Beryllium Neutron Source Research Articles

Systematic evaluation of fast neutron sensing with Cesium Hafnium Chloride

Cesium Hafnium Chloride (CHC) is a promising new scintillator for dual mode sensing of both neutrons and gamma-rays. The high chlorine content allows for both 35Cl(n,p)35S and 35Cl(n, α)32P reaction channels leading to reliable detection of fast neutrons. By utilizing pulse shape discrimination (PSD), these neutron interactions may be reliably separated from gamma-ray signals with a high figure-of-merit (FOM) after optimization of the PSD algorithm. In this study, the PSD algorithm settings for CHC were systematically investigated using a bare 252Cf and a lead-shielded plutonium beryllium neutron source. It was found that the PSD algorithm settings affects both the FOM and the neutron detection efficiency, but a FOM as high as 4.5 for alpha particles was observed in one data processing scenario. Further, an intrinsic 5 parts per million alpha-emitting contamination was observed in the sample, which we attribute to natural uranium.

Study on the Design, Preparation, and Performance Evaluation of Heat-Resistant Interlayer-Polyimide-Resin-Based Neutron-Shielding Materials.

Polymers have an excellent effect in terms of moderating fast neutrons with rich hydrogen and carbon, which plays an indispensable role in shielding devices. As the shielding of neutrons is typically accompanied by the generation of γ-rays, shielding materials are developed from monomers to multi-component composites, multi-layer structures, and even complex structures. In this paper, based on the typical multilayer structure, the integrated design of the shield component structure and the preparation and performance evaluation of the materials is carried out based on the design sample of the heat-resistant lightweight polymer-based interlayer. Through calculation, the component structure of the polymer-based materials and the three-layer thickness of the shield are obtained. The mass fraction of boron carbide accounts for 11% of the polymer-based material. Since the polymer-based material is the weak link of heat resistance of the multilayer shield, in terms of material selection and modification, the B4C/TiO2/polyimide molded plate was prepared by the hot-pressing method, and characterization analysis was conducted for its structure and properties. The results show that the ball milling method can mix the materials well and realize the uniform dispersion of B4C and TiO2 in the polyimide matrices. Boron carbide particles are evenly distributed in the material. Except for Ti, the other elemental content of the selected areas for mapping is in good agreement with the theoretical values of the elemental content of the system. The prepared B4C/TiO2/polyimide molded plate presents excellent thermal properties, and its glass transition temperature and initial thermal decomposition temperature are as high as 363.6 °C and 572.8 °C, respectively. In addition, the molded plate has good toughness performs well in compression resistance, shock resistance, and thermal aging resistance, which allows it to be used for a long time under 300 °C. Finally, the prepared materials are tested experimentally on an americium beryllium neutron source. The experimental results match the simulation results well.

Neutron shielding properties of TPX/B4C composites based on Monte Carlo method

As the key and difficult point of shielding protection, many domestic and foreign scholars have carried out a lot of experimental research on neutron shielding materials. In this paper, the research progress, advantages and disadvantages of common neutron shielding materials are discussed, and the neutron shielding process of TPX/B4C composites is simulated by Monte Carlo method, and the results are compared with the Boron polyethylene, lead boron polyethylene, aluminum based boron carbide mentioned in the literature. Based on the simulation results, it is concluded that the thermal neutron absorption rate of TPX/B4C composites with the thickness of 1cm is 98.3%, the fast neutron shielding rate of 1MeV is 1.457, and the neutron shielding reduction factor and neutron dose reduction factor of americium beryllium neutron source are obviously better than the other three materials. The simulation results show that TPX/B4C Composite can be used as a new kind of high temperature neutron shielding material.

Characterization of a plutonium–beryllium neutron source

Here we present an investigation of a plutonium–beryllium neutron source available at the Horia Hulubei National Institute of Physics and Nuclear Engineering, Romania, to be used for detector characterization during the implementation of the Extreme Light Infrastructure – Nuclear Physics project. Using several different techniques and instruments, we have measured the isotopic composition for plutonium to be 75% 239Pu and 24% 240Pu, with a minor contribution from other isotopes. Furthermore, we have measured the source activity as of November 20th 2019 to be 2.220(5)×105 neutrons per second with a mean energy of 3.25(17) MeV. We have also measured both the γ-tagged and full neutron energy spectra, and discuss the origin of the observed structure in the neutron energies based on these. All these parameters are of importance both for traceability of nuclear material, radioprotection, and accurate detector characterization.

A Fizikai Intézet Ra-Be neutronforrásának felhasználása és eltemetése

The period of service of our laboratory Radium-226 – Beryllium neutron source, used in our education for 44 years, is expired so its disposal became necessary. The disassembling of the source, its preparation for disposal was a unique, professional challenge. In this paper, we show the performance of this work, with regard to the referring regulations. On the basis of our measurements we delivered an uninjured closed isotope to the radioactive waste disposal facility.

