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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