The Swedish Radiation Safety Authority sets constraints for discharges of radioactive substances and checks that the operator stays well below these constraints. We also require the nuclear facilities to make use of best available techniques for gradual reduction of discharges.
The operators are themselves liable to fulfil the requirements in terms of discharge reduction. The Swedish Radiation Safety Authority ensures that the companies take this responsibility by drawing up regulations and exercising regulatory supervision. These regulations require the companies to measure the amount of radioactive substances released into the environment and report this to us.
The companies are required to work towards reducing discharges, even if the discharges are below our constraints. Discharges from the Swedish nuclear power industry have been at a relatively high level compared with many nuclear power plants in other countries. The past few years’ work to reduce discharges has borne fruit, but there is potential for further reductions in discharges in pace with the availability of new technology and new know-how.
Discharges to water
All nuclear facilities need water for their operations. Large quantities of water are managed at the nuclear power plants, with most of the water being reused at the facilities. It is not possible to reuse all the water; however, the nuclear facilities work proactively to as far as possible reduce the quantities of water released. Waste water is treated in several stages and measured as a check before being released. Despite this, however, small quantities of radioactive substances are still present in the water.
Releases to air
All nuclear facilities release small quantities of radioactive substances into the air. Depending on the kind of facility, systems for treatment and measurement are adapted accordingly. Nuclear power plants make use of different systems for time delay so that the level of radioactive inert gases present in the air can drop before the air is released through the stack. The air is also filtered to reduce releases of particulate radioactive substances.
The facilities immediately detect increases in radioactivity in exhaust air. An increase could for example be a sign of damaged fuel rods and indicate that they are leaking radioactive substances.
Measurements in the vicinity of the nuclear facilities
The Swedish Radiation Safety Authority has developed a programme for environment surveillance in the vicinity of the nuclear facilities. The operators are responsible for performing their own measurements in accordance with the programme. For example, they must analyse the level of radioactive substances present in different kinds of biological samples such as mosses, lichens, ferns, grains, fish, bladder wrack algae, mussels and sediment in the sea and nearby lakes.
The Authority’s constraints
The Swedish Radiation Safety Authority limits discharges from Swedish nuclear facilities by imposing a constraint on the maximum dose that an individual living in the vicinity of a facility is allowed to be exposed to owing to discharges from the facility.
No one living near a nuclear facility is allowed to receive a dose exceeding 0.1 mSv per year. This constraint has been set with a good margin of safety to ensure that no one receives a dose that causes injury.
Discharges into the atmosphere and sea are measured at the nuclear facilities. The values measured are then used to calculate the dose contribution for the individual who is likely to receive the highest level of contributions due to the facility’s discharges. These estimates are performed using models developed by the industry but that have been examined by the Authority. Among other things, these models take into account whether the individual inhales air, eats food or drinks water from the nearby surroundings. Calculations are performed for six different age groups; the age group receiving the highest dose is compared with the dose constraint. The results from the dose calculations are reported to us.
Normally, the level of discharges from Swedish nuclear facilities is far below the dose constraint. In normal circumstances, the dose contributions to the (fictitious) individual who received the largest dose due to the discharges from the facility amount to only a few parts per thousand of the dose constraint.