ML13330A165

Tornado & Straight Wind Hazard Probability for San Onofre Nuclear Power Reactor Site,Ca. Sheet Requesting Info for SEP Topic XV-16 Encl

ML13330A165
Person / Time
Site:	San Onofre
Issue date:	05/31/1980
From:	Mcdonald J TEXAS TECH UNIV., LUBBOCK, TX
To:
Shared Package
ML13330A164	List: ML13330A163 ML13330A165
References
TASK-02-02.A, TASK-15-16, TASK-2-2.A, TASK-RR NUDOCS 8101120149
Download: ML13330A165 (26)

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TORNADO AND STRAIGHT WIND HAZARD PROBABILITY for SAN ONOFRE NUCLEAR POWER REACTOR SITE, CALIFORNIA by James R. McDonald, P.E.

Institute for Disaster Research TEXAS TECH UNIVERSITY Lubbock, Texas 79409 8101180

TORNADO AND STRAIGHT WIND HAZARD PROBABILITY for SAN ONOFRE NUCLEAR POWER REACTOR SITE, CALIFORNIA by James R. McDonald, P.E.

Prepared for U.S. Nuclear Regulatory Commission Site Safety Research Branch Division of Reactor Safety Research May, 1980 Institute for Disaster Research Texas Tech University Lubbock, Texas

I. INTRODUCTION The objective of this report is to assess tornado and straight wind probability hazards at the San Onofre nuclear power reactor site. The hazard probability analyses are developed using storm records from the geographical region surrounding the site. Ninety-five percent confidence limits on the probabilities are presented to give an indication of the accuracy of the expected hazard probabilities.

The author (McDonald, 1980a) performed a tornado hazard probability assessment for the state of California. The San Onofre reactor site is located in local region Zone 1 as defined in the above referenced report.

Therefore, the tornado hazard assessment presented herein is identical to that for California Zone 1. The data and analyses are presented herein for completeness.

The final hazard probability model is presented graphically in Figure 6. Windspeeds corresponding to selected probability.values are summarized in Table 8. The basic data used in the calculations are presented in this report. Derivation of the tornado hazard assessment methodology, the rationale and assumptions are given in McDonald (1980).

Use of the Type I extreme value distribution function for straight wind hazard assessment is well documented in Simiu and Scanlan (1978).

II. TORNADO HAZARD PROBABILITY ASSESSMENT A. METHODOLOGY The tornado hazard model developed by the Institute for Disaster Research (IOR) accounts for gradations of damage across the tornado path width and along its length (McDonald, 1980).

There are four basic steps involved in the methodology:

(1) Determination of an area-intensity relationship in a global region surrounding the site of interest.

(2) Determination of an occurrence-intensity relationship in a local region surrounding the site.

(3) Calculation of the probabilities of a point within the local region experiencing windspeeds in some windspeed interval.

(4) Determination of the probability of windspeeds in the local region exceeding the interval values.

B. CALCULATIONS

1. Site

2. Coordinates Latitude 330 22' 53." N Longitude 1170 31' 17" W

3. Area-Intensity Relationship Global Region Odd shaped region encompassing the entire state of California. See Figure 1.

Data DAPPLE Tornado Data Tape UT1678 (Fujita, et al., 1979)

Period of Record 1971 -

1978

0 430 370 08 L

REGION OCA REGION S A ONOFRE S A DI 1E,GO FIGURE 1. LOCAL AND GLOBAL REGIONS

See Figure 1 for definition of the global region. The region is selected to be as large as possible and still give reasonably homoge nous conditions for tornado formation. The relatively short period of record is used because the data are more complete and accurate than that collected prior to 1971, especially with regard to tornado damage path characteristics. The area-intensity matrix is shown in Table 1. It gives the number of tornadoes in each corresponding area-intensity classification. From this information, the mean damage path area per F-scale can be obtained.

TABLE 1 AREA-INTENSITY MATRIX Number of Tornadoes*

Area Mean Area Interval FO.

