Characteristics of MCP Alloys

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Characteristicsof MCP Alloys

Institution’sName

Abstract

Radiationis applied in medicine for cancer treatment. Different materialsplaced between a source and a receptor can affect the amount ofradiation transmitted from the source to the receptor. Such effectsare due to attenuation and absorption of the emitted radiation in thesource itself, of the material used for encapsulation of the source,or in a shielding barrier. The most important factors to considerbefore selecting any material for radiation shielding is its build-upfactor and attenuation coefficient. MCP alloys are now used forradiation shielding. Suchalloys have low melting points, fusible alloys and are mainlyproduced for radiation shielding as well as tissue compensationpurposes. The study investigated the characteristics of MCP-200,MCP-150, and MCP-137 in relation to radiation shielding.

Keywords:Radiation shielding, attenuation, dose, cancer, buildup factor.

Contents

Chapter 1: Introduction 5

Chapter 2: Literature Review 7

2.1 Radiation and types of radiation 8

2.1. 1 Alpha Radiation 9

2.1.2. Beta radiation 9

2.1.3. Gama radiation 9

2.1.4. X-radiation 9

2.1.5. Neutron Radiation 10

2.2.1. MCP-200 11

2.2.2 MCP -150 14

2.2.3 MCP -137 17

Chapter 3: Research Objective and approach 18

3.1 Statement problem 18

3.2 Objective: 18

3.2 Method 19

Chapter 4: Current Work and Preliminary Research 20

Chapter 4: Work Plan 21

Chapter 5: Conclusion 22

References 23

Chapter1: Introduction

Differentmaterials placed between a source and a receptor can affect theamount of radiation transmitted from the source to the receptor. Sucheffects are due to attenuation and absorption of the emittedradiation in the source itself, of the material used forencapsulation of the source, or in a shielding barrier. Regardless ofhow it occurs, shielding is an important aspect of radiationprotection since it can be a form of radiation control therefore,the features of shields and their design, use, and effectivenesswarrant particular consideration. The shielding requirements forradiation protections depend on some factors. This includes the typeof radiation, exposure length, and the distance from the radiationsource. These factors are used to determine the right shieldingrequirements (Leo, 2013).

Sometypes of radiation have found their use in medicine. However, duringradiation therapy, scattering do occur, and this can affect healthyareas thus causing damage. One way of avoiding such damages to occurduring treatment is through shielding. Shielding as a processeliminates radiation dose to some certain parts of the target zonewhere radiation beam is targeted. MCP alloys are widely employed inradiation shielding (Leo, 2013).

Radiationcan cause a serious problem in industrial systems, medical x-rayfacilities or nuclear power industries, particle accelerator work,radioisotope among many other conditions. Containing and preventingradiation from causing harm to workers and the environment is acritical part of operating devices emitting some dangerous rays.Preserving both human safety as well as structures that can bedestroyed by exposure to radiation are serious concerns and shieldingsensitive materials including electronic gadgets and photographicfilm (Rangacharyulu, 2013).

Theprocess of controlling the degree and effects of radioactive rays’penetration varies depending on the type of radiation emitted.Indirectly ionizing radiation consisting of gamma rays, neutrons, andx-rays is usually classified differently from directly ionizingradiation involving charged particles. Different materials are suitedbetter for particular radiation types than others (Rangacharyulu,2013).

Radiationshielding is mainly based on the attenuation principle, which is theability of the material to minimize the ray or wave’s effect bybouncing or blocking particles through a barrier material. Thesecharged particles are attenuated by losing energy to reactions withelectrons within the barrier. On the other hand, gamma radiation andx-ray are attenuated through scattering, photoemission, or pairproduction. The harmful effects of Neutrons can be reduced through acombination of inelastic and elastic scattering. Most neutronsbarriers are made using materials that promote these processes(Rangacharyulu, 2013).

Theshielding ability of a given material is determined by the materialthickness required to absorb half of the radiation. That materialthickness is known as half-thickness. Radiation that passes throughone half-thickness will be reduced by half as it passed another halfthickness. The characteristics of material and type of radiationenergy determine half thickness.

