ML20071D263
| ML20071D263 | |
| Person / Time | |
|---|---|
| Site: | Clinton  |
| Issue date: | 03/04/1983 |
| From: | ILLINOIS POWER CO. |
| To: | |
| Shared Package | |
| ML20071D255 | List: |
| References | |
| RTR-NUREG-0853, RTR-NUREG-853 NUDOCS 8303090308 | |
| Download: ML20071D263 (34) | |
Text
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HAZARD ANALYSIS OF FLAMMABLE COMPRESSED GAS SIIIPMENTS ON THE ILLINOIS CENTRAL GULF RAILROAD NEAR THE CLINTON POWER STATION (Safety Evaluation Report - Outstanding Issue No. 1)
Illinois Power Company Clinton Power Station - Unit 1
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8303090308 830304 )
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, TABLE OF CONTENTS PAGE
, I. INTRODUCTION 1 II. SITE CONDITIONS 2
. III. BASIC ASSUMPTIONS 2 IV.- PROBABILITY CALCULATION 5 V. CONCLUSIONS 13 VI. REFERENCES 14 LIST OF TABLES 15 LIST OF FIGURES 16 s
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s I. INTRODUCTION The Nuclear Regulatory Commission (NRC) has required an evaluation of the risk associated with rail transportation of hazardous materials in the vicinity of the Clinton Power Station (CPS). The NRC position was stated in the CPS Safety Evaluation Report (NUREG-0853 - Outstanding Issue No.
1):
"The nearest railroad is a line of the Illinois Central Gulf Railroad which runs parallel to State Route 54 and traverses the site approximately 0.75 mile (1.21 km) north of the station. The Illinois Central Gulf Railroad also has a line approximately 3.5 mi F . 6 km) south of the station. The hazards associated with rail transportation of toxic and explosive materials are still being evaluated. Based on 1976 and 1980 transportation data obtained from Illinois Central Gulf Railroad, the applicant has identified several materials req 0 iring further analysis. These will be addressed in a future SER supplement."
It is the purpose of this report to give a detailed discussion of the calculations required to determine the probability of a delayed detonation giving rise to an overpressure greater than 1 psi at the' plant. It will be shown that the probability of such an incident causing an overpressure greater than 1 psi is acceptably low. The methodology used is similar to that used in NUREG-0014 (Reference 1).
Flammable compressed gas (FCG) is transported on the Gilman Line of the Illinois Central Gu?.f (ICG) Railroad which~
passes approximately three-quarters of a mile north of the CPS. In case of an accidental release of FCG into the atmosphere near the station, a hazard to the structural
' integrity of the plant could result. Such a hazard would be from the detonation o,f the FCG with resulting overpressures on the plant structures. According to Regulatory Guide 1.91, overpressures of 1 psi or less are considered safe.
Explosions which give rise to overpressures greater than 1 psi must be anaiyzed further. In particular, the safety of the Seismic Category I plant structures can be demonstrated by showing that they can actually withstand the overpressure of the explosion, or that the probability of such an occurrence is acceptabb/ low.
Regulatory Guide 1.91 provides'a method for calculating the safe stand off distance which insures overpressures of 1 psi or less. For detonations which would occur at any point on the rail line near the station, the separation is sufficient to guarantee overpressures of less than 1 psi and therefore no further analysis is necessary. However, in the case of accidentally released FCG, the formation of a vapor cloud which drifts toward the plant with subsequent detonation is a possibility.
II. SITE CONDITIONS The two rail-lines in the vicinity of the CPS are owned and operated by the ICG Railroad. The ICG line approximately 3.5 miles south of the station is not used to transport hazardous materials. Therefore, no additional evaluation cf this line will be made. Further, the railroad is considering abandoning this line. The ICG line parallel to State Route 54, the Gilman Line, is used to transport numerous commodities including flammable compressed gas. At its closest point, this line is approximately 3,400 feet northwest of the plant. Figure 1 shows the location of the plant and surrounding facilities.
Illinois Power (IP) made a comprehensive survey of the Gilman Line from ICG shipping records for the period of December 1, 1981 to November 30, 1982. During this period, a total of 1673 trains were operated over this line.
Shipments of FCG were identified on shipping records by a 49-05 series Standard Transportation Commodity Code number.
