DOCSLIB.ORG

Neutron Production and Absorption in Uranium

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Neutron Production and Absorption in Uranium Neutron Production and Absorption in Uranium H. L. A11."'DERSON, E. FERMI AND LEo SziLARD Reprinted from THE PHYSICAL REVIEW, Vol. 56, No. 3, August 1, 1939 AUGUST 1, 1939 PHYSICAL REVIEW VOLUME 56 Printed in U. S. A. Neutron Production and Absorption in Uranium* H. L. ANDERSON, E. FER.liH AND LEo SziLARD Columbia University, New York, New York (Received July 3, 1939) 1 3 T has been found - that there is an abundant placed in the center of the tank. The geometry I emission of neutrons from uranium under the was such that practically all neutrons emitted action. of slow neutrons, and it is of interest to as­ by the source and by the uranium oxide were certain whether and to what extent the number of slowed down and absorbed within the tank. Each neutrons emitted exceeds the number absorbed. irradiation extended over several half-life periods This question can be investigated by placing a of radiomanganese and the observed activity of photo-neutron source in the center of a large the solution was about four times the back­ water tank and comparing, with and without ground of the ionization chamber. Alternating uranium in the water, the number of thermal measurements were taken with the cans filled neutrons present in the water. In the previous with uranium oxide, and with empty cans of the 1 experiments of this type • 3 it was attempted to same dimensions. The activity proved to be have as closely as possible a spherically sym­ about ten percent higher with uranium oxide metrical distribution of neutrons. The number of than without it. This result shows that in our thermal neutrons present in the water was de­ arrangement more neutrons are emitted by termined by measuring along one radius the uranium than are absorbed by uranium. neutron density p as a function of the distance r In order to find the average number of fast from the center, and then calculating fr2pdr. neutrons emitted by uranium for each thermal A difference in favor of uranium of about five neutron absorbed by urani percent was reported by von Halban, Joliot and um, we have to de­ Kovarski.4 termine what fraction of the total number of neutrons Since one has to measure a small difference, emitted by the photo-neutron source is, slight deviations from a spherically symmetrical in our experiment, absorbed in the thermal region by uranium. distribution might give misleading results. The The number of photo-neutrons present experiments which are based on the same general principle do not require such symmetry. In order to measure the number of thermal neutrons in the water we filled the tank with a ten-percent solution of MnS04. The activity in­ duced in manganese is proportional to the number 0000 of thermal neutrons present. A physical aver­ 000000 aging was performed by stirring the solution 00000000 before measuring the activity of a sample with an 0 0 O~Q?O 0 0-s ionization chamber. To obtain an effect of suffi­ oooo oooo cient magnitude, about 200 kg of U30s was used. 00000000 The experimental arrangement is shown in . 000000 Fig. 1. A photo-neutron source, consisting of 0000 about 2 g of radium and 250 g of beryllium was IOcm *Publi cation assisted by the Ernest Kempton Adams Fund for Physical Research of Columbia U niversity. tv. Halban, Joliot and Kovarski, Nature 143, 470 (1939). FIG. 1. Horizontal section through center of cylindrical 2 L. Szilard and W. H. Zinn, Phys. R ev. 55, 799 (1939). tank which is filled with 540 liters of 10-percent MnSO, a Anderson, Fermi and Hanstein, Phys. Rev. 55, 797 solution. A Photo-neutron source composed of 2.3 grams (1939). of radium ~nd 250 grams of beryllium. B, One of 52 cylin­ 4 v. Halban, Joliot and Kovarski, Nature 143, 680 drical cans 5 em in diameter and 60 em in height, which (1939). are either empty or fill ed with uranium oxide. 284 285 NEUTRON PRODUCTION AND ABSORPTIO emitted by the source is indicated by the activity section for neutron production and neutron ab­ of the solution in the tank when the irradiation sorption in uranium is greater than one, and is carried out with empty cans surrounding the probably about 1.5. \Nhat fraction of the neu­ source. Vve obt<~:ined a measure of this number by trons will reach thermal energies without being taking into accoun t that in our solution about absorbed will, however, depend on the ratio of 20 percent of the neutrons are captured by the average concentrations of hydrogen and manganese and the rest by hydrogen. In order to uranium. Since there is an appreciable absorption obtain , in the same units, a measure