ASN Report 2015

1. STATE OF KNOWLEDGE OF THE

HAZARDS AND RISKS ASSOCIATED

WITH IONISING RADIATION

Ionising radiation is defined as being capable of producing

ions – directly or indirectly – when it passes through

matter. It includes X-rays, alpha, beta and gamma rays,

and neutron radiation, all of which being characterized

by different energies and penetration powers.

1.1 Biological and health effects

Whether it consists of charged particles, for example

an electron (beta radiation) or a helium nucleus (alpha

radiation), or of photons (X rays or gamma rays), ionising

radiation interacts with the molecules making up the

cells of living matter and alters them chemically. Of the

resulting damage, themost significant concerns the DNA

of the cells and this damage is not fundamentally different

from that caused by certain toxic chemical substances,

whether exogenous or endogenous (resulting fromcellular

metabolism).

When not repaired by the cells themselves, this damage

can lead to cell death and the appearance of harmful

biological effects if tissues are no longer able to carry

out their functions.

These effects, called “deterministic effects”, have been

known for a long time, as the first effects were observed

with the discovery of X rays by W. Roentgen (in the

early 1900’s). They depend on the nature of the exposed

tissue and are certain to appear as soon as the quantity

of radiation absorbed exceeds a certain dose level. These

effects include, for example, erythema, radiodermatitis,

radionecrosis and cataract formation. The higher the

radiation dose received by the tissue, the more serious

the effects.

Cells can also repair the damage thus caused, although

imperfectly or incorrectly. Of the damage that persists,

that to DNA is of a particular type, because residual

genetic anomalies can be transmitted by successive cellular

divisions to new cells. A single genetic mutation is far

from being sufficient to cause the transformation into a

cancerous cell, but this damage due to ionising radiation

may be a first step towards cancerisation.

The suspicion of a causal link between exposure to

ionising radiation and the appearance of a cancer dates

back to 1902 (observation of skin cancer in a case of

radiodermatitis).

Subsequently, several types of cancers were observed

in occupational situations, including certain types

of leukemia, broncho-pulmonary cancers (owing to

radon inhalation) and jawbone sarcomas. Outside the

professional area, themonitoring for more than 60 years

of a cohort of about 85,000 people irradiated at Hiroshima

and Nagasaki has enabled the regular assessment of

the morbidity

and mortality due to cancer following

exposure to ionising radiation, and the description of the

dose-effects relationships – which often form the basis

1. Number of persons suffering from a given disease for a given time

– usually one year – in a population.

onising radiation

may be of natural origin or caused by human activities, referred to

as nuclear activities. The exposure of the population to naturally occurring ionising

radiation is the result of the presence of radionuclides of terrestrial origin in the

environment, radon emanations from the ground and exposure to cosmic radiation.

Nuclear activities are defined in the Public Health Code as

“activities involving a risk

of exposure of persons to ionising radiation associated with the utilisation of artificial sources of

radiation, whether substances or devices, or natural sources of radiation, whether natural radioactive

substances or materials containing natural radionuclides…”

These nuclear activities include

those carried out in Basic Nuclear Installations (BNI) and during the transport of radioactive

substances, as well as in the medical, veterinary, industrial and research fields.

The various principles with which the nuclear activities must comply, particularly those of

nuclear safety and radiation protection, are set out in chapter 3.

In addition to the effects of ionising radiation, BNIs are similar to all industrial installations

in that they are the source of non-radiological risks and detrimental effects such as the

discharge of chemical substances into the environment, or noise emission.

CHAPTER 01:

NUCLEAR ACTIVITIES: IONISING RADIATION AND HEALTH AND ENVIRONMENTAL RISKS

ASN report on the state of nuclear safety and radiation protection in France in 2015