Low-level Neutron Research Articles

Investigation of the Impact of Thermal Acute Low-level Neutron Radiation on Various Hematological Parameters and Lipid Profiles in Rats.

Investigation of the Impact of Thermal Acute Low-level Neutron Radiation on Various Hematological Parameters and Lipid Profiles in Rats.

Defects and structural changes of graphite-rich media subjected to low-level neutron doses for radiation dosimetry

Using commercially available, 0.3 mm thick rod-shaped, highly uniform 2B and HB grade polymer pencil lead graphite (PPLG), and subjected to a low-level neutron dose range of 2–10 Gy, a comprehensive understanding of radiation-induced effects have been achieved. The thermoluminescence (TL) and photoluminescence (PL) dose dependency, as well as changes in Raman spectroscopic characteristics, have been studied in order to understand the nature and distribution of defects in its crystal lattice structures that produce the luminescence signal. The atomic spacing, lattice constant, and the degree of structural order of the irradiated samples have been the primary focuses of the X-ray diffraction (XRD) study, which has then been followed by crystallite size calculations. The findings make it abundantly evident that neutron irradiation of different doses leads to some structural alteration in the studied sample at the microscopic level. Within the investigated dose range, all of the samples displayed an excellent linear response, with the sensitivity of the 2B grade PPLG being significantly higher than that of the HB. The findings show that the PPLG can be employed as a dosimetric medium for neutron radiation field. PPLG can provide a low-cost, highly effective system for researching radiation-driven changes in carbon, and all results anticipate 2B grade of PPLG to be a valuable material for new generation radiation dosimetry.

Structural and Optical Properties of Graphite-Rich Media Under Low Level Neutron Doses for Radiation Dosimetry

Structural and Optical Properties of Graphite-Rich Media Under Low Level Neutron Doses for Radiation Dosimetry

DETERMINATION OF THE BACKGROUND OF 3He-FILLED PROPORTIONAL COUNTERS USED FOR LOW-LEVEL NEUTRON MEASUREMENTS

Low-level neutron measurements are required for applications such as environmental monitoring, measurements of weak sources and the determination of neutron fluxes at underground laboratories. When analyzing low-level neutron measurements, it is important to be able to distinguish the signal due to neutrons from any background term that may originate within the detector. A solution to this problem has been developed for the case of measurements carried out with 3He spherical proportional counters of the type which are often used in Bonner sphere spectrometers. To determine this background, measurements were carried out in the former UDO underground laboratory of the Physikalisch-Technische Bundesanstalt located in the Asse salt mine. The analysis of the data was carried out using Bayesian parameter estimation. The result of the analysis is a very general parameterised function that can be used to describe the pulse height spectrum due to the background of the proportional counters.

Effect of Radiation on the Transmission Rate of Emission Intensity of Optical Fiber Cable Used in a Nuclear Material Facility

The performance and eligibility of the fiber optic laser-induced breakdown spectroscopy (FO-LIBS) instrument will be primarily evaluated at the Advanced Spent Fuel Conditioning Process Facility (ACPF), where spent nuclear fuel is processed in a high-temperature molten salt bath using electrochemical methods. The damage incurred by the optical fiber cable due to radiation should be addressed to ensure the reliability of FO-LIBS measurements. High-level and low-level gamma ray and neutron irradiation experiments were conducted to measure the effect of radiation on the optical transmission rate of the optical fiber cable. Conclusively, we determined the dependence of the transmission rate of the cable on the radiation dose rate as a function of the wavelength.

The Development of a High Sensitivity Neutron Displacement Damage Sensor

The capability to characterize the neutron energy spectrum and fluence received by a test object is crucial to understanding the damage effects observed in electronic components. For nuclear research reactors and high energy density physics facilities this can pose exceptional challenges, especially with low level neutron fluences. An ASTM test method for characterizing neutron environments utilizes the 2N2222A transistor as a 1-MeV equivalent neutron fluence sensor and is applicable for environments with $1 \times 10^{12} - 1 \times 10^{14}\,\,1$ -MeV(Si)-Eqv.-n/cm2. In this work we seek to extend the range of this test method to lower fluence environments utilizing the 2N1486 transistor. The 2N1486 is shown to be an effective neutron displacement damage sensor as low as $1 \times 10^{10}\,\,1$ -MeV(Si)-Eqv.-n/cm2.