of the num­ even far from the center of the resonance band, ber of neutrons absorbed by uranium we pro­ it follows that the fraction of neutrons absorbed ceeded in the following way: A mixture of sand by uranium at resonance will increase with de­ and manganese powder, having the same thermal creasing hydrogen concentration. This has to be neutron absorption as uranium oxide replaced taken into account in discussing the possibility the uranium oxide in t of the cans which were of a nuclear distributed uniformly among the other uranium chain reaction in a system composed essentia oxide-filled cans. After irradiation, all this powder lly of uranium and hydrogen. A chain was mixed together, a ten-percent MnS04 solu­ reaction would require that more neutrons be tion was prepared from a sample, and its activity produced by uranium than absorbed by uranium was measured with our ionization chamber. and hydrogen together. In our experiment the In this way we found that about SO percent of ratio of the average concentration of hydrogen t he neutrons emitted by the source are absorbed to uranium atoms was 17 to 1, and in the experi­ as t hermal neutrons by uranium in our arrange­ ment of von Halban, Joliot and Kovarski this ment. It follows that, if uranium absorbed only ratio was 70 to 1. At such concentrations the thermal neutrons, the observed ten-percent in­ absorption of hydrogen in the t hermal region will crease in activity obtained with uranium present prevent a chain reaction. By reducing the con­ would correspond to an average emission of centration of hydrogen one would obtain the about 1.2 neutrons per thermal neutron absorbed following effect: On the one hand a larger fraction by uranium. This number should be increased, of those neutrons which reach thermal energies to perhaps 1.5, by taking into account the will be absorbed by uranium; on the other hand neutrons which, in our particular arrangement, fewer neutrons reach t he thermal region due to are absorbed at resonance in t he nonthermal an increased absorption by uranium at resonance. region by uranium, without causing neutron Of t hese two counteracting factors the first is emissiOn. more important for high h ydrogen concentra­ From this result we may conclude that a tions and the second is more important for low nuclear chain reaction could be maintained in a hydrogen concentrations. Starting with high system in which neutrons are slowed down with­ hydrogen concentrations, the ratio of neutron out much absorption until t hey reach thermal production to total neutron absorption will thus energies and are then mostly absorbed by ura­ first rise, t he~ pass through a maximum, and, nium rather than by another element. I t remains as the hydrogen concentration is decreased, there­ an open question, however, whether this holds after decrease. We attempted to estimate the for a system in which hydrogen is used for quantities involved from the information avail­ slowing down the neutrons. able about resonance absorption in uranium•-7 In such a system the absorption of neutrons and from the observed net gain of 0.2 in the takes place in three different ways: The neutrons number of neutrons in our experiment. The effect are absorbed at thermal energies, both by hydro­ of the absorption gen and uranium, and they are also absorbed by at resonance turns out to be so uranium at resonance before they are slowed 5 Meitner, Hahn and Strassman, Zeits. f. Physik 106, down to thermal energies. Our result is inde­ 249 (1937). pendent of the ratio of the concentrations of s v. Hal ban, Kovarski and Savitch, Comptes rend us hydrogen and uranium, insofar as it shows that, 208, 1396 (1939). 7 H. L. Anderson and E. Fermi, Phys. Rev. 55, 1106 for thermal neutrons, the ratio of the cross (1939). ANDERSON, FERMI AND SZILARD 286 large that even at the optimum concentration of We wish to thank Dr. D . W. Stewart, of the hydrogen it is at present quite uncertain whether Department of Chemistry, and [r. S. E. Krewer, neutron production will exceed the total neutron for advice and assistance in carrying out some of absorpt-ion. More information concerning the these experiments. We are much indebted to the resonance absorption of uranium as well as more Eldorado Radium Corporation for enabling us to accurate measurement of some of the values work with large quantities of uranium oxide in which enter into our calculation are required our experiments, and to the Association for before we can conclude whether a chain reaction Scientific Collaboration for the use of the photo­ is possible in mi.xtures of uranium and water. neutron source and other facilities. LANCASTER PRESS, INC., LANCASTER, PA. .
