PC CREAM: Technical Support

The DORIS model within PC CREAM is used to estimate activity concentrations in the marine environment for subsequent use in calculations of collective and individual doses. Where relevant, DORIS models the discharges of parent radionuclides and the subsequent decay into the first radiologically significant daughter. This can be an area of confusion when estimating doses as ASSESSOR does not distinguish between the activity concentrations of direct discharges or as the decay product of a parent radionuclide, i.e. decay products will be scaled by the discharge rate of that radionuclide directly, not by the discharge rate of the parent. Example output files from DORIS are given below showing potential differences in activity concentrations.

Activity concentrations due to discharge of uranium-235 directly:

'Local compartment'
	1.00E 00	5.00E 00	5.00E 01	5.00E 02	1.00E 04	1.00E 09
'U-235'	1.46E-02	1.59E-02	1.60E-02	1.60E-02	1.61E-02	1.63E-02

Activity concentrations of uranium-235 as decay product of plutonium-239:

'Local compartment'
	1.00E 00	5.00E 00	5.00E 01	5.00E 02	1.00E 04	1.00E 09
'U-235'	2.86E-13	1.59E-12	1.37E-11	1.46E-11	1.88E-11	3.50E-11

Such decay products can be selected in ASSESSOR (with no indication of whether directly discharges or a decay product) resulting in similar differences (up to ~10 orders of magnitude) in doses calculated.

Due to this treatment of decay products, discharges of radionuclides directly can be considered by running DORIS for the parent alone and using this DORIS file within ASSESSOR to calculate the dose for that radionuclide and any daughters by entering the same discharge rate for the parent and decay products. This will avoid the possibility of modelling a discharge as the contribution from the radionuclide as a decay product rather than a direct discharge. As an example, listed are radionuclides considered to be discharged directly in the default Sellafield files provided with PC CREAM and relevant decay products:

Direct discharge: H-3, C-14, S-35, Mn-54, Fe-55, Co-60, Ni-63, Zn-65, Sr-89, Sr-90, Zr-95, Nb-95, Tc-99, Ru-103, Ru-106, Ag-110m, Sb-125, I-129, Cs-134, Cs-137, Ce-144, Pm-147, Eu-152, Eu-154, Eu-155, U-234, U-238, Np-237, Pu-238, Pu-239, Pu-241, Am-241, Cm-242, Cm-243

Daughter product only: Te-125m, Th-230, Th-234, U-233, U-235

 

Update of globdata.dat

An error has recently been discovered in the file globdata.dat, which should be in folder C:\cream\input\atmos\dllfiles\. The library file is used to calculate global collective doses from atmospheric releases. The error affects H-3 and C-14. The H-3 global collective dose (manSv) per unit release (Bq/y)in the 50th year should be 3.27E-16 and the C-14 global collective dose (manSv) per unit release (Bq/y)in the 10000th year should be 8.42E-11. However, all the data for C-14 have been revised using new dose coefficients from ICRP 72. The new version of globdata.dat can be downloaded from this site.

An updated file has been created, and can be downloaded by right clicking the following link and choosing "Save Target As...". When prompted, save to folder \cream\input\atmos\dllfiles on the hard drive of your PC.

• globdata.dat

Update of depgam.inp (new)

The file depgam.inp, which should be in folder C:\cream\atmos\input\dllfiles, was not generated using the latest version of GRANIS. This library file is used for the calculation of effective dose from deposited gamma emitted (Sv per Bq m ^-2 s for one year). The version of the file distributed with PC CREAM 98 produced skin dose instead of effective dose. This error has implications only for calculations of external gamma from deposited radionuclides (individual and collective dose) and total dose, but it does not affect the dose calculated for all other pathways.

An updated file has been created, and can be downloaded by right clicking the following link and choosing "Save Tartget As...". When prompted, save to folder \cream\input\atmos\dllfiles\ on the hard drive of your PC.

• depgam.inp

How to install PC CREAM on Windows NT (July 1999)

To run PC CREAM on Windows NT, you need to create a copy of the winnt\system folder as windows\system, before you install the program. This is to mirror the Windows 95 directory structure as some file paths in the code refer to this directory.

