ML20038A941
| ML20038A941 | |
| Person / Time | |
|---|---|
| Site: | Midland |
| Issue date: | 11/13/1981 |
| From: | CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | |
| Shared Package | |
| ML20038A936 | List: |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8111240481 | |
| Download: ML20038A941 (51) | |
Text
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3 DESIGN REPORT FOR THE BORATED WATER STORAGE TANK FOUNDATIONS 2.
CONSUMERS POWER COMPANY MIDLAND PLANT UNITS 1 AND 2 l
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0111240481 8111] f
{DRADOCK 05000329 PDR f
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MIDIMD PLANT UNITS 1 AND 2 DESIGN REPORT FOR THE BORATED WATER STORAGE TANK FOUNDATIONS TABLE OF CONTENTS
1.0 INTRODUCTION
1
2.0 DESCRIPTION
OF EXISTING FOUNDATION STRUCTURE 1
3.0 DEFICIENCY AND CORRECTIVE ACTIONS 2
h.0 APPLICABLE CODES AND STANDARDS 3
5.0 LOADS AND LOADING COMBINATIONS 3
6.0 DESIGN AND ANALYSIS PROCEDURE h
70 ACCE;TANCE CRITERIA 8
8.0 FOUNDATION BEARING PRESSURE 8
9.0 QUALITY ASSURANCE, MATERIALS, QUALITY CONTROL, 9
AND SPECIAL CONSTRUCTION TECHNIQUES 10.0 INSERVICE INSPECTION 9
11.0 INFORMATION TO THE NBC 10 FOOTNOTES 11 REFERENCES 12 APFFNDDIS A
Preliminary Seismic Analysis of the Borated Water Storage Tanks B
NRC letter, RLTedesco to JWCook, September 25, 1981
- FIGURES, 1
Borated Water Storage Tank 2
Foundation Surcharge Program 3
Foundation Modifications, Sheet 1 h
Foundation Modifications, Sheet 2 11
Midlcnd PlEnt Unita 1 c.4d 2 Da3ign Rcport:
Boratnd Wrtar Stornga Tcnk Foundations Table of Contents (continued) 5 Finite Element Model of Foundation 6
Finite Element Model of Subgrade 7
Extrapolation of Future Settlement 8
Predicted Foundation Settlement 9
Long-Term Elastic Moduli of Subgrade 10 Short-Term Elastic Moduli of Subgrade 11 Foundation Settlement From Finite Element Analysis 12 Ring Beam Axial Force Diagram 13 Ring Beam Vertical Shear Force Diagram 14 Ring Beam Vertical Moment Diagram 15 Ring Beam Circumferential Moment Diagram 16 Ring Beam Torsional Moment Diagram 17 Illustration of Interface Shear Connector Design Force 18 Flow Diagram, Formulation of Load Combinations 19 Comparison of Predicted and Calculated Settlements 20 Maximum Design Loads and Capacities of Interface Shear Connectors (Midland Criteria) i 21 Maximum Design Loads and Capacities of Interface Shear Connectors (ACI 349 Criteria)
TABLES 1
Summary of Calculated Loads and Capacities of the New Ring l
Beam (Midland Criteria) 2 Summary of Calculated Loads and Capacities of the New Ring Beam (ACI 349-76 Load Combination as Supplemented by Regulatory Guide 1.142) 3 Summary of Calculated Loads and Capacities of the Valve Pit Members (Midland Criteria) iii r.
Midland Plcnt Unito 1 cnd 2 D: sign Rcport:
Borated Watcr Storege Tank Foundations Table of Contents (continued) 4 Summary of Calculated Loads and Capacities of the Valve Pit Members (ACI 349-76 Load combination as Supplemented by Regulatory Guide 1.142) 5 Summary of Calculated Loads and Capacities of the Foundation Footing (Midland Criteria) 6 Summary of Calculated Loads and Capacities of the Foundation Footing (ACI 349-76 Load Combinations as Supplemented by Regulatory Guide 1.142) 7 Factors of Safety of Borated Water Storage Tank Foundation Against Overturning, Sliding, and Flotation 1
iv
MIDLAND PLANT UNITS 1 AND 2 DESIGN REPORT FOR THE BORATED WATER STORAGE TANK FOUNDATIONS
1.0 INTRODUCTION
Each unit of the Midland plant has a 500,000-gallon, stainless steel borated water storage tank (BWST).
These tanks are 32 feet high and 52 feet in diameter.
The foundations of the BWSTs were constructed between July 1978 and January 1979.
Construction of the tanks was completed in December 1979.
A load test of the soil by filling the tanks with water has been ongoing since October 1980.
A deficiency of the tank foundations was identified on January 29, 1981, and was reported to the NRC under 10 CFR 50.55(e).
Part of the corrective action for the BWST is to modify the tank foundations.
This report describes the analytical work performed on the modified BWST foundations, soil bearing pressure, and settlement predictions, and justifies the effectiveness of the structural modification to the foundatiens.
2.0 DESCRIPTION
OF EXISTING FOUNDATION STRUCTURE The BWST has a flexible, flat bottom.
The tank shell, roof, and part of the water in the tank (above the foundation ring wall) are supported by a reinforced concrete ring wall.
Compacted granular fill lies inside the ring wall and a 6-inch layer of oiled sand is between the tank bottom and the granular fill.
Approximately 25 feet of compacted plant fill lies under the foundation structure and granular fill.
Because the tank bottom is flexible, the vertical pressure due to the weight of the water and the tank bottom is transfered directly to the soil inside the ring wall.
This vertical pressure also causes a lateral pressure which is resisted by the ring wall.
Forty 1-1/2-inch diameter anchor bolts, which are evenly spaced and embedded around the periphery of the foundation ring wall, provide anchorage to the tank for resisting overturning loads caused by externally applied lateral forces.
The ring wall measures 4 feet, 6 inches high and 1 foot, 6 inches wide with footings that are 4 feet wide and 1 foot, 6 inches high.
Each valve pit is 10 feet, 8 inches high and extends 4 feet, 8 inches below the bottom elevation of the ring wall foundation.
The valve pit walls are 1 foot, 6 inches thick, and the top and bottom slabs are 1 foot, 6 inches and 2 feet thick, A depth transition from 6 feet to 10 feet, respectively.
