TYPES OF RADIATION/INTERACTION WITH MATTER/RADIATION DETECTORSGirish kumar PalvaiWebsite: www.conceptualphysicstoday.comEmail: firstname.lastname@example.org
Topics under Discussion What is Radiation? Types of Radiation? Interaction of radiation with matter. Why Radiation Detection? Types of Radiation detectors Radiation Detectors in ECIL Radiation --- harmful to mankind?
Radiation could be referred to as flux of energeticparticles emanating from Nuclei /atomic events.The word radiation in the present world covers both highenergy photons and energetic subatomic particles suchas electrons, protons, -particles, fission products etc.
Process of emission of energeticsubatomic/Nuclei particles due to changein state of certain atoms/nuclei. Such nucleiare called unstable nuclides.This phenomenon is called Radioactivity.
Types of Radiations Photons ParticlesElectromagnetic wavesX-rays gamma-rays Electron Ions Neutron -ray Proton, -rays EBCommonly used Heavy ionsradiation sources
Cosmic Shower ~109-1021 eV (~ 6 GeV) (~ km) (100mb) 2 x 1018 particles (mainly protons) / s enter the atmosphere (ISOTROPIC) Upto ~100• Interact with atmospheric nuclei MeV & produce secondary particles (muons, electrons, photons, neutrons: responsible for cosmic dose) Flux % H 1300 92.9 He 88 6.3 >He 10.7 1.06
Interaction of Gamma Photons with matterPhotoelectric effect:The kinetic energy Ee of thephotoelectron is given by E e= hν–E b hνThe cross section for photoelectricabsorption depends on the atomic Eenumber (Z) of the absorber andenergy of the photon Eγ σPE α Z4.5 / Eγ3 13
Compton scatteringThe scattered photon energy is given by E Esc E 1 1 - cos m0 c 2The cross section for Compton scattering is hν e θ σ cs α Z / Eγ hν’ 14
Pair ProductionThe excess energy above 1.02 MeV is shared between the positronand electron as kinetic energy, which are later slowed down in thestopping medium. Eγ= e- + e+ + Ee- + Ee+The cross section for pair production varies with Z of the absorberand Energy of the photon as, σ pp α Z2 ln Eγ 15
Relative Importance of Three Major Interaction Mechanisms 16
Interaction of Neutrons with matter• Charged particle emission (Slow neutrons)• Elastic scattering collision (Fast neutrons)• In elastic scattering collision (Fast Neutrons)
Fast Neutron InteractionIn- Elastic scattering: - Excited Compound Nucleus Emitted Neutron Incident Neutron Gamma Ray Target nucleus
Elastic scatter:• The neutron and the nuclide collide and share a part of their kinetic energies. They rebound with speeds different from the original speeds, such that the total kinetic energy before and after the collision remains the same. If the nucleus is stationary before collision, it will gain energy from the neutron and start moving, and the neutron gets slowed down due to loss of kinetic energy. However, the residual nucleus is not excited but is in its ground state.• The most important process for slowing down of neutrons.• Total kinetic energy is conserved• E lost by the neutron is transferred to the recoiling particle.• Maximum energy transfer occurs with a head-on collision.
Non elastic scatter• Differs from inelastic scattering in that a secondary particle that is not a neutron is emitted after the capture of the initial neutron. eg: 12C ( n, α ) 9Be ; Egamma = 1.75 MeV• Energy is transferred to the alpha particle and the de excitation gamma ray.
Neutron capture• Same as non elastic scatter, but by definition, neutron capture occurs only at low neutron energies (thermal energy range is < 0.025 eV).• Capture leads to the disappearance of the neutron.• Neutron capture accounts for a significant fraction of the energy transferred to tissue by neutrons in the low energy ranges. eg: 1H ( n, gamma ) 2H ; Egamma = 2.2 MeVSpallation• In this process, after the neutron is captured, the nucleus fragments into several parts. Only important at neutron energies in excess on 100 MeV. (cross sections are higher at 400-500 MeV).
Why to detect Radiation? &How to detect Radiation
Why to detect Radiation?• Environmental safety• Personal protection of occupational workers• Calibration of radioactive isotopes• Power regulation in nuclear reactors• Research applications• Estimation of radiation dose in treatment of patients and more…………….
How to detect Radiation?Choose a radiation detector working on a particularprinciple of interaction (ionization/scintillation/etc)with known sensitivity to estimate the radiation underdetection.
