CERC — Environmental Software and Services

Hazardous releases

CERC has extensive experience in modelling hazardous releases, starting 30 years ago with modelling of the 1987 King's Cross Underground fire for the UK HSE, and continuing with the development of the GASTAR model for dense gas dispersion in 1988 and the liquid spill model LSMS in 1989.

The term 'Hazardous Releases' relates to situations posing an acute risk to human life, which are assessed in the UK under the Control of Major Accident Hazards (COMAH) framework. As part of our consultancy work, we have modelled a large variety of hypothetical hazardous releases including warehouse fires, catastrophic vessel failures and liquid spills, with emitted substances which may be toxic, flammable or explosive. We have also been key partners in projects to determine the best practice for modelling of hazardous releases.

Some accidental releases would not be considered ‘hazardous’, although they may have some human health impacts. CERC has worked behind the scenes on several recent high-profile legal cases relating to fires which were in this category.

CERC have developed a number of software tools for modelling hazardous releases:

  • ADMS 5 contains many features which are useful in the modelling of hazardous releases, although it is not specifically designed as an emergency response model. Features relevant to hazardous releases include modelling of temporally varying source properties, effects of buildings, terrain, varying surface roughness and variable meteorological conditions.
  • ADMS-STAR is a model developed for the analysis of short-term accidental releases. ADMS-STAR combines the ADMS description of the meteorology and boundary layer with a Lagrangian puff approach for modelling the dispersion of explosive and short-duration releases. ADMS-STAR includes the radioactive decay of modelled isotopes and can be used to calculate the amount of material deposited, inhalation dose and gamma dose due to the release. ADMS-STAR also includes a back-calculation mode which can be used to estimate the release parameters from air or deposition samples.
  • ADMS-Puff is a Lagrangian puff dense gas dispersion model designed for modelling accidental and emergency response scenarios involving dense materials. ADMS-Puff is able to model the dispersion of the dense materials with spatially and temporally varying meteorological data.
  • GASTAR is a dense gas dispersion model developed for modelling accident and emergency response scenarios or investigating site safety involving releases of flammable and/or toxic materials from a variety of industrial accidents such as cryogenic spills, catastrophic tank failure, pipe fractures and multi-phase jets.

Source term sensitivity

Defining source terms is an essential part of dispersion modelling. A substance can be released into the atmosphere in many different ways, particularly in accidental release situations. It is important to have an understanding of the sensitivity of the model results to each of the source term input parameters. CERC and GT Science & Software Ltd carried out a ‘High Level Review of the Sensitivity of Dispersion Model Predictions to Individual Source Term Parameters’. This work was funded by the UK Atmospheric Dispersion Modelling Liaison Committee (ADMLC).

The review discusses the main issues of source term sensitivity, describes a range of commonly-used dispersion models, and presents the results of detailed sensitivity tests. The source terms examined in the review include evaporating pools, catastrophic failures of pressurised vessels, jet releases, spray releases, warehouse fires and pool fires. The report describing the outcomes of this review was published in January 2017 and is available for download from the ADMLC publications webpage.

ADMS-Puff development

ADMS-Puff was initially developed by CERC for clients in China. Alongside the features available in the public release of ADMS-Puff, additional features were added allowing the client to use their own flow field data directly in the model.

ADMS-STAR development

ADMS-STAR was initially developed in conjunction with a UK government agency to model the dispersion and deposition of material from accidental releases, including comparisons against maximum permitted levels in foodstuffs. Additional development has been carried out to incorporate new features at the request of clients, including the ability to include the effects of spatially varying meteorology and additional output options.

SMEDIS: Scientific Model Evaluation of dense gas DISpersion models

Between 1998 and 2000, CERC were involved in coordinating the EU SMEDIS project concerned with developing a protocol for the scientific evaluation of dense gas dispersion models. The project had particular emphasis on the complex effects of obstacles, terrain and aerosols often found in real situations, and involved validating the models against field data. CERC’s dense gas model, GASTAR, was one of the models used in the evaluation process.

Project funded by the European Union under the Environment and Climate Research Programme part sponsored by EU.

Learn more

  • Carissimo et al.,2001:The SMEDIS database and validation exercise. 6th International Conference on Harmonisation, Rouen, France, October 1999.International Journal of Environment and Pollution, vol. 16, issue 1-6, pp. 614-629, DOI: 10.1504/IJEP.2001.000654.Article online
  • Daish NC, Britter RE, Linden PF, Jagger SF and Carissimo B,2000:SMEDIS: scientific model evaluation of dense gas dispersion models.International Journal of Environment and Pollution, vol. 14, issue 1-6, pp. 39-51, DOI: 10.1504/IJEP.2000.000525.Article online
  • EU SMEDIS Report Summary. http://cordis.europa.eu/news/rcn/8679_en.html

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