Analytical investigation and experimental application of the source modulation technique to measure ρ/βeff\rho/\beta_{eff}

In recent years great interest has been displayed, worldwide, for Accelerator Driven Sub critical reactors (ADS) to incinerate the minor actinides generated by the existing energy producing reactors. In sub critical systems, the effective neutron multiplication factor is lower than 1.0 and the neutrons otherwise required to maintain the chain reaction, can be put to other uses, in particular, the destruction of nuclear wastes such as minor actinides (MA). One of the major advantages of such ADS systems is that it can be operated with very high M.A content without jeopardizing the overall safety due to a small effective delayed neutron fraction, a small Doppler temperature coefficient and possibly also a large void coefficient depending on the chosen coolant. This enhanced safety however prerequisites at all time a sufficient subcriticality margin. Reliable reactivity monitoring techniques are hence required to achieve this goal. The MUSE-4 program is a series of low power experiments carried out at the CEA-Cadarache MASURCA facility to investigate the various methods leading to the measurement of the reactivity level and associated kinetic parameters such as the effective delayed neutron fraction. The aim of this paper is to present the results obtained with a method which directly gives the ratio, for a sub critical assembly, between the reactivity ρ and the effective delayed neutron fraction βeff. By combining these results to those obtained with the kp-method for the prompt neutron multiplication coefficient, we have access to the parameters which govern the prompt and the slow kinetics of a sub critical assembly. These parameters can be obtained without reference to any calibration measurement in critical configuration. It opens the way to the control of larger sub critical demonstrators which are operating with fuels which cannot be used in critical reactor, and, thanks to sub criticality, which are characterized by a deterministic safety

APPLICATION OF THE STOCHASTIC TRANSPORT THEORY TO REACTIVITY MEASUREMENTS IN A SUBCRITICAL ASSEMBLY DRIVEN BY A PULSED SOURCE

ABSTRACT Using the stochastic transport theory formalism developed by Muñoz-Cobo for a radioactive source and for a spallation source, we derive an expression for the Cross Power Spectral Density (CPSD) for a subcritical system driven by an external pulsed neutron source. The derivation of this expression has been done in a rigorous and general way including the energy and spatial dependency. The CPSD shows some peaks at the source frequency together with its harmonics. The final expression containing some approximations (fundamental mode analysis; Dirac delta pulses for the source) is compared with calculations using a Monte Carlo code. In the future, comparisons with measurements in the MUSE project are planned

EFECTO DE TRATAMIENTOS PRE-GERMINATIVOS EN LA CALIDAD DE PLÁNTULAS GUAPINOL (HYMENAEA COURBARIL)