8 inches is located at each ring wall and valve pit intersection to provide a continuous ring wall through each valve pit (see The valve Figure 1 for the tank and foundation cross-section).
pit provides access to the piping connection to the tank and houses the valves for the fill and drain lines.
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Midland Plcnt Units 1 cnd 2 Design R; port:
BoratOd Wetar Storage Tank Foundctions 3.0 DEFICIENCY AND CORRECTIVE ACTIONS The deficiency of the BWST foundation was revealed by a structural analysis which indicated the allowable moment capacity for the dead load and differential settlement load condition was exceeded in several locations in the foundation structure.
A visual inspection at these locations showed cracks in the Units 1 and 2 foundations.
The overstressed condition is attributed to the differential settlement due to nonuniform bearing pressure at the footings between the tank ring wall foundation and the valve pit.
The original design of the foundations did not account for the additional bending induced by this differential settlement.
A three-phase corrective action procedure is to be adopted.
These measures will be performed in the following sequence:
3.1 SURCHARGE A PORTION OF THE VALVE PIT AND ITS SURROUNDING AREA Figure 2 details the surcharge operation.
The surcharge operation will consolidate the fill beneath the valve pit, thereby reducing the amount of expected residual settlement of the valve pit over the 40-year life of the plant.
In addition, by reducing the differential settlement, the surcharging is expected to reduce the ring wall distortion, the existing foundation crack widths, and the tank shell deformations.
NRC approval for this surcharge is acknowledged in R.L. Tedesco's letter to J.W. Cook dated September 25, 1981 (see Appendix B).
3.2 INTEGRALLY CONSTRUCT A REINFORCED RING BEAM AROUND THE EXISTING RING WALL Figures 3 and 4 show the ring beam construction.
The new ring beam is sized to resist all the imposed loading from the tank, including the additional future bending induced by the predicted l
residual differential settlement between the ring wall and the l
valve pit.
Shear connectors transfer the shear force from the l
existing ring wall to the new ring beam.
One end of the shear l
connectors will be installed in the existing ring wall by drilling and grouting.
The other end will be cast in the new ring beam.
All cracks in the existing ring wall that exceed 10 mils will be repaired by pressure grouting to ensure proper shear transfer.
The main reinforcing bars in the new ring beam that terminate at the valve pit are anchored in the roof or base slab of the valve pit by rock anchors.
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Midland Plcnt Unita 1 cnd 2 Design Raport:
CorctId Water Storcgs Tank Foundatior-3.3 RESETTING THE TANK ON THE EXISTING RING WALL TO THE ORIGINAL CONSTRUCTION TOLERANCE f
After ring beam construction is complete, resetting the tank (if required) will be considered as a part of the remedial action for the tank itself.
4.0 APPLICABLE CODES AND STANDARDS Refer to FSAR Subsection 3.8.6.2.
5.0 LOADS AND LOADING COMBINATIONS The modified BWST foundations are designed in accordance with the The loading requirements for Seismic Category I structures.
following loads are applied:
Dead load, which includes weight of concrete, tank, soil a.
supported on the foundation footing, water, and groundwater hydrostatic pressure (D) b.
Live load, which includes roof loads, snow load, and lateral earth pressure (L)
Operating basis earthquake (OBE) load (E)('I c.
d.
Safe shutdown earthquake (SSE) load (E')I')
e.
Wind load of 100-year recurrence (W) f.
Effect of differential settlement (T) g.
Hydrostatic force due to probable maximum flood (el 635'-0") (B)
The above loads are combined as follows for design considerations:
U = 1.4D + 1.7L (1)
U = 1.25 (D + L + E)
(2)
U = 1.25 (D + L + W)
(3)
U = 0.9D + 1.25E (4)
U = 0.9D + 1.25W (5)
U = 1.OD + 1.0L + 1.6E (6) 3
.s F
Midltnd Pltnt Units 1 cnd 2 Design R; port:
Borstod W: tar Storage Tank Foundationc U = 1.0D + 1.0L + 1.0E' (7)
U = 1.0D + 1.0L + 1.0B (8)
U = 1.05D + 1.28L + 1.05T (9)
U = 1.4D + 1.4T (10)
U = 1.0D + 1.0L + 1.0W + 1.0T (11)
U = 1.0D + 1.0L + 1.0E + 1.0T (12) where U = required strength to resist design loads or their related internal moments and forces Load combinations 1 through 8 are the applicable combinations based on Final Safety Analysis Report (FSAR) requirements.
Settlement effects are considered in load combinations 9 through 12.
These combinations were presented in response to Question 26 of the Response to NRC Requests Regarding Plant Fill (Reference 1).
To account for the increase in SSE due to site-specific response spectra, the seismic forces generated by the current FSAR SSE value (0.12g ground acceleration) are increased one and one-half times their value to formulate load combination 7.
6.0 DESIGN AND ANALYSIS PROCEDURE 6.1 COMPUTER MODEL The BWST foundation was analyzed by the finite element method using the Bechtel Structural Analysis Program (BSAP).
Because the tank has a flexible bottom, the water and tank bottom loads above the soil are transferred directly to the soil.
To account for the settlement effect of the soil from this load, the soil subgrade was modeled in the analysis.
The model is divided into two parts:
the foundation structure and the soil subgrade.
These two parts are connected at the common nodal points at the bottom of the foundation and the outside periphery at the top of the valve pit.
6.1.1 Foundation Structure The ring wall was modeled with curved shell elements.
The ring wall footing and the valve pit were modeled with plate elements.
The curved shell and plate elements are thin quadrilateral and/or triangular structural elements that have membrane and bending properties.
The new ring beam was represented by thickening the curved shell elements representing the ring wall and the plate 4
Midlcnd Pltnt Units 1 cnd 2 Deaign R;part:
Borotcd Wstor Storcgo Tcnk Foundations elements representing the affected parts of the valve pit walls.
The eccentricity due to the addition of the new ring beam was neglected in the model but the torsional effect on the new ring beam war considered in the design.
See Figure 5 for the model of the foundation structure.
At the locations where cracks were observed at the ring wall and footing, the thickness of the existing foundation was reduced by 50% to simulate the existence of cracks.
6.1.2 Soil Subgrade The soil subgrade was modeled by brick elements.
The brick element is an eight-node, hexahedron, isatropic solid element that has membrane properties.
