People are also exposed to radiation from human activity, such as medical examinations, airplane travel and industrial processes, which adds an average of 1 mSv per person.
The Radiation Protection Regulations drafted by the Canadian Nuclear Safety Commission (CNSC) limit the dose of radiation from activities licensed by the CNSC that may be received by members of the public to 1 mSv. The estimated annual dose received by representative members of the population in the Gentilly-2 area has always been less than 1% of this prescribed effective dose limit.
The effects of exposure to ionizing radiation on the human body are dependent upon several factors: radiation type (alpha, beta, gamma), dose and duration.
According to a 2003 study by the Direction de santé publique of the Agence de la santé et des services sociaux de la Mauricie et du Centre-du-Québec, cancer rates in the area around Gentilly-2 are no higher than elsewhere in Québec.
In 2004, the International Agency for Research on Cancer conducted a study on cancer risk in nuclear industry workers. Data from Gentilly-2 was combined with data on nearly 600,000 workers in 15 countries. The study showed that in Canada, general mortality and cancer rates are lower and leukemia rates are no higher among nuclear industry workers than among the general population.
Worker health and radiation protection standards
The health of Gentilly-2 employees remains one of Hydro-Québec’s top priorities. As during operations, every worker has a medical follow-up and enjoys access to personalized health care. In addition, every worker wears a dosimeter to measure exposure to ionizing radiation. Furthermore, annual health and safety campaigns keep workers informed of best practices.
CNSC limits for worker exposure are 50 mSv/year and 100 mSv/5 years. For Gentilly-2, Hydro-Québec has set an even more restrictive administrative limit of 20 mSv/year. On average, workers are exposed to only 1 mSv.
Understanding ionizing radiation
To understand ionizing radiation, it is important to have a basic understanding of how nuclear reactions work.
What’s an atom?
The atom is the basic building block of the chemical elements that form matter. An atom is a collection of protons, neutrons and electrons. Together, protons and neutrons form the atomic nucleus. The nucleus is very small, holds a positive charge and contains almost all of the mass of the atom. Light, negative-charged particles called electrons orbit the nucleus. Each atom has an equal number of electrons and protons, making it electrically neutral.
All matter in the universe is made up of countless combinations of the approximately 100 elements that exist in nature. The atoms of each element differ only in the number of particles they contain. Atoms are about 0.1 millionths of a millimetre in size. The nucleus itself is a mere 10,000th of that size.
Radioactivity is a natural phenomenon caused by certain unstable atomic nuclei spontaneously disintegrating into new, lighter and more stable nuclei. It is accompanied by a release of energy in the form of alpha, beta or gamma radiation, known as ionizing radiation.
The radioactive elements (uranium, thorium, potassium) in the Earth’s core are disintegrating, heating it from the inside and causing earthquakes and volcanoes.
What’s ionizing radiation?
Radioactive nuclei lose excess energy through radiation, in the form of helium nuclei (alpha radiation), electrons (beta radiation) or light particles, or photons (X-rays or gamma radiation). This radiation carries enough energy to free electrons from atoms or molecules, thereby ionizing them.
What’s natural radiation?
Radioactivity is a natural phenomenon that we are exposed to daily. It comes from many sources, both natural and artificial, that emit radiation of varying intensity.
Natural sources, particularly stars such as the sun, are responsible for over two-thirds of the ionizing radiation to which we are exposed. Naturally radioactive substances in soil, such as potassium and uranium, and in materials like granite and brick, also produce radiation. Even the human body is radioactive because of the potassium it contains.