. XAC DINH NONG DO DONG VI PHONG XA "'U

TAPCHiKHOAHOCOHSPTPHCM c--,=^«., - , „ ,

^ So 6(84) nam 20h

. XAC DINH NONG DO DONG VI PHONG XA " ' U

TRONG MAU LirONG THVC THirc P H A M

B A N G P H 6 K E G A M M A P H A N G I A I CAO

LUU TAM BAT, TRU-ONG TH| H(iNG LOAN", TRU'DNG H&U N G A N T H V "

HUYNH THI Y6N HCbNG"', VO NGCPC B A " L L I NH& QUVNH^^^

TOM TAT

Bai bao ndy phdn lich nhiing khia cgnh phiic Igp khi su dung phi ki gamma phdn gia, cao de phan tich "'U n-ong cdc mdu luang Ihuc Ihuc phim (lm): dug ra cdcZ

Ti khda: ddng vi phdng xa, thuc phim, HPGe.

ABSTRACT

Determining "'U radioactivity concentration in food using high-resolution gamma spectrometer

'he d^e'^minaZnol'^7'!,'" " ' " " ' ""^"""^ ^ish-resolulion gamma speclromeler for

Keywords: Radioactivity, Food, HPGe.

J- Gidi thifu

dung f ' i ' r t i T x T d ! S ; n & t ' " ' " ^° """ ' ^ ^ ' ^ ' " * ™ ^ ' (™G=) * " - - .hue thuc ph m sfdu*fh6 do n l ? ' -f M"U^ "=*' " ' " ™" " ^ ^ ^ E^' ^ ^ '"™S n6n bo qua gi"; ^^Tl^^t 1 * J ™ '"u"*" '**^ "" "^ ^^ '"^' -^^n bfag khong khi "'II rrt r J - .,- I u ^ " '''=" "^"^ P''^' "*<: dinh riang ^"U v4^'Ra Trnn»

phuong phap P h 6 ' i p t H ^ p l ™ ; I r i C P MS h" " " "l"" t " ^ "« " ' ' ^ ^^"«

_CN Taring Bai hgc Khoa hec Tg. nhien, BHQG TPHCM - T h l ; Z ^ ' " ' " ' " '^""^ ""= "^^ ">'^"- BHQG TPHCM

ThS, Vi0n ngh,6n c»u IMOi truing va cac vin Oi xa hOi Ha N«i

TAPCHi KHOA HOC BHSP TPHCM Ltm Tam Bat va tgk

xac dinh "*U. su dung ddng ttioi mgt dSu do hinh tin kieh ttiuoc Ion d6 xac dinh cac dong VI phong x j voi cae dmh a vimg luong eao. [4, 6]

Sudung cic he phd kS gamma phan giai cao dap ung nang Iuong giai rong CO tti6 phan tieh xac djnh d j ^ nong do ^ U . Tuy nhiea ttong cac eong ttinh nghien cuu ttuoc day [5, 9] eho ttiay-»U khong xac dinh duoc ttuc tiep vi no phat ra dinh hue xa CO nang luong 49,55 keV voi cuong do ttiip (0,069%) va dmh nang luong 113,5 keV cling voi erong do rai ttiap (0,0174), hai dmh na> ttiuong bi lip boi n&i tan xa lien tiic Compton cua

~K von r a l o n ttong mm. Phuong an kha di n h i la xac <Enh ^ U qua hai ddng vi con sat rfc™. f T i S ; , ! ° ban la 24.1 ngay va phat ra nang luong 63,3 keV (4,8%) va 92,6 keV n ;,r^x'> ™ w 7 ° ' "^^ " ^ " ' ' l ^ PMl voi hai dmh nang luong 766,4 keV (cuong do

