Improvement of the activity measurement method for solid dosimeters emitting X-rays.

Today, there is growing interest for neutrons in the intermediate energy range between 100keV and 1MeV, which are responsible for damaging materials in reactor. To improve this deficiency, we use rhodium and niobium which, through the inelastic neutron scattering reaction, leads to the formation of 103mRh and 93mNb low-energy X-emitters. This paper describes the improvements and validation made on this type of complex measurement by X spectrometry: self-attenuation, fluorescence correction, and emission intensity were poorly known previously.

Measurement of absolute K X-ray emission intensities in the decay of 103mRh.

A new experiment was designed to measure the photon emission intensities in the decay of 103mRh. The rhodium samples were activated in the ISIS experimental nuclear reactor at CEA Saclay. The procedure includes an absolute activity measurement by liquid scintillation counting using the Triple-to-Double Coincidence Ratio method, followed by X-ray spectrometry using a high-purity germanium detector to determine the photon emission intensities. The new result (IX = 0.0825 (17)) is derived with a significant reduction of the uncertainty.

SPECTRON, a neutron noise measurement system in frequency domain.

This paper is dedicated to the presentation and validation of SPECTRON, a novel neutron noise measurement system developed at CEA Cadarache. The device is designed for the measurement of the ß(eff) parameter (effective fraction of delayed neutrons) of experimental nuclear reactors using the Cohn-α method. An integrated electronic system is used to record the current from fission chambers. Spectra computed from measurement data are processed by a dedicated software in order to estimate the reactor transfer function and then the effective fraction of delayed neutrons as well as the prompt neutron generation time. After a review of the pile noise measurement method in current mode, the SPECTRON architecture is presented. Then, the validation procedure is described and experimental results are shown, supporting the proper functioning of this new measurement system. It is shown that every technical requirement needed for correct measurement of neutron noise is fulfilled. Measurements performed at MINERVE and EOLE, two experimental nuclear reactors at CEA Cadarache, in real conditions allowed us to validate SPECTRON.