CERN’s Radiation Protection Rules and Regulations are based on European Directives and Basic Safety Standards, as well as on the national radiation protection legislations of the two Host States France and Switzerland. These reference rules and best practices continuously develop, with a tendency towards increasing restrictions whilst activities in radiation areas at CERN strongly intensify in particular during long shut-downs like the LS1. The LS1 has been a particular challenge for radiation protection due to the large amount of tasks to be accomplished, ranging from works in slightly radioactive areas such as the LHC arcs (e.g. SMACC) to major consolidation projects in controlled radiation areas such as the target areas TDC2/TCC2 or ISOLDE. At the same time, radiation protection continued to implement European radiation protection rules and best practices leading to some significant changes coinciding with the beginning of LS1. Examples are the new training scheme for radiation protection, the individual and operational dosimetry system and an enhanced system for the tracing of radioactive material (TREC).
Due to a common effort, CERN succeeded in meeting its objective of keeping individual doses below 3 mSv over 12 months during LS1. Only a very few experts out of around 8500 monitored persons received slightly higher doses, but still well below the legal limit. Furthermore, there was no significant radiation protection incident. This excellent result demonstrates that CERN’s procedures and tools put into place to keep the dose to workers as low as reasonable achievable (ALARA) are effective and adapted to the needs of a High Energy Physics laboratory. Today, the ALARA principle has become an important part of CERN’s culture.
Progress made and experience gained from LS1 will be an important asset for LS2. With respect to LS2, the radiological risk in the injectors and related facilities will be more or less similar to LS1. However, radiation levels in the LHC and its experiments will increase and the radiological classification of some areas will change from Supervised Radiation Area to Controlled Radiation Area. This will have consequences for the future training of radiation workers, job and dose planning and dosimetry. There will also be further developments with regard to applicable radiation protection rules, in particular with respect to the inter-site transport of radioactive material, where international transport rules apply, and with respect to exemption limits for radioactive material that will decrease by about a factor of ten for the radionuclides which are most common at CERN (e.g. 22Na, 60Co). To verify such low values for such large quantities of material within a very short delay will represent a challenge to the Radiation Protection Group.
LS2 will profit from the experience gained in LS1, but adjustments will be necessary and the next years will be used to efficiently prepare radiation protection for LS2.