55 research outputs found
Antineutrino emission and gamma background characteristics from a thermal research reactor
The detailed understanding of the antineutrino emission from research
reactors is mandatory for any high sensitivity experiments either for
fundamental or applied neutrino physics, as well as a good control of the gamma
and neutron backgrounds induced by the reactor operation. In this article, the
antineutrino emission associated to a thermal research reactor: the OSIRIS
reactor located in Saclay, France, is computed in a first part. The calculation
is performed with the summation method, which sums all the contributions of the
beta decay branches of the fission products, coupled for the first time with a
complete core model of the OSIRIS reactor core. The MCNP Utility for Reactor
Evolution code was used, allowing to take into account the contributions of all
beta decayers in-core. This calculation is representative of the isotopic
contributions to the antineutrino flux which can be found at research reactors
with a standard 19.75\% enrichment in U. In addition, the required
off-equilibrium corrections to be applied to converted antineutrino energy
spectra of uranium and plutonium isotopes are provided. In a second part, the
gamma energy spectrum emitted at the core level is provided and could be used
as an input in the simulation of any reactor antineutrino detector installed at
such research facilities. Furthermore, a simulation of the core surrounded by
the pool and the concrete shielding of the reactor has been developed in order
to propagate the emitted gamma rays and neutrons from the core. The origin of
these gamma rays and neutrons is discussed and the associated energy spectrum
of the photons transported after the concrete walls is displayed.Comment: 14 pages, 11 figures, Data in Appendix A and B (13 pages
New antineutrino energy spectra predictions from the summation of beta decay branches of the fission products
In this paper, we study the impact of the inclusion of the recently measured
beta decay properties of the Tc, Mo, and
Nb nuclei in an updated calculation of the antineutrino energy spectra
of the four fissible isotopes U, and Pu. These
actinides are the main contributors to the fission processes in Pressurized
Water Reactors. The beta feeding probabilities of the above-mentioned Tc, Mo
and Nb isotopes have been found to play a major role in the component
of the decay heat of Pu, solving a large part of the
discrepancy in the 4 to 3000\,s range. They have been measured using the Total
Absorption Technique (TAS), avoiding the Pandemonium effect. The calculations
are performed using the information available nowadays in the nuclear
databases, summing all the contributions of the beta decay branches of the
fission products. Our results provide a new prediction of the antineutrino
energy spectra of U, Pu and in particular of U for
which no measurement has been published yet. We conclude that new TAS
measurements are mandatory to improve the reliability of the predicted spectra.Comment: 10 pages, 2 figure
Total Absorption Spectroscopy Study of Rb Decay: A Major Contributor to Reactor Antineutrino Spectrum Shape
The antineutrino spectra measured in recent experiments at reactors are
inconsistent with calculations based on the conversion of integral beta spectra
recorded at the ILL reactor. Rb makes the dominant contribution to the
reactor spectrum in the 5-8 MeV range but its decay properties are in question.
We have studied Rb decay with total absorption spectroscopy. Previously
unobserved beta feeding was seen in the 4.5-5.5 region and the GS to GS feeding
was found to be 87.5(25)%. The impact on the reactor antineutrino spectra
calculated with the summation method is shown and discussed.Comment: 6 pages, 3 figure
Indication for the disappearance of reactor electron antineutrinos in the Double Chooz experiment
The Double Chooz Experiment presents an indication of reactor electron
antineutrino disappearance consistent with neutrino oscillations. A ratio of
0.944 0.016 (stat) 0.040 (syst) observed to predicted events was
obtained in 101 days of running at the Chooz Nuclear Power Plant in France,
with two 4.25 GW reactors. The results were obtained from a single 10
m fiducial volume detector located 1050 m from the two reactor cores. The
reactor antineutrino flux prediction used the Bugey4 measurement as an anchor
point. The deficit can be interpreted as an indication of a non-zero value of
the still unmeasured neutrino mixing parameter \sang. Analyzing both the rate
of the prompt positrons and their energy spectrum we find \sang = 0.086
0.041 (stat) 0.030 (syst), or, at 90% CL, 0.015 \sang 0.16.Comment: 7 pages, 4 figures, (new version after PRL referee's comments
Uncertainties in projecting climate-change impacts in marine ecosystems
Projections of the impacts of climate change on marine ecosystems are a key prerequisite for the planning of adaptation strategies, yet they are
inevitably associated with uncertainty. Identifying, quantifying, and communicating this uncertainty is key to both evaluating the risk associated
with a projection and building confidence in its robustness. We review how uncertainties in such projections are handled in marine science. We
employ an approach developed in climate modelling by breaking uncertainty down into (i) structural (model) uncertainty, (ii) initialization and
internal variability uncertainty, (iii) parametric uncertainty, and (iv) scenario uncertainty. For each uncertainty type, we then examine the current
state-of-the-art in assessing and quantifying its relative importance. We consider whether the marine scientific community has addressed
these types of uncertainty sufficiently and highlight the opportunities and challenges associated with doing a better job. We find that even
within a relatively small field such as marine science, there are substantial differences between subdisciplines in the degree of attention given
to each type of uncertainty. We find that initialization uncertainty is rarely treated explicitly and reducing this type of uncertainty may deliver
gains on the seasonal-to-decadal time-scale.Weconclude that all parts of marine science could benefit from a greater exchange of ideas, particularly
concerning such a universal problem such as the treatment of uncertainty. Finally, marine science should strive to reach the point where scenario
uncertainty is the dominant uncertainty in our projections
Uncertainties in projecting climate-change impacts in marine ecosystems
Projections of the impacts of climate change on marine ecosystems are a key prerequisite for the planning of adaptation strategies, yet they are inevitably associated with uncertainty. Identifying, quantifying, and communicating this uncertainty is key to both evaluating the risk associated with a projection and building confidence in its robustness. We review how uncertainties in such projections are handled in marine science. We employ an approach developed in climate modelling by breaking uncertainty down into (i) structural (model) uncertainty, (ii) initialization and internal variability uncertainty, (iii) parametric uncertainty, and (iv) scenario uncertainty. For each uncertainty type, we then examine the current state-of-the-art in assessing and quantifying its relative importance. We consider whether the marine scientific community has addressed these types of uncertainty sufficiently and highlight the opportunities and challenges associated with doing a better job. We find that even within a relatively small field such as marine science, there are substantial differences between subdisciplines in the degree of attention given to each type of uncertainty. We find that initialization uncertainty is rarely treated explicitly and reducing this type of uncertainty may deliver gains on the seasonal-to-decadal time-scale. We conclude that all parts of marine science could benefit from a greater exchange of ideas, particularly concerning such a universal problem such as the treatment of uncertainty. Finally, marine science should strive to reach the point where scenario uncertainty is the dominant uncertainty in our projections
Non-proliferation studies with Double Chooz detectors
International audienceThe near detector of Double Chooz will provide the most accurate measurement of the spectrum and the flux of the electronic anti-neutrinos () emitted by a nuclear power plant. This enables the collaboration to address certain safeguards issues for the International Atomic Energy Agencyʼs (IAEA) benefit
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