultants Perspective Dr. R. B. Peck' stated the following:
a.
The compacted fill is comprised mainly of glacial till and was excavated from the cooling pond area.
b.
Evidence exists from the Dutch cone curve that the looser and softer areas are limited to. local zones or lenses.
c.
Water content is higher than at the time the fill was placed, Settlement of the till has been occurring since original placement of fill, accelerated by increased moisture content resultin_g from filling of the discharge cooling pond. Soil settlement is occurring under its own weight and the added weight of the building is believed to be insignificant.
d.
The DG Building would probably not have settled as much if the material had not been so wet (moisture content is high).
e.
Bearing capacity is not a problem for the footings.
f.
Short of removing all the fill above the hard glacial till, a "preload" program would be the best approach. The preload purpose would be to consolidate the fill materials.
g.
The settlement with the preload would tend to be rapid (a few weeks to a few months),
h.
The preload is a necessary first step even though other measures might be necessary.
1.
The main unknown is what might happen to the rate of settlement as the water table rises and saturates the fill, J.
Preloading would occur in early 1979 and the sand used as the surcharge would be removed in mid-1979, Mr. C. J. Dunnicliff of Goldberg, Zoino, Dunnicliff & Associates described the instrumentation program to monitor the settlement of the foundation material and structures during the preload, The purpose of the instrumentation is to determine if the surcharge is doing its job of consolidation and if it is causing any harm to the structures or utility lines under and around the building,
JAN 121979 a.
Instrumentation for the structure will include optical survey measurements as well as monitoring of cracks using electrical devices.
Four locations foc 9e electrical devices have been chosen; two on the exterior of the east wall of the DG Building and two on the west wall of bay number four in the DG Building.
A mapping of cracks will be developed.
b.
Foundation monitoring will include devices to measure settlement and pore water pressure. A total of 60 anchors will be installed (20 groups of 3 at different elevations). A total of 40 piezometers are to be installed to measure the pore water pressure.
The consultants indicated that 6" settlement would not be a surprise and that up to as much as 18" could occur. The preload will be made up of 15 to 20 feet of sand piled in and around the DG Building.
No more than a 5-foot differential in the sand level between bays would be pennitted.
The NRC questioned the effect of settlement and preloading on the condensate lines located under the DG Building. Fixed points for the piping, such as the Turbine Building wall, are also of interest for the potential of cantilever effects. Bechtel explained that the 20-inch condensate lines are encased in 24-inch lines surrounded by concrete and resting in well compacted sand.
Instrumentation will be included to monitor the condensate lines.
The possibility of cutting the lines loose at the DG Building and the Turbir.e Building is also being studied. The condensate lines have no safety-related function for the Midland design.
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The NRC also expressed concern for the effect of settlement on the fuel oil lines under the building. CPC0 stated that re-routing of lines can be readily accomodated if necessary. This matter is also under review.
The NRC Resident Inspector asked for a list of the equipment, with a discussion of the compacting capability and limitations of each, used for compacting the fill for the DG Building from elevation 618 to 628 feet. Bechtel will provide this information.
5.
Program Status Bechtel sumarized the activities completed, in progress, and planned for the future:
JAN 121979 a.
Activities Completed (1) Boring program (2)
Isolation of the electrical duct banks on the north side of the DG Building b.
Activities in Progress (or soon to be initiated)
(1)
Foundation settlement monitoring program (2) Preload instrumentation program (3) Actual preload of the structure and foundatic.,
(4) Filling the cooling pond to maximum elevation (Elevation 627)
(5 > Complete construction of the rest of the DG Building structure c.
Activities Planned (1) After removal of the surcharge, assure contact between footings and soil foundation material (2) Verify uti.11 ties and structure integrity 6.
Project Schedule Bechtel presented the following project schedule infonnation:
Construction is 58% completed as of November 1978 Engineering is 80% complete Structural concrete is 97% complete Fuel load target date is.uvember 1980 Earliest requirement for one diesel generator is January 1980 Current completion date for one diesel generator is Januaiy 1980 Latest date for one diesel generator is June 1980
JAN 121979 Bechtel emphasized that the installed instrumentation will show when the preload surcharge may be removed and therefore the present schedule is somewhat tentative. Most settlement is predicted to occur rapidly as the area is being preloaded and frequent readings will be taken du'.-ing this period and used as a basis for further prtjections. The rate of settlement will decrease thereafter and the total settlement is expected to be reached within a few mcnths.
