DOCSLIB.ORG

Neutron Interactions and Dosimetry Outline Introduction Tissue

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Neutron Interactions and Dosimetry Outline Introduction Tissue Outline • Neutron dosimetry Neutron Interactions and – Thermal neutrons Dosimetry – Intermediate-energy neutrons – Fast neutrons Chapter 16 • Sources of neutrons • Mixed field dosimetry, paired dosimeters F.A. Attix, Introduction to Radiological • Rem meters Physics and Radiation Dosimetry Introduction Tissue composition • Consider neutron interactions with the majority tissue elements H, O, C, and N, and the resulting absorbed dose • Because of the short ranges of the secondary charged particles that are produced in such interactions, CPE is usually well approximated • Since no bremsstrahlung x-rays are generated, the • The ICRU composition for muscle has been assumed in absorbed dose can be assumed to be equal to the most cases for neutron-dose calculations, lumping the kerma at any point in neutron fields at least up to 1.1% of “other” minor elements together with oxygen to an energy E ~ 20 MeV make a simple four-element (H, O, C, N) composition Neutron kinetic energy Neutron kinetic energy • Neutron fields are divided into three • Thermal neutrons, by definition, have the most probable categories based on their kinetic energy: kinetic energy E=kT=0.025eV at T=20C – Thermal (E<0.5 eV) • Neutrons up to 0.5eV are considered “thermal” due to simplicity of experimental test after they emerge from – Intermediate-energy (0.5 eV<E<10 keV) moderator material – Fast (E>10 keV) • Cadmium ratio test: • Differ by their primary interactions in tissue – Gold foil can be activated through 197Au(n,)198Au interaction and resulting biological effects – Addition of 1mm thick Cd filter, which absorbs all neutrons below 0.5eV, tests for presence of those neutrons 1 Neutron kinetic energy Kerma calculations • For E<10 keV the dose is mainly due to - • For a mono-energetic neutron beam having rays resulting from thermal-neutron capture fluence (cm-2), the kerma that results from a in hydrogen, 1H(n,)2H neutron at a point in a medium is 8 1 • For E>10 keV the dose is dominated by the K 1.60210 Nt m Etr contribution of recoil protons resulting from where is the interaction cross section in elastic scattering of hydrogen nuclei 2 cm /(target atom), Nt is the number of target atoms – Resulting biological effect (and the in the irradiated sample, m is the sample mass in corresponding neutron quality factor) rises grams, and Etr is the total kinetic energy (MeV) steeply given to charged particles per interaction Kerma calculations Kerma calculations -8 -1 • The product of (1.602 10 Ntm Etr) is • Fn values are tabulated in Appendix F 2 equal to the kerma factor Fn in rad cm /n • Fn is not generally a smooth function of Z and E, • Thus the equation reduces to unlike the case of photon interaction coefficients • Interpolation vs. Z cannot be employed to obtain CPE values of Fn for elements for which data are not D K Fn listed, and interpolation vs. E is feasible only • CPE condition is usually well-approximated within energy regions where resonance peaks are for neutron interactions in tissue absent Typical neutron absorption Kerma calculations cross section Resonance peaks occur when the binding energy of a neutron plus the KE of the neutron are exactly equal to the amount required to raise a compound nucleus from its ground state to one of quantum levels Image from Kerma per unit fluence due to various interaction in a small mass of tissue http://nuclearpowertraining.tpub.com/h1019v1/css/h1019v1_113.htm 2 Thermal-neutron interactions Thermal-neutron interactions in tissue in tissue • Two important interactions of thermal • The nitrogen interaction releases a kinetic energy of neutrons with tissue: Etr = 0.62 MeV that is shared by the proton (0.58 MeV) and the recoiling nucleus (0.04 MeV) – neutron capture by nitrogen, 14N(n,p)14C • CPE exits since the range of protons in tissue ~10mm – neutron capture by hydrogen, 1H(n,)2H • Based on known values for and N /m, kerma factor • Thermal neutrons have a larger probability t F 2.741011 [rad cm 2 / n] of capture by hydrogen atoms in muscle, n because there are 41 times more H atoms • Dose deposited CPE than N atoms in tissue D 2.741011 [rad] Thermal-neutron interactions Thermal-neutron interactions in tissue in tissue • In the hydrogen interaction the energy given to - • In the center of a 1-cm diameter sphere of tissue the rays per unit mass and per unit fluence of thermal kerma contributions from the (n, p) and (n, ) neutrons can be obtained similarly, but replacing processes are comparable in size • In a large tissue mass (radius > 5 times the -ray Etr by E = 2.2 MeV (the -ray energy released in each neutron capture) MFP) where radiation equilibrium is approximated, the kerma due indirectly to the (n, ) process is 26 R m 7.131010 [rad cm 2 / n] • The energy available: times that of the nitrogen (n, p) interaction • These -rays must interact and transfer their • The human body is intermediate in size, but large energy to charged particles to produce kerma enough so the 1H(n, )2H process dominates in • Contribution to dose depends on proximity to RE kerma (and dose) production Interactions by intermediate Interactions by neutrons in tissue and fast neutrons in tissue • It is dominated below 10-4 MeV (100eV) by (n,p) reactions, mostly in nitrogen, represented by curve g • Above 10-4 MeV elastic scattering of hydrogen nuclei (curve b) contributes nearly all of the kerma x10-3 3 Interaction by intermediate Interaction by intermediate and fast neutrons in tissue and fast neutrons in tissue • The average energy transferred by elastic • Values for E for different tissue atoms: scattering to a nucleus is closely approximated tr (i.e., assuming isotropic scattering in the center- – E/2 for hydrogen recoils (changes from 0 when o of-mass system) by proton is recoiling at 90 to Etr for protons recoiling straight ahead) 2M M a n – 0.142E for C atoms Etr E 2 M a M n – 0.124E for N where E = neutron energy, – 0.083E for O Ma = mass of target nucleus, Mn = neutron mass Neutron sources Neutron sources • Neutrons can be released through processes such as fission, spallation, or neutron stripping • Most widely available neutron sources: • Fission: splitting atoms in a nuclear reactor – Nuclear fission reactors – n + 235U = n + n + fragments – one n may go back – Accelerators into chain reaction, the other is available – Radioactive sources • Spallation: bombarding heavy metal atoms with energetic protons – p + heavy nucleus = X * n + fragments • Stripping: bombarding light metal atoms with protons, a-particles, etc. Neutron sources Neutron sources • Fission-like spectra have average neutron energies ~2MeV • From beam ports of nuclear reactors • Watt spectrum is an idealized shape for unmoderated reactor neutrons • Several types of Be(a,n) radioactive sources are in common use, employing 210Po, 239Pu, 241Am, or 226Ra as the emitter • Neutron yields are on the order of 1 neutron per 104 a- Fission neutron spectra from reactors particles; average energies 4 MeV 4 Neutron sources Neutron Quality Factor deuteron bombardment of Be target • Cyclotrons are used to produce neutron beams by accelerating protons or deuterons into various targets, most commonly Be • For purposes of neutron radiation protection the dose equivalent H = DQ, • The neutron spectrum extends from 0 to energies Emax somewhat above the where Q is the quality factor, which depends on neutron energy deuteron energy, and have E ~0.4E avg max • The quality factor for all -rays is taken to be unity for purposes of • Tissue dose rates ~10rad/min at 1m in tissue, -ray background ~few % combining neutron and -ray dose equivalents Radiation Weighting Factor Mixed-Field Dosimetry n + • New approach uses radiation and tissue weighting factors • Neutrons and -rays are both indirectly ionizing (updated in ICRP 103 report, 2007); effective dose radiations that are attenuated exponentially in E=w H = w w *D T T T R T,R passing through matter • For neutrons weighting factor is a continuous function of energy; represented as a graph or in functional form • Each is capable of generating secondary fields of the other radiation: – (, n) reactions are only significant for high-energy - rays (10 MeV, there is a threshold defined by reaction) – (n, ) reactions can proceed at all neutron energies and are especially important in thermal-neutron capture, as discussed for 1H(n, )2H Mixed-Field Dosimetry n + Mixed-Field Dosimetry n + • Neutron fields are normally “contaminated” by • Three general categories of dosimeters for secondary -rays n + applications: • Since neutrons generally have more biological 1. Neutron dosimeters that are relatively effectiveness per unit of absorbed dose than - insensitive to rays rays, it is desirable to account for and n 2. -ray dosimeters that are relatively insensitive components separately to neutrons • It is especially important in the case of neutron 3. Dosimeters that are comparably sensitive to dosimeters to specify the reference material to both radiations which the dose reading is supposed to refer 5 Mixed-Field Dosimetry n + Mixed-Field Dosimetry n + • While water is a very close substitute of muscle • The response of a dosimeter to a mixed field of neutrons and -rays tissue in photon dosimetry, it is not as close a Q AD BD substitute for neutrons n, n • Water is 1/9 hydrogen by weight; muscle is 1/10 or alternatively as hydrogen Q B n, D D • Water contains no nitrogen, and hence can have no A A n 14N(n,p)14C reactions by thermal neutrons Here A = response per unit of absorbed dose in tissue for - rays, B = response
Load more

Recommended publications
  • Neutron Activation and Prompt Gamma Intensity in Ar/CO $ {2} $-Filled Neutron Detectors at the European Spallation Source
