Chronic radiation doses - hdbk-1130-98

DOE-HDBK-1130-98

d. Probability of a large acute dose

What is important to understand is that it takes a large acute dose of radiation

before any physical effect is seen. These acute doses have occurred in

Hiroshima/Nagasaki, and in a few radiation accidents, including Chernobyl. The

possibility of a radiological worker receiving a large acute dose of ionizing radiation

on the job is extremely low. Typically, radioactive materials are handled in small

quantities that do not produce a large amount of radiation. Where there is a

potential for larger exposures, many safety features are required.

2. Chronic radiation doses

A chronic radiation dose is typically a small amount of radiation received over a long

period of time. An example of a chronic dose is the dose we receive from natural

background every day of our lives. The body's cell repair mechanisms are better able

to repair a chronic dose than an acute dose.

a. The body has time to repair damage because a smaller percentage of the cells need

repair at any given time.

b. The body also has time to replace dead or non-functioning cells with new, healthy

cells.

3. Biological effects of radiation exposure

Somatic effects refer to the effects radiation has on the individual receiving the dose.

Genetic effects refer to mutations due to radiation damage to the DNA of a cell. When

this change is in the DNA of parental reproductive cells, it is called a heritable effect.

a. Somatic Effects

Somatic effects can best be described in terms of prompt and delayed effects as

discussed below.

1) Prompt Effects

Although rare in the nuclear industry, large doses are typically acute

radiation doses representing serious overexposures. The biological effects

of large acute doses are as follows: