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Page 1 of 16 DSAR-5.11 Structures Structures Other Than Containment Rev 1 Safety Classification: Usage Level:
Safety Information Change No.: EC 69765 Reason for Change: This section is updated to incorporate Amendment No.
293 (NRC-17-065).
Preparer: T. Knuth Fort Calhoun Station
DSAR-5.11 Information Use Page 2 of 16 Structures Other Than Containment Rev. 1 Table of Contents 5.11 Structures Other Than Containment .......................................................................... 4 5.11.1 Classification of Structures......................................................................... 4 5.11.2 Description of Class I Structures ................................................................ 4 5.11.3 Design Criteria - Class I Structures ............................................................ 5 5.11.4 Design of Structures - Class II ................................................................. 15 5.11.5 Visual Weld Acceptance Criteria .............................................................. 16
DSAR-5.11 Information Use Page 3 of 16 Structures Other Than Containment Rev. 1 List of Figures The following figures are controlled drawings and can be viewed and printed from the listed aperture card.
Figure No. Title Aperture Card 5.11-1 Section Through Engineered Safeguards Equipment Room 36534
DSAR-5.11 Information Use Page 4 of 16 Structures Other Than Containment Rev. 1 5.11 Structures Other Than Containment 5.11.1 Classification of Structures Structures are classified into two categories: Class I and Class II. As described in Appendix F, Class I structures include the auxiliary building (including the control room, spent fuel pool, refueling water storage tank, and emergency diesel-generator rooms), and the intake structure up to 1007.5.
DSAR Section 5.11 describes the auxiliary building and the intake structure.
5.11.2 Description of Class I Structures The auxiliary building is a Class I structure and is located immediately adjacent to the containment structure.
The foundation mat for the auxiliary building and the containment structure is an integral unit supported on piles driven to bedrock. The piling type and design criteria are presented in Section 5.7 (archived).
The auxiliary building is a multi-floored structure of reinforced concrete construction. The building was designed to provide suitable tornado and earthquake protection for the Class 1 equipment and components contained therein. The criteria for this design are given in Section 5.11.3.
In the event of water accumulating on the floor of Room 81, certain modifications have been made to ensure that water will not pass through the floor of Room 81 around piping, cable trays, conduit and ventilation ductwork into the switchgear area and electrical penetration area on the floor below.
Piping that penetrates the floor have had seals installed. Some are flexible where required by movement of the pipe. Cable trays are surrounded by water-tight four-sided enclosures of steel plate embedded in the floor opening extending at least two feet above the floor and the openings sealed.
All ventilation ductwork which formerly passed through the floor of Room 81 was rerouted so that it no longer penetrates the floor openings which have been sealed. The seismic gap between the Containment building and the Auxiliary building as well as conduit floor penetrations have been sealed per EC 62082.
The masonry walls in the area of safety-related equipment have been reinforced to provide protection for Class 1 equipment and components nearby.
DSAR-5.11 Information Use Page 5 of 16 Structures Other Than Containment Rev. 1 The intake structure is a multi-floored reinforced concrete structure supported by a mat foundation on steel pipe piles driven to bedrock. Major systems and components, both critical quality element (CQE) and non-CQE, are housed within this structure in designated rooms. The building was designed to provide the structural support and environmental protection necessary to ensure the functional integrity of the CQE systems and components under all operational and environmental conditions is maintained. The criteria for this design are given in Section 5.11.3.
5.11.3 Design Criteria - Class I Structures Class I structures were designed to ensure that their functional integrity under the most extreme environmental loadings, such as tornado or maximum hypothetical earthquake, will not be impaired.
Loading
- a. Dead Load (D)
Dead loads included the weight of the structure and other items permanently affixed to it such as equipment, non-structural toppings, partitions, cables, pipes and ducts.
Dead loads also include interior hydrostatic fluid loads which are known and controllable. This type of loading is often sustained over time.
- b. Live Load (L)
Live loads included floor loadings of a magnitude commensurate with their intended use, ice and snow loads on roofs, and impact loads such as may be produced by switchgear, cranes, railroad and equipment handling. Design live loads, with the exception of snow and ice loads, were generally based on temporary or transient loads resulting from the disassembly or replacement of equipment for maintenance purposes.
