Validation of a free release measurement facility on a decommissioning site

The paper summarizes measurements and the Monte Carlo simulations performed to adapt the high purity germanium (HPGe) detectors of the system to the particular tasks of the decommissioning site. The work carried out for the installation and adaptation in CIEMAT of the prototype 'SuperMum', developed in the framework of the European MetroDecom II project for segregation and declassification of materials is described. The activities related to the validation of the prototype for the specific needs of a real Waste Management Unit are presented. Monte Carlo models of the SuperMum have been developed at CIEMAT and CMI using different codes and adapted to the geometries used (big-bag containers with the material volume of up to 0.5 m³). Uncertainty budget reporting tailored for the possible deviations between Monte Carlo assumptions and real waste have been analyzed. Data for several filling levels and activity distributions have been measured with reference sources and a good agreement has been obtained with calculated values.

Activity measurements and determination of nuclear decay data of 166Ho in the MRTDosimetry project

Holmium-166 is a high-energy β^--emitter radionuclide (~ 1.8 MeV) with a short half-life (~26.8h) that offers great potential as an alternative to ⁹⁰Y for the treatment of liver cancer based on radioembolization. The possibility of quantitative Single Photon Emission Computed Tomography (SPECT) imaging of the main γ-ray emission at 80.6 keV, in addition to strong paramagnetic properties suitable for Magnetic Resonance Imaging (MRI), complement this therapeutic potential. The present paper describes the measurements carried out in three European radionuclide metrology laboratories for primary standardization of ¹⁶⁶Ho and new determinations of X- and γ-ray photon-emission intensities in the framework of the European EMPIR project MRTDosimetry. New half-life measurements were also performed.

MEASUREMENT OF SECONDARY NEUTRONS GENERATED DURING PROTON THERAPY

Measurements described in this article were carried out with the aim of evaluating risks of the patient exposure to secondary neutrons during treatment at the Proton Therapy Centre Prague. The neutron spectral fluence was measured by means of the extended Bonner sphere spectrometer (EBS). The article presents secondary neutron spectral fluences obtained by the EBS with passive thermoluminescent detectors, i.e. pairs of ⁶LiF and ⁷LiF chips. Measurements were performed in two positions: the first one behind the Nylon 6 phantom, and the second one close to the range shifter to evaluate their contribution to the generation of neutrons. Both the Nylon 6 phantom and the range shifter were irradiated with a pencil beam of protons 4 mm in diameter and the energy of 200 MeV. The results are supplemented with the values of effective dose derived from neutron spectral fluences.

Microtron MT 25 as a source of neutrons

The objective was to describe Microtron MT25 as a source of neutrons generated by bremsstrahlung induced photonuclear reactions in U and Pb targets. Bremsstrahlung photons were produced by electrons accelerated at energy 21.6 MeV. Spectral fluence of the generated neutrons was calculated with MCNPX code and then experimentally determined at two positions by means of a Bonner spheres spectrometer in which the detector of thermal neutrons was replaced by activation Mn tablets or track detectors CR-39 with a (10)B radiator. The measured neutron spectral fluence and the calculated anisotropy served for the estimation of neutron yield from the targets and for the determination of ambient dose equivalent rate at the place of measurement. Microtron MT25 is intended as one of the sources for testing neutron sensitive devices which will be sent into the space.