From this survey, summarized in Table 1, 3472 carloads of FCG were shipped via the Gilman Line during the time period studied.
Measurements of local meteorological data were taken over a 5-year period, from April 1972 through April 1977. Joint frequency distribution of wind according to stability class, speed, and direction were taken from the CPS FSAR (Reference 2). The data encompass seven stability conditions (A through G), six speed ranges, and 16 discrete directions.
The stability Categories A through G are defined in Regulatory Guide 1.23. Table 2 defines the various categories.
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After the meteorological measurements were taken, a man made lake, Lake Clinton, was formed. Lake Clinton surrounds three sides of the plant and covers approximately 5,000 acres. Most of the year the temperature of the lake is greater than the surrounding air. Therefore, it would have a destabilizing effect on the air mass. That is, the air layer in contact with the lake would be heated and would tend to rise, thus causing additional movement. Since any escaping gas would be dispersed faster in increasingly I unstable air, the lake would probably reduce the potential for a damage-causing explosion. For conservatism, any effects of the lake are disregarded.
III. BASIC ASSUMPTIONS In this study, the hazard due to the transportation of FCG is considered. The railroad transports numerous gases in
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this category. However, for this case, propane was chosen as the representative cargo. It was further assumed that the liquefied propane was transported in tank cars holding 160,000 lbs. of the fuel (Reference 3).
A loaded tank car loss of lading rate was determined in an Association 6 of American Railroads Report (Reference 4) to be 0.152 x 10 loss of ladings per tank car mile. This spill rate is based on data from 1965 through 1970 (6 years) where a total of 49 loss of lading accidents were observed.
During this period, the average loaded pressurized tank car traffic (flammable gases) was 5.38 x 10 car miles per year (from 1% Waybill statistics) . Thus, the nationwide
. loss of lading rate for loaded tank cars was:
-6 Pr= 49 accidents = 0.152 x 10 accidents (3.1) 5.38 x 10 7 car miles x 6 years year A detonation _{ ate given a loss of lading was determined to be 1.11.x 10 explosions / accident using a review of the University of Southern California report (Reference 5) AAR -
RPI reports (References 6,7), FRA report (Reference 8) and DOT reports (Reference 9). The determination of this value is from an analysis of LPG tank car accident data from the period of 1965 through 1977 (13 years). During this time period 163 losses of ladings caused by mechanical damage resulted in three explosive incidents. This type of incident could be caused by a major rupture of the containment vessel resulting in a gross spill without ignition. The result could be the formation of a very large vapor clcud. If this cloud would be ignited after an explosive fuel-air mixture had been formed, a maximum incident explosion could result. This type of incident is
__ characterized by an unconfined fuel / air detonation. In addition to mechanical damage induced loss of lading, exposure to fire can lead to an explosive incident. From an analysis of LPG tank car accident data for the period of 1965-1970 (6 years) , 49 losses of ladings caused by fire resulted in no explosive incidents.
Thus, the nationwide detonation rate given a loss of lading for FCG is:
3 explosions /13 years + 0 explosions /6 years P (D/ R) = (3.2) 163 accidents /13 years + 49 accidents /6 years
-2 explosions
= 1.11 x 10 accident
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NUREG/CR-0075 by.Eichler & Napadensky (Reference 10) contains information on accidental discharge of gases from tank cars. In that report, puncture hole sizes of 23-1/2" and 7-1/2" in diameter were recommended for analysis purposes. Openings of this size would discharge gas at the constant rates of 2,667 lbs/second and 266.7 lbs/second, respectively. In.this work, a 14-1/2", opening and a-4-3/4" opening were also used. The'latter two have corresponding gas release. rates of 888.9 lbs/second and.102.6 lbs/second, respectively. A summary of the assumed puncture hole sizes, release rates, and durations of release are given in Table
- 3. In the analysis, it'was assumed that as the liquefied gas escaped, it immediately flash-vaporized in its entirety.
This is a very. conservative assumption since only about one-third of the contents would vaporize immediately, with the remainder staying as liquid droplets (Reference 10).
In evaluating the detonation potential of the escaping gas, it was assumed that the limits of flammability for propane are between 2.8% and 7% by volume of the gas-air mixture.
