Vi vdy, nlu sir dyng phuong phdp ndy dl xdc dinh P-32 trong nuoc tieu nguoi phyc vy cho viec xdc dinh lilu chilu ti-ong se co y nghia thilt thuc hon vi mo rgng dugrc khd ndng xdc djnh li
Trang 1XAC DINH LifeU CHlfeU TRONG CUA P-32
vA DO NHAP NHAY LONG
N G U Y S N V A N H O N G ' , PHAM H O N G T H A I "
T6M TAT
Mdu nudc tiiu cua dSi tugng bj nhiim xg P-32 dugc thu gdp, xu ly hda hgc rdi do hogt dg beta trin he nhdp nhdy Idng ALOKA-LSC-6100 Sau dd, diing chuang trinh chuyin dung MONDAl 3.0 sS tinh dugc liiu hieu dung Kit qud nghiin ciru dugrc dp dung xdc dinh liiu cho nhdn vien birc xg d Vien Nehien ciru hgt nhdn Ngodi ra phuang phdp ndy ciing dugc so sdnh vdi phuang phdp do bdng Sngjim GM vd kit qud cho thdy nd cho
dg nhgy vd dg chinh xdc cao han khi ddi tugng bf nhiim xg P-32 & mure hogt dg thdp
Tir khda: xdc dinh lilu chieu trong, do nhap nhdy I6ng, lilu hi?u dyng (lieu todn than)
ABSTRACT
Determining internal dosimetry ofP'32for radiation workers by analysis
of the human urine and liquid scintillation counting
Urine samples from the subjects internally contaminated with P-32 are collected, chemically processed, and measured beta activity by the liquid scintillation counting system of ALOKA-LSC-6100 Then, effective doses are calculated by using the specialized software ofMONDAL3.0 The results are applied in dosimetry for the radiation workers in the Nuclear Research Institute Besides, this method is also compared with that of using
GM counter, and the result is shown it gives sensitivity and accuracy better in the case of subjects contaminated at low activity level
Keywords: internal radiation dosimetry, liquid scintillation counting, effective dose
(dose for whole-body)
1 Mfrdau
Dinh lieu chilu trong doi voi cdc dong vj ph6ng x^ phdt beta bdng phuong phdp
do nhdp nhdy 16ng dd dugrc nghien cuu vd dp dvmg pho biln tai nhilu phong thi nghiem tren the gioi [4, 5] T^i Vift Nam, phuong phdp ndy tuy con khd moi me nhung da dugrc ap dyng 6r mgt^sd co so nghien cuu trong linh vuc moi tiorong, tiuiy vdn ddng vi
do CO mgt so tinh chat uu vift cua phuong phdp ndy nhu dg nhay xdc dinh tdt, do chinh xdc ciia phuong phdp cao Vi vdy, nlu sir dyng phuong phdp ndy dl xdc dinh P-32 trong nuoc tieu nguoi phyc vy cho viec xdc dinh lilu chilu ti-ong se co y nghia thilt thuc hon vi mo rgng dugrc khd ndng xdc djnh lieu chilu ti-ong 6 muc boat do tiidp [3,
" TS, Vi$n Nghifen ci>u Hgt nhdn Dd Lgt
ThS, Vi$n Nghi6n cCi-u Hgt nhSn Dd Lgt
Trang 28] Xdc dinh lilu chilu trong d6i \6\ P-32 cho nhdn vien buc x^ dya tren phep phdn
tich nuoc tieu nguoi vd do tren hf nhdp nhdy long dugrc nghien cuu dp dyng ldn ddu tien tai Vif n Nghien cuu hat nhdn (Dd L^t)
