Investigation into activation of accelerators at various synchrotron radiation facilities in Japan

Abstract

To establish systematic guidelines for accelerator decommissioning, a large-scale activation survey was conducted at representative synchrotron radiation facilities in Japan. The neutron flux during accelerator operation was measured with various dosimeters. A Monte Carlo simulation was conducted for some facilities to verify the special neutron distribution and their spectra. Beam loss points, reflected as high-dose-rate areas, were identified by a wholebeamline survey with a survey meter, and the generated radionuclides and their activity were determined with a lanthanum bromide (LaBr 3 ) scintillation spectrometer. In all facilities, the activation level was quite low. Whole-beamline tunnels made of concrete were not activated, and no radionuclides were detected except for natural nuclides. In addition, almost all beamline components were either not or minimally activated. Although the acceleration energy is very high for radiation synchrotron facilities, the generation of radioactive waste would be very low.

Radioactivation Investigation for Concrete in Synchrotron-Type Proton Therapy Facilities

“…In our previous study on cyclotron-type proton therapy facilities [2], the "in situ 24 Na measurement method" was used for measuring the thermal neutron fluence rate in concrete with high detection sensitivity. This method was also applied at the electrostatic accelerator facility and the synchrotron radiation facilities [7,8]. First, to determine the specific activity of 24 Na (half-life: 14.9590 hours [3]) produced by the thermal neutron capture reaction of 23 Na in the concrete, the 1,369 keV γ rays from 24 Na were counted by putting a γ-ray spectrometer on the concrete floor in situ after the operation.…”

Identification of Activation Isotopes in a CS-30 Cyclotron Vault

“…In a recent article, Go Yoshida et al [ 18 ] performed an accelerator decommissioning study by conducting a series of surveys in synchrotron radiation facilities in Japan to evaluate the activation of walls and accelerator beam components. Various dosimeters were used to measure ambient neutron flux at various locations of the facilities.…”