The highest energy in the electromagnetic spectrum is occupied by the gamma-rays, (γ-rays). For the betterment of mankind, γ-rays have immense applications as non-destructive evaluation tool in various fields, such as radiological diagnostics, security screening and research. However, an exposure of γ-rays to living tissues has adverse health effects, especially when the exposure time is long and intensity is high. In this regard, the biggest concern for the scientific community in radiation protection is the safety of the nuclear reactors, which are always at the risk of accidental-leakage of γ-rays. Under such circumstances, there is always a need to minimize the exposure of γ-rays originated from critical sites such as nuclear establishments and nuclear-waste disposal sites. This can be achieved by using effective γ-ray shielding enclosures at these sites. The term shield refers to the radiation attenuating material placed around radioactive source to stop or minimize the leakage of ionizing-radiations to its immediate surroundings. For γ-ray shielding purpose, any material with sufficient thickness can be used to attenuate the intensity of the rays. However, the choice of an appropriate material is necessary for effective shielding. Mostly, high-Z (atomic-number) and high-density materials such as lead and its alloys have been recommended to use for shielding purpose. Besides, the high-cost, toxicity and non-availability in huge quantities has put some constraints on the excessive use of high-Z materials as γ-ray protective shields. If space is not a constraint, then in addition to high-Z materials, commonly available low-Z building-materials can be used for the cost effective shielding purpose. The low-Z building-materials are non-toxic, low cost, inexpensive and easily available in abundance.
Table of Contents
CHAPTER 1
LITERATURE REVIEW
1.1 INTRODUCTION
1.2 TYPES OF RADIATIONS
1.3 SOURCES OF RADIATIONS
1.4 RADIOACTIVITY
1.4.1 Natural Radioactivity
1.4.2 Radiation Protection and Dose Quantities
1.4.2.1 Exposure of Radiations.
1.4.2.2 Radiation Dose.
1.4.2.3 Absorbed dose (DR, Gy).
1.4.2.4 Organ absorbed dose, (DT, Gy).
1.4.2.5 Equivalent-dose (HR, Gy).
1.4.2.6 Effective dose (E).
1.4.2.7 Fluence (Φ, m-2).
1.4.2.8 ICRU-sphere.
1.4.2.9 Ambient dose equivalent, (H.10, Sv).
1.5 RADIATION EXPOSURE RISK
1.5.1 Effects of Ionizing Radiations on Health
1.6 APPLICATIONS OF IONIZING RADIATIONS
1.7 RADIATION PROTECTION organizations
1.8 INTERACTIONS OF GAMMA-RAYS WITH MATTER
1.8.1 Interaction Mechanisms of γ-ray with Matter
1.8.1.1 Photoelectric-absorption.
1.8.1.2 Compton-scattering
1.8.1.3 Pair-production.
1.8.1.4 Triplet production.
1.9 RADIATION SHIELDING
1.9.1 Characterization of the Source
1.9.2 Characterization of Shielding-material.
1.9.2.1 Linear Attenuation Coefficient
1.9.2.2 Total Mass Attenuation Coefficient
1.9.2.3 Total Interaction Cross-Section.
1.9.2.4 Mass Energy Absorption Coefficient.
1.9.2.5 Effective and Equivalent atomic-numbers.
1.9.2.6 Electron Density.
1.9.2.7 Mean Free Path and Optical-Thickness
1.9.2.8 Half Value Layer (HVL).
1.9.2.9 KERMA.
1.9.2.10 Buildup Factor (BUF).
1.9.2.11 Double Layered Transmission Exposure Buildup Factor.
1.9.3 Dose Calculations by the Point-kernel Method.
1.9.3.1 Fluence-to-dose Conversion.
1.9.3.2 Calculation of uncollided-radiation dose.
1.9.3.3 Calculation of total dose.
1.10 THE LITERATURE REVIEW
1.10.1 Mass Attenuation Coefficient (μm)
1.10.2 Mass Energy Absorption Coefficient (μen/ ρ).
1.10.3 Atomic-Numbers (Zeq & Zeff).
1.10.4 Buildup Factor for Homogenous Shield.
1.10.5 Buildup Factor for Heterogeneous Shield
1.11 Importance of the study.
CHAPTER 2
EXPERIMENTAL TECHNIQUES.
