ML13317A114
| ML13317A114 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 05/04/1982 |
| From: | Krieger R Southern California Edison Co |
| To: | Crutchfield D Office of Nuclear Reactor Regulation |
| References | |
| TASK-03-02, TASK-03-04.A, TASK-3-2, TASK-3-4.A, TASK-RR NUDOCS 8205100269 | |
| Download: ML13317A114 (10) | |
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Southern California Edison Company PO BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 May 4, 1982 Director, Office of Nuclear Reactor Regulation Attention:
D. M. Crutchfield, Chief Operating Reactors Branch No. 5 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D.C.
20555 Gentlemen:
Subject:
Docket No. 50-206 SEP Topics:
111-2, Wind and Tornado Loadings III-4.A, Tornado Missiles San Onofre Nuclear Generating Station Unit 1 Enclosed find our draft assessments for SEP Topics 111-2, Wind and Tornado Loadings, and III-4.A, Tornado Missiles. As indicated in these reports, equipment that is protected by masonry walls or that is unprotected are susceptible to damage from tornado winds and missiles. It should be noted, however, that these results are based on tornado parameters which do not appear appropriate for use in the reevaluation of San Onofre 1.
Resolution of these concerns will depend on the selection, during the integrated assessment, of appropriate tornado parameters as part of SEP Topic II-2.A, Severe Weather Phenomena.
If you have any questions regarding these assessments or require additional information, please let me know.
Very truly yours, R. W. Krieger Supervising Engineer San Onofre Unit 1 Licensing Enclosures 8205100269 820504 PRK 05000206 pDR ADC PDR P
SAN ONOFRE NUCLEAR GENERATING STATION, UNIT 1 SAFETY ASSESSMENT REPORT TOPIC 111-2, WIND AND TORNADO LOADINGS I. INTRODUCTION The purpose of SEP Topic 111-2 is to assure that safety-related structures are adequate to resist expected wind and tornado loadings including tornado pressure drop loading.
II. REVIEW CRITERIA The review criteria for this topic is General Design Criteria 2, design bases for protection against natural phenomena.
III. RELATED SAFETY TOPICS SEP Topic III-4.A reviews tornado missiles.
SEP Topic III-1 identifies structures which are considered safety related.
SEP Topic II-2.A identifies wind and tornado parameters.
SEP Topic III-7.B reviews design codes, criteria and loading combinations.
IV. REVIEW GUIDELINES The design tornado used for evaluation of the structures is defined as having a maximum wind speed of 260 mph (220 mph rotational wind speed plus 40 mph translational wind speed) with a pressure drop of 1.5 psi in 4.5 seconds. This is based on the 107-tornado identified in SEP Topic II-2.A. The design wind is also specified in SEP Topic II-2.A.
Currently accepted criteria for wind and tornado loadings is outlined in Standard Review Plan (SRP) Sections 3.3.1 and 3.3.2.
V. EVALUATION Conversion of wind and tornado loads was done for the following evaluations using the methods of reference A.
Wind Loads As stated in Section 4.3.2.3 of the SONGS Unit 1 FSA, a design wind velocity of 100 miles per hour was used for the containment sphere.
Typical wind loads of 15 or 20 psf, corresponding to wind velocities of approximately 80 and 90 mph respectively, were considered for the remaining structures which were constructed as part of the original plant design, where applicable. The 90 mph wind criteria was applied above a height of 30 feet from the ground. Wind loadings were not combined with earthquake loads in accordance with accepted practice. In general the wind load combinations, with the exception of the vent stack, did not govern the design. The vent stack is a light gage steel stack and as such the aerodynamic forces were more significant than the seismic forces. Wind forces on the vent stack were calculated in accordance with "The Design of Self Supported Steel Stacks" by Kaiser Steel Corp.,
printed in "Modern Designing with Steel," Vol. 6, No. 1, May 1960.
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-2 As stated in Reference B and Reference C, the design wind load for the sphere enclosure building and the diesel generator building are based on a design wind velocity (defined as the fastest mi/h of wind at 30 feet above ground level) of 100 mi/h, and the procedures of "Building Code Requirements for Minimum Design Loads in Buildings and Other Structures, ANSI A58.1-1972" were used to convert the wind velocity into applied forces for these structures.