The amount of soil considered in the model extended outward to an average of 55 feet beyond the ring wall and valve pit and 85 feet below the top of the ring wall (see Figure 6).
Two sets of elastic moduli were used in the analysis.
One set of elastic moduli was used for long-term loads to include consolidation effects and the other set of elastic moduli was for short-term loads.
Long-term loads are defined as permanent loads (dead load and permanent live load) when differential settlement effects are to be considered.
Short-term loads are defined as all the loads, including dead and live loads, when differential settlement effects are not to be considered in the analysis.
6.1.3 Boundary Conditions Boundary conditions are imposed on the soil elements only.
Along all edges of the vertical boundary, vertical movement is allowed and horizontal movement is restrained.
At the lower boundary, vertical movement is restrained and horizontal movement is allowed.
6.2 SETTLEMENT PREDICTION Future settlement of the BWST foundation was predicted based on l
the data obtained from the full-scale load test of the soil.
By extrapolating the settlement-versus-log-time curve for each I
settlement marker, future settlement can be predicted (see Figure 7 for an example).
Settlement predictions based on the full scale load test of the existing foundation are conservative because the modified foundation will be stiffer and will provide l
more bearing area, thereby resulting in reduced differential settlement.
Additional settlement of the foundation from December 31, 1981, to December 31, 2025, is shown in Figure 8.
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Midicnd Plcnt Units 1 cnd 2 DO2ign R; port:
BorntOd Wnter Storcga Tcnk Foundations 6.3 DETERMINATION OF ELASTIC MODULUS OF SOIL 6.3.1 Long-Term Loads The differential settlement effect on the BWST foundation was considered in the analysis by using a proper set of elastic moduli for the soil subgrade as shown in Figure 9.
The foundation settlement resulting from the finite element analysis using the moduli in Figure 9 is shown in Figure 11.
The differential settlement from the finite element an. lysis is in general more severe than the differential settlement from the settlement prediction (see the comparison shown in Figure 19).
Thus, using the elastic moduli shown in Figure 9 results in a conservative design for the new ring beam.
6.3.2 Short-Term Loads The elastic moduli used for short-term loads are shown in Figure 10.
These values are calculated from the shear moduli used for seismic analysis of the BWST and foundation (see Appendix A).
6.4 ANALYSIS PROCEDURE Applicable loads given in Section 5.0 are applied to two models.
From the results of these loads, 12 design basis combinations are obtained.
The two models are ider tical in every aspect except the elastic moduli used for the soil elements are different.
6.4.1 Long-Term Model The elastic moduli of soil for long-term loads (dead and live l
load) are used, and this allowed the settlement effects to be incorporated.
The application of the dead load and live load to l
the model causes the foundation and the soil model to displace, which induces stresses due to differential settlement in the l
foundation structure.
6.4.2 Short-Term Mod ('
The elastic moduli of soil for short-term loads are used and all the individual loads are applied in the analysis.
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Midlcnd Plcnt Units 1 cnd 2 Design R; port:
Bortt;d WntOr Storago Tank Foundationa 6.4.3 Formulation of Design Load Combinations Load combinations 1 through 8 presented in Section 5.0 are generated from the results obtained by using the short-term model described in Subsection 6.4.2.
Load combinations 9 and 10 are generated from the results obtained by using the long-term model described in Subsection 6.4.1.
For load combinations 11 and 12, the dead load, live load, and differential settlement effect are obtained by using the long-term model, and the wind and operating basis ear.hquake (OBE) effects are obtained by using the short-term model.
Refer to Figure 18 for the flow diagram detailing the formulation of the load combinations.
6.5 DESIGN PROCEDURE 6.5.1 Existing St uctural Components a.
Valve pit:
The entire valve pit structure was evaluated for the controlling load combinations (see Table 3 for the summary of loads).
b.
Footing:
The footing of the existing ring wall is relied on for distributing the design loads to the soil (see Table 5 for the summary of loads).
6.5.2 New Structural Components The foundation ring wall and the new ring beam were treated as a composite section in the analysis.
The stresses from the composite section were designed to be resisted by the new ring beam only.
Samples of the design axial load, shear force, bending moment, and torsional moment diagrams are given in Figures 12 through 16.
Torsional moment due to the eccentricity of the interface shear transferred from the ring wall to the new ring beam was added manually to the design torsional moment obtained from the computer ana3/ sis (see Table 1 for the summary of loads).
6.5.3 Interface Between Existing and New Structural Components The composite section of the ring wall, footing, and new ring beam is supported vertically by the soil.
The net vertical force to be resisted by the composite section is the incremental change in the shear force diagram.
Because the new ring beam is designed to carry all the force, the incremental change in the shear force diagram is the upper bound of the interface shear force to be transmitted to the new ring beam.
At the intersection of the new ring beam and the valve pit walls, the interface shear force includes the full magnitude of the shear 7
Midland Pltnt Units 1 cnd 2 Danign R; port:
Borcted Water Storago Tank Foundations force diagram (see Figure 17).
One-inch diameter bolts with nuts on each end are used to carry the interface forces between the new ring bean and the existing foundation.
The design of the connector is in accordance with Reference 2 (see Figure 20 for design loads).
7.0 ACCEPTANCE CRITERIA The modified BWST foundation is designed to meet the load criteria presented in Section 5.0.
The capacity of the structural components is evaluated in accordance with American Concrete Institute (ACI) 318-71 and found to exceed the design loads.
Tables 1, 3,
and 5 compare design loads to the section capacities.
The capacity of the interface shear connectors is evaluated in accordance with Reference 2 and found to exceed the design loads.
Figure 20 compares the design loads to the connector capacities.
In addition to the strength criteria, the BWST foundation was analyzed and found to satisfy the requirements of FSAR Subsection 3.8.6.3.4 for overturning, sliding, and flotation (see Table 7 for the actual factors of safety).
8.0 FOUNDATION BEARING PRESSURE The results of the finite element analysis indicate all the soil elements immediately beneath the foundation structure are in compression for dead load and live load conditions.
This behavior indicates that the soil and the foundation are displacing in a compatible manner without separation.
The maximum calculated soil pressures are:
a.
2.0 ksf for dead load and live load b.
2.5 ksf for dead load, live load, and OBE c.
3.5 ksf for dead load, live load, and SSE Bearing capacity determination was presented in Attachment 43-1 of the Response to NRC Request: Regarding Plant Fill, Question 43 (Reference 1).
