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File: 082696_doc1_645.txt
Computer Simulations of Chlorine Releases
in the Al Jubayl Area
1. This appendix describes the computer simulations that were
performed to assess the threat of chlorine releases to military
facilities in the Al Jubayl vicinity. These simulations were
performed by the Rash id Geotechnical and Materials Engineers
based on data provided by the Saudi Petrochemical Company
(Sadaf). Two scenarios are considered: in the first, the gas is
released instantaneously; in the second, the tank is ruptured
causing a pool of gas to form. Typical day and nighttime
-conditions for the winter months are considered. For example,
windspeeds of 2 meters per second are assumed for the day and 7
meters per second are assumed for the night. Tempertures of 20
and 25 degrees C are assumed for the nighttime and daytime,
respectfully.
2. The simulations of the instantaneous release of chlorine help
determine the size of the resulting lethal cloud. The simulation
produces pictures of the cloud moving in the direction of the
wind, at the same speed. The simulations involving the scenario
( of a ruptured tank help determine the distance out to which a
lethal plume of the gas extends. These plumes depend on the
-~ amount of chlorine in the tank in the sense that the greater the
amount, the longer the duration of the plume. The plumes also
depend on windspeed in that the higher the windspeed the greater
the dispersion of the gas. All simulations were performed
assuming 110 MT of chlorine in the tank.
3. Figure E-1 shows the results of the simulation of an
instantaneous release of all of the chlorine currently being
stored (110 MT) during the day. The shaded portions indicates
areas for which the chlorine concentration is 25 ppm or greater
(the IDLH concentration is 30 ppm). A wind direction of north-
northeast is assumed. Given a windspeed of 7 meters per second,
the initial cloud will reach the port in 26 minutes. If a
southwesterly wind is assumed, the cloud could reach the camp
area in 17 minutes. The cloud diameter regardless of wind
direction is 1.7 km.
4. Figure E-2 shows the same results as figure E-1 except that a
nighttime scenario is considered. In this case, the diameter of
the cloud is somewhat larger (2.5 km vs. 1.7 km). In addition,
because the windspeed at night is lower, the cloud takes longer
to reach certain locations. Thus, depending on wind direction,
the cloud reaches the camp area in 59 minutes and the port in 93
minutes.
5. Thus, the behavior of the cloud is determined primarily by
windspeed (stability of the cloud also is a factor). At nighttime
the cloud has a greater diameter because the slower windspeed
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