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The study examined association between oscillations of body temperature of laboratory Wistar rats maintained under constant illumination with the amplitude of fluctuations of secondary cosmic rays reported by neutron count rate provided by neutron monitors and geomagnetic undulations. In contrast to geomagnetic undulations, neutron count rate variations and body temperature oscillations in rats assessed by spectrum analysis of the corresponding step functions at 1-min intervals demonstrated almost permanent variations with the periods ranging from 100 to 400 min. Under conditions of constant illumination inducing changes in the period of circadian rhythm and predominance of the ultradian rhythms, an association between neutron count rate fluctuations and body temperature oscillations was observed perpetually during the day- and nighttime.

The effect meteorological parameters have on the concentration of thermal neutrons is studied using data from the NEUTRON setup in the period May 2015 to February 2019. Daily and seasonal variations in the neutron count rate are obtained. Such variations are associated with changes in temperature. The effect the depth of the snow cover has on the neutron count rate for four winter periods is estimated. It is shown that meteorological parameters have a considerable impact on the concentration of neutrons near the surface. The total contribution from pressure, temperature, and the depth of the snow cover can be more than 30%.

Pulsed neutron-neutron (PNN) logging is based on emitting neutrons into the near-wellbore zone and computing the neutron count decay due to scattering and capturing. The main application of this logging tool is to determine the current oil saturation and to detect channeling in perforated and non-perforated intervals behind the casing. Correct interpretation of the results obtained from PNN logging enables engineers to predict new perforation intervals in depleted reservoirs. This study examines the application of PNN logging in a well located in one of Iranian oil reservoirs. The interpretation procedure is described step by step. The principle of the PNN logging and the specifications of the tool are discussed and the applications of PNN logging in evaluation of oil saturation, identification of water flooded zones and prediction of potential perforating zones are described. Channeling is also investigated between all layers, good and poor oil zones are characterized based on the calculated oil saturations and new perforation intervals are suggested with the aim to boost oil production from the reservoir. The results of this study show that zones 1 to 5 having low oil saturations, are interpreted as depleted oil zones. Zones 6 to 8 are interpreted as good oil zones having high potential to produce oil. Zone 9 is interpreted as a water zone.

The Fork detector is widely used by the safeguards inspectorate of the European Atomic Energy Community (EURATOM) and the International Atomic Energy Agency (IAEA) to verify spent nuclear fuel. Fork measurements are routinely performed for safeguards prior to dry storage cask loading. Additionally, spent fuel verification will be required at the facilities where encapsulation is performed for acceptance in the final repositories planned in Sweden and Finland. The use of the Fork detector as a quantitative instrument has not been prevalent due to the complexity of correlating the measured neutron and gamma ray signals with fuel inventories and operator declarations. A spent fuel data analysis module based on the ORIGEN burnup code was recently implemented to provide automated real-time analysis of Fork detector data. This module allows quantitative predictions of expected neutron count rates and gamma units as measured by the Fork detectors using safeguards declarations and available reactor operating data. This paper describes field testing of the Fork data analysis module using data acquired from 339 assemblies measured during routine dry cask loading inspection campaigns in Europe. Assemblies include both uranium oxide and mixed-oxide fuel assemblies. More recent measurements of 50 spent fuel assemblies at the Swedish Central Interim Storage Facility for Spent Nuclear Fuel are also analyzed. An evaluation of uncertainties in the Fork measurement data is performed to quantify the ability of the data analysis module to verify operator declarations and to develop quantitative go/no-go criteria for safeguards verification measurements during cask loading or encapsulation operations. The goal of this approach is to provide safeguards inspectors with reliable real-time data analysis tools to rapidly identify discrepancies in operator declarations and to detect potential partial defects in spent fuel assemblies with improved reliability and minimal false positive alarms. The results are summarized, and sources and magnitudes of uncertainties are identified, and the impact of analysis uncertainties on the ability to confirm operator declarations is quantified.

