A Review on Radiation Damage in Concrete for Nuclear Facilities: From Experiments to Modeling

Concrete is a relatively cheap material and easy to be cast into variously shaped structures. Its good shielding properties against neutrons and gamma-rays, due to its intrinsic water content and relatively high-density, respectively, make it the most widely used material for radiation shielding also. Concrete is so chosen as biological barrier in nuclear reactors and other nuclear facilities where neutron sources are hosted. Theoretical formulas are available in nuclear engineering manuals for the optimum thickness of shielding for radioprotection purposes; however they are restricted to one-dimensional problems; besides the basic empirical constants do not consider radiation damage effects, while its long-term performance is crucial for the safe operation of such facilities. To understand the behaviour of concrete properties, it is necessary to examine concrete strength and stiffness, water behavior, volume change of cement paste, and aggregate under irradiated conditions. Radiation damage process is not well understood yet and there is not a unified approach to the practical and predictive assessment of irradiated concrete, which combines both physics and structural mechanics issues. This paper provides a collection of the most distinguished contributions on this topic in the past 50 years. At present a remarkable renewed interest in the subject is shown

On the hydration of unsaturated barriers for high-level nuclear waste disposal

The paper addresses the topic of the effects of hydration and temperature on the final state of an engineered barrier composed of compacted bentonite. In particular the distributions of water content and dry density are examined. Those issues are explored with reference to a long-duration field test that reproduces at full scale the behaviour of an unsaturated compacted bentonite barrier subjected to hydration and thermal ef-fects. The state of the barrier is discussed at two different stages using data from two separate dismantling op-erations. It is observed that the state of the barrier is not homogenous even after reaching saturation. It is shown that coupled THM analyses are able to predict satisfactorily the state and evolution of the barrier throughout.Postprint (published version

Gamma-ray shielding properties of heavyweight concrete with Electric Arc Furnace slag as aggregate: An experimental and numerical study

This study investigates, both experimentally and numerically, the radiation shielding properties of two types of heavyweight concretes, one containing barite and one made with Electric Arc Furnace (EAF) slag as coarse aggregates. Fresh and hardened concrete properties are preliminary analyzed and compared to a conventional mix containing natural aggregates, namely: fresh and hard bulk density, consistency, compressive and tensile strength, elastic modulus. Three specimens per each mix are subsequently irradiated with both a high-activity (8.97 TBq) and a low-activity (280 kBq) 60Co gamma-ray source to measure their linear attenuation coefficients. Gamma-ray shielding characteristics are also numerically analyzed via a Monte Carlo code assessing radiation transport calculations. Experimental and numerical results indicate that EAF concrete has comparable shielding properties to baritic one, and it allows a certain decrease in thickness of the radiation shield, if compared to an ordinary concrete, however it has superior mechanical properties than the other studied mixtures

Notizia di due manoscritti lulliani a Firenze

Abstract not availabl

Primi passi per lo «scriptorium» lulliano, con una nota filologica

Abstract not availabl

Numerical modelling of ellipsoidal inclusions

Within the framework of numerical algorithms for the threedimensional random packing of granular materials this work presents an innovative formulation for polydispersed ellipsoidal particles, including an overlapping detection algorithm for an optimized simulation of the mesostructure of geomaterials, particularly concrete. Granular composite cement-based materials can be so reconstructed with adequate precision in terms of grain size distribution. Specifically, the algorithm performance towards the assumed inclusion shape (ellipsoidal or spheric) and degree of regularity (round or irregular) is here discussed. Examples on real grading curves prove that this approach is effective. The advantages of the proposed method for computational mechanics purposes are also disclosed when properly interfaced with visualization CAD (Computer Aided Design) tools

A proposito della Petitio Raimundi tra Celestino V e Bonifacio VIII

[eng] In 1294, during his stay in Italy, Ramon Llull addressed a letter (whose date, according to scholars, is November 1294) to Pope Celestine V. The original Catalan version of this letter is preserved by a single manuscript, whilst all the witnesses of the Latin translation known until now - two of which are certainly linked to the authorial environment – are, instead, addressed to Celestine’s successor, Boniface VIII. The short duration of the pontificate of Celestine V justifies this change of addressee. The recent finding, in a fifteenth-century manuscript owned by Giovanni da Capestrano, of a copy of the Latin translation addressed to Celestine V reopens the question. Philological analysis confirms the goodness of the transmitted text, which is contemporary to the most ancient witness of the version addressed to Boniface; this discovery proves both the existence of a Latin translation addressed to Celestine V, and the need to consider afresh Llull’s travels and the chronology of his works between 1294 and 1295.[ita] Nel 1294, nel suo soggiorno in Italia, Raimondo Lullo indirizza a papa Celestino V una lettera (dagli studiosi collocata nel novembre del 1294), della quale rimane la versione originale catalana, testimoniata da un unico manoscritto; i testimoni della traduzione latina che ci rimangono –due dei quali legati sicuramente ad ambiente autoriale– sono tutti invece indirizzati al successore Bonifacio VIII. La breve durata del pontificato di Celestino V giustifica in effetti questo cambio di indirizzo. Il recente rinvenimento in un manoscritto quattrocentesco posseduto da Giovanni da Capestrano di una copia della traduzione latina indirizzata a Celestino V riapre la questione. L’analisi filologica conferma la bontà del testo trasmesso, che si colloca all’altezza del testimone più antico della redazione bonifaciana, provando sia l’esistenza di una traduzione a Celestino V sia la necessità di ripensare i movimenti di Lullo e la cronologia delle opere tra 1294 e 1295