    Neutron activation and prompt gamma intensity in Ar/CO2-filled neutron detectors at the European Spallation Source E. Diana,b,c,∗, K. Kanakib, R. J. Hall-Wiltonb,d, P. Zagyvaia,c, Sz. Czifrusc aHungarian Academy of Sciences, Centre for Energy Research, 1525 Budapest 114., P.O. Box 49., Hungary bEuropean Spallation Source ESS ERIC, P.O Box 176, SE-221 00 Lund, Sweden cBudapest University of Technology and Economics, Institute of Nuclear Techniques, 1111 Budapest, M}uegyetem rakpart 9. dMid-Sweden University, SE-851 70 Sundsvall, Sweden Abstract Monte Carlo simulations using MCNP6.1 were performed to study the effect of neutron activation in Ar/CO2 neutron detector counting gas. A general MCNP model was built and validated with simple analytical calculations. Simulations and calculations agree that only the 40Ar activation can have a considerable effect. It was shown that neither the prompt gamma intensity from the 40Ar neutron capture nor the produced 41Ar activity have an impact in terms of gamma dose rate around the detector and background level. Keywords: ESS, neutron detector, B4C, neutron activation, 41Ar, MCNP, Monte Carlo simulation 1. Introduction Ar/CO2 is a widely applied detector counting gas, with long history in ra- diation detection. Nowadays, the application of Ar/CO2-filled detectors is ex- tended in the field of neutron detection as well. However, the exposure of arXiv:1701.08117v2 [physics.ins-det] 16 Jun 2017 Ar/CO2 counting gas to neutron radiation carries the risk of neutron activa- tion. Therefore, detailed consideration of the effect and amount of neutron ∗Corresponding author Email address: [email protected] (E.
    [Show full text]
  • 7. Gamma and X-Ray Interactions in Matter
    Photon interactions in matter Gamma- and X-Ray • Compton effect • Photoelectric effect Interactions in Matter • Pair production • Rayleigh (coherent) scattering Chapter 7 • Photonuclear interactions F.A. Attix, Introduction to Radiological Kinematics Physics and Radiation Dosimetry Interaction cross sections Energy-transfer cross sections Mass attenuation coefficients 1 2 Compton interaction A.H. Compton • Inelastic photon scattering by an electron • Arthur Holly Compton (September 10, 1892 – March 15, 1962) • Main assumption: the electron struck by the • Received Nobel prize in physics 1927 for incoming photon is unbound and stationary his discovery of the Compton effect – The largest contribution from binding is under • Was a key figure in the Manhattan Project, condition of high Z, low energy and creation of first nuclear reactor, which went critical in December 1942 – Under these conditions photoelectric effect is dominant Born and buried in • Consider two aspects: kinematics and cross Wooster, OH http://en.wikipedia.org/wiki/Arthur_Compton sections http://www.findagrave.com/cgi-bin/fg.cgi?page=gr&GRid=22551 3 4 Compton interaction: Kinematics Compton interaction: Kinematics • An earlier theory of -ray scattering by Thomson, based on observations only at low energies, predicted that the scattered photon should always have the same energy as the incident one, regardless of h or • The failure of the Thomson theory to describe high-energy photon scattering necessitated the • Inelastic collision • After the collision the electron departs
    [Show full text]
  • TUTORIAL on NEUTRON PHYSICS in DOSIMETRY S. Pomp1
    TUTORIAL ON NEUTRON PHYSICS IN DOSIMETRY S. Pomp1,* 1 Department of physics and astronomy, Uppsala University, Box 516, 751 20 Uppsala, Sweden. *Corresponding author. E‐mail address: [email protected] (S.Pomp) Abstract: Almost since the time of the discovery of the neutron more than 70 years ago, efforts have been made to understand the effects of neutron radiation on tissue and, eventually, to use neutrons for cancer treatment. In contrast to charged particle or photon radiations which directly lead to release of electrons, neutrons interact with the nucleus and induce emission of several different types of charged particles such as protons, alpha particles or heavier ions. Therefore, a fundamental understanding of the neutron‐nucleus interaction is necessary for dose calculations and treatment planning with the needed accuracy. We will discuss the concepts of dose and kerma, neutron‐nucleus interactions and have a brief look at nuclear data needs and experimental facilities and set‐ups where such data are measured. Keywords: Neutron physics; nuclear reactions; kerma coefficients; neutron beams; Introduction Dosimetry is concerned with the ability to determine the absorbed dose in matter and tissue resulting from exposure to directly and indirectly ionizing radiation. The absorbed dose is a measure of the energy deposited per unit mass in the medium by ionizing radiation and is measured in Gray, Gy, where 1 Gy = 1 J/kg. Radiobiology then uses information about dose to assess the risks and gains. A risk is increased probability to develop cancer due to exposure to a certain dose. A gain is exposure of a cancer tumour to a certain dose in order to cure it.