CPC0 stated that if 'lecessary, temporary diesels could be used during preoperationhi testing prior to fuel loading and that this matter is presently under study.
7.
Response to Open Items in NRC Ir.spection Report Bechtel addressed the open items included in NRC inspection report Nos. 50-329/78-12 and 50-330/78-12.
CPC0 stated that a written response would be sent to I&E Region III to resolve the conflict between the FSAR and site implementing procedures:
a.
Conflict between FSAR Table 2.5-14 and Table 2.5-10 regarding the description of #ill material and what was actually used in the random fill'. Bechtel stated that this conflict was an oversight and that an FSAR amendment would be issued.
The NRC staff stated that any such amendment should address both the previous and the adjusted entries such that the basis for the previous staff review is not obscured in the documentation.
b.
Conflict between FSAR Table 2.5-21 and Bechtel Specification C-210 regarding number of passes for compaction: Bechtel stated that FSAR Table 2.5-21 is for the embankments for the cooling pond dikes.
c.
FSAR Section 3.8.5.5 regarding expected settlement: Bechtel stated that 1/2-inch indicated in the FSAR was a mistake and that the FSAR ould be ar.ided to correct this. mistake, d.
Conflict between FSAR Figure 2.5-47 and project drawing regarding foundation elevation: Bechtel stated the elevations in the FSAR was also a mistake and would be corrected, e.
Conflict in Bechtel Specification C-210 regarding compactive effort: Bechtel stated that Field Change Request C-302 dated 10/31/75 clarified this conflict and permitted the "Bechtel Modified Protector" using 20,000 ft-lbs compactive effort rather than the ASTM standard of 56,000 ft-lbs.
JAN 121979
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f.
Conflict between Dames & Moore recommendation regarding lift thickness of 6 to 8 inches and the Bechtel specification permitting up to 12 inches: Bechtel stated that the greater depth per-mitted by their specification uould not matter because of perfomance qualification tests. However, the NRC was then informed that the test qualifications performed were for Zone 1 clay only, and that no test qualifications on the random fill material using 12 inches was perfomed to qualify such lift thicknesses. Dr. Peck stated that the thicker the layer, the more differences in compaction through the thickness of the layer would occur.
g.
Tolerance of i 2% in moisture content permitted in Bechtel Specification C-210: Bechtel stated that this tolerance is in line with industry practice.
Dr. Peck was asked his view on this i 2% tolerance. He stated that the important question is "t 2% of what material."
Since the material used in the fill was variable, the i 2%
tolerance could cause a problem if the material is not consistent.
h.
Cracks ir the building structure: Bechtel stated that all cracks greater than the ACI 318-71 limit would be identified and repaired after the preload program.
- i. FSAR question 362.2: Bechtel stated that the answer had t :en sent to NRC via FSAR revision 15 in November 1978.
CPC0 stated that the reply to the inspection report is in process, and that the reply will include copies of all data, slides, and drawings presented during this meeting.
In concluding remarks, CPC0 stated its intent to proceed with the preloading program as described during the meeting.
In its closing coments, the NRC staff stated that the proposed solu-tion is at the risk of the applicant and that NRC intends to review and evaluate this matter in accordance with the original compaction requirements as set forth in the commitments in the PSAR, The staff also stated that while attention to remedial action is important, determination of the exact cause is also quite important for verifying the adequacy of the remedial action, assessing the extent of the matter relative to other structures, and in precluding repetition of such matters in the future.
ykny_l>
Darl Hood, Project Manager Light Water Reactors Branch 4 Division of Project Management
Enclosures:
As stated
JAN 121979 consumers Power Company ccs:
Michael 1. Miller, Esq.
Isham, Lincoln & Beale Suite 4200 One First National Plaza Chicago, Illinois 60670 Judd L. Bacon, Esq.