Regional settings for PC CREAM (July 1999)

Some users have had difficulties in calculating doses due to discharges into rivers. They have found that all dose coefficients for ingestion, as shown in the log file, are zero and consequently all doses due to ingestion pathways are zero. This is not due to an error in PC CREAM but is related to the regional settings of the PC where PC CREAM is installed. To run PC CREAM on your PC you have to make sure that the decimal symbol is set to . and the digit grouping symbol is set to ,. You can check these settings using the Regional Settings controls (Windows 95) or the International controls (Windows 3.1) of your Control Panel.

Display settings for PC CREAM (July 1999)

If you have tried to display your output files using PC CREAM and all you get is a blank screen, it means that your Windows display settings are not the recommended ones for PC CREAM. If you have Windows 95, double click the Display icon in your Control Panel and select the Settings tab. Change the Font Size field to Small Fonts and the Desktop Area to 800 ?? 600 pixels. If you have Windows 3.1, double click the Windows Setup icon in your Control Panel and from the Options menu select Change System Settings. Change the setting to one for a 800 ?? 600 pixels display screen with small fonts.

Can PC CREAM be used to assess short-term atmospheric releases? (December 1999)

No. PC CREAM was designed for use with annually averaged releases and as such appropriate simplifications are built into the models.

What external dose model is used for marine and river assessments? (December 1999)

The model is based on empirical measurements. The equation is taken from Hunt, G J. Simple models for prediction of external radiation from aquatic pathways. Rad. Prot. Dosim., 8, No. 4, 215-24 (1984).

Incorrect river concentration factor for phosphorus (August 2000)

The concentration factor (CF) of phosphorus for freshwater fish in the river model of ASSESSOR is incorrect. The value given in CREAM is 5E-4, however it should be 5E 4. The file FishCF.dat should be altered ( C:\cream\input\river\dllfiles\) to correct the error permanently. Alternatively, a user-defined value can be entered on running the program.

Can I obtain activity concentrations as an output from PC CREAM? (August 2000)

Yes, most of the modules in PC CREAM produce activity concentrations in environmental media in addition to doses. The files either end with .con or .cnc, depending on the module being used.

Where are the cloud beta dose rates in PC CREAM obtained from? (August 2000)

They are taken from Kocher, D C and Eckerman, K F. Electron dose-rate conversion factors for external exposure of the skin. Health Physics, 40, 467-75 (1981).

FARMLAND

Deposition rate in FARMLAND (August 2000)

If the deposition rate is changed when running the fruit model this has little or no effect on the activity concentrations in fruit. One would expect the fruit concentration to be proportional to the deposition rate but this is not the case because the code overwrites the user defined deposition rate with the default. To work around this problem the user must use the default deposition rate and scale the corresponding activity concentrations in fruit by the actual deposition rate.

FARMLAND errors (December 1999)

Two minor errors in the FARMLAND module of PC CREAM have become apparent.

The first results from the fact that an abbreviated form of the radionuclide name is used in the output file names. For example, if FARMLAND is run for I-125 and I-135, the I-125 files will be overwritten by the files for I-135. The solution is to carry out separate runs for the two radionuclides and rename the files for I-125 before the I-135 run is carried out. This is not only a problem for iodine, but applies equally to other radionuclides that have isotopes with a common atomic mass digit or character, for example, Te-127m, Te-129m, and Te-131m.

The second error arises when FARMLAND is run for Ni-63 using the cow or sheep models. The problem is that the biological half-life of nickel in meat and liver is greater than the upper bound that has been set for these parameters. As a consequence, whenever these parameters are written to or read from file an error is generated. However, it is possible to carry out a FARMLAND cow or sheep run for nickel without saving the file and generate correct results before then saving the input data at which point the error will occur.

 

FARMLAND database errors (September 2005)

Incorrect parameter values have been identified in the FARMLAND database. These values affect rate constant calculations for phosphorus for the sheep and cow models only. The values stored in the database were a factor of 10 too low.

An updated file has been created, and can be downloaded by right clicking the following link and choosing "Save Target As...". When prompted, save to folder \farmland\farmdb\ on the hard drive of your PC, replacing the previous version of the database.