;? J ' l ^ u ? ^ ^ ^ < ™ ^ '*' ''•'^'^''°*- •r"> nhien, o vung nang luong cao, hieu s u i ghi dau do ttiap nen kho xac dinh duoe »^rh qua 2 dinh eua » * P a (ttiuc t« dinh 1001 0 keV ch, dimg de xac djnh mau co ham luong =«0 eao). Trong 2 dinh eon lai ciia ^ ^ ia 63,3 keV va 92,6 keV, n p o i ta dimg 63,3 keV nhiju hon, mac dii co lln dinh 63 9 keV (cucmg do 0 ^ 2 3 % cua ='Th va 63,9 euimg do 0,255% cua ^ ) , Wii do cJn phii hieu chmK Dinh 92,6 keV eiia ™Th co lan 92,4 keV (2,81%) va 92,8 keV (2,77%) la dinh kep c m chuyen hoa K-X gamma, dinh nay tiiroc day it dupc dimg, nhmig hien nay vol phSn mem ya ttiuat toan tach dinh tot ttii ngucri ta da sir dung va co hieu qua (vln de nay ttiy meo timg phong tfu nghiem). Nhu vay, chiing toi su dung mpt ttong hai dmh 63.3 keV va 92,6 keV de xac djnh nong dp ™U ttong cae mlu LTTP. Khi sir dung hai dmh nay ed hai van de chinh can giai quyet, do la xu li dS hieu ehinh, tach phin ehdng chap o hai dinh nang Iupng su dung ndi tten, mjt khac Uiuc hien hieu chinh tu hip tfiu, nhu vay. ttong mdt phep do CO the xac dinh dupe ^ U , ciing tat ca cae ddng vj phdng xa khae nhu ^'°Pb « R a ,

Ih, cae dong vj phan ra Clia chung v a " K . 2. Phinmg phap va vgt lieu

2.1. He phi ki gamma HPGe GMX3SP4-70

„ . u ? ^ ^^ ^ ' ™ " " ' ' " ^'^i •'""S cdng ttmh nay ttiupc Phdng ttii nghiem KI ttiuat T ? ™ ^ Truong Dai hpc Khoa hpc Tu nhiea DHQG TPHCM (eo sd Lmh Trung, IUu Due). He gom ed eac phan chinh nhu sau: D I U do HPGe sd Ilieu GMX35P4-TO S t h ? ' . 1 " ' L l ; " ^ ' ! ? * ' ™ - ^ * ' ^ ' " ' H™ * » g " " ngudn nudi cao tti6 eho dau do, khuech dai, bp bien do, nrong tu ttianh sd va khdi phan tich da kenh duoc tieh quanh dau do, va ttnet b, lam lanh cho dau dd X-Cooler III. He phd k8 duoc g h | , ndi ven may Unh ttiong qua edng USB, vice ghi nhan va xu li phd k6 gamma d ^ e ttiuc h^en bang cae phm mem chuyen dung MEASTRO - 3.2 (GammaVision - 5 3) He phd ke gamma phong ttiSp ed ttie ghi nhan eac tia gamma co nang luong ttr khoang 3 keV - d i n . ! : ^ c l ; i t l / ^ ) . " " " * ' " ^ ^ ^ <••"' " ^ ^ ' " ' ' " ^ ^ = - " C o , ti sd

TAP CHI KHOA HOC DHSP TPHCM So 6(84) nam 2016

2.2. Phtrang phdp tdch dinh nhieu tham gia vdo trong hai dinh 63,3 keV vd 92,6 keVcua'"Th

DJ xac dinh hoat dp "'U bJng dinh 63,3 keV ta cin hieu chinh su ddng gdp ciia dmh 63,9 keV cudng dp 0,255% cua ™Th.

DID dp phan giai FWHM eiia diu do phdng thi nghiem khdng the phan biet dupc 2 dinh 92,4 keV va 92,8 keV ciia ^"Th nen ta ed tiiJ xem day la 1 dinh 92,6 keV vdi xac suit phat la tdng xac suit cua 2 dinh ttianh phin. Khi dd Ai tinh hoat dp ™U bing dmh 92,6 keV ta cin hieu chinh su ddng gop ciia tia X nang Iupng 93,3 keV (3,19%) ciia ^'AC.

