Archive for February, 2019

Problem with using mixtures in DELNuS++

February 25th, 2019

Some of our users have reported that the results of a decay calculation using DELNuS++ for a mixture does not give the same result as the sum of the results for the single nuclide calculations.
As an example, the activity of Cs137 or Kr85 produced from a mixture of Cf252 and Cf250 is almost a factor two higher that from the sum of the results using the single nuclides Cf252 and then Cf250.
The problem has now been identified and resolved.
The results obtained using DELNuS++ for the mixture are now consistent with the sum of the results for the individual component nuclides. The results also agree with those obtained using the Decay Engine++ (which can also account for fission products).

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Ambient dose rates caused by different types of radiation

February 8th, 2019

Ambient dose equivalent H*(d) is the normal monitoring (area monitoring) quantity for X, gamma and neutron radiation where d is the depth at which the dose applies. International convention in radiation protection is to use the ambient dose equivalent at 10 mm depth i.e. H*(10). The ambient dose gives a conservative estimate of the effective dose a person would receive when staying at the point of the monitoring instrument (NPL).
In Nucleonica applications, the photon (X+gamma), beta, and neutron doses are calculated separately using analytical and semi-analytical formulae. To obtain the (total) ambient dose H*(d), these individual doses must be added. Following Otto, the ambient dose from a radionuclide can be represented as a sum of components caused by different radiation types, i.e.
ADR_Radiations3This is the notation which will be used in various Nucleonica applications for ambient doses and dose rates i.e.
ADR_Radiations4
For control of doses to skin and lens of eye, the directional dose equivalent is used. The directional dose equivalent denoted by H′(d) is intended for use with less penetrating radiation such a beta particles. Its main use is for skin dose at a depth of 0.07 mm. For beta radiation and electrons, for example, this is denoted as i.e. H'(0.07)e.
ADR_Radiations6

More info…
– T. Otto, Personal Dose-Equivalent Conversion Coefficients for 1252 Radionuclides, Radiation Protection Dosimetry (2016), Vol. 168, No .1, pp1-70. Link
NPL: Measurement of dose rate
Operational quantities (Wikipedia)

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