Neutron spectrometry of a lightly encapsulated 241Americium–beryllium neutron source using two different Bonner Sphere Spectrometers

Abstract 241Americium–beryllium neutron sources are used in a variety of applications, spanning from the civil engineering to the oil industry, and to the radiation dosimetry. The ISO 8529-1 Standard reports a reference distribution for the energy of the emitted neutrons, which extends from 0.1 to 11 MeV. Nevertheless every source exhibits a slightly different spectrum, depending on the material and dimension of the capsule, and on the amount of active material. This source-to-source variability is expected to mainly affect the energy region below 0.1 MeV. As these differences can be important in the fields of neutron dosimetry and metrology, some relevant source formats have been investigated with spectrometric methods. The neutron calibration laboratory of the Politecnico di Milano recently acquired a CZ/1003/S — 96 type 241 Am–Be source (nominal emission rate 2.2E+6 s−1). As this type of source is in use in a number of European laboratories, its spectrum was determined through a neutron spectrometry experiment, involving two Bonner sphere spectrometers with well-known responses. The experimental spectrum is compared to that published for a similar source and to the ISO-recommended one.

Beam dynamics and commissioning of CW RFQ for a compact deuteron–beryllium neutron source

The Institute of Modern Physics (IMP) of the Chinese Academy of Sciences (CAS) is building a compact neutron source using a superconducting linac. The injector RFQ will operate in continuous wave (CW) mode, accelerating a 10-mA deuteron beam from 20 keV/u to 1.5 MeV/u. To minimize the possibility of beam loss in the downstream superconducting linac and maintain high acceleration efficiency, we take the 99.9% longitudinal beam emittance as the key optimization parameter for the beam dynamics design of the RFQ, and include an internal buncher to reduce the longitudinal beam emittance. This paper describes the design procedures, beam dynamics simulations and preliminary beam commissioning results for this RFQ. Simulation results show that 99.9% longitudinal beam emittance at the RFQ exit is optimized to 3.5 pi mm mrad, which is 0.13 times the longitudinal acceptance of the downstream superconducting linac. Beam commissioning results demonstrate that the RFQ can accelerate 7.8 mA H2+ to 3.11 MeV. The transmission efficiency from a Faraday cup before the RFQ to the beam dump after the RFQ is 97.6%. The measured transmission efficiency agrees well with simulation results at different values for the inter-vane voltage.

Chemical investigation of three plutonium–beryllium neutron sources

Thorough physical and chemical characterization of plutonium–beryllium (PuBe) neutron sources is an important capability with applications ranging from material accountancy to nuclear forensics. Characterization of PuBe sources is not trivial owing to range of existing source designs and the need for adequate infrastructure to deal with radiation and protect the analyst. This study demonstrates a method for characterization of three PuBe sources that includes physical inspection and imaging followed by controlled disassembly and destructive analysis.

Developments for neutron-induced fission at IGISOL-4

At the IGISOL-4 facility, neutron-rich, medium mass nuclei have usually been produced via charged particle-induced fission of natural uranium and thorium. Neutron-induced fission is expected to have a higher production cross section of the most neutron-rich species. Development of a neutron source along with a new ion guide continues to be one of the major goals since the commissioning of IGISOL-4. Neutron intensities at different angles from a beryllium neutron source have been measured in an on-line experiment with a 30MeV proton beam. Recently, the new ion guide coupled to the neutron source has been tested as well. Details of the neutron source and ion guide design together with preliminary results from the first neutron-induced fission experiment at IGISOL-4 are presented in this report.

Neutron producing reactions in PuBe neutron sources

There are a plenty of out-of-use plutonium–beryllium neutron sources in Eastern Europe presenting both nuclear safeguards and security issues. Typically, their actual Pu content is not known. In the last couple of years different non-destructive methods were developed for their characterization. For such methods detailed knowledge of the nuclear reactions taking place within the source is necessary. In this paper we investigate the role of the neutron producing reactions, their contribution to the neutron yield and their dependence on the properties of the source.

Elemental composition in sealed plutonium–beryllium neutron sources

Five sealed plutonium–beryllium (PuBe) neutron sources from various manufacturers were disassembled. Destructive chemical analyses for recovered PuBe materials were conducted for disposition purposes. A dissolution method for PuBe alloys was developed for quantitative plutonium (Pu) and beryllium (Be) assay. Quantitation of Be and trace elements was performed using plasma based spectroscopic instruments, namely inductively coupled plasma mass spectrometry (ICP-MS) and atomic emission spectrometry (ICP-AES). Pu assay was accomplished by an electrochemical method. Variations in trace elemental contents among the five PuBe sources are discussed.

