E = mc 2. Energy is Released in Fusion and Fission Reactions

Transcription

1 4 th August, 2009

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4 E = mc 2 Nuclear Fission Nuclear Fusion Energy is Released in Fusion and Fission Reactions

5 Energy release in fission is attributed to the mass defect occurring during the process Radiation n Neutron Nucleus of U MW-Day energy from 3 t of coal Compound Nucleus in an excited state of high internal energy Energy 1 MW-Day energy from 1 gm of U-235 Energy Fission Fragments 36 Kr Ba 141 Fast-n (Prompt Neutrons) 92U n 1 92U n 1 36Kr Ba ( 0 n 1 ) + Energy 42Mo La ( -1 e 0 ) + 2( 0 n 1 ) + Energy Fission product Half life 90 Sr 28.9 y Mass 'm1'= gm Mass 'm2'= gm Difference in mass Dm= gms 5 E = Dm * c 2 c, velocity of light = 3x10 8 m/s 137 Cs 30.07y 129 I 15.7E6 y 99 Tc 2.1E5 y

6 Nuclear Reactions ( like Chemical reactions) are Broadly Exoergic ( Q > O ) and Endoergic (Q<0) 2 H + 3 H = 4 He + n MeV n U = Frg1 + Frg2 + 2n +( ) MeV ( various combinations of fragment mass)

7 Images are taken from internet Requirement of coal for a 1000 MWe Coal fired plant ~ 2.6 million t / Year (i.e. 5 trains of 1400 t /Day) Requirement of natural uranium for a 1000 MWe Nuclear Power Plant: ~ 160 t /Year. REACTOR BOILER COAL, NUCLEAR GAS OR REACTION OIL IS BURNED GENERATES TO MAKE HEAT STEAM TO MAKE STEAM WHICH TURNS THE TURBINE 7 WHICH SPINS THE GENERATOR WHICH PRODUCES ELECTRICITY

8 (n, γ) 0 n U U239 + γ (Fertile) 93 Np β 0 (Fissile) 94 Pu β 0 (n, γ) 0 n Th Th233 + γ (Fertile) 91 Pa β 0 (Fissile) 92 U β 0 In-situ fissions enhance burn-up up Fuel source for other reactors (after reprocessing of spent fuel) 8

9 Isotopes of Hydrogen Protium 1 Proton + 0 neutron (stable) Deuterium (D) 1 Proton + 1 neutron (stable) Tritium (T) 1 Proton + 2 neutrons (radioactive, βactive) D-T T fusion occurs at a reasonable rate only at temperatures over 100 million K. We also need: Plasma density (n) ~ particles/ cm 3 Confinement time (τ)( ~ a few seconds A rough guide is the Lawson Criterion n x τ > 10 > sec/cm 3 with the temperature at 10 kev (1eV = 10 4 K)

10 SPALLATION REACTIONS Proton ( 1 GeV) 1 st stage: Emission of high energy particles (pions,p,n) 2 nd stage: Evaporation from highly excited nucleus (p, n, fission fragments, spallation residues.) Evaporation from Excited Nucleus Intra Nuclear Cascade Spallation Residues Fission Products

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12 Parameters suggested by U.N for calculating HDI Per Capita GDP, Life Expectancy at Birth, Adult Literacy Parameters suggested by me for calculating HDI 2 decades back Per Capita Electricity Consumption and Female Literacy 12

13 Source: International Energy Agency, World Energy Outlook 2007, reference scenario from Report prepared by an independent Commission at the request of the Director General of the International Atomic Energy Agency 2008.

14 The sun, the atmosphere, the oceans, plants, living organisms, etc. are in delicate balance and this balance determines the earth s s climate. Some of the reflected light and heat from the earth s s surface are trapped by the naturally occurring gases like water vapourm CO 2 etc. in atmosphere. These are natural greenhouse gases (GHGs( GHGs), but for which we would be freezing on earth! But the man-made made GHGs CO 2, Methane, etc. in the atmosphere make it trap more heat than we want, leading to global warming.

15 The Fourth assessment report of the Intergovernmental Panel on Climate Change(IPCC) ) concluded from direct observations of changes in temperature, sea level, and snow cover in the northern hemisphere during 1850 to the present, that the warming of the earth s s climate system is unequivocal. The global atmospheric concentration of greenhouse gases (GHG) has increased from a pre industrial value of about 280 ppm to 379 ppm in Multi model averages show that the temperature changes between relative to will range from 1.1 to 6.4 C C and sea level rise from 0.18 to 0.59 meters.

16 1 Relative Carbon Emissions Coal IGCC Natural gas Nuclear Hydro Renew

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18 Why Neutron Beams? From Research Reactors Thermal neutrons: an ideal and unique probe in condensed matter Microscopic Understanding of - Structural, - Dynamic and - Magnetic properties Wave-length close to interatomic distances Just as energetic as atoms and molecules in condensed matter study of lattice dynamics Gets deep into the samples Contrast between isotopes and neighbouring atoms in periodic table Magnetic (spin) to probe magnetism Nondestructive characterization (Radiography)

19 Maxwell Distribution of Thermal Neutrons EmeV ( ) = 81.8 λ(å) 2 Bent Perfect Crystal Monochromator

20 Scattering Lengths of Thermal Neutrons Coherent Scattering Length, b coh (10-14 m) H or D 1 H 7 Li b coh b coh X (relative abundance) 51 V 48 Ti 50 Cr 53 Cr 55 Mn 62 Ni Atomic Weight

