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UT CH 302 - Some question to ponder about nuclear chemistry
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Work%Sheet%13%Some%question%to%ponder%about%nuclear%chemistry%%%1.%A%person%goes%to%get%radiation%treatment%for%cancer%utilizing%“brachytherapy”%in%which%a%small%radioactive%source%is%placed%directly%into%the%body.%%The%radiation%center%has%some%newly%created%radioactive%sources%of%192Ir.%%They%start%out%as%10%Curie%sources.%%Under%computer%control%and%robot%inserts%the%source%using%a%long%needle%into%the%patient’s%body%and%holds%it%there%for%the%treatment.%%When%the%source%is%new,%the%treatment%can%be%as%short%as%say%30%minutes.%%%%Given%that%the%halfLlife%of%192Ir%is%74%days,%what%would%be%the%intensity%of%the%source%that%was%originally%10%Curies%after%3%months?%%How%much%longer%would%a%radiation%treatment%take%to%achieve%the%same%exposure%of%radiation%for%the%patient?%€ 192Ir half life = t1/ 2= 74 daysk = decay constan t =ln(2)t1/ 2=ln(2)74 days= 9.365 × 10−3days−1First order kinetics :A (90 days) = A0exp[−kt] = 10 Curies* exp[−9.365 × 10−3days−1• 90 days]A (90 days) = 4.3 Curies%%€ For the patient to recieve the same amount of radiation from a 4.3 Curie source, it would take :30min∗10Curie4.3Curie= 70min%To%understand%the%complexity%of%computing%the%exposure%to%a%particular%source,%look%at%the%typical%decay%of%192Ir%which%is%chosen%in%part%for%its%simplicity.%http://ozradonc.wikidot.com/iridiumL192%%%%2.%%%%Why%are%many%forms%of%nuclear%decay%also%accompanied%by%the%gamma%radiation?%Often%the%nuclei%formed%directly%after%nuclear%decay%are%not%in%their%ground%nuclear%state,%so%a%high%energy%photon%(gamma%ray)%is%emitted;%as%a%result%the%newly%formed%nucleus%is%in%an%energetically%more%stable%state.%%%3.%%You%are%standing%10%feet%away%from%three%different%radioactive%sources.%%All%three%happen%to%be%1%Curie%sources.%%The%first%is%primarily%an%alpha%emitter,%the%second%a%beta,%and%the%third%both%a%beta%and%gamma%source.%%%Will%your%exposure%be%the%same%or%different%for%these%three.%%If%different%from%which%will%your%exposure%yield%the%highest%exposure%as%measured%in%Sieverts?%%%%%4.%%%Which%will%give%you%a%higher%exposure%in%Sieverts:%holding%a%10%microCurie%alpha%emitter%in%your%hand,%or%breathing%in%a%10%microCurie%alpha%emitter%into%your%lungs?%%Or%will%they%both%be%the%same%since%you%are%essentially%absorbing%all%the%radiation%that%is%emitted?%%A%Sievert%is%a%unit%of%measure%that%quantifies%the%biological%effect%of%ionizing%radiation.%%Holding%an%alpha%emitter%is%not%typically%dangerous,%since%large%Helium%nuclei%can%be%effectively%shielded%from%human%tissue%by%a%layer%of%dead%skin.%%Inhalation%and%ingestion%of%alpha%particles,%however,%can%amount%to%a%serious%dose%of%radiation%that%could%damage%one’s%cells.%%Breathing%in%an%alpha%emitter%would%result%in%a%higher,%potentially%lifeLthreatening%radiation%dose,%and%a%higher%exposure%as%measured%in%Sieverts.%%More%practice%with%balancing%and%decay%products%%%Balance%the%following%%%2713Al + 42He → 3015P + € 01n 32He + 32He → 2 11H + € 24α 23993Np → 23994Pu + € −10β € 83212Bi→ 42He + 20881Tl %The%following%nuclei%decay%via%electron%capture%predict %their%decay%product%%57Co€ +−10β→2657Fe%%68Ge€ +−10β→3168Ga%%49V€ +−10β→2249Ti%%The%following%undergo%alpha%emission,%predict%their%decay%product%%226Ra€ →86222Rn +24α%%238U€ →90232Th +24α%%218Rn€ →84214Po +24α%%The%following%undergo%beta%decay,%predict%their%decay%product%%218Po€ →85218At +−10β%%90Sr€ →3990Y +−10β%%63Ni€ →2963Cu +−10β%When%we%speak%of%dangerous%radiation%exposure,%are%we%customarily%speaking%of%alpha%radiation,%beta%radiation%or%gamma%radiation?%Discuss.%Gamma%radiation%exposure%is%customarily%considered%the%most%dangerous%type%of%radiation.%%Gamma%rays%are%a%type%of%ionizing%radiation,%and%can%penetrate%through%the%skin%(and%even%go%all%the%way%through%a%human%body);%gamma%rays%are%highLenergy%photons%that%can%damage%DNA%and%cells%without%killing%them,%which%can%lead%to%replication%of%altered%cells.%%Beta%particles,%which%are%also%ionizing%particles,%have%shorter%mean%free%paths%and%are%less%penetrating%than%gamma%rays,%so%they%are%considered%less%dangerous%than%gamma%rays.%%Alpha%emitters,%which%are%strong%ionizing%agents,%will%only%do%substantial%harm%if%they%are%inhaled/ingested/intravenously%introduced%into%the%human%body,%so%avoiding%alpha%radiation%exposure%is%not%a%concern%since%they%cannot%penetrate%human%tissue.%%People%who%work%around%radioactivity%wear%film%badges%to%monitor%the%amount%of%radiation%that%reaches%their%bodies.%These%badges%consist%of%small%pieces%of%photographic%film%enclosed%in%a%lightLproof%wrapper.%What%kind%of%radiation%do%these%devices%monitor?%%Dosimeters%can%be%used%to%monitor%gamma%rays,%XLrays,%neutrons,%beta%particles,%etc.%LL%it%really%depends%on%the%type%purchased.%%The%most%common%types,%though,%monitor%gamma%and%XLray%radiation.%%A%sample%of%a%particular%radioisotope%is%placed%near%a%Geiger%counter,%which%is%observed%to%register%260%counts%per%minute.%Six%hour%later,%the%detector%counts%at%a%rate%of%20%counts%per%minute.%What%is%the%halfLlife%of%the%material?%%€ ln A[ ]= ln A[ ]0− ktln 20[ ]= ln 260[ ]− k(360min)k =ln 20[ ]− ln 260[ ]−360 min= 7.124 × 10−3min−1t1/ 2=ln2k= t1/ 2=ln27.124 ×10−3min−1= 97 min%%%%%%%%In%what%way%is%the%emission%of%gamma%radiation%from%a%nucleus%similar%to%the%emission%of%light%from%an%atom?%%A nucleus in an excited state may emit one or more photons of discrete energies. The emission of gamma rays does not alter the number of protons or neutrons in the nucleus, but moves the nucleus from a higher to a lower energy state (unstable to stable). Gamma ray emission frequently follows beta decay, alpha decay, and other nuclear decay processes.


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UT CH 302 - Some question to ponder about nuclear chemistry

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