Load more

Recommended publications
  • MASTER 9700 South Cass Avenue Argonne, Illinois 60439 USA
    ANL/KDH—SO DE84 001440 ANL/NDM-80 NEUTRON TOTAL CROSS SECTION MEASUREMENTS IN THE ENERGY REGION FROM 47 key to 20 MeV* by W. P. Poenitz and J. F. Whalon Applied Physics Division May, 1983 *This work supported by the U.S. Department of Energy Argonne National Laboratory MASTER 9700 South Cass Avenue Argonne, Illinois 60439 USA fflSTRtBtfUOU OF miS DOCUMENT IS UNLIMITED NUCLEAR DATA AMD MEASUREMENTS SERIES The Nuclear Data and Measurements Series presents results of studies in the field of microscopic nuclear data. The primary objective is the dissemination of information in the comprehensive form required for nuclear technology applications. This Series is devoted to: a) measured microscopic nuclear parameters, b) experimental techniques and facilities employed in measurements, c) the analysis, correlation and interpretation of nuclear data, and d) the evaluation of nuclear data. Contributions to this Series are reviewed to assure technical competence and, unless otherwise stated, the contents can be formally referenced. This Series does not supplant formal journal publication but it does provide the more extensive informa- tion required for technological applications (e.g., tabulated numerical data) in a timely manner. DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or retpoosi- bility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Refer- ence herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recom- mendation, or favoring by the United States Government or any agency thereof.
    [Show full text]
  • Uses of Isotopic Neutron Sources in Elemental Analysis Applications
    EG0600081 3rd Conference on Nuclear & Particle Physics (NUPPAC 01) 20 - 24 Oct., 2001 Cairo, Egypt USES OF ISOTOPIC NEUTRON SOURCES IN ELEMENTAL ANALYSIS APPLICATIONS A. M. Hassan Department of Reactor Physics Reactors Division, Nuclear Research Centre, Atomic Energy Authority. Cairo-Egypt. ABSTRACT The extensive development and applications on the uses of isotopic neutron in the field of elemental analysis of complex samples are largely occurred within the past 30 years. Such sources are used extensively to measure instantaneously, simultaneously and nondestruclively, the major, minor and trace elements in different materials. The low residual activity, bulk sample analysis and high accuracy for short lived elements are improved. Also, the portable isotopic neutron sources, offer a wide range of industrial and field applications. In this talk, a review on the theoretical basis and design considerations of different facilities using several isotopic neutron sources for elemental analysis of different materials is given. INTRODUCTION In principle there are two ways to use neutrons for elemental and isotopic abundance analysis in samples. One is the neutron activation analysis which we call it the "off-line" where the neutron - induced radioactivity is observed after the end of irradiation. The other one we call it the "on-line" where the capture gamma-rays is observed during the neutron bombardment. Actually, the sequence of events occurring during the most common type of nuclear reaction used in this analysis namely the neutron capture or (n, gamma) reaction, is well known for the people working in this field. The neutron interacts with the target nucleus via a non-elastic collision, a compound nucleus forms in an excited state.
    [Show full text]
  • PGNAA Neutron Source Moderation Setup Optimization
    Submitted to ‘Chinese Physics C PGNAA neutron source moderation setup optimization Zhang Jinzhao1（张金钊）Tuo Xianguo1（庹先国） (1.Chengdu University of Technology Applied Nuclear Techniques in Geoscience Key Laboratory of Sichuan Province，Chengdu 610059，China) Abstract: Monte Carlo simulations were carried out to design a prompt γ-ray neutron activation analysis (PGNAA) thermal neutron output setup using MCNP5 computer code. In these simulations the moderator materials, reflective materials and structure of the PGNAA 252Cf neutrons of thermal neutron output setup were optimized. Results of the calcuations revealed that the thin layer paraffin and the thick layer of heavy water moderated effect is best for 252Cf neutrons spectrum. The new design compared with the conventional neutron source design, the thermal neutron flux and rate were increased by 3.02 times and 3.27 times. Results indicate that the use of this design should increase the neutron flux of prompt gamma-ray neutron activation analysis significantly. Key word: PGNAA; neutron source; thermal neutron; moderation; reflection 1. Introduction study, Monte Carlo calculation was carried out for the Prompt gamma ray neutron activation analysis design of a 252Cf neutron source moderation setup for the (PGNAA) is a rapid, nondestructive, powerful analysis cement samples[7]. The model of Monte Carlo multielemental analysis technique, large samples of some simulation was verified by experiment[8, 9].We improve minor, trace light elements and is used in industrial the thermal neutron source yield rate of 252Cf neutron by control[1-5]. In a PGNAA analysis, the sample nuclear the PGNAA neutron source structure to the design. The composition is determined from prompt gamma rays calculation results for the new design were compared which produced through neutron inelastic scattering and with the previous, example: themal neutron flux rate, fast thermal neutron capture.