21 Magnetic Scattering by Neutrons Magnetic Phase Transition (AFM-PM) of KMnCl 3 neutron has spin lattice with ordered spin (antiferromagnetic) 9 K 20 K 30 K 40 K 50 K 60 K 70 K 80 K 90 K 95 K 98 K 99 K 100 K 102 K 104 K 150 K 220 K theta [deg.] Magnetic Moment [Bohr magneton] T [K]

22 Neutron spectrometers inside Dhruva Reactor Hall

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24 British physicist Frederick Soddy clarified the concept of isotopes in Atoms with same atomic number [Z] and different mass number [A]. Written as Mass Number X Atomic Number Atom In nature, Uranium (Z=92) exists as U = 238 (99.284%), U-235 (0.711%) and a very small amount of U-234 (0.0058%) Unstable Isotopes are called Radioisotopes or Radionuclides. They emit α, β & γ- rays p+n e He Nucleus Electron Electromagnetic radn. Both stable and unstable isotopes are used for applications 24

25 Isotopes (both stable & radioactive) which occur in the environment in varying concentrations, over which the investigator has no control are called Environmental Isotopes. 25

26 Isotope Abundance in nature (%) Deuterium ( 2 H) Oxygen - 18 ( 18 O) Carbon - 13 ( 13 C) 1.11 Nitrogen-15 ( 15 N) Sulphur -34 ( 34 S) 4.21 These isotopes are used for identification of source & origin of groundwater and groundwater pollutants. 26

27 ISOTOPES T 1/2 (years) Energy (MeV) Abundance (%) Tritium ( 3 H) β (100) Carbon - 14 ( 14 C) 5730 β (100) Chlorine -36 ( 36 Cl) 3.1x10 5 β (98) *Cesium - 137( 137 Cs) 30 γ (100) These isotopes are used for groundwater and *sediment dating 27

28 Tritium - 3 H is produced in the atmosphere by cosmic ray neutrons reaction with nitrogen atoms. It is oxidized to water and incorporated in the rain. 14 N n 0 3 H C 6 Also it is produced by the atmospheric explosion of thermonuclear devices, operation of nuclear reactors and particle accelerators. Radiocarbon - 14 C is produced in the upper atmosphere by cosmic ray neutrons reaction with nitrogen atoms. It is oxidized to carbon dioxide and incorporated in the carbon cycle. 14 N n 0 1 H C 6 28

29 Isotope Half life 3 H y HTO 60 Co Chemical form 5.3 y K3[Co(CN)6] Applications Groundwater recharge rate and flow direction Groundwater recharge rate 82 Br 198 Au 46 Sc 36 h NH 4 Br 2.7 d HAuCl 3 84 d Scandium glass Ground water velocity, effluent dispersion Seepage entry in dams and exit points Sediment transport in marine environments 29

30 Recharge of drying springs in Himalayan region Isotopes Used : 18 O, 2 H ( identification of recharge altitude). 3 H ( groundwater residence time) Based on isotope results, artificial recharge structure were constructed at identified recharge areas for rain water harvesting. Outcome: : Enhanced & perennial spring discharge [Contd] 30

31 Application of Isotope Techniques in Hydrology for recharging of Drying Springs in Mountainous Region of Gaucher, Uttarakhand Collaborative project of BARC and Himalayan Environmental Studies and Conservation Organisation [HESCO] 10 Springs recharged. All springs have become perennial. Discharge rates increased by 5 to 9 times. 2 New springs appeared. Similar work initiated at 10 new locations in Uttarakhand, Jammu & Kashmir and Himachal Pradesh. Isotope Hydrology Centre being set up at HESCO, Dehradun to train the local people to carry out the work themselves. Before Recharge: 2 L/min 31 After Recharge: 18 L/min

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34 Static Imaging Organ size, shape, abnormalities etc. Thyroid, Liver, Kidneys, Brain, Skeleton, Lungs, malignancies Presence of nodules, tumours, metastatic lesions, goitre, abcess,, shrinkage etc. Dynamic Imaging Functioning of the organ, rate, output, defects etc. Heart, Liver, Kidneys Infarcted myocardium, hole in the heart, filtration defects in kidneys etc.

35 Lung Images of a normal healthy person vs. a long time chain smoker Scan in a patient with Pulmonary Disease

36 Positron Emission Tomography: PET Recent technology 18 F-Fuloro deoxy glucose ( 18 F-FDG) most widely used tracer for PET; mimics glucose, but gets trapped once inside the cell clear, precise 3D pictures of defects Most often used to find out recurrence of cancers; Also used to image heart and brain to find tissues that are not alive (do not take up glucose) Applications: Oncology, neurology, Cardiology & Psychiatry

37 Ionising radiations can kill living cells and organisms Historically radioisotopes have been used for therapy of cancers and a few other diseases; e.g. 131 I, 32 P Radiation as a external beam or as a source inside body are being used for treatment - Primarily Cancers and other situations like hyperthyroidism. Surge - past 15 years; Billion dollar business Gamma rays are good for external beam therapy and particles like beta and alpha rays are good for internal (in-vivo) therapy.

38 External source High intensity radiation; 60 Co most widely used A machine is used to direct the radiation to the tumor (cancer) through the skin.

39 Gamma Knife Multiple targeting (up to Co sources; 1 TBq each; circular array) to achieve better dose delivery and low damage to surrounding tissues. Useful in Brain tumors Acoustic neuroma Arteriovenous malformation (AVM) Trigeminal neuralgia High accuracy, low risk, low complications, low morbidity

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41 Radionuclides and Radiation : Aiding Better Health Care

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