Except for the containment, Class I structures were basically of reinforced concrete box-type construction with internal bracing provided by the vertical concrete interior walls and the horizontal floor slabs. In general, the beams and girders of these structures do not contribute significant lateral shear resistance for the structures. Therefore, in most instances, structural elements basically stressed by the floor live loads will not be stressed significantly by the maximum hypothetical earthquake. However, localized areas were investigated and, where appropriate, live loads were combined with dead loads and the maximum hypothetical earthquake load. Roof live loads from snow and ice were considered as acting simultaneously with maximum hypothetical earthquake loads.
DSAR-5.11 Information Use Page 6 of 16 Structures Other Than Containment Rev. 1
- c. Wind Load (W)
Wind loadings were incorporated as set forth in the ASCE paper No. 3269 Wind Forces on Structures Transactions of the American Society of Civil Engineers, Part II, 1961, for the fastest mile of wind, which is 90 miles per hour; (mph) basic wind velocity 30 feet above ground level at the site for 100 years period of recurrence.
- d. Wind Loading due to Tornado (N)
The design basis wind velocity from a tornado event is 230 mph for the Midwest zones based on studies of tornado winds as defined in Regulatory Guide 1.76, Revision 1.
Class I structures, other than the containment, were originally designed to withstand a tornado with a maximum wind velocity of 300 miles per hour. The wind loads were distributed throughout the structures in accordance with ASCE paper No. 3269 utilizing a uniform load throughout the height of the structures.
The grade slab of the auxiliary building was designed to support falling debris that might result from tornado wind speeds in excess of the design wind speed of 300 mph so as to provide additional margin. The emergency diesel generator enclosure and the spent fuel pool structure were designed to withstand a tornado with a maximum wind velocity of 500 miles per hour, and thus have additional margin beyond the 230 mph basis value.
The 230 mph and 500 mph maximum wind velocities specified in the DSAR were considered to be the sums of the translational and rotational components of the tornado.
DSAR-5.11 Information Use Page 7 of 16 Structures Other Than Containment Rev. 1
- e. Pressure Loading due to a Differential Pressure (Q)
Class I structures, other than the containment, were designed to withstand a tornado with a maximum wind velocity of 300 miles per hour and a concurrent pressure drop of 3 psi applied over a period of 3 seconds as the tornado passes across the building. This is conservative in comparison to the requirements in Regulatory Guide 1.76, Revision 1.
Sufficient venting was provided to prevent the differential pressure , from exceeding a 1.5 psi design value during depressurization which, when combined with other applicable loads, was determined to be within the allowable load criteria as defined later in this section (Reference 5-14).
Where non-vented structures would experience only external depressurization (internal pressures being greater than external pressures), vented structures are subject to external pressurization (internal pressures being lower than external) during the repressurization phase of a tornado. The resulting loads could be more limiting than those of the depressurization phase. The vented structures have, therefore, been subsequently reanalyzed for a complete tornado transient which includes the pressure drop (depressurization) of 3 psi in 3 seconds followed by a low pressure dwell period followed by a recovery pressure rise (repressurization of 3 psi in 3 seconds). The dwell period was sufficient for internal pressures to drop 3 psi prior to repressurization, which results in the most conservative recovery differentials. The transient reanalysis was performed using a suitable dynamic Thermal-Hydraulic analysis code which models the structure as a series of internal volumes connected by various flow paths and vent openings to other volumes and/or boundary conditions. The tornado transient was applied as a time history pressure boundary condition on external flow paths. The structures have been shown to be within design basis allowables for the resultant repressurization differentials combined with other applicable loads. This demonstrates no loss of function during the repressurization phase of a design basis tornado.
Two cases were considered during design in determining vent area requirements. First, a space communicating directly to the outside was treated as a chamber with a sharp edge orifice. The orifice was sized, using classical formulae, to give pressure drop of 1.5 psig when flow was fully developed. The flow corresponding to that pressure drop was that required to reduce the pressure in the room by 0.5 psi per second. The criterion developed by this process was that there should be one square foot of vent area for each 1,000 cubic feet of space. This criterion included a margin of safety over the calculation value. For reanalysis, it was conservatively assumed that exterior hinged doors and horizontal concrete relief panels reclose during repressurization when air flow reverses in the direction of closure resulting in reduced vent area and higher than 1.5 psid pressure drops.
DSAR-5.11 Information Use Page 8 of 16 Structures Other Than Containment Rev. 1 In many cases, spaces do not communicate directly with the outside, but through another space. For example, the ground floor of the auxiliary building communicates directly to the outside, but the basement communicates indirectly, i.e., through the ground floor. A two stage iterative model, using the same classical formulae as above, was used to calculate this case for design. The criterion used was that pressure drop across an outside wall should not exceed 1.5 psi and pressure drop across an interior wall or ceiling should not exceed 1 psi. The calculation was performed on a dynamic basis, i.e., the tornado pressure depression of 0.5 psi per second was assumed to act on initially static conditions.
