[Exposure risk for workers and prevention measures in ordinary and emergency conditions]. / Rischio espositivo per i lavoratori e misure di prevenzione in condizioni ordinarie e di emergenza.

SUMMARY: The radiological risk assessment and the definition of the radioprotection physical surveillance program applied to a 250 kW (thermal power) research nuclear reactor operated by a large Italian public body. Useful elements for the prevention of personnel exposures, classification criteria for workers, risk reduction methods and optimization of exposures, most common criticalities in plant activities. Analysis of the main operations related to the activities of irradiation and scientific research with an eye to the needs of researchers and one to the indications of prevention. Consolidated intervention methods for ordinary activities and for emergency situations. Detailed examination of the possible unforeseen events or accidents initiators, stopping the assessment at the definition of the source terms related to emergencies inside the plant. Nuclear and conventional causes of accidents and analysis of the radiological consequences. Indications for in-depth-defense and long-term monitoring of the safety of workers, individuals of population and the environment.

[Work at the cyclotron for radioisotope production: exposure risks and prevention measures]. / Il lavoro al ciclotrone per produzione di radioisotopi: rischi espositivi e misure di prevenzione.

SUMMARY: In this article, there will be presented the main aspects of the radiation protection for a site dedicated to the production of radioisotopes by cyclotron for medical use. After analyzing the design parameters of the site for the operation from a point of view of the radiation protection of the operators, the population and the environment (shielding around the accelerator, ventilation system, chimney releases etc.), we will focus our attention to the handling of unsealed sources produced, with particular regard to the operating procedures. The final part will be dedicated to intervention in exceptional operating conditions (entring the bunker due to a machine failure, breaking of a vial during transfer from the hot cell to the transport container and accidental contamination by an operator).

Author Correction: Cryoconite as a temporary sink for anthropogenic species stored in glaciers.

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Cryoconite as a temporary sink for anthropogenic species stored in glaciers.

Cryoconite, the typical sediment found on the surface of glaciers, is mainly known in relation to its role in glacial microbiology and in altering the glacier albedo. But if these aspects are relatively well addressed, the same cannot be said about the geochemical properties of cryoconite and the possible interactions with glacial and peri-glacial environment. Current glacier retreat is responsible for the secondary emission of species deposited in high-altitude regions in the last decades. The role played by cryoconite in relation to such novel geochemical fluxes is largely unknown. Few and scarce observations suggest that it could interact with these processes, accumulating specific substances, but why, how and to what extent remain open questions. Through a multi-disciplinary approach we tried to shed lights. Results reveal that the peculiar composition of cryoconite is responsible for an extreme accumulation capability of this sediment, in particular for some, specific, anthropogenic substances.

A new method based on low background instrumental neutron activation analysis for major, trace and ultra-trace element determination in atmospheric mineral dust from polar ice cores.

Dust found in polar ice core samples present extremely low concentrations, in addition the availability of such samples is usually strictly limited. For these reasons the chemical and physical analysis of polar ice cores is an analytical challenge. In this work a new method based on low background instrumental neutron activation analysis (LB-INAA) for the multi-elemental characterization of the insoluble fraction of dust from polar ice cores is presented. Thanks to an accurate selection of the most proper materials and procedures it was possible to reach unprecedented analytical performances, suitable for ice core analyses. The method was applied to Antarctic ice core samples. Five samples of atmospheric dust (µg size) from ice sections of the Antarctic Talos Dome ice core were prepared and analyzed. A set of 37 elements was quantified, spanning from all the major elements (Na, Mg, Al, Si, K, Ca, Ti, Mn and Fe) to trace ones, including 10 (La, Ce, Nd, Sm, Eu, Tb, Ho, Tm, Yb and Lu) of the 14 natural occurring lanthanides. The detection limits are in the range of 10(-13)-10(-6) g, improving previous results of 1-3 orders of magnitude depending on the element; uncertainties lies between 4% and 60%.

(30)Si mole fraction of a silicon material highly enriched in (28)Si determined by instrumental neutron activation analysis.

The latest determination of the Avogadro constant, carried out by counting the atoms in a pure silicon crystal highly enriched in (28)Si, reached the target 2 × 10(-8) relative uncertainty required for the redefinition of the kilogram based on the Planck constant. The knowledge of the isotopic composition of the enriched silicon material is central; it is measured by isotope dilution mass spectrometry. In this work, an independent estimate of the (30)Si mole fraction was obtained by applying a relative measurement protocol based on Instrumental Neutron Activation Analysis. The amount of (30)Si isotope was determined by counting the 1266.1 keV γ-photons emitted during the radioactive decay of the radioisotope (31)Si produced via the neutron capture reaction (30)Si(n,γ)(31)Si. The x((30)Si) = 1.043(19) × 10(-6) mol mol(-1) is consistent with the value currently adopted by the International Avogadro Coordination.

Gamma residual radioactivity measurements on rats and mice irradiated in the thermal column of a TRIGA Mark II reactor for BNCT.

The current Boron Neutron Capture Therapy (BNCT) experiments performed at the University of Pavia, Italy, are focusing on the in vivo irradiations of small animals (rats and mice) in order to evaluate the effectiveness of BNCT in the treatment of diffused lung tumors. After the irradiation, the animals are manipulated, which requires an evaluation of the residual radioactivity induced by neutron activation and the relative radiological risk assessment to guarantee the radiation protection of the workers. The induced activity in the irradiated animals was measured by high-resolution open geometry gamma spectroscopy and compared with values obtained by Monte Carlo simulation. After an irradiation time of 15 min in a position where the in-air thermal flux is about 1.2 × 10(10) cm(-2) s(-1), the specific activity induced in the body of the animal is mainly due to 24Na, 38Cl, 42K, 56Mn, 27Mg and 49Ca; it is approximately 540 Bq g(-1) in the rat and around 2,050 Bq g(-1) in the mouse. During the irradiation, the animal body (except the lung region) is housed in a 95% enriched 6Li shield; the primary radioisotopes produced inside the shield by the neutron irradiation are 3H by the 6Li capture reaction and 18F by the reaction sequence 6Li(n,α)3H → 16O(t,n)18F. The specific activities of these products are 3.3 kBq g(-1) and 880 Bq g(-1), respectively.