Measurement and simulation of cosmic rays effects on neutron multiplicity counting

Neutron coincidence and multiplicity counting is a standard technique used to measure uranium and plutonium masses in unknown samples for nuclear safeguards purposes, but background sources of radiation can obscure the results. In particular, high energy cosmic rays can produce large coincidence count contributions. Since some of the events occur in the sample itself, it is impossible to measure the background separately. This effect greatly increases the limit of detection of some low level neutron coincidence counting applications.The cosmic ray capability of MCNP6 was used to calculate the expected coincidence rates from cosmic rays for different sample configurations and experimental measurements were conducted for comparison. Uranium enriched to 66%, lead bricks, and an empty detector were measured in the mini Epithermal Neutron Multiplicity Counter, and MCNP6 simulations were made of the same measurements. The results show that the capability is adequate for predicting the expected background rates.Additional verification of MCNP6 was given by comparison of particle production rates to other publications, increasing confidence in MCNP6׳s use as a tool to lower the limit of detection. MCNP6 was then used to find particle and source information that would be difficult to detect experimentally. The coincidence count contribution was broken down by particle type for singles, doubles, and triples rates. The coincidence count contribution was broken down by source, from(a,n), spontaneous fission, and cosmic rays, for each multiplicity.

FLUOLE-2: An Experiment for PWR Pressure Vessel Surveillance

FLUOLE-2 is a benchmark-type experiment dedicated to 900 and 1450MWe PWR vessels surveillance dosimetry. This two-year program started in 2014 and will end in 2015. It will provide precise experimental data for the validation of the neutron spectrum propagation calculation from core to vessel. It is composed of a square core surrounded by a stainless steel baffle and internals: PWR barrel is simulated by steel structures leading to different steel-water slides; two steel components stand for a surveillance capsule holder and for a part of the pressure vessel. Measurement locations are available on the whole experimental structure. The experimental knowledge of core sources will be obtained by integral gamma scanning measurements directly on fuel pins. Reaction rates measured by calibrated fission chambers and a large set of dosimeters will give information on the neutron energy and spatial distributions. Due to the low level neutron flux of EOLE ZPR a special, high efficiency, calibrated gamma spectrometry device will be used for some dosimeters, allowing to measure an activity as low as 7. 10−2 Bq per sample. 103mRh activities will be measured on an absolute calibrated X spectrometry device. FLUOLE-2 experiment goal is to usefully complete the current experimental benchmarks database used for the validation of neutron calculation codes. This two-year program completes the initial FLUOLE program held in 2006–2007 in a geometry representative of 1300MWe PWR.

Estimation of low-level neutron dose-equivalent rate by using extrapolation method for a curie level Am–Be neutron source

Neutron radiation protection is an important research area because of the strong radiation biological effect of neutron field. The radiation dose of neutron is closely related to the neutron energy, and the connected relationship is a complex function of energy. For the low-level neutron radiation field (e.g. the Am–Be source), the commonly used commercial neutron dosimeter cannot always reflect the low-level dose rate, which is restricted by its own sensitivity limit and measuring range. In this paper, the intensity distribution of neutron field caused by a curie level Am–Be neutron source was investigated by measuring the count rates obtained through a 3He proportional counter at different locations around the source. The results indicate that the count rates outside of the source room are negligible compared with the count rates measured in the source room. In the source room, 3He proportional counter and neutron dosimeter were used to measure the count rates and dose rates respectively at different distances to the source. The results indicate that both the count rates and dose rates decrease exponentially with the increasing distance, and the dose rates measured by a commercial dosimeter are in good agreement with the results calculated by the Geant4 simulation within the inherent errors recommended by ICRP and IEC. Further studies presented in this paper indicate that the low-level neutron dose equivalent rates in the source room increase exponentially with the increasing low-energy neutron count rates when the source is lifted from the shield with different radiation intensities. Based on this relationship as well as the count rates measured at larger distance to the source, the dose rates can be calculated approximately by the extrapolation method. This principle can be used to estimate the low level neutron dose values in the source room which cannot be measured directly by a commercial dosimeter.

Low-level gamma and neutron monitoring based on use of proportional counter filled with 3He in polythene moderator: study of the responses to gamma and neutrons

It has been shown that a proportional counter filled with (3)He placed centrally inside a polythene sphere opens a new possibility for measuring gamma photons and neutrons in the separate pulse-height windows. The responses to gamma and neutrons (in terms of ambient dose equivalent) of the detector assembly consisting of 203-mm polythene sphere with centrally positioned 40-mm diameter (3)He proportional counter have been studied. The response to secondary gammas from capture process in hydrogen has also been studied. The rather preliminary studies indicate that the proposed measuring system has very promising features as an ambient dose equivalent device for mixed gamma-neutron fields.

Condensed matter nuclear science (cold fusion): an update

Seventeen years after the announcement by Professors Stanley Pons and Martin Fleischmann of the discovery of cold fusion in March 1989, the scientific community does not acknowledge this field as a genuine scientific research theme. However, the scientific demonstration of cold fusion was made long ago by showing the evidence of excess heat production in electrolytic cells and other devices. Also, nuclear ashes have been observed, mainly the formation of helium-4 along with the production of excess heat. What makes this field difficult to accept is the lack of the usual particle emission observed in nuclear science or high-energy physics. In some instances low-level neutron production, X-ray emission and transmutation of elements have been measured. At this point there is no satisfactory theory explaining the unique characteristics of condensed matter nuclear science. Many models have been proposed, several of them using textbook physics.