2.1 INTRODUCTION.
2.2 INSTRUMENTS AND TECHNIQUES.
2.2.1 X-Ray Techniques
2.2.1.1 Wavelength Dispersive X-Ray Fluorescence (WDXRF).
2.2.1.2 X-Ray Diffractometer (XRD-R).
2.2.2 Free Swell Ratio (FSR) Test.
2.2.3 Standard Radioactive Sources
2.2.4 Gamma-Ray Spectrometry
2.2.4.1 Gamma-Ray Spectrometer
2.2.4.2 Scintillation Detector.
2.2.4.3 Photo Multiplier Tube (PMT).
2.2.4.4 Pre-Amplifier.
2.2.4.5 Linear Amplifier.
2.2.4.6 Regulated High Voltage Power Supply.
2.2.4.7 Multi-Channel Analyzer (MCA).
2.2.4.8 Lead Collimators and Lead-Alloy Blocks.
2.2.5 Miscellaneous Instruments
2.2.5.1 Pocket Radiation Monitor.
2.2.5.2 Electronic Balance.
2.2.5.3 Digital Vernier Calipers.
2.2.5.4 Radiation Laboratory.
2.3 SAMPLE PREPARATION
2.3.1 Sample Preparation for WDXRF.
2.4.2 Sample Preparation for XRD-R.
2.3.3 Sample Preparation for Gamma-Ray Spectroscopy.
2.3.3.1 Procedure for making of sample-bricks.
2.4 COMPUTER SOFTWARES
2.4.1 WinXCom.
2.4.2 MAESTRO
2.4.3 MAUD
2.4.4 ORIGIN
2.4.5 GEANT4 Toolkit.
CHAPTER 3
COMPUTER PROGRAMS (TOOLKITS).
3.1 INTRODUCTION.
3.2 NEED OF TOOLKITS
3.2.1 GRIC-Toolkit.
3.2.2 GRIC2-Toolkit.
3.2.3 BUF-Toolkit.
3.2.3.1 Corrections for overestimations.
3.3 FORMULATIONS OF TOOLKITS.
3.3.1.1 Mass attenuation coefficient, μm (cm2g-1).
3.3.1.2 Mass energy absorption coefficient, .
3.3.1.3 KERMA relative to air (KR).
3.3.1.4 Equivalent atomic-number (Zeq).
3.3.2 Formulation of GRIC2-toolkit.
3.3.2.1 Photon interaction
3.3.2.2 Mass attenuation coefficient of a mixture.
3.3.2.3 HVL and TVL.
3.3.2.4 Effective atomic-number (Zeff).
3.3.2.5 Effective electron density, Nel,eff (electrons/g).
3.3.3 Formulation of BUF-Toolkit
3.3.3.1 BUF for SLHS.
3.3.3.2 EBF for DLHS.
3.4 VALIDATIONS OF THE TOOLKITS
3.4.1 Validations of GRIC-toolkit
3.4.2 Validations of GRIC2-toolkit
3.4.3 Validations of BUF-toolkit.
3.5 EXAMPLE: NBS-Concrete
3.6 CONCLUSIONS.
CHAPTER 4
BUILDUP FACTORS FOR HOMOGENEOUS AND HETEROGENEOUS GAMMA-RAY SHIELDS
4.1 INTRODUCTION.
4.2 OBJECTIVES
4.3 THEORY.
4.4 GEOMETRY.
4.4.1 Homogeneous Infinite Medium Spherical Shield
4.4.2 Heterogeneous Finite Media Spherical Shield
4.4.2.1 Significance of the DLEBF.
4.5 MATERIAL AND METHODS
4.5.1 Samples.
4.5.2 Methodology.
4.5.2.1 Computations.
4.6 RESULTS AND DISCUSSION
4.7 CONCLUSIONS.
Research Objectives & Key Themes
This work aims to enhance radiation shielding safety for residential buildings in the event of nuclear accidents by evaluating the gamma-ray shielding behaviors (GSB) of various low-Z engineering materials. A primary goal is to address the lack of buildup factor information for finite heterogeneous shields by developing specialized computer toolkits to compute these parameters, thereby enabling more accurate radiation dose estimations for stratified shielding configurations.
- Analysis of gamma-ray interaction mechanisms (Photoelectric, Compton, Pair, and Triplet production).
- Development of computational toolkits (GRIC, GRIC2, BUF) for shielding analysis.