The bearing capacity was also evaluated using the soil samples obtained by Woodward-Clyde Consultant * (WCC).
A summary of the factors of safety and ultimate bearing capacity from Reference 1 and WCC test data based on undrained shear strength are given below:
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Midicnd Plcnt Unita 1 cnd 2 Design Rgport:
Borntcd Water Storaga Tank Foundations Ultimate Bearing Factor of Safety Against Capacity Ultimate Bearing Capacity (ksf), D + L( 2 )
D + L + E'(33 Reference 1 12.0 6.5 2.8 WCC Test Data 15.1 8.2 3.4 (average for two borings)
These factors of safety satisfy the requirements of FSAR Subsection 2.5.4.10.1 which are 3.0 and 2.0, respectively, for D + L and D + L + E'.
9.0 QUALITY ASSURANCE, MATERIALS, QUALITY CONTROL, AND SPECIAL CONSTRUCTION TECHNIQUES 1ha new ring beam, including its connection to the existing foundation structure, is constructed in compliance with the Midland Project Quality Assurance Program.
Refer to FSAR Subsection 3.8.4.6 for other requirements.
10.0 INSERVICE INSPECTION After the new ring beam is constructed, two observation pits will
)
be provided for each BWST foundation at the high stress locations (see Figure 2 for locations and size of the observation pits).
The ring beams will be monitored monthly for cracks under the service condition (complete or partially filled tank) for 6 months.
Any observed cracks over 10 mils will be evaluated.
BWST foundation settlement will also be monitored as part of the foundation survey.
Foundations are surveyed at 60-day intervals during construction and at 90-day intervals for the first year of plant operation.
Subsequent survey frequency will be established after evaluating the data taken during the first year of plant operation.
As a minimum, the tank foundation would be monitored annually for the next 5 years of operation and at 5-year intervals thereafter.
The allowable total settlement will be based on the settlement prediction (Figure 8).
The allowable for differential settlement will be based on the results of the finite element analysis (Figure 11).
These allowables will be provided as part of the technical specifications in the FSAR.
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Midltnd Plcnt Units 1 cnd 2 De ign R; port:
BoratOd Water Storage Tank Foundations t
11.0 INFORMATION TO THE NRC The new ring beam interface shear connectors and the existing parts of the BWST foundation are analyzed and found to be capable of withstanding the load combinations of ACI 349-76 as sapplemented by Regulatory Guide 1.142 (see Tables 2, 4, and 6, and Figure 21 for a comparison of design loads to the section capacities).
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Midland Plant Unita 1 nnd 2 Design R;p3rt:
BoretCd Wntor Storego Tank Foundations FOOTNOTES
('3For a discussion of the seismic analysis'and seismic loads, refer to Appendix A of this report.
1202.5 ksf was used in the factor of safety calculation.
1245.0 ksf was used in the factor of safety calculation.
i 11
.~,..:.- -.
+.
Midlcnd Plcnt Units 1 cnd 2 Design Rtport:
Borctcd Wntor Storage Tank Foundations REFERENCES 1.
Consumers Power Company, Response to NRC Requests Regarding Plant Fill, Docket 50-329, 50-330 2.
Proposed Addition to Code Requirements for Nuclear Safety Related Concrete Structures (ACI 349-76), ACI Journal, August 1978 i
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Midland Plant Units 1 and 2 Design Report: Borated Unter Storage Tank Foundations APPENDIX A PRELIMINARY SEISMIC ANALYSIS OF THE BORATED WATER STORAGE TANK
1.0 DESCRIPTION
The borated water storage tank (BWST) is a flat bottomed, stainless steel tank with a 26-foot radius and a height of 32 feet. The tenk vall is 3/8-inch thick for the botton 8 feet and 1/h-inch thick fo* the remainder of its height. The roof is a 0.3-inch thick done segnent with a 52-foot radius and a height of 6 feet, 9-3/8 inches. The tank bottom is 1/h-inch thick. Both the tank and roof are insulated. The tank is set on a ring foundation at-tached to a val.e pit.
2.0 PROCEDURE The tank, foundation, and water are modeled as a multi-degree-of-freedom system that is solved by a response spectrum method in accordance with Section 3.7 of the ~ Final Safety Analysis Report (FSAR). The model is based on infor-mation contained in TID-702h (Reference 1), except the coefficient of mass for sloshing water is taken from American Society of Civil Engineers Publication 58 (References 6 and T).
The analysis considers all possible combinations of soil shear nodulus G (0.TG + 50%) with or without entrapped foundation soil, and the IBP(l) or E35(2) model of sloshing and rigid water. The ground ac-celerations are baced on FSAR Figure 3.7-1.
Any mode with a damping ratio greater than 10% uses accelerations corresponding to a damping ratio of 10%.
The analysis accounts for both tank flexibility and soil-structure interaction (base translation and rocking). The final moments and shears are calculated using Reference 1 techniques with the addition of the soil-structure interaction.
This analysis is done to find forces and moments on the anchor bolts and founda-tion.
No time Listory is used and no spectra curves are produced.
3.0 ASS wPTIONS USED IN THE ANALYSIS Torsional effects are negligible (i.e., eccentricity due to the valve a.
pit has a negligible effect).
b.
The factor for calculating the sloshing water mass is 0.h6, as pro-vided in References 6 and 7, and not the 0.318 factor shown in Ref-erence 1.
(1)IBF - Including bottom pressure (includes the effect of dynamic fluid pressure on the tank bottom)
(2)EBP - Excluding bottom pressure (excludec the effect of dynamic fluid pressure on the tank botton)
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Midl&nd.PIEnt' Unit 0'i End 2 DeDign'R; ports Borated Water Storago Tank Foundations Appendix A c.
All soil springs and dampers (horizontal, verti-cal, and rocking) are reduced to 88% of the cal-culated value to account for tiie ring foundation instead of the solid circular base (see Reference 8).
d.
The bate mass is concentrated at a depth _ equal to one-half the depth of the foundation.
The analysis was performed with the concrete ring e.
that was added to the foundation assumed to be 30 inches thick.
Later, the ring size was reduced to 24 inches thick.
This change was evaluated and the effect on the analysis is negligible.
4.0 MATERIAL DAMPING A material damping value is input for each dynamic degree of freedom (DDOF).
Soil dampings are calculated separately.
