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WhatChapter 1. Introduction and Basic concepts Chapter 2. Radiation Chapter 3. Basic Instrumentation for Nuclear Technology Chapter 4. Power From Fission Chapter 5. Thermonuclear Fusion Chapter 6. Nuclear Weapons Chapter 7. Nuclear Waste Chapter 8. Radioactive isotopes and Their Applications Chapter 9. Nuclear Analysis Methods Chapter 10. Nuclear Technology in Industry and Agriculture Chapter 11. Medical Applications of Nuclear Technology Chapter 12. Impact, Issues and Future of Nuclear Technology
References
1) Fundamentals of Nuclear Science and Engineering, J.Kenneth Shultis and Richard E.Faw (Marcel Dekker)
2) Nuclear Physics - Principles and Applications, J.S.Lilley, (John Wiley & Sons, Ltd )
3) Nuclear Technology, Joseph A. Angelo,Jr (Greenwood Press)
4) Nuclear Energy – Principles, Practices, and Prospects, David Bodansky (Springer)
5) Introduction to Nuclear Technology, Lecture notes by Chung Chieh
The Assessment
• Class discussion and home work 40%
• Midterm report 10%
• Final Exam 50%
one’s work is performed honestly !
1.The Significance of Nuclear Technology 2.Early Discoveries 3.Basic Facts and Definitions
4.Units SI system, Physical constants, natural unit
5.Nuclear Reactions
Chapter 1. Introduction and Basic concepts
Discovery of nuclear reactions (n.r.).Energy in n.r.Neutron induced nuclear reactionsSimple theories or concepts related to n.r.Types of n.r.Applications of n.r.
6
Nature’s Hierarchy – a biological view? ? ?
Sub-Atomic ParticlesAtom
MoleculeOrganelle
CellTissueOrgan
Organ SystemMulticellular Organism
PopulationCommunityEcosystemBiosphere
1)Widely applied
1.1 The Significance of Nuclear Technology
1)Widely applied
• medicine, basic research, agriculture, industry, archaeology, geology, environmental science, and space exploration
• nuclear technology has played a dominant role in national security and geopolitics
• GDP 4.7% (USA)
Extensively Collaboration
1.1 The Significance of Nuclear Technology
2) Alter the course of Human civilization
Prometheus stole fire from Mount Olympuscontrol of fire ultimately enabled the human race to evolve into the technically complex global civilization
Enrico Fermi nuclear reactorStarted a new technical erahuman beings might wisely harvest the energy within the atomic nucleus in a controlled manner
1942
Atomic Bomb - the age of nuclear weaponry.
Human beings were capable of unleashing wholesale destruction on planet Earth
Pandora Box deliver misfortune into the house of man
05:29:45 ， J uly16 ， 1945
3) Skill and Wisdom
how the technology works INNOVATION to make a unanimous decision to promote and harvest only the beneficial aspects of nuclear technology CAREFULNESS
Instead of becoming the destroyer of worlds, nuclear technology should represent a powerful technology that serves as the saver of worlds and the protector of Earth CONSCIENCE
1.1 The Significance of Nuclear Technology
1.2 Early Discoveries
Leucippus and Democritus (c. 460–c. 370 B.C.) The theory of atomism--The Four ElementsEarth Air
Fire Water
Democritus ， atomos (ατομος), “not divisible.”
• 1803, J.Dalton ， suggested that each chemical element was composed of a particular type of atom.
• 1811, A.Avogadro, Avogadro’s Law.
• 1869, Mendeleev ，
？Is an atom divisible
the molecule as the smallest particle of any substancemolecules, consisted of collections of atoms
Dalton’s Atomic TheoryDalton (1766-1844 ): all substances are made of small, indivisible, and fundamental natural units called atoms.
Various symbols like these hadbeen used to represent atoms of
different elements by Dalton
The law of partial pressure of gases:
the pressure of a fixed volume of gases was proportional to the number of atoms present
Molecules
Failure of Dalton’s atomic theory
2 H + O = 2 HO 2 H + O = H2O (does not agree with volume measured) H + O = HO (does not agree with volume measured)
Avogadro(1775-1856 ): natural units (for chemical reactions are molecules rather than single atoms.
1 vol. O2 + 2 vol. H2 2 vol. H2O2 CO (g) + O2 (g)
Avogadro’s number = 6.0221367e23 molecules mol-1 (physical constant)
1895 , Roentgen, X-ray
Dec.22, 1895
Causing the sheet to glow was a penetrating form of radiation. He called this unknown radiation X-rays.
penetrating rays could reveal the internal structure of opaque objects
Crookes tube
1896 , Becquerel, the discovery of radioactivity
The uranium salt produced an intense silhouette of itself on the photographic plate
18
Marie and Pierre Curie
1898, named the emissions (alpha & beta) from uranium radioactivity
Discovered the chemical elements radium and polonium
1897, Thomson, the discovery of electron
Atom, was in fact divisible and contained “smaller parts.”
