Energy deposition and Ambient dose equivalent

Dear experts, I do the work about the radiation dose specification for equipment qualification. Firstly, I need to calculate the dose rate of the place where the equipment locates. A simplified model is produced as shown followed.

An electron beam hit a cooper target, the target around is vacuum, and USRBIN is chosen to calculate the energy deposition and the dose field around (Dose-EQ/AMB74 is chosen). The results are shown in follow. I have two questions.

  1. Does ambient dose equivalent is suitable to be used for the radiation dose specification for equipment qualification?
  2. Since dose equivalent is based on the absorbed dose and absorbed dose is the amount of energy deposited by radiation in a mass, so I think dose equivalent is proportional to the energy deposition. However, from the USRBIN results of energy deposition and Ambient dose equivalent, it seems not provides support for the connection of energy deposition and Ambient dose equivalent since USRBIN results shows that the energy deposition replies on material and no energy deposition exist in vacuum while dose equivalent exists not only in the target but also in the vacuum. I am quite confused about this result.

No, you should calculate absorbed dose (GeV/g —> Gy) instead.

It’s not. Dose equivalent results from particle fluence folding with respective conversion coefficients.

Thank you for your response. Do you mean that the accurate radiation dose shoulde be calculate absorbed dose, whihc could be achived by the USRBIN/DOSE option?


Indeed. As a general rule, ask for an odd number of bins in x/y (namely 101 and not 100), such as to get a central bin where the beam impacts on.

Hello Jia,
As you observed in your firts post, absorbed dose is zero in vacuum. In a meaningful simulation you have to place a model of your equipment in the simulation geometry. For a first guess, a slab of the dominant material in a representative distance to the copper target will give you some insight.

Ambient dose equivalent H*(10) is a quantity for radiation protection purposes. Radiation monitors are calibrated in H*(10). It approximates effective dose E, which cannot be measured. Both E and H*(10) are based on particle fluence, the conversion coefficients take into account the radiation sensitivity of organs to different radiation types. Neither of the two quantities is suitable for qualifying equipment for radiation damage.
By the way, while E cannot be measured directly, it can be scored with USRBIN in FLUKA.

Best regards, Thomas

Hello Thomas,thank you for your kindly explanation and I understand more about the concept. I have another question if you are convenient. For radiation dose specification for equipment qualification of nuclear power plants, since there are hundreds of rooms and lots of equipments loacted in each room, it may be difficult and unconvenient to calculate the exact absorbe dose of each equipment. Generally, the maxmium dose equivalent in the room would be calculated and all the equipment qualification in the room would be based on the maxmium dose equivalent, the detail is shown in the attchment paper. Do you think it is not accurate by this way?
20489489.pdf (584.2 KB)

Helllo Jia, the authors of the paper you attached calculate absorbed dose, probably to air (they did not specify it, but it seems logical to me). Reproducing this, you take account of photon absorption and scattering in air and you will get a first idea of radiation levels to equipment.

The next level of approximation can be attained by the following method: In a photon radiation field,absorbed dose to material A can be converted to absorbed dose to material B by the ratio of the mass absorption coefficients \mu_E. You could score absorbed dose rate in air and the photon spectrum in the relevant location (for example averaged over a room). From the spectrum you can calculate the spectrum-averaged conversion coefficient for absorbed dose in air and the target material.

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