Superconductor based, tomographic, neutron diagnostics for fusion power monitoring.

We propose a scalable system of compact, superconducting neutron monitors, which can be embedded in any existing cryogenic infrastructure of a fusion system. The pixel-based nature of the detectors allows them to be placed at intervals following the circumference of a cooled zone, e.g., a field coil, thus allowing for a tomographic measurement of the neutron flux surrounding the plasma. An early stage prototype of the superconducting bolometer is described, and the key results of a previous feasibility study of this prototype performed with cold neutrons are summarized. The bolometer can be adapted for use with fast neutrons by altering the composition and geometry of the neutron-to-heat conversion layer. This paper describes the initial feasibility considerations for implementation in a superconducting tokamak. The sensor is based on a high-temperature superconductor, making it possible to select the operation temperature in the range 1-90 K. Neutron flux numbers were found using the ITER MCNP reference model, and these were embedded in a TOPAS model to find the expected signal measured by the bolometer at the position of a toroidal field coil. The results at the coil position indicate suitable operation levels in terms of the magnitude of the measured signal, with a measurable signal of several ohm, which is much smaller than the saturation energy of the detector. Radiation hardness is estimated and found to be on the order of at least 40 years for the relevant radiation levels. The upcoming investigation activities of the project are described for both radiation testing and analytical modeling.

Dissolution of Molybdenum in Hydrogen Peroxide: A Thermodynamic, Kinetic and Microscopic Study of a Green Process for 99mTc Production.

99mTc-based radiopharmaceuticals are the most commonly used medical radioactive tracers in nuclear medicine for diagnostic imaging. Due to the expected global shortage of 99Mo, the parent radionuclide from which 99mTc is produced, new production methods should be developed. The SORGENTINA-RF (SRF) project aims at developing a prototypical medium-intensity D-T 14-MeV fusion neutron source specifically designed for production of medical radioisotopes with a focus on 99Mo. The scope of this work was to develop an efficient, cost-effective and green procedure for dissolution of solid molybdenum in hydrogen peroxide solutions compatible for 99mTc production via the SRF neutron source. The dissolution process was extensively studied for two different target geometries: pellets and powder. The first showed better characteristics and properties for the dissolution procedure, and up to 100 g of pellets were successfully dissolved in 250-280 min. The dissolution mechanism on the pellets was investigated by means of scanning electron microscopy and energy-dispersive X-ray spectroscopy. After the procedure, sodium molybdate crystals were characterized via X-ray diffraction, Raman and infrared spectroscopy and the high purity of the compound was established by means of inductively coupled plasma mass spectroscopy. The study confirmed the feasibility of the procedure for production of 99mTc in SRF as it is very cost-effective, with minimal consumption of peroxide and controlled low temperature.

Proton Dynamics in Palladium-Silver: An Inelastic Neutron Scattering Investigation.

Proton dynamics in Pd77Ag23 membranes is investigated by means of various neutron spectroscopic techniques, namely Quasi Elastic Neutron Scattering, Incoherent Inelastic Neutron Scattering, Neutron Transmission, and Deep Inelastic Neutron Scattering. Measurements carried out at the ISIS spallation neutron source using OSIRIS, MARI and VESUVIO spectrometers were performed at pressures of 1, 2, and 4 bar, and temperatures in the 330-673 K range. The energy interval spanned by the different instruments provides information on the proton dynamics in a time scale ranging from about 102 to 10-4 ps. The main finding is that the macroscopic diffusion process is determined by microscopic jump diffusion. In addition, the vibrational density of states of the H atoms in the metal lattice has been determined for a number of H concentrations and temperatures. These measurements follow a series of neutron diffraction experiments performed on the same sample and thus provide a complementary information for a thorough description of structural and dynamical properties of H-loaded Pd-Ag membranes.

14 MeV Neutrons for 99Mo/99mTc Production: Experiments, Simulations and Perspectives.

BACKGROUND: the gamma-emitting radionuclide Technetium-99m (99mTc) is still the workhorse of Single Photon Emission Computed Tomography (SPECT) as it is used worldwide for the diagnosis of a variety of phatological conditions. 99mTc is obtained from 99Mo/99mTc generators as pertechnetate ion, which is the ubiquitous starting material for the preparation of 99mTc radiopharmaceuticals. 99Mo in such generators is currently produced in nuclear fission reactors as a by-product of 235U fission. Here we investigated an alternative route for the production of 99Mo by irradiating a natural metallic molybdenum powder using a 14-MeV accelerator-driven neutron source. METHODS: after irradiation, an efficient isolation and purification of the final 99mTc-pertechnetate was carried out by means of solvent extraction. Monte Carlo simulations allowed reliable predictions of 99Mo production rates for a newly designed 14-MeV neutron source (New Sorgentina Fusion Source). RESULTS: in traceable metrological conditions, a level of radionuclidic purity consistent with accepted pharmaceutical quality standards, was achieved. CONCLUSIONS: we showed that this source, featuring a nominal neutron emission rate of about 1015 s-1, may potentially supply an appreciable fraction of the current 99Mo global demand. This study highlights that a robust and viable solution, alternative to nuclear fission reactors, can be accomplished to secure the long-term supply of 99Mo.

A neutron resonance capture analysis experimental station at the ISIS spallation source.

Neutron resonance capture analysis (NRCA) is a nuclear technique that is used to determine the elemental composition of materials and artifacts (e.g., bronze objects) of archaeological interest. NRCA experiments are mostly performed at the GELINA facility in Belgium, a pulsed neutron source operating with an electron linear accelerator. Very intense fluxes of epithermal neutrons are also provided by spallation neutron sources, such as the ISIS spallation neutron source in the United Kingdom. In the present study, the suitability of the Italian Neutron Experimental Station (INES) beam line for NRCA measurements is assessed using a compact (n, γ) resonance detector made of a Yttrium-Aluminum-Perovskite (YAP) scintillation crystal coupled with a silicon photomultiplier (SiPM) readout. The measurements provided a qualitative recognition of the composition of the standard sample, a lower limit for the sensitivity for NRCA for almost-in-traces elements, and an estimation of the relative isotopic concentration in the sample.