Importance of parametric uncertainty in predicting probability distributions for burst wait-times in fissile systems

A method of uncertainty quantification in the calculation of wait-time probability distributions in delayed supercritical systems is presented. The method is based on Monte Carlo uncertainty quantification and makes use of the computationally efficient gamma distribution method for prediction of the wait-time probability distribution. The range of accuracy of the gamma distribution method is examined and parameterised based on the rate and magnitude of the reactivity insertion, the strength of the intrinsic neutron source and the prompt neutron lifetime. The saddlepoint method for inverting the generating function and a Monte Carlo simulation are used as benchmarks against which the accuracy of the gamma distribution method is determined. Finally, uncertainty quantification is applied to models of the Y-12 accident and experiments of Authier et al. (2014) on the Caliban reactor

Numerical comparison of mathematical and computational models for the simulation of stochastic neutron kinetics problems

This paper concerns numerical comparisons between five mathematical models capable of modelling the stochastic behaviour of neutrons in low extraneous (extrinsic or fixed) neutron source applications. These models include analog Monte-Carlo (AMC), forward probability balance equations (FPB), generating function form of the forward probability balance equations (FGF), generating function form of the backward probability balance equations (P´al-Bell), and an Itˆo calculus model using both an explicit and implicit Euler-Maruyama discretization scheme. Results such as the survival probability, extinction probability, neutron population mean and standard deviation, and neutron population cumulative distribution function have all been compared. The least computationally demanding mathematical model has been found to be the use of the P´al-Bell equations which on average take four orders of magnitude less time to compute than the other methods in this study. The accuracy of the AMC and FPB models have been found to be strongly linked to the computational e ciency of the models. The computational e ciency of the models decrease significantly as the maximum allowable neutron population is approached. The Itˆo calculus methods, utilising explicit and implicit Euler-Maruyama discretization schemes, have been found to be unsuitable for modelling very low neutron populations. However, improved results, using the Itˆo calculus methods, have been achieved for systems containing a greater number of neutrons

An evaluation of storage time for dithiothreitol‐treated reagent cells

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138313/1/trf14244.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138313/2/trf14244_am.pd

Soil Property Determination for a Seismic Study

Static and dynamic soil property data were needed for input into the seismic retrofit design for the I-155 Mississippi River crossing located near the center of the New Madrid Seismic Zone. Soils consisted of recent river alluvium underlain by very dense soils of the Mississippi embayment. The field investigation consisted of conventional borings, downhole geophysical tests to measure shear wave velocity, and seismic piezo-cone soundings. SPT energy measurements were made at one boring to confirm hammer energy for liquefaction evaluation. This paper summarizes the data and provides site specific correlation of shear wave velocity vs. N-value from the seismic cone and downhole geophysical tests; measured SPT energy value; and estimates of static and dynamic soil properties

Geotechnical Earthquake Engineering for the Great River Bridge

The proposed Great River Bridge is a 1400-foot long cable-stay structure that will be constructed over the Mississippi River between Desha County, Arkansas and Bolivar County, Mississippi. Including the bridge approach structures and approach embankments, the total structure length is approximately 23,500 feet. Seismic issues have controlled most of the structural design. Design ground motions for three typical subsurface profiles were developed and resulted in near-surface peak accelerations between 0.23 and 0.26g. Level ground liquefaction analyses indicated widespread liquefaction in an abandoned channel of the river and sporadic liquefaction elsewhere. Seismic slope stability and lateral spreading analyses indicated minor displacements at the approach embankments, the Arkansas levee, and the Mississippi riverbank; moderate displacements at the Mississippi levee; and major displacements at a 25-foot high natural terrace and the Arkansas riverbank. Conceptual liquefaction mitigation/soil improvement options were investigated

Estuary environmental flows assessment methodology : final specification report

This report provides a consistent and systematic approach to the determination of environmental water requirements for estuaries in Victoria.Victoria&rsquo;s limited water resources are subject to competing demands. These demands, including town water supplies and irrigation requirements, often deplete the flow entering estuaries and put their environmental values at risk.The Estuary Environmental Flows Assessment Methodology (EEFAM) is a standard methodology which can be applied in a consistent manner across all Victorian estuaries, according to their priority. It is not anticipated that this method would be used for the Gippsland Lakes or Port Phillip or Western Port Bay.<br /

Practical quantum metrology with large precision gains in the low photon number regime

Quantum metrology exploits quantum correlations to make precise measurements with limited particle numbers. By utilizing inter- and intra- mode correlations in an optical interferometer, we find a state that combines entanglement and squeezing to give a 7-fold enhancement in the quantum Fisher information (QFI) - a metric related to the precision - over the shot noise limit, for low photon numbers. Motivated by practicality we then look at the squeezed cat-state, which has recently been made experimentally, and shows further precision gains over the shot noise limit and a 3-fold improvement in the QFI over the optimal Gaussian state. We present a conceptually simple measurement scheme that saturates the QFI, and we demonstrate a robustness to loss for small photon numbers. The squeezed cat-state can therefore give a significant precision enhancement in optical quantum metrology in practical and realistic conditions