Maritime transport of Hazardous and Noxious Substances (HNS) has increased for 20 years, involving the risk of major pollution accidents with potentially more hazardous than oil. Chemicals may involve long-term environmental effects and the risks for public safety can be more severe for chemical releases (European Maritime Safety Agency [EMSA], 2007). Approximately 2,000 chemicals are transported by sea and only a few hundred chemicals are transported in bulk, but it represents the main volume of the chemical trade (Purnell, 2009). Alongside the expansion of chemicals transported at sea, incidents involving chemical tankers increased accordingly. Still, information on past and more recent incidents is not easily available. Furthermore, in the case of marine accident involving HNS, spill response is difficult due to the chemicals spilled, particularly when gas or volatile substances are released. The vapour cloud created can be toxic, flammable or explosive and there is a necessity to protect the crew, the population nearby as well as the environment and the stakeholders involved in marine pollution response. As an example, Figure 1 shows a picture of the explosion which occurred in September 2019 in the Ulsan harbour, South Korea. This explosion is the consequence of a styrene monomer leak on the chemical tanker Stolt Groenland that led to a massive explosion with fireball and mushroom cloud. The present report is a literature review on past accidents that have induced the formation of a toxic, flammable or explosive gas cloud. The information gathered will allow better identification of 1) the categories of chemicals most involved; 2) the main risks generated by the gas cloud dispersion in the air and 3) the consequences of a chemical slick on fire at the water surface as well as the hazard due to a vapour cloud explosion. This work is part of WP2: Enhancing knowledge and data on gases and evaporators of the MANIFESTS program (Managing risks and impacts from evaporating and gaseous substances to population safety) that studies risks associated to accidental chemical spills in the marine environment. The aim of this WP is to contribute to a better prediction of the consequences of vapour clouds due to marine accidents. This would facilitate the intervention of marine pollution organisms and would also help to protect population nearby, as we would know precisely where the dangerous area is.
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RBINS Staff Publications 2021 OA
Responding to maritime accidents can be extremely challenging when involving HNS that behave as evaporators. Due to their potential to form toxic or combustible clouds, evidence-based decisions are needed to protect the crew, responders, the coastal population and the environment. However, when an emergency is declared, key information is not always available for all the needs of responders. A case in point is the lack of knowledge and data to assess the risks that responders or rescue teams could take when intervening, or those that could impact coastal communities when allowing a shipping casualty to dock at a place of refuge. The MANIFESTS project aims to address these uncertainties and improve response and training capacities through the development of an operational decision-support system (DSS) for volatile HNS spills. Besides management and communication, the project includes four other work packages: WP2 on collecting new data on evaporators, WP3 on table top exercises and field training, WP4 on improving modelling tools and WP5 on the development of the DSS. Key expected outcomes include: · Operational guidance; · Desktop and field exercises; · In situ training; · Experimental data on gas cloud fate; · A brand-new fire and explosion modelling module; · Improved HNS database with new experimental data on evaporation/dissolution kinetics. This report presents the results obtained in the framework of the task 4.1 aiming at developing tools that would help responders to asses risks in case of explosion and of fire of volatile HNS. The fire module computes the energy flux as a function of the distance to the fire source. It is useful to assess the safety distance at which e.g. a boat can approach a fire while keeping the crew safe. The energy flux can cause burning to people, and start new fire. The burning rate is also estimated. The explosion module computes the overpressure of the shockwave caused by the combustion of a chemical. This overpressure can be very dangerous for people and structure, causing wounds from minor injury to death and destruction of building. The model could be used to predict what could happen in case of the explosion of a stored explosive for instance. The two models are simplifications of the reality and do not take everything into account. Their results can be useful to have a rough idea of what could happen in open sea but should always be interpreted keeping the model hypotheses and limitations in mind. Due to the sensitivity of the topic, the source code of both modules is not made available to public
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RBINS Staff Publications 2021