    [Show full text]
  • Concrete Analysis by Neutron-Capture Gamma Rays Using Californium 252
    CONCRETE ANALYSIS BY NEUTRON-CAPTURE GAMMA RAYS USING CALIFORNIUM 252 Dick Duffey, College of Engineering, University of Maryland; Peter F. Wiggins, Naval Systems Engineering Department, U.S. Naval Academy; Frank E. Senftle, U.S. Geological Survey; and A. A. El Kady, United Arab Republic Atomic Energy Establishment, Cairo The feasibility of analyzing concrete and cement by a measurement of the neutron-capture or prompt gamma rays was investigated; a 100-ug californium-252 source was used to supply the neutrons. A lithium drifted germanium crystal detected the capture gamma rays emitted. The capture gamma rays from cement, sand, and 3 coarse aggregates-quartzite gravel, limestone, and diabase--:were studied. Concrete blocks made from these materials were then tested. The capture gamma ray response of the calcium, silicon, and iron in the concrete blocks was in accord with the elements identified in the mix materials. The principal spectral lines used were the 6.42 MeV line of calcium, the 4.93 MeV line of silicon, and the doublet of iron at about 7 .64 MeV. The aluminum line at 7. 72 MeV was ob­ served in some cases but at a lower intensity with the limited electronic equipment available. This nuclear spectroscopic technique offers a possi­ ble method of determining the components of sizable concrete samples in a nondestructive, in situ manner. In addition, the neutron-capture gamma ray technique might find application in control of the concrete and cement processes and furnish needed information on production operations and inventories. • FROM THE point of view of the geochemical analyst, concrete may be considered as rock relocated and reformed at the convenience of the engineer.
    [Show full text]
  • Conceptual Design Report Jülich High
    General Allgemeines ual Design Report ual Design Report Concept Jülich High Brilliance Neutron Source Source Jülich High Brilliance Neutron 8 Conceptual Design Report Jülich High Brilliance Neutron Source (HBS) T. Brückel, T. Gutberlet (Eds.) J. Baggemann, S. Böhm, P. Doege, J. Fenske, M. Feygenson, A. Glavic, O. Holderer, S. Jaksch, M. Jentschel, S. Kleefisch, H. Kleines, J. Li, K. Lieutenant,P . Mastinu, E. Mauerhofer, O. Meusel, S. Pasini, H. Podlech, M. Rimmler, U. Rücker, T. Schrader, W. Schweika, M. Strobl, E. Vezhlev, J. Voigt, P. Zakalek, O. Zimmer Allgemeines / General Allgemeines / General Band / Volume 8 Band / Volume 8 ISBN 978-3-95806-501-7 ISBN 978-3-95806-501-7 T. Brückel, T. Gutberlet (Eds.) Gutberlet T. Brückel, T. Jülich High Brilliance Neutron Source (HBS) 1 100 mA proton ion source 2 70 MeV linear accelerator 5 3 Proton beam multiplexer system 5 4 Individual neutron target stations 4 5 Various instruments in the experimental halls 3 5 4 2 1 5 5 5 5 4 3 5 4 5 5 Schriften des Forschungszentrums Jülich Reihe Allgemeines / General Band / Volume 8 CONTENT I. Executive summary 7 II. Foreword 11 III. Rationale 13 1. Neutron provision 13 1.1 Reactor based fission neutron sources 14 1.2 Spallation neutron sources 15 1.3 Accelerator driven neutron sources 15 2. Neutron landscape 16 3. Baseline design 18 3.1 Comparison to existing sources 19 IV. Science case 21 1. Chemistry 24 2. Geoscience 25 3. Environment 26 4. Engineering 27 5. Information and quantum technologies 28 6. Nanotechnology 29 7. Energy technology 30 8.
