[en] The future of the centralised low and intermediate level waste disposal facility at El Cabril (Cordoba) rests on its integration into the surrounding landscape. Once the disposal platforms have been filled, a final covering made up of a series of layers of soil, draining materials and low permeability materials will be put into place. Prior to drawing up the definitive project for the construction of the long-term covering layer, ENRESA decided in 2008 to initiate two scale tests to evaluate two previously defined alternatives and simultaneously acquire construction experience and obtain experimental information supporting the decisions taken in the final detailed design. The management, development and description of this R and D project constitute the subject of this article. (Author)

[en] The studies performed as a result of the collection of water in the control containers of the low and intermediate level waste disposal structures at El Cabril facility have catalysed the development of more complex and detailed engineered barrier behaviour models more in keeping with physical reality. These models have explained this phenomenon, caused by water evaporation and condensation mechanisms that have no effect on the integrity of the barriers or any radiological impact. (Author).

[en] As a part of EUROTRANS program, it has carried out an experimental campaign focused in the validation of reactivity monitoring techniques in the Yalina-Booster subcritical assembly. The aim of this paper is to present the analysis of part of the experiments results, in particular those carried out with a pulsed neutron source.

[en] The reaction of Di-2-pyridyl-ketone 2-furoylhydrazone (DPFH) with scandium in an aqueous ethanolic medium (4% v/v of ethanol) has been studied. A spectrofluorometric method based on the formation of a fluorescent complex is proposed for the determination of scandium. With excitation at 387 nm, the scandium(III) chelate has an emission maximum at 492 nm; the reaction is carried out at pH 6.5-7.5. The accuracy and precision of the method are demonstrated by the analysis of synthetic mixtures containing various amounts of scandium. 10 - 140 ng/ml of scandium can be determined with a relative error of ±1.3%

[en] A Very Low Level Radioactive Waste disposal site is being planned in El Cabril, Spain, where a Low and Intermediate Level Radioactive Waste disposal site is already located. As part of the ongoing safety assessment for this new facility, we have modelled the transfer of chemical pollutants from the disposal site to the underlying aquifer. The conceptual model is based on the water transport due to the infiltration of rain through the disposal cell. The source term is given by the dissolution of the initial inventory limited by sorption in cement (the main form of the waste) and secondary phase solubility. Several assumptions have been made: all protective layers are degraded, the system is saturated and the water flux is stationary and unidimensional in the vertical direction. A compartment modelling approach has been followed, and the system has been divided in four compartments: Top clay layer, Waste, Bottom clay layer and Subsoil. The latter acts as a sink representing the discharge to the aquifer. Advective and diffusive fluxes are defined between the compartments taking into account hydrological, geochemical and transport properties of the different materials and compounds. The results of the simulation (up to 106 years) show that there is an initial increase in the contaminant release to the aquifer due to the leaching of the waste by the infiltrating waters until a maximum is obtained. In most of the elements the maximum is given by their respective solubility limit and therefore the release is constant during all the time the concentration in the pore water is controlled by solubility. (author)

[en] The Subcritical Accelerator Driven Systems (ADS) have been proposed as one of the strategies for reducing the inventory and radiotoxicity of the spent nuclear fuel. The reactivity monitoring of ADS has been found to play a key role in the development of this technology. Although the current-to-power technique has been proposed as the main reactivity monitoring technique, it is necessary to periodically calibrate it using additional techniques. In this work, the standard reactivity monitoring techniques using Pulsed Neutron Source experiments have been evaluated in the coupled fast-thermal subcritical assembly YALINA-Booster. In addition, a new method to measure the absolute value of the system reactivity is proposed by using micro-interruptions of the continuous external neutron source (beam-trips). This technique, used for the first time in a subcritical core, provided results compatible with the standard PNS methods and can be used in future power ADS. Even more, to allow instantaneous reactivity checks, we have developed and tested the necessary electronic chains and data acquisition system to determine the system reactivity during a single beam trip, thus allowing the determination of the reactivity within a second. (authors)

