Neutron Radiation And Its Impact In Medical Physics

Description

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWELDGEMENT

ABSTRACT

CHAPTER ONE

INTRODUCTION

1.1    BACKGROUND OF THE PROJECT

• PROBLEM STATEMENT
• AIM AND OBJECTIVE OF THE STUDY
• SCOPE OF THE STUDY
• LIMITATION OF THE STUDY
• SIGNIFICANCE OF THE STUDY
• RESEARCH QUESTIONS
• DEFINITION OF TERMS

CHAPTER TWO

LITERATURE REVIEW

• OVERVIEW OF NEUTRON RADIATION
• RADIATION BASICS
• IONIZATION MECHANISMS AND PROPERTIES
• REVIEW OF NEUTRON RADIATION EXPOSURE

CHAPTER THREE

• SOURCES OF NEUTRON RADIATION
• USES OF NEUTRON RADIATION
• NEUTRON RADIATION: HEALTH HAZARDS AND PROTECTION
• EFFECTS NEUTRON RADIATION ON MATERIALS
• CONCLUSION
• RECOMMENDATION

REFERENCES

CHAPTER ONE

1.0                                                        INTRODUCTION
1.1                                           BACKGROUND OF THE STUDY

Neutron radiation is a form of ionizing radiation that presents as free neutrons. Typical phenomena are nuclear fission or nuclear fusion causing the release of free neutrons, which then react with nuclei of other atoms to form new isotopes—which, in turn, may trigger further neutron radiation. Free neutrons are unstable, decaying into a proton, an electron, plus an anti-electron-neutrino with a mean lifetime of 887 seconds (14 minutes, 47 seconds)(Yue et al, 2013).

Neutrons may be emitted from nuclear fusion or nuclear fission, or from other nuclear reactions such as radioactive decay or particle interactions with cosmic rays or within particle accelerators. Large neutron sources are rare, and usually limited to large-sized devices such as nuclear reactors or particle accelerators, including the Spallation Neutron Source.

Neutron radiation was discovered from observing an alpha particle colliding with a beryllium nucleus, which was transformed into a carbon nucleus while emitting a neutron, Be(α, n)C. The combination of an alpha particle emitter and an isotope with a large (α, n) nuclear reaction probability is still a common neutron source.

Neutron radiation is often called indirectly ionizing radiation. It does not ionize atoms in the same way that charged particles such as protons and electrons do (exciting an electron), because neutrons have no charge. However, neutron interactions are largely ionizing, for example when neutron absorption results in gamma emission and the gamma ray (photon) subsequently removes an electron from an atom, or a nucleus recoiling from a neutron interaction is ionized and causes more traditional subsequent ionization in other atoms. Because neutrons are uncharged, they are more penetrating than alpha radiation or beta radiation. In some cases they are more penetrating than gamma radiation, which is impeded in materials of high atomic number. In materials of low atomic number such as hydrogen, a low energy gamma ray may be more penetrating than a high energy neutron )(Yue et al, 2013).

The nuclear materials that are accounted for in the nuclear fuel cycle emit neutrons as well as gamma rays. For most isotopes the neutron emission rate is very low compared to the gamma-ray emission rate. For other isotopes the neutron emission rate is high enough to provide an easily measurable signal.

Neutron radiation has many effect such as biological effect. Because of their biological effects fast neutrons are most effective in treating large, slow-growing tumours which are resistant to conventional X-radiation. Patients are treated typically 3–4 times per week for 4–5 weeks (sometimes in combination with X-radiation) for a variety of conditions such as carcinomas of the head and neck, salivary gland, paranasal sinus and breast; soft tissue, bone and uterine sarcomas and malignant melanomas. It is estimated that about 27,000 patients have undergone fast neutron therapy to date )(Yue et al, 2013).

The biological effects of different radiations depend not only on the dose delivered, but also on the microscopic dose distribution which is expressed in terms of linear energy transfer (LET). Densely ionizing radiations such as neutrons, heavy ions and the light ions emitted in thermal neutron capture are high-LET radiations while photons, electrons and high-energy protons are low-LET radiations. The higher the LET, the greater the biological effect of a given type of radiation. The lower the energy of a particular radiation, the higher is its LET and therefore, its biological effect.