Cac bude phan tich xac djnh ndng dp ^''U su dung hai dinh 63,3 keV va 92,6 keV eu the nhu sau:

Suae I. Tinh dien tich dinh bSng chuong ttinh phan tich Gamma Vision. Bing cdch nhan dien dinh va lam khdp dmg dmh ta cd the ily dupc dien tich dinh 63,3 keV ddng thdi tach dupc dinh 92,6 keV va dinh 94,7 keV ciia ™Pa. Sd ddm dinh diipc the hien tren bang va hinh lam khop timg dinh dupe tti6 hi$n tren hinh bing mau dam.

Huth 1. Phdn ttch va tdch dinh dinh phi gamma 63.3 keVva 92,6 keV cia mdu 31

TAP CHi KHOA HOC DHSP TPHCM Ltru Tam Bdt vd tg

Hmh 2. Phan ttch vd Idch dinh dmh phi gamma 63.3keVvd 92,6 keVcua mdu 282 Buac 2. Tinh hoat dd eua ^-*Ac qua dinh 338,32 kcV va dinh 91 I.I keV, ki hieu

AAC-228.

92,6 kl^^kiliillt W - t ) ' ' " * '"^ ^"^ "^ " • ' " ' ' ' "' " ^ " ^ - ^ - ' " ^ ' = ' '' "^

R43J tevC^'Ac) = AA,.228 £(63,3 keV). y^^.,,^ (63.9 keV) R?2.6 I,.V(^'AC) = AA..221, .e(92,6 keV). yAc.22!(93,3 keV)

Vdi AAC-ZM 14 host dp ciia ^ A c , . E(63,3 keV) va e(92,6 keV) la hieu suit dinh tai nang Iupng 63,3 keV va 92,6 keV, y,..;,, (63,9 keV) va yA..2,8(93,3 keV) la xac sui, phat cua tia 63,9 keV va 93,3 keV ciia "*Ae.

Buac 4. Hieu chinh tde dp dem ddng gdp vao dinh 63,3 keV va 92 6 keV eii i '^Th tir dinh 63,9 keV va 93.3 keV cua '"Ac san phim eon ehau eiia "^Th.

Tde dp dSm tai dinh 63,3 keV va dinh 92,6 keV cua ^ ' u sau khi hieu chinh:

Ra J i.v('"U) = R,3j ,.v - R63J ».v('''Ac) R«.6kcv(''*U) = R«.6k,v - V«.v('''Ae)

. , . 7 ° ! •'"•"^X.™ R»wk« la tdc dp dem tdng tai nang Iupng 63,3 keV khi chua tat h va hieu chinh nhieu.

^ Bum 5. Tinh hoat dp cua ™U qua tde dp ddm dinh 63,3 keV va dinh 92 6 keV Ket qua hoat dp A tinh tir ttung binh cd ttpng sd cua dinh 63,3 keV va dmh 92 6 keV sau kh, hifu chinh la ket qua hoat dp ciia ™U va '^^li

TAP CHi KHOA HOC DHSP TPHCM So 6(84) nam 2016

2.3. Nghien cuu hiiu chinh tir hap thii gid tri hieu suit ghi dii v&i gamma 63,3 ke V vd 92,6 keV va binh hgc mau phdn tich dgng tru