    [Show full text]
  • Meeting the Joint Commission's Fluoroscopy Training Requirements
    Meeting The Joint Commission’s Outline Fluoroscopy Training Requirements • Overview of TJC’s recent fluoroscopy requirements Part I: Image Gently, Image Wisely and Dose Optimization • Basics of radiation units, terminology and regulatory limits • Radiation risks in fluoroscopy, their prevalence and probabilities • Physical and operational aspects of fluoroscopes Satish Nair Ph.D, CHP, DABMP Certified Health Physicist • Best practices in fluoroscopy: for patients and operators Certified Medical Physicist F. X. Massé Associates, Inc. Health and Medical Physics Consultants Gloucester, MA fxmasse.com 20th Annual SRPE Educational Conference, Las Vegas, NV April 2019 1 January 2019 Terminology Convert to Equivalent dose (mrem, mSv) X-ray , Gamma, Beta = 1 Alpha = 20 Proton = 2 Head CT Neutron = 5 to 20 Cardiac Exposure Stress Test KUB Image Gently: ‘Pause and Pulse’ resources X Ray 1 January 2019 • Annual Medical Physics evaluation of fluoroscopes • Designated Radiation Safety Officer (RSO) Measure Exposure Extremity X Ray • Dose indices stored in retrievable format: CAK or KAP - if displayed Roentgen Compare to NB Convert to R, mR, mR/h If not displayed: cumulative fluoro time and # of digital spot images Calculate Radiation Effective Dose (Whole Body Dose) • Establish radiation exposure and skin dose thresholds for adverse effects Absorbed dose to organ • Perform evaluation if exceeded these thresholds are exceeded Roentgen equivalent man Roentgen absorbed dose rem, mrem, mrem/year rad, mrad 1 July 2018 Sievert: Sv, mSv • Use of shielding
    [Show full text]
  • 1663-29-Othernuclearreaction.Pdf
    it’s not fission or fusion. It’s not alpha, beta, or gamma dosimeter around his neck to track his exposure to radiation decay, nor any other nuclear reaction normally discussed in in the lab. And when he’s not in the lab, he can keep tabs on his an introductory physics textbook. Yet it is responsible for various experiments simultaneously from his office computer the existence of more than two thirds of the elements on the with not one or two but five widescreen monitors—displaying periodic table and is virtually ubiquitous anywhere nuclear graphs and computer codes without a single pixel of unused reactions are taking place—in nuclear reactors, nuclear bombs, space. Data printouts pinned to the wall on the left side of the stellar cores, and supernova explosions. office and techno-scribble densely covering the whiteboard It’s neutron capture, in which a neutron merges with an on the right side testify to a man on a mission: developing, or atomic nucleus. And at first blush, it may even sound deserving at least contributing to, a detailed understanding of complex of its relative obscurity, since neutrons are electrically neutral. atomic nuclei. For that, he’ll need to collect and tabulate a lot For example, add a neutron to carbon’s most common isotope, of cold, hard data. carbon-12, and you just get carbon-13. It’s slightly heavier than Mosby’s primary experimental apparatus for doing this carbon-12, but in terms of how it looks and behaves, the two is the Detector for Advanced Neutron Capture Experiments are essentially identical.