D I loai trir nhiing dnh hu6ng bdi 1-131 hay nhOtig ddng vf ph6ng xa khdc hifn difn trong nuoc tilu ddn din sai so khi xdc dinh P-32, vi vdy cdn thilt phdi tdch P-32 ra khoi cdc ddng vi gdy nhieu nhu 1-131 (d Vifn, ti-ong cdc dgrt Ld phdn ung hat nhdn boat ddng thi thudng san xudt ddng thdi P-32 vd 1-131 dl cung cdp cho cdc bfnh vifn trong nudc) Ben canh dd, vifc tdch vd ldm gidu P-32 trong nudc tieu cdn gdp phan ldm tdng
do nhay va dg chinh xdc ciia phuong phdp ddi vdi P-32 Phuong phdp ndy cd tinh din tdch hda hgc vd ldm gidu ddng vi cho kit qud tot hon (mdu nudc tilu dugrc trgn trong dung dich chdt nhap nhdy nen ldm tdng hifu sudt phdt quang khi tin hifu tdi detector nhap nhdy Do dd hifu suat ghi cao, dat din 98%) so vdi phuong phdp su dyng hf do hoat do beta tdng cdng dimg ong dim GM dang dp dyng tai Vifn (phuong phdp nay
Cling phdi tdch hda hgc P-32 trong mdu nudc tilu, sau d6 do boat do tren hf do beta
tdng cdng dung dng dim chua khi GM nhung hifu suit ghi nhd, chi dat 20%) Hon nua, nhdn phdng xa P-32 dugrc ldm gidu len 10 lan, tuc Id khd nang phdt hifn P-32 tdt hon 10 lan so vdi luc chua tdch hda hgc
2 Thyc nghiem
2.1 Th u gdp vd ch uan bi mdu nu&c tiiu
Mau nudc tilu ciia cdc ddi tugrng khdng bi nhilm xa trong (P-32, 1-131, hay cdc dong vi phdng xa khdc tu qud trinh sdn xudt chat phdng xa hay xa tri bdng ddng vi phdng xa, ) dugrc thu gdp vdo cdc binh nhua sach loai 0,5 lit Sau dd cho them vdo 5
ml Focmandehit (Formol) dl bdo qudn trdnh bi bdc miii hdi sau mdt thdi gian luu mdu
DO kilm tra tren hf phd kl gamma phdng thdp dl xdc dinh hifn trang "phdng xa" cua mlu Sau do mdu dugc cho them mgt lugrng ddng vi phdng xa P-32 vd 1-131 bilt trudc hoat do DO boat do tren phd tren pho kl gamma phdng thap HPGe Canberra [2] dl xdc dinh sd dim tai dinh ndng lugrng 364,5 keV ciia 1-131 vd kit qud dugrc trinh bdy tren hinh 1
-1
"5 « »
4 0 0
300
-2 0 0 •
100 •
0 •
•
1
J,^
•
^
140O 1800 1800 2000
Ning lij-?ng (E/2)
ITmh 1 Phd gamma cua mdu nu&c tiiu cd chira P-32 vd 1-131
tru&c khi tdch hda P-32
Trang 32.2 Tdch hda P-32 trong mdu ntf&c tliu
2.2.1 Nguyen ly
Vifc tdch hda P-32 trong mlu nudc tilu dya tren nguyen ly sau [2,4,6]:
• Khi cd m^t ion Mg^* vd ion NH^ trong dung djch ammoniac, ion POl' tao nen
kit tiia mdu trdng NH4MgP04, khdng tan trong dung djch ammoniac nhung tan trong axit:
NH;+Mg'* + POl- = NH^MgPO, i
• Khi cd mdt mu6i molipdat (NH4)2Mo04 trong dung dich HNO3, ion POl' tao nen
kit tiia amoni photpho molipdat (NH4h [Pmoi204o] cd mdu vdng khdng tan trong axit
nitric nhung tan trong kilm vd dung djch amoniac:
^NHl-^PO]- + \2MoOl- •¥24H' =iNH,),[PMo^^OJ + \2H^O i
2.2.2 Quy trinh
Viec tdch P-32 ti-ong mau nudc tilu dugrc thyc hifn theo quy trinh sau [2, 4, 6]: 1- Lay 50 ml nudc tilu vao binh trdn 250 ml ThSm 1 gam KMn04 vd 4 ml H2SO4 (khoi lugrng rieng d = 1,84 g/cm^) dun tren bip cdch cat ti-ong 2-4 gid
2- Them dung djch O-xalic acid cho din liic dung dich mau mdt mdu, loc bd kit tiia (nlu cd) Them 1 ml dung djch chat mang P (15,3 mg P0"''4)
