TREATMENT OF CHEMICAL AGENT CASUALTIES NOR NAVSURNLANT SHIPS

File: 082696_doc1_632.txt
Page: 632
Total Pages: 652

                  Computer Simulations of Ammonia ~e1eases
                            in the Al Jubayl Area


       1. The computer simulations that were performed to assess the
       threat of ammonia to various sites in the Al Jubayl area are
       described below. These simulations were performed by Mr. William
       Crean of Rashid Geotechnical and Materials Engineers. Two
       scenarios are considered:  in.the first all of the ammonia is
       released instantaneously and in the second the tank is ruptured
       causing a pool of gas to form. Typical day and nighttime
       conditions are considered. Thus, a windspeed of 7 meters per
       second and a temperature of 20 degrees C is assumed for the
       daytime. A wind speed of 2 meters per second and a temperature of
       16 degrees C is assumed for the nighttime. An inversion layer is
       assumed for the nighttime scenarios.


       2. The simulations of an instantaneous release of ammonia help
       determine the size of the lethal cloud. Simulations of a ruptured
       tank help determine the distance out to which the lethal plume
       extends. These plumes, which appear as shaded portions of the
       figure, depend on the windspeed: a higher windspeed results in
       greater dispersion of the gas. In addition, the plumes remain
-      only as long as there is a pool of ammonia. Thus, the smaller the
       amount of ammonia, the less time the plume persists.


       3. Figure C-i shows the distance out to which life-threatening
       concentrations of ammonia occur if an instantaneous release of
       the gas occurred at the Ibn Baytar plant. The results shown
       assume the release of 1000 MT of ammonia and typical daytime
       weather conditions. The shaded portions of the figure indicate
       areas for which the concentration of ammonia is 500 ppm,  i.e.,
       the IDLH concentration. Thus, harmful concentrations of ammonia
       could be found 7 km downwind from the plant. The cloud itself
       would be 1.6 km at its widest point and any single point in the
       cloud would travel the same speed as the wind (7 km per hour).

       4. Figure C-2 shows the cloud of ammonia that occurs if the
       instantaneous explosion occurs at night. The quantity of gas
       released is 1000 MT. The figure shows that the plume at its
       widest point is 1.9 km. Any single point of the plume moves at 2
       meters per second, the speed of the wind.

       5. Comparison of figures C-i and C-2 reveals that the nighttime
       scenario is more devastating than the daytime scenario. The low
       wind speeds at night cause the gas to disperse less, thereby
       increasing the area of harmful concentrations of ammonia.