Beforeusing any material for shielding gamma-ray radiation during medicaltreatment and protection, some factors need to be considered. Themost important factors to consider before selecting any material forradiation shielding is its build-up factor and attenuationcoefficient. For this study, the attenuation coefficient, build upfactors, as well as other factors will be determined for MCP-150, MCP200, and MCP 137 to evaluate their application in radiotherapy.Different thickness of MCP-150, MCP-200, and MCP-137 will be placedon the path of gamma rays with a narrow collimated beam from sourceswith changing energy. Three different thickness for each alloy willbe tested. The attenuation of the beam intensity calculated for eachmaterial. To compute the coefficient of linear attenuation of eachmaterial, the thickness of each sample will be plotted against thecorresponding beam intensity.

Chapter2: Literature Review

Differenttypes of radiation are now used in hospital industry for treatment ofsome conditions, including cancer, as well as scanning the internalbody organs to diagnose any problem. However, radiations, if allowedto hit healthy tissue, can cause damage to the body in the end.Therefore, to avoid such problems, radiation-shielding materials areoften used to protect the health part of the body from harm.

McCaffreyand associates (2007) studied the attenuating properties of varioustype non-lead and led-based radiation-shielding material and made acorrelation between materials properties, radiation attenuation,determined spectra as well as ambient dose equivalent. Theresearchers used well-characterized gamma ray and x-ray beam. Theauthors concluded that a single material or combination lack theability could not provide optimum shielding for all various ranges ofenergy. However, Macfrey et al. (2007) revealed that appropriatematerials choice for a given energy range could gibe significantlyenhanced shielding per unit mass over customary Pb-based materials.Muhammad Maqbool (2003) studied the transfer function of MCP-200alloy for beam intensity modulation. The author managed to find thetransfer function of MCP-200 to be 30 cGy.

Hopkinset al. (2012) determined the linear attenuation coefficient as wellas buildup factor of MCP-96 alloy for (54) Mn, (60) Co, and (137) Csgamma emitters and Nal detector. The researchers varied the thicknessof MCP-96 attenuator from 1-4cm. A collimated beam of gamma rays waspassed through different thickness of MCP-96 alloy. The coefficientsof linear attenuation were determined through the plot of thecollimated beam intensity versus the attenuated thickness. The studyfound that for each thickness of MCP-96 alloy, the ratio ofattenuated beam to the un-attenuated beam was higher in broad-beamgeometry than in narrow-beam geometry. Besides, they found that theattenuator thickness and beam energy increase the buildup factor. Hopkins et al. (2012) concluded that buildup factor needed todetermine and included for dose correction as well as precision whenMCP-96 alloy are used for radiation shielding and protectionpurposes. From the above studies, it is important, that the radiationshielding characteristics of any materials be determined before beingused for shielding purposes.

2.1Radiation and types of radiation

Thepurpose of radiation shield is to protect objects that can sufferradiation damage. Radiation also referred as ionization radiation isan energy in the form of particles or waves with a force that canremove electrons from atoms. There are different sources ofradiation, for instance, nuclei of unstable atoms. As such,radioactive atoms (radioisotopes or radionuclides) attempt to becomestable, their nuclei emit or eject particles as well as high-energywaves—a process defined as radioactive decay. Some radionuclidesincluding thorium, uranium, and radium have existed since the earthwas formed. Human activities including the atoms splitting in anuclear reactor are also known to produce radionuclides. Irrespectiveof their mode of formation, all radionuclides release radiation (Leo,2013).

Themain forms of radiation emitted in a radioactive decay are gammarays, beta particles, and alpha particles. Radiation can emanate fromman-made radionuclides or natural sources. Synthetic X-rays, anotherradiation type, are created outside of the nucleus. Nearly all x-rayexposure that individuals receive is artificially produced.

Thereare four main types of radiation mainly encountered: x-radiation,beta radiation, alpha radiation, and gamma radiation. Theseradiations also encountered in high-altitude flight and nuclearplants and ejected from certain industrial radioactive sources (Leo,2013).

