Groundbreaking Research on Chlorine Spread

Recent events highlight the need for responders to be prepared with the best information possible for this type of hazard. For instance, in June 2020, dozens of people were treated for chlorine exposure during an incident at a hazardous material storage facility at a U.S. military base in Okinawa, Japan. Another 25 were hospitalized in June after a chlorine gas leak at waterworks in Mohali, India. In July 2020, 70 people were injured by chlorine inhalation after a fire at a power plant in Iran.

“Large scale releases of chlorine have never been tested and studied at the volumes representative of shipments via tanker truck (20 tons) or railcars (90 tons),” said Dr. Shannon Fox, Jack Rabbit II principle investigator and director of S&T’s Chemical Security Analysis Center (CSAC). “Outdoor field testing affords the unique opportunity to study this type of release scenario and directly address critical data and knowledge gaps to improve hazard prediction modeling, emergency response, and industrial safety and security.”

“We do a substantial environmental assessment before the large-scale outdoor release and coordinate with the test site state authority, so no one is injured, and environmental impacts are minimized,” added Dr. Sun McMasters, CSAC physical chemist and current Jack Rabbit program manager.

Special journal issue highlights an extraordinary collaborative accomplishment

The special issue of the Journal of Atmospheric Environment will contain a cluster of 18 articles, with two co-authored by CSAC involving the Jack Rabbit II field and lab tests. Subject matter experts submitted an additional 16 manuscripts presenting summary test results used for model inter-comparisons, results from comparisons of different dispersion models, as well as some results of related research on flow fields around obstructions and chemical reactions with surface materials.

The first CSAC-authored article in the special issue presents an introduction and overview of the Jack Rabbit II field experiments involving releases of 5-20 tons of liquefied chlorine. The article describes the chlorine releases for which the researchers arranged a combination of over 80 shipping containers at the test site to represent an urban area with one- and two-story buildings, capturing the releases with LIDAR (similar to radar but uses laser light instead of radio waves), video and still cameras.

The second article co-authored by CSAC focuses on lab experiments conducted at the University of Arkansas to measure the degree to which plants and soil absorb chlorine to help decrease the spread of the gas. During a release, chlorine reacts with plants, destroying their tissue.

“If you have more vegetation, more soil, more environmental material that absorbs the chlorine, this means there is likely less downwind hazard,” said McMasters. “The purpose of this study was to investigate potential mitigation strategies using environmental materials and learn how much of chlorine can be removed. This will also help modeling better predict the actual spread of chlorine.”

The remaining articles were authored by researchers from the US, UK, Sweden, France, Finland, China and the European Commission. The feature inter-comparison article compares 17 widely-used dense-gas prediction modeling tools using the Jack Rabbit II field trial data (mass release rate, wind speed, wind direction and detection concentrations) with the goal of analyzing hazardous gas releases and identifying gaps to be addressed in future analysis and studies. This will help improve harmonization of the models and provide guidelines to response in the event of a chlorine release.

“The special issue of Atmospheric Environment is an extraordinary collaborative accomplishment that highlights the far-reaching impact of Jack Rabbit II,” said Fox. “This demonstrates and validates a highly successful model of S&T leading a groundbreaking multifaceted program, securing extensive interagency partnerships, and mutually sharing data and resources to greatly enhance the program’s impact and return on investment.”

Jack Rabbit’s Impacts and Future Efforts
The Jack Rabbit research has greatly improved and will continue to improve hazard prediction modeling, emergency planning and response strategies against chemical release incidents. CSAC used Jack Rabbit II findings to update modeling for Pamphlet 74, a product furnished by the Chlorine Institute to help chlorine producers, local emergency planning committees, fire departments and municipalities estimate areas affected by potential chlorine release incidents. Also, the project findings informed the U.S. Department of Transportation’s work related to large-scale chlorine releases, guided improvements to DTRA’s atmospheric transport and dispersion and hazard prediction models, and informed DHS agencies how to train first responders for large chlorine incidents. 

Next year, CSAC researchers will embark on a new round of Jack Rabbit research—Jack Rabbit III—which will focus on developing strategic technology solutions for chemical incident countermeasures, decontamination, protection, emergency response, training and national level exercises. Planned experiments include laboratory, wind tunnel and chamber testing, and large-scale open-field tests with Anhydrous Ammonia, the foundation of nitrogen fertilizers.  

“Jack Rabbit III will expand on previous work and build security, safety and resilience in the chemical supply chain through experimentation over the next five years,” said Fox. “Jack Rabbit III is building on the success of the Jack Rabbit II trials and significant impacts made in securing the homeland from persisting chemical threats.”