Fl F2 F3 F4 F5 (sq mi) 0 9

3 O\\

0 0

0 0.316E-02 1

1 0

0

\\)

0 0

0.100E-01 2

1 2

0 0

0 0

0.316E-01 3

2 2

0 0

0 0.100E-00 4

0 0

0 0

0 0

0.316E-00 5

0 0

1 0

0

\\0 0.100E 01 6

0 0

0 0

0 0.316E 01 7

0 0\\

0 0

0 0

0.100E 02 8

0 0

N0 0

0 0

0.316E 02 9

0 0

0 0

0 0.100E 03 10 0

0 0

O 0

0 0.316E 03 Totals 13 7

1 0

0 0

• Those tornadoes outside the dashed lines are considered outliers and have been eliminated from the data set.

Mean Damage Path Area Per F-Scale FO Fl F2 F3 F4 F5 Mean Area, sq.mi

.0208

.0390 1.000 Median Windsoeed, mph 56 92.5 135 182 233.5 289.5 4

Area-Intensity Function Linear regression analysis of the above area-intensity data, based on a long-log plot, yields the following functional relationship:

Log (Area) = 2.401 Log V - 5.927 (1)

The coefficient of determination is r2 =

0.302 Area-Intensity Relationship The expected mean area is obtained from Equation (1) above.

Upper and lower bound confidence limits are calculated at the 95 percent level.

These values are shown in Table 2.

Figure 2 shows a plot of the area-intensity relationship.

TABLE 2 AREA-INTENSITY RELATIONSHIP WITH 95 PERCENT CONFIDENCE LIMITS FO Fl F2 F3 F4 F5 Expected Mean area, a, sq mi

.0186

.0622

.1542

.3159

.5747

.9629 Lower Limit a.,

sq mi

.0065

.0213

.0474

.0856

.1368

.2027 Upper limit a.,

sq mi

.0540

.1820

.5010 1.1670 2.4140 4.5750 Median F-scale Windspeed, mph

4.

Occurrence-Intensity Relationship Local Region "Odd-shaped region that defines an area of homogeneous meteorological and topographical conditions as they relate to tornado occurrence. See Figure 1 for definition of local region.

5

100 ci i

1.0 4

F 0.1 95%

CONFIDENCE 0

.0 0.01 56 92.5 133.5 182 233.5 289.5 WINDSPEED MPH FIGURE 2. AREA-INTENSITY RELATIONSHIP FOR SAN ONOFRE 6

Data DAPPLE Tornado Data Tape UT1678 (Fujita, et al., 1979)

Period of Record 1950 to 1978 The records used do not necessarily include every tornado that has occurred in the local region. Within a 50 mi radius of the San Onofre site, the population density is 450 persons per sq mi (USNRC, 1979).

This is generally sufficient population to assure that all tornadoes within that area are reported. However, the local region used for the occurrence-intensity relationship emcompasses more than a 50 mi radius.

Some of the.terrain is open with little vegetation, trees, or structures to be damaged should a tornado strike. Because of this situation, it is estimated that the number of unreported tornadoes is perhaps as high as 25 percent. The number of reported tornadoes in the local region is shown in Table 3.

TABLE 3 NUMBER OF TORNADOES IN THE LOCAL REGION FO Fl F2 F3 F4 F5 Number of Tornadoes 12 20 5*

1 0

0 Cumulative Number 38 26 6

1 0

0 Lower Bound F-Scale Windspeed, mph 40 73 113 158 207 261 Occurrence-Intensity Function The function used is obtained by performing a linear regression analysis using the FO and Fl tornadoes and another linear regression using the F2 to F5 tornadoes.

The actual number of reported F2 tornadoes is 2. This gave a nonmonotonically increasing occurrence-intensity function.

Three F2 tornadoes have been arbitrarily added to *the data set.

They could easily be accounted for as unreported tornadoes.

The action tends to be conservative.

7

Linear regression analysis of the data in Table 3 on a semi-log plot gives the following functional relationships:

y = (60.19 )10-.0050x (x < 75 mph)

(2)

-0164x y = (428.23)10 (x > 75 mph) where y is the cumulative number of tornadoes with windspeeds greater than or equal to x.

