I work as a radiochemist at Fennovoima in the unit responsible for radiation safety and radioactive waste management of the Hanhikivi 1 nuclear power plant. Admittedly, the most interesting set of work for which I am responsible for is the radiological environment baseline study. Its purpose is to determine the natural baseline level of radiation and radioactive substances in the vicinity of Hanhikivi 1 plant site. Interestingly, small amounts of radioactive substances are always present in the nature and also in us humans.
We will implement the radiological environment baseline study in three phases. We have carried out a preliminary survey on the marine environment in 2012 and 2014, and 2016 on the terrestrial environment. We also accomplished an environmental analysis before construction work began in the middle of the last decade. We are currently going through a quiet stage, during which the effects of construction work on the marine environment are monitored. We take samples of seawater, sinking matter, benthic fauna, and aquatic flora. Based on the analysis results, the construction work has not affected the radionuclide concentrations as these have remained practically the same.
The final stage of radiological baseline study will begin in 2022, when the terrestrial and marine environment in the vicinity of the Hanhikivi 1 site area will be monitored quite extensively, before the operation of the power plant begins. During a three-year period, samples will be taken from groundwater and surface water, fish, berries, ferns and cereals, and dairy products, just to mention a few. At that time, we will also start whole body countings of nearby residents. The measurements are carried out in co-operation with the Finnish Radiation and Nuclear Safety Authority (STUK) using their expertise and equipment, as is also done at other Finnish nuclear power plants in Loviisa and Olkiluoto.
Whole body countings look at how much people emit gamma radiation. The amount of radiation is affected by people's lifestyles, i.e. what they eat and how much, and if they smoke, for instance. The amount of muscle mass also affects the content of natural radionuclide potassium-40 in humans, as potassium tends to accumulate in muscles.
The average radiation dose of a Finn is about 5.9 millisieverts (mSv) per year. The most significant factor influencing the radiation dose is found in our bedrock, from which radon, a product of uranium decay, is the most significant source of radiation. The annual radiation dose is also affected by, for example, cosmic background radiation, medical X-rays and flying. The radiation dose caused to humans from the use of nuclear power is less than one-tenth of one percent compared to other radiation sources.
Each nuclear operator has their own limits for radioactive releases. The limits for Hanhikivi 1 plant have not yet been set, but the radiation dose caused to the population from the releases will naturally be below the 0.1 millisievert a year limit set in the Nuclear Energy Decree. At the Hanhikivi 1 plant, the releases are mitigated by cleaning and delay systems. In delay systems, as the name implies, the release is delayed so that the short-lived nuclides have decayed, and the level of activity has decreased. Various purification systems help to control liquid releases by cleaning the media from radionuclides as thoroughly as possible, and by returning the media into closed process whenever suitable. Solid waste is packed and placed in the final disposal repository, or released from monitoring if the activity level falls below stipulated limits.
In my opinion radiation safety requirements have been taken well into account in the design of the Hanhikivi 1 plant - the discharge and emission routes are designed appropriately, and the necessary components, such as the radiation detectors of different systems, are in place.