Khi sir dung tia gamma nang Iuong ttilp 63,3 keV va 92,6 keV de xac dinh ^*U, can hieu chinh tu hip ttiu cho gia tti hieu suit ghi. Trong phin nay, chiing tdi thiic hien danh gia he sd hieu chinh tu hip ttiu ttong phan tich gamma eiia mlu LTTP vdi Mnh hpc mlu dang tm ddi vdi hai nang lugng nay. Viec hieu chinh tu hip fliu cho gia tii hi$u suat dupe danh gia nrong ddi so vdi su tu hip fiiu ttong mlu chuin dmg cd. Cac chat lieu raau mdi ttudng dupc danh gia su tu hip tiiu la ehit njn cua cac mlu LTTP Clia de tai KC.05.21/11-15 [1] chu yeu da dupe tto hda va nen vao hop ttu vdi chidu eao va mat dp khac nhau. Cd nhiSu phuong phap danh gia he sd hi^u chmh ttr hip ttiii tiiy thupc vao didu kien do rieng biet [2,3,7]. Trong edng trinh nay. chung tdi sir dung phan mem_ Angle 3 [8] de tinh torn hieu suit dinh, va hieu chinh anh hudng tu hip ttiu ddi vdi mau dang tru vdi chieu cao va mat dp khae nhau. Angle 3 la phin mem diing di hicu ehinh hieu suit cua hang Ortee (Mi), dupc mua kem theo he do. De lam di6u nay can xay dimg md hinh detector, hinh hpc mlu, ttianh phin nguyen td ttong mlu, m$t dp mau, eac dinh nang Iupng cin phan tich hoat dp. Cung cip hieU suit ttiuc nghiem tii mau chuan. Sau dd khi yeu cau, chuong ttinh se ty ddng xuit ra hidu suit dinh cho mlu em phan tich vdi eimg hinh dang hop chiia miu chuin nhung cd ttil ttiay ddi kich tiiuoc, eiing nhu ed su khac nhau ve mat dp va thanh phin trong mlu phan tich so vdi mau chum. Hinh 3 ttinh bay mdt giao dien gidi diieu eiia ehuong ttinh Angle

Hinh 3. Giao diin chuang trinh Angle

TAP CHl KHOA HOC DHSP TPHCM Lirti Tam Bdt vd tgk

chuin nay tten he phd kd HPGe dimg d6 phan tich. Hieu suit ttiuc nghiem tinh torn dupc vdi cae nang lupng khao sat ttieo cdng ttiirc:

Sm khi xac djnh dien tieh dinh cua mpt sd vach nang Iuong qum tam hoat dd cua cac nguyen td sdng dai khi dd dupc tinh bdi [3]: ' '

^"^>^73f (!)

ttong dd E(E) la hieu suit dmh tai nang lupng E, A la hoat dd (Bq/kg) ciia mlu chuin tai ttioi diem dmg do, R^. la tde dp ddm dmh da ttir phdng (sd ddm/s) va hieu chinh Uioi gim chet, m la khoi lupng mau (kg), va y la xac suit phat gamma (%). Cdng tiiuc tiw, dupe ap dung cho cae dong vj cd ttidi gim ban ra dai dl ttong khoang ttidi gim do so dem khong tiiay ddi nhieu.

^ Gia tti hieu suit nay la sd lieu diu vao cho Angle dl tinh torn su hidu chinh hieu suat ttieo chieu cao va mat dp tidp flieo cho mlu phan tich. Quy ttinh dinh gia he sd hieu chmh tu hap thu duoc chiing tdi dl xuit ttiuc hien nhu sau:

o. Khao sat hf sd hieu chinh ttieo chidu cao

92 6 k ^""^ '^^'^ " ' * '''*" ^"^' ' " ' * *^° '''''™ '^^° "^'"'' "^^ ' " ^ g ^^'^ ''^^ "*

-Jinh ti s6f(h) giiia hieu suit ddi vdi be day h va mat dd va ttianh phin vat lidu eua mau do e(h) vdi hieu suat tinh til raau chuin e(h,J.

f(h)

=

-SlL

£(h.) (2) - Khdp ti sd flieo chilu cao ttieo dmg ham phi, hpp. Ta cd he sd hidu chinh hieu

suat ttieo Uieo ehieu eao. Dang Iam khdp sau day dupc su dung tfiich hop cho dii lieu tuih toan dupe;

e(h) = a-bln(h-i-c)

a, b, e la he sd cd dupc tir viec lam khdp.