To assess the probability of a detonation, given that an accidental discharge of FCG has occurred, a negative exponential probability density function for ignition time was used. That is, the probability,of detonation between time equal to T 7 and time equal to T is given by the 2
following expression:
Pd (Ty,T2 ) = 'exP (-T1 /S)-exP(-T 2/p) (3.3) where p is the mean time to detonation.
When applying Equation (3.3) eight discrete time intervals were selected such that for a given rupture size, the time range covered the time needed to discharge the contents of the tank and to dissipate the flammable concentrations of gas. In all cases, the range was increased until the
' computed probability showed no increase for the increase in total time. Based on the observed time to ignition reported in Reference 8 for two rail tank car accidents, the mean time to detonation used in the analysis is nearly 300 seconds. In addition, for the 23.5- and 14.5-inch diameter ruptures, average times to detonation of 90 and 120 seconds, respectively, were used in the analysis because of rapid dumping of tank contents at these rupture sizes.
In order to evaluate the overpressure from an explosion of FCG, it was necessary to convert the explosive potential of the gas to that of TNT. According to Regulatory Guide 1.91, the product of 2.4 times the weight of the hydrocarbon involved will give an equivalent weight of TNT. . Based on an equivalent weight of TNT and assuming ground level detonation, the' distance from the explosion beyond which the overpressure will not exceed 1 psi is given in Regulatory Guide 1.91 as:
1/3 r
b = 45W (3.4) where: r separation for 1 psi or less (ft)
Wb == equivalent weight of TNT (lbs)
IV. PROBABILITY CALCULATION In this section, a step-by-step procedure is used to explain the calculation of.the probability of exceeding the 1 psi overpressure at the plant due to an accident on the ICG Railroad. As each step is explained,. numerical examples are used for clarity.
A. Division of Railroad into Segments An approximately 2.6-mile-long section of the railroad line just north of the plant was considered. This portion of the line was used because preliminary calculations indicated that using a longer section would not make a significant contribution to the hazard probability. The 2.6-mile portion was divided into 26 segments of varying lengths: 300, 400, and 800 feet. While an accident is equally possible at any point in any of the segments, it was assumed that an accident would occur at the point in each segment which was. closest to the plant. As an example, consider Segment 8 (see Figure 2). The segment is 400 feet in length; therefore, the probability that an accident occurs in the segment within a year is computed as follows:
P -6 a = 0.152x10 accidents x 400 ft x 1 miles car mile 5280 ft
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x 3472 FCG cars = 4.00x10 accidents (4.1) yr year If a detonation were to follow an accident right at the 1 point of accident on the railway line, the resulting overpressure at the plant would be less than 1 psi. To see this, consider the location of the assumed accident point on Segment 8. Its distance from the plant is given by:
2 2 r= )2350 + 2650 = 3542 ft (4.2)
. In addition, the stand off distance prescribed by Regulatory Guide 1.91 is found to be:
r = 45 (160,000 x 2.4) 1/3 = 3271 ft (4.3) b Since the stand off distance is less than the actual
distance to the assumed point of accident on the line, the conditions of Regulatory Guide 1.91 are fulfilled and there would be no additional concern. Since the rail line is approximately 3400 feet from the plant at its closest point, the safe stand off distance is always less than the actual distance to the assumed point of accident. However, in the case of a material such as propane, the possibility of a vapor cloud moving toward the plant and subsequently exploding must be examined. To do this, a study of cloud diffusion dynamics is necessary.
B. Cloud Dynamics As the propane esca' pes from the damaged tank car, it is assumed that turbulent mixing with the air occurs. It is further assumed that the entire amount of released propane vaporizes immediately. The resulting cloud then moves with the prevailing wind. As the cloud moves away from the source, it diffuses so that the concentration becomes less and leas. The concentration of vaporized propane at any point downwind from the accident point is given by the following expression:
2 2 Y (x,y,z) --
Q exp ( y z ); u (t-T) f: xi ut (4.4)
I"y #z 2ry 2- 2 ozz
= 0 x4u (t-T) and x >ut where the following symbols are used:
Y = gas concentration 0 = gas release rate (ft 3/sec) u = wind velocity (ft/sec) -
x = distance downwind (ft) y = horizontal distance normal to drift direction (ft) z = vertical distance normal to drift direction (ft) er = dispersion coefficient in horizontal Y
direction (ft) cr* = dispersion coefficient in vertic 'icection (ft) t = time after initial rupture (sec)
T = time required for total content of car to be released (sec)
The previous expression represents the distribution of l concentration _ associated with a Gaussian Dispersion I Process. The diffusion coefficients e and r, depend on the distance the vapor has tEavelled from the -
source and are given graphically in Figures 3 and 4 ,
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5 1
(Reference 1). From an examination of the dispersion equation itself and the curves showing the dispersion coefficients, it is evident that the vapor concentration at any point is dependent upon wind speed, wind stability class, and time after the initial discharge of gas. In this analysis, calculations were made for each stability class and for each wind speed range. The average speed was used for each of the first five speE3 groups. A speed of 36.7 fps (25 mph) was used for the highest speed range.
