RADIOLOGICAL FALLOUT (RADFO)

LEARNING OBJECTIVES Interpret RADFO forecasts for radiation doses produced by a nuclear detonation. Identify limitations and assumptions. Interpret an example output of the RADFO model, and an example of ATP-45 outputs.

The RADFO model generates forecasts of the accumulated radiation dose from fallout produced by the detonation of a nuclear device. This program replaces the radiological fallout templates in order to better assess early fallout from a radioactive cloud. Output consists of an analysis of accumulated dose of radioactive energy in roentgens for a user-defined location, time, and forecast duration. Appropriate ATP-45 data, such as the radius of the nuclear cloud and the deposition boundary, are also output.

User-supplied input includes either the yield of the weapon or the height of the top of the nuclear cloud, the type of burst (land, sea, or air), the location (latitude and longitude) of surface zero, a specification of the prediction period with respect to time zero, and a specification of the contours to be plotted. The user also specifies a radiosonde data set, which contains an upper wind profile that is to be retrieved from the EDFs. If an applicable upper wind profile is not available, the user may enter one based on either height or pressure levels.

The RADFO model forecasts a pattern of accumulated dose of radioactive energy caused by a specified type of nuclear detonation and dispersed by upper level winds. The forecast is produced in a timely manner for the ships captain or staff, and it is used to determine ship and unit maneuvering to avoid potential nuclear radiation hazards.

RADFO is used to forecast the pattern of accumulated dose of radiation caused by nuclear fallout after the detonation of a nuclear weapon. Care must be taken to select a radiosonde data set that contains an upper wind profile representative of the upper winds at surface zero. Care must also be taken to accurately estimate either the yield of the nuclear weapon or the height of the top of the nuclear cloud.

. Meteorological conditions are considered to be constant for the entire fallout period; no spatial or temporal variations of the upper wind are taken into account.

. This model does not assess radiation from other nuclear phenomena such as the thermal radiation, electromagnetic effects, or initial nuclear radiation emitted in the actual fission or fusion process. This model should only be used as a resource tool to better assess early fallout from the radioactive cloud. Early fallout from a radioactive cloud is normally defined as the fallout that is down within the first 48 hours.

. The RADFO model is meant to be used only for nuclear detonations that occur near the surface (those that throw a significant amount of radiological fallout into the atmosphere). This model should not be used for high-altitude bursts or deep-water bursts.

This model assumes a 100 percent fission yield through the complete spectrum of nuclear weapons, including thermonuclear weapons; this is a worst case estimate.

Output consists of an analysis of dosage of radioactive energy plotted on an appropriate geographic background. The speed and direction of the effective fallout wind are included on the display. ATP-45 output, such as the cloud radius and deposition boundary, is provided on a second screen. Figure 7-8 shows an example output of the RADFO model, and figure 7-9 shows an example of ATP-45 outputs.

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