b. Khao sat he sd hieu chinh theo mat dp

keV °™^ '^^'^ " * *"''" ' " ^ ^"^ ""^ " ' ' •*' "*' ^" "™^ '"'"« '•^•^ ^^^ ™ '2,6 hi™ h ^ t * ^^ " I " - ' " * " ^ '^° ™ '''«" '"^' ™^" '^'"^- Kh-iP « ^ nay theo dmg

ham phu hpp. Taedhfsd hieu chinh theo mat dp. * f(p) = ^

s(Pa) (4)

- Khdp ti sd ttieo mat dp thep dang ham phii hpp. Ta ed hd sd hi?u ehinh hieu suit tti^^ttieo mat dp. D^g lam khdp sau day dupe su dpng thieh hpp eho dii m. t i t l

TAP CHi KHOA HOC DHSP TPHCM Sd 6(84) nim 2016

E(h)=a'-tbh-i-c'h' (5) a', b', c* la he sd ed duac tir viec lam khdp.

I.. Hieu suit ghi ddi vdi mau phan tich cu the

- Hieu suit ghi cda mau do vdi hop dung m l u dang ttu gidng hop dung mlu chuan nhung cd chieu cao hi va mat dp p, la:

E=E(h,)£(P|) (6) vdi: £(h,)=e(h„)f(h,) (7)

E(p,)=£(p„)f(p,) (8) 3. Ket qua va thao luan

3.1. Hi so hieu chinh tir hap thit khi thay doi chiiu cao vd mat do miu dgng tru dii v&i gamma nang lirffng 63,3 keVvd 92,6 keV

Blu tien phd eiia mlu chuin dupc do tten he phd kd GMX35P4-70. Thdng tin mlu chuin bao gdm: chuin dit RGUl dung ttong hop tru, dudng kinh 7,66cm, chilu cao 1,9cm, mat dp I,58g/cm', hieu suit tai dinh 63,3keV va 92,6keV dupc tinh toan tir phd thyc nghifm do dupc va eho trong Bang 1 sau:

Bang I. Gid tri hilu suit thuc nghiim tinh todn dugc doi vai nang lugng 63,3 keVva 92,6 keV Nang Iupng (keV)

63,3 92,6

HlSu s u i t dinh 0,06611 0,06429

Nhap gia trj hidu suit dinh thuc nghiem tinh tii mlu chuin nay vao Angle vdi mat dp khdng ddi (1,58 g/cm^) tinh toan hieu suit theo chilu cao mlu khac nhau.

Lam khdp da lieu hifu suit ttieo chilu cao mau. Ta dupc kit qua:

Vdi 63,3 keV: E(h) = 1,21337 - 0,47090.1n(h - 0,30746) Vdi 92,6 keV: E(h) = 1,26930 - 0,47392.1n(h - 0,12253)

BSng 2. Hiiu suit linh todn tir Angle vai chiiu cao mdu khdc nhau Chieu cao (cm)

1,3 1,7

Higu suit 6 3 3 keV

0,08679 0,08068 0,07526 0,07043

92,6 kcV 0,08172 0,07666 0,07211 0,06801

Ti so hieu suat 63,3 keV

1,31292

1,06544

92,6 kcV 1,27110 1,19239 __L12I69_

1,05786

TAP CHl KHOA HOC DHSP TPHCM Luu Tam Bit va Igk

1,9 2,1 2,4 2,6 3,0 4,0 5,0 6,0

0,06611 0,06221 0,05706 0,05402 0,04871 0,03876 0,03193 0,02702

0,06429 0,06090 0,05637 0,05365 0,04885 0,03962 0,03307 0,02824

1,00000 0,9411 0,86318 0,81715 0,73680 0,58634 0,48307 0,40878

1,00000 0.94734 0,87675 0.83454 0,75987 0,61627 0,51443 0,43929 Hinh 4 va Hinh 5 minh hpa sd lieu tinh toan va so lieu khdp cua hidu suit ttieo chieu cao. Ket qua cho tiiay dmg lam khdp dupe chpn phii hop tdt vdi sd lidu hieu suit ed dupc tir Angle.