The calculations were carried out for several different total time durations. Hazard probabilities were calculated for a given qas discharge rate and mean time to ignition, increasing the total time on each successive cycle. Although the cloud formation and drift are continuous processes, the numerical computations were only carried out for discrete time points. Flammable gas volumes and centroid drift distances were calculated at eight times over the duration. The probability of detonation was also evaluated for eight time intervals, the intervals being chosen such that the times of flammable volume and centroid travel calculation fell at the mid-points of
-the intervals. Figure 5 gives an example of the time steps used in a 1600 second total time calculation.
It is noted from Figures 3 and 4 that the dispersion coefficients a and a are dependent upon the distance from Ehe soufce. Since the curves representing the coefficients do not admit values for zero distance from the source (that is, at the source itself) , a device is needed which will allow use of the dispersion equation in conjtmetion with the dispersion coefficient curves and still yield a concentration of 100% at the source. lu3 device most often used to accomplish this is the computation of a virtual source distance. That is, it is assumed that a source exists somewhat behind the actual source. The actual distance between the real source and the virtual source is chosen to give dispersion coefficients which, when utilized in the dispersion equation, give a 100%
concentration on the centerline at the source.
For example, consider wind stability Class D and wind speed of 7.4 fps. If the dispersion coefficients are assumed equal at the source, then a straightforward calculation shows that if the discharge rate is 2667 lbs/second, the dispersion coefficients must be equal to 22.3 feet:
y (0,0,0) = Q (Reference 1) (4.5) 2 27ucr
where o-y = o-z = o- It follows that:
26 1.0= I 0.671154) (4.6) 2 27(7.4)r where a specific weight of 0.1154 lb/ft 3 is assumed for propane.
Hence:
o= 22.3 ft. (4.7)
Note that in the proceeding calculation the factor 27 appears in the denominator, while in Equation 4.4, the factor is 7r . Equation 4.4 is intended for the calculation of concentrations at spatial points located at distances from the source which are much greater than the elevation of the source above ground.
In that case, the ground surface forms a boundary preventing diffusion downward. On the other hand, when determining the virtual source location, it is assumed that diffusion occurs in all directions normal to the cloud drift direction.
The lateral diffusion coefficient is given in the form:
y = 0.18 x 0.825 8'
(4.8)
= 22.3 ft, the distance to the virtual Since source o'ls given by:
1 0.885 d
Y
= 22.3 =232 ft (4.9)
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(0.18 I Even though the graphical representation of the variation of dispersion coefficient in the. vertical direction is not a set of straight lines, as is the case for the lateral dispersion coefficients, the same form.of analytical expression was still used to approximate the vertical dispersion coefficients.
Specifically, the form of the variation for wind stability Class D may be written as:
0.825 (4.10) og = 0.13 x Using the same steps as before, it is determined that the virtual source distance for computation of the vertical dispersion coefficient is approximately 511 feet. In aubsequent calculations for this wind
stability class and wind speed, the two distances just calculated must be added to the actual distance from the source when determining the two dispersion coefficients. Values used for calculating o and og for all wind stability classes are given En Table 4.
The dispersion equation allows computation of the concentration of the gas at any location downwind from the assumed point of tank car puncture. Figures 6 and 7 show contours of concentration at ground level and in a vertical plane passing through the centerline of the cloud. Using contour data of this type, the volume contained in the flammable region and the downwind centroid location of this volume can be calculated.