In this paper, the compensated neutron logging is transformed into the Thermal Neutron Cross Section Logging (TNXS) to improve the application effect. Because the compensated neutron logging measures the neutron count, TNXS cannot be directly measured by the compensated neutron logging tool. Moreover, the thermal neutron ratio cannot be directly converted into the TNXS due to the influence of lithology and fluid. The ratio of thermal neutron count is related not only to the formation hydrogen index, but also to the formation density and the formation capture cross section. The density and the capture cross section of formations can be used to reduce the influence of lithology and fluid. Therefore, the thermal neutron counting ratio can be converted into the TNXS by density and the capture cross section of formations. The accuracy of the porosity calculated by the TNXS is studied based on the Monte Carlo method. The results show that the thermal neutron counting ratio can be accurately converted to the TNXS by density and the capture cross section of formations. The porosity calculated by TNXS is closer to the formation porosity than that calculated by the compensated neutron logging, especially in gas-bearing formations and complex lithologic formations.

It is believed that the cosmic-ray neutron sensor can be used to measure vegetation. We compare biomass water equivalent (BWE) to neutron counts from a cosmic-ray neutron sensor. We believe that the thermal neutrons will have a highly correlated inverse relationship with BWE. This is due to the ambient energy of thermal neutrons and the ability of hydrogen to capture them easily. Our results for soybean in 2017 showed that there was better correlation between raw fast neutron count $(\mathbf{R}^{2}= \mathbf{0.61})$ and BWE than raw thermal neutron count $(\mathbf{R}^{2}= \mathbf{0.21})$ . It would be ideal to explore this relationship of fast neutrons to BWE, with the addition of other hydrogen pools at the surface.

The time structure of neutron count rate enhancement during thunderstorm is studied. The enhancements take place during the time of atmospheric discharge. Significant part of neutrons is emitted in short bursts (200–400 μs). Sometimes the emission is well correlated over the space scale 1 km. Short burst width enables us to suppose that neutrons are generated mainly in a dense medium (probably soil).

In this paper artificial neural network based senso r informatics architecture has been investigated; i ncluding proposed continuous daily estimation of area wise surface soil moisture using cosmic ray sensor’s neutron count time serie s. Study was conducted based on cosmic ray data available from two Australian locat ions. The main focus of this study was to develop a data driven approach to convert neutron counts into area wise ground surfac e soil moisture estimates. Independent surface soil moisture data from the Australian Water Availability Project (AWAP) was us ed as ground truth. A comparative study using five different types of neural networks, namely, Feed Forward Back Propagation (FF BPN), Multi-Layer Perceptron (MLPN), Radial Basis F(RBFN), Elman (EN), and Probabilistic networks (PNN) was co nducted to evaluate the overall soil moisture estim ation accuracy. Best performance from the Elman network outperformed all other neural networks with 94% accuracy with 92% s ensitivity and 97% specificity based on Tullochgorum data. Overall hig h accuracy proved the effectiveness of the Elman ne ural network to estimate surface soil moisture continuously using cosmic ray sensors.

The divergent phenomenon of critical extrapolation and ρ–1/N extrapolation curve is analyzed during the physical startup of a reactor. Aiming at the deficiency of the existing improving method—constant neutron source elimination (CNSE) method, a new method—variable neutron source elimination (VNSE) is proposed. This new method aims at getting accurate neutron count rate for extrapolation, and considers all the errors caused by the neutron source leakage, reactor spatial effect and neutron detector positions as a whole. Applied to a small reactor, this VNSE method can remove all errors and eliminate the divergence of extrapolation so that the accurate ρ–1/N extrapolation curve is got. The VNSE method is efficient and accurate for the critical extrapolation.

The Modified Neutron Source Multiplication (MNSM) method, which is based on the extraction of the fundamental mode of neutron flux distribution, has been proposed to estimate subcriticality. It has been proven applicable to a small critical assembly and domestic PWRs during criticality approach. In the following study, it is also shown by numerical simulation that it is applicable to estimate the subcriticality using neutron count rate data during the control rod drop testing in PWRs. As the next step, we looked further into the actual data of neutron count rate in order to examine whether the expected signal response was observed for the estimation. It was found that the actual data have shown the expected response, and the control rod worth could have been estimated in the same manner as during criticality approach. A new procedure is also proposed to measure a reference reactivity that is essentially required to evaluate the reactivity of each control rod worth.