Hmh 4. Sif Ihay dii hiiu suit

theo chieu cao mdu dot vdi tia 63.3 keV Hmh 5. Stf thay dii hiiu sudt theo chiiu cao mdu dii v6i tia 92,6 keV

Tucmg tu, vdi chieu eao khdng diii (h -- 1,9era), tinh toan hieu suit khi thav .Jdi raat dp mau khac nhau. Ket qua dupc cho trong Bang 3.

Bang 3. Hiiu suit Iheo mat do tinh tir Angle Mjt dp (g/cm^)

0,6 0,8 1,0 1,2

Hieu 6 3 3 keV

0,08472 0,08037 0,07635 0,07262

suat 92,6 keV

0,07735 0,07442 0,07164 0,06901

Ti so higu s u i t 6 3 3 kcV

1,28151 1,21575 1,15490 1,09852

92,6 keV 1,20322 1,15750 1,11430 1,07345

TAP CHI KHOA HOC DHSP TPHCM So 6(84) nam 2016

1,4 1,6 1,8 2,0 2,2

1

2,5

^ 2 , 1

^ k 3 , 0

0,06916 0,06595 0,06296 0,06018 0,05759 0,05402 0,05184 0,04882

0,06653 0,06417 0,06195 0,05983 0,05783 0,05501 0,05325 0,05077

1,04622 0,99764 0,95247 0,91040 0,87119 0,81720 0,78413 0,73843

1,03480 0,99821 0,96354 0,93068 0,89951 0,85569 0,82829 0,78971 Lam khdp dir lieu hieu suat theo mat dp mlu. Ta dupc kit qua:

Ddi vdi 63,3 keV: E(p) = 1,48463 - 0,36790p -(- 0,04005p' Ddi vdi 92,6 keV: E(p) = 1,34587 - 0,25371p -I- 0,02291p'

1

\ UnkWp

\ |:. ~ ™ " ^

\

Hinh 6. Sir thay dil hiiu suit

Iheo mdt do mdu dot vdi tia 63.3 keV Hmh 7. Sir thay dii hieu sudt Iheo mgt d§ mdu dii vol tia 92,6keV ma, ,?f^ "* "i,''*J " ' ' * ""^ '^ "'^•" ""^ '°^" ™ ^ "«" 1**P "^"a hi6u suit tiieo dupe^ t g r ' ^ " " '*"* '""^ '*"" "''" " ^ * ™ ^ "«" hi^u suit ed mlu r^fii!!^""-"".-"^ "'•* " ' " ' " ' ^ ' *P "^"6 ""^ '"•* « n tinh toan hidu suit eho 8 raau churn vo, ch.eu cao va mat dp khac nhm tir ham Iam khdp da xay dung vlsp sanh VOI tinh torn ti, ttiuc nghiem. Kit qua dupc ttinh bay ttpng Btog 4

TAP CHl KHOA HOC BHSP TPHCM Luu Tam Bit va tgk

Bang 4. So sdnh hiiu suit tinh todn tit he si hieu chinh tir hip thi/

vd hiiu sudt tinh tir phi thuc nghiim cimg hinh hgc va mgt do

Mau RGU-a RGU-b RGU-c RGU-d RGU-e RGU-f RGU-g RGU-h

Chien cao (cm)

1,3 1,5 1.9 1,7 2,4 2,6 2,1 1,1

Mat dd d/cm')

1,5496 1,5655 1,5900 1,5856 1,5379 1,5487 1,5981 1,5260

Hieu s u i t tinh tir lam khdp 633keV 0,08130 0,07524 0,06579 0,07004 0,05800 0,05498 0,06198 0,08889

92,«ki;V 0,07722 0,07219 0,06410 0.06779 0,05708 0,05439 0,06076 0,08329

Hieu suat tinh tir thuc nshiem 633keV 0,08265 0,07564 0,06612 0,06968 0,05910 0,05624 0,06259 0,08409