The volume of flammable gas and its downwind location of the centroid are shown on each curve. Similar curves can be calculated for each different combination of wind stability class, wind speed and time. It is noted that no rise of the centroid of the gas volume is considered. That is because propane has a greater density than air and therefore will not be lifted by buoyant force. It is further noted that in case of gases which are lighter than air, such as natural gas, a rise of the entire cloud, independent of the upward diffusion, would be taken into account.
C. Critical Wind Directions For a given wind stability class, wind direction, and time, a flammable volume of gas and a downwind centroid location can be obtained as shown in the previous section. The next step in the analysis is to convert the flammable gas volume into an equivalent weight of TNT. The volume is multiplied by the specific weight of progane (in this study it was taken to be 0.1154 lbs/ft ) and subsequently multiplied by the 2.4 equivalency factor stated in Regulatory Guide 1.91.
Next, the equivalent weight of TNT is used in the stand off equation given by Regulatory Guide 1.91 to determine a 1 psi explosion radius, that is, a radius within which the overpressure will be at least 1 psi if the calculatod gas volume were to explode. Since the centroid of the detonating gas volume is displaced downwind from the source of gas release, a geometric calculation will show whether the centroid lies inside or outside the 1 psi damage circle. Figure 8 shows the various items involved in calculations of this type.
For Segment 8 the point of assumed accident is located 2,350 feet west and 2,650 feet north of the. nearest plant structure. For stability Class D, a wind speed of 7.4 fps and for 520 seconds following the break, a flammable gas volume of 17,350 cubic feet is formed, and the centroid of the flammable volume is located
3,600 feet downwind from the point of break.
Consequently,theweightofgasjnvolved,basedona specific weight of 0.1154 lbs/ft , is approximately 2,002 pounds. The equivalent weight of TNT is 2.4 times the weight of gas or 4,805 pounds. It follows that the 1 psi damage radius obtained on the basis of the equation from Regulatory Guide 1.91 is:
1/3 = 757 feet r
b = 45 (4805) (4.11)
From Figure 8 it can be seen that for wind directions between 306' and 331* the centroid of the exploding gas will fall within the 1 psi damage radius. For all other wind directions the centroid will fall outside the 1 psi radius. Figure 9 shows that for the range of winds giving an unfavorable result (that is, causing the centroid to fall wi'hin the 1 psi circle), only the northwest and north-northwest sections need be considered. Reference 2 gives the probability of wind from all directions for the six wind speed increments for stability Class D. For winds in the speed range of 1.5 to 3.0 meters per second (average 7.4 fps) , it is observed that the probability of winds from the northwest is 0.41% and for wir2ds from north-northwest it is 0.38%. Therefore, the total probability of having winds from a direction which will cause the centroid of the detonating gas to be inside the 1 psi damage radius is 0.79%.
Next, the probability of detonation at the time under consideration is calculated. In the case under consideration here, the average time to detonation is taken as 300 seconds. Therefore, the probability of detonation in the time interval between 410 seconds and 610 seconds following detonation is given by the following:
P d
= exp(-410/300)-exp(-610/300) = 0.1241 (4.12)
D. Combined Probability for a Single Segment The following probabilities are now used to obtain the results for Segment No. 8:
Probability of an accident in Segment 8 = 4.00 x 10-Probability of unfavorable wind direction = .0079 Probability of detonation given an accident = 0.0111 Probability of detonation in time interval = 0.1241 Finally, the product of the four probabilities just stated is the probability that a detonation will occur on Segment No. 8 during wind of stability Class D, with speed of 7.4 fps in the critical directions and that detonation will occur in the 410 to g10 y second time interval. The result is 4.35 x 10 per year.
E. Total Probability of an Explosion Hazard Using the same steps.just presented for all segments, wind stability categories, wind speeds and time intervals, then summing the results gives the total probability of an explosion hazard at the plant.
