Fusion Fission Hybrid Systems (FFHS) could have a potential role in the management of fission reactor wastes, with (in principle) some advantage over the comparable Accelerator Driven systems, devoted to the same objective. The validation of the concept poses major challenges in the area of fusion "source" development. However, the physics of the multiplying and transmutation blanket has also to be carefully understood and validated. Simple experiments can be envisaged for that purpose. Some of these experiments have already been performed in a different research framework (i.e. validation of the ADS concepts) and could constitute a very first database. Moreover, a new series of similar experiments could be planned. (C) 2020 Elsevier Ltd. All rights reserved.

The present paper summarizes the studies related to the development of the conceptual basis of tokamak neutron sources useful for fusion fission hybrid (FFH) reactors and the FFH concept experimental validation. The parameters for a tokamak neutron source are determined by a newly derived scaling laws, based on an extension of the Kadomtsev similarity principle to fusion reactors. The tokamak model obtained is then used as neutron source for a fusion fission hybrid reactor which uses fusion and fission blankets ( which is operated in subcritical mode). This FFH model is simulated using MCNP to determine the tritium produced and the nuclear waste burned. An essential result of this evaluation is the strong ( a factor 6 ) increase of tritium production in the fusion blanket when the nuclear fuel is present in the fission blanket. In parallel, we formulate a proposal of an experimental validation of the FFH concept by using a fusion source injecting neutrons in the core of TRIGA RC-1 reactor configured in subcritical operation mode.

A simplified Fusion-Fission Hybrid System (FFHS) deterministic calculation model has been developed in order to study the coupling between a fusion machine and a subcritical fission system.Monte-Carlo (MC) codes are very flexible and they have to be considered as reference calculation tools for complex systems like FFHS.On the other hand, deterministic codes can provide, in shorter calculation time respect to MC codes, parametric and sensitivity analysis, also by exploiting General Perturbation Theory (GPT) methodologies, which can usefully support the global FFHS theoretical analysis.This work describes the comparison between the results obtained for a simplified FFHS model by using a MC code (MCNP6.1,MC N-Particle) and a deterministic code (ERANOS).In particular, in this preliminary study, integral parameters like k eff , thermal power, neutron fluxes and some key reaction rate profiles, will be compared.If the comparison between the two mentioned codes will give encouraging results further, more refined, studies will be performed in order to consider deterministic codes as a powerful workhorse for the FFHS analysis, including time dependent analysis devoted to transient and reactivity monitoring issues.

Based on the heuristically generalized perturbation theory (HGPT) adapted to subcritical systems [1], a procedure for online operational monitoring of the subcriticality level of a hybrid fusion-fission system in which an "external" neutron source is generated in a magnetically confined tokamak-type plasma is described.This procedure [2], commonly referred to as power control-based subcriticality monitoring (PCSM), consists of compensating of slow and small movements of a specialized control rod in the nuclear fission zone, previously calibrated using a standard procedure, with equally slow and small alterations of the fusion neutron source.PCSM is verified by solving the multigroup transport equation for the direct flux, as well as for the importance function, associated with normalized fission power [3], and a technique is proposed for modifying the fusion neutron source strength based on plasma compression/expansion.Plasma and confining magnetic field adjustments, needed to implement the PCSM, are estimated with due account of the 0-D-plasma power balance.

TRIGA RC-1 Mark II reactor of ENEA’s Casaccia Research Center reached its first criticality in 1960, with a maximum thermal power of 100 kW. In 1967 it was upgraded at the thermal power of 1 MW. Currently the core, fully reflected by graphite, contains 111 TRIGA standard SS cladded fuel elements (235U enrichment 19.90%, uranium weight fraction 8.5% of the UHZr alloy). The reactor is moderated also by demineralized light water, serving as first biological shield and coolant too. TRIGA RC-1 is equipped with various experimental channels and irradiation positions in-core and out of the core, providing a wide range of neutron and gamma fluxes and spectra useful for diverse applications. During 2017 an agreement was signed between ENEA and the Italian Spatial Agency to cooperate in the field of neutron/gamma radiation damage analysis on electronic components to be used in future space-crafts. This agreement provides for use ENEA TRIGA RC-1 (and TAPIRO) research reactors as tools to perform neutron/gamma irradiation on such electronic components. In the meantime, in the frame of other activities focused on the evaluation of the current TRIGA RC-1 fuel burn-up level, a MCNPX model of the reactor has been implemented and validated by means of a comparison between experimental and calculated neutron flux spectra for different core positions, starting from the first core loading in 1967. This paper describes the main steps moved up to now to characterize the facility neutron field and to evaluate some key ASTM(American Society for Testing and Materials)standard damage parameters, such as 1 MeV neutron equivalent flux and hardness parameter, using the MCNPX TRIGA RC-1 model. The description of the neutronic fields present in the available irradiation channels and facilities of TRIGA RC-1 to be used in the future experimental campaigns devoted to radiation damage analysis, always based on the results from the MCNPX model, completes the work described in this paper.