A Monte Carlo model was developed for our current neutron lifetime experiment using storage of ultracold neutrons (UCN) in a big gravitational trap. The model allows us to calculate neutron trajectories in the given geometry, taking into account gravity, and has been used in simulations that reproduce all stages of the experiment. The simulation was proven able to reproduce the time-dependence of the detected neutron count rates. For investigation of systematic effects, the value of the neutron lifetime resulting from the simulation of the experimental procedure was compared to the value entered as an input parameter. In particular, the systematic uncertainty associated with the method of calculating the effective UCN collision frequency in the trap was found not to exceed 0.1 s. In addition, calculations showed that up to 1% uncoated area of the copper trap has a negligible influence on the neutron lifetime result.

Measuring the reactivity of the accelerator-driven thorium reactor (ADTR) core accurately ensures safe, optimal performance of the reactor. The preferred method is to momentarily drop the accelerator beam current.

Applicability of the modified Neutron Source Multiplication (NSM) method with extraction of the fundamental mode to subcriticality measurement has been proposed. Following the feasibility verification in the previous study based on numerical analyses, its applicability has been proven in a more realistic situation; in a withdrawal sequence of control rod banks during the PWR startup. Subcriticalities with various control rod insertion configurations were estimated based on the modified NSM method. The subcriticality could be evaluated with a good accuracy even with the mockup experiment where any special treatments for accurate measurement were not taken into account and furthermore the insensitivity of measured signals by reactivity changes and their large fluctuations were seen. Based on this fact, we further investigated a feasibility to use neutron count rate data obtained during the control rod drop testing, which is carried out before the reactor physics tests at hot zero power condition. When it is proven that these data could be used for the estimation of each control rod worth, the following reactor physics tests could be performed with the advanced knowledge of each control rod worth and procedures for detailed control rod worth measurement could be simplified or eliminated from the reactor physics tests.

To overcome the difficulties of the conventional neutron source multiplication method, the authors have developed the Indirect Bias Estimation Method. This method obtains the bias in calculated K eff using the difference between measured and calculated neutron count rates. This bias in calculated K eff is used for an adjustment of the calculated K eff , deriving a truer K eff . Using neutron diffusion calculations, numerical experiments simulating the neutron source multiplication method were performed to validate this method. It could be shown how closely a true K eff can be reproduced using this method. It was found that an accurate estimation of subcriticality requires neutron count rate measurements at more than three locations.

This study combines soil moisture capacitance probes and cosmic-ray neutron probe with a Fuzzy Inference System to estimate variability of soil moisture in a ~28 ha circle over time. The technique demonstrates that the cosmic-ray neutron probe's average neutron count and a network of capacitance probes may be useful for estimating spatial and temporal variability in soil moisture patterns within the probe's footprint.

This chapter reviews the most significant developments that have taken place in the design, construction, and operation of new neutron sources as well as the refurbishment programs of others already serving the neutron-scattering community. Such advances in neutron production devices are to be considered in conjunction with impressive achievements in the optimization of neutron delivery systems as well as in neutron instrumentation which overall resulted in a truly remarkable improvement in neutron count rates. As a result, the capabilities of experimental neutron sources are nowadays larger than ever before, despite there being fewer sources available. It is also worth remarking the coming into line of compact, accelerator-driven neutron sources as well as work carried out at small research reactors which, as exemplified during the past decade, have played an important role in helping the large, user-based facilities to carry out development work geared toward the achievement of full performance.

