DOCSLIB.ORG

Natural Uranium and the Environment

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Natural Uranium and the Environment RADIONUCLIDE FACT SHEET Natural Uranium and the environment 238 92U Olivier Seignette/Mikaël Lafontan/IRSN Contents Characteristics 3 Origins 4 Environmental concentrations 4 Metrology, analytical techniques and detection limits 6 Mobility and bioavailability in terrestrial environments 8 Mobility and bioavailability in continental aquatic environments 9 Mobility and bioavailability in marine environments 10 Mobility and bioavailability in semi-natural ecosystems 11 Environmental dosimetry 11 Environmental toxicity 11 Summary 13 Review of measurement methods 14 Usual radioecological parameters: terrestrial environment 14 Usual radioecological parameters: freshwater environment 16 Usual radioecological parameters: marine environment 17 Radiotoxicological parameters 18 Selected bibliography 19 Radionuclide fact sheet NATURAL URANIUM This fact sheet describes the behaviour of the chemical element in the principal compartments of terrestrial and aquatic ecosystems using the following assumptions. Isotope discrimination is negligible, which is verified for most of the elements considered. When the element has stable isotopes, the behavioural analogy between the stable and radioactive isotopes is accepted implicitly, with the understanding that for naturally- occurring elements, the chemical form and emission environment for anthropogenic discharge may involve pathways and transfer processes different from those identified for the stable natural element. The radioactive isotope designated in the title of the fact sheet has major radioecological importance with regard to quantity and persistence in the environment, with other isotopes, both radioactive and stable, being cited as well. The information, which has been intentionally simplified, is intended to reflect the level of knowledge on the topic as of publication and provide values for the main usual radioecological parameters for estimating transfer in the environment and the food chain in particular. Written by: J. Garnier–Laplace, C. Colle and M. Morello Verified by: B. Bonin Date of first issue: 14 May 2001 Revision: Terrestrial ecosystem: L. Février Continental aquatic ecosystem: O. Simon Marine ecosystem: D. Boust and J. Pommier Metrology: C. Augeray, B. Boulet, X. Cagnat, J. Loyen, J.L. Picolo and R. Vidal Environmental concentrations: P. Renaud Verified by: K. Beaugelin-Seiller Date of revision: 18 December 2010 This document is the intellectual property of IRSN and may not be reproduced without its consent. Radionuclide fact sheet NATURAL URANIUM Characteristics Chemical Uranium, a chemical element with atomic number of 92 is part of the actinide family. A pyrophoric grey metal that is very dense in its pure state, uranium is always found combined with other elements, especially oxygen. It has four possible valences (+III to +VI), with valences 4 and 6 the most common in ore. The conditions for passing from valence 4 to valence 6 depend on the reduction potential of the environment; they resemble the conditions for passing from ferrous iron to ferric iron. Hexavalent uranium is much more soluble than tetravalent uranium; it forms complexes, with the most common being uranylcarbonates and uranylsulfates. Nuclear Natural uranium is composed of three main isotopes (234U, 235U and 238U), all of which are radioactive. The two most abundant isotopes on earth are 238U and 235U, which have existed since the planet’s creation. The 234U isotope is produced by alpha disintegration of 238U and represents only a minute share of all uranium. On the other hand, it is more radioactive than the other isotopes and makes up approximately half of all