“plum pudding”model
the atom was a distributed positively charged mass with an appropriate number of tinyelectrons embedded in it
"It was as incredible as if you fired a 15-inch shell at a piece of tissue paper and it came back and hit you."
1911, Rutherford, nuclear model of the atom
a tiny central positive core that contained almost all the atom’s mass. The nucleus was surrounded by electrons in appropriate number to maintain a balance of electrical charge.
RadioactivityRadioactivityErnest Rutherford determined there were 3 kinds of radioactivity
1932, Chadwick discovered the neutron
complete the basic model of the nuclear atom: a central, positively charged nucleuscontaining protons and neutrons that was surrounded by a discretely organized cloud of orbiting electrons.
neutron-related nuclear research
http://www2.lucidcafe.com/lucidcafe/library/library.html#science
1. 人类寻找物质构造基本单元的历程
>10-2 cm(?) 10-8 cm 10 -12 cm 10-13 cm ?
Nuclide Z N A Symbol
碳 -12 6 6 12 12C
碳 -13 6 7 13 13C
碳 -14 6 8 14 14C
25
Atomic and Nuclear StuctureAtomic and Nuclear Stucture Atom - smallest unit of a chemical element
Size on the order of 10-8 cm (1 Angstrom) Contains Z electrons (Qe = -1e, me = 0.511 MeV/c2)
– e = 1.602x10-19 Coulomb– and
Nucleus – Size on the order of 10-13 cm (1 Fermi ) Contains more than 99.9% of the mass of the atom Made of Z protons and N neutrons Proton (Qp = +1e, mp = 938.28 MeV/c2 ) Neutron (Qn = 0, mn = 939.57 MeV/c2 ) A = Atomic mass = Z + N Held together by strong nuclear force
ZXN where X = chemical symbolA ~ 2.3 1014 g/cm3
Nobel Prizes in Nuclear Science
1.The Significance of Nuclear Technology 2.Early Discoveries 3.Basic Facts and Definitions
4.Units SI system, Physical constants, natural unit
5.Nuclear Reactions
Chapter 1. Introduction and Basic concepts
Discovery of nuclear reactions (n.r.).Energy in n.r.Neutron induced nuclear reactionsSimple theories or concepts related to n.r.Types of n.r.Applications of n.r.
1) The nucleus and its constituents
1.3 Basic Facts and Definitions
Nuclide 核素 : a term used to refer to a particular atom or nucleus with a specific neutron number N and atomic (proton) number Z.
Isotopes 同位素 : atoms of the same element with different number of neutron
isobar 同量异位素 : nuclides with the same mass number A = N + Z but with different number of neutrons N and protons Z.
Isotone 同中子异位素 : nuclides with the same number of neutrons N but different number of protons Z.
isomer 同质异能素 : the same nuclide (same Z and N) in which the nucleus is in different long lived excited states.
2) Nuclear Nomenclature
nuclear jargon
Z N A Examples
isotope Same D D 1H 2H 3H
isotone D Same D 2H 3He
isobar D D Same 3H 3He
isomer Same Same Same 99Te 99mTe
Calculation of Hydrogen Atomic Weight
Isotope atomic mass Abundance atomic mass abundance
1H 1.00782503 0.99985 1.0076742H 2.014102 0.00014
80.000298
3H 3.016049 TraceAtomic weight for H = 1.007674 + 0.00298 = 1.007972
• 39K (93.2%)
• 59Co
• 88Sr
• 127I
• 133Cs
一些放射性同位素
Are the chemical properties of isotopes nearly identical?
40K 1.28x108 a
60Co 5.27 a
90Sr 28.8 a
131I 8.04 d
137Cs 30.12 a
Stable Nuclides
Stable nuclides remain the same for an indefinite period.
Some characteristics of stable nuclides:
Atomic number Z 83, but no stable isotopes for Z = 43 and 61.
There are 81 elements with 280 stable nuclides.
Usually there are more neutrons than protons in the nuclei.
Nuclides with magic number of protons or neutrons are very stable.
Pairing of nucleons (spin coupling) contributes to nuclide stability.
Is abundance of a nuclide related to its stability?