This research has evaluated the effect of five pre-germination treatments on the quality and structure of plant locust (Hymenaea courbaril) due to the high variability in the germination and emergency tillage. Five treatments were evaluated by measuring the rate of Germanization and emergency speed; quality parameters (height and diameter) together with biomass (fresh and dry weight) of seedlings, bringing the Dickson quality index were estimated. Each treatment group contained 50 replicates for 250 plants in the experiment. The data were processed with statistical SPSS V.22.0: variance, standard deviation, variance analysis, obtaining statistical tests of binary correlations, repeated measures analysis and analysis of variance (ANOVA), intra and inter groups, 95% (P-valor 0.05) of confidence. The results show differences between treatments three (hydration) and four (mechanical scarification) regarding treatment one (thermal) and two (chemical) where no statistically significant difference. Treatment five (witness) has less statistical difference with all other evaluated. These same data for determining a positive effect between application of pre germination treatments and increased seedling quality of 93.0%, this translates to a greater chance of survival of the plant to be transplanted in the field. It is tested combination treatments one and three.Esta investigación ha evaluado el efecto que tiene cinco tratamientos pre-germinativos en la calidad y estructura de las planta de guapinol (Hymenaea courbaril) debido a la elevada variabilidad en la germinación y emergencia con la siembra directa. Se evaluaron cinco tratamientos, midiendo el índice de germanización y velocidad de emergencia, parámetros de calidad (altura y diámetro) junto con la de biomasa (peso fresco y seco) de las plántulas, con lo que se estimó el índice de calidad de Dickson. Cada uno de los tratamientos consto de 50 repeticiones para un total de 250 plántulas dentro del experimento. Los datos se procesaron SPSS V.22.0 con los estadísticos: varianza, desviación estándar, análisis de varianza, obteniendo las pruebas estadísticas de correlaciones binarias, análisis de medidas repetidas y análisis de varianza (ANOVA), intra e inter grupos, a un 95% (P-valor 0.05) de confianza. Los resultados muestran diferencia entre los tratamientos tres (hidratación) y cuatro (escarificación mecánica) respecto al tratamiento uno (térmico) y dos (químico) donde no hay diferencia estadísticamente significativa. El tratamiento cinco (testigo) presenta diferencia estadística menor con todos los demás evaluados. Estos mismos datos permiten determinar un efecto positivo entre la aplicación de tratamientos pre-germinativos y el aumento de la calidad de la plántula de un 93.0%, esto se traduce a mayores posibilidades de sobrevivencia de la planta al ser trasplantada en campo. Debe probarse la combinación de los tratamientos uno y tres

Processing and validation of JEFF3.1 library in ACE format at 10 different temperatures

In July 2006 the NEA/Data Bank made available upon request the JEFF-3.1 library in ACE format (NEA-1768 ZZ-MCJEFF3.1NEA). This library contains continuous energy neutron cross section data files for use in the Monte Carlo program MCNP. The nuclides processed are all the evaluations of the General Purpose Library and Thermal Scattering JEFF-3.1 Library, including the important light nuclei, structural materials, fission products, control rod materials and burnable poisons, all major and minor actinides. This library was generated with the NJOY-99.90 nuclear data processing system plus some specific updates required for correct processing. The library has undergone strict Q&A procedures. All inputs used for processing JEFF3.1 with NJOY99.90 and the documented derived version are provided. The validations made, using benchmark experiments for criticality (ICSBEP) and shielding (SINBAD) are documented in the report

PRELIMINARY MEASUREMENTS OF THE PROMPT NEUTRON DECAY CONSTANT IN MASURCA

ABSTRACT Pulse counting techniques have been used to measure the prompt decay constant ~z = (fl-p)/A in the MASURCA reactor of CEA at critical state. The data has been analyzed in time domain using Rossi-~ and Feynman-~ techniques, and in frequency domain using the cross power spectral density. The Rossi-~ technique has been studied using one and two detectors. Due to the strong inherent spontaneous fission source, the one-detector variant gives a very strong whitenoise signal, which is absent in the two-detector method. Because each neutron detected recorded not only a pulse, but also an echo after 120 ns, corrections had to be made to the theory applied. The Feynman-o~ technique is even more sensitive to the echo in the signals, and quite large corrections had to be made. Nevertheless the results obtained are in reasonable agreement with those of the correlation methods. For both measurement techniques, experiments of long duration are needed to get accurate results. The results obtained agree within 10% with calculations. The prompt decay constant has also been measured with a continuous current technique. From the cross power spectral density thus obtained, the c~-value is in agreement with that of the pulse counting techniques

Coupling MCNP-DSP and LAHET Monte Carlo Codes for Designing Subcriticality Monitors for Accelerator-Driven Systems

The design of reactivity monitoring systems for accelerator-driven systems must be investigated to ensure that such systems remain subcritical during operation. The Monte Carlo codes LAHET and MCNP-DSP were combined together to facilitate the design of reactivity monitoring systems. The coupling of LAHET and MCNP-DSP provides a tool that can be used to simulate a variety of subcritical measurements such as the pulsed neutron, Rossi-{alpha}, or noise analysis measurements