Limitation on the response of 3He counters due to intrinsic alpha emission

Alpha-emitters in the uranium and thorium series, present as trace elements in the construction materials of 3He detectors, can result in a highly significant count rate when these detectors are used for low-level neutron flux measurements. This is confirmed for a detector with a uranium content of only 5.72×10 −8 g/g. It is shown that measurement of the contribution of the internal background to total count is not readily possible in an above-ground environment. However, a deep underground laboratory, where the effects of cosmic rays become insignificant, is an ideal location for such measurements. It is shown that the pulse heights due to alpha particles are suppressed because of electron ion recombination in the detector. The observed internal alpha background in 3He detectors is consistent with Monte Carlo simulation.

Electrical conductivities and dielectric constants of some sodium tetraborate glasses containing CuO, irradiated with a low-level fast neutron beam

A number of glass samples were prepared from a mixture of Na2B4O7 and CuO. The prepared glasses were irradiated with a low-level fast neutron beam (flux density 108 n cm-2). The alternating current (a.c.)-electrical conductivity and the dielectric constant at a frequency of 1 kHz of these glasses have been studied as a function of temperature in the range 300–600 K. The measurements showed that an amorphous–crystalline phase transition characterized these samples. This phase transition was affected by neutron irradiation. Also a decrease in the activation energy for the irradiated undoped sample and an increase in the activation energy for the irradiated doped samples were found. After irradiation, the maximum peak, which characterized the dielectric constant of the samples before irradiation, disappeared. © 1998 Chapman & Hall

Measurement of neutron dose by a moderating germanium detector

A moderating neutron detection system based on measurement of the neutron-induced prompt gamma rays in a central germanium detector was established to measure low-level neutron dose rates. Fast neutrons are moderated in polyethylene cylinders and then captured in the germanium crystal for counting. The neutron dose rate is estimated by measuring the most intense capture prompt gamma ray of 596 keV in the Ge(n th,γ) reaction, The moderating neutron dosimeter shows high detection sensitivity to neutrons, exceeding other reported germanium-based neutron detection devices. It can be practically used for measurement of the neutron dose rate of environmental neutrons.

Palm-size low-level neutron sensor for radiation monitoring

We have developed a new technique for the detection of neutrons in the presence of a high gamma-ray background. This was accomplished by using two lithium-loaded glass scintillators (/sup 6/Li//sup 7/Li) in combination. The neutron capture reaction in /sup 6/Li has a very high Q-value which means better discrimination against gamma-ray background. The /sup 7/Li detector, on the other hand, is neutron insensitive and was used to measure separately the gamma contribution in a mixed neutron-gamma field. By subtracting this gamma contribution from the /sup 6/Li data, which is sensitive to both gamma rays and neutrons, one can obtain the pure neutron counts.

Low Level Neutron Monitoring Using High Pressure 3He Detectors

Three detectors two spherical proportional counters and an ionisation chamber, all filled with 3He to pressures of 160kPa, 325kPa and 1 MPa respectively have been experimentally studied with respect to their use for low level neutron monitoring. The ambient dose equivalent responses and the energy resolutions of these detectors have been determined. It is shown that spectral analysis of the signals from these detectors not only gives high sensitivity with regard to ambient dose equivalent but also improves the quality of the measurements. A special instrumentation for low level neutron monitoring is described in which a quality control method has been implemented.

硝酸セルロースフィルムを検出器とした放電計数による低中性子線量の測定 特に医療用ＬＩＮＡＣの漏洩中性子線量の推定

硝酸セルロースフィルムを検出器とした放電計数による低中性子線量の測定 特に医療用ＬＩＮＡＣの漏洩中性子線量の推定

Anomalous nuclear effects in solids ("cold fusion"): questions still remain

The results are discussed of recent experiments to detect the nuclear products of cold fusion (neutrons, tritium, and helium) and their possible theoretical interpretation. Apparently low-level neutron emission has been established rather reliably and can be understood without adducing exotic models. The results on tritium and helium require further refinement and as yet have not received a satisfactory theoretical explanation.

Low-level neutron monitoring by use of germanium detectors

The detection sensitivity of various size germanium detectors to low-level neutron dose equivalent rate is described. Six high-purity germanium detectors with a crystal volume of 60 to 120 cm 3 were irradiated by neutrons produced from a 0.76 μg 252Cf isotopic neutron source. The counting rate of the prompt gamma rays of 596 keV was used to determine the detecting sensitivities of the detectors. The results show that the detecting sensitivity of the HPGe detector decreases with increasing detector size, and approximately proportional to the crystal volume.

A design study of detectors for low-level neutrons

Abstract Low-level neutron detectors were designed by using NE213 scintillator employing well-type geometry. The relative error of net neutron counts for a 24 h measurement for a source intensity of 0.41 neutrons/s could be less than 2%, which is much smaller than conventional moderating 6 Li and 3 He neutron detectors.