This ramp acted for three seconds. The P between the basement and the first floor, and between the first floor and the outside, was calculated as a function of time. It was found that an opening of one square foot per thousand cubic feet of basement volume was sufficient between the basement and the first floor. Also, an opening in the outside wall of four square feet per thousand cubic feet of first floor volume was sufficient.
For reanalysis, it was conservatively assumed that interior hinged doors reclose during repressurization if air flow reversed in the direction of closure. This resulted in pressure differentials greater than 1 psid for some interior envelopes.
The vent areas consist primarily of doors and relief panels. These were assumed, for original design, not to be capable of resisting more than approximately 0.5 psi pressure differential. With resistance capability of only one third the design pressure differential, these barriers were expected to open well within the required time. For reanalysis, the existing fire doors installed since original construction were found, from manufacturers data, to have failure ratings greater than 0.5 psid in the open direction. The appropriate values were used for reanalysis. It has been shown that these doors open in time to limit pressure differentials to acceptable values based on the building structures compliance with applicable load limits for no loss of function.
- f. Tornado Missile Load Class I structures were also designed to withstand the spectrum of tornado generated missiles listed in Section 5.8.1.1. The spectrum of tornado generated missiles and the methodology for structural evaluations were updated by Amendment 272.
DSAR-5.11 Information Use Page 9 of 16 Structures Other Than Containment Rev. 1 The methodology uses Regulatory Guide 1.76, Revision 1 and Topical Report BC-TOP-9A, Revision 2 to address protection of SSCs from tornado-generated-missiles at FCS with one exception. The exception regards the potential impact height of an automobile missile where procedural controls prohibit vehicle access to higher surrounding elevations within 0.5 miles of plant structures during periods of increased potential for tornadoes
- g. Seismic Load (E, E)
E = Seismic load from operating basis earthquake (OBE)
E' = Seismic load from maximum hypothetical earthquake (also called Design Basis Earthquake, DBE)
Class I structures were designed for seismic loads as discussed in Appendix F.
- h. Soil Pressure Load (H)
Load due to lateral earth pressure or ground water pressure for design of structures below grade. Load due to pressure of bulk materials for design of other retention structures.
- i. Flood Load (F, F)
F = Flood load to elevation 1007 feet Hydrostatic load due to lateral pressure of floodwaters up to 1007 feet elevation. These loads are equal to the product of the water pressure multiplied by the surface area on which the pressure acts. Hydrostatic pressure is equal in all directions and acts perpendicular to the surface on which it is applied.
F` = Hydrostatic load to elevation 1014 feet Class I structures were also designed for the Corps of Engineers estimate of the flood level that might result from the failure of Oahe or Fort Randall dams. The estimated flood level resulting from the failure of a dam coincident with the probable maximum flood is 1014 feet (See Section 2.7.1.2).
DSAR-5.11 Information Use Page 10 of 16 Structures Other Than Containment Rev. 1 Operating Basis Load Combinations for Class I Steel Structures Class I steel structures were designed on the basis of working stress for the following load combinations:
S=D+L+H S = D + L + H + W or E S=D+H+F where:
S= Required section capacity The ACI Code 318-63 and the AISC Code for structural steel, 1963 edition, design methods and allowable stresses are used for reinforced concrete and steel structures respectively.
Design Basis Load Combinations for Class I Steel Structures Class I steel structures were also designed on the basis of no loss of function for the following load combinations:
U = 1(D + H + E)
U = 1(D + H + L + E)
U = 1(D + N + Q)
U = 1(D + 1.25H + F) where:
U= Ultimate strength capacity required
= Reduction factors in accordance with the following values and applications:
= 0.90 for structural steel The AISC Code 318-63 for Structural Steel, 1963 edition, design methods and allowable stresses were used for steel structures.
DSAR-5.11 Information Use Page 11 of 16 Structures Other Than Containment Rev. 1 Operating Basis Load Combinations for Class I Concrete Structures Class I structures were designed on the basis of working stress for the following load combinations:
S=D+H+L S = D + L + H + W or E S=D+H+F where:
S = Required section capacity The ACI Code 318-63 design methods and allowable stresses were used for reinforced concrete.