Some Characteristics of Radiation Detectors• Sensitivity• Operating voltage• Operating voltage region• Radiation detection range• Resolution (for pulse based)• Less dead time• Life time
TYPES OF RADIATION DETECTORS Gas Flow Scintillation Semi-Conductor Detectors Gas Filled Detectors Detectors Radiation DetectorsAlpha Beta Gamma Neutron Other ParticlesDetectors Detectors Detectors Detectors & Energy GM Radiation
GAS FILLED DETECTORSGamma Ion Chamber Gamma Ion Chamber B10F3 filled counter.Criticality Alarm Systems Area Monitoring He3 filled counter. Neutron MonitoringFission Detector with MI Fission Detector with MI Neutron Monitoringcable for Source Range Self Powered Neutron Detector cable for IntermediateMonitoring ( BWR) Range Monitoring( BWR) Gamma Compensated neutron Ion chamber Uncompensated Neutron Ion Chamber with MI cable for Power Range Monitoring in PHWRs
B10 Lined Proportional Counters Application: Used normally for physical or normal start-up of Reactors. Sensitivity From 0.8 to 20 CPS/nV 4 CPS/nV detectors are supplied regularly to NPCIL for Reactor Start-up Enriched Boron (96% enriched amorphous fine powder) is the main constituent. 10B + 0n1 (5B11) (3Li7 )+++ + (2He4 )++ + 2.34 Mev
B10 Coated Ion chambers Supplied regularly to NPCIL for Reactor Power Measurement in Intermediate and Power Range Sensitivity: Neutron: 10-14 Amps/nv, Gamma: 10-11 Amps/R/hr (Un Compensated) 10-12 Amps/R/hr (Compensated)
B10 coated Ion chamber with integral MI cable assembly Boron-10 coated chamber with integral MI cable assembly Neutron Sensitivity: 1x10-14 Amps/nv Gamma Sensitivity: 2.5 x10-12 Amps/R/h Range: 104 to 1011 nv Operating Voltage: 600 V Operating Temperature: 100 deg C Dimensions: 88 mm dia, 330 mm length,
10BF Gas Filled Detectors 3 Sensitivity from 4 to 150 CPS/nv 25 CPS/nv detectors are supplied regularly to NPCIL, BARC for DNM and other systems Enriched Boron Complex (B10 F3 CaF2 ).. 90% enriched powder) is the main conversion material to generate BF3 Gas by thermal decomposition. B10 F3 CaF2 complex currently produced by HWB Generation and purification system is made by ECIL
He3 Detectors Sensitivity from 10 to 250 CPS/nv Applications: SNM detection systems, research applications etc. Supplied to IGCAR, BARC for Neutron well counters and other applications
Fission Detectors• HEU based SRM, IRM, LPRM, Wide Range Sensitivity From 10-3 to 1 CPS/nv, With & Without integral MI Cable Supplied to BWR, FBTR• LEU (<20% Enrichment) based Sensitivity From 10-3 to 0.18 CPS/nv, With & Without integral MI Cable Supplied to BARC, PHWR High Temperature (650o C) Fission Counter for PFBR
FD for Source Range MonitorUsed for incore flux monitoring in BWRs. Pulse mode operationU-235 (90% enriched) coated counter with integral MI cable assembly Sensitivity: 10-3 CPS/nv Range: 104 to 109 nv Operating Voltage: 350 V Operating Temperature: 300 deg C Dimensions: 6 mm dia, 75 mm length, sensitive length: 25 mm
Local Power Range Monitor U-235 (90% enriched) coated chamber with integral MI cable assembly Neutron Sensitivity: 1x10-17 Amps/nv Range: 1011 to 1013 nv Gamma Sensitivity: Less than 5x10-14 Amps/R/h Operating Voltage: 100 V Operating Temperature: 300 deg C Dimensions: 6 mm dia, 75 mm length, sensitive length: 25 mm
Self Powered Neutron Detectors Sensitivity: 10-22 Amps/nv Operating temperature: Up to 3000C Emitter: Cobalt, Vanadium, Platinum Supplied regularly to NPCIL for Incore Flux Mapping Fabricated with Integral MI Cable Tested for hydrostatic pressure of 250 kg/cm2
SPND with COBALT EMITTERSPND with VANADIUM EMITTER
Applications of Radiation Technology Crosslinking of polymers Degradation of high molecular weight materials Curing of polymer coatings Graft polymerization Sterilization of medical products Food irradiation Sewage Sludge Hygienization