Atmospheric Release Advisory Capability Research Articles

The use of an operational model evaluation system for model intercomparison

This paper describes a prototype model evaluation system for the study of the capabilities and performance of operational atmospheric transport and dispersion models. This system provides tools both for objective statistical analysis using common performance measures and for more subjective visualisation of the temporal and spatial relationships of model results relative to field measurements. Supporting this system is a database of processed field experiment data (source terms and meteorological and tracer measurements) from over 100 individual tracer releases. The use of this system is illustrated using results from models that are used operationally by the Atmospheric Release Advisory Capability (ARAC) emergency response system, as well as new models currently being developed.

ARAC and its Modernisation

The Atmospheric Release Advisory Capability (ARAC), located at Lawrence Livermore National Laboratory, has embarked on a multi-year modernisation effort that began over two years ago and is now well under way with full completion expected by the year 2000. The modemisation involves a new computer system, improved three-dimensional diagnostic flow and atmospheric dispersion models, and a completely new mesoscale prognostic atmospheric modelling capability. Terrain representation in the atmospheric transport flow and dispersion models will be continuous rather than the block-terrain representation in the earlier models. A UNIX-based distributed computing architecture will be the underlying framework for the 3-D visualisation tools, interactive graphical user interface applications, communications software, file management, database management, and modelling environment.

Atmospheric lab

A new $11.3 million Atmospheric Emergency Response Facility is under construction at the Lawrence Livermore National Laboratory in Calif. The facility, which will take 18 months to build, will house Livermore's Atmospheric Release Advisory Capability (ARAC) and research components of the Regional Atmospheric Sciences (RAS) division, which have been housed in trailers for the past 17 years. Along with studying the effects of episodic releases of hazardous materials in the atmosphere, the RAS division also is working on developing atmospheric models on a variety of space scales.

Atmospheric Release Advisory Capability: Real-Time Modeling of Airborne Hazardous Materials

The Atmospheric Release Advisory Capability (ARAC) at Lawrence Livermore National Laboratory is a centralized federal project for assessing atmospheric releases of hazardous materials in real time. Since ARAC began making assessments in 1974, the project has responded to over 60 domestic and international incidents. ARAC can model radiological accidents in the United States within 30 to 90 min, using its operationally robust, three-dimensional atmospheric transport and dispersion models, extensive geophysical and dose-factor databases, meteorological data acquisition systems, and experienced staff. Although it was originally conceived and developed as an emergency response and assessment service for providing dose-assessment calculations after nuclear accidents, it has proven to be an extremely adaptable system, capable of being modified to respond also to nonradiological hazardous releases. In 1991, ARAC responded to three major events: the oil fires in Kuwait, the eruption of Mt. Pinatubo in the Philippines, and an herbicide spill into the upper Sacramento River in California. Modeling the atmospheric effects of these events added significantly to the range of problems that ARAC can address and demonstrated that the system can be adapted to assess and respond to concurrent, multiple, unrelated events at different locations.

Dose Estimates from the Chernobyl Accident

The Lawrence Livermore National Laboratory Atmospheric Release Advisory Capability (ARAC) responded to the Chernobyl nuclear reactor accident in the Soviet Union by utilizing long-range atmospheric...

The Current Status of ARAC and Its Application to the Chernobyl Event

The Atmospheric Release Advisory Capability (ARAC) project, developed by the Lawrence Livermore National Laboratory (LLNL), provides real-time dose assessments and estimates of the extent of surface contamination that may result from an atmospheric release of radioactivity. It utilizes advanced computer-based data communication and processing systems to acquire the meteorological and source term information needed by the three-dimensional atmospheric dispersion models to derive the consequence assessments. The ARAC responded to the recent Chernobyl reactor accident in the Soviet Union by estimating the source term and the radiation dose distribution due to exposure to the radioactive cloud over Europe and the Northern Hemisphere. This analysis revealed that approximately 50% of the estimated core inventories of 1-131 and Cs-137 were released. The estimated committed effective dose equivalent due to inhalation of radioactivity during cloud passage is of the order of 10 mrem within parts of Scandinavia and eastern Europe, while most of the populations within central Europe were exposed to levels ranging from 1-10 mrem. The amount of Cs-137 released by the Chernobyl accident far exceeds that released by previous reactor accidents, but is only about 6% o of the Cs-137 produced by the atmospheric weapon testing programs.

'No Place to Hide'—Computer Models Track

THE BIG SPONGE is what initiates call ARAC—the Atmospheric Release Advisory Capability—and it is vital to the clean-up after a nuclear accident. But this sobriquet doesn't refer to a propensity for mopping up radiation. It alludes to ARAC's ability to soak up data on weather conditions, regional geography, and the release of radionuclides into the atmosphere at thousands of sites around the globe. ARAC is a contingent of about 30 physicists, meteorologists, electronic engineers, computer scientists, and technicians who work at the Department of Energy's (DOE) Lawrence Livermore National Laboratory across the bay from San Francisco. It was initiated in 1974 and beefed up considerably after the accident in a nuclear power plant at Three Mile Island (Pa) in 1979. The ARAC staff employs computer models to estimate the extent of surface contamination as well as radiation doses to population centers after hypothetical or real nuclear accidents. ARAC works fast.

Atmospheric Release Advisory Capability (ARAC) Response to the Three Mile Island Accident

This paper discusses the three general classes of support provided by the Atmospheric Release Advisory Capability (ARAC) and describes the role played by ARAC in support of DOE during the Three Mile Island accident in March and April of 1979.

Atmospheric Release Advisory Capability (ARAC): Update 1977

The Atmospheric Release Advisory Capability (ARAC) is a service to facilities requiring a means of realtime prediction of the extent of health hazards that may result from a release of radionuclides or other toxic materials. The ARAC system, sponsored by the Department of Energy (DOE), consists of a network of serviced facilities and a central facility at the University of California, Lawrence Livermore Laboratory (LLL). Since 1973, when the concept was initiated, a joint feasibility study of the ARAC system has been conducted by LLL and the Savannah River Laboratory (SRL) and research and development was initiated to implement this service for DOE nuclear facilities. The present system of three sites (LLL, Savannah River Plant and the Rocky Flats Plant) is now being tested and evaluated with the Mound Laboratory scheduled to join the network in the fall of 1977. Plans are presently being formulated to implement the ARAC service for additional DOE sites during the next several years. This article briefly describes the ARAC concept, discusses progress to date and outlines future plans for completing the system's development and operating the service.

Atmospheric Release Advisory Capability (ARAC)

ARAC is in the initial stages of being implemented and is therefore susceptible to changes before it reaches its final form. However the concept of ARAC is fully developed and was successfully demonstrated during a feasibility study conducted in June 1974, as a joint effort between the Savannah River Laboratory (SRL) and LLL. Additional tests between SRL and LLL are scheduled for December 1975. While our immediate goal is the application of ARAC to assist a limited number of ERDA sites, the system is designed with sufficient flexibility to permit expanding the service to a large number of sites. Success in ARAC application should provide nuclear facilities with a means to handle better the urgent questions concerning the potential accidental hazards from atmospheric releases in addition to providing the sites with a capability to assess the effort of their normal operations.