[en] This technical report of ENRESA refers to the transmutation of some transuranic elements, mainly plutonium and minor actinides (Np, Am and Cm). The transmutation of minor actinides (MA) could be efficiently made by very energetic neutrons, using fast reactors of Generation IV or accelerator driven systems (ADS). This publication is dedicated to expose the state-of-the-art situation of the ADS, mainly the activities developed by CIEMAT within the R+D projects of the EU. This technical publication of ENRESA on Transmutation is the second volume, of a set of two, on Partitioning and Transmutation. The first volume, entitled Partitioning of transuranic elements and some fission products from spent nuclear fuels, was published in 2006. The present report has ten chapters; the first one is an introduction on the spent fuels management, mainly in Spain. In the second one a summary of the main characteristics of spent fuels is provided; in the third the transmutation concept including their nuclear reactions is described; and in the fourth one a description of the present management options of the spent fuels is given. In the fifth chapter several new advanced closed cycles with transmutation of Pu and MA are given and in the sixth one the main proposed transmutation systems are de scribed. Among these, a great emphasis is given to the ADS including its main parts, as they are: the proton accelerator, the spallation source for neutrons production and the subcritical core. Also a re view of different fuels and proposed cool ants for the ADS is made, as well as proposed reprocessing of the transmuted spent fuel from ADS. In this chapter a description of some R+D projects is given, most of them supported by the European Union, with participation of CIEMAT. Chapters seven and eight show the progress on the measurement of new nuclear data to complete the simulation of the transmutation basic processes and systems, together in chapter nine with new R+D activities on transmutation. Finally, chapter ten lists the bibliographic references. (Author)

[en] As a part of the IP-EUROTRANS experimental program at YALINA-Booster, presented in this conference, a set of measurements concerning the current-to-flux techniques has been performed. In a subcritical assembly coupled to an accelerator operating in continuous mode, the power of the reactor is related to the accelerator beam current and the external neutron source strength. It is generally assumed that by monitoring the ratio between the accelerator beam current and the neutron source intensity as well as the ratio between the neutron source intensity and the core power, any change in the system can be detected. With this methodology, changes in the system caused by reactivity transients can be isolated. However, it has been observed that this is only true for transients in the time scale of seconds. At CIEMAT, an acquisition system capable of monitoring the core power, the accelerator beam current and the neutron source intensity in the millisecond scale has been developed. It has been observed that, in these short time ranges, the proportionality relationship between these three quantities is not always fulfilled. (author)

[en] Reactivity monitoring of subcritical systems has been a major topic of study in the 5. and 6. Framework Programme of the EU (MUSE-4 and EUROTRANS) [1]. This interest has been motivated by the proposal of using Accelerator Driven Systems (ADS) to stabilize or reduce the high level nuclear waste inventory. However, licensing and building any industrial scale ADS will require, among other developments, that of a reactivity monitoring system. Among the existing reactivity determination techniques, those based on the point kinetic model are of the most interest due to its simplicity. Pulsed neutron source experiments (PNS) have been used widely in the past since they provide a simple way to apply the prompt decay constant and the area method technique, both based on the point kinetics model. However, MUSE-4 and YALINA-Booster experiments have shown that these techniques can be severely biased in reactors with large reflectors and heterogeneities, making necessary to apply corrections. In addition, the necessity to know the kinetic parameters, β_eff and Λ, to get the criticality constant k_eff forces the use of simulation codes. Hence, this paper proposes a methodology based on Monte Carlo calculations to provide an accurate value of the reactivity using the area method and prompt decay constant results. Furthermore, this methodology reduces the number of kinetic parameters that has to be calculated to just the delayed neutron fraction, which can be calculated with higher accuracy than the mean neutron generation lifetime. (authors)

No abstract available