Stable Nuclidesnumber of neutrons and protons
Find
N / Z for
4He2 = 116O8 =40Ar18 = 91Zn40 = 144Nd60 = 186Re75 =
209Bi83 =
N = # of neutrons
Z = # of protons
Stable NuclidesN/Z of some light nuclides
Z Stable Nuclides| (Magic numbers and double magic-number nuclides are in bold) (to be continued)21 Sc20 . . . . . . . . . . . . . . . . . . . Ca Ca Ca Ca Ca Ca19 K K K18 Ar Ar Ar .17 Cl Cl16 S S S S15 . . . . . . . . . . . . . . P14 Si Si Si . .13 Al12 Mg Mg Mg . . .11 Na10 . . . . . . . . . . Ne Ne Ne 9 F . . . 8 O O O 7 N N 6 C C . . . . 5 . . . . B B 4 Be . . . . 3 Li Li 2 He He . . . . . 1 P D N 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
Stable NuclidesN/Z of nuclides 40 Zr . . . . . . . . + . . . XXX X X
39 Y X38 Sr X XXX 37 Rb X X 36 Kr X X XX X 35 Br . . . . . + . . X X34 Se XXXX X X33 As X32 Ge X XXX X . 31 Ga X X30 Zn . . . + . X XXX X . 29 Cu X X28 Ni X XXX X . . 27 Co X26 Fe X XXX . . 25 Mn + X24 Cr X XXX . . 23 v XX22 Ti XXXXX . . . 21 Sc X 20 Ca X X 2 2 3 4 5 01234567890123456789012345678901
N / A ratio increases as A increases
More stable isotopes for even Z than odd Z
More stable isotones for even N than odd N
More stable isotopes and isotones for magic Z and N
Stable Nuclidesnatural occurring heavy nuclides
Natural Occurring Isotopes of Heavy Elements (abundance)
76 Os 184 (0.018), 186 (1.59), 187 (1.64), 188 (13.3), 189 (16.1), 190 (26.4), 192 (41.0)77 Ir 191 (38.5), 193 (61.5)78 Pt 190 (0.0127), 192 (0.78), 194 (32.9), 195 (33.8), 196 (25.2), 198 (7.19)79 Au 197 (100)80 Hg 196 (0.146), 198 (10.02), 199 (16.84), 200(23.13), 201(13.22), 202(29.8), 204(6.85)81 Tl 203 (29.5), 205 (70.5)82 Pb 204 (1.4), 206 (25.1), 207 (21.7), 208 (52.3)83 Bi 209 (100)
90 Th 232 (100% half life 1.4x1010 y)
92 U 235 (0.720, half life 7.04x108 y), 238 (99.276, half life 4.5x109 y)
Stable Nuclidespairing of nucleons
Effect of Paring Nucleons
Z N # of stable stable nuclides
even even 166even odd 57odd even 53odd odd *4
total 280
*They are: 2D1, 6Li3, 10B5, & 14N7
Two protons or neutrons occupy a quantum state, due to their ½ spin.
Pairing nucleons stabilises nuclides, leading to a large number of stable nuclides with even Z and N.
No stable isotopes for Z = 43 or 61.
No stable isotones with N = 19, 31, 35, 39, 61, 89
More stable isotopes for even Z than odd Z and for even N than odd N
Elements with even Z are more abundant than those with odd Z of comparable mass.
Stable Nuclidesmagic numbers of nucleons
Magic numbers are 2, 8, 20, 28, 50, 82, and 126.
Double-magic number nuclides: 4He2, 16O8, 40Ca20, 48Ca20, & 208Pb82.
4He2 as alpha particles, abundant in the universe, 16O8 abundant on Earth.
Six stable isotopes of Ca20, 5 stable isotopes of Ni28, high for their masses.
Large number of stable isotopes and isotones with Z & N = 50 and 82.
The heavies stable nuclide 209Bi83 has 126 neutrons.
O8, Ca20, Ni28, Sn50 and Pb82 have relative high abundance.
The binding energy (BE) of a nuclide is the energy released when the atom is synthesized from the appropriate numbers of hydrogen atoms and neutrons.
Z H + N n = AE + BE
or Z mH + N mn = mE + BEwhere mH, mn, and mE are masses of H, n, and AE respectively.Eg
BE = Z mH + N mn - mE
BE (3He) = (2*1.007825 + 1.008665 - 3.01603) 931.481 MeV = 7.72 MeV
BE (4He) = (2*1.007825 + 2*1.008665 - 4.00260) 931.481 MeV = 28.30 MeV
3) Nuclear mass and energy),()()(),(M 1 AZMmZAHZMAZ n
The more the binding energy, the more stable is the nuclide.