    [Show full text]
  • Arxiv:1506.05417V2 [Physics.Ins-Det] 28 Jul 2016
    http://dx.doi.org/10.1016/j.apradiso.2016.06.032 A precise method to determine the activity of a weak neutron source using a germanium detector M. J. M. Dukea, A. L. Hallinb, C. B. Kraussb, P. Mekarskib,∗, L. Sibleyb aSLOWPOKE Nuclear Reactor Facility, University of Alberta, Edmonton, AB T6G 2G7, Canada bDepartment of Physics, University of Alberta, Edmonton, AB T6G 2E1, Canada Abstract A standard high purity germanium (HPGe) detector was used to determine the previously unknown neutron activity of a weak americium-beryllium (AmBe) neutron source. γ rays were created through 27Al(n,n0), 27Al(n,γ) and 1H(n,γ) reactions induced by the neutrons on aluminum and acrylic disks, respectively. These γ rays were measured using the HPGe detector. Given the unorthodox experimental arrangement, a Monte Carlo simulation was developed to model the efficiency of the detector system to determine the neutron activity from the measured γ rays. The activity of our neutron source was determined to be 307.4 ± 5.0 n/s and is consistent for the different neutron-induced γ rays. Keywords: neutron activation, germanium detector, simulation, spectroscopy, activity determination 1. Introduction As neutrons are difficult to detect, determining the absolute activity of a neutron source is challenging. This difficulty increases as the activity of the source decreases. Sophisticated techniques exist for neutron activity measure- ments, including the manganese bath technique[1], proton recoil techniques[2] and the use of 3He proportional counters[3]; nevertheless, the development of a method utilizing commonly available high purity germanium (HPGe) detectors would be advantageous. HPGe's are an industry standard for measuring γ ray energies to high preci- sion.
    [Show full text]
  • Neutron Sources
    Neutron Sources Nadia Fomin Fundamental Neutron Physics Summer School Knoxville, TN 2015 Much content “borrowed” from Kevin Anderson, Mike Snow, Geoff 1 Greene, Scott Dewey, Mike Moncko, Jack Carpenter, and many others http://knoxbeerweek.com/ Neutron Sources Nadia Fomin Fundamental Neutron Physics Summer School Knoxville, TN 2015 Much content “borrowed” from Kevin Anderson, Mike Snow, Geoff 3 Greene, Scott Dewey, Mike Moncko, Jack Carpenter, and many others What is neutron physics ? Research which uses “low energy” neutrons from nuclear reactors and accelerator-driven spallation sources to address questions in nuclear, particle, and astrophysics Neutron Properties -22 Electric charge: qn=0, electrically neutral [qn<10 e] -5 -25 2 Size: rn~10 Angstrom=1 Fermi [area~ 10 cm =0.1 “barn”] Internal Structure: quarks [ddu, md~ mu~few MeV ] + gluons Spin: sn= 1/2 [Fermi statistics] Magnetic Dipole Moment: mn/ mp = -0.68497935(17) -26 Electric Dipole Moment: zero[dn < 10 e-cm] Mass: mn=939.566 MeV [mn> mp+ me, neutrons can decay] Lifetime: tn=880ish (depends on whom you ask) Neutrons are hard to get Neutrons are bound in nuclei, need several MeV for liberation E E=0 We want E~kT~25 meV (room temperature) VNN How to slow down a heavy neutral particle with Mn= Mp ? Lots of collisions… p n [1/2]N=(1 MeV)/(25 meV) for N collisions E 0 E/2 Neutrons are unstable when free->they can’t be accumulated easily Neutrons: Fast and Furious. And slow and gentle . Thermal ~25meV (2200m/s, λT=1.8Å) . Cold 50μeV-25meV . Very cold 2x10-7 - 5x10-5 eV .