A field study was conducted to examine the effect of the water content of potato tubers on the neutron count ratios of a neutron probe in an irrigated potato field. At the 20 cm depth, where tubers are concentrated, the neutron count ratios within the potato row (CW) were significantly higher than the neutron count ratios between the rows (CB). In contrast, the measured soil water contents within the rows (SW) at this depth, tended to be less than those measured between the rows (SB). At 45 cm depth, results were similar in a dry but not a wet year. The SW values, in contrast, were less than SB. Neither (CW-CB) or (SW-SB) were significant at 75 cm depth and values of (CW-CB) and (SW-SB) were similar. This study provides qualitative information regarding the influence of a potato tuber water content on neutron measurements, resulting in an overestimations of soil moisture in a potato field. Further studies should be conducted to develop relationships for corrections.

[1] During routine measurements of the background count rate of low-energy neutrons with a standard He-3 detector tube in the city of Sao Jose dos Campos, Brazil, we observed a sudden and sharp increase in the neutron count rate. This sharp increase was practically simultaneous with a lightning discharge that occurred in the vicinity of the tube detector. Since sources of spurious signals, such as malfunctioning equipment and electrical transients, have been eliminated as causes of the observed event, we are led to conclude that we possibly recorded a burst of neutrons associated with the lightning discharge.

We investigate the relation between Forbush cosmic ray decrease recovery time and coronal mass ejection transit time between the Sun and Earth. We identify 17 Forbush decreases from ground based neutron count rates between 1978 and 2003 that occur during the same phase in the solar cycle and can be associated with single coronal mass ejections (CMEs) in the SOHO LASCO CME Catalog or previously published reports, and with specific interplanetary coronal mass ejections (ICMEs) crossing the vicinity of Earth. We find an anti-correlation between Forbush recovery times and CME transit time that contradicts the predictions of simple cosmic ray diffusive barrier models. The anti-correlation suggests that the decay rate of ICMEs is anti-correlated with their travel speed. Forbush recovery times range from seven times the transit time for the fastest disturbance to a fifth the Sun-Earth transit time for the slowest. To account for the large range of measured recovery times we infer that the slowest disturbances must decay rapidly with radius whereas the fastest ones must remain strong. The longest recovery times suggest that the fastest disturbances in our sample decayed less rapidly with radius than the ambient solar wind magnetic field strength.

Multivariate correlations developed via radial-basis function (RBF) network analysis of a modern suite of logs are used to estimate crossplot density-neutron porosity and pseudo-deep resistivity from 1950's vintage well logs. Historically, porosity has been estimated with the logarithm of the neutron count rate standardized with a 2% porosity tight spot and a maximum porosity of ~40% in a shale stringer. Despite a frequently observed visual correlation of the gamma ray track with the neutron count rate, the gamma ray log information is not included in conventional porosity estimates. The visual comparison of the openhole gamma ray and the neutron porosity to the shape of the crossplot porosity from a new well, Foster 4, is similar to the pattern seen between the old gamma ray and the neutron-count rate logs. The new log data were investigated with various RBF networks to correlate the gamma ray and neutron-count rate with the crossplot porosity. An optimal RBF network was then used to estimate the crossplot porosity of the Penrose sand for 22 wells in the Reed Sanderson Unit where only cased-hole gamma ray and neutron-count rate logs are available. An equation converts the modern neutron log to the old style neutron count rate while providing a normalized input to the network training. The "goodness" of the RBF network predictions was validated via exclusion testing. A similar procedure was used to estimate a pseudo-deep resistivity in old wells. The study indicated that a carefully trained RBF network could identify the high resistivity intervals (shale stringers) with only gamma ray and neutron count rate used as the network inputs. The methodology presented should prove useful to others faced with characterizing old fields.

The divergence of the variance and covariance of the neutron counts in a critical reactor has been investigated in the usual one-speed point-reactor model, explicitly taking into account the delayed neutrons. The statistical approach is based upon the Kolmogorov and Dmitriev theory of the branching stochastic processes, making use of the probability-generating-function formalism. The analysis is performed by considering an ensemble of critical reactors steady at the same power level—an effect of the control system having been in operation for a long time. At the start of the experiment the reactors are left free to drift in the absence of any feedback mechanism. The influence of the assumptions of the initial distributions of the neutron and precursor populations is investigated and found to be negligible. After an initial transient lasting for a time of the order of the inverse of the Rossi-α, both the variance and covariance linearly increase with time with a common slope. From a mathematical point of view, in the limit of time going to infinity, they obviously diverge, giving rise to the ‘critical catastrophe’. However, in actual experiments lasting a few tens of seconds, the relative increase is confirmed to be negligible.