Stable and Radioactive Nuclidesaverage binding energy
The binding energy and averagebinding energy of some nuclides
Nuclide BE BE / A MeV MeV / nucleon
3He2 7.72 2.574He2 28.3 7.0816O8 127.6 7.9856Fe26 492.3 8.79 54Fe26 471.76 8.74 208Pb82 1636.44 7.87 238U92 1801.7 7.57
Variation of the Average Binding Energyas a Function of Mass Number A
Fe
U
3He
BEa
v
A
BE A
A
The Average Binding Energy Curve
Stable and Radioactive Nuclides
a semi-empirical equation for BE
BE(A,Z) = 14.1A - 13A2/3 - - + Ea
3/1
26.0
A
ZA
ZA 2)2(20
Proportional to A
Decrease due to surface tension
Instability due to p
Instability due to neutron to proton ratio
Pairing of nucleon
Stable and Radioactive Nuclidesmass excess (ME)
The difference between the mass of a nuclide and its mass number, A, is the mass excess (ME),
ME = mass - A.
Masses (amu) of some entitiesH 1.00782503 18O 17.999162D 2.014102 54Fe 54.938296 3H 3.016049 56Fe 55.9349394He 4.002603 206Pb 205.97587212C 12.000000 209Bi 208.980414C 14.003242 235U 235.04392416O 15.994915 238U 238.055040 What are the MEs for the
nuclides listed here?
Which is the standard?
Which have negative MEs?
Stable and Radioactive Nuclidesmass excess (ME) and average -BE
Comparison of mass excess and average binding energy (amu)
Nuclide Mass ME -BE average BE
H 1.007825 0.007825 0 0n 1.008665 0.008665 0 0
3He 3.01603 0.01603 -0.00276 0.008284He 4.00260 0.00260 -0.0076 0.030412C 12.000000 0 -0.00825 0.0989416O 15.994915 -0.005085 -0.00857 0.1369
40Ca 39.96259 -0.03741 -0.00917 0.3669 54Fe 53.939612 -0.060388 -0.00938 0.506556Fe 55.934939 -0.065061 -0.00944 0.52851
208Pb82 207.976627 -0.023373 -0.00845 1.757238U92 238.050784 0.050784 -0.00813 1.934
Stable and Radioactive Nuclidesfission and fusion energy and ME
Variation of ME with Afor Some Stable Nuclides
ME amu
0.01
0.005
0.0
–0.005
A
H
3He
4He12C
FePb
U
n
Stable and Radioactive Nuclidesapplication of mass excess (ME)
Like masses, the ME can be used to calculate energy of decay, because the same scale is used for both.
eg:
ME’s of 40Sc21 and 40Ca20 are -20.527 and -34.847 MeV respectively. Estimate the energy of decay for
40Sc21 40Ca20 + + or 40Sc21 + e– 40Ca20
solution:Edecay = -20.527 - (-34.847) = 14.32 MeV
Edecay includes 1.02 MeV for the positron-electron pair for + decay.
1.The Significance of Nuclear Technology 2.Early Discoveries 3.Basic Facts and Definitions
4.Units Grammar, SI system, Physical constants, natural unit
5.Nuclear Reactions
Chapter 1. Introduction and Basic concepts
Discovery of nuclear reactions (n.r.).Energy in n.r.Neutron induced nuclear reactionsSimple theories or concepts related to n.r.Types of n.r.Applications of n.r.
1) Grammar1.4 Units
Capitalization
Space
plural
A unit name is never capitalized even if it is a person's name. Thus curie, not Curie. However, the symbol or abbreviation of a unit named after a person is capitalized. Thus Sv, not sv.
Use 58 m, not 58m .
A symbol is never pluralized. Thus 8 N, not 8 Ns or 8 Ns .
raised dots
Solidis
mixing units/names
prefix
Sometimes a raised dot is used when combining units such as N.m2.s; however, a single space between unit symbols is preferred as in N m2 s.
For simple unit combinations use g/cm3 or g cm-3. However, for more complex expressions, N m-2 s-1 is much clearer than N/m2/s.
Never mix unit names and symbols. Thus kg/s, not kg/second or kilogram/s.
Never use double prefixes such as μμg; use pg. Also put prefixes in the numerator. Thus km/s, not m/ms.
double vowels
Hyphens
numbers
When spelling out prefixes with names that begin with a vowel, supress the ending vowel on the prefix. Thus megohm and kilohm, not megaohm and kiloohm.
Do not put hyphens between unit names. Thus newton meter, not newton-meter. Also never use a hyphen with a prefix. Hence, write microgram not micro-gram.
For numbers less than one, use 0.532 not .532. Use prefixes to avoid large numbers; thus 12.345 kg, not 12345 g. For numbers with more than 5 adjacent numerals, spaces are often used to group numerals into triplets; thus 123 456 789.123 456 33, not 123456789.12345633.