• FARMLAND.MDB

PLUME

Problems with high stacks (August 2000)

The PLUME code can be used to model releases from stacks with an effective release height of up to 100 m. The result can then be used in ASSESSOR for a dose calculation. A problem has been identified, especially when modelling relatively high stacks(>75 m) using site-specific meteorological data. These conditions can lead to a zero value being predicted by PLUME for certain sectors at the minimum distance (300 m). The problem occurs when the resultant file is used in ASSESSOR as it tries to interpolate between the minimum and the next value. This creates a divide by zero error. To work around the problem, the PLUME file should be edited and the zero replaced by 1.0E-40, the minimum value accepted by PC CREAM. Although this is an overestimate the contribution to dose will be extremely small.

PLUME error

An error has been found in PLUME concerning the selection of radioactive daughters. Any PLUME runs in which a radionuclide is first included indirectly, by selecting its parent, and then directly, by selecting it from the radionuclide list, will predict the same air concentrations for both instances of the radionuclide. Reversing the order of selection does not cause the problem. If a PLUME run has been carried out that might include this error it is advised to quit PLUME before changing the list of selected nuclides and rerunning the program.

DORIS

How to add a radionuclide to the list provided for the calculation of doses from discharges into the marine environment (July 1999)

If you need to calculate doses from liquid discharges to the marine environment for one or more radionuclides which are not included in PC CREAM, you can add them to the current list provided in DORIS and ASSESSOR. The procedure to amend the list is quite long and requires editing four of the input files provided with PC CREAM. To edit the files you need to have MS Access and a text editor like MS Notepad installed on your PC. To help you we have prepared a step-by-step guide on how to add one radionuclide to the list (the values in brackets, used as an example, are for Hg-203).

1. Using MS Access, open the database doris.mdb, in the folder C:\doris\library. If you use MS Access 7.0 or 97 do not convert to the new format. When a warning message is displayed, press the OK button.
2. Open the table Nuclides.
3. Add data for the following parameters:
   • radionuclide name (Hg-203).
   • radionuclide code (the format of the code is XXYYYC, where XX is the atomic number, YYY is the mass number and C is a character which could be either blank or m for metastable radionuclides; for Hg-203 the code is 80203).
   • half life (0.128 y).
   • coastal K _d (1.0E 04 m ³ t ^-1).
   • deep K _d (5.0E 03 m ³ t ^-1).
   • number of nuclides in decay chain (the only number you can enter here is 1).
4. Close the database.
5. Open the database general3.mdb, in the folder C:\cream\app. If you use MS Access 7.0 or 97 do not convert to the new format. When a warning message is displayed press the OK button.
6. Open the table MarineNuclides.
7. Add data for the following parameters:
   • rRadionuclide name (Hg-203).
   • radionuclide code (80203).
   • f ₁ (1.0, if chemical form is, for instance, 'organic - methyl mercury').
   • absorption type ('F', if chemical form is, for instance, 'organic').
8. Close the database and exit.
9. Using a text editor (MS Notepad), open the ASCII file marinecf.dat which should be in the folder C:\cream\input\marine\dat.
10. Increase the number of radionuclides at the top of the list according to the number of new radionuclides entered (for example, if you add 1 radionuclide to the current file, change the number from 86 to 87).
11. Add data for the following parameters:
    • radionuclide name ('Hg-203').
    • concentration factor for fish (2.0E 04 l kg ^-1).
    • concentration factor for crustaceans (2.0E 04 l kg ^-1>).
    • concentration factor for molluscs (1.0E 04 l kg ^-1).
    • mean gamma energy per decay (2.38E-01 ;MeV Bq ^-1).
    • mean beta energy per decay (9.88E-02 MeV Bq ^-1).
    • skin dose rate conversion factor (6.85E-09 Sv y ^-1(Bq ;m ^-2) ^-1).
12. Save the file.
13. Open the ASCII file of dose coefficients for ingestion dc_ing.dat, which should be in folder C:\cream\input\general\vbfiles.
14. Increase the number of radionuclides at the top of the list to account for the new radionuclides entered (for example, if you add 1 radionuclide to the current file, change the number 123 to 124).
15. Add data for the following parameters:
    • radionuclide name ('Hg-203').
    • f ₁ (same as value in database general3.mdb).
    • dose coefficients for ingestion for:
      • 1 year old infants (1.1E-08 Sv Bq ^-1).
      • 10 year old children (3.6E-09 Sv Bq ^-1).
      • adults (1.9E-09 Sv Bq ^-1).
16. Save the file.
17. Open the ASCII file of dose coefficents for inhalation dc_inh.dat, which should be in folder M C:\cream\input\general\vbfiles.
18. Increase the number of radionuclides at the top of the list according to the number of new radionuclides entered (for example, if you add 1 radionuclide to the current file, change the number 137 to 138).
19. Add data for the following parameters:
    • radionuclide name ('Hg-203').
    • absorption type (same as value in database general3.mdb).
    • dose coefficients for inhalation for:
      • 1 year old infants (3.7E-09 Sv Bq ^-1).
      • 10 year old children (1.1E-09 Sv Bq ^>-1).
      • adults (5.6E-10 Sv Bq ^-1).
20. Save the file and exit.

