Modeling the Outcome of Chlorine Emission Based on Emergency Response Planning Values over 24 Hours Using the PHAST Software (Case Study: Bushehr Nuclear Power Plant)

Background and Aim: Chemical warfare can endanger the security of any country. The present study examined the chlorine gas emission scenario on the outskirts of the Bushehr nuclear power plant over a 24-hour period, so that the study results can be utilized in an emergency response program. Methods: In order to access the data, the area of Bushehr nuclear power plant was investigated in person and then, in order to assess the worst scenario, chlorine was selected due to its extremely high toxicity. From among the existing scenarios, the catastrophic explosion (immediate release) was selected and finally the risk intervals of this scenario were determined to evaluate the impact of chlorine gas on the target population with the use of ERPGs, IDLH and STEL. PHAST 6.7 software has been used for this purpose. Results: Based on the criteria for evaluating the effects of exposure to toxic substances, the results of the present study showed that it is not possible to define an emergency planning area at close distances to the explosion origin by using IDLH and STEL criteria. However, based on ERPG concentrations, the chlorine gas passes shorter distances from 06:00 to 10:00 in the morning to reach the values of ERPG2-3 at 2811 and 1040 meters compared to other time periods studied. Conversely, at night, these distances have the largest risk area based on the values of the above mentioned concentrations at 5212 and 1459 meters, respectively. Conclusion: In order to reduce the vulnerability in accidents, modeling weather conditions based on time periods (morning, noon, evening and night) can be an important tool for planning emergency conditions. Accordingly, it was suggested that the highest risk distance is obtained based on the ERPG1 criterion, i.e. the risk distance based on the lowest concentration of the chemical in the ambient air which does not even make unpleasant odors to be sensed by the residents in the safe areas, especially in similar study zones.