radioactivity from natural uranium. The 235U isotope is the only natural fissile isotope. The enriched, depleted and reprocessed forms of uranium correspond to variable percentages of these isotopes. Other radioactive isotopes of uranium exist, but they are produced artificially (see table below). Natural uranium such as it is extracted from ore contains by weight 99.275% of the isotope 238, 0.719% of isotope 235 and 0.0057% of isotope 234. Thus for 1 g of natural uranium and without taking into account radioactivity of decay products, the chemical element is distributed as follows: 0.99275 g of 238U, or approximately 12,311 Bq; 0.00719 g of 235U, or approximately 576 Bq; 0.000057 g of 234U, or approximately 12,880 Bq. Isotope 232U 233U 234U 235U 236U 238U Natural abundance - - 0.0057 0.719 - 99.275 (% by weight) Half-life (years) 69.8 1.6 × 105 2.5 × 105 7.04 × 108 2.37 × 107 4.47 × 109 Specific activity 8.17 × 1011 3.56 × 108 2.30 × 108 8.00 × 104 2.36 × 106 1.24 × 104 (Bq.g-1) Précursors 232Th 233Pa 234mPa 235mU 236Pa 238Pa 232Pa 233Np 234Pa 235Np 236mNp 242Pu 232Np 237Pu 234Np 239Pu 236Np 236Pu 238Pu 236Pu 240Pu Decay products 228Th 229Th 230Th 231Th 232Th 234Th Principal emission(s) through disintegration (keV) (% emission probability) α 5,320 4,824 4,775 4,397 4,495 4,198 (68.8) (82.7) (71.4) (54) (76) (77.5) γ 57.8 42.5 53.2 185.7 49.4 49.6 (0.2) (0.065) (0.12) (57.1) (0.072) (0.068) X 13.41 13.41 13.41 13.41 13.41 13.41 (10.2) (7) (9.3) (23.2) (7.9) (7.3) (Nucleonica; CE, 2009) 3 Radionuclide fact sheet NATURAL URANIUM Radionuclide fact sheet NATURAL URANIUM Origins Natural The origin of this radioelement is exclusively natural with redistribution related to human activity (Paulin, 1997). Four principal sources of industrial activity enrich certain compartments, including soil, sediment and water, of the biosphere with uranium: - nuclear fuel cycle from uranium mining to waste processing: France has only 3% of reserves and no more domestic production of uranium. In general, nuclear fuel is an alloy of uranium, either uranium dioxide, a mix of uranium and plutonium oxide, or uranium carbide; - military use of depleted uranium (natural uranium in which the 235U content has been reduced by 0.7 to 0.2%). The metal is used for its pyrophoric properties and sites subject to bombardment by this type of weapon are enriched with fine particles of UO2(solid) deposited near the explosion; - use of coal, which emits uranium into the atmosphere during combustion; - agricultural use of phosphate fertilisers produced from natural phosphates that are particularly rich in uranium 238. Artificial Not applicable. Environmental concentrations Conversion rule: radioactivity/weight conversions given below are performed using the assumption of the measurement of uranium 238 in the expected ratio for natural uranium, with 1 Bq of 238U corresponding to 0.08 mg of natural uranium. These conversions are for purposes of information and comparison. In fact, due to possible imbalances between uranium isotopes in the sampled compartments, only measurement is valid. Uranium-related radioactivity for the principal components of the continental environment – air, plants, animals, surface water and sediments, underground water – is related to that of soil, which is itself related to adjacent geological formations. Overall, soils in sedimentary basins and limestone formations have less uranium than those of granite massifs. On a more local level, specific geological conditions may also lead to unusual levels of uranium, particularly in rivers and ground waters (IRSN, 2009). In Europe, median uranium concentration in soil is estimated to be approximately 2 mg.kg-1, with a range of variation from less than 0.1 to more than 50 mg.kg-1 (De Vos and Tarvainen, 2006). The