Consumers Power Company 212 West Michigan Avenue Jackson, Michigan 49201 Mr. Paul A. Perry Secretary Consuiners Power Company 212 W. Michigan Avenue Jackson, Michigan 49201 Myron H. Cherry, Esq.
One IBM Plaza Chicago, Illinois 60611 Mary Sindlair 5711 Summerset Orive Midland, Michigan 48640 Frank J. Kelley, Esq.
Attorney General State of Michigan Environmental Protection Division 720 Law Building Lansing, Micnigan 48913 Mr. Windell Marshall Route 10 Midland, Michigan 48640 Mr. S. H. Howell Vice President Consumers Power Company 212 West Michigan Avenue Jackson, Michigan 49201
+4
ENCLOSURE 1 JAN 121979 ATTENDEES DECEMBER 4, 1978 MEETING P. A. Martinez, Bechtel Karl Wiedner, Bechtel
- S. S. Afiff, Bechtel R. B. Peck, Bechtel Consultant
- W. R. Ferris, Bechtel M. O. Rothwell, Bechtel
- D. B. Miller, CPC0 - Project
- J. P. Betts, Bechtel W. L. Barclay, Bechtel
- A. J. Boos, Bechtel G. L. Richardson, Bechtel
- D. E. Horn, CPC0 - QA W. R. Bird, CPC0-QA
- R. M. Wheeler, CPC0 - PM0
- C. A. Hunt, CPC0 - Engineering Services D. E. Sibbald, CPC0 Project John Dunnicliff, Bechtel Consultant
- Austin Marshall, Bechtel - Geotech
- Y. K. Lin, Bechtel - Geotech
- 8. C. McConnel, Gechtel - Geotech
- B. Dhar, Bechtel
- N. Swanberg, Bechtel
- Darl Hood, NRC LPM
- Gene Gallagher, NRC Region III (I&E)
- Daniel Gillen, NRC/NRC Geosciences
- Lyman Hiller, NRC/NRR Geosciences
- Ronald Cook, NRC Resident Inspector
- Present during both the 12/3/78 site tour and the 12/4/78 meeting.
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SUBJECT:
CPCo Mi'dland Plant Units 1 & 2 Diesel Generator Building JAN 121979 Meeting with NRC at Midland DATE:
December 4, 1978 AGENDA I.
Introduction by CPCo II.
History by Bechtel (N. Swanberg) a.
Plant description b.
Settlement monitoring program c.
Brief history of site fill placement d.
Settlement of Category 1 structure Settlement of diesel generator building and pedestals e.
f.
Review settlement data and drawings,(SK-C-620/623) g.
Consultants III.
Soil Exploration by Bechtel (S. Afifi) a.
Soil borings b.
Dutch cone penetrations c.
Laboratory tests d.
Possible causes IV.
Consultant's Recommendation by Dr. R.B. Peck and C.J. Dunnicliff a.
Preload b.
Instrumentation V.
Status report by Bechtel (B.C. McConnell) a.
Activities completed b.
Activities in progress c.
Activities planned for future 1)
Corrective action 2)
FSAR conformance VI.
Schedule by Bechtel (P. Martinez) a.
Overall project b.
Impact on project schedule c.
Schedule for remedial measures
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VII.
Responses to open items in NRC Inspector's report dated 11/17/78 by Bechtel (B. Dhar)
Jgg 1 3 1979 Responses to Gallaghar's concerns:
a.
1)
Conflict between FSAR Table 2.5-14 and Table 2.5-10 regarding fill material description 2)
Conflict between FSAR Table 2.5-21 and Specification C-210 regarding required number of passes for compaction 3)
FSAR Section 3.8.5.5 - expected settlement 4)
Conflict between FSAR Figure 2.5-47 and project drawing regarding icundation elevation 5)
Conflict in Specification C-210 regarding compactive effort in test method 6)
Conflict between consultant's recommendation anc Specification C-210 regarding lift thickness 7)
+ 2% tolerance in moisture content permitted
.in Specification C-210 8)
Cracks in the building structure b.
FSAR Question 362.2 (Section 2.5.4.5.1)
VIII.
Closing Comments by CPCo 9
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