    [Show full text]
  • Chapter 3. Fundamentals of Dosimetry
    Chapter 3. Fundamentals of Dosimetry Slide series of 44 slides based on the Chapter authored by E. Yoshimura of the IAEA publication (ISBN 978-92-0-131010-1): Diagnostic Radiology Physics: A Handbook for Teachers and Students Objective: To familiarize students with quantities and units used for describing the interaction of ionizing radiation with matter Slide set prepared by E.Okuno (S. Paulo, Brazil, Institute of Physics of S. Paulo University) IAEA International Atomic Energy Agency Chapter 3. TABLE OF CONTENTS 3.1. Introduction 3.2. Quantities and units used for describing the interaction of ionizing radiation with matter 3.3. Charged particle equilibrium in dosimetry 3.4. Cavity theory 3.5. Practical dosimetry with ion chambers IAEA Diagnostic Radiology Physics: a Handbook for Teachers and Students – chapter 3, 2 3.1. INTRODUCTION Subject of dosimetry : determination of the energy imparted by radiation to matter. This energy is responsible for the effects that radiation causes in matter, for instance: • a rise in temperature • chemical or physical changes in the material properties • biological modifications Several of the changes produced in matter by radiation are proportional to absorbed dose , giving rise to the possibility of using the material as the sensitive part of a dosimeter There are simple relations between dosimetric and field description quantities IAEA Diagnostic Radiology Physics: a Handbook for Teachers and Students – chapter 3, 3 3.2. QUANTITIES AND UNITS USED FOR DESCRIBING THE INTERACTION OF IONIZING RADIATION
    [Show full text]
  • Basic Radiation Interactions, Definition of Dosimetric Quantities, and Data Sources
    Basic Radiation Interactions, Definition of Dosimetric Quantities, and Data Sources J.V. Siebers Virginia Commonwealth University Richmond, Virginia USA 2009 AAPM Summer School Learninggj Objectives 1. To review and describ e the bas ics of radiation interactions for understanding radiation dosimetry 2. To review definitions of quantities required for understanding radiation dosimetry ©JVS: 2009 AAPM SS Constants Units Conversions ©JVS: 2009 AAPM SS ©JVS: 2009 AAPM SS Scope Radiation Types Ionizing Interactions can remove atomic orbital electrons Non-Ionizing Particulate Electromagnetic -electron -positron -proton -neutron -alpha -etc. ©JVS: 2009 AAPM SS Types of ionizin g radiation Direc tltly ion iz ing radia tion Direct interactions via the Coulomb force along a particles track Charged particles electrons positrons protons heavy charged particles ©JVS: 2009 AAPM SS Direct Ionization Coulombic Interaction e- A charged particle exerts electromagnetic forces on atomic Energy transfer can electrons result in the ejection of an electron (ionization) ©JVS: 2009 AAPM SS Indirectlyyg Ionizing Radiation Uncharged particles that must first transfer energy to a charged particle which can then further ionize matter Two step process Examples Elec tromagne tic radia tions: x- or γ-rays Neutrons ©JVS: 2009 AAPM SS Indirectly Ionizing Radiation Pho toe lec tr ic Effec t e- Ejec te d h electrons further ionize matter ©JVS: 2009 AAPM SS Radiant Energy R R – Total energy, excluding rest mass, carried by particles Photons: E = hν = hc/λ
    [Show full text]
  • Sonie Applications of Fast Neutron Activation Analysis of Oxygen
    S E03000182 CTH-RF- 16-5 Sonie Applications of Fast Neutron Activation Analysis of Oxygen Farshid Owrang )52 Akadenmisk uppsats roir avliiggande~ av ilosofie ficentiatexamen i Reaktorf'ysik vid Chalmer's tekniska hiigskola Examinator: Prof. Imre PiAst Handledare: Dr. Anders Nordlund Granskare: Bitr. prof. G~iran Nyrnan Department of Reactor Physics Chalmers University of Technology G6teborg 2003 ISSN 0281-9775 SOME APPLICATIONS OF FAST NEUTRON ACTIVATION OF OXYGE~'N F~arshid Owrang Chalmers University of Technology Departmlent of Reactor Physics SEP-1-412 96 G~iteborg ABSTRACT In this thesis we focus on applications of neutron activation of oxygen for several purposes: A) measuring the water level in a laboratory tank, B) measuring the water flow in a pipe system set-up, C) analysing the oxygen in combustion products formed in a modern gasoline S engine, and D) measuring on-line the amount of oxygen in bulk liquids. A) Water level measurements. The purpose of this work was to perform radiation based water level measurements, aimed at nuclear reactor vessels, on a laboratory scale. A laboratory water tank was irradiated by fast neutrons from a neutron enerator. The water was activated at different water levels and the water level was decreased. The produced gamma radiation was measured using two detectors at different heights. The results showed that the method is suitable for measurement of water level and that a relatively small experimental set-up can be used for developing methods for water level measurements in real boiling water reactors based on activated oxygen in the water. B) Water flows in pipe.