3- Them dung dich NH3 (d) cho din luc dung dich mau cd mdi trudng kilm
4- Them 5 ml thu6c tiiu Mg^"", khuiy 5 phiit, ly tdm hdn hgrp tdch tiianh hai phdn: Tiia mdu trdng vd dung dich
5- Hda tan tiia bdng 3 ml dung dich HNO3 3M (a)
6- Dun can phin dung dich vd chuyin vl mdi trudmg kilm bdng NH3, cho tilp 1
ml dung dich chit mang photpho vd lap lai budc 4 Lly tiia, bd dung djch Hda tan tiia bdng 3 ml dung djch HNO3 (b) Trgn hai phan (a) vd (b) vdi nhau
7- Them vdi gigt Aerosol O.T vd ldm Im dung djch bdng nudc ndng Them tu tir
30 ml dung dich thu6c thii molybdate, kholy khodng 5 phiit, ly tam, bd phdn nudc ndi Rua kit tiia hai ldn bdng 3 ml dung djch NH4NO3 0,5 M
8- Hda tan kit tiia bdng 5 ml dung dich NH4OH (d = 0,88 g/cm^)
9- Chuyin todn bg dung dich mlu vdo cuvet chuyen dyng, do boat do P-32 tren
hf do nhip nhdy Idng ALOKA-LSC-6100 trong tiidi gian 20 phiit/mlu
10- Tinh toan va hifu chinh boat do P-32
2.3 Xdc dinh d^ sgch phdng xa sau khi tdch hda
Sau khi thuc hifn quy trinh tdch hda P-32, mlu dugrc do tren phd kl gamma ti-ong cung dilu kifn: hinh hgc mlu, thdi gian do, khodng each giiia mlu va ddu dd cua hf do,
gidng nhu trudc khi thuc hifn tdch hda P-32 dh xdc dinh do sach phdng xa ciia mlu
Trang 4sau khi tdch (hinh 2) Kit qud do cho thiy sau khi tdch hda P-32 thi khdng cdn thiy
I-131 Dilu nay chung td quy trinh tach hda ddi vdi P-32 la tin cay, da loai bd dugc ddng
vi khdng quan tdm Id I-131
2" 500
I
^ 400
300
200
-100
wmm
20 220 420 620 820 1020 1220 1420 1620 1820
NSng 11/909 (E/2)
Hinh 2 Phd gamma cua mau nu&c tiiu sau khi tdch hda P-32 2.4 Xde dinh hiiu suat tdch P-32
Vifc tinh hifu suit tdch hda dua vao cdng thuc sau [5]:
H(%)=—.100
4)
(1)
Trong dd A la boat do xdc dinh dugc sau khi tdch hda va A© Id boat do ban ddu them vdo nudc tieu
Mlu nudc tilu da bilt boat do P-32 nhu d myc 1 Ap dyng quy trinh tdch hda d
muc 2 dh tdch P-32, sau dd mlu dugc do tren hf nhip nhdy Idng Ap dyng phuang
phdp ngoai suy hifu suit ghi diing mlu chuin C-14 dang dung dich ciia Nhdt Bdn (di kem theo hf do ALOKA-LSC-6100; do khdng cd dung dich chudn P-32 nen dung dung
dich chuin C-14 de ngoai suy hifu suit ghi) dh xdc dinh boat do ciia P-32 [2, 3, 8]
Tien hdnh quy trinh xac dinh hifu suit ghi 3 ldn tren 3 mlu nudc tieu khdc nhau Tir dd tinh duoc hieu suit tdch hda trung binh ddi vdi P-32 trong mlu nudc tilu Id (90 ± 3)% [2]
2.5, Xdc dinh gi&i han phdt hi^n
Gidi ban phdt hien LOD (Limit Of Detection) ciia nhdn phdng xa quan tam d muc tin cdy 95% dugc tinh theo cdng thiic sau [1,2]:
Trong do: LOD la gidi ban phat hien ciia hf do, B la sudt dem phdng, va t la thdi gian do
Trang 5Hoat do phdng xa cyc tieu cd thi do dugc MDA (Minimum Detectable Activity) dugc tinh theo cdng thuc sau [1, 2]:
LOD
H
Trong dd: MDA la ho^t dg phdng xa thdp nhlt do dugc (Bq) vd H Id hifu sudt ghi ciia hf do