2.1.1 Alpha Radiation

Alpharadiation takes place when an atom goes through radioactive decay,producing a particle, the alpha particle comprising two neutrons andtwo protons, changing the atomic number and atomic mass of the atom. Alpha radiation is unable to penetrate the skin of human. However,materials emitting alpha radiation can cause harmful effect to humansif the material is absorbed through open wounds, swallowed orinhaled. Alpha radiation only travels few centimeters in air andcannot penetrate clothing. Examples of materials that emit alpharadiation are thorium, uranium, radon, and radium (Leo, 2013).

2.1.2.Beta radiation

Whenan atom emits a positron or an electron, this is known as betaradiation. Because of its smaller mass, beta particles can travellarger distances in the air up to several meters and can be stoppedusing a stack of paper or a thick piece of plastic. Beta radiationcan penetrate human skin a few centimeters (germinal layer) thusposing serious health risk.

2.1.3.Gama radiation

Gammaradiation is a highly penetrative electromagnetic radiation. Gammaradiation can travel many inches in human tissue and many feet in theair. Gamma radiation can penetrate most materials hence known aspenetrating radiation. Dense materials are required for shieldingfrom gamma radiation.

2.1.4.X-radiation

X-Rays have similar characteristics to that of gamma radiation.However, the difference is that x rays originate from the cloud ofthe electron. This is due to energy changes in an electron includingmoving from a higher energy level from a lower energy level resultingin the release of excessive energy (Leo, 2013).

2.1.5.Neutron Radiation

Neutronradiation comprises a free neutron, emitted due to induced orspontaneous nuclear fission. Neutron radiation can travel hundreds ofmeters in the air. The hydrogen-rich material can easily block thistype of radiation such as water or concrete.

Fig1: Summary of types of radiation (Leo, 2013).

Characteristicsof various radiation materials have been studied by a number ofscholars. The most commonly studied material is the Lead. However,lead is poisonous material especially when not handle with care.Therefore, there is a need for scholars, to switch to studying othermaterials that are harmless such as MCP alloys. Little literatureexists about radiation shielding characteristics of MCP alloys moreso that of MCP-157 and MCP-200 and MCP-150 (&quot5NPlus :: Low Melting Point Alloys&quot, 2016)

2.2MCP Alloys

Thesealloys have low melting points (fusible alloys) and are mainlyproduced for radiation shielding protection as well as tissuecompensation purposes. MCP alloys are produced by Bismuthspecialists: Mining and Chemical Products Limited. The Lower meltingpoint of MCP alloys makes the metal easy to mold to particular shapesrequired in radiation therapy. These alloys are reusable and canreproduce very fine details.

2.2.1.MCP-200

Itconsists of 91% tin and 9% zinc. MCP-200 is free from lead, a metalthat normally causes harm to human. Lead is employed to manufacturemetal products, batteries, and devices for radiation shielding, andcan negatively affect musculoskeletal, cardiovascular, andneurological among other organ systems. MCP-200 is the mostpreferred for radiation shielding purpose because of its highavailability and its affordability. In general, MCP-200 alloy is usedin spraying applications. The alloy is mainly suitable for thermalprotection tools designed to yield at 1970C (Grote&amp Antonsson, 2009).

Justlike other alloys with low melting point, it undergoes equilibrium following solidification. Even though melting behaviors areinfluenced by the thermal history and age of the alloy, the observedvariances are of less significance as compared with Bismuth alloys,which normally melt in a quite lower temperature range, changes aremore complex and slower. The alloy in molten form is vulnerable todross formation through oxidation thus require a protectiveatmosphere. Pressurized nitrogen is often preferred to air.

Characteristics

Typical Value

Melting point

197 °C

Brinell Hardness

21.5

Density

7.27 g/cm3

Specific heat at 25°C (solid)

0.239 J/g.°C

Thermal Conductivity

0.61 J/sec.cm.°C

Enthalpy of fusion

71.2 J/g

Specific heat at 120°C (liquid)

0.272 J/g.°C

Electrical Resistivity

11.2 m. Ω cm

Table2 (&quot5N Plus:: Low Melting PointAlloys&quot, 2016).