"International System of Units“(1) Base units(2) derived units which are combinations of the
base units,(3) supplementary units(4) temporary units which are in widespread use
for special applications.(5) Special Nuclear Units
2) SI system
(1) Base units
Physical quantity
length
mass
time
electric current
thermodynamic temperature
luminous intensity
quantity of substance
Unit name
meter
kilogram
second
ampere
kelvin
candela
mole
Symbol
m
kg
s
A
K
cd
mol
(2) derived units
(3) supplementary units
(4) special applications
(5) Special Nuclear Units
is the kinetic energy gained by an electron (mass me
and charge -e) that is accelerated through a potential difference ΔV of one volt. The work done by the electric field is -eΔV = (1.60217646 x 10-19 C)(1 J/C) = 1.60217646 x 10-19 J = 1 eV.
The Electron Volt 1 eV= 1.602 176 46 x 10-19 J
The Atomic Mass Unit 1 amu = 1.6605387 x 10-27 kg
1/12 the mass of a neutral ground-state atom of 12C.
3) Physical constants
4) Natural Units
Units such as meter, second, joule, calorie, gram, kilogram etc are artificial (man-made) units.
The fundamental components of materials are called the natural units.
remain the same during changes
Atoms, electrons, molecules, and moles are natural units or building blocks of matter. Photons are natural units of EM radiation (energy).
Earth Water
Cold
Wet Dry
Hot
Fire Air
1.The Significance of Nuclear Technology 2.Early Discoveries 3.Basic Facts and Definitions 4.Units 5.Nuclear Reactions
Chapter 1. Introduction and Basic concepts
Discovery of nuclear reactions (n.r.).Energy in n.r., ExperimentalNeutron induced nuclear reactionsSimple theories or concepts related to n.r.Types of n.r.Applications of n.r.
1.5 Nuclear Reactions
Energy drives all reactions, physical, chemical, biological, and nuclear.
Physical reactions change states of material among solids, liquids, gases, solutions. Molecules of substances remain the same.
Chemical reactions change the molecules of substances, but identities of elements remain the same.
Biological reactions are combinations of chemical and physical reactions.
Nuclear reactions change the atomic nuclei and thus the identities of nuclides. They are accomplished by bombardment using subatomic particles or photons.
She points it to the rock, and the rock turns into gold.
- a legend
200Hg + 1H 197Au + 4He
Discoveries of Nuclear Reactions
source & tracks with long & thin proton track
and thin proton spots on fluorescence screen
In 1914, Marsden and Rutehrford saw some thin tracks and spots among those due to particles. They attributed them to protons and suggested the nuclear reaction:
14N + 4He 17O + 1H or 14N (, p)17O
F. Joliot and I. Curie discovered the reaction
27Al (, n) 30P ( , + or EC) 30Si, half life of 30P is 2.5 min
"the nitrogen atom is disintegrated under the intense force developed in a close collision with a swift particle".
Smashing the Atoms
In 1929, John Cockroft and Ernest Walton used 700,000 voltage to accelerate protons and bombarded lithium to induce the reaction,
7Li + p 2
They called it smashing the atoms, a mile stone in the discovery of nuclear reaction. This reaction is also a proton induced fission, and illustrates the stability of the helium nuclide.
They received the Nobel prize for physics in 1951.
Use the discover of n.r. to explain n.r.
Nuclear Reactions changing the hearts of atoms
Nuclear reactions, usually induced by subatomic particles a, change the energy states or number of nucleons of nuclides.
a
A B
bAfter bombarded by a, the nuclide A emits a subatomic particle b, and changes into B.
a + A B + b
or written as A (a,b) B
A (a,b) B
Describe nuclear reactions
Subatomic Particles for and from Nuclear Reactions
Subatomic particles used to bombard or emitted in nuclear reactions:
photons electrons
p or 1H protonsn neutrons
d or 2D deuteronst or 3T tritons or 4He alpha particles
nE atomic nuclei
Endothermic reactions require energy.
exothermic reactions release energy.
Potential Energy of Nuclear
Reactions
The Potential Energy of a Positively ChargedParticle as it Approaches a Nucleus.
Potential Energy
Coulombbarrier
Chargedparticle a
Nucleus, A
Neutron
Explain interaction of particle with nuclei
Estimate Energy in Nuclear Reactions
The energy Q in a reaction A (a, b) B is evaluated according to
ma + mA = mb + mB + Q,
where mi means mass of i etc
Q = ma + mA - (mb + mB) (difference in mass before and after the reaction)
The Q is positive for exothermic (energy releasing at the expense of mass) or negative for endothermic (requiring energy) reactions.
For endothermic reactions, the energy can be supplied in the form of kinetic energy of the incident particle. Energy appear as kinetic energy of the products in exothermic reactions.