Thu gdp 5 mlu nudc tilu sach "phdng xa" vd chudn bi mlu th\rc hifn nhu d muc
1 nhung khdng them P-32, 1-131 vdo mlu, thyc hifn vifc tach hda P-32 nhu quy trinh d myc 2 Mlu sau khi tdch hda, dugc hda tan bdng 5 ml NH4OH Do cdc mlu tren
hf do nhip nhay Idng trong thdi gian 20 phiit/mlu sd xdc dinh dugc LOD == 0,117 Bq Hifu chinh cdc qud trinh hda hgc nhu ldm gidu dong vi P-32, hifu suit tdch hda, thi
tich mlu do xdc djnh dugc MDA ~ 69,5 pCi/lit Tu dd xdc djnh dugc boat dg phdng xa
ciia P-32 tham nhdp vdo co thi qua dudng hit thd (sau mgt ngdy) tiieo phuomg phdp do nhip nhdy Idng vd phuong phdp do tren hf GM vd cho kit qud tuong ung Id 74 Bq va
440 Bq Ap dyng chuong trinh ddnh gid lilu chilu trong chuyen dyng MONDAL 3.0 [2, 7] se tinh dugc lilu hifu dyng (lilu todn thdn) theo hai phuong phdp tuong ung la 0,08nSvvdO,5|iSv[l,2]
2.6 Dfnh liiu chiiu trong cho mpt so doi tugrng tham gia sdn xudt P-32
2.6.1 Chudn bi vd do hogt dg mdu
Mlu nudc tilu ciia cac doi tugng tham gia sdn xult ddng vj P-32 dugc thu gdp sau mdt ngdy (sau ngdy tiln hanh sdn xult P-32) vdi thi tich tu 100 din 200 ml Xir ly
so bd vd tiln hdnh tdch hda P-32 nhu quy trinh 0 myc 2 Sau dd mlu dugc do boat do beta ciia P-32 bdng hai phuong phdp sau:
- Phuong phap do nhip nhdy long: thdi gian do 20 phiit/mlu, tinh boat do P-32 bdng phep ngoai suy hifu suit dimg mlu chuin dung djch C-14 [3, 8]
F F
- Phucmg phdp do diing dng dem GM [2, 5]
Kit qud xdc djnh boat do P-32 (Bq/ngdy) vd lugng xdm nhdp (Intake - ky hifu la I) theo dudng hit thd dugc neu trong bdng 1 [2, 6, 8]
Bdng 1 Kit xdc dfnh hogt dp P-32 trong mdu nu&c tiiu cda 2 doi tugrng trong 9 dgrt sdn xuat theo hai phuorng phdp (Ky hi^u: ong dim GM "GM*', nhdp nhdy Idng
"LSC'\ khdng xdc dfnh "NA*')
xuat P-32
Ngay do mau
Doi tugng
Hoat dg P-32 trong mau nudc tilu (Bq/ngay) va gia
trj I (Bq) cua 2 doi tugng Dgt Lo phan umg hoat dgng ngay 28/6-2/7/2010
Hoat dg P-32 (Bq/ngay)
GM 149,2 ±15,2
LSC 161,5 ±11,7
I(Bq)
GM 3,1E-H)3
LSC 3,3E-K)3
Trang 6Dgt Lo phan ung hoat dgng ngay 19-23/7/2010
2
3
25/7/2010
25/7/2010
27/7/2010 27/7/2010
T.Binh P.Thg
Ho^t dg P-32 (Bq/ngay)
GM 125,8 ±10,4 70,4 ±8,1
LSC 140,2 ±9,7 74,1±6,8
I(Bq)
GM 2,6E+03 l,4E+03
LSC 2,9E+03 1,5E-H)3 Dgt Ld phan Omg hoat dgng ngay 9-13/8/2010
Ho^t dg P-32 (Bq/ngay)
GM 60,5 ± 7,2
LSC 55,6 ±5,4
I(Bq)
GM l,2E+03
LSC 1,1E-K)3 E)gt L5 phan iimg ho?t dgng ngay 6-11/9/2010
Hoat dg P-32 (Bq/ngay)
GM 210,4 ±17,2
LSC 203,7 ±12,7
I(Bq)
GM 4,3E+03
LSC 4,2E-K)3 E)gt Lo phan ung hoat dgng ngay 4-8/10/2010
6
7
11/10/2010
11/10/2010
14/10/2010 14/10/2010
T.Binh P.Thg
Hoat do P-32 (Bq/ngay)
GM 35,6 ± 6,3 47,3 ±6,5
LSC 32,1 ±4,1 52,5 ± 8,4
I(Bq)
GM 7,2E-K)2 9,7E+02
LSC 6,6E-K)2 l,lE+03 E)gt Lo phan umg hoat dgng ngay 8-12/11/2010
8
9
14/11/2010
11/11/2010
17/11/2010 17/11/2010