Fig2.2.1a: The Tin-Zinc Phase Diagram.

Fig2.2. 1b: Solidification (&quot5N Plus::Low Melting Point Alloys&quot, 2016)

Fromfig 2.2 above, there is no evidence of post-solidification of furtherreaction. For MCP-200 alloy, the plateau level defines clearly theeutectic temperature.

Fig2.2.1c: Melting characteristics of MCP-200 (&quot5NPlus:: Low Melting Point Alloys&quot, 2016).

Fig2.2.1d: Viscosity of MCP-200 (&quot5NPlus:: Low Melting Point Alloys&quot, 2016).

Justlike those alloys with low melting point, the MCP-200 viscosity islow and non-Newtonian. However, the data as in fig 12 have beeninfluenced by conditions of measurement and the high surface tensionof the alloy, exclusively close to its melting point. The values infig 12 were obtained through a Brookfield RVT viscometer (&quot5NPlus:: Low Melting Point Alloys&quot, 2016).

2.2.2MCP -150

Thisis typically a non-eutectic alloy of Tin and Bismuth. The solid is βand α phase, respectively the solid solution of Tin in Bismuth andBismuth in Tin. Just like other metal alloys with low melting point,it undergoes a slow equilibration following solidification, thuschanging its physical properties. It has low viscosity and thisproperty combines with bright surface finish as well as suitablemelting range to produce an alloy mainly adapted to accuratereproduction through casting (&quotProductData Sheet MCP 150/Metspec 281/338 Alloy&quot, 2016).

Characteristics

Typical Value

Compressive Properties: Proof stress at two-days and 70-days

(0.2% set)

(1.0% set)

41.8 – 46.2 MPa

52.6 – 52.8 MPa

Brinell Hardness

23-24

Density

8.21g/cm3

Specific heat at 25°C (solid)

0.180 J/g.°C

Melting Range

135 -170°C

Enthalpy of fusion

47.5 J/g

Specific heat at 120°C (liquid)

0.213 J/g.°C

Electrical resistivity

34.0 m Ω.cm

Tensile Properties: Data at two-days and 70 days

Proof stress 0.2% set

Tensile Strength

Elongation (% in 5.65 )

31.6 rising to 37.5 MPa

62.5 falling to 58.5 MPa

105 falling to 35

Fig2: Solidification (&quotProduct DataSheet MCP 150/Metspec 281/338 Alloy&quot, 2016)

Thesolidification of 300g sample show 2 clearly defined arrests at 1700Cand 1350 C. The plateau level of this alloy defines clearly the solidustemperature.

Fig2.2.2a: Melting (&quotProduct DataSheet MCP 150/Metspec 281/338 Alloy&quot, 2016).

Thestructural alteration occurring following solidification can be madeclear through differential scanning calorimetry. Although the plasticrange is basically unaltered, the onset temperature, is found haveslightly changed in older specimens (&quotProductData Sheet MCP 150/Metspec 281/338 Alloy&quot, 2016).

2.2.3MCP -137

MCP-137a Bismuth (58%) and Tin alloy. For best purposes MCP-150 can beregarded as system eutectic, with reported values is in the range(51-58% Bi). Just like other alloys with low melting point, MCP 137goes through a slow equilibration after solidification thus changingthe physical properties (&quot5N Plus:: Low Melting Point Alloys&quot, 2016).

Chapter3: Research Objective and approach 3.1Statement problem

Untilnow, there has not been a perfect method of treating cancer.Radiation method also has several side effects. As a result, therehas been a constant improvement in that field to reduce the negativeside effects caused by gamma and x-rays. These rays in addition todestroying cancerous cells also destroy healthy cells thus puttingyour life into great risks. Therefore, studied the characteristics ofradiation shielding materials can help in improving the protectionprocess during radiation therapy.

3.2Objective:

Thisstudy is to establish the characteristics of MCP-137, MCP-200, andMCP-150 alloys that make them suitable be used for radiationshielding and protection.

