Radiation protection for personnel

Licensees of Swedish nuclear power plants are responsible for ensuring that no one is exposed to radiation levels that cause injury. The licensees must also guarantee that all workers at the facilities are exposed to as little radiation as possible viewed over an extended period of time. This implies that the level of safety must be high enough so that no accidents occur exposing the personnel to radiation. This also means that the personnel must be protected as far as possible from the radiation they are exposed to in their day-to-day tasks.

The Swedish Radiation Safety Authority is the public authority in Sweden with a mandate to exercise regulatory supervision in the area of radiation protection. This is why we work proactively to improve radiation protection work at Swedish nuclear power plants. We check to ensure that these nuclear power plants comply with current regulations governing radiation protection. The main principles are that the benefits from all use of radiation must exceed any potential damage or injury, that the radiation protection must be optimised and no radiation dose limits may be exceeded.

Time, shielding and distance

To keep radiation doses as low as possible, Swedish nuclear power plants apply the three factors of time, shielding and distance. This means that personnel must minimise the work time in the radiation environment, have an appropriate shield between themselves and the radioactive source and work as far as possible from the radiation source. The licensee of a nuclear facility has the full responsibility for effective radiation protection. The role of the Swedish Radiation Safety Authority is to perform inspections, reviews and follow-ups of radiation protection work.

The Authority is also in charge of issuing regulations governing radiation protection that are in turn based on relatively general EU Directives and the Radiation Protection Act. Our regulatory supervision helps us to assess which kind of radiation protection is needed when an activity at a nuclear facility is under development. As a consequence, we can also ensure that Sweden has up-to-date regulations that are in pace with developments in the industry.

One of the aspects of our regulatory supervision is identifying whether there is a lack of knowledge in the field of radiation protection so we can initiate and provide funding for research in order to fill the gaps in knowledge.

The Swedish Radiation Safety Authority performs inspections to check that the licensees of the facilities fulfil the regulations in the field of radiation protection, and through our surveillance inspections, we monitor the operations. This involves our compiling information from and about the work carried out at the facilities so that we gain an understanding of the situation in terms of radiation protection.

Prognoses for low radiation doses

When a nuclear power plant is operating normally, radiation protection work is routine in nature. Radiation protection work becomes more complicated when a reactor has been shut down. This is because many people are then moving about in the facility and a variety of different tasks are performed in radiation environments with higher levels of radiation, in turn placing demands on effective radiation protection.

Planning at nuclear power plants includes preparing the work so that the radiation dose received by personnel is as low as possible. This is achieved by reducing one’s duration in the radiation environment, increasing one’s shielding from the source of radiation and increasing the distance to this source. For instance, this planning work involves ensuring that personnel apply the most effective working methods to reduce the period of time spent in the radiation environment. 

This planning work also includes drawing up a prognosis for the radiation dose prior to all major work. This prognosis is to show the predicted radiation dose for personnel who will take part in the work and each particular step of the work. After the work has been performed, a follow-up is conducted of the actual outcome. The personnel can do this by means of the dose meters they wear.

Planning of radiation protection work

The radiation dose prognosis is to be submitted to the Swedish Radiation Safety Authority no later than four weeks before large-scale work is to be performed. This forces the facilities to plan their radiation protection work and the specific task well in advance. This also means that we gain an understanding of the radiation protection work’s effectiveness and we can pose questions to the facilities prior to the work, or impose requirements for additional measures if this proves to be necessary.

The facilities must report the results to the Authority no later than three months after large-scale work has been performed. The presentation is to contain details about the dose outcome and a description of the experience gained by the facility in connection with this work. The requirement on reporting means that the facilities need to evaluate their own work, thus giving us an opportunity to comment on the work if we consider it to be justified.

Managers at the facilities must also plan their work so that employees have the proper training and information when it comes to radiation protection. Part of the Authority’s regulatory supervision involves performing inspections and checks of the procedures for this planning work.

Dose limits for personnel

Every day, personnel working in a controlled area of a nuclear facility wear a personal dose meter that measures the radiation dose received by the individual. Normally, this result is evaluated once a month.

The dose limit is a maximum of 20 millisievert (mSv) in an individual year.

The objective is to keep the radiation dose as low as possible. The average dose per year for personnel at Swedish nuclear facilities is just over 2 mSv.