Radiation safety at Loviisa NPP
During the operation of the power plant, radioactive substances develop in the splitting of uranium nuclei and as the materials are activated in the neutron radiation of the reactor core. Most of the activity is within the fuel cladding. Systems that contain or may contain radioactive substances are located inside the controlled area and are closely monitored. The controlled area is enclosed, and nothing can be brought out without careful measurements.
Loviisa power plant takes all practically and reasonably possible measures in order to avoid radiation exposure to any employees, other people or the environment. Our three basic principles of radiation protection are based on the recommendations of the International Commission on Radiological Protection (ICRP). The ICRP recommendations have also been taken into account in the Radiation Act of Finland.
The radiological environmental impact of the normal operation of Loviisa nuclear power plant is very small. The annual radiation dose caused by the operation of the nuclear power plant to the residents in the vicinity is so small that it can not be measured by any meter. Therefore doses in the environment are estimated theoretically based on release information and meteorological data to a theoretical representative person who lives in the vicinity of the plant.
The radiation dose describes the health hazard caused by radiation. Its unit is sievert (Sv). The dose is often given in thousandths of sieverts, i.e. millisieverts (mSv) or in millionths, i.e. microsieverts (µSv).
Some examples of radiation doses
|Dose rate||What the rate causes|
|0,01 mSv||The radiation dose received by a patient having his/her teeth X-rayed.|
|0,1 mSv||The radiation dose received by a patient having his/her lungs X-rayed.|
|2 mSv||The annual dose of cosmic radiation received by a person working in an aeroplene.|
|3,2 mSv||The average annual radiation dose for Finns caused by indoor radon, X-ray examinations, etc.|
|20 mSv||The highest permitted dose for a radiation worker over a period of a year.|
|1000 mSv||The dose which may cause symptons of a radiation sickness (e.g. tirednss and nausea) if received within 24 hours.|
|6000 mSv||A dose that when received within under 24 hours causes radiation sickness and can be fatal.|
Radiation dose rate
The dose rate indicates the amount of radioactive dose received by a person within a certain period of time. The unit of the dose rate is sieverts per hour (Sv/h).
Some examples of external dose rates
|0,04–0,30 µSv/h||Natural background radiation in Finland.|
|0,2–0,4 µSv/h||The dose rate which, if it's exceeded, causes an alarm in an automatic radiation monitoring station in the Finnish automatic external dose rate monitoring network. Each station in Finland has its own station-specific alarm level, which is determined separately for each station. Alarm levels in Finland are between 0.2 and 0.4 µSv/h. The differences are mainly caused bu the level of natural radioactivity in the soil surrounding each sensor.|
|5 µSv/h||The dose rate in an aeroplane flying at an altitude of 12 kilometres.|
|5 µSv/h||The highest dose rate measured in Finland during Chernobyl accident.|
|10 µSv/h||Some protective measures are needed, e.g. avoiding being outdoors unnecessarily.|
|30 µSv/h||The dose rate measured at a distance of one metre of a patient that has undergone isotope treatment. When the dose rate is less than 30 µSv/h, the patient can be discharged.|
|100 µSv/h||It is necessary to take protective measures, e.g. to shelter indoors.|