Significanceof the Study

Thestudy determines the buildup factors, linear attenuation, and otherradiological characteristics, making MCP-150, MCP-200, and MCP-137readily available for radiation shielding and protection use andtissue compensation. The obtained values can be used to find thethickness and shape of the alloy required and the radiation dose. With an abundance of shielding materials that are effective, cancertreatment through radiation therapy can be improved and the shieldingand protection process enhanced.

3.2Method

Theresearcher will introduce primary experimental tools as well asmethods to be used in the study. It will include differentestablished spectroscopic and microscopic techniques of measurements.In addition, computer-aided simulations will be used.

Chapter4: Current Work and Preliminary Research

Theresearcher is currently going through most of the published workrelevant to the area of study. There are many articles and literatureabout the research problem hence the need for sorting. First,ensuring that the selected literature are up-to-date and are peerreviewed by a recognized body. The researcher has embarked onconducting preliminary research using computer-aided simulation. Thiswill help the researcher to have an overview on how to handlesuccessful the entire research process.

Chapter4: Work Plan

Steps In The Research Plan

Deadline for Completion

Proposal submission

A research design plan

Getting permission/getting access to work at (—)

Literature Review

Setting selection criteria

Design and testing data collection tools

Conducting the experiment

Grouping and coding data

Design as well as testing of a computer program

Raw tabulations/draft analysis of quantitative data

data Analysis

Report up of findings

Final research product(s) presentation

Chapter5: Conclusion

Thereis need for continuous improvement radiotherapy techniques used totreat cancer. One method is ensuring that stray rays are protectedfrom reaching the healthy parts of the body. This can be achieved byusing a best radiation shielding material. Attenuation propertiesand buildup factors determine the type of material that can bestshield radiation.

References

5NPlus:: Low Melting Point Alloys.(2016). Webcache.googleusercontent.com.Retrieved 25 August 2016, fromhttp://webcache.googleusercontent.com/search?q=cache:bWeuyn39QfYJ:www.5nplus.com/en/products/low-melting-point-alloys/+&ampcd=2&amphl=en&ampct=clnk

Grote,K.-H., &amp Antonsson, E. K. (2009). Springerhandbook of mechanical engineering.New York: Springer.

Hopkins,D., Maqbool, M., &amp Islam, M. (2012). Linear attenuationcoefficient and buildup factor of MCP-96 alloy for dose accuracy,beam collimation, and radiation protection. RadiologicalPhysics And Technology, 5(2),229-236. http://dx.doi.org/10.1007/s12194-012-0158-1

Leo,W. R. (2013). Techniques for Nuclearand Particle Physics Experiments: A How-to Approach.Berlin, Heidelberg: Springer Berlin Heidelberg.

MAQBOOL,M. (2004). DETERMINATION OF TRANSFER FUNCTIONS OF MCP-200 ALLOY USING6 MV PHOTON BEAM FOR BEAM INTENSITY MODULATION. J.Mech. Med. Biol.,04(03),305-310. http://dx.doi.org/10.1142/s0219519404001053

McCaffrey,J., Shen, H., Downton, B., &amp Mainegra-Hing, E. (2007). Radiationattenuation by lead and nonlead materials used in radiation shieldinggarments. Med.Phys.,34(2),530. http://dx.doi.org/10.1118/1.2426404

ProductData Sheet MCP 150/Metspec 281/338 Alloy.(2016). Webcache.googleusercontent.com.Retrieved 25 August 2016, fromhttp://webcache.googleusercontent.com/search?q=cache:6D17PCEItjgJ:www.5nplus.com/files/4713/8929/3067/Alloy_150_Tech_Data_Sheet_web.pdf+&ampcd=3&amphl=en&ampct=clnk

RangacharyuluC. (2013. Physics of NuclearRadiations: Concepts, Techniques and Applications.Boca Raton, Florida: Taylor &amp Francis,

TongX. Colin. (2016). Advanced Materialsand Design for Electromagnetic Interference Shielding. BocaRaton, Florida: CRC Press.

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