CERN European Organisation for Nuclear Research

Applied Physics Group
Radiation Protection at High Energy Accelerators

CERN Accelerating science

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Operating high-energy accelerators inevitably leads to prompt radiation, to activation of accelerator components, detector and shielding materials and to activation of the environment (including rock and earth), of cooling and of ground water and air. Measures must be taken to protect man and the environment as well as radiation sensitive equipment used in the accelerator construction.
During the construction phase of an accelerator, predictions are required of all parameters likely to cause exposure situations to ensure that radiation levels remain below internationally accepted limits. Monte-Carlo cascade calculations are the basic tool. From the results of radiation transport simulations, predictions can be made of shielding requirements and measures can be taken to mitigate the dangers of exposures to high levels of induced radioactivity for maintenance personnel. The quantities of radioactive air and water produced can be used as the source terms for environmental dispersion calculations in order to assess the exposure of persons living near the facility.
During operation of accelerators and associated facilities (including shutdown periods), the main objective of radiation protection is to maintain checks on the levels of radiation using area, environmental and personal monitors and to ensure that exposures are kept at a minimum.
Finally, accelerators will have to be dismantled and radioactive components disposed of as waste in a manner that is safe for future generations.
This series of lectures will provide an overview of the physical phenomena causing prompt and remanent radiation fields at high-energy particle accelerators, including the propagation of cascades induced by beam particles in matter. The implications for shielding and design and operational constraints are discussed, especially in view of current trends to significantly increase beam intensities in future facilities. Various aspects of operational radiation protection, based on CERN's own and host states regulations, are explained and discussed within the general perspective of industrial safety and hygiene. In particular, the three basic principles of justification, optimisation and limitation of exposure (and thus risk) will be discussed.
The lectures will also provide a résumé of current knowledge of effects induced by ionising radiation in biological matter, in particular in humans. It will be shown how this knowledge is used to assess radiation risks and how regulations, including dose limits, are derived.

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