highest concentrations in France are found in the Massif Central in conjunction with secondary hydrothermal alteration of granite domes, vein deposits or the presence of Autunian black schists. These results are coherent with measurements of radioactivity from uranium 238 for the majority of French soil, which vary between several Bq.kg-1 dry weight (d.w.) and several hundred Bq.kg-1 d.w. (several tenths to tens of mg.kg-1 d.w.). They may reach a thousand Bq.kg-1 d.w. (a hundred mg.g-1) in uraniferous granitic soils. Le Roux (2007) proposes an overall average (including all regions, sites and soil types) of 40 Bq.kg-1 d.w. (or approximately 3 mg.kg-1 d.w.). Nevertheless, such an average is necessarily relative because there is significant influence from the representation of soils analysed with regards to various soils found in France. In this instance, samples of soil found on sedimentary substrate are probably overrepresented. In a compilation of French data from various sources, Picat et al. (2002) indicate that an average of 98 Bq.g-1 d.w. (8 mg.kg-1) around facilities upstream of the nuclear cycle, for a range of variation from 25 to 173 Bq.kg-1 d.w. (2 to 14 mg.kg-1). The United Nations Scientific Commission on the Effects of Atomic Radiation (UNSCEAR) assesses radioactivity in the air from 238U to be around 1 µBq.m-3 (UNSCEAR, 2000) based on some references that measure uranium outside the influence of nuclear facilities, as in Poland (1 to 18 µBq.m-3; or 0.08 to 1.5 ng.m-3) and in the USA (0.9 to 5 µBq.m-3; 0.07 to 0.4 ng.m-3). At the Cadarache site in France, where the substrate is sedimentary by nature, a lower value of 0.1 µBq.m3 (0.008 ng.m-3) corresponding to local background was recently measured. In Europe, median uranium concentration in sediments is estimated to be approximately 2 mg.kg-1, with a range of variation from less than 1 to more than 90 mg.kg-1 (De Vos and Tarvainen, 2006). As with soils, sediments from rivers in the Massif Central may have high uranium concentrations of up to 59 mg.kg-1. These results are consistent with those obtained from measuring 238U. Indeed, according to Le Roux (2007), 4 Radionuclide fact sheet NATURAL URANIUM radioactivity from uranium in sediments from rivers in France resembles that in soil: from several Bq.kg-1 d.w.
Load more

Recommended publications
  • Per-10 Basic Information Relating to Uranium
    PER-10 1 BASIC INFORMATION RELATING TO URANIUM-ENRICHMENT CALCULATIONS AND FUEL REQUIREMENTS FOR NUCLEAR POWER REACTORS by K.T. Brown m 3 ATOMIC ENERGY BOARD Pelindaba PRETORIA Republic of South Africa February 1977 :::: : =:::""""""::::::;::: i:::""""""" :::::::::i:::::::::::::::H:::""»"""::::::::::::::::: BASIC INFORMATION RELATING TO URANIUM-ENRICHMENT CALCULATIONS AND FUEL REQUIREMENTS FOR NUCLEAR POWER REACTORS hy K.T. Brown POSTAL ADDRESS: Atomic Energy Board Private Bag X256 PRETORIA 0001 PELINDABA Fi-ln liai v 1977 ISBN U 86Ü6U 654 9 Pago Page SAMEVATTING 2 ABSTRACT 2 3. REACTOR FUEL REQUIREMENTS 5 1. INTRODUCTION 3 3.1 Reactor Types 5 2. URANIUM ENRICHMENT 3 3.1.1 Pressurised-water roactor 5 2.1 Definitions 3 3.1.2 Boiling-water reactor 5 2.1.1 Natural uranium 3 3.1.3 CANDU-PHW 6 2.1.2 Fissile 3 3.1.4 High-temperature gas-cooled reactor 6 2.1.3 Fertile 3 2.1.5 Liquid-metal-cooled fast breeder reactor ... .6 2.1.4 Enrichment 3 3.2 Nuclear Fuel Cycles 6 2.1.5 Product 3 3.3 Typical Fuel Requirements 6 2.1.6 Feed 3 3.3.1 Pressurised-wator reactor 7 2.1.7 Tails, or waste 3 3.3.2 Boiling-water reactor 8 2.1.8 Cascade 3 3.3.3 CANDU-PHW 9 2.1.9 Separative work 4 3.3.4 High-temperature gas-cooled reactor 9 2.1.10 Separative-work unit 4 3.3.5 Liquid-metal-cooled fast breeder reactor ... 10 2.2 Enrichment Parameters 4 3.3.6 Comparative data 10 2.3 Optimum Tails Assay 5 4.