Il reattore TAPIRO e un impianto sperimentale che puo fornire importanti informazioni sulla qualita dei dati nucleari utilizzati per la fisica dei reattori. In particolare, la presenza di una grande quantita di rame nel riflettore, consente di qualificare l'adeguatezza dei dati esistenti per questo materiale in varie librerie di dati di base. In questo lavoro, il codice Serpent e usato per simulare i tassi di reazione che sono stati misurati in una campagna sperimentale condotta in passato. Il confronto quantifica le differenze nei risultati ottenuti utilizzando le librerie JEFF-3.1.1 e ENDF/B-VIII.

The EURATOM FP7 project FREYA was launched in 2011 to support the design and licensing of lead cooled reactors, by choosing as reference the MYRRHA and ALFRED fast spectrum systems. During the five-year project, a number of critical experiments were conducted in the VENUS-F zero-power reactor with the main aim to validate the neutronic codes adopted for the core design. Five critical core configurations were assembled in VENUS-F: the start-up core, the mock-up dedicated to ALFRED and three layouts simulating the MYRRHA reactor conditions. The ERANOS code system, coupled with the JEFF-3.1 nuclear data library, was one of the tools adopted for the design and characterisation of the experiments. In this paper, the results obtained with the ERANOS deterministic code are compared with the experimental measurements of integral and local parameters, such as: the core reactivity and kinetic parameters, the lead void reactivity worth, the axial and radial distributions of fission rates for the nuclides of major interest, the spectral indexes of important actinides (e.g., U-238, Pu-239, Np-237, Am-241) respect to U-235. The comparison between measurements and simulations shows a general good agreement, with some discrepancies for few local parameters that are here discussed. (C) 2018 Elsevier Ltd. All rights reserved.

•Study developed in an IAEA Collaborative Work on ADS Applications and Use of LEU.•Feasibility study of a conceptual design of an ADS fuelled by Th-U solid fuel SA.•Promising results on neutron performances and safety behaviour have been obtained.

Basing on the extension of the HGPT (Heuristical Generalized Perturbation Theory) methodology to subcritical systems [1], a procedure is proposed for the online monitoring of the subcriticality level of ADS reactors with minimal interaction with the plant normal operation. The proposed method, which shall be named with the acronym PCSM (for Power Control based Subcriticality Monitoring), consists in compensating slow, small movements of a control rod with as well slow, small alterations of the external source strength, so that the overall power is maintained constant. The estimation of the subcriticality level requires the knowledge of a bias factor. This implies the standard precalibration of a control rod and the precalculation of the importance function associated with the reactor power control (in this case, the external neutron source strength). To this purpose a calculation procedure will be implemented into the ERANOS code so to extend its present GPT calculation modality. An experimental verification of the proposed method on the TRIGA reactor at the ENEA Casaccia Center is been considered. The reactor would be operated at different subriticality levels corresponding to different positions of a control rod and would be driven by a suitable neutron source.

The reduction of the nuclear waste is one of the most important nuclear issues. The high radiotoxicity of the spent fuel is due to plutonium and some minor actinides (MAs) such as neptunium, americium and curium, above all. One way to reduce their hazard is to destroy by fission MAs in appropriate nuclear reactors. To allow the MAs destruction an important effort have been done on the nuclear data due to the poor knowledge in this field. In the framework of one of the NEA Expert Group on Integral Experiments for Minor Actinide Management an analysis of the feasibility of MAs irradiation campaign in the TAPIRO fast research reactor is carried out. This paper provides preliminary results obtained by calculations modelling the irradiation, in different TAPIRO irradiation channels, of some CEA samples coming from the French experimental campaign OSMOSE, loaded with different contents of MAs, in order to access, through particular peak spectrometry, to their capture cross section. On the basis of neutron transport calculation results, obtained by both deterministic and Monte Carlo methods, an estimate of the irradiated samples counting levels from the AOSTA (Activation of OSMOSE Samples in TAPIRO) experimental campaign is provided.