    [Show full text]
  • STUDY of the NEUTRON and PROTON CAPTURE REACTIONS 10,11B(N, ), 11B(P, ), 14C(P, ), and 15N(P, ) at THERMAL and ASTROPHYSICAL ENERGIES
    STUDY OF THE NEUTRON AND PROTON CAPTURE REACTIONS 10,11B(n, ), 11B(p, ), 14C(p, ), AND 15N(p, ) AT THERMAL AND ASTROPHYSICAL ENERGIES SERGEY DUBOVICHENKO*,†, ALBERT DZHAZAIROV-KAKHRAMANOV*,† *V. G. Fessenkov Astrophysical Institute “NCSRT” NSA RK, 050020, Observatory 23, Kamenskoe plato, Almaty, Kazakhstan †Institute of Nuclear Physics CAE MINT RK, 050032, str. Ibragimova 1, Almaty, Kazakhstan *[email protected] †[email protected] We have studied the neutron-capture reactions 10,11B(n, ) and the role of the 11B(n, ) reaction in seeding r-process nucleosynthesis. The possibility of the description of the available experimental data for cross sections of the neutron capture reaction on 10B at thermal and astrophysical energies, taking into account the resonance at 475 keV, was considered within the framework of the modified potential cluster model (MPCM) with forbidden states and accounting for the resonance behavior of the scattering phase shifts. In the framework of the same model the possibility of describing the available experimental data for the total cross sections of the neutron radiative capture on 11B at thermal and astrophysical energies were considered with taking into account the 21 and 430 keV resonances. Description of the available experimental data on the total cross sections and astrophysical S-factor of the radiative proton capture on 11B to the ground state of 12C was treated at astrophysical energies. The possibility of description of the experimental data for the astrophysical S-factor of the radiative proton capture on 14C to the ground state of 15N at astrophysical energies, and the radiative proton capture on 15N at the energies from 50 to 1500 keV was considered in the framework of the MPCM with the classification of the orbital states according to Young tableaux.
    [Show full text]
  • Energy Deposition by Neutrons
    22.55 “Principles of Radiation Interactions” Neutrons Classification of neutrons by energy Thermal: E < 1 eV (0.025 eV) Epithermal: 1 eV < E < 10 keV Fast: > 10 keV Neutron sources Neutron energies Reactors neutrons in the few keV to several MeV Fusion reactions 14 MeV Large accelerators Hundreds of MeV Energy Deposition by Neutrons • Neutrons are generated over a wide range of energies by a variety of different processes. • Like photons, neutrons are uncharged and do not interact with orbital electrons. • Neutrons can travel considerable distances through matter without interacting. • Neutrons will interact with atomic nuclei through several mechanisms. o Elastic scatter o Inelastic scatter o Nonelastic scatter o Neutron capture o Spallation • The type of interaction depends on the neutron energy Radiation Interactions: neutrons Page 1 of 8 22.55 “Principles of Radiation Interactions” Cross Sections • Because mass attenuation coefficients, µ/ρ (cm2/g) have dimensions of cm2 in the numerator, they have come to be called “cross sections”. • Cross sections do not represent a physical area, but a probability of an interaction. • Cross sections usually expressed in the unit, barn: (10-24 cm2) • The atomic cross sections can be derived from the mass attenuation coefficient. Photons Cross sections are attenuation coefficients, expressed at the atom level (Probability of interaction per atom) ρ N = atom density (#atoms/cm3) N = N A A A 0 2 σA = atomic cross section (cm /atom) 23 N0 = 6.02 x 10 atoms/mole ρ = g/cm3 µ = N A σ A A = g/mole ρ µ = N σ A 0 A µ N σ ⎛ µ ⎞⎛ A ⎞ 0 A ⎜ ⎟⎜ ⎟ = σ A = ⎜ ⎟⎜ ⎟ ρ A ⎝ ρ ⎠⎝ N 0 ⎠ Radiation Interactions: neutrons Page 2 of 8 22.55 “Principles of Radiation Interactions” Neutron Cross Sections Analogous to photons • Neutrons interact by different mechanisms depending on the neutron energy and the material of the absorber o Scattering • elastic • inelastic o Capture • Each energy loss mechanism has a cross section • Neutron cross sections expressed in barns (1 barn = 10-24 cm2).
    [Show full text]