Tornado Loads The following building structures were reviewed for loading from tornados:
Control Building Reactor Auxiliary Building Fuel Storage Building Turbine Building Ventilation Equipment Building Sphere Enclosure Building Diesel Generator Building In each case the maximum withstand pressure and corresponding tornado wind are indicated.
Control Building The Control and Administration Building is a three-story reinforced concrete structure with a single-story administration office building attached to the east side. The administration office building consists of glass windows on the east side and reinforced masonry block walls surrounding the station batteries and the security batteries on the south end. The exterior reinforced concrete walls of the Control Building vary in thickness from 9" to 2'-10" and the concrete roof thickness varies from 7" to 2'-0". The Control Building's masonry walls are reinforced with #4 rebar spanning vertically every 24".
These walls would be able to resist a uniformly distributed pressure of 0.28 psi, corresponding to a tornado wind of 140 mph.
The 9" thick reinforced concrete wall on the east side and the 7" thick reinforced concrete roof above the Heating-Ventilating and Air Conditioning equipment area would provide the least wind and tornado resistance of the remaining exterior structural elements. The 9" concrete wall has the capacity to withstand a uniform pressure of 0.89 psi.
This capacity translates into the ability to withstand the pressure drop associated with a 150 mph tornado. The 7" concrete roof could resist a tornado of up to 160 mph.
Reactor Auxiliary Building With the exception of the northeast corner, the Reactor Auxiliary Building is a single story, partially embedded, concrete structure. The
-3 northeast corner of the Reactor Auxiliary Building includes an additional story constructed of masonry walls, reinforced concrete walls and slabs, and structural steel floor framing.
The majority of the Reactor Auxiliary Building is embedded and therefore will not be exposed to a tornado.
The first story concrete roof is capable of resisting the full design tornado.
The additional story, located on the northeast corner, is composed of masonry block walls and a sheet metal roof. The masonry block walls are reinforced with #5 rebars and 48" spacing vertically. This means that only every sixth cell is grouted and that the majority of the cells are empty. Consequently the exposed northeast corner is considered not capable of withstanding a tornado of any significant magnitude. However, failure of this portion will not affect the structural integrity of the embedded first story portion of the building.
Fuel Storage Building The Fuel Storage Building consists of a reinforced concrete pool supporting a superstructure constructed of reinforced hollow concrete block walls and steel framing. The walls of the Fuel Storage pool are composed of 4' thick reinforced concrete and can withstand the 260 mph design tornado. The remaining portions of the building are composed of masonry block walls and metal decking roofs. These portions are unable to resist a tornado of any significant magnitude.
Turbine Building The Turbine Building consists of four individual structural systems which surround the turbine pedestal.
These structural systems are composed of structural steel framing and masonry block walls. As with the other masonry walls examined, these walls will not withstand any significant tornado.
Ventilation Equipment Building The Ventilation Equipment Building is a single-story structure with a roof of steel decking on a structural steel frame. The roof is supported by peripheral, reinforced, hollow, concrete block walls.
Being masonry, these walls would not be able to withstand a tornado of any significant magnitude.
Sphere Enclosure Building The sphere enclosure building is protected against the design basis tornado loads. An evaluation of the design basis tornado characteristics was provided in the Safety Evaluation Report supporting Amendment No. 20 (Reference D).
-4 Diesel Generator Building The diesel generator building is protected against the design basis tornado loads. An evaluation of the design basis tornado characteristics was provided in the Safety Evaluation Report supporting Amendment No. 20 (Reference D).
Other Safety Related Components Many of the components identified as safety related are not enclosed in structures and thus not protected against tornado loads. Among these are the refueling water storage tank, condensate storage tank, portions of the salt water cooling system, component cooling water system and the auxiliary feedwater pumps.
VI.
CONCLUSIONS Although the Containment Sphere Enclosure Building and Diesel Generator Building are designed for a 100 mile per hour wind, other structures are not.
Resolution of the design wind speed for San Onofre-1 will be considered as part of the integrated assessment for this facility.
As identified above, many structures are not capable of withstanding the 260 mph design basis tornado. However, as indicated in our comments on SEP Topic II-2.A (SCE letter from W. C. Moody to D. M. Crutchfield, NRC, dated March 18, 1981) it would appear that this is an overly conservative tornado for use in the reevaluation of San Onofre 1. Our letter indicates that the IDR report, which calculates a peak windspeed from 98 to 272 miles per hour with an expected value of 172 miles per hour, would be more appropriate for use at San Onofre 1. Resolution of the design tornado parameters will be considered as part of the integrated assessment for this facility.