    [Show full text]
  • Chapter 3 Gamma-Ray and Neutron Sources R.J. Holmes
    123 CHAPTER 3 GAMMA-RAY AND NEUTRON SOURCES R.J. HOLMES 125 1. GAMMA-RAY SOURCES Most y-ray sources in commercial use do not occur in nature because their half-lives are small compared with geological times. They must be produced from naturally occurring nuclides by a suitable nucle?r reaction; often this is by irradiation in a nuclear reactor. Some examples of radioisotope production are given below: 59Co (n,y)60Co T^ 5.26 y 123Sb (n,y)mSb T^ 60 d 6Li (n,a)3H T^ 12.3 y 55Mn (p,n)55Fe T, 2.7 y Commercially available sources are sealed in chemically inert capsules. The choice of the most suitable source for a particular application usually depends on the energy of the y-rays that are emitted and on the half-life of the radioisotope. In many applications, a monoenergetic source of long half-life is preferred. Calibration corrections for source decay can be made using the familiar equation - 0.693t/T, = Io e where I is the initial source intensity/ I(t) is its intensity at time o t, and T, is the half-life. Selection of the appropriate y-ray energy depends on such criteria as the energy threshold for a desired nuclear reaction and whether absorption should be due predominantly to the photoelectric effect or Compton scattering. Table 1 lists the commonly used y-ray sources together with their y-ray energies and half-lives. 2. X-RAY SOURCES Sources of radiation below an energy of about 150 keV are usually referred to as X-ray sources, although technically some of them are low energy y-ray sources, e.g.
    [Show full text]
  • AN34 Application Note Experiment 17 Neutron Activation Analysis
    ® ORTEC AN34 Experiment 17 Neutron Activation Analysis (Slow Neutrons) Equipment Needed from ORTEC colorimetric, spectrographic, or mass spectroscopy, its sensitivity is usually shown to be better by a factor of 10 than that of other • 113 Scintillation Preamplifier methods. Activation analysis is used extensively in such fields as • 266 Photomultiplier Tube Base geology, medicine, agriculture, electronics, metallurgy, • 4006 or 4001A/4002D Bin and Power Supply criminology, and the petroleum industry. • 556 High Voltage Power Supply • 575A Amplifier The Neutron Source • 905-3 2-in. x 2-in. or 905-4 3-in. x 3-in. NaI(Tl) Detector and PM This experiment is described using 1 Ci of Am-Be for the Tube neutron source, with the source located in the center of a • Easy-MCA 2k System including a USB cable, a suitable PC paraffin howitzer. The samples are irradiated at a point ~4 cm and MAESTRO-32 software (other ORTEC MCAs may be from the source by the neutrons whose energies have been substituted) moderated by the paraffin between that point and the source. • Coaxial Cables and Adapters: Any of the commonly found isotopic neutron sources can be • One C-24-1/2 RG-62A/U 93-Ω coaxial cable with BNC plugs used for this experiment. on both ends, 15-cm (1/2-ft) length. Neutron Activation Equations Ω • One C-24-12 RG-62A/U 93- coaxial cable with BNC plugs Assume that the sample has been activated in the howitzer. At on both ends, 3.7-m (12-ft) length. the instant when the activation has been terminated, (tc = 0), the • Two C-24-4 RG-62A/U 93-Ω coaxial cables with BNC plugs activity of the sample is given by the following expression: on both ends, 1.2-m (4-ft) length.