The first DDOF is sloshing water, for which 0.5% damping is used.
This is the damping used in similar examples shown in Reference 1, and it is conservative.
The second DDOF is rigid water, the tank, and some foundation weight whose displacement is associated with beam bending of the tank.
The damping associated with this DDOF was it, which is the damping for welded steel plate assemblies (see FSAR Appendix 3A, response to Regulatory Guide 1.61).
5.0 SOIL SPRINGS AND DAMPERS The dynamic soil springs and dampers for the soil-structure interaction analysis of the BWST which is founded on fill, were developed using equations from BC-TOP-4-A (Reference 2),
and soil parameters based on the following information.
~4 5.1 Soil properties at low soil strains (10
- 4) were estab-lished by using a weighted average of the shear modulus values (G ) of the material below the structure to a depth equS1 to the diameter of the foundation.
Soil properties were based on Dr. Wood's site shear wave
<elocity tests for the fill (Reference 5) and the Dames
& Moore evaluation for the natural material [See FSAR Subsection 2.5.4.7.2 (Reference 4)].
The unit weight and Poisson's ratio for fill material were taken as 120 pcf and 0.40, respectively.
These values were averaged with the natural material values as described above to produce composite values.
A-2
'Midlr.nd P'lCnt Unito 1 cnd 2 Decign R3 ports Boratcd Wnter Stor:go Tank Foundations App;ndix A 5.2 The composite soil shear modulus G (calculated as described in Section 5.1) was degraded to 70% to account for the effect of larger shear strain during seismic events, as presented a FSAR Subsection 2.5.4.7 (0.7G
= 1,510 ksf, E =,4,380 ksf).
s To ensure a conservative analysis, the model was analyzed with soil shear modulus values of 0.70G, +50%.
This proce-dure accounted for both the range of soll strains postulated for the site and for the variation of fill material.
6.0 OBSERVATIONS The maximum acceleration comes from the case using entrapped soil, the shear modulus of 0.7G and the IBP model.
The dynamic response in both the IBh,and EBP cases were soil-dominated, and, therefore, there was very little difference in the frequencies of the corresponding modes in each case and virtually no difference in the final accelerations of the masses.
This seismic analysis was performed to generate seismic forces for calculating foundation stresses, overturning, and sliding.
This seismic analysis is not applicable for calcu-lating stresses in the tank.
The IBP and EBP models are summarized in the following pages.
All results are for operating basis earthquake (OBE).
To obtain safe shutdown earthquake results, multiply OBE by 2.
A-3
Midlcnd Plcnt Unito 1 End 2 Deaign R3portt Borntsd Wstar Storaga Tank Foundation 0 Appendix A REFERENCES 1.
U.S. Atomic Energy Commission, Nuclear Reactors and Earthquakes, (TID-7024), Chapter 6, August 1963 2.
Bechtel Power Corporation, Seismic Analyses of Scruc-tures and Equipment for Nuclear Power Plants, Revision 3, November 1974 (BC-TOP-4-A) 3.
Bechtel Associates Professional Corporation, Civil Design Criteria, Str.ndard 7220-C-501, Rev 11 4.
Consumers Power Company, Midland Plant Units 1 and 2, Final Safety Analysis Report, Subsection 2.5.4.7.2 5.
Letter, Dr.
R.P. Woods to Dr.
S.S. Afifi, 2/22/80 10 CFR 50.54(f), Vol 6, TAB 126 6.
ASCE Publication 58, Structural Analysis and Design of Nuclear Plant Facilities, 1980 7.
A.S. Veletsos and J.Y. Yang, " Dynamics of Fixed-Base Liquid-Storage Tanks," U.S.-Japan Seminar on Earthquake Engineering Restraints with Emphasis on Lifeline Systems, November 1976, Tokyo, Japan 8.
H.L. Wong, " Dynamic Soil-Structure Interaction,"
Report No. EERL 75-01, Earthquake Engineering Research Laboratory, California Institute of Technology, 1975 A-4
Midicnd Plcnt Unito 1 ond-2 Design RIports B;ratGd W2tsr Storegs Tank Fcundations Appendix A TABLE 1 HORIZONTAL MODEL Weight With Elevation (
Elevation Entrapped Mass Point Node EBP Case (ft)
IBP Case (ft)I ' Soil (kips) 1 1
20.5 23.5 1.5E3 2
3 12.0 21.4 2.8E3 3
6
-3,0
-3.0 2.7E3 4(3) 6
-3.0
-3.0 5.0E5 III EBP = excluding bottom pressure (This case is used to calculate anchor bolt loads for the tank.)
(2)IBP = including bottom prescure (This case is used to calculate overturning moment and foundation loads.)
Mass 4 represents rotational weight moment of inertia (Ig) at 4
base in ksf.
Midland Plcnt Unito 1 End 2 Decign R port Borated Wcter Storege Tcnk Foundationc Appendix A TABLE 2 HORIZONTAL MODEL - MEMBER PROPERTIES (1)
(2)
Member A(ft )
Ag(ft )
4)'
E(ksf)I4)
G(ksf)(5) y 1
3.4 1.8 1.2E3 4.2E6 1.6E6 2
3.4 1.8 1.2E3 4.2E6 1.6E6 3
5.1 2.7 1.2E3 4.2E6 1.6E6 4
685.0(6) 363.3 2.6ES 5.2E5 2.lES IIIA = cross-sectional area (2)Ag = effective shear area (3)I = moment of inertia (4)E = elastic modulus (5)G
= shear modulus (6) Shear area used here conservatively includes only the con-crete.
No contribution from the entrapped soil was inclu-ded because it was not considered cignificant.
Midland Plcnt Unito 1 cnd 2 DeDign R; port:
Cor2tsd Water Storega Tank Foundations Appendix A TABLE 3 HORIZONTAL MODEL - SOIL SPRINGS AND DAMPERS IBP WITH ENTRAPPED SOIL fad C
CX(K sec/ft)
Gg(ksf)
KX(kips /ft)
Kg,( rad /f t )
0.7G 2.0E5 1.6E8 5.2E3 1.7E6 Notes:
All springs and dampers were reduced to 88% of calculated 1.
value to account for the foundation being a ring and not a disk.
The reduced values are shown above.
Entrapped soil is soil contained inside the foundation 2.
ring.