T.Binh P.Thg
Hoat do P-32 (Bq/ngay)
GM 179,8 ±17,2 193,7 ±17,9
LSC 186,5 ± 14,3 210,5 ± 16,9
1(1
GM 3,7E+03 4,0E+03
3q) LSC 3,8E-K)3 4,3E+03 Dgt Lo phan ung hoat dgng ngay 3-7/01/2011
10
11
9/01/2011
9/01/2011
12/01/2010 12/01/2010
T.Binh P.Thg
Hoat dg P-32 (Bq/ngay)
GM
NA
NA
LSC 34,2 ±5,2 30,9 ±4,7
I(Bq)
GM
NA
NA
LSC 7,0E4{)2 6,4E+02 Dgt Lo phan ung ho?it dgng ngay 17-21 / 01 /2011
12
13
23/01/2011
23/01/2011
26/01/2011 26/01/2011
TBinh P.Thg
Hoat dg P-32 (Bq/ngay)
GM
NA
NA
LSC 25,8 ±4,2 28,7 ±5,4
I(Bq)
GM
NA
NA
LSC 5,3E+02 5,9E-H)2
Trang 7Dgt Ld phan ung hoat dgng ngay 14-18/02/2011
14
15
20/02/2011
20/02/2011
23/02/2011 23/02/2011
T.Binh P.Thg
Ho^tdg P-32 (Bq/ngay)
GM _j
65,3 ± 8,5
NA
LSC 76,4 ±9,3 22,6 ±4,1
I(Bq)
GM l,3E+03
NA
LSC l,6E+03 4,7E+02
r^.'
2.6.2 Ddnh gid liiu chiiu trong doi v&l P-32
Tu gid trj boat do P-32 xdc djnh dugc (Bq/ngdy), tinh thdi dilm nhan phdng xa thdm nhdp vdo co thi theo dudng hd hip Id I ngdy (thdi dilm tu liic sdn xult P-32 din
llic lly mdu nudc tilu), su dyng phdn mIm MONDAL 3.0 se tinh dugc lugng boat d^
thdm nhdp theo dudng hit thd trong (bdng 1) vd lilu hifu dyng gdy ra do hit phdi P-32 Kit qud tinh lieu tdng cgng ddi vdi 15 ldn thu gdp mlu ciia 2 ddi tugng dugc rieu trong bdng 2, trong dd ky hifu D (^Sv) la lilu hifu dyng (theo cdc dgt thu gdp mdu) cua tung ddi tugng bj nhilm P-32 Tir bdng 2 thiy rdng, kit qud n h ^ dugc lilu hieu dyng (Id lilu tich luy khi mgt lugng P-32 xdm nhdp vdo co thi dang tiic thdi, da dugc chuong trinh MONDAL 3.0 xii ly vd tinh todn, cd tinh tdi ylu td phan ra vdt ly vd dao thdi sinh hgc [1]) cd gid trj ndm trong ddi tuong ung Id 0,79 - 4,80 nSv theo phuong phdp do dung dng dim GM vd 0,51 - 4,80 jiSv theo phuomg phdp do nhip nhdy Idng
Bdng 2 Kit qud tinh liiu hi^u dung D (pSv) ddng chuang trinh MONDAL 3.0
theo hai phuorng phdp (GM vd LSC)
TT
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Ngdy sdn xult P-32 4/7/2010 25/7/2010 25/7/2010 15/8/2010 14/9/2010 11/10/2010 11/10/2010 14/11/2010 11/10/2010 9/01/2011 9/01/2011 23/01/2010 23/01/2010 20/02/2011 20/02/2011
Ngdy do mdu 7/7/2010 27/7/2010 27/7/2010 17/8/2010 16/9/2010 14/10/2010 14/10/2010 17/11/2010 17/11/2010 12/01/2010 12/01/2010 26/01/2011 26/01/2011 23/02/2011 23/02/2011
Ddi tugng T.Binh T.Binh P.Tho P.Tho P.Thg T.Binh P.Tho T.Binh P.Thg T.Binh P.Tho T.Binh P.Tho T.Binh P.Tho
D (nSv)
Phuong phdp GM 3,40 2,80 1,60 1,40 4,80 0,79 1,10 4,10 4,40
NA
NA
NA
NA 1,50
NA
Phuong phdp LSC 3,60 3,20 1,70 1,20 4,60 0,72 1,20 4,20 4,80 0,77 0,70 0,58 0,65 1,70 0,51
Trang 8Tu cdc gid trj lilu hieu dyng xdc djnh dugc d bang 2 cho thiy tit ca cdc gid trj
nay rit thlp (nlu lly gid tri lilu trung binh trong mdt thdng nhdn vdi 12 thdng dh dugc
lilu tdng cdng trong mgt ndm) so vdi lilu gidi han cho phep hdng ndm (20 mSv/ndm) [1, 2] Dilu nay chiing td cdc doi tugng cd bj nhilm xa trong khi tilp xiic vdi P-32 nhung vdn dam bdo vl mdt an toan biic xa