VII. REFERENCES A.
BC-TOP-3-A, "Tornado and Extreme Wind Design Criteria for Nuclear Power Plants," Rev. 3, Bechtel Power Corporation, August 1974.
B. Amendment 52 to Final Safety Analysis, San Onofre Nuclear Generating Station, Unit 1, Docket 50-206.
C. Amendment 28 to Final Safety Analysis, San Onofre Nuclear Generating Station, Unit 1, Docket 50-206.
D. Safety Evaluation by the Office of Nuclear Reactor Regulation Supporting Amendment No. 20 to Provisional Operating License No. DPR-13, San Onofre Nuclear Generating Station, Unit 1, Docket 50-206.
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SAN ONOFRE NUCLEAR GENERATING STATION, UNIT 1 SAFETY ASSESSMENT REPORT TOPIC III-4.A TORNADO MISSILES I. INTRODUCTION The intent of this topic is to review the plant design relative to its ability to withstand tornado-generated missiles to assure that structures, systems and components necessary to ensure:
- 1. The integrity of the reactor coolant pressure boundary,
- 2. The capability to shut down the reactor and maintain it in a safe shutdown condition, and
- 3. The capability to prevent accidents which could result in unacceptable off-site exposures can withstand the impact of an appropriate postulated spectrum of tornado-generated missiles.
An assessment of the adequacy of a plant to withstand the impact of tornado missiles includes:
- 1. Determination of the capability of the exposed systems, components and structures to withstand key missiles (including small missiles with penetrating characteristics and larger missiles which result in overall structural impact)
- 2. Determination of whether any areas of the plant require additional protection.
II. REVIEW CRITERIA The plant has been reviewed with regard to General Design Criteria 2, "Design Bases for Protection Against Natural Phenomena," of Appendix A to 10 CFR 50, which requires, in part, that structures sytems and components important to safety be designed to withstand the effects of natural phenomena such as tornados without loss of capability to perform their safety functions.
III. RELATED SAFETY TOPICS SEP Topic II-2.A, "Severe Weather Phenomena" describes the tornado characteristics for the plant.
-2 SEP Topic 111-2, "Wind and Tornado Loadings," reviews the capability of the plant structures, systems and components to withstand wind and tornado loadings.
SEP Topic VII-3, "Systems Required for Safe Shutdown" reviews those systems needed to achieve and maintain the plant in a safe shutdown condition.
IV. REVIEW GUIDELINES Current review guides for this topic include Standard Review Plan (SRP)
Sections 3.3.2, "Tornado Loadings," 3.5.3, "Barrier Design Procedure,"
and 3.5.1.4, "Missiles Generated by Natural Phenomena," Revision 1. The tornado missiles considered for evaluation of the structures are shown in Table 1. These are based on the criteria used in the design of San Onofre Unit 2&3.
V. EVALUATION The following safety related structures were evaluated for the effects of tornado geneated missiles. The analytical methods described in Reference A were used to determine the missile withstand capability of these structures.
Control Building Reactor Auxiliary Building Fuel Storage Building Turbine Building Ventilation Equipment Building Sphere Enclosure Building Diesel Generator Building Control Building The Control and Administration Building is a three-story reinforced concrete structure with a single-story administration office building attached to the east side. The administration office building consists of glass windows on the east side and reinforced masonry block walls surrounding the station batteries and the security batteries on the south end. The exterior reinforced concrete walls of the Control Building vary in thickness from 9" to 2'-10" and the concrete roof thickness varies from 7" to 2'-0".
The Control Building's masonry walls are reinforced with #4 rebar spanning vertically every 24" and backfilled with grout. However, since the rebar only occurs once every 24" only every third cell is filled, the rest of the cells are empty. The remaining ungrouted cells have only two 1-1/4" masonry face shells to resist damage associated with tornado generated missiles. The penetration resistance of these face shells is negligable, consequently the wall in the vicinity of these empty cells is vulnerable to missile damage. Because these empty cells have little or no resistance to missile penetration, and because they comprise a majority of the wall, the masonry walls are considered to have no resistance to any of the missiles listed in Table 1.