0,07754 0,07326 0,06429 0.06885 0,05516 0,05308 0,05994 0,08034

s a lech J

1,62%

0,53%

0,48%

0,51%

1,85%

2,25%

0,98%

5,71%

0,41%

1,46%

(>~WBI

3,49%rTi 2,46%

1,38%

3,67%

Ket qua cho ttiay ed sy phi, hpp tdt gia ttj hieu suit sau khi hipu chinh ttr hip ttiu bm quy ttinh xay dyng dupc ydi hiju suit tinh torn dupc ttuc tilp tir ttiuc nriiiem ddi vd, m m chuan RGUl vdi chieu cao mlu vk mjt dp ttiay ddi. Vay cd ttil sir dyng each hipu chmh ty hap thy da xay dyng d ttdn eho vipc tinh torn hoat do ^'»U ttuc tilp tir dinh 6 3 3 keVva 92,6 keV ttong mlu luong ttiyc ttiue phim. ' ' ' 3.2. /ip dung phan tich hogt dS'^'u tir miu luang thuc thuc phim sir dung photon gamma 63,3 keVvi 92,6 key ' «'"""""

Duoi day ap dung quy ttmh tach dinh va hieu chuin ty h i p ttiu da xay dung d t ^ c t r t ^ Jl, V^-^^'" ^* ' ' • * " ' " • ' ^ ^ - ^ P " ^ '"^h '* nhQng m l u i u ^ g ttiye ttiyc pham khae nhau nhu g,o, ttimg vit, khoai tay, cd sin, rau, ca, dupc tto hda va chuto b, frong hpp tty vdi ehieu cao mlu va mat dp mlu khac nhau Kit qua duoc cho ttong Bang 5.

Bang 5. Kit qud'phdn dch hoat di "'Utir 63.3 keVva92 6keV cua mgt so mdu luang thue thuc phim sau khi tdch nhiiu dong g6p cL ding vt "'Th vdo

dmh 63 key vai xde sudt phdt 0.263% vd sir dong gdp ciia ttaX"Uc vao dinh9keV Sai s l Ab, Mau

31 Tning

vjt 263 Khoai

tay 282

E (keV)

6 3 3 92,6 6 3 3 6 3 3

E(%) 8,45240 7,99650 6,28410 6,22480 6,56390

R, 0,00540 0,00990 0,00280 0,00430 0,00270

R , 0,00046 0,00533 0,00014 0,00168 0,00058

0,00500 0,00460 0,00260 0,00260 0,00210

1,66 2,87 1,15 1,59 1,08

1,52 1,34

0,97 0,85

0,08 0,06 0,12 0,06 0,07

TAP CHl KHOA HOC BHSP TPHCM

si 6(84) nam 2016

Sancu 154B Gao 43B Gao 360 Rau 347 Rau cai

368 ca 359 Rau 248 Gao

92,6 6 3 3 92,6 63,3 ,92,6 6 3 3 92,6 6 3 3 92,6 6 3 3 92,6 63,3 92,6 63,3 92,6

6,42690 6,95290 6,55610 731190 6,77130 5,87120 5,91120 4,05413 430809 5,67554 5,73306 5,29490 5,40793 6,83362 6,47372

0,00950 0,00125 0,00181 0,00525 0,00839 0,00377 0,00930 0,00762 0,01469 0,00776 0,01079 0,00252 0,00686 0,00249 0,00368

0,00702 0,00003 0,00019 0,00003 0,00034 0,00024 0,00293 0,00028 0,00366 0,00012 0,00148 0,00019- 0,00242 0,00002 0,00019

0,00250 0,00122 0,00163 0,00522 0,00805 0,00353 0,00636 0,07340 0,01102 0,00764 0,00932 0,00232 0,00445 0,00248 0,00349