    [Show full text]
  • Uranium Fact Sheet
    Fact Sheet Adopted: December 2018 Health Physics Society Specialists in Radiation Safety 1 Uranium What is uranium? Uranium is a naturally occurring metallic element that has been present in the Earth’s crust since formation of the planet. Like many other minerals, uranium was deposited on land by volcanic action, dissolved by rainfall, and in some places, carried into underground formations. In some cases, geochemical conditions resulted in its concentration into “ore bodies.” Uranium is a common element in Earth’s crust (soil, rock) and in seawater and groundwater. Uranium has 92 protons in its nucleus. The isotope2 238U has 146 neutrons, for a total atomic weight of approximately 238, making it the highest atomic weight of any naturally occurring element. It is not the most dense of elements, but its density is almost twice that of lead. Uranium is radioactive and in nature has three primary isotopes with different numbers of neutrons. Natural uranium, 238U, constitutes over 99% of the total mass or weight, with 0.72% 235U, and a very small amount of 234U. An unstable nucleus that emits some form of radiation is defined as radioactive. The emitted radiation is called radioactivity, which in this case is ionizing radiation—meaning it can interact with other atoms to create charged atoms known as ions. Uranium emits alpha particles, which are ejected from the nucleus of the unstable uranium atom. When an atom emits radiation such as alpha or beta particles or photons such as x rays or gamma rays, the material is said to be undergoing radioactive decay (also called radioactive transformation).
    [Show full text]
  • An Advanced Sodium-Cooled Fast Reactor Core Concept Using Uranium-Free Metallic Fuels for Maximizing TRU Burning Rate
    sustainability Article An Advanced Sodium-Cooled Fast Reactor Core Concept Using Uranium-Free Metallic Fuels for Maximizing TRU Burning Rate Wuseong You and Ser Gi Hong * Department of Nuclear Engineering, Kyung Hee University, Deogyeong-daero, GiHeung-gu, Yongin, Gyeonggi-do 446-701, Korea; [email protected] * Correspondence: [email protected]; Tel.: +82-31-201-2782 Received: 24 October 2017; Accepted: 28 November 2017; Published: 1 December 2017 Abstract: In this paper, we designed and analyzed advanced sodium-cooled fast reactor cores using uranium-free metallic fuels for maximizing burning rate of transuranics (TRU) nuclides from PWR spent fuels. It is well known that the removal of fertile nuclides such as 238U from fuels in liquid metal cooled fast reactor leads to the degradation of important safety parameters such as the Doppler coefficient, coolant void worth, and delayed neutron fraction. To resolve the degradation of the Doppler coefficient, we considered adding resonant nuclides to the uranium-free metallic fuels. The analysis results showed that the cores using uranium-free fuels loaded with tungsten instead of uranium have a significantly lower burnup reactivity swing and more negative Doppler coefficients than the core using uranium-free fuels without resonant nuclides. In addition, we considered the use of axially central B4C absorber region and moderator rods to further improve safety parameters such as sodium void worth, burnup reactivity swing, and the Doppler coefficient. The results of the analysis showed that the final design core can consume ~353 kg per cycle and satisfies self-controllability under unprotected accidents. The fuel cycle analysis showed that the PWR–SFR coupling fuel cycle option drastically reduces the amount of waste going to repository and the SFR burner can consume the amount of TRUs discharged from 3.72 PWRs generating the same electricity.
