Page 107 - 6848

Tissue or organ Radiation risk Tissue or organ Radiation risk
factor w T factor w T

Sex glands 0,20 liver 0,05
Red bone marrow 0,12 esophagus 0,05
Colon (large intestine) 0,12 thyroid 0,05
Lights (Lungs) 0,12 skin 0,01
stomach 0,12 The surface of the bone 0,01
bladder 0,05 The rest of tissue or organ 0,05
breasts 0,05

Dose rate (intensity of radiation or radiation level) - an increase of the dose
under the influence of radiation per unit time.
It has the dimension of the dose (absorbed, exposure, etc.), divided by unit

time.
Radiation levels characterize the degree of contamination of the area and
indicates that the dose can get a person, being in the contaminated area per unit time.

13. 3 Sources of I onizing R adiation. Sources of I onizing R adiation

in the O il and G as I ndustry

On average, a person receives an annual dose of 3950 μSv from all sources of
radiation. By far the largest contribution of approximately 86 percent comes from
natural sources (Figure 13.2). Man-made sources contribute approximately 14 percent
and are dominated by the beneficial use of radiation in medicine. Doses from other
man-made or artificial sources account for less than 1 percent.

 Exposure to natural radiation

The principal sources of natural radiation are as follows:

1) Radon, thoron

Radon is a radioactive gas that occurs naturally in the ground and when it

enters a building it can build up to unacceptable levels (Figure 13.3). For most
people, radon is the major contributor to their total dose. On average, a person
receives 2050 μSv per year from radon in the home and an additional 180 μSv from
radon in the workplace. For the individual, there is very large variability in the dose
received from radon. This source of radiation exposure, among all others, is probably
the easiest to reduce.

On average, a person receives 280 μSv per year from exposure to thoron.
Thoron, like radon, is a naturally occurring radioactive gas. Unlike radon, its
principal source is building materials.

4