Occurrence-Intensity Relationship The expected number of tornadoes in the 29 year period is obtained from the occurrence-intensity function (Equation 2).

Upper and lower bound confidence limits are also obtained at the 95 percent level.

These values are then divided by the period of record (29 years) to obtain the number of tornadoes per year for each F-scale classifica tion xi, which is the needed occurrence-intensity relationship required for the hazard probability assessment. Table 4 lists the values used in the probability calculation. Figure 3 shows a plot of the occurrence intensity relationship.

TABLE 4 OCCURRENCE-INTENSITY RELATIONSHIP WITH 95 PERCENT CONFIDENCE LIMITS FO Fl F2 F3 F4 F5 Expected number of tornadoes in inter val, A 12.00 20.00 4.90 0.92 0.15 0.02 Lower limit f 6.38 13.97 0.85 Upper limit n 17.62 26.03 8.96 2.79 0.91 0.32 Expected number of tornadoes per year x 0.41 0.69 0.17 0.03 0.005 0.0008 1

Lower limit X.

0.22 0.48 0.03 1

Upper limit Xi 0.61 0.90 0.31 0.10 0.03 0.01

5. Tornado Hazard Probability The tornado hazard probability calculations are performed by computer, although they can easily be done by hand. The expected hazard probabilities are obtained by using the expected area-intensity relationship (ai) and the expected occurrence-intensity relationship (x.i).

Upper and lower limits of hazard probability are obtained by using the upper and lower limit Ni.s and ai's respectively. The computer printouts for these calculations are contained in Appendix A.

NO. 'OF TORNADOES WITH WINDSPEEDS EXCEEDING THRESHOLD VALUE 5

0 000 0

000 00

10 Cl.

mU

Table 5 summarizes the tornado hazard probabilities, and includes the 95 percent confidence limits. The tornado hazard probability model is plotted in Figure 4. Final hazard probability results are summarized in Section IV of this report.

TABLE 5 TORNADO HAZARD PROBABILITIES WITH 95 PERCENT CONFIDENCE LIMITS Mean Hazard Tornado Windspeeds, mph Recurrence Probability Expected Lower Upper Interval Per Year Value Limit Limit 10,000 1.0 x 10-4

<40

<40

< 40

-5 100,000 1.0 x 10 47

< 40 113 1,000,000 1.0 x 106 105 50 200

-7 10,000,000 1.0 x 10 172 98 272 10

I 10IC cr-5 x 10 I 1 ix 10 W NDPE MPHO

w.

W 0

1x111 50 100.

15O 200 250 300 350 WINDSPEED MPH FIGURE 4. TORNADO HAZARD PROBABILITY MODEL WITH 95 PERCENT CONFIDENCE LIMITS

III.

STRAIGHT WIND HAZARD ASSESSMENT A. METHODOLOGY A set of annual extreme fastest-mile windspeeds are used to fit a cumulative probability distribution function in order to obtain the straight wind hazard probabilities. The Type I extreme value function generally fits the data well.

In view of the studies by Simiu and Filliben (1975),

the Type I distribution function is used in lieu of the Type II that was used previously.(ANSI, 1972). A detailed description of the methodology is given in Simiu and Scanlan (1978).

B. CALCULATIONS Annual extreme fastest-mile windspeed data are not available at the power plant site. The closest weather station with the needed data is San Diego, California, which is located fifty-one miles southeast of the site (See Figure 1).

Terrain and meteorological conditions are such that the data.should be representative of wind conditions at the site.

The data and Type I distribution are taken from weather records from Simiu, Changery and Filliben (1979).

The data covers the.thirty-eight year period 1940 to 1977.

The set of annual extreme fastest-mile wind speeds for San Diego, California is given in Table 6. The windspeeds have been adjusted to.a standard anemometer height of 10 m. The expected windspeeds for various mean recurrence intervals along with 95 percent confidence limits are given in Table 7. The straight wind hazard probability model is plotted in Figure 5.

