Preparing for abnormal incidents

Preparations must be made in advance for abnormal incidents in the use of radiation.

Obligations of a responsible party

The responsible party must ensure safety in the use of radiation. Therefore, the responsible party must already during normal operations prepare for abnormal incidents that compromise radiation safety. The responsible party must ensure that

• the possible abnormal incidents are identified and the related risks are assessed
• the risk for exceptional radiation exposure is minimized
• exceptional radiation exposure is detected, its causes are identified and corrective action is taken without delay.

Additionally, the responsible party must

• verify the methods used for the monitoring and periodic inspection and testing of the security arrangements, radiation appliances and other radiation sources, in order to identify reductions of performance that may lead to abnormal incidents
• ensure that the maintenance, inspection and testing of radiation appliances and other radiation sources are conducted appropriately in accordance with the radiation safety regulations, preventing unnecessary exposure to radiation
• verify the procedures for quickly identifying abnormal operations that compromise safety and for taking the corrective measures without delay
• provide the procedures for any anticipated abnormal incidents
• provide the workers with the guidance and equipment necessary for limiting radiation exposure from the possible abnormal incidents
• instruct the reporting practices for abnormal incidents and the procedures for learning from accidents
• ensure that radioactive substances are taken into account in the rescue and safety plan for the place of use of radiation
• verify the periodic assessment and monitoring procedures for the safety measures
• maintain records of the radiation appliances and radiation sources for which it is responsible as well as their location, acquisition and transfer.

Detailed information on the responsible party’s obligation to prepare for abnormal incidents is presented in Guide ST 1.6.

Assessing risks

In order to identify and determine the risks related to the operations, the following, for example, must be assessed in advance:

• probability of a possible abnormal incident
• number of persons potentially exposed to radiation and the magnitude of their radiation exposure
• the possibility and consequences of the failure of structures, systems and processes related to radiation protection or radiation safety
• the changes in operations inside or outside the organization and their possible effect on radiation safety
• the effects of planned changes to radiation shielding or safety measures.

Depending on the type of operations, the assessment of the following may also be necessary:

• factors that may lead to releases of radioactive substances and the measures for preventing or identifying such releases
• the highest possible activity of radioactive substances in the environment caused by a potential failure of the protective structures
• factors that may lead to a minor but continuous release of radioactive substances and the measures for preventing or identifying such releases
• factors that may cause an accidental enabling of a radiation beam and the measures for preventing and detecting such events
• how well redundant, independent safety systems limit the probability and magnitude of a potential radiation exposure.

The following additional assessments may be necessary at specific intervals and after significant changes:

• operating experiences and other information on accidents, mistakes and abnormal incidents that could have led to exposure
• maintenance of and considerable changes to radiation sources, their locations or operation
• significant changes in operations or instructions.

The risk assessment results must be documented and assessed for determining the necessary corrective measures. If, as a result of risk assessment or otherwise, it is deemed necessary to improve protection or take other measures that improve safety, the effects of such measures must also be carefully assessed. If all the measures for improving safety cannot be implemented at the same time, their priority must be determined.

Radiation sources and their location

The radiation appliances and other radiation sources must be designed, constructed and maintained such that accidents and abnormal incidents can be prevented as effectively as possible and that, in the event of abnormal incidents, accidents and radiation exposure can be limited as much as possible by practical means and at reasonable expense.

The selection and location of radiation appliances and other radiation sources as well as the planning of the premises of use shall take into account:

• factors that prevent the damaging and unauthorized acquisition of radiation sources
• factors that affect the radiation exposure of the workers and the members of the public, such as ventilation, radiation shields and distances from living spaces.

The location of radiation sources is especially significant when using or storing large quantities of radioactive substances or if releases of radioactive substances can occur during the operations. In this case, it may be necessary to prepare special, feasible plans for taking cover and provide thorough instructions on protection measures. Detailed information on locating radiation sources is presented in Guide ST 1.10.

Security arrangements

Security arrangements refer to measures for protecting radiation sources against illegal activities, such as harming the source or using it for causing harm. The security arrangements must be taken into account in all use of radiation under a safety licence, and they must be proportioned to the danger posed by the sources and the nature of operations. The security arrangements must be implemented consistently with the radiation safety methods in order to reach the best overall solution that addresses both aspects. Practical security arrangements include the following, for example:

• the radiation sources and appliances undergo inspection, receipt and transfer procedures, which are documented
• protecting the radiation sources with structural barriers
• implementing access control.

Depending on the type of operations, the following may also be necessary:

• preparing a security arrangement plan
• ensuring information security
• implementing an alarm system.

Detailed information on security arrangements is presented in Guide ST 1.11.