4. METHOD OF SOLUTION
The code must be supplied with an initial radioisotope inventory, leakage and cleanup rates for each level of containment, and dose rate factors for each isotope and organ. The containment inventory model contains up to four shells with leakage, aerosol cleanup, and filtration factors, as well as radioactive decay. Inventory equations both inside and outside containment are solved using a numerical method for quasi-linear equations. The meteorological dispersion is calculated from an anisotropic Gaussian cloud using Briggs' values for dispersion coefficients. Gravitational settling and dry deposition may be included for each of three isotope classes. A virtual point source release is employed. The gravitation model applies settling to both actual and image sources. Dry deposition is accounted for by uniform source depletion. Alternately, meteorological dispersion may be calculated from input attenuation factors. In both approaches, the weather conditions may be changed three times. Doses from retained sources are calculated from uniform spherical volume sources using input removal coefficient, buildup factor, and shielding factor at a singl energy. The standard breathing rates for inhalation doses are built-in. The external beta and gamma cloud doses are calculated from analytical formulas for semi-infinite clouds. For modelled meteorology, the external gamma cloud dose may be calculated from the anisotropic Gaussian cloud. A numerical integration is used. Doses may be calculated separately for two groups if isotopes, such as fuel nd fission products. Dose sources may be saved on auxiliary storage and used for subsequent dose-only calculations.