The Feynman method of analyzing a neutron flux has been widely used to characterize systems in which fission neutrons are present. John T. Caldwell of the Advanced Nuclear Technology group of the Los Alamos National Laboratory proposes a variation of this technique in which each sample gate is initiated by a neutron count. We compared the two methods for a few specific cases and find the second method markedly superior. Moreover, it is possible to combine the two methods and obtain information about a single chains that is not available when either method is used along. For example, the combined methods permit us, without knowing the counter efficiency, to estimate the fraction of fission neutrons in an unknown neutron flux.

A general approach to the application of neutron count moment analysis to passive assay is presented. The higher moments of the neutron count distribution are derived with the aid of the probabilit...

A mathematical model is derived for the probability distribution of neutron signal multiples inside randomly and signal triggered time intervals for a generalized time response function of the neut...

The construction of a monochromator- and analyser-crystal system with variable horizontal curvature is described. Experiments with the triple-axis spectrometer at the reactor Saphir showed an increase of the neutron count rates by more than an order of magnitude without appreciable loss in energy resolution.

The effect of the size of cylindrical containers filled with soil on the calibration of two types of neutron probes was investigated for moisture contents up to 0.25 volume fraction. Neutron count rates were appreciably affected by the value of both diameter and height up to 3 feet. Differences between 3 and 4 feet were small. The response of the end-source probe was linear within the range investigated (0 to 0.40 volume fraction). The data also show that the end-source probe design as compared with the centered-source design is more efficient and, therefore, requires a smaller radioactive source for equal precision. Once an accurate calibration with soil is available, verifying calibration of probes may be done with NaCl or H3BO3 solutions, limited to probes of identical design but differing efficiencies or source strengths. Relations found between soil moisture content and solution concentration are given. A discussion of the range of measurement of soil moisture content with neutron probes is presented, comparing various literature data. View complete article To view this complete article, insert Disc 2 then click button8

Initial use of the TRIPOLI code at Oak Ridge National Laboratory (ORNL) involves calculation of sample problems for both neutron and gamma-rays. Comparison with existing MORSE results indicates that the computing efficiency of TRIPOLI is somewhat better for the problems studied. Calculation of a thick (90cm) concrete and steel ingetral experiment with TRIPOLI gives good agreement with the experimental results. This calculation involved the neutron count rate and unfolded energy spectra as measured in an NE213 detector behind the sample. It was necessary to expand the standard TRIPOLI cross section energy structure near the 2.3 MeV minimum in the total cross section of oxygen (a major constitutent of concrete) to correctly calculate the count rate near this energy.

A neutron counting method for inspecting borosilicate glass Raschig rings and an apparatus designed specifically for this method are discussed. The neutron count ratios for rings of a given thickness show a linear correlation to the boron oxide content of the rings. The count ratio also has a linear relationship to the thickness of rings of a given boron oxide content. Consequently, the experimentally-determined count ratio and physically-measured thickness of Raschig rings can be used to statistically predict their boron oxide content and determine whether or not they meet quality control acceptance criteria.

The first observation of the statistical fluctuations of the number of neutrons in a reactor was the now famous Rossi-alpha experiment, named for Bruno Rossi who suggested and set up the measuring apparatus during the early days of Los Alamos. The original theoretical studies were formulated by Fermi, Feynman and de Hoffmann in 1944 (1) and again by de Hoffman (1946) (2) during the same period and issued in two Los Alamos reports: LADC-269 and LADC-256, respectively. Like most of the scientific and literary production of the time, the above-mentioned reports remained classified for several years.