    [Show full text]
  • 12 Natural Isotopes of Elements Other Than H, C, O
    12 NATURAL ISOTOPES OF ELEMENTS OTHER THAN H, C, O In this chapter we are dealing with the less common applications of natural isotopes. Our discussions will be restricted to their origin and isotopic abundances and the main characteristics. Only brief indications are given about possible applications. More details are presented in the other volumes of this series. A few isotopes are mentioned only briefly, as they are of little relevance to water studies. Based on their half-life, the isotopes concerned can be subdivided: 1) stable isotopes of some elements (He, Li, B, N, S, Cl), of which the abundance variations point to certain geochemical and hydrogeological processes, and which can be applied as tracers in the hydrological systems, 2) radioactive isotopes with half-lives exceeding the age of the universe (232Th, 235U, 238U), 3) radioactive isotopes with shorter half-lives, mainly daughter nuclides of the previous catagory of isotopes, 4) radioactive isotopes with shorter half-lives that are of cosmogenic origin, i.e. that are being produced in the atmosphere by interactions of cosmic radiation particles with atmospheric molecules (7Be, 10Be, 26Al, 32Si, 36Cl, 36Ar, 39Ar, 81Kr, 85Kr, 129I) (Lal and Peters, 1967). The isotopes can also be distinguished by their chemical characteristics: 1) the isotopes of noble gases (He, Ar, Kr) play an important role, because of their solubility in water and because of their chemically inert and thus conservative character. Table 12.1 gives the solubility values in water (data from Benson and Krause, 1976); the table also contains the atmospheric concentrations (Andrews, 1992: error in his Eq.4, where Ti/(T1) should read (Ti/T)1); 2) another category consists of the isotopes of elements that are only slightly soluble and have very low concentrations in water under moderate conditions (Be, Al).
    [Show full text]
  • The Nuclear Fuel Cycle
    THE COLLECTION > From the uranium mine> toI wNTasRtOeD dUisCpToIsOaN l 1 > The atom 2 > Radioactivity 3 > Radiation and man 4 > Energy 5 > Nuclear energy: fusion and fission 6 > How a nuclear reactor works 7 > The nuclear fuel cycle 7 > The nuclear fuel cycle FROM RESEARCH 8 > Microelectronics 9 > The laser: a concentrate of light TO INDUSTRY 10 > Medical imaging 11 > Nuclear astrophysics 12 > Hydrogen 7 >>TThhee nnuucclleeaarr ffuueell ccyyccllee UPSTREAM THE REACTOR: PREPARING THE FUEL IN THE REACTOR: FUEL CONSUMPTION DOWNSTREAM THE REACTOR: REPROCESSING NUCLEAR WASTE NUCLEAR WASTE © Commissariat à l’’Énergie Atomique et aux Energies Alternatives, 2005 Communication Division Bâtiment Siège - 91191 Gif-sur-Yvette cedex www.cea.fr ISSN 1637-5408. From the uranium mine to waste disposal 7 > The nuclear fuel cycle From the uranium mine to waste disposal 7 > The nuclear fuel cycle 2 > CONTENTS > INTRODUCTION 3 Uranium ore is extracted from open-pit mines – such as the McClear mines in Canada seen here – or underground workings. a m e g o C © “The nuclear fuel cycle includes an erray UPSTREAM THE REACTOR: of industrial operations, from uranium PREPARING THE FUEL 4 e mining to the disposal of radioactive l Extracting uranium from the ore 5 waste.” c Concentrating and refining uranium 6 y Enriching uranium 6 c Enrichment methods 8 l introduction uel is a material that can be burnt to pro - IN THE REACTOR: FUEL CONSUMPTION 9 Fvide heat. The most familiar fuels are wood, e Preparing fuel assemblies 10 coal, natural gas and oil. By analogy, the ura - e g a nium used in nuclear power plants is called Per unit or mass (e.g.