The result is expressed formally by:
NP 7 6 NT 16 P = Pr xP(D/R) x F x T F) '
) Py (S ,V,D)xPd(T 7_y ,T y)xL(N)xd(S,V,D,I,E N=1 S= V=1 I=1 D=1 where:
P = probability of rupture per tank mile PTD/R) = probability of detonation (explosion) given a rupture F = frequency of shipment of tanks carrying FCG, in shipments per year P"(S,V,D) = probability that wind of stability class S, speed V, and direction D is blowing when detonation occurs P d(T _y'T ) =
7 7 probability that detonation occurs between times T and T given that a rupture das occurfe,d L(N) = length of railroad segment N, in miles NP = number of railroad segments considered in analysis NT = number of detonation time intervals d(S,V,D,I,N):
= 1 if overpressure exceeds the one psi criterion for S,V,D,I,N
= 0 if overpressure does not exceed the one psi criterion Each total probability calculation must be based on:
a) gas discharge rate b) mean time to detonation c) total time after puncture occurs As indicated earlier, four different discharge rates corresponding to four different size puncture holes were considered. In addition, the mean time to detonation was varied between 90 and 300 seconds and the time following rupture of the tank was varied from 900 to 3120 seconds, depending on the time required to empty the tank of its contents. Table 5 gives a list representative of the cases studied, including the worst cases. This list shows the results for a series of assumed conditions. As shown by the two cases in Table 5, the maximum probability calculated for all of
, .m- . - . , - - . - _ -
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the cases studied was 2.3x10 per year and was distributed over the 26 segments of the rail line as-shown in Table 6. AccordingtoRegulatoryGuide1.gl, ~
this probability is sufficiently low, less than 10 per year, provided conservative estimates were used.
The following conservatisms were used in the evaluation:
- 1. The entire contents of the tank has been assumed to flash-vaporize. Actually, only 1/3 of the contents might vaporize, the remaining 2/3 staying in the form of liquid droplets.
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- 2. Destabilizing effects of the lake have been neglected.
- 3. No rise of the plume due to buoyancy has been assumed.
- 4. The equivalent weight of TNT has been taken as 240% of the gas contained in the flammable cloud region. Regulatory Guide 1.91 indicates that the 240% reptasents an upper limit for hydrocarbons.
- 5. The safe overpressure for the safety-related structures has been taken as 1.0 psi, whereas the maximum safe overpressure for CPS is 1.65 psi, which is one-half the total tornado wind design load of 3.3 psi.
- 6. Statistics used for tsnk car accidents rates have been taken from a time period (1965-1977) before recently mandated design changes,were completed.
Specifically, tank cars used to transport flammable combustible gases are mandated by 49CFR173 and 179 to have a combination of the following safety features: coupler restraint systems, tank head puncture resistance systems, thermal protection systems, and safety relief valves. Tank cars not built with the mandated safety features were required to be backfitted under a timetable (1977-1982) specified in 49 CFR.
- 7. Exceeding the specified overpressure will not necessarily cause any radioactivity release, much less one sufficient to exceed 10CFR100 guidelines.
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l V. CONCLUSIONS This study evaluated the effects on the Clinton Power l Station of the accidental discharge and detonation of flammable compressed gases transported by the Illinois Central Gulf Railroad. Using conservative estimates, the probability of egceeding a 1 psi overpressure was shown to be less than 10 per year. According to Regulatory Guide 1.91, this probability is sufficiently low and, therefore, the hazards associated with FCG shipments near CPS do not need to be considered as design basis events.
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l VI. REFERENCES
- 1. NUREG-0014, " Safety Evaluation Report for Hartsville Nuclear Plants," April 8, 1976,
- 2. Clinton Power Station, Final Safety Analysis Report, Tables 2.3-15 through 21, " Joint Frequency Distribution, Distribution of Wind Directions and Speeds".
- 3. Considine, D. M., Energy Technology Handbook McGraw-Hill, 1977.
- 4. " Final Phase 02 Report on Accident Review", Railroad Tank Car Safety Research and Test Project, Association of American Railroads and Railway Progress Institute, Report No. RA-02-2-18. August, 1972.
- 5. Jones, G. P., et al, " Risk Analysis in Hazardous Materials Transportation," report by the University of Southern California Institute of Aerospace Safety and Management for the Department of Transportation, NTIS Report No. PB-230 810, March 1973.
- 6. " Phase 02 Report on Dollar Loss Due to Exposure of Loaded Tank Cars to Fire - 1965 through 1970,"
Association of American Railroads and Railway Progress Institute, Report No. RA-02-1-10, August 11, 1972.
- 7. " Final Phase - 01 Report on Summary of Ruptured Tank Cars Involved in Past Accidents," Association of American Railroads and Railway Progress Institute, Report No. RA-01-2-7, July 1972.