Endothermic and Exothermic Reactions
These two examples illustrate endothermic and exothermic reactions.
Example: Energy for the reaction
14N + 4He 17O + 1H + Q 14.00307 + 4.00260 = 16.99914 + 1.007825 + QQ = 14.00307 + 4.00260 – (16.99914 + 1.007825) = – 0.001295 amu = – 1.21 MeVendothermic, kinetic energy of must be greater than 1.21 MeV
Example: The energy Q for the reaction 11B(, n) 14N, given masses: 11B, 11.00931; n, 1.0086649.
Q = 11.00931 + 4.00260 - (1.0086649 + 14.00307) = 0.000175 amu = 0.163 MeVexothermic reaction
Nuclear Reaction Experiments
A Setup for Nuclear Reactions
Shield Target
Particlesource
oraccelerator
Data collection and analysis system
Detectors
Basic Components
particle sourcetargetshielddetectorsdata collectiondata analysis system
Neutron Sources for Nuclear Reactions
Neutrons are the most important subatomic particles for inducing nuclear reactions. These sources are:
Neutrons from induced nuclear reactions
Neutrons from -photon excitations
Neutrons from nuclear reactions induced by accelerated particles
Neutrons from spontaneous and n-induced fission reactions (nuclear reactors)
Know how to get neutrons
Neutrons from Induced Reactions
Mixtures used as neutron sources
Source Reaction n energy / MeV
Ra & Be 9Be(, n)12C up to 13Po & Be 9Be(, n)12C up to 11Pu & B 11B(, n)14N up to 6Ra & Al 27Al (, n)31P
The discovery of neutron by James Chadwick in 1932 by reaction
9Be (, n) 12C,
was applied to supply neutrons for nuclear reactions by mixing -emitting nuclides with Be and other light nuclides.
Neutrons by Excitation
High-energy photons excites light nuclides to release neutrons. To avoid - and -ray excitation, radioactive materials are separated from these light nuclides in these two-component neutron sources to supply low energy neutrons for nuclear reactions.
Two-component neutron sources
Source Reaction n energy / MeV
226Ra, Be 9Be(, n)12C 0.6226Ra, D2O 2D(, n)1H 0.1
24Na, Be 9Be(, n)8Be 0.824Na, H 2D(, n)1H 0.2
Neutrons from Accelerators and Reactors
Neutrons are produced from nuclear reaction using energetic particles from accelerators.
2D (d, n) 3He
3T (d, n) 4He
Neutrons from nuclear fission reactions
252Cf spontaneous fission to yield 3 or more neutrons
235U and 239 Pu induced fission reactions release 2 to 3 neutrons in each fission
Neutron Induced Radioactivity
Using neutrons from the reaction, 27Al (, n)31P, Fermi’s group in Italy soon discovered these reactions:
19F (n, ) 16N 27Al (n, ) 24Na ( , ) 24Mg.
They soon learned that almost all elements became radioactive after the irradiation by neutrons, in particular
10B (n, ) 7Li releasing 2.3-2.8 MeV energy
is used in classical neutron detectors. Now, detectors use,
3He (n, p) 3H
Application of neutrons
Nuclear Reactions Induced by Cosmic Rays
Cosmic rays consist of mainly high energy protons, and they interact with atmospheres to produce neutrons, protons, alpha particles and other subatomic particles.
One particular reaction is the production of 14C,
14N(n, p)14C - emitting, half-life 5730 y
Ordinary carbon active in exchange with CO2 are radioactive with 15 disintegration per minute per gram of C.
Applying decay kinetics led to the 14C-dating method.
Simple Theories on Nuclear Reactions
Theories on nuclear reactions involve theory of nuclei, collision theory, and high-energy particles etc.We can only talk about some simple concepts of nuclear reactions.
Energy Consideration of Nuclear Reactions
Cross Sections of Nuclear Reactions
Rate of Nuclear Reactions
Types of Nuclear reactions
Give an overall look at n.r.
Nuclear Reaction Cross Sections
Cross Section of the Target andthe Random Target Shooting
(Don’t be too serious about the crossection)
Cross section with unit barn (1 b=1e-28 m2) comes from target area consideration, but it is a parameter () indicating the probability leading to a reaction,
rate = N I
(number per unit time)
N is the number of target nuclei per unit area; I is the beam intensity Differentiate the concept and reality of cross section
Cross Sections and Rate
A large copper (65Cu) foil with a surface density of 0.01g cm-2 is irradiated with a fast neutron beam with an intensity 2.0e10 n s-1 cm-2. A total width of the beam is 0.5 cm-2. After irradiation for 1 min, a total of 6.0e7 64Cu has been formed. Estimate the cross section for the reaction, 65Cu (n, 2n) 64Cu. Ignore the (t1/2 12.7 h) 64Cu nuclei decayed during the irradiation.
