Practical methods of reducing personnel radiation dose at cyclotron facilities

Abstract

The implementation of recent ICRP recommendations regarding the reduction of personnel radiation doses has necessitated some drastic changes in the philosophy and method of operation for several commercial cyclotron facilities. In previous years it was not uncommon for some operations personnel to receive 20-50 mSv/year due to the high radiation fields and operating schedule of some of these cyclotron facilities. The new limit commonly being adopted is 20 mSv/year and this has resulted in many of these facilities switching to more stringent operating routines e.g., scheduled preventative programs schedules, longer cooldown periods for repairs, more conservative beam current levels, and significant upgrades to cyclotron and targetry components. At the Nordion/TRIUMF facilities in Vancouver, Canada the recent upgrade of cyclotrons resulting in significantly higher operating beam currents has made the personnel radiation dose issue even more prominent. By a prudent choice of improved shielding schemes, carefully planned preventative maintenance, improvements to the cyclotron and the targetry hardware these problems have been managed such that individual personnel radiation doses below 10 mSv/year are achieved without compromising production.