- 8. Federal Railroad Administration. " Unpublished Summary List of Tank-Car Accidents--Hazardous Materials Section."
- 9. " Hazardous Material Incident Reports," Material Transportation Board, DOT.
- 10. Eichler, T.V. and H. S. Napadensky, " Accidental Vapor Phase Explosion on Transportation Routes Near Nuclear Power Plants," report prepared for the NRC, NUREG/CR-0075, April 1977.
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A List of Tables Table Title 1 Flammable Compressed Gas Shipments Over the Illinois Central Gulf-Gilman Line, 12/1/81 to 11/30/82.
2 Classification of Atmospheric Stability 3 Puncture Size and Related Gas Release Quantities 4 Analytical Representations for Dispersion Coefficients i
.5 Probability of Exceeding 1 psi Overpressure Based on Various Assumed Conditions 6 Contribution of Each Railroad Segment to Total Probability i
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. - _ . - - , - ~ - , ,m._.- - - . , _ . , _ , ,, . _ _ _ m , . . - . -
TABLE 1 FLAMMABLE COMPRESSED GAS SHIPMENTS OVER THE ILLINOIS CENTRAL GULF-GILMAN LINE, 12/1/81 to 11/30/82 STCC No. Description of Commodity Carloads Tons 4905702 Butane (butane, impure for further 9 675 refining) 4905703 Butadiene, inhibited (butadiene, 1 75 impure for further refining) 4905706 Butane. 443 31,146 4905707 Liquefied Petroleum Gas (butene gas, 345 24,459 liquefied) 4905711 Liquefied Petroleum Gas (butylene, 13 875 impure for further refining) 4905741 Liquefied Petroleum Gas (NIC) 1 75 4905747 Isobutane 793 57,001 4905748 Isobutylene 1 75 4905750 Isobutane (Isobutane for further 8 523 '
refinery processing) 4905752 Liquefied Petroleum Gas 885 61,816 4905761 Methyl Chloride 3 141 4905781 Propane 164 11,559 4905782 Propylene 801 57,132 4905785 Trifluorochloroethylene 1 75 4905792 Vinyl Chloride 4 300 Total 3472 245,927 STCC: Standard Transportation Commodity Code NIC: Not in Code - commodity was coded with a STCC number which could not be identified from the STCC tariff. Commodity was assumed to be of the same family of nearest identifiable commodity by STCC number.
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Table 2 Classification of Atmospheric Stability Stability- Pasquill Temperature change Classification Categories #*
0 with height (OC/100m)
Extremely unstable A 25.00 -1.9 Moderately unstable B 20.0 -1.9 to -1.7 Slightly unstable C 15.0 -1.7 to -1.5 ->
10.0 Neutral D -1.5 to -0.5 Slightly stable E 5.0 -0.5 to 1.5 Moder cely stable F 2.5 1.5 to 4.0 Extremely stable G 1.7 4.0
- 6 - Standard deviation of horizontal wind direction fluctuation over a period of 15 minutes to'l hour.
1
- . =
Table 3 Puncture Size and Related Gas Release Quantities Puncture Release Discharge Diameter Rate Time (in.) (1bs./Sec) (Sec.)
23 2667 60 14 888.9 180 7% 266.7 600 4 3/4 102.6 1560 0
Table 4 Analytical Representations for Dispersion Coefficients B* B
- STABILITY #
y 7 "Z ~^*
Z CLASS A B A B y y z z A 0.52 0.885 0.031 1.27 B 0.39 0.885 0.097 1.02 C 0.27 0.885 0.097 0.95 D 0.18 0.885 0.13 0.825 E 0.14 0.885 0.097 0.815 F 0.094 0.885 0.058 0.815 G 0.052 0.900 0.038 0.815
- x,o ,og in feet y
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4
Table 5 Probability of Exceeding 1 psi Overpressure Based on Various Assumed Conditions 3
Mean Detonation l
Discharge Time Duration Time Probability (Min.) (Sec.) (Sec.) (per yr.)
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26 3120 300 l'. 7 x 10 '
-8 1 180 300 5.1 x 10 10 1200 300 -
- 1. 5 x 10~
-8 1 180 90 ,6. 6 x 10 3 '400 120 ;2. 9 x 10 -8 1 600 90 1. 3 x 10~
1 900 300 2. 3 x 10~
3 1500 300 1.1 x 10-1 1125 300 2. 2 x 10~
~
1 1500 300 2. 3 x 10~
1"DischargeTime"isdefIneda'sth'etimerequired,fromwhen the car is punctured, to release the entire contents of the car.