The Auxiliary Building, with the exception of the foundation mat and the Spent Fuel Pool, design criteria changed to implement the ultimate strength design method for normal/operating service conditions for changes and reanalysis using the following load combinations from sections 9.3.1 through 9.3.5 of ACI 318-71 (Ref. 5.13.13):
U = 1 (1.4D + 1.7L + 1.7H)
U = 1 (1.05D + 1.275L + 1.275W + 1.275H) (1)
U = 1 (1.05D + 1.275L + 1.40E + 1.275H) (2)
U = 1 (1.4D + 1.7H + 1.4F) where:
U = Ultimate strength capacity per the ACI 318-63 Code
= Reduction factors in accordance with the following values and applications:
= 0.90 for concrete in flexure
= 0.90 for mild reinforcing steel in direct tension excluding mechanical or lapped splices
= 0.85 for mild reinforcing steel in direct tension with lapped or mechanical splices
= 0.85 for diagonal tension, bond and anchorage
= 0.70 for tied compression members
DSAR-5.11 Information Use Page 12 of 16 Structures Other Than Containment Rev. 1 (1) When D or L reduces the effect of W, the corresponding coefficients shall be taken as 0.90 for D and zero for L.
(2) When D or L reduces the effect of E, the corresponding coefficients shall be taken as 0.90 for D and zero for L.
The ultimate strength capacity of Class I reinforced concrete structures is determined in accordance with the ultimate strength provisions from the ACI 318-63 Code using the capacity reduction factors, listed above.
Design Basis Load Combinations for Class I Concrete Structures Class I structures were also designed on the basis of no loss of function for the load combinations shown below using the ultimate strength design provisions of the ACI 318-63 Code.
U = 1 (1.0D + 1.0H + 1.0E')
U = 1 (1.0D + 1.0L + 1.0H + 1.0E'); Live Load (L) as required.
U = 1 (1.0D + 1.0N + 1.0H + 1.0Q)
U = 1 (1.0D + 1.25H + 1.0F')
where:
U= Ultimate strength capacity required per the ACI 318-63 Code
DSAR-5.11 Information Use Page 13 of 16 Structures Other Than Containment Rev. 1 Special Case Load Combinations
- a. Load Combinations for Spent Fuel Pool The spent fuel pool (SFP) structure, including walls, slab and piling, was revisited for the 1994 rerack modification (Ref. 5.13.11). A three-dimensional ANSYS finite element analysis was performed. The design basis and load combinations have been upgraded to those prescribed in the NRC Standard Review Plan (SRP) 3.8.4. After deleting those loads which are not applicable to the SFP structure, the limiting factored load combinations are as follows:
U = 1.4D +1.9E U = 0.75 (1.4D + 1.7To + 1.9E)
U = D + Ta + E U = D + Ta + 1.25E where:
U= Ultimate strength capacity required D= Dead load E= Design earthquake E = Maximum hypothetical earthquake Ta = Abnormal design thermal load To = Normal operating thermal load The pool is filled with water. The hydrostatic pressure, dead load of racks plus 1083 fuel bundles having conservatively postulated dry weight of 2480 lbs per assembly, water sloshing and convective load, and thermal load were considered. The pool water temperature of 140°F which bounds the normal operating condition was utilized for the analysis. Cracked sections were assumed in the thermal stress analysis.
Cracks are usual in reinforced concrete structure. Such credit is permitted by ACI 349-85. The fuel transfer canal, which is next to the spent fuel pool, is assumed to be drained to maximize the loading condition for the spent fuel pool. The calculated loads for the SFP structure, including the walls, slab, and piling, do not exceed the ultimate strength capacity allowable delineated in SRP 3.8.4 and the applicable ACI Code.
A stainless steel liner was provided on the inside face of the pool. This liner plate, due to its ductile nature, will absorb the strain due to the cracking of the concrete in the walls. Per reference 5.13.12, it is concluded that no tearing or rupturing of the liner occurs, no fatigue problems occur, and material stresses do not exceed stress allowables.
DSAR-5.11 Information Use Page 14 of 16 Structures Other Than Containment Rev. 1 Under prolonged outage of the fuel pool cooling system, the pool water could reach a boiling temperature. Under these conditions, the ultimate strength capacity allowables are not exceeded (Ref. 5.13.12).
No special provisions have been made to control cracking, except that the stresses are kept within a moderate range. Such cracks are usual in a reinforced concrete structure.
Codes and Standards The design of Class I structures, other than the containment, was governed by the then applicable building design codes and standards. In general, those of the American Institute of Steel Construction, the American Concrete Institute, and the American National Standards Institute were followed.
