1.6 Multi-species Dose Constant Emissions




In previous examples, the dose computations were limited to a single species. The program CON2REM was designed to compute doses for more realistic multi-species emission scenarios. The program reads a unit source HYSPLIT concentration file and a file called ACTIVITY.TXT that defines each radionuclide to be included in the dose calculation. In its current configuration, CON2REM supports two computational species; a generic particulate radionuclide RNUC and a non-depositing noble gas NGAS. A dose is computed for each defined radionuclide using either the RNUC or NGAS computations. The dose is defined as the sum of the product of the emissions, dose conversion factor, dispersion, and deposition coefficients over all radionuclides.

  1. Two pollutants are required to run this simulation. The simplest approach is to put both on the same computational particle. Add the additional variable line to the standard SETUP.CFG namelist file:

    maxdim = 2,    define two species on each particle

  2. In addition to setting the output file name to fdnpp_unit.bin, ensure that the emission section of the CONTROL file is set to a unit hourly rate for the duration of the simulation. Two entry sections are required, one for each species:

    2    two pollutant definitions follow
    RNUC    generic particulate radionuclide
    1.0    emission rate units per hour
    51.0    emission duration in hours
    0 0 0 0 0    emission start time (0 defaults to run start)
    NGAS    generic noble gas
    1.0    emission rate units per hour
    51.0    emission duration in hours
    0 0 0 0 0    emission start time (0 defaults to run start)

  3. The deposition section of the CONTROL file should be configured to correspond to the general characteristics of the RNUC and NGAS pollutants:

    2    two pollutant definitions follow
    1.0 1.0 1.0    defined as a particle
    0.001 0.0 0.0 0.0 0.0    forced dry deposition 0.1 cm/s
    0.0 8.0E-05 8.0E-05    below and within cloud wet removal
    0.0    no radioactive decay
    0.0    no resuspension
    0.0 0.0 0.0    defined as a gas
    0.0 0.0 0.0 0.0 0.0    no dry deposition
    0.0 0.0 0.0    no wet removal
    0.0    no radioactive decay
    0.0    no resuspension

  4. In the first post-processing step, the model predicted dispersion and deposition factors for the two computational species are converted to dose according to the radionuclides and their emission rates defined in the ACTIVITY.TXT file. Decay is applied to both air concentration and deposition from the start time of the simulation. Nobel gases are identified by the zero value for the ground-shine dose conversion factor and these are all associated with the NGAS dispersion coefficients. All other radionuclides listed are linked with the RNUC dispersion-deposition coefficients. In this example the ACTIVITY.TXT file lists the top-ten radionuclides and their maximum emission rate (Bq/h) during the Fukushima accident:

    con2rem    convert concentration to dose
    -ifdnpp_unit.bin    HYSPLIT binary output file
    -ofdnpp_dose.bin    binary output dose file
    -d1    compute dose over averaging time
    -a..\files\activity.txt    emission rates and dose factors

  5. In the second post-processing step, the ground-shine and cloud-shine dose values are added together each time period into a combined total dose output:

    concsum    add ground- and cloud-shine
    -ifdnpp_dose.bin    input binary dose file
    -ofdnpp_total.bin    output binary total dose file
    -l    sum all levels ground+cloud
    -pDOSE    species label in output file

  6. In the third and last post-processing step, the 3-hourly dose values are summed together to obtain a total dose over the specified averaging time period:

    conavgpd    average or sum over time
    -ifdnpp_total.bin    input file of 3-h dose values
    -ofdnpp_sums.bin    binary output file of summed doses
    -a11031409    YYMMDDHH of summation start
    -b11031612    YYMMDDHH of summation end
    -r1    r=1 to sum or r=0 to average

  7. For the first graphics, we produce a time series of the sum of the ground- and cloud-shine dose one would receive at Tokai-mura, about 100 km south of the Fukushima plant. The numbers shown represent the dose each 3-h period and must be accumulated for the total dose:

    echo Tokai 36.4356 140.6025 >latlon.txt    location to file
    con2stn    extract time series at a location
    -ifdnpp_total.bin    binary dose output file
    -oTokai.txt    text output file at location
    -slatlon.txt    latitude & longitude for each location
    timeplot    time series plot
    -iTokai.txt    input file with data to plot
    -p2    plot points and connecting lines
    -y    log axis scaling

  8. In the last graphic, we plot the accumulated dose, computed previously, over the entire model simulation period:

    concplot    concentration plotting program
    -ifdnpp_sums.bin    binary input of dose summation
    -odose_plot    Postscript output file
    -c4    force contour levels
    -v1.0+0.3+0.1+0.03+0.01+0.003+0.001    set forced contours

In this HYSPLIT radiological configuration, a continuous unit source dispersion-deposition calculations with two computational species, one representing a small particle and other a noble gas, were run for a multi-day period of interest. Post-processing programs were used to assign each computational species to multiple radionuclides, each with its own emission rate, decay, and dose factors, to compute dose.