Measuring Radiation Dosage — Question 2

Question 2

Radiation weighting changes equivalent dose without changing absorbed energy

One specified tissue receives photon absorbed dose $D_\gamma=2.00\,\mathrm{mGy}$ and alpha absorbed dose $D_\alpha=.100\,\mathrm{mGy}$. For this exercise use radiation weighting factors $w_\gamma=1$ and $w_\alpha=20$.

1. Find total absorbed dose and equivalent dose $H=\sum_Rw_RD_R$.

2. Find the alpha fraction of equivalent dose and compare it with the alpha fraction of absorbed dose.

Question 2 - Solution

Radiation weighting changes equivalent dose without changing absorbed energy

(a) Method and calculation

$$\boxed{D_{\mathrm{total}}=2.00+.100=2.10\,\mathrm{mGy}}.$$$$\boxed{H=1(2.00)+20(.100)=4.00\,\mathrm{mSv}}.$$

(b) Interpretation and further calculation

$$\boxed{H_\alpha/H=2.00/4.00=.500}.$$$$\boxed{D_\alpha/D_{\mathrm{total}}=.100/2.10=.04762}.$$

Physical check

Gray and sievert describe different quantities even though both use joules per kilogram dimensionally. Weighting is a protection convention, not extra deposited physical energy.