= 1,510 ksf) g = soil shear modulus (0.7G 3.
G s
X = horizontal translational spring 4.
K 5.
K4 = rocking spring 6.
C
= horizontal damper X
7.
C$ = rocking damper i
8.
All values shown are from the controlling case.
l
Midicnd Plcnt Unito 1 cnd 2 DeGign R; ports Boratsd Water Storcg Tank Found2tiona Appandix A TABLE 4 RESULTS - HORIZONTAL OBE EARTHQUAKE Modal Modal Frequency Damping (cps)
(%)
0.24 0.5 4.06 10 9.66 10 20.89
1.7 Notes
1.
Maximum shear et tank foundation interface = 382 k Maximum shear at bottom of foundation = 555 k 2.
3.
Maximum moment on tank at tank foundation interface =
4,891 ft-k (for use in anchor bolt calculations)
Maximum overturning moment at bottom of foundation =
4.
11,061 f t-k (of which 3,359 f t-k is applied directly to soil) f
- ""'^ -
~-ev<,wp--w,-
Midicnd Plcnt Unita 1 cnd 2 Decign R2 ports Boroted Wator Storcge Tank Foundctions Appendix A
, TABLE 5
/ERTU, AL SEISMIC MODEL M
KZ M = 5,617 kips
= mass of tank, water, 9
and foundation The water in the tank is supported directly on the soil and the tank itself is very stiff.
Therefore, it can be modeled as a single-degree-of-freedom model with a soil spring and damper.
Three cases of G were run:
0.7G, 0.7G + 50%,
g 0.7G - 50%.
Only the controlling case is shown below.
Vertical Model - Soil Springs and Dampers Gs(ksf)
K[(kips i
kip see Z
ft j Z(
ft
)
0.7G-50%
1.4E5 7.6E3 Notes:
1.
All springs and dampers were reduced to 88% of their calculated value to account for the foundation being a ring and not a disk.
The reduced values are shown above (based on the lower bound values of G).
2.
Gg = soil modulus 3.
K
= vertical translational spring g
4.
C
= vertical damper g
Results - Operating Basis Earthquake The frequency is 4.53 cps; damping is 10%.
The maximum vertical seismic force is 395 kips.
The increase in hydro-static head due to a vertical earthquake load condition is 7.0%.
.n
SEISMIC ANALYSIS OF THE BWST HORIZONTAL COMPUTER MODEL MEMBER SP1 1
1/4" TANK 2
1/4" TANK 1
3 3/8" TAh1 4
CONCRETE FOUNDATION NODE OBJECT 2
1*
SLOSHING WATER 2
ATIACEMENT POINT FOR SLOSHING WATER 4
3*
RIGID WATER & TANK 4
JUNCTION 1/4" & 3/8" TANK 3
5 JUNCTION 3/8" TANK &
FOUNDATION 6*
FOUNDATION C5 MASS NODE SP1 - SPRING PICKED TO 4
GIVE CORRECT FREQUENCY TO SLOSHING WATER l
SP2 - SOIL SPRINGS Y
MASS NODE p
W//H4 CONSUMERS POWER COMPANY MIDLAND PLANT UNITS 1 & 2 swsT SEISMIC MODEL l
l FIGURE A-1
l Q, BORATED WATER TANK t
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NOTES UNIT 2 DEWATEmmG START'D ON Sitof00 CONSUIKR$ POWER CouPANY_
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O PREDICTED SETTLEMENT OF SETTLEMENT MARKERS FROM 12/31/1981 TO 12/31/2025
======== DEVELOPED VIEW OF RING FOUNDATION PROFILE CONSUMERS POWER COMPANY
====== DEVELOPED VIEW OF VALVE PIT PROFILE MIDLAND PLANT UNITS 1 & 2 BORATED WATER STORAGE NOTE: FOUNDATION PROFILE IS BASED ON BEST TANK FOUNDATION ESTIMATE OF PREDICTED MARKER SETTLEMENT PREDICTED FOUNDATION SETTLEM_E.NT FIGURE 8 L 1834-14
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- DEVELOPED VIEW OF RING FOUNDATION PROFILE CONSUMERS POWER COMPANY
== = DEVELOPED VIEW OF VALVE t iT PROFILE
?
j BORATED WATER STORAGE TANK FOUNDATION FOUNDATION SETTLEMENTFROM FINITE ELEMENT ANALYSIS FIGURE 11
< 1834-15
TOTAL AXIAL FORCE DIAGRAM - LOAD CASE 10 i
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TOTAL VERTICAL SHEAR DIAGRAM - LOAD CASE 10 j
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-100.0 CONSUMERS POWER COMPANY 2m.0 MIDLAND PLANT UNITS I & 2 0
5 10 15 20 25 30 35 40 BORATED WATER STORAGE TANK GRID LOCATION FOUNDATION ILLUSTRATION OFINTERFACE SHEAR CONNECTOR DESIGN FORCE FIGURE 17 I
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.12 CONSUMERS POWER COMPANY MIDLAND PLANT UNITS 1 & 2 j
BORATED WATER STORAGE TANK FOUNDATION COMPARISON OF PREDICTED AND CALCULATED SETTLEMENTS FIGURE 19
'834 16
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60.0 CAPACITY ENVELOPE 7
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10 15 20 25 30 35 40 CONSUMERS POWER COMPANY MIDLAND PLANT UNITS 1 & 2 BWST FOUNDATION MAXIMUM DESIGN LOADS AND CAPACITIES OF INTERFACE SHEAR CONNECTORS (MIDLAND CRITERIA)
FIGURE 20
KE Y PL AN CAPACITY ENVELOPE j
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5 20.0 10.0 0.0 5
10 15 20 25 30 35 40 GRID LOCATION CONSUMERS POWER COMPANY MIDLAND PLANT UNITS 1 & 2 BORATED WATER STORAGE TANK MAXIMUM DESIGN LOADS AND CAPACITIES OF INTERFACE SHEAR CONNECTORS (ACI 349 CRITERIA)
FIGv.:E 21
Midland Plant Units 1 and 2 Design Report: Borated Watar Storage Tank Foundations TABLE 1
SUMMARY
OF CALCULATED LOADS AND CAPACITIES OF Tile NEW PING HEAM (MIDLAND CRITERI A)
Axial and Flexural Axial, Shear, and Torsion Interaction Interaction Calculated t
Calculated Loadizi Load as Load Grid Axial Moment Load Grid Axial Shear Category Combinat ionl Number Tension Moment Capacityt 2,3 8 Combinationt'l Number Tension Shear TorsioniSI Capacitys t,4 p
~
Region A Reg ion B Region C Region D Region E IURefet to Sect ion 5.0 of the design Report for the Borated Water Storage Tank Foundations for load combinations (81 Axial and shear are measured in kips: moment and torsion are measured in ft-kips 83' Interaction capacities at calculated axial load I*' Interaction capacities at calculated axial load and torsion 85' Including torsion due to eccentricity of the interface shear force o
Midland Plant Units 1 and 2 Destyn Report: porated water Storage Tank Foundations i
TABLE 2
SUMMARY
OF CALCULATED LOADS AND CAPACITIES OF THE NEW RING BEAM 349-76 LOAD COMDINATIONS AS SUPPLEMENTED BY REGULATORY GUIDE 1.142)
(ACI Axial and Flexural Axial, Shear, and Torsion Interaction Inte ract ion Calculated Calculated LoadI23 8#'
Load Load Grid Axial Moment Load Grid Axial Shear ist_ Capacityf 2*
- l tr 38 Combin_aQod' Ntsaber Tension Shear Torsion 3
Category combinationtU Number Tension Moment Capacity Reg ion.*.
