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BREEZE Expert

BREEZE Expert is a proprietary model developed by BREEZE to calculate source-term parameters needed by accident release dispersion models.  Both source-term and non-source-term models require observable data to perform calculations. The only difference is whether you or the model perform the calculation of input release conditions.

For BREEZE Expert, the following information is required:

• Chemical
• Storage temperature
• Storage pressure
• Hole size
• Depth of liquid in container above hole
• Maximum pool size
• Meteorological conditions

The calculations performed by BREEZE Expert are designed to provide input to non-source-term models including those in the BREEZE HAZ suite of dispersion models (i.e., DEGADIS, SLAB, INPUFF, and AFTOX). BREEZE Expert requires information about the following physical aspects of the release scenario:

• Vessel shape and dimensions
• Release location and orientation
• Diking
• Chemical database
• Release class
• Release duration, either specified by the user (reaction time) or computed by BREEZE Expert

BREEZE Expert calculates the key model input parameters (e.g., pool evaporation rate, emission rate, etc.) based on user-specified observables such as chemical property data and storage, release, and ambient meteorological conditions. It then recommends an appropriate dispersion model based upon the calculated results and seamlessly transfers these results to the dispersion model. The algorithms in BREEZE Expert are based primarily upon the EPA's document entitled "Guidance on the Application of Refined Dispersion Models to Hazardous/Toxic Air Pollutant Releases", April 1993.

Applicability

BREEZE Expert is designed to perform the source-term analysis portion of an off-site consequence analysis. Users can enter the known conditions of the release and the source-term parameters that are required to run the dispersion models in BREEZE HAZ will be automatically calculated.

The initial step in preparing the input required for any air release model is to gather the observable data; the release’s physical description prior to and at the time of the release. There are two types of models: source-term and non-source term. BREEZE Expert is a source-term model that estimates the gas state of a release entering the atmosphere. It calculates the injection of the gas into the atmosphere and, as gases cool during depressurization, any aerosol that might form to expansion cooling.

In addition to the emission rate, BREEZE Expert also calculates temperature, initial concentration, and initial density parameters. It also calculates the emission rate of a liquid release from a container, and the rate of the gas and aerosol injection into the atmosphere. Non-source term models are models that cannot calculate release conditions based on storage conditions. BREEZE HAZ DEGADIS, SLAB, INPUFF, and AFTOX are non-source-term models that rely on user-defined release conditions. These calculations are performed outside the model. The non-source term model then uses a dispersion algorithm to estimate impacts based on the user-calculated input. These calculations are often very complex and subject to error if extreme care is not used in their derivation. BREEZE Expert eliminates the potential for error, to a large degree, and quickly generates appropriate input to non-source term models.