- Characterization of common building materials (concrete, clay, limestone, etc.) for shielding efficacy.
- Validation of the proposed computational models using standard reference data and Monte Carlo simulations.
- Investigation of Double Layered-Heterogeneous-Shields (DLHS) and optimal layer orientation.
Excerpt from the Book
1.1 INTRODUCTION
Gamma-rays are the most energetic electromagnetic radiations which are emitted from the radioactive nuclei. Being ionizing in nature, gamma (γ) -rays have beneficial as well as adverse biological consequences. The human race was unaware of the existence of γ-rays until 1896, when Henri Becquerel demonstrated some new kind of radiations being emitted from uranium ore that could affect photographic plates. Around the turn of the 19th century, these nuclear radiations were named as alpha (α), beta (β) and gamma (γ) rays. In general the emission of γ-ray follows the α and β emissions. Alpha and beta decay of unstable parent nuclei leave the daughter nuclei in the excited states. These excited nuclei in turn make transitions to their ground states by emitting γ-ray photons.
The discovery of γ-rays had an enormous impact right from the beginning and changed the world drastically. This discovery contributed not only in the progress of nuclear physics, but also advanced medical science to new heights. Gamma-rays were soon perceived to present health hazards resulting from damage to the living cells. The discovery of nuclear fission in 1938, based on Einstein’s mass energy relation, caused the birth of an atomic bomb. In 1945, explosions of two such bombs at Hiroshima and Nagasaki in Japan had started the race between different countries in the manufacturing of nuclear weapons. The fallout of various nuclear test explosions executed by various countries created worldwide atmospheric radioactive pollution.
Summary of Chapters
CHAPTER 1: Provides a comprehensive literature review on gamma-ray interactions, radiation safety, shielding parameters, and historical advancements in buildup factor studies.
CHAPTER 2: Details the experimental techniques used, including X-ray fluorescence, diffraction, and gamma-ray spectrometry, alongside the materials tested.
CHAPTER 3: Describes the design, formulation, and validation of the three self-developed computer programs (toolkits) for shielding parameter calculations.
CHAPTER 4: Focuses on the analysis of buildup factors for both homogeneous and heterogeneous shields, demonstrating the utility of Double Layered-Heterogeneous-Shields.
Keywords
Gamma-rays, radiation shielding, buildup factor, heterogeneous shield, effective atomic-number, mass attenuation coefficient, EGS4-code, dose estimation, ionizing radiation, material science, nuclear safety, computational toolkit.
Frequently Asked Questions
What is the primary focus of this work?
The book focuses on characterizing the gamma-ray shielding behaviors of common, low-cost building materials to improve residential radiation safety during potential nuclear accidents.
What are the central themes discussed in the book?
The themes include interaction mechanisms of gamma radiation with matter, methods for shielding parameter characterization, and the development of computational toolkits for analyzing both homogeneous and heterogeneous shields.
What is the main research objective?
The objective is to compute double-layered transmission exposure buildup factors (DLEBF) for various stratified shield combinations and determine the most effective orientation of materials to minimize radiation exposure.
Which computational methods are utilized in the study?
The study utilizes geometric progression (G-P) fitting methods and self-designed spreadsheet toolkits (GRIC, GRIC2, BUF) validated against standard reference data and Monte Carlo simulations.
What is covered in the main body of the work?
The body covers theoretical interactions (photoelectric, Compton, etc.), experimental characterization of materials, the design of custom software tools, and detailed shielding analysis for stratified shield configurations.
Which specific materials are analyzed?
Common, low-Z building materials such as concrete (NBS-Concrete), aluminum, water, clay, and limestone are investigated for their efficacy as protective shields.
How do the self-designed toolkits improve upon existing standards?
The toolkits consolidate the computation of various required parameters (like Zeff, KERMA, and BUFs) into a single user-friendly platform, overcoming the limitations of previous fragmented or aging standards.
What is the significance of the "double-layered" shield configuration?
A double-layered shield allows for an optimized design using both low-Z and high-Z materials, which can provide better radiation attenuation and cost-effectiveness compared to single-layer shields.
- Citar trabajo
- Kulwinder Singh Mann (Autor), 2016, Shielding Behaviour Analysis of Double Layered Slabs. Gamma Ray Shielding, Múnich, GRIN Verlag, https://www.grin.com/document/437837