3,45 0,46 0,50 1,84 2,22 1,64 2,82 4,82 6.11 3,50 4,35 1,22 2,27 0,93 1,02

0,92 0,45 0,44 1,83 2,13 1,54 1,92 4,64 4,59 3,45 3,75 1,12 1,47 0,93 0,96

0,04 0,11 0,08 0,24 0,10 0,30 0,12 0,77 0,26 0,52 0,22 0,23 0,10 0,22 0,06 Trong 66 e la hieu suit ghi gamma tai nSng lupng 63,3 keV v4 92,6 keV; R„ R,, R 14 tdc dp dim dinh phan tich chua trir nhilu, dinh nhieu, dinh phaT tich da ttii nhilu;

A v4 A|„ la hoat dp eua "'U tinh Uieo don vj (Bq/kg) khi chua hieu chinh va da hieu chinh dinh nhilu.

Dii lieu phan tich eho thiy cd su ddng gdp nhd ciia "^Th vao 63,3 keV ciia '''Th diing de phan tich "'U ngoji trit mlu 282. Tuy nhidn, cd sy ddng gdp kha Idn ciia tia X Ae vao dinh 92,6 keV. Ddng gdp nay Idn nhit 72% d mlu 282, 54% d mlu 31, 39% d mau 383. Ket qua tinh torn hoat dp '''U tir hai dinh 63,3 keV va 92,6 keV cua Th - con chau ttorc tiep eiia "«U eho ttiiy ed sy khae bidt Idn nhit 24% d mlu 359 20% o mau 360, 14% d mau 43B. Dilu nay cho thiy cin can nhic khi sir dung dinh 92^ke\ cua Th vi ttiam gia eua dinh nhilu tia X ^^«Ac qua ldn (die bidt khi ndng dp 23.^ ""-^ ™"' ^^^ ^'" "° ''« *°ng Idn trong viec xac dinh hoat dd rit thip cua

U ttorg mau mdi trudng.

4. Ket lu$n

Trong cdng ttinh nay, chiing tdi da sii dyng thufit torn tach dinh trong Gamma Vissionde tach dinh nhieu gamma 63,9 keV eua "^Th len dinh 63,3 keV ciia "'Th - U S't a'63 3 . V t o ' , ' ? . ' ' ' ' ^'^ ?"^ " ™ " ^ " ''""8 dl tinh torn hoat dp eu^

U tir tta 63,3 keV vi 92,6 keV eiia ddng vj con ehau ttuc tilp ciia "'U Qua trinh c r = ? ; "^b " *• •*' ' ^ «'' ".''" ^"^' 8*" ' " hai gmiraa nang luong ftlpn^

cung dupe nghien emi va danh gii ddi vdi quy trinh do ey thl. Tir dd gdp phin nang

TAP CHl KHOA HOC DHSP TPHCM Luu Tam Bat va tgk

TAI LIEU THAM KHAO

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3. Debertui, K. & Hehner, R.G. (1988), Gamma And X-Ray Spectrometry With Semiconductor Detector, Elsevier Science, Amsterdam.

4. Forte, M., Ruseoni R., Margini C , Ahbate G., Maltese S., Badalamenti P., &

Belhnzona S. (2012), Delerminnalion of uranium isotopes in food and environmetal sample by different technique: a comparalion. Division of Radiological Protection via Juvara 22, 9 Milmo. Italy; ARPA Lombaniia, Faculty of Physics. University of Milano, Italy.

5. James, M. Kaste, Benjamine, C. Bostick, & Arjun, M. Heirasattl (2006),

• "Detennirang Th-234 md U-238 in rocks, soils, md sediments via ttie doublet r gamma at 92.5 kcV", The Analyst, 131, 757-763.

6. MitcheU, N. & Harris, G. Limited (2013), "'A review of ttie behaviour of U-238 senes radionuclides in soils and pimts". Radiological Protection, 33(2):R 17-48 7. Nachab, A., Nourreddine, A., Benjelloun, M., Kihel S., Oster D., & Pape A. (2004),

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INgiy Tda soan nhin dugc bU: 02-02-2016: ngiy phin bign dinh gii: 12-3-2016 ngiy chSp nhin ding: 13-6-2016)