CALCULATION OF GAMMA EXPOSURE RATES IN AN OPEN OR COVERED BASEMENT IN FALLOUT FIELDS USING THE GADJET CODE.

Abstract : The gamma adjoint energy transport code (GADJET), a Monte Carlo solution of the adjoint transport equation, is used to calculate the exposure rate at a number of positions in a rectangular basement (20 ft x 10 ft x 7 ft) located in the center of plane fallout fields (1 curie 60Co/sq ft). The basement is assumed open or covered with a 4-inch or 6-inch concrete slab. The simulated fallout fields are on the ground plane and are annuli with radii 0 to 60ft, 60 to 200 ft, 200 to 450 ft, 450 to 600 ft, and 600 ft to infinity. Computed exposure rates compare well with experimental data. Differences between experimental data and calculations appear to be mainly due to the 'non-ideal' geometry of the experiments. The GADJET Code is also used in a few cases to show the effects of varying fallout source energy and air density. Use of the GADJET Code for calculating exposure rates in finite fallout fields is shown to be valuable in planning decontamination operations. (Author)