12

TABLE 6 ANNUAL EXTREME FASTEST-MILE WINOSPEEDS AT SAN DIEGO, CALIFORNIA Windspeed Year mph Direction Date 1940 35 Sw 12/24 1941 37 SW 11/41 1942 37 Sw 03/14 1943 43 SE 01/23 1944 47 SE 11/11 1945 42 SW 03/23 1946 35 S

03/30 1947 26 S

12/05 1948 31 S

03/24 1949 31 SW 11/10 1950 26 SW 01/08 1951 32 SW 03/01 1952 41 S

03/07 1953 27 SW 02/23 1954 33 W

03/16 1955 36 SW 01/18 1956 29 S

04/13 1957 31 SW 04/20 1958 34 S

04/03 1959 27 S

02/11 1960 30 SW 11/20 1961 34 N

10/08 1962 34 S

01/20 1963 35 SE 03/16 1964 37 NW 03/02 1965 36 S

04/08 1966 36 S

11/07 1967 35 5

12/18 1968 35 sw 03/08 1969 38 S

02/25 1970 39 S

02/09 1971 35 W

01/02 1972 34 SE 11/14 1973 38 S

02/11 1974 36 SW 03/08 1975 33 W

11/28 1976 35 W

04/15 1977 35 NW 03/01 Mean Windspeed:

34 5 mph Standard Deviation:

4.46 mph 13

TABLE 7 STRAIGHT WIND HAZARD PROBABILITIES WITH 95 PERCENT CONFIDENCE LIMITS Mean Expected Upper Lower Recurrence Hazard Fastest-Mile Limit Limit Interval Probability Windspeed, moh moh moh 10 1.0 x 10 41 44 38 20 5.0 x 10- 2 43 47 39 50 2.0 x 10- 2 47 51 42 100 1.0 x 10-2 49 55 44 200 5.0 x 10-3 52 53 45 500 2.0 x 10-55 62 47 1,000 1.0 x 10-57 66 49 10,000 1.0 x 10-4 66 77 55 100,000 1.0 x 10-5 74 87 60 1,000,000 1.0 x 10-82 98 66 14

0 10 w

lx 10 o

4 a

Ix IO

\\

5w 0

1 Xr-1x103.

50 100 150 200 250 300 350 WINDSPEED MPH FIGURE 5. STRAIGHT WIND HAZARD PROBABILITIES WITH 95 PERCENT CONFIDENCE LIMITS 15

I*

IV. WINDSPEED HAZARD PROBABILITY MODEL Windspeed hazard probability, which includes both tornadoes and straight winds, is the probability of a point within some defined geographical region experiencing windspeeds greater than or equal to some threshold value in one year. Tornado hazard probabilities are the same at any point within the defined local region. The Type I extreme value distribution function obtained from data collected at San Diego, California is used for the straight wind probability hazard assessment at the San Onofre reactor site.

Thus, in effect, San Diego and the reactor site are contained in a common local region.

Tornado windspeeds are referenced to 30 ft above ground level (approx imately 10 m) and are the maximum horizontal windspeeds. According to Fujita (1971), F-scale windspeeds are fastest-one-quarter mile winds.

However, because of the translational speed of a tornado, winds acting on a structure may be.of considerably shorter duration. Because tornado windspeeds are based on appearance of damage, they are considered to be effective velocities, which include effects of gust, structure size and structure frequency. For design pruposes, the gust response factor for tornado winds may be taken as unity.

The straight winds are fastest-mile windspeeds which have a variable time duration, depending on the magnitude of the windspeeds., Values are normalized to a 10 m anemometer height. For design purposes, gust response factors.greater than unity are appropriate (See ANSI A58.1, 1972).

The tornado and straight wind models are combined in Figure 6 to obtain the final windspeed model.

For design or evaluation purposes, one needs to know the type of storm that controls the criteria.

For windspeeds less than 80 mph, the straight wind model governs.

