BS ISO 20785-4:2019 pdf download -Dosimetry for exposures to cosmic radiation in civilian aircraft Part 4: Validation of codes
5.1 General
Since the radiation protection quantity effective dose, E, cannot be measured, the operational quantity, ambient dose equivalent, H*(10), or its rate, shall be used for the validation of a software code. Then the validation of the code can be assumed in the procedure for the assessment of effective dose, E.
5.2 Measured data
The ambient dose equivalent calculated by the codes shall be validated by a comparison with measured or reference data. The general approach is to perform a comparison with a selection of data from a representative selection of routes with a range of altitude, latitude, longitude and solar activity. The dose measurements shall be performed according to the other parts of the ISO 20785 series, i.e. ISO 20785‑1, ISO 20785‑2 and ISO 20785‑3.
5.3 ICRU reference data ICRU has published reference values of the dose rate [8] . The purpose of the ICRU report is to provide reference data derived from measurements against which the results of routine methods of assessing annual doses using calculations can be compared (benchmarked) for validation purposes. The cut-off rigidity is not a standard input parameter for flight codes as are position and altitude. There are many points with identical vertical cut‑off but different non‑vertical cut‑offs and hence different dose rates. Comparison of the results for locations with a certain vertical cut‑off can be used as a test of the code, but it does not consider the local dose rates which shall be integrated for a flight dose. Therefore, using ICRU 84 cannot be the only test of a code.
5.4 Code validation using measurements or reference data The agreement between dose values calculated using a code and the comparison data should be as good as possible taking into account the uncertainties of the measurements. The dependence of r c is to be determined on the basis of different routes over a large range of the magnetic latitude B m (from the equator to the polar regions), which allows the code validation to be formulated based on either of the following criteria.
1) A code for the determination of the dose at flight altitudes can be accepted if the calculated ambient dose equivalent rates dH*(10)/dt lie, as a function of the cut‑off rigidity r c , for all possible values of r c in a range of ±30 % around the mean values determined from measurements or reference data.
2) The route dose can be determined as a cumulative dose from the take‑off to the landing. For this purpose, dose values shall be calculated on the basis of flight data from routes representative of the range of cut-off rigidities. A code for the determination of the dose at flight altitudes can be accepted if the route doses in terms of ambient dose equivalent calculated for different flights do not differ by more than ±30 % from the measured route doses. The same flight parameters should be used for both the measurements and calculations, especially for flights at high latitude. Specific attention should be made to neutron spectra measurements as they contribute about 50 % to total ambient dose equivalent at normal flight altitudes (ISO 20785-2, ISO 20785-3).
5.5 Considerations for the routine dose assessment In order to check the correctness and reliability of the validated code in routine use, regular comparison flights on representative routes should be used to allow dose values obtained by measurements to be directly compared with the values determined by the code. The measurement procedure shall be in accordance with ISO 20785‑3.
In routine use, additional requirements shall be fulfilled as good practices in terms of code integrity,data security, plausibility check and traceability of measured data.BS ISO 20785-4 pdf download.