9,169 research outputs found
Detection of Anomalous Reactor Activity Using Antineutrino Count Rate Evolution Over the Course of a Reactor Cycle
This paper analyzes the sensitivity of antineutrino count rate measurements
to changes in the fissile content of civil power reactors. Such measurements
may be useful in IAEA reactor safeguards applications. We introduce a
hypothesis testing procedure to identify statistically significant differences
between the antineutrino count rate evolution of a standard 'baseline' fuel
cycle and that of an anomalous cycle, in which plutonium is removed and
replaced with an equivalent fissile worth of uranium. The test would allow an
inspector to detect anomalous reactor activity, or to positively confirm that
the reactor is operating in a manner consistent with its declared fuel
inventory and power level. We show that with a reasonable choice of detector
parameters, the test can detect replacement of 73 kg of plutonium in 90 days
with 95% probability, while controlling the false positive rate at 5%. We show
that some improvement on this level of sensitivity may be expected by various
means, including use of the method in conjunction with existing reactor
safeguards methods. We also identify a necessary and sufficient daily
antineutrino count rate to achieve the quoted sensitivity, and list examples of
detectors in which such rates have been attained.Comment: 9 pages, 7 figures, submitted to J. Appl. Phy
Double-logarithms in Einstein-Hilbert gravity and supergravity
We study the interplay between graviton reggeization and double-logarithmic
in energy contributions to four-graviton scattering in theories with and
without supersymmetry. Predictions to all orders in the gravitational coupling
are given for these double-logarithms. As the number of supersymmetries grows
these terms generate a convergent behaviour for the amplitudes at very high
energies. At two-loop level, we find agreement with previous exact results for
N=8 supergravity and with those of Boucher-Veronneau and Dixon, who studied the
N=4,5,6 supergravities using a conjectured double-copy structure of gravity
Liquid Polymorphism and Density Anomaly in a Lattice Gas Model
We present a simple model for an associating liquid in which polymorphism and
density anomaly are connected. Our model combines a two dimensional lattice gas
with particles interacting through a soft core potential and orientational
degrees of freedom represented through thermal \char`\"{}ice
variables\char`\"{} . The competition between the directional attractive forces
and the soft core potential leads to a phase diagram in which two liquid phases
and a density anomaly are present. The coexistence line between the low density
liquid and the high density liquid has a positive slope contradicting the
surmise that the presence of a density anomaly implies that the high density
liquid is more entropic than the low density liquid
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