Calculations and Measurements of Activation in Concrete Radiological Shielding Produced by a High-Energy Ion Accelerator
L. Masson, L. Bourgois*
* Commissariat à l'énergie atomique, Saclay, UGSP/SPR/SRI, 91191, Gif-sur-Yvette Cedex, France. E-mail: bourgois@aquilon.cea.fr
The Saturne II synchrotron is located on the Commissariat à l'énergie atomique (CEA) Saclay site and has been running since 1979. It should be dismantled in the next few years. Saturne accelerated protons, deuterons, helium ions, and heavy charged particles (up to krypton) with proton energies ranging from 100 to 2900 MeV. Monte Carlo calculations (FLUKA), coupled with activation/evolution computer codes (DARWIN/PEPIN), were used to predict activation in concrete radiological shielding of the accelerator. Activation products were due mainly to (n, gamma) capture reactions, but 22% of the activation came from neutrons with energies greater than 20 MeV [(n,p), (n, spallation), etc., reactions]. Those calculations were compared to gamma ray, helium-3, calcium-45, and iron-55 measurements on samples taken from different concrete shielding: ordinary concrete (2.35 g cm-3), heavy concrete with barium (3.6 g cm-3), and extra-heavy concrete with iron (4.8 g cm-3). The ratio between calculation and measurement varied from one to six, depending on the kind of concrete and the protection depth. In addition, measurements were compared to those obtained by other accelerators (with different energies and particles). It shows that activation depends on integrated charge over production targets, on particle energy, and especially on in-depth activation profile.