    [Show full text]
  • 1 Introduction
    1 Introduction WHO commissions reviews and undertakes health risk assessments associated with exposure to potentially hazardous physical, chemical and biological agents in the home, work place and environment. This monograph on the chemical and radiological hazards associated with exposure to depleted uranium is one such assessment. The purpose of this monograph is to provide generic information on any risks to health from depleted uranium from all avenues of exposure to the body and from any activity where human exposure could likely occur. Such activities include those involved with fabrication and use of DU products in industrial, commercial and military settings. While this monograph is primarily on DU, reference is also made to the health effects and behaviour of uranium, since uranium acts on body organs and tissues in the same way as DU and the results and conclusions from uranium studies are considered to be broadly applicable to DU. However, in the case of effects due to ionizing radiation, DU is less radioactive than uranium. This review is structured as broadly indicated in Figure 1.1, with individual chapters focussing on the identification of environmental and man-made sources of uranium and DU, exposure pathways and scenarios, likely chemical and radiological hazards and where data is available commenting on exposure-response relationships. HAZARD IDENTIFICATION PROPERTIES PHYSICAL CHEMICAL BIOLOGICAL DOSE RESPONSE RISK EVALUATION CHARACTERISATION BACKGROUND EXPOSURE LEVELS EXPOSURE ASSESSMENT Figure 1.1 Schematic diagram, depicting areas covered by this monograph. It is expected that the monograph could be used as a reference for health risk assessments in any application where DU is used and human exposure or contact could result.
    [Show full text]
  • Sources of Variation in the Stable Isotopic Composition of Plants*
    CHAPTER 2 Sources of variation in the stable isotopic composition of plants* JOHN D. MARSHALL, J. RENÉE BROOKS, AND KATE LAJTHA Introduction The use of stable isotopes of carbon, nitrogen, oxygen, and hydrogen to study physiological processes has increased exponentially in the past three decades. When Harmon Craig (1953, 1954), a geochemist and early pioneer of natural abundance stable isotopes, fi rst measured isotopic values of plant materials, he found that plants tended to have a fairly narrow δ13C range of −25 to −35‰. In these initial surveys, he was unable to fi nd large taxonomic or environmental effects on these values. Since that time ecologists have identi- fi ed clear isotopic signatures based not only on different photosynthetic pathways, but also on ecophysiological differences, such as photosynthetic water-use effi ciency (WUE) and sources of water and nitrogen used. As large empirical databases have accumulated and our theoretical understanding of isotopic composition has improved, scientists have continued to discover mismatches between theoretical and observed values, as well as confounding effects from sources and factors not previously considered. In the best tradi- tion of science, these discoveries have led to important new insights into physiological or ecological processes, as well as new uses of stable isotopes in plant ecophysiology. This chapter reviews the most common applications of stable isotope analysis in plant ecophysiology. Carbon isotopes Photosynthetic pathways 13 Plants contain less C than the atmospheric CO2 on which they rely for photosynthesis. They are therefore “depleted” of 13C relative to the atmo- sphere. This depletion is caused by enzymatic and physical processes that discriminate against 13C in favor of 12C.
    [Show full text]
  • Characterisation of Various Types of Alloy by K0-Neutron Activation Analysis
    A27 CHARACTERISATION OF VARIOUS TYPES OF ALLOY BY K0-NEUTRON ACTIVATION ANALYSIS M. WASIM, N. KHALID, M. ARIF Chemistry Division, Pakistan Institute of Nuclear Science and Technology, Islamabad, Pakistan N.A. LODHI Isotope Production Division, Pakistan Institute of Nuclear Science and Technology, Islamabad, Pakistan Abstract Samples of certified alloys were analysed by semi-absolute, standardless k0-instrumental neutron activation analysis (k0-INAA) for compositional decoding. Irradiations were performed at Miniaturised Neutron Source Reactor (MNSR) located at Pakistan Institute of Nuclear Science and Technology, Islamabad having nominal thermal neutron fluxes of 1×1012 cm-2s-1. The experimentally optimised parameters for NAA suggested a maximum of three irradiations for the quantification of 21 elements within 5 days. The same experimental conditions produced quantitative results of 13 elements, which were not reported by the supplier of the reference materials. All reference concentrations were within 95% confidence interval of the determined concentrations. 1. INTRODUCTION Worldwide interest in the determination of elements in different materials has led to the development of many analytical techniques. The commonly used techniques include inductively coupled plasma with optical emission spectrometry (ICP-OES), X-ray fluorescence spectrometry (XRF), atomic absorption spectrometry (AAS) [1], arc/spark optical emission spectrometry, ICP with mass spectrometry and laser-induced breakdown spectroscopy [2-4]. Nuclear analytical techniques also play important role in material characterisation [5]. Among these the noticeable are particle induced X-ray emission, proton activation analysis [6,7], prompt gamma-ray neutron activation [8], fast neutron activation analysis [9,10] and thermal neutron activation analysis (NAA) [11,12]. The non-nuclear techniques apply relative standardisation, also known as classical linear calibration, whereby a calibration curve is drawn by using three or more calibration standards.