Region B Region C Region D Region E 8H ontrolling ACI 349-76 load combinations are:
C i
A.
U = 1.4D + 1.4T + 1.4F + 1. 7 L + 1.7H + 1.9E B.
U = 0.9D + G.9T + 1.4F + 1.711 + 1.9E where D = dead load L = live load F = hydrostatic pressure f rom groundwater T = differential settlement H=
lateral earth pressure E = operating basis earthquake 830 Axial and shear are in kips: moment and torsion are measured in f t-kips IHIntesaction capacities at calculated axial load
(*l nteraction capacities at calculated axial load and torsion I
85' Including torsion due to eccentricity of the interface shear force
Mid1Cnd Plant Units 1 and 2 Design Report: Borated Water Storage Tank Foundations i
TABLE 3
SUMMARY
OF CALCULATED LOADS AND CAPACITIES OF TIIE VALVE PIT MEMBERS (MIDLAND CRITERIA)
Axial and Flexural Interactionl88 Shearial Calculated Load in-Plane Transverse Axial Moment Category Combinations' Calculated capacity Calculated Capacity Tension Moment Capacity 838 t
n' Exterior walls Interior wall (ring wall)
Roof slab'O l
N-S direction E-W direction Floor slabt'O N-S direction E-W direction 8' Refer to Section 5.0 of the Design Report for the Borated Water Storage Tank Fbundations for load combinations (2' Units are in kips and feet.
8381nteraction capacity at calculated axial load l 'UForces shown are per linear foot of slab.
l'hBased on maximum of all load combinations e
Midland Plant Units 1 (nd 2 0
Design Report: Borsted Water Storage Tank Foundations TABLE _4
SUMMARY
OF CALCULATED LOADS AND CAPACITIES OF THE VALVE PIT MEMBERS 349-76 LOAD COMBINATIONS AS SUPPLEMENTED BY REGULATORY CUIDE 1.142)
(ACI Axial and Flexural Inte raction(38
--- Calculated Shear:23 Moment Axial In-Plane Transverse Combinations 'I Calculated Capacity Calculated capacity Tension Moment Capacityl33 Load 8
I Category Exterior walls Interior wall (ring wall)
Roof slabl*l N-S direction E-W direction Floor slab (*8 N-S direction E-w direction l'icontrolling ACI 349-76 load combination ist A.
U= 1.4D + 1.4T + 1.4F + 1.7L + 1. 711 + 1.9E where D = dead load L = live load F = hydrostatic pressure from groundwater T = differential settlement H = lateral earth pressure E = operating basis earthquake
"' Units are in kips and feet.
lnteraction capacity at calculated axial load "I
(*' Forces shown are per linear foot.
l Based on maximum of all load corbinations
a Midland Plant Unito 1 and 2 Dasign Rtport s' Borsted Water Stortga Tank Foundations TABLE 5
SUMMARY
OF CALCULATED LOADS AND CAPACITIES OF Tile FOUNDATION FOOTING (MIDLAND CRITERIA)
Load Type of Load Combinatio nt 'l Calculated Load (2)
Capaci ty(21 Moment Axial Tension Shear (SI Refer to Section 5.0 of the Design Report for the Borated Water Storage Tank Foundations (2) Units are in kips and feet per linear foot of footing
~
r s
Midlcnd Plant Units 1 and 2 Design Report:
Borated Water Storage Tank Foundations TABLE 6
SUMMARY
OF CALCULATED LOADS AND CAPACITIES OF Ti!E FOUNDATION FOOTING (ACI 349-76 LOAD COMBINATIONS AS SUPPLEMENTED BY REGULATORY GUIDE 1.142)
Load t2)
Capacityl2)
U8 Calculated Load Type of Load Combination Moment Axial Tension Shear HIControlling ACI 349-76 load combination is:
A.
U = 1.4D + 1.4T + 1.4F + 1.7L + 1.7H + 1.9E where D = dead load L = live load F = hydrostatic pressure from groundwater T = differential settlement H = lateral earth pressure E = operating basis earthquake (2 Units are in kips and feet per linear foot of footing.