Solution: ( rate = N I )
rate = 6e7/60 =1e6 64Cu s-1.N = 6.022e23*0.01 cm-2*0.5 cm2/ 65 = 9.26e19 65Cu.1e6 s-1 = * 9.26e19 * 2.0e10 s-1 cm-2
= 1.08e-24 cm2 = 1.08 b
The cross section is 1.08 b for 65Cu (n, 2n) reaction.
Cross Sections and Rate
Theories of
The cross section for neutron capture of cobalt is 17 b. Estimate the rate of nuclear reaction when 1.0 g of 59Co is irradiated by neutrons with an intensity of 1.0e15 n s-1 cm-2 in a reactor.
Solution:In a nuclear reactor, the entire sample is bathed in the neutron flux.
N = 6.022e23 *1.0 / 59 = 1.02e22 59Co rate = N I = 17e-24 * 1.02e22 * 1.0e15 = 1.74e14 60Co s-1
Estimate the radioactivity of 60Co, half life = 5.27 y.
Energy Dependence of Cross SectionA Typical Variation of Neutron Cross
Section against the Energy of Neutrons.
Crosssection
Energy of n
Cross sections depend on the nuclide, the reaction, and energy.
The neutron capture cross sections usually decrease as energy of the neutron increase.
The sharp increases are due to resonance absorption.
Theories of
Cross Sections of Multi-reaction Modes
Cross Section of Multiple Reaction Modes
Crosssection
particle energy
for209Bi(, n)212At
for209Bi(, 2n)211At
Fragmentation
Reactions of 4He and 209Bi serve as an example of multiple reaction modes.
The variation of partial s as functions of energy of 4He is shown to illustrate the point.
total = i
for total consumption of nuclei.
Nuclear Fusion Cross Sections
Cross sections data from reactions studied using particles from cyclotron
7Li (p, n) 7Be3T (p, n) 3He1H (t, n) 3He2D (d, n) 3He2D (t, n) 4He3T (d, n) 4He
Effective Cross Section (mb) of Fusion Reactions
0.1
1.
10
100
1000
10000
10 20 30 40 50 60 60
D + T 4He + n
D + D 3T + p
D + D 3He + n
D + 3He 4He + p
keV
Types of Nuclear Reactions
Theories of
Elastic scattering (n, n) no energy transfer
Inelastic scattering (n, n) energy transferred
Capture reactions (n, )
Photon excitation (, )
Rearrangement reactions (n, x)
Fission reactions
Fusion reactions
Elastic and Inelastic Scattering
When the incident and emitted particles are the same, the process is scattering. If energy is transferred between the particle and the target nuclei the process is inelastic, otherwise, elastic.
Elastic scattering example: 208Pb (n, n) 208Pb, but the two n’s may not be the same particle
Inelastic scattering examples: 40Ca () 40mCa excitation
208Pb (12C, 12mC) 208mPb mutual excitation
Types of
Capture Reactions
The incident particle is retained by target nuclei in capture reactions. Prompt and delayed emission usually follow.
197Au79 (p, ) 198Hg80
238U (n, ) 239U2D (n, ) 3T9Be (n, ) 10Be12C (n, ) 13C14N (n, ) 15N
Types of
Rearrangement Nuclear Reactions
After absorption of a particle, a nuclide rearranges its nucleons resulting in emitting another particle. For example:
197Au (p, d) 196mAu4He (4He, p) 7Li27Al (4He, n) 30P54Fe (4He, 2 n) 56Ni54Fe (4He, d) 58Co54Fe (32S, 28Si) 58Ni
Particles or nuclides
Some Nuclear
Reactions
Transformation of Nuclides in Nuclear Reactions
(3He, 2n)(, 3n)
(3He, n),(d, ), (, 2n)
(3He, )(, n), (t, ) (, )
(p, n)(d, 2n)
(p, ), (n, )(3t, 2n), (d, n)(3He, d)(, t)
(d, )(3t, n)(3He, p)(, d)
(3t, )
(, p)
(, n)(n, 2n)(p, d)(3He, )
OriginalNuclideScattering,
elastic & inelastic
(n, )(d, p)(3t, d)(3He, 2p)(, 3He)
(3t, p)(, 2p)
(, d)(n, 3t)(d, )
(, p)(3t, )
(n, p)(d, 2p)(3He, 3p)
(3t, 2p)(, 3p)
No. of neutrons
No. of protons
Types of
Nuclear Fission and Fusion
A nuclide splits into two pieces with the emission of some neutrons is nuclear fission. Nuclides such as 254Fm undergo spontaneous fission, whereas neutrons induce 238U and 239Pu fission.