Generally accepted design procedures were used in the development of all structures with modern computerized practices to facilitate the study of all credible combinations of loadings.
Structural steel was designed in accordance with the requirements of the Specification for the Design, Fabrication, and Erection of Structural Steel for Buildings, 1963 edition, of the AISC. Elastic theory was the basis of design for all structural steel except for the hold-back bolts at the steam generators.
Reinforced concrete was designed in accordance with the Building Code Requirements for Reinforced Concrete, of the ACI (ACI-318-63) and as stipulated in Section 5.11.3.1.
Concrete Compressive Strength for the Auxiliary Building Class B concrete was used in the construction of the Auxiliary Building.
The compressive concrete strength (fc) used for the Auxiliary Building during original design was 4000 psi.
A higher concrete design compressive strength value of 4500 psi was established for the Auxiliary Building using statistical analysis of the 28-day test data based on Building Code ACI 318-63 Section 504(c) and limited to no greater than the 95% confidence level of all test data. This value, 4500 psi, was approved in Amendment No. 293 and may be used for activities that require reanalysis of the Auxiliary Building with the following exceptions:
- Auxiliary Building exterior walls below 1007 elevation
- Auxiliary Building foundation mat
- Spent Fuel Pool
DSAR-5.11 Information Use Page 15 of 16 Structures Other Than Containment Rev. 1 Steel Reinforcing Yield Strength for the Auxiliary Building The reinforcing steel yield strength (Fy) used for the Auxiliary Building during original design was 40 ksi.
A higher yield strength value of 42 ksi was established for the Auxiliary Building using statistical analysis of the original test reports for individual bar sizes. The value was limited to the lowest 95% confidence value determined for a bar size data set. This value, 42 ksi, was approved in Amendment No. 293 and may be used for activities that require reanalysis of the Auxiliary Building with the following exceptions:
- Auxiliary Building foundation mat
- Spent Fuel Pool 5.11.4 Design of Structures - Class II Class II structures were designed in accordance with conventional practice and on the basis of generally recognized governing codes and criteria such as those of the American Institute of Steel Construction, American Concrete Institute, National Building Code and the American National Standards Institute. The following criteria apply:
- a. Dead loads include the weight of the structure and other items permanently affixed to it such as equipment, cables, piping, and ducts.
- b. Live loads include floor loadings of a magnitude commensurate with their intended use, ice and snow loads on roofs, and impact loads such as may be produced by equipment, cranes, and handling of equipment.
- c. Wind loadings were incorporated as set forth in the National Building Code, 1967 edition, for a moderate windstorm area.
- d. Earthquake loads were computed and utilized in accordance with the National Building Code, 1967 edition, as defined in Appendix F, Section 2.4. These loads were applied to the structure independently of wind loading or horizontal crane impact loading.
- e. Horizontal crane impact forces were computed in accordance with the stipulations of the American Institute of Steel Construction, sixth edition.
- f. For loading combinations involving wind or earthquake forces, a one-third increase in allowable design stresses was permitted.
DSAR-5.11 Information Use Page 16 of 16 Structures Other Than Containment Rev. 1
- g. The design hydrostatic head for Class II structures was assumed to be at elevation 1007'-0". The circulating water tunnels were designed as pressure tunnels with hydrostatic pressures of a magnitude commensurate with their intended use.
For the most part, Class II structures were supported on piling with a compressive load capacity of 90 tons and an uplift capacity of 22.5 tons.
Other foundations, separate from the main building, were supported on piling of lesser capacity.
The design of Class II structures was governed by then applicable building design codes and standards such as those of the American Institute of Steel Construction, American Concrete Institute, National Building Code and the American National Standards Institute. Generally accepted design procedures were used.
5.11.5 Visual Weld Acceptance Criteria Visual weld acceptance criteria for use in structures and supports designed to the requirements of ASIC and AWS D1.1 and other Non-ASME code stamped structures shall be in accordance with AWS D1.1-86 or later revisions, or NCIG-01, Revision 2, titled Visual Weld Acceptance Criteria for Structural Welding at Nuclear Power Plants. The NCIG-01, Revision 2, document is included as an EPRI document EPRI NP-5380, Volume 1, Research Project Q101, September 1, 1987.
The use of the NCIG-01, Revision 2, acceptance criteria shall be specified in station approved procedures prior to use.
The NCIG-01, Revision 2, has been evaluated by Engineering and found to be technically acceptable for use at the Fort Calhoun Station.