    [Show full text]
  • 1 Spallation Neutron Source and Other High Intensity
    SPALLATION NEUTRON SOURCE AND OTHER HIGH INTENSITY PROTON SOURCES* WEIREN CHOU Fermi National Accelerator Laboratory P.O. Box 500 Batavia, IL 60510, USA E-mail: [email protected] This lecture is an introduction to the design of a spallation neutron source and other high intensity proton sources. It discusses two different approaches: linac-based and synchrotron-based. The requirements and design concepts of each approach are presented. The advantages and disadvantages are compared. A brief review of existing machines and those under construction and proposed is also given. An R&D program is included in an appendix. 1. Introduction 1.1. What is a Spallation Neutron Source? A spallation neutron source is an accelerator-based facility that produces pulsed neutron beams by bombarding a target with intense proton beams. Intense neutrons can also be obtained from nuclear reactors. However, the international nuclear non-proliferation treaty prohibits civilian use of highly enriched uranium U235. It is a showstopper of any high efficiency reactor-based new neutron sources, which would require the use of 93% U235. (This explains why the original proposal of a reactor-based Advanced Neutron Source at the Oak Ridge National Laboratory in the U.S. was rejected. It was replaced by the accelerator-based Spallation Neutron Source, or SNS, project.) A reactor-based neutron source produces steady higher flux neutron beams, whereas an accelerator-based one produces pulsed lower flux neutron beams. So the trade-off is high flux vs. time structure of the neutron beams. This course will teach accelerator-based neutron sources. An accelerator-based neutron source consists of five parts: 1) Accelerators 2) Targets 3) Beam lines * This work is supported by the Universities Research Association, Inc., under contract No.
    [Show full text]
  • 28 Neutron Activation Analysis (NAA) Predicting the Sensitivity of Neutron Activation Analysis (NAA)
    Neutron Activation and Activation Analysis 11/26/09 1 General 2 General Many nuclear reactions produce radioactive products. The most common of these reactions involve neutrons: Neutron + Target Nuclide → Activation Product 3 General Important Applications/Issues Associated with Neutron Activation 1. Neutron Activation Analysis (NAA) This is an extraordinarily powerful technique for identifying and quantifying various elements (and nuclides) in a sample. 2. Neutron Fluence Rate (Flux) Measurements Neutron fluence rates in reactors or other neutron sources can be measured by exposing targets (e.g., metal foils) to the neutrons and measuring the induced activity. 4 General Important Applications/Issues Associated with Neutron Activation 3. Dosimetry Following Criticality Accidents The induced activity in objects or individuals following a criticality accident can be used to estimate the doses to these individuals. 4. Hazards from Induced Activity Induced radioactivity in the vicinity of intense neutron sources can constitute an exposure hazard. Examples of such sources include reactors, accelerators and, of course, nuclear explosions. 5 General Neutron Capture The most important reaction is neutron capture: Thermal neutrons are most likely to be captured. The target nuclide is usually, but not necessarily stable. If the product is radioactive, it is likely a beta emitter. The gamma ray, referred to as a prompt gamma or capture gamma, is typically of high energy. 6 General Neutron Capture Example: This is an exception to the generalization that the activation product is a beta emitter. Cr-51 decayyys by electron cap ture! The major prompt gamma rays: 749 keV produced 11.0% of the time 8512.1 keV produced 6.16% of the time 8484.0 keV produced 4.54% of the time 7 General Neutron-Proton Reaction Another potentially important reaction is the n-p reaction: The n-p reaction is most likely for fast neutrons and target nuclides with low atomic numbers.