2.7 So sdnh kit qud dinh liiu
Trong dilu kifn phuong phdp xii ly hda va lam gidu mlu nhu nhau, phuong phdp
do dung dng dim GM vd phuong phdp do nhip nhdy Idng cho kit qud djnh lilu cd su sai khdc khdng qua 14% (hinh 3) Tai mgt sd dgt sdn xult cila thdng 1 vd 2 ndm 2011,
do cdc ddi tugng bj nhiim P-32 d miic thap thlp nen khdng xac djnh dugc lilu bdng phep do dung dng dim GM, tuy nhien cd thi phdt hifn dugc bdng phep do nhip nhdy Idng Dieu ndy cho thiy, phuomg phdp do nhip nhdy Idng cho do nhay cao hon so vdi phucmg phdp diing dng dim GM khi ddi tugng bj nhilm xa P-32 d miic boat do thlp
Do thi so sanh lieu toan than
5 5
2
D Oo long beta
Q Oo nh^p nhay Idng i
i H a i
10 11 12 13 14 15
T7ii> t y theo phu'ong phap
ITinh 3 So sdnh liiu hieu dung ciia P-32 do bdng phuong phdp do dimg ong dim
GM vd phuong phdp do nhdp nhdy long
3 Ket luan
•
Tir kit qua thuc nghifm tren thiy rdng phuong phap djnh lilu bdng phep do nhip nhdy Idng cd do nhay vd do chinh xdc cao so vdi phuong phdp do dung dng dem GM
Vifc dp dyng kit qud nghien ciiu dh xdc dinh lilu cho hai ddi tugng (la nhdn vien biic
xa) lam vifc true tilp tren day chuyin sdn xult P-32 d Vifn trong mdt sd dgt sdn xult P-32 cho thiy lilu tdng cgng trung binh theo nam la nhd hon lilu gidi ban cho phep
Tii do, cd thi dp dyng quy trinh tren dh xdc djnh lilu chilu trong cho cdc nhdn vien biic
xa cd tilp xiic vdi ngudn phdng xa hd P-32 d cdc co sd biic xa khdc ciing nhu cho cdc bfnh nhdn chin dodn vd dilu trj bdng P-32 d cac co sd y tl
Trang 9TAI L i f u THAM KHAO
1 Nguyen Vdn Hiing (2003), Nghiin cicu dinh liiu chiiu trong trin ca s& phuang phdp
do todn thdn vdphdn tich nudc tieu ngu&i, Ludn an Tiln sT Vdt ly, Bg GD & DT
2 Pham Himg Thdi, Nguyen Vdn Hiing vd cgng sy (2011), Nghien ciru dp dung quy
trinh xdc dinh P-32 vd I-l31 trong nu&c tiiu bdng phuang phdp nhdp nhdy Idng phuc vu dinh liiu chiiu trong, Bdo cdo tdng kit de tdi d p Co sd ndm 2010, Vifn
NLNTVN
3 D.L Horrocks (1974), Application of liquid scintillation counting, Packard
Instrument Co., Inc Japan
4 IAEA (2000), Indirect methods for assessing intakes of radionuclides causing
occupational exposure Safety reports series No 18, Vienna, Austria
5 IAEA (1989), Measurement of radionuclides in food and environment Technical
report series, No 295, Vienna, Austria
6 NCRP (1987), Use of bioassay procedures for assessment of intenal radionuclide
deposition Report No 87, Bethesda, MD, 20814, UK
7 N Ishigure et al (2000), MONDAL 3.0, a personal computer program for monitoring
to dose calculation, NIRS, Japan
8 Y Kobayashi (1987), Liquid scintillation analysis, science and technology,
Packard Instrument Co., Inc., Japan
(Ngdy Tda so?n nh$n dirge bdi: 26-4-2011; ngdy ch4p nh$n dSng: 13-6-2011)