The Potential of Photon Activation and Neutron Activation Techniques for Fast Soil Characterization

Abstract

In the frame of a partnership between CEA and VINCI, various measurement techniques are applied to soil analysis and tested in different laboratories located at CEA Saclay (France). This paper deals with two nuclear measurement techniques assessed in this project. More specifically, this paper presents the feasibility study carried out for two non-destructive active methods: photon activation and neutron activation. First, some atomic nuclides are activated either by photons or neutrons. Secondly, gamma-rays of specific energies are emitted by activated nuclides and gamma-ray spectrometry enables to identify these activated nuclides. Calibration of the full measurement system with reference samples would enable to quantify the mass of activated nuclides. Irradiations performed for photon activation measurements were conducted using a linear electron accelerator (linac) as the latter enables to generate high-energy photons by Bremsstrahlung thanks to its conversion target. Furthermore, irradiations performed for neutron activation measurements were also conducted with a linac. Indeed, photons may be converted to neutrons by photonuclear reactions using a secondary target. In the frame of this project, experiments were carried out at the SAPHIR platform (CEA Saclay) with a Linatron-M9 VARIAN linac. The electron energy was either 6 or 9 MeV. For neutron activation measurements, a secondary target made of heavy water has been used as neutron source and a polyethylene cell enabled to thermalize neutrons and increase the number of reactions of interest. In this paper, we present the different experimental setups and the measurement protocols established for this feasibility study. We show experimental results obtained with raw material samples coming from three construction sites.

Characterization of photoneutron fluxes emitted by electron accelerators in the 4–20 MeV range using Monte Carlo codes: A critical review

“…The latter are due to elastic scattering reactions of neutrons on 16 O contained in the heavy water target. To a lesser extent, (n, γ) reactions on 16 O may also occur and contribute marginally to the dips observed at around 0.4, 1.0, 1.65 and 1.85 MeV [17].…”

“…It should be nevertheless stressed that the second of these two methods enables to optimize both the high-energy photon and the photoneutron beams, and facilitates interpretation of results obtained with the two interrogation techniques. Moreover, a significant interest can also be reported towards linac-based neutron sources for a variety of applications such as: material analysis by neutron activation for different industrial applications [16,17], Boron Neutron Capture Therapy (BNCT) [18], or applications related to nuclear reactors [19], among others. Furthermore, one would notice that such linac-based platforms also enable to deploy a third measurement techniquei.e.…”