UNIVERSITI SAWS MALAYSIA Peperiksaan Kursus Semasa Cuti Panjang Sidang Akademik 2003/2004 April 2004 ZCT 533/4 - Dosimetry And Radiation Protection [Dosimetri Dan Perlindungan Sinaran] Duration : 3 hours [Masa : 3 jam] Please check that the examination paper consists of THIRTEEN pages of printed material before you begin the examination. [Sila pastikan bahawa kertas peperiksaan ini mengandungi TIGA BEL4S muka surat yang bercetak sebelum anda memulakan peperiksaan ini.] Instruction : Answer all FIVE (5) questions . Students are allowed to answer all questions in Bahasa Malaysia or in English. [ Arahan : Jawab kesemua LIMA soalan. Pelajar dibenarkan menjawab semua soalan sama ada dalam Bahasa Malaysia atau Bahasa Inggeris.]
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UNIVERSITI SAWS MALAYSIA
Peperiksaan Kursus Semasa Cuti PanjangSidang Akademik 2003/2004
April 2004
ZCT533/4 - Dosimetry And Radiation Protection[Dosimetri Dan Perlindungan Sinaran]
Duration : 3 hours[Masa : 3jam]
Please check that the examination paper consists of THIRTEEN pages of printed materialbefore you begin the examination.
[Sila pastikan bahawa kertas peperiksaan ini mengandungi TIGA BEL4S muka suratyang bercetak sebelum anda memulakanpeperiksaan ini.]
Instruction : Answer all FIVE (5) questions . Students are allowed to answer allquestions in Bahasa Malaysia or in English.
[Arahan: Jawab kesemua LIMA soalan. Pelajar dibenarkan menjawab semua soalansama ada dalam Bahasa Malaysia atau Bahasa Inggeris.]
2
1 .
(a)
Photons of energy 1 MeV has[(a)
Foton bertenaga 1 MeV mempunyai]
=2.8x10-' m' kg- '
Determine the energy fluence and the photon fluence needed for anexposure of 100 R.[Tentukanfluens tenaga danfluensfoton yang diperlukan untuk suatudedahan 100 R.]
(iii)
Determine the energy deposited in the aluminium.f(ii) Tentukan tenaga yang diendapkan dalam aluminium.]
I C) A
[ZCT 533]
[4 marks]
Explain the differences between energy transfer and the net energy transferin a volume V.Jelaskan perbezaanperbezaan di antara pemindahan tenaga denganpemindahan tenaga bersih dalam suatu isipadu V.]
[4 marks
(c)
Consider a parallel beam of 1 MeV photons incident perpendicularly to analuminium plate at a fluence rate of 101° m2 s-1 . The thickness of thealuminium is 1 .2 cm and its density is 2700 kg m3.
[(c)
Pertimbangkan suatu alur foton 1 MeV yang datang secara sereyanfkepada suatu plat aluminium pada suatu kadar fluens 101° m" s- .Ketebalan aluminium ialah 1.2 cm dan ketumpatannya ialah 2700 kg m-3.1
Calculate the ratio of photons transmitted through withoutundergoing any interaction in the aluminium.Hitung nisbah foton yang ditransmissikan tanpa mengalamisebarang interaksi dalam aluminium.]
Calculate the ratio of the photon energy passing through thealuminium.Hitung nisbah tenagafoton yang melalui aluminium.]
(iv)
Determine the ratio of the kinetic energy of the electrons emitted asbremsstrahlung .
f(iv)
Tentukan nisbah tenaga kinetik elektron yang dipancarkan sebagaibremsstrahlung.]
State their importance in the measurement of exposure and dose .[Nyatakan kepentingan perkaraperkara tersebut dalam pengukurandedahan dan dos.]
[ZCT 533]
[8 marks]
(b)
A 8-MeV p-ray enters a volume V and undergoes pair-productioninteraction. The electron and positron produced have identical energies .The electron spends half of its kinetic energy before escaping from V. Thepositron spends three quarter of its energy before being annihilated. Theresulting photons escape from V. Determine the kerma and the absorbeddose in V given that the volume V = 1 cm3 and its density is I kg m-3 .
[(b)
Suatu sinar y 8-Me V memasuki suatu isipadu V dan mengalami interaksipenghasilan pasangan. Elektron dan positron yang terhasil mempunyaitenaga yang seiras. Elektron itu menghabiskan setengah tenaga kinetiknyasebelum keluar dari V. Positron itu pula menghabiskan tiga sukutenaganya sebelum dihapuskan . Fotonfoton yang terhasil terkeluar dari V.Tentukan kerma dan tenaga terserap dalam Vjika diberikan isipadu V = 1cm3 dan ketumpatannya ialah 1 kg m3.j
[12 marks]
3 .
(a)
Describe the meaning of the mass stopping power and the restricted massstopping power.