If you open DORIS or ASSESSOR you will find that the new radionuclides have been added to the list in the Nuclides form (for ASSESSOR you have to select a file compatible with PC CREAM created using DORIS, which includes the new radionuclides).

Sedimentation rates in DORIS (August 2000)

There is a difference in units between the sedimentation rates used in DORIS and those presented in Table 4.5 of the methodology document EUR 15760 (Simmonds, J R, Lawson, G, and Mayall, A. Methodology for assessing the radiological consequences of routine releases of radionuclides to the environment. Radiation Protection 72, EUR 15760. European Commission, Luxembourg (1995)). The values in EUR 15760 are given in units of t m ^-3 y ^-1, whereas in DORIS they are in t m ^-2 y ^-1. To convert the values in EUR 15760 to those required by DORIS, the value should be multiplied by the depth of the compartment.

GRANIS

Using GRANIS to calculate external doses from a known soil profile (December 1999)

The model for calculating external doses above soil in PC CREAM can be used to calculate an instantaneous external dose above known activity concentrations in a soil. Activity concentrations in soil are usually given in Bq g ^-1, Bq kg ^-1 or Bq m ^-2. These values can either be used with the well-mixed or undisturbed soil models.

1. The first step is to perform a dummy run to obtain a soil activity file to edit, so set up GRANIS using the soil model and soil types of interest, use an output time of one year, save the file and run GRANIS.
2. The input file of soil activity concentrations in GRANIS uses atoms of material in each layer of the soil assuming a surface area of 1 m ². For the well-mixed model the layer is 0.3 m, for the undisturbed model the layers are 0-0.01 m, 0.01-0.05 m, 0.05-0.15 m, 0.15-0.3 m, and 0.3-1.0 m. The measured activity concentrations you have should be allocated to the correct layers in the GRANIS model. If, for example, you have activity concentrations in the top 2 cm then this can be split between the 0-0.01 m layer and the 0.01-0.05 m layer as required. The activity in each soil layer should be derived; this may require using the density of the soil (used in GRANIS) and the volume of the layer.
3. The activity in each layer should now be converted to the number of atoms of the radionuclide per layer. To obtain this the activity in becquerels should be divided by the decay constant (lambda) in units of days ^-1.
4. Using a text editor, for example, MS Notepad, open the ASCII file .cof where the radionuclide name is in the form Cs-137. The file will be located in the folder granis\output\pccoma\ where the run name is the same as used in (1) above. The file contains three initial data lines which give the number of soil layers, output times, etc. Immediately following this is a block of data in a column (ten rows for the undisturbed model and two rows for the well-mixed model). The first half of the rows represents the inventories in each soil layer and the second half represents the integrals in each layer. The columns represent the different time periods (in this case just one year) indicated at the top of the file. A further two values are given at the bottom of the file and should be ignored for this purpose.
5. The inventories in each soil layer should be replaced by the values calculated in (3) above and the integrals should be calculated assuming that the soil is in steady state by multiplying by 365 (GRANIS uses days) to convert from atoms/layer to atoms.years/layer. Save the file using the same filename. Run GRANIS again and open the run saved in (1) above. In the Run Options on the main form, select External Dose Only instead of Soil Migration and External Dose. Click on Change and select the edited COMA file from (4) above. Continue to run GRANIS and the output file produced will give dose rates from the measured soil activity concentrations. The soil layer activity concentrations used can be checked by viewing the log file located in C:\GRANIS\Output\ \.log.

Are the gamma disintegration energies for radionuclides available from PC CREAM? (August 2000)

Yes. A database taken from Oak Ridge is located in C:\granis\input\library\ called ornlspec.mdb. The gamma emissions are binned into twelve energies.