    [Show full text]
  • Measuring Long-Range 13C–13C Correlations on a Surface Under
    Ames Laboratory Accepted Manuscripts Ames Laboratory 10-13-2017 Measuring Long-Range 13C–13C Correlations on a Surface under Natural Abundance Using Dynamic Nuclear Polarization-Enhanced Solid- State Nuclear Magnetic Resonance Takeshi Kobayashi Ames Laboratory, [email protected] Igor I. Slowing Iowa State University and Ames Laboratory, [email protected] Marek Pruski Iowa State University and Ames Laboratory, [email protected] Follow this and additional works at: http://lib.dr.iastate.edu/ameslab_manuscripts Part of the Materials Chemistry Commons, and the Physical Chemistry Commons Recommended Citation Kobayashi, Takeshi; Slowing, Igor I.; and Pruski, Marek, "Measuring Long-Range 13C–13C Correlations on a Surface under Natural Abundance Using Dynamic Nuclear Polarization-Enhanced Solid-State Nuclear Magnetic Resonance" (2017). Ames Laboratory Accepted Manuscripts. 33. http://lib.dr.iastate.edu/ameslab_manuscripts/33 This Article is brought to you for free and open access by the Ames Laboratory at Iowa State University Digital Repository. It has been accepted for inclusion in Ames Laboratory Accepted Manuscripts by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Measuring Long-Range 13C–13C Correlations on a Surface under Natural Abundance Using Dynamic Nuclear Polarization-Enhanced Solid-State Nuclear Magnetic Resonance Abstract We report that spatial (<1>nm) proximity between different molecules in solid bulk materials and, for the first time, different moieties on the surface of a catalyst, can be established without isotope enrichment by means of homonuclear CHHC solid-state nuclear magnetic resonance experiment. This 13C–13C correlation measurement, which hitherto was not possible for natural-abundance solids, was enabled by the use of dynamic nuclear polarization.
    [Show full text]
  • Long Term Sustainability of Nuclear Power in India - Prospects and Challenges
    Page | 45 5 LONG TERM SUSTAINABILITY OF NUCLEAR POWER IN INDIA - PROSPECTS AND CHALLENGES Vipin Shukla, Vivek J. Pandya and C. Ganguly ABSTRACT: Nuclear power is emerging as a viable for at least 12 additional indigenous PHWR 700 carbon – free option for India to meet the ever- reactors. The target is to have ~ 45,000 MWe nuclear increasing demand of base – load electricity at an power by 2030. Since the last six years, India has affordable price, in a safe, secured and sustainable also been importing natural uranium oreconcentrate manner. Since the 1970s, India had been pursuing (UOC) and finished natural UO2 pellets tofuel the a self-reliant indigenous nuclear power program ten PHWR 220 units at Rawathbhata, Kakrapara and linking the fuel cycles of Pressurized Heavy Water Narora. India has also been importing enriched UO2 Reactor (PHWR), Fast Breeder Reactor (FBRs) and fuel for the two BWRs at Tarapur and the two VVERs thorium-based self-sustaining breeder in stage 1, 2 at Kudankulunm. The present paper summarizes the and 3 respectively, for efficient utilization of modest on-going and the expanding nuclear power program low grade (0.03-0.06 % U3O8) uranium reserves but in India highlighting the challenges of availability of vast thorium resources. Natural uranium fueled uranium and plutonium for manufacturing nuclear PHWR is the backbone of the program. India has fuels. achieved industrial maturity in PHWR and the related uranium fuel cycle technology. Presently, 21 reactors are in operation, including 16 units of PHWR 220 MWe, 2 units of PHWR 540 MWe, 2 units of Boiling Water Reactor (BWR) 160 MWe and a (Water KEYWORDS Water Energy Reactor) VVER 1000 MWe.