Fusion on the other hand combines two light nuclides into one, and may also be accompanied by the emission of one or more nucleons. An important fusion is
2D + 3T 4He + n
Applications of Nuclear Reactions
Applications of
Based on nuclide productions:
synthesis of radioactive nuclides - for various applications
synthesis of missing elements Tc, Pm and At
synthesis of transuranium (93-102) elements
synthesis of transactinide (103 and higher) elements
Activation analyses
non-destructive methods to determine types and amounts of elements
Syntheses of Radioactive Isotopes
Over 1300 radioactive nuclides have been made by nuclear reactions. The most well known is the production of 60Co, by neutron capture,
59Co (100%) (n, ) 60mCo and 60Co - and emission t1/2 = 5.24 y
The sodium isotope for study of Na transport and hypertension is produced by
23Na (n, ) 24Na ( emission, t1/2 = 15 h)
For radioimmunoassay, 131I is prepared by
127I (n, ) 128I ( EC, t1/2 = 25 m)
There are many other production methods.
Applications of
Syntheses of Tc, Pm, and At
In 1937, Perrier and Segré synthesized the missing element 43 using deuteron from cyclotron,
96Mo + 2D 97Tc + n, (Tc, EC, t1/2 = 2.6e6 y)
In 1940, Segré and Mackenzie synthesized and named element 85 astatine ( Greek astatos - unstable) At by the reaction,
209Bi83 (, xn) (213-x)At85, (x = 1, 2, 3 etc)
The missing element promethium was made by
144Sm62 (n, ) 145Sm ( , EC) 145Pm61 (EC, t1/2 = 17.7 y)
Many more isotopes of these elements have been made.
Applications of
Syntheses of Transuranium Elements
From 1940 to 1962, about 11 radioactive transuranium elements (almost 100 nuclides) have been synthesized, about one every two years. Representative isotopes of the 11 elements are neptunium (Np93), plutonium (Pu94), americium (Am95), curium (Cm96), berklium (Bk97), californium (Cf98), einsteinium (Es99), fermium (Fm100), mendelevium (Md101), nobelium (No102), and lawrencium (Lw103).
La57 , Ce, Pr59, Nd, Pm61, Sm, Eu63 , Gd, Tb65 , Dy, Ho67, Er, Tm69, Yb, Lu71
Ac89, Th, Pa91, U92, Np93 , Pu , Am95, Cm, Bk97, Cf, Es99, Fm, Md, No, Lw103
Among these, tons of 239Np, and its decay products 239Pu have been made for weapon and reactor fuel. Successive neutron capture reactions are major methods, but accelerators are involved. . . continue =>
Applications of
Syntheses of Transuranium Elements -continue
Applications of
Very heavy elements are synthesized using accelerated nuclides,
246Cm + 12C 254No102 + 4 n,
252Cf + 10B 247Lw103 + 5 n,
252Cf + 11B 247Lw103 + 6 n.
These syntheses completed the analogous of rare-earth elements. These elements were made during the cold war, and results from the former USSR were not available to us.
Syntheses of Transactinide Elements
Elements with Z > 103 are transactinides. Some results from both the USA and the former USSR are known, and some of the syntheses are given here.
242Pu (22Ne, 4n) 260Rf104 rutherfordium249Cf98 (12C6, 4n) 257Rf104
249Cf (15N, 4n) 260Ha105 hahnium249Cf (18O, 4n) 263Sg106 seaborgium
268Mt109 ( , ) 264Ns107 nielsbohrium209Bi (55Mn, n) 263Hs108 hassium208Pb (58Fe, n) 265Hs108
272E111 ( , ) 268Mt109 meitnerium208Pb (64Ni, n) 271Uun110 ununnilium
209Bi (64Ni, n) 272Uuu111 unununium
Applications of
Neutron Activation Analyses (NAA)
Applications of
Since most elements capture neutrons and produce radioactive isotopes, these reactions made them detectable.
After emission, the daughter nuclides usually emit rays. Each nuclide has a unique -ray spectra. Presence of their spectra after irradiation implies their being in the sample, and Intensities of certain peaks enable their amounts to be determined.
NAA has many applications, and these will be discussed in Chapter 12.
Neutron Activation Analyses (NAA)
Applications of
ParticlegunDetectors
NAA can be applied to explore planets and satellites and other objects in space.
Summary
Discovery of nuclear rreactions (n.r.).
Energy in n.r.
Neutron induced nuclear reactions
Simple theories or concepts related to n.r.
Types of n.r.
Applications of n.r.