e
_~
Midland Plcnt Units 1 and 2 Design Raport Boroted W tor Storage Tcnk Foundations TABLE 7 FACTORS OF SAFETY OF BORATED WATER STORAGE TANK FOUNDATION AGAINST OVERTURNING, SLIDING, AND FLOTATION Factor of Safety Load Combination Required
, Actual Overturning D+L+E 1.5 6.64 D + L + E' l.1 2.92 Sliding D+L+E 1.5 6.88 D + L + E' l.1 2.21 Flotation D+B 1.1 1.40-i l
l l
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[/
UNITED STATES
^
' t, NUCLEAR REGULATORY COMMISSION j
)
g WASHINGTON, D. C. 20555 i
i N '.... /
SEo 2 o' 1981 Docket Nos. 50-329 OM, OL and 50-330 OM, OL Mr. J. W. Cook Vice President Consumers Power Company 1945 West Parnall Read Jackson, Michigan 49201
Dear Mr. Cook,
Subject:
Staff Concurrence on Surcharging of Valve Pits for Borated Water Storage Tank Foundations References : (1) Interim 50.55(e) Reports 81-03 dated February 20, 1981, April 3,1981, June 12,1981, June 26,1981 July 21,1981 and August 28, 1981 (2) Structural Design Audit by NRC Staff of Midland Plant, April 20-24,1981, AnnArbor, Michigan (3) Meetings of May 4-6, 1981, to discuss Soils Remediation, Bethesda, Maryland (4) Meeting of August 25, 1981, Midland, Michigan (5) Telephone conference on July 30, 1981, August 12 & 14, 1981, September 10 & 11, 1981 By several interim 50.55(e) reports, meetings and telephone conversations (Reference 1-5), you have informed us of the status of the cracks in the concrete foundations of the Borated Water Storage Tanks (BWST) for Midland Plant, Units 1 and 2 and your preliminary plans for remediation. Your plans for remediation include, in part, surcharging a portion of the BWST valve pits and the surrounding area in order to consolidate the fill beneath the pits, reduce residual settlement during plant life, reduce distortion of the ring wall foundation, partially close existing cracks, and reduce tank shell deformation. As noted in Mr. J. Keppler's letter of July 13, 1981, you have agreed that the surcharging would not begin until conferences with the NRR staff were completed. Your letter of August 28, 1981, states your belief that resolution of NRC concerns has been achieved and requests NRR concurrence of the proposed surcharge program.
Your plans call for daily visual inspection of cracks in the BWST ring walls and valve pits during the surcharge period. You have also committed to stop further loading if a maximum 1/2-inch settlement is reached prior to full surcharge loading to provide for engineering evaluations. We find these plans to be acceptable, but not sufficient. Our approval recognizes your adoption j
of two further conditions:
h j
l
...~.
C J. W. Cook :
1.
You state that, while it is not anticipated that existing cracks will widen or that significant new cracks will form, any new or existing cracks in excess of 10 mils during the surcharge program will be monitored and the results reported to the NRC upon removal of the surcharge. The absence of any immediate actions to assure that cracks approaching acceptable limits during the program will be terminated in a timely manner was unacceptable to the NRC staff. You, therefore, have also committed that in the event that the monitoring program should indicate a crack reaching or exceeding 16 mils, then the last increment cf surcharge which was added prior to start of crack growth will be removed ininediately and any further surcharge addition will be prohibited pending engineering evaluation and further NRC staff concurrence. This, of course, excludes' the existing 20 mil crack already known to exist at the ring-pit interface of Unit 1.
2.
You state that propagation of a crack from the tension zone of the wall is not expected to occur because the ultimate moment capacity of the valve pit wall is governed by the yielding of the reinforcement steel. Your expected limit of new crack propagation is 18 inches from the top of the valve pit roof slab. However, your plans provide no immediate action in the event a i
crack should propagate above this 18 inch value. You, therefore, have committed that in the event a crack should propagate to within 18 inches from the top of the valve pit roof slab, then the last increment of surcharge which was added prior to start of crack propagation will be removed immediately and any further surcharge addition will be prohibited pending engineering evaluation and further NRC staff concurrence.
On the basis the above two additional committments, the NRC staff concurs with your plans to commence surcharging of the BWST valve pits.
Our concurrence to begin this activity does not address the adequacy of the i
proposed remedy to achieve its intended purpose nor does it have any effect on any other remedial action that may be required as a result of the staff's OL review or as a result of the OL-0M hearing. Rather, the staff's review at this point has been limited to assurance that proper precautions are or will be in place to preclude potential detrimental effects due to surcharging.
t Sincerely, Robert L. Tedesco, Assistant Director for Licensing Divisicn of Licensing cc: See next page
4 MIDLAND Mr. J. W. Cook Vice President Consumers Power Company 1945 West Parnall Road Jackson, Michigan 49201 cc: Michael I. Miller, Esq.
Mr. Don van Farrowe, Chief Ronald G. Zamarin, Esq.
Division of Radiological Health Alan S. Farnell, Esq.
Department of Public Health Isham, Lincoln & Beale P.O. Box 33035 Suite 4200 Lansing, Michigan 48909 1 First National Plaza Chicago, Illinois 60603 William J. Scanlon Esq.
2034 Pauline Boulevard James E. Brunner, Esq.
Ann Arbor, Michigan 48103 Consumers Power Company 212 West Michigan Avenue U.S. Nuclear Regulatory Comission Jackson, Michigan 49201 Resident Inspectors Office Route 7 Myron M. Cherry, Esq.
Midland, Michigan 48640 1 IBM Plaza Chicago,11'inois 60611 Ms. Barbara Stamiris 5795 N. River Ms. Mary Sinclair Freeland, Michigan 48623 5711 Summerset Drive Midland, Michigan 48640 Mr. Paul A. Perry, Secretary Consumers Power Company Stewart H. Freeman 212 W. Michigan Avenue Assistant Attorney General Jackson, Michigan 49201 State of Michigan Environmental Protection Division Mr. Walt Apley 720 Law Building c/o Mr. Max Clausen Lansing, Michigan 48913 Battelle Pacific North West Labs (PNWL)
Battelle Blvd.
Mr. Wendell Marshall SIGMA IV Building Route 10 Richland, Washington 99352 Midland, Michigan 48640 Mr. Steve Gadler i
l 2120 Carter Avenue St. Paul, Minnesota 55108 l
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Mr. J. W. Cook.
cc: Commander, Naval Surface Weapons Center ATTN:
P. C. Huang White Oak Silver Spring, Maryland 20910 Mr. L. J. Auge, Manager Facility Design Engineering Energy Technology Engineering Center P.O. Box 1449 Canoga Park, California 91304 Mr. William Lawhead U.S. Corps of Engineers NCEED - T 7th Floor 477 Michigan Avenue Detroit, Michigan 48226 Charles Bechhoefer, Esq.
Atomic Safety & Licensing Board U.S. Nuclear Regulatory Commission Washington, D. C.
20555 Mr. Ralph S. Decker Atomic Safety & Licensing Board U.S. Nuclear Regulatory Commission Washington, D. C.
20555 Dr. Frederich P. Cowan Apt. B-125 6125 N. Verde Trail Boca Raton, Florida 33433 i
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