2 " Duration" is total time modeled by the computer program,.taken
~
from when th2 car is punctured.
3 "Mean Detonation Time" is defined as the mean time elapsed, from-when the car is punctuted, until a detonation occurs.
+
.o TABLE 6
, 'QONTRIBUTION OF EACH RAILROAD SEGMENT TO TOTAL PROBABILITY Duration: 1500 seconds Mean Duration Time: 300 seconds Segment Contribution Number (%)
1 ' -
1.0 1
2 2.9 3 3.9 4 3.3 5 4.0 6 3.4 7 5.5 8 6.4 9 6.0 10 7.6 11 8.3 12 8.2 ,
13 6.6 14 5.2 15 4.8
~
16 4.2 17 3.5
- 18 2.4
- ~
19 2.8 4
20 s. 2.5 I 21 2.7 1
22 2.2 23 1.2 24 0.7 25 0.4 26 O.3 TOTAL 10 0. 0 - = 2. 3 ~ x 10-7 per year d
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e , -y - . - . - - - - ,- -,n-- n ,,,.___,,,.-,--,n._., , -,,,,,.-w-, -
List of Figures Figure Title 1 Site Plan 2 Isolated Segment 8 of Railroad Line 3 Horizontal Dispersion Coefficients 4 Vertical Dispersion Coefficients 5 Time After Rupture for Calculation of Flammable Volume and Centroid Location; Time Intervals for Probability of.
Detonation Calculation, 1600 Second Duration 6 Ground Level Concentration at 520 Seconds After Rupture 7 Concentration in Vertical Plane at Centerline of Cloud 520 Seconds After Rupture 8 Geometric Considerations for Unfavorable Wind Direction 9 Determination of Applicable Wind Directions. .
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i Figure 1 - Site Plan f
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N 1 iL POINT OF = 2550'
=-
%NK RUPTUltf D ,
d 1
SEGMENT 6 1.ENGTH = 400' N
P PLANT Figure 2: Isolated Segment 8 of Railroad Line 4
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D - NEUTRAL
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l 10 g_g
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8 10 2 S 10* 2 5 10 DISTANCE FROM SOURCE Iml Figure 3: Horizontal Dispersion Coefficients
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_ . 10 2 5- f0 2 5 to" 2 5 40' DISTANCE FROM SOURCE tm)
Figure 4: Vertical Dispersion Coefficients
F CALCLtLATICN TIMES FOR
, FLAMMABLE VOLUME MD CENTRotD, SEC.
A TIME, SEC. O E
' tw v 0 - - 3 -j V
PROBA&lLITY OF PETONATION TLME INTERVALS , SEC.
Figure 5: Time After Rupture for Calculation of Flammable Volume and Centroid Location; Time Intervals for Probability of Detonation Calculation, 1600 Second Duration
~
4
i .
f.4 %
ll S00 a
20%
al -
u 200 Z
l00 ME FLAMMAsut SOURCEy ,f
/
S400 b500 bbOO 5700 S600 5000 SYMMETRIC ABOUT 4 DOWNWIND DISTANCE 3 ft.
l00 -
200 _
500 -
Figure 6:
Ground Level Concentration at 520 Seconds Aft.er Rupturc
n-g@
N f.4 %
$ 7.0 %
e 5 loo 3 ?.6 % CENTRotD y .%MMMblE N
, Y/// z
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souncal woo asoo w stoo e seoo DOWHWIND DISTANCE, fl.
Release Rate 2667 lb/sec.
._ ' Wind Stability Class: D Wind Velocity: 7.4 fps Figure 7: Concentration in Vertical Plane at Centerline of Cloud 520 Seconds After Rupture.-
t
=
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fotNT OFTAWK RunuRE. N
~ji SEGMENT No. 8 N 4, 2 o
8 N
ES.7*
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r-
=
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Release Rate: 2667 lbs/sec
/N Mind Stability Class: D Tb=757'__
Wind Speed: 7.4 fps
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Figure 8: Geometric Considerations for Unf avorable Wind Direction I
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