For a given absorbed dose, high-LET radiations are more efficient at killing cells than low-LET radiations. This is quantified in terms of the relative biological effectiveness (RBE) which is defined as the ratio of the dose of a reference radiation (usually ⁶⁰Co) required to produce a specified biological effect to the dose of the given radiation required to produce the same effect. With low-let radiations a larger proportion of cells suffer sub-lethal (repairable) damage than with high-let radiations, where the damage is largely irreparable.

One of the main rationales for high-LET therapy lies in the so-called oxygen effect [2]. Damage to DNA is done either directly by ionizing particles or indirectly by biochemical action. Low-LET radiation damage is caused mostly by indirect biochemical action while high-LET radiation damage is caused mostly by direct interaction of ionizing particles. In the indirect method the ionizing particles induce the formation of free radicals that damage the DNA. The presence of free oxygen is required to facilitate this radiation damage. In the absence of oxygen, the effects of indirect action are limited.

Because the rapidly proliferating tumour cells can reduce the blood supply to the centre of large tumours, the cells in this region can become deprived of oxygen. Cells that lack oxygen are therefore resistant to low-LET radiations (photons, protons and electrons) but are much less resistant to high-LET radiations such as neutrons which therefore have a better chance of effecting a cure.

Another important reason for using high-LET radiations concerns the cell cycle effect [4]. Cells are most sensitive to radiation in the mitotic (dividing) phase of the cell cycle. However, they are relatively tolerant in the S (DNA synthesizing) phase, and because slowly growing tumours have a larger proportion of cells in the S phase at any given time, slowly growing tumours are resistant to conventional radiations. The variation in radio-sensitivity between cells in different stages of the cell cycle is much less for fast neutrons and other high-LET radiations, which are therefore, generally used for treating large, slow-growing or radio resistant tumours.

1.2                                                  PROBLEM STATEMENT

Radiation occurs when energy is emitted by a source, then travels through a medium, such as air, until it is absorbed by matter. People use and are exposed to non-ionizing radiation sources every day. This form of radiation does not carry enough energy to ionize atoms or molecules.

Microwave ovens, global positioning systems, cellular telephones, television stations, FM and AM radio, baby monitors, cordless phones, garage-door openers and ham radios all use non-ionizing radiation. Other forms include the earth’s magnetic field and magnetic field exposure from proximity to transmission lines, household wiring and electrical appliances.

There has been a lot concern about neutron radiation exposure from medical physics, and many patients are asking about it. They want to know if neutron radiation will increase their risk of developing sickness like cancer. The study was carried out to enlighten the reader about the effects of excess dose of x-ray radiation and also provide its remedy.

1.3                                                     AIM OF THE STUDY

The main aim of this seminar is to carry out a research on neutron radiation and explaining its associated health effects. The objectives are:

1. To study neutron radiation and its different types.
2. To understand how neutron radiation occurs

• To explore the effects of neutron radiation

1.4                                                   SCOPE OF THE STUDY

The scope of this seminar covers the basics of neuron radiation and its impact in medical physics. In this seminar, neural radiation which comes from many sources including more than 60 naturally-occurring radioactive materials found in soil, water and air shall be discussed.

This seminar also discusses how radiation exposure can cause damages to the body and how it can occur internally when radionuclides enter the body through ingestion, inhalation, or the skin.

1.5                                                      SIGNIFICANCE OF THE STUDY

This seminar work will throw more light on the overview, uses, and applications of Neutron radiation. This study will also be designed to be of immense benefit to all the users and those working on Neutron radiation in that it will help them to understand the health effect of neutron radiation and how to observe safety measure. This study will also highlight the importance of using the lowest possible dose of radiation for any case. The principle of application of dose limits indicates that the dose given should never exceed the recommended dose for an individual.

1.6                                                   RESEARCH QUESTION

At the end of this seminar, answers to the following questions shall be provided:

1. What is neutron radiation?
2. What is the effect of neutron radiation?

• What is an example of neutron radiation?

1. Do neutrons cause radiation?
2. Is neutron radiation harmful?

1.7                                                  DEFINITION OF TERMS

RADIATION: Radiation is energy that travels in the form of waves or particles and is part of our everyday environment. People are exposed to radiation from cosmic rays, as well as to radioactive materials found in the soil, water, food, air and also inside the body.

NEUTRONS: Neutrons are uncharged particles that can interact easily with a positively charge atomic nucleus where various capture processes can occur.

Impact: impact is a strong effect neutron radiation have on someone