-3 TABLE 1 TORNADO-GENERATED MISSILES CONSIDERED Maximum Kinetic Weight Impact Area Velocity Energy Description (1bs)
(ft2)
(ft/s)
(ft-lbs)
A 12-foot wood plank, 108 0.333 322 1.74 x 105 4 x 12 inches in cross-section, weigh ing 108 pounds, traveling end on at a speed of 220 mi/hr, striking the structure at any elevation.
A steel pipe, 75.8 0.063 147 2.54 x 104 Schedule 40, 3 inches in diameter by 10 feet long, weighing 75.8 pounds, traveling end on at 100 mi/hr, striking the structure at any elevation.
An automobile of 4000 20.0 73.5 3.36 x 105 4,000 pounds weight striking the structure at 50 mi/hr on a contact area of 20 ft2, any portion of the impact being not more than 25 feet above grade.
A utility pole, 1490 0.994 VH - 152 5.35 x 105 13 1/2 inches in dia meter, Missile F of Vy 122 3.44 x 105 SRP 3.5.1.4 A steel rod, 1-inch 8
0.0054 VH - 229 6.51 x 103 diameter x 3 ft long, Missile C of SRP 3.5.1.4 Vy - 183 4.16 x 103
-4 The 9" thick reinforced concrete wall on the east side and the 7" thick reinforced concrete roof above the Heating-Ventilating and Air Conditioning equipment area would provide the least tornado missile resistance of the remaining exterior structural elements. This 7" thick roof would resist missiles generated by a tornado of up to 160 mph.
Reactor Auxiliary Building With the exception of the northeast corner, the Reactor Auxiliary Building is a single story, partially embedded, concrete structure. The northeast corner of the Reactor Auxiliary Building includes an additional story constructed of masonry walls, reinforced concrete walls and slabs, and structural steel floor framing.
The majority of the Reactor Auxiliary Building is embedded and therefore will not be exposed to tornado missiles. The first story concrete roof will be exposed to tornado missiles, and is capable of resisting the missiles of Table 1.
The additional story, located on the northeast corner, is composed of masonry block walls and a sheet metal roof. The masonry block walls are reinforced with #5 rebars with 48" spacing vertically. This means that only every sixth cell is grouted and that the majority of the cells are empty. As previously described, empty cells, and masonry walls composed of empty cells, have little or no resistance to missile damage. However, failure of this portion will not affect the structural integrity of the embedded first story portion of the building.
Fuel Storage Building The Fuel Storage Building consists of a reinforced concrete pool supporting a superstructure constructed of reinforced hollow concrete block walls and steel framing. The walls of the Fuel Storage pool are composed of 4' thick reinforced concrete and can easily withstand the design tornado missiles. The remaining portions of the building are composed of masonry block walls and metal decking roofs. As previously described, hollow masonry block walls are incapable of resisting tornado missiles.
Turbine Building The Turbine Building consists of four individual structural systems which surround the turbine pedestal.
These structural systems are composed of structural steel framing and masonry block walls.
As with the other masonry walls examined, these walls provide no resistance to tornado missiles.
-5 Ventilation Equipment Building The Ventilation Equipment Building is a single-story structure with a roof of steel decking on a structural steel frame. The roof is supported by peripheral, reinforced, hollow, concrete block walls. Being masonry, these walls offer little resistance to tornado missile loading.
Sphere Enclosure Building Amendment 52 to the license indicates that the sphere enclosure building was designed to withstand the tornado missiles described in Table 1.
Diesel Generator Building Amendment 38 to the license indicates that the diesel generator building design is based on the tornado design parameters stated in Table 1.
Other Components Other safety related components which are not enclosed in the above stated buildings and are required for safe shutdown are not protected from tornado missiles. Among these components are the following:
Portions of the Chemical and Volume Control System Including Refueling Water Storage Tank Portions of the Salt Water Cooling System Portions of the Component Cooling Water System Condensate Storage Tank Auxiliary Feedwater Pumps Steam Dump Valves VI.
CONCLUSIONS Masonry walls containing safety related components at San Onofre 1 are susceptible to tornado missiles. Other components which are located outside of building structures are also susceptible to damage from tornado missiles. The capability of these components to perform their safety functions is dependent upon successful resolution of SEP Topic II-2.A which defines the tornado to be considered for the San Onofre 1 site.
VII. REFERENCES A. BC-TOP-9-A, "Design of Structures for Missile Impact," Rev. 2, Bechtel Power Corp, September 1974.
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