[(a)
Perihalkan maksud kuasa penghenti jisim dan kuasa penghenti jisimterbatas.]
[6 marks]
Describe the Bragg-Gray cavity theory and the assumptions involved.Perihalkan teori rongga Bragg-Gray dan anggapan-anggapan yangterlibat.J
[6 marks]
4
(c)
ATLD chip with a thickness of 0.5 mm is used to determine the absorbeddose in water due to a Co-60 gamma source . (i) Could the Bragg-Graycavity theorem be used to determine the absorbed dose in water? Explain.(ii) Describe how the absorbed dose in the chip is determined .
[(c)
Suatu cip TLD dengan ketebalan 0.5 mm digunakan untuk menentukan dosterserap dalam air akibat suatu sumber gamma Co-60. (i) Bolehkan teoremrongga Bragg-Gray cavity digunakan untuk menentukan dos terserapdalam air? Jelaskan. (ii) Perihalkan bagaimana dos terserap dalam cip ituditentukan.J
4 .
(a)
Describe the construction of a free-air ion chamber. Explain how it is usedto measure exposure at a point in air.
[(a) Perihalkan binaan kebuk ion udara bebas. Jelaskan bagaimana isdigunakan untuk mengukur dedahan pada suatu titik dalam udara.]
[10 marks]
(b)
Afree-air ion chamber has a diaphragm opening of 1 .00 cm diameter and acollecting plate 12 cm long. The separation between the collecting plateand the guard plate is 0.5 mm. The distance between the diaphragm and thefront edge ofthe collecting plate is 30 cm. The temperature of the dry air inthe chamber is 23 .1'C, its pressure is 755 torn and (fclp) .i, = 0.155 cm2 g" 1 .Assume that no x-rays is scattered into the chamber and also all electronsare stopped after their full ranges.
[(b) Suatu kebuk ion udara bebas mempunyai suatu bukaan diaframberdiameter 1 . 00 cm dan suatu platpengumpu112 cm panjang. Pemisahandi antara plat pengumpul dan platpengawal ialah 0.5 mm. Jarak di antaradiafram dan pinggir hadapan plat pengumpul ialah 30 cm. Suhu udarakering dalam kebuk ialah 23.1 `C tekanannya ialah 755 torr dan(p/p).,, = 0.155 cm2 g". Anggap tiada sinar-x yang diserakkan ke dalamkebuk dan juga kesemua elektron berhenti selepas mencapai julatpenuhnya.
126
[ZCT 533]
[8 marks]
Calculate the exposure at the diaphragm for charge Q = 6.17 x 10'7C (corrected for ion recombination) . Give your answer in C kg-1 andalso in R. The density of dry air at 0°C and 760 torr is 1 .293 kg m-3Hitung dedahan pada diafram bagi cas Q = 6.17 x 10"' C (telahdibetulkan bagi penggabungan semula ion). Berikanjawapan andadalam C kg1 dan juga dalam R. Ketumpatan udara kering pada0 `C dan 760 torr ialah 1.293 kgm3J
(ii)
Calculate the absorbed dose in air at that point.f(ii)
Hitung dos terserappada titik itu.J
(b)
Discuss the ALARA concept.[(b)
Bincangkan konsep ALARAJ
- 5[ZCT 533]
[10 marks]
(a)
Describe the type ofthermal neutron reaction occuring in tissue . What is itsrelative contribution in term of tissue size.
[(a)
Perihalkan jenis tindakbalas neutron terma yang berlaku dalam tisu.Berapakah sumbangan relatifrrya dalam sebutan saiz tisu.]
[5 marks]
[5 marks]
Define maximum permissible dose (WD). Describe the differencesbetween occupational MPD and non-occupational MPD.Takrifkan dos maksimum yang dibenarkan (MPD). Perihalkan perbezaan-perbezaan di antara MPDpekerja dan MPD bukanpekerja.J
[ 10 marks]
LAMPIRAN
APPENDIX A.2 .
Conversion Factors
Electron rest massProton rest mass
Neutron rest mass1 electron volt (eV)
1 joule (J)1 coulomb (C)
1 gray (Gy)1 sievert (Sv)
Energy-wavelength conversion :
Exposure conversion :
6
1 kg = 5.6095 x 10 29 MeV1 amu = 931 .50 MeV
- 0.51100 MeV- 938.26 MeV= 939.55 MeV= 1.6022 X 10`9 J= 1.6022 X 10-12 erg= 10 7 erg= 2.9979 x 10 9 esu= 1 J/kg = 10 2 rad = 10 4 erg/g= 1 J/kg
1 .23985 X 10-6 eV m12.3985 keV A
i roentgen (R) = 2.58 X 10-4 C/kg1 C/kg = 3876 R
(ZCT533/a)
7
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LAMPIRAN
(ZCT533/4)
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