The GUINEVERE project was launched in 2006 in order to study the feasibility of transmutation in Accelerator Driven subcritical Systems (ADS). This facility, hosted at the Belgian Nuclear Research Center SCK.CEN, couples the fast subcritical lead reactor VENUS-F with an external neutron source provided by the GENEPI-3C accelerator.In order to test on-line subcriticality monitoring techniques, an independent measurement of the reactivity of VENUS-F was achieved using the Modified Source Multiplication Method (MSM). The unknown reactivity of the subcritical configuration of interest was determined by comparing detector count rates driven by an external neutron source in this configuration with those obtained in a slightly subcritical configuration whose reactivity was determined by rod drop experiments. To account for spatial effects, MSM correction factors were calculated for all the detectors using the Monte Carlo neutron transport code MCNP. The corrected reactivity values of all the detectors were found to be consistent. This led to a final estimate of -5.28 +/- 0.13 $ for the reactivity of VENUS-F.The MSM factors calculated with MCNP were found to be insensitive to the assumptions made for modeling the reactor and the detectors. Thus the MSM method appears to be a robust technique for measuring large subcriticality values with good accuracy. (C) 2015 Elsevier Ltd. All rights reserved.

Within the FREYA Project, methods to interpret flux measurements in the VENUS-F core are being studied in order to reconstruct the subcriticality level of the facility. In this work, after the presentation of results obtained with standard techniques such as the Area Method, we introduce an alternative approach to the experimental determination of the reactivity. This method, whose validity has been tested by computational exercises, makes use of general mathematical properties of the point kinetics system of equations and has been recently extended for subcritical system analysis. The evaluation of spatial correction factors is also carried out using deterministic transport evaluations (ERANOS code). The statistical and systematic uncertainty of the results in terms of reactivity is discussed and numerical results are presented

The GUINEVERE experiment (Generation of Uninterrupted Intense NEutrons at the lead VEnus REactor) is an experimental program in support of ADS (Accelerator Driven Systems) and Lead Fast Reactor technologies presently carried out at SCK in Mol (Belgium). GUINEVERE is presently part of the 7th EURATOM FP project FREYA (Fast Reactor Experiments for hYbrid Applications), started on March 2011. The program aims to generate an experimental background for the MYRRHA project, for which by 2023 it is planned the start-up of the facility. The present paper is focused on the analysis, by numerical simulations, of the representativeness, respect to the MYRRHA reference system, of the behaviour of selected spectral indexes in GUINEVERE following a localized or global perturbation in the core. The analysis, carried out by means of GPT (Generalized Perturbation Theory) methodologies implemented into the ERANOS French neutronic code, consisted in the calculation of the different sensitivity coefficients required for determining the correlation coefficients among analogous integral quantities in GUINEVERE and MHYRRA. To obtain such correlation coefficients the dispersion matrix BOLNA, at 15 energy groups, has been used. The results, which include a discussion about the different calculated sensitivity profiles, show a very good correlation for all the spectral indexes taken into account, with special emphasis for the high energy spectral indexes.

The GUINEVERE experiment (Generation of Uninterrupted Intense Neutrons at the lead Venus Reactor) is an experimental program in support of the ADS technology presently carried out at SCK-CEN in Mol (Belgium). In the experiment a modified lay-out of the original thermal VENUS critical facility is coupled to an accelerator, built by the French body CNRS in Grenoble, working in both continuous and pulsed mode and delivering 14 MeV neutrons by bombardment of deuterons on a tritium-target. The modified lay-out of the facility consists of a fast subcritical core made of 30% U-235 enriched metallic Uranium in a lead matrix. Several off-line and on-line reactivity measurement techniques will be investigated during the experimental campaign. This report is focused on the simulation by deterministic (ERANOS French code) and Monte Carlo (MCNPX US code) calculations of three reactivity measurement techniques, Slope ({alpha}-fitting), Area-ratio and Source-jerk, applied to a GUINEVERE subcritical configuration (namely SC1). The inferred reactivity, in dollar units, by the Area-ratio method shows an overall agreement between the two deterministic and Monte Carlo computational approaches, whereas the MCNPX Source-jerk results are affected by large uncertainties and allow only partial conclusions about the comparison. Finally, no particular spatial dependence of the results ismore » observed in the case of the GUINEVERE SC1 subcritical configuration. (authors)« less

Integral parameters can give useful information on the physical properties of a multiplying system. However, various theoretical problems are encountered when trying to introduce them in a consistent way for source-driven systems. Many questions also arise for their experimental estimation. After some general considerations, the paper presents comparisons of numerical results obtained in different approaches and by the application of inverse methods to localized neutron flux signal detections. Results presented refer to the Yalina Booster experimental facility, which constitutes an excellent challenging test for the models and methods, being a neutronically, spatially and spectrally decoupled system. Some considerations on the usefulness of such parameters for kinetic analyses and to qualify the system characteristics are also included in the paper, analyzing both highly and loosely coupled configurations.