Investigation of the neutron spectrum of americium–beryllium sources by Bonner sphere spectrometry

Americium–beryllium neutron sources are certainly the most widely used in neutron dosimetry laboratories, basically due to their long half-life and their energy distribution, which covers the energy domain of interest for many applications in ambient and personal dosimetry. Nevertheless, the spectrum of this source depends on the materials and dimension of the capsule and on the amount and physical–chemical properties of the active material, thus affecting relevant quantities such as the spectrum-averaged fluence-to-dose equivalent conversion coefficient. A EURAMET (European Association of National Metrology Institutes) project (n. 1104) was initiated to experimentally investigate how the neutron spectrum changes for different source sizes and encapsulations with a view to providing improved data for a planned revision of the ISO 8529 Standard Series. The experimental campaign was carried out in the low scatter facility at NPL. Here three different Bonner sphere spectrometers, BSSs, were exposed to the neutron fields produced by three different neutron sources formats: one X3 capsule (1Ci) and two X14 capsules (10Ci and 15Ci). The specific advantage of the BSS is the large sensitivity to low-energy neutrons (E<0.1MeV) which is the component expected to be most affected by the capsule-to-capsule variations and the component which is least well known.This paper summarises the results of the campaign with emphasis on (1) estimating the low-energy component of the Am–Be neutron spectrum, according to the encapsulation type; (2) evaluating the coherence between the Bonner spheres data and the previous studies performed with high-resolution spectrometers but limited in energy to E>0.1MeV; (3) understanding whether the ISO-recommended Am–Be spectrum needs to be amended, and for which source formats.

Study of the gamma spectrum of 16N with a BGO detector, for the purpose of calibration and of determining the fluorine grade of mineral samples

The study of 16N’s gamma spectrum has two main uses: calibrating gamma detectors in a high energy range, and determining the fluorine grade of mineral samples of fluorite. This article examines and compares the gamma ray spectrum of 16N as recorded by a Bi4GeO12 detector, as well as the resolution of this detector at high energy levels, and the signal–background relationship of an experimental laboratory cyclic activation unit. 16N is the product of the reaction 9-F-19(n,α)7-N-16, which takes place during the neutron activation of mineral samples of fluorspar, and its production depends, among other factors, upon the grade of fluorite. The technique used in this study is cyclic-type neutron activation for recording delayed gamma rays, carried out with an americium–beryllium neutron source with an activity of 1 Ci. Lastly, a correlation is established between the area below the peak amount of 16N emitted by the sample, and the sample’s fluorite grade.

The Bonebrake Theological Seminary: Top-Secret Manhattan Project Site

We discuss the top-secret Manhattan Project site established at the Bonebrake Theological Seminary in 1943 in Dayton, Ohio, where research on polonium and its production was carried out. The polonium produced there was then transported to Los Alamos to be used in a polonium–beryllium neutron source whose purpose was to ignite the plutonium implosion bomb that would be dropped on Nagasaki, Japan, on August 9, 1945. Our account is based primarily on the recollections of John J. Sopka, research physicist at the Bonebrake laboratory.

Production of 16N and obtaining of its gamma spectrum in order to calibrate detectors or determination of fluorine in geological specimens

In this paper, we show a procedure for producing 16N and a method to obtain its gamma spectrum with a NaI(Tl) detector. We also demonstrate the interest of this radioactive element for the purpose of NaI(Tl) detector calibration and for the determination of fluorine in geological specimens using an Alpha Beryllium neutron source. This work consists of a theoretical study which analyzes the characteristics of 16N and nuclear reactions that originate from an Americium Beryllium source of 1Ci activity. We justify our choice of reaction 19F(n,α) 16N and the use of fluorspar as a source of fluorine. The mathematical procedure followed to obtain the gamma rays spectrum produced by 16N in a NaI(Tl) detector is shown.

Characterization of a sealed Americium–Beryllium (AmBe) source by inductively coupled plasma mass spectrometry

Two Americium–Beryllium neutron sources were dismantled, sampled (sub-sampled) and analyzed via inductively coupled plasma mass spectrometry (ICP-MS). Characteristics such as “age” since purification, actinide content, trace metal content and inter and intra source composition were determined. The “age” since purification of the two sources was determined to be 25.0 and 25.4 years, respectively. The systematic uncertainties in the “age” determination were ±4% 2σ. The amount and isotopic composition of U and Pu varied substantially between the sub-samples of Source 2 (n = 8). This may be due to the physical means of sub-sampling or the way the source was manufactured. Source 1 was much more consistent in terms of content and isotopic composition (n = 3 sub-samples). The Be–Am ratio varied greatly between the two sources. Source 1 had an Am–Be ratio of 6.3 ± 52% (1σ). Source 2 had an Am–Be ratio of 9.81 ± 3.5% (1σ). In addition, the trace element content between the samples varied greatly. Significant differences were determined between Sources 1 and 2 for Sc, Sr, Y, Zr, Mo, Ba and W.

