Concentration / Utilities / Convert to Dose

Converts a HYSPLIT binary concentration and deposition file to dose in rem/hr. The HYSPLIT calculation should be done using a unit emission so that the concentration units are m-3 and the deposition units are m-2. This post-processing step reads the file activity.txt which contains the activity (Bq) at time=0 for all the isotope products. Sample activity.txt files can be created by the program for a high-energy nuclear detonation or a thermal fission reaction from a power plant reactor. The file also contains the half-life and cloud- and ground-shine does conversion factors for each radionuclide specified in the file.

For nuclear detonations, the activity.txt file contains columns for either a high-energy or thermal fission reaction assuming a yield of 1 kT. The emission factor can be specified as a multiple of 1 kT. Activation products resulting from the fission are not considered. Two fuel sources (U235 and Pu239) are available for each reaction type. The fission yield data were obtained from T.R. England and B.F. Rider, Los Alamos National Laboratory, LA-UR-94-3106; ENDF-349 (1993). The external dose rate for cloud- and ground-shine is computed from the factors given by Eckerman K.F. and Leggett R.W. (1996) DCFPAK: Dose coefficient data file package for Sandia National Laboratory, Oak Ridge National Laboratory Report ORNL/TM-13347.

During the processing step, the cumulative product of the activity and dose factor is computed for each decay weighted concentration averaging period, independently for noble gases and particles. Command line options exist to turn off the dose calculation but still multiplying the dispersion factors by the activity, resulting in air concentration output. If the dispersion factors input file contains only one pollutant type and level, then an option can be set to output each of the species defined in the activity.txt file. Concentration units may also be converted from Bq to pCi.

For nuclear power plant accidents, the same fission product table can be used by entering the duration of the reactor operation in terms of mega-watt-hours based upon the relation that 3000 MW-hours releases an energy equivalent to 2.58 kT. An alternative approach is to generate an activity.txt file that corresponds with the radionuclide release profile of the reactor accident. The command line option -afdnpp will create a sample activity.txt file that corresponds to the maximum emissions over a 3-hour period during the Fukushima Daiichi Nuclear Power Plant accident for the 10 most critical radionuclides for short-term dose calculations.

Post Processing Program CON2REM command line options (default):

An example of the activity.txt file for a 1 kT detonation:

An example of the activity.txt file for the Fukushima-Daichii Nuclear Power Plant Accident for the top ten radionuclides important for short-term dose calculations. The activity represents the maximum number of Bq released over a 3 hour period.

As an example, a HYSPLIT simulation could be configured with two species, NGAS for the noble gases and RNUC for the radio-nuclide particles. After the emissions stop, the total emissions of both NGAS and RNUC should equal one. Then in the post-processing step, con2rem is called and the concentration and deposition fields are multiplied by the total emission and dose conversion factor for each species and added together to get a ground-shine and cloud-shine dose file, which can then be plotted using any of the standard HYSPLIT display programs. Dose results, by species, are decayed to the valid time of the output graphic. An additional time factor can be added for long-term dose estimates.

One aspect of applying the decay in the the post-processing step is that the decay times are referenced to the start of the simulation rather than the start of the release. This means that the radionuclide release rate is valid at the start of the simulation time. This might be the best configuration for a nuclear power plant accident, where the fission is assumed to have stopped at the start of the release (and simulation). However in other situations, where emissions might be occurring in concert with some other process, then starting the decay at the time when the radionuclides are released might be a more appropriate configuration. If the decay is computed during the model calculation for each species released then use the con2rem options -s1 -t0 to apply just the emission factors and not decay in the post-processing step.

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