    [Show full text]
  • Protection Against Neutron Radiation up to 30 Million Electron Volts
    PROTECTION AGAINST NEUTRON RADIATION UP TO 30 MILLION ELECTRON VOLTS Handbook 63 U. S. Department of Commerce National Bureau of Standards HANDBOOKS OF THE NATIONAL BUREAU OF STANDARDS The following Handbooks issued by the Bureau are avail¬ able by purchase from the Superintendent of Documents, Government Printing Office, Washington 25, D. C., at the prices indicated: No. Price 28 Screw-Thread Standards for Federal Services 1944-$1.25 28 1950 Supplement to Screw-Thread Standards for Federal Services 1944 .60 28 Screw-Thread Standards for Federal Services 1957, Part I. (Amends in part H28 1944 and in part its 1950 Supplement) . 1.25 30 National Electrical Safety Code. 2.25 37 Testing of Weighing Equipment. 2.50 42 Safe Handling of Radioactive Isotopes.20 43 Installation and Maintenance of Electric Supply and Communication Lines. Safety Rules and Discussion.. 2.25 44 Specifications, Tolerances, and Regulations for Commer¬ cial Weighing and Measuring Devices—2d Edition.... 2.00 45 Testing of Measuring Equipment . 1.50 46 Code for Protection Against Lightning.45 48 Control and Removal of Radioactive Contamination in Laboratories .15 49 Recommendations for Waste Disposal of Phosphorus-32 and Iodine-131 for Medical Users.15 50 X-ray Protection Design.20 51 Radiological Monitoring Methods and Instruments.20 52 Maximum Permissible Amounts of Radioisotopes in the Human Body and Maximum Permissible Concentra¬ tions in Air and Water.25 53 Recommendations for the Disposal of Carbon-14 Wastes .15 54 Protection Against Radiations From Radium, Cobalt-60,
    [Show full text]
  • Moderator Design for Accelerator Based Neutron Radiography and Tomography Systems
    Moderator Design For Accelerator Based Neutron Radiography and Tomography Systems by Donald B. Puffer Submitted to the Department of Nuclear Engineering in partial ful- fillment of the requirements for the degree of Master of Science in Nuclear Engineering at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY August 1994 © Massachusetts Institute of Technology, 1994. All Rights Reserved. A uthor ..................................... .................... .................................................. Department of Nuclear Engineering August 19, 1994 Certified by •., - 7/7' ....... " PiiaRsr Sciei < o Dr. Richard Lanza SPrincipal Research Scie Department of Nuclear Engineering Thesis Supervisor R ead by .... ...... .... .......... .... .................................................................. Dr. Jacquelyn Yanch / Professor of Nuclear Engineering Thesis Reader A ccepted by ............................... ........... ..... ............................................... Dr. Allen Henry rs., -Chairman, Committee on Graduate Students Department of Nuclear Engineering o V 16 1994 Moderator Design For Accelerator Based Neutron Radiography and Tomography Systems by Donald B. Puffer Submitted to the Department of Nuclear Engineering on August 19, 1994, in partial fulfillment of the requirements for the degree of Master of Science in Nuclear Engineering Abstract MIT is in the initial phase of developing a small accelerator based neutron imaging system. The system includes a radiofrequency quadrupole (RFQ) accelerator--producing neutrons by the
    [Show full text]
  • The Bimodal Neutron and X-Ray Imaging Driven by a Single Electron Linear Accelerator
    applied sciences Article The Bimodal Neutron and X-ray Imaging Driven by a Single Electron Linear Accelerator Yangyi Yu 1,2, Ruiqin Zhang 1,2, Lu Lu 1,2 and Yigang Yang 1,2,* 1 Department of Engineering Physics, Tsinghua University, Beijing 100084, China; [email protected] (Y.Y.); [email protected] (R.Z.); [email protected] (L.L.) 2 Key Laboratory of Particle & Radiation Imaging, Tsinghua University, Ministry of Education, Beijing 100084, China * Correspondence: [email protected] Abstract: Both X-ray imaging and neutron imaging are essential methods in non-destructive testing. In this work, a bimodal imaging method combining neutron and X-ray imaging is introduced. The experiment is based on a small electron accelerator-based photoneutron source that can simultane- ously generate the following two kinds of radiations: X-ray and neutron. This identification method utilizes the attenuation difference of the two rays’ incidence on the same material to determine the material’s properties based on dual-imaging fusion. It can enhance the identification of the materials from single ray imaging and has the potential for widespread use in on-site, non-destructive testing where metallic materials and non-metallic materials are mixed. Keywords: bimodal imaging; compact neutron source; neutron imaging; X-ray imaging; image fusion Citation: Yu, Y.; Zhang, R.; Lu, L.; 1. Introduction Yang, Y. The Bimodal Neutron and Both X-ray imaging and neutron imaging have proven capabilities in non-destructive X-ray Imaging Driven by a Single assays (NDAs) [1]. Unlike the cross sections of photons sensitive to the atomic number, Electron Linear Accelerator.
    [Show full text]