Improved activation tests of fusion structural materials with a deuteron–beryllium neutron source

In the framework of the European Activation File (EAF) task of the European Fusion Technology Programme, the EAF data relevant to the steel types F82H-mod and MANET-2 were benchmarked experimentally. Samples were activated in an intense neutron field produced in a thick beryllium target by a 19-MeV deuteron beam of the Karlsruhe Isochron-Zyklotron. The irradiated samples were investigated by γ spectrometry. The results were compared with calculations using the FISPACT code, the EAF-4.1 library and the source neutron spectrum as measured by activation foil dosimetry. Calculation-over-experiment ratios between 0.96 and 1.19 are found for the more important medium-halflife radionuclides produced in F82H-mod. Similar values are found for MANET-2.

A 7–9 MeV isotopic gamma-ray source for detector testing

An isotopic source of high-energy gamma rays has been constructed and tested. The source uses either a long-lived americium–beryllium neutron source or 252Cf to produce fast neutrons, which are moderated in paraffin and then absorbed in metallic nickel. The radiative capture of thermal neutrons in natural metallic Ni produced five prominent gamma-ray energies in the range 7.5–9 MeV, of which the 8.997 MeV line is the strongest by more than a factor of two. The source was optimized for counting rate by measuring gamma-ray energy spectra with a 76 mm diam. NaI detector, then used to test an imaging BGO detector with gamma rays in the energy range 7.5–9 MeV.

The Shale-Compensated Chlorine Log

Although many chlorine logging systems have been used by the petroleum industry, they never attained widespread popularity. The use of many of these systems was limited by their sensitivity to increasing shale content. A shale-compensated chlorine logging system (SCC) has been developed and evaluated. The SCC log interpretation has proven to be correct in predicting the type of fluid behind the casing more than 80 percent of the time. Introduction The chlorine log was introduced to the petroleum industry in the late 1950's. The primary purpose of this log was to determine the amount of salt water in the formations immediately behind the production casing and to relate this salinity measurement to hydrocarbon content. Although many chlorine logging systems were used by industry,1–4 they never attained widespread popularity. The use of many of these systems was limited by their sensitivity to increasing shale content. A shale-compensated chlorine logging system (SCC)5 has been developed and extensively evaluated. The recorded log supplies a continuous salinity profile of the formations behind the casing. A specific advantage of this log over other similar logs is that the system compensates for the effect of shale on the salinity measurement. Also, the porosity, lithologic, and borehole fluid effects on the salinity measurement are minimized. The log has been run in several hundred cased wells. The majority of the runs have been made in wells subject to workover and/or abandonment. New hydrocarbon-bearing intervals have been identified and oil-water contacts in producing reservoirs have been located. The SCC log interpretation has proven to be correct in predicting the type of fluid behind the casing more than 80 percent of the time. Oil production has been obtained in many wells that, before logging, were considered to have little, if any, economic potential. The SCC log will give reliable results at logging speeds of 20 to 30 ft/min in formations containing high porosity and salinities above 45,000 ppm NaCl. Slower logging speeds are recommended for areas where porosities are low and/or salinities are less than 45,000 ppm NaCl. The possibility of successful completions based on the log interpretation decreases rapidly when porosities are less than 20 percent and formation salinities are below 30,000 ppm NaCl. Tool Design The SCC system was specifically designed to minimize the effects of shaliness, porosity, and lithology on formation salinity measurements and water saturation (Sw) determinations. The system measures thermal neutron-capture gamma radiation in two gamma ray energy ranges: 1.3 to 2.92 MeV, recorded as the NG (Hydrogen) curve, and all gamma ray energies above 3.43 MeV, recorded as the NG (Chlorine) curve. The detector is a 2-in. by 4-in. long NaI(Tl) scintillation detector that is spaced 15¾in. (center to center) from a 2.3 × 107 neutron / americium - beryllium neutron source. Lead is used as shielding material between neutron source and detector.

Untersuchungen zum verallgemeinerten Albedo‐Problem

AbstractMit Hilfe einer 500 mC Ra–Be‐Neutronenquelle in einer Paraffinanordnung wurden Untersuchungen durchgeführt, die Aufschluß über die Genauigkeit theoretischer Betrachtungen zum verallgemeinerten Albedo‐Problem bringen sollten. Die Ausmessung des Neutronenfeldes erfolgte mit Dysprosium‐Sonden. Aus den Meßergebnissen ergibt sich die Brauchbarkeit der Theorie, deren Anwendung bei anderen Diffusionsproblemen demnach durchaus gerechtfertigt ist.