For windspeeds greater than 16

80 mph, the tornado model governs.. In the case of a-tornado, the atmospheric pressure change and missiles must be taken into account in addition to the wind effects. Because of this, the union of the two events (tornado and straight winds) is not of particular interest. Table 8 summarizes the final windspeed hazard probabilities.

17

Ix'0 95% CONFIDENCE LIMITS 0

__2_

0 a

I 02 w

x lo

.02 Li 0

__a x 10 6 50 IC0 s50 200 250 300 350 WINDSPEED MPH FIGURE 6. TORNADO AND STRAIGHT WIND HAZARD PROBABILITY MODEL FOR SAN N0OFRE POWER REACTOR SITE, CALIFORNIA 18

TABLE 8

SUMMARY

OF WINDSPEED HAZARD PROBABILITIES FOR SAN ONOFRE Mean Expected Recurrence Hazard Windspeed Interval Probability mph Type of Storm 10 1.0 x 10 41 Straight Wind 100 1.0 x 102 49 Straight Wind 1,000 1.0 x 10-3 57 Straight Wind 10,000 1.0 x 10 66 Straight Wind 100,000 1.0 x 10-5 74 Straight Wind 1,000,000 1.0 x 10-105 Tornado 10,000,000 1.0 x 10 -

172 Tornado

REFERENCES

1. ANSI, 1972:

"Building Code Requirements for Minimum Design Loads in Buildings and Other Structures," A58.1, American National Standards Institute, Inc., New York, New York.

2. Fujita, T. T., 1971:

"Proposed Characterization of Tornadoes and Hurricanes by Area and Intensity," SMRP No. 91, The University of Chicago, Chicago, Illinois.

3. Fujita, T. T., Tecson, J. 3, and Abbey, R. F., 1979:

"Statistics of U. S. Tornadoes Based on the DAPPLE Tornado Tape," 11th Conference on Severe Local Storms, Kansas City, Missouri, October 2-5, 1979, published by American Meteorological Society, Boston, Massachusetts.

4. McDonald, J. R., 1980: "A Methodology for Tornado Hazard Assessment,"

Institute for Disaster Research, Texas. Tech University, Lubbock, Texas.

5. Simiu, E., Changery, M. J. and Filliben, J. J., 1979:

"Extreme Wind speeds at 129 Stations in the Contiguous United States," NBS Building Science Service 118, National Bureau of Standards, Washington, D.C.

6. Simiu, E. and Scanlan, R. H., 1978: Wind Effects on Structures, John Wiley and Sons, New York, New York.

7. Simiu, E. and Filliben, J. J., 197.5:

"Statistical Analysis of Extreme Winds," Technical Note No. 868, National Bureau of Standards, Washington, D. C.

8. U. S. Nuclear Regulatory Commission, 1979:

Demographic Statistics Pertaining to Nuclear Power Reactor Sites, NUREG-0348, Office of Nuclear Reactor Regulation,-Washington, D. C.

20

APPENDIX A.

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ENCLOSURE 3 SEP Topic XV-16, "Radiological Consequences of Small Lines Carrying Primary Coolant Outside Containment" is intended to consider the rupture and subsequent radioactive release from lines carrying primary coolant outside containment.

To evaluate the radiological consequences of postulated failure of such lines, the following is requested:

1. Identification of all lines penetrating the containment which contain primary coolant.

2. The line size for each line identified in item 1, above.

3. The flow rate for a rupture in such lines and the assumptions used to determine the flow rate (e.g., the existence of flow restrictors, their location, etc.).

4. The plant locations where the lines traverse and/or terminate.

5. The detection and isolation capabilities of each line break (assuming the postulated break occurs outside containment).

6. The time required to isolate such postulated breaks and the assumptions used in arriving at the time required.

7. The plant areas (where breaks might occur) which are served by ventilation systems utilizing charcoal filters.

8. Whether the filters identified in item 7, above, are used when the plant is at power.

9. Information concerning the charcoal filters, if used (e.g., thickness, etc.).

10. Are any of the plant areas where breaks might occur completely sealed (i.e., no ventilation)?