Radiation Protection for actinides targets production at ISOLDE

by Alexandre DORSIVAL (CERN, Geneva, Switzerland)

Tuesday 20 Apr 2010, 11:00 → 12:30 Europe/Rome

LNL Meeting Room (INFN LNL)

In the ISOLDE facility at CERN, a 2.8 kW radioactive ion beam facility, radioactive nuclides are produced by spallation and fission reactions by bombardment of fast protons (E = 1.4 GeV) on thick targets. They diffuse out of the hot targets (T = 2000°C), are ionised and extracted by high-voltage into a magnetic mass-separator. Isobaric beams of nuclides are then transported by beam-lines to different experimental stations. This principle of operation is called Isotope Separation On-Line (ISOL). The ISOLDE facility operates with an average of 25 targets units per year, alternatively on two mass-separators, the General purpose Separator (GPS) and the High Resolution Separator (HRS), which allows to provide continuously radioactive ion beams from April to November. A number of ISOL-facilities exist world-wide, but ISOLDE is specific in that it uses production targets made from actinides (U-238 and Th-232), offering via the fission reaction a very wide spectrum of radioactive product nuclides. In contrast to other facilities, radiation protection at ISOLDE begins with the target production from actinides. For this purpose, a class-A work sector [1] for work with unsealed radioactive sources has been installed in Building 179. The work sector is equipped with filtered and monitored ventilation, liquid effluents are retained and only released after control and radiation- and contamination monitors are installed. Access is only permitted under surveillance by personnel of the Radiation Protection Group, who optimises and monitors work in this area. A particle-in-air monitor with alarm for alpha and beta aerosols is the standard method of assessing the risk at the workplace [2]. This measurement has to identify artificial alpha emitters among the natural radon and thoron solid daughters.