    [Show full text]
  • Highly Enriched Uranium: Striking a Balance
    OFFICIAL USE ONLY - DRAFT GLOSSARY OF TERMS APPENDIX F GLOSSARY OF TERMS Accountability: That part of the safeguards and security program that encompasses the measurement and inventory verification systems, records, and reports to account for nuclear materials. Assay: Measurement that establishes the total quantity of the isotope of an element and the total quantity of that element. Atom: The basic component of all matter. Atoms are the smallest part of an element that have all of the chemical properties of that element. Atoms consist of a nucleus of protons and neutrons surrounded by electrons. Atomic energy: All forms of energy released in the course of nuclear fission or nuclear transformation. Atomic weapon: Any device utilizing atomic energy, exclusive of the means for transportation or propelling the device (where such means is a separable and divisible part of the device), the principal purpose of which is for use as, or for development of, a weapon, a weapon prototype, or a weapon test device. Blending: The intentional mixing of two different assays of the same material in order to achieve a desired third assay. Book inventory: The quantity of nuclear material present at a given time as reflected by accounting records. Burnup: A measure of consumption of fissionable material in reactor fuel. Burnup can be expressed as (a) the percentage of fissionable atoms that have undergone fission or capture, or (b) the amount of energy produced per unit weight of fuel in the reactor. Chain reaction: A self-sustaining series of nuclear fission reactions. Neutrons produced by fission cause more fission. Chain reactions are essential to the functioning of nuclear reactors and weapons.
    [Show full text]
  • Determination of Particulate and Dissolved 228Th in Seawater Using a Delayed Coincidence Counter
    MARCHE-03183; No of Pages 7 Marine Chemistry xxx (2014) xxx–xxx Contents lists available at ScienceDirect Marine Chemistry journal homepage: www.elsevier.com/locate/marchem Determination of particulate and dissolved 228Th in seawater using a delayed coincidence counter Kanchan Maiti a,b,⁎, Matthew A. Charette b, Ken O. Buesseler b,KuanboZhoub, Paul Henderson b, Willard S. Moore c,PaulMorrisb, Lauren Kipp b a Department of Oceanography and Coastal Sciences Louisiana State University, Baton Rouge, LA 70803, USA b Department of Marine Chemistry and Geochemistry Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA c Department of Earth and Ocean Sciences, University of South Carolina, Columbia, SC 29208, USA article info abstract Article history: The application of thorium-228 towards understanding particle dynamics in the open ocean is limited because of Received 13 August 2014 its low natural abundance in seawater and associated sampling and analytical challenges. Here we describe a fast Received in revised form 26 November 2014 and nondestructive method for measuring both dissolved and particulate 228Th activities in the open ocean using Accepted 7 December 2014 Radium Delayed-Coincidence Counters (RaDeCC). Particulate and dissolved samples were collected from the Available online xxxx upper 1000 m of the Sargasso Sea water column during the US GEOTRACES intercalibration cruise using large vol- ume in situ pumps equipped with Quartz microfiber filters and MnO impregnated cartridges. Samples were di- Keywords: 2 fi Thorium-228 rectly counted on the RaDeCC system using a custom machined lter sample holder and a commercially available Particle flux cartridge holder followed by traditional alpha counting.
    [Show full text]