Vd1052-20142011412.pdf

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XAC DINH HOAT D O P H 6 N G XA CUA P-32 TRONG N\f6C Tifeu N G i r o n BANG PHlTOfNG PHAP NHAP NHAY LONG

PHUC v y DINH LIEU CHIEU TRONG

PHAM HUNG THAI, NGUYEN VAN HUNG, LE VAN NGQC, HOANG VAN NGUYBN Vi?n Nghien cuu hgt nhdn, Dd Lgt

Abstract: The determination of P-32 radioactivity in the hirnian urine by liquid scintillation counting was first applied in the field of intemal radiation dosimetry at the Nuclear Research Institute. Urine samples firom the subjects internally contaminated with P-32 were collected and sample preliminary processing was conducted with formaldehyde. 50 ml of the samples was taken, chemically separated and eruiched 10 times by the precipitation with amonium phosphor molypdate. The chemical separation efficiency of 90% was obtained. Then the processed samples were measured by using the liquid scintillation counting system of ALOKA 6100.

This method involving chemical separation and enrichment results in better efficiency of 98% compared with that of 20% of the gross beta counting system being used at the Institute. In addition, ten-time eruichment of radionuclides of P-32 leads to its lower limit of detection by ten times.

Based on the counting efficiency of liquid scintillation in combination with enrichment process of samples of interest, we have experimentally determined the sensitivity level of 69.5 pCi/L for P-32. This method enables to detect the P-32 intake level of 74 Bq through respiratory system (after one day) compared with that of 440 Bq by using the gross beta counting system of GM counter. Based on the specialized intemal radiation dosimetry software of MONDAL-E, the effective dose was calculated to be 0.08 |iSv for the liquid scintillation method and 0,5 jiSv for the gross beta counting one. Due to its advantages, it will be applied to assess the intemal dose for the subjects working with unsealed sources of P-32.

Tir khoa: Nhdp nhdy ldng, dinh lieu chieu trong, liiu hi?u dung

I. MO DAU

Xac dinh boat do phong xa bing phuong phap nhAp nhay long da duoc nghien cuu va ap dung ph6 biln tai nhiSu phong thi nghiem tren th^ gioi. Tai Viet Nam phuong phap nay tuy con kha moi me nhung da dugc ap dung tai mot s6 ph6ng thi nghiem, trung tam nghien cih I trong ITnh vyc nghien cuu moi trucmg, thuy van dong vi phong xa do eo mgt so tinh chat uu I viet cua phuong phap nay nhu do nhay xae dinh t6t, do chinh xae cua phuong phap cao...Vi vay neu su dung phuong phap nay de xac dinh P-32 trong nuoc tieu phuc vu cho dinh lieu chi6u trong se co y nghTa thiet th\rc hem vi noi rgng dugc kha nang dinh lilu chilu trong cr gioi ban thap.

De loai trir nhimg anh huong boi I-I31 hay nhung d6ng vi phong xa khac hien di^

trong nuoc tilu dan din sai s6 khi xac dinh P-32, vi vay cin thilt phai tdch P-32 ra khoi cac dong vi gay nhilu nhu 1-131. Ben canh do viec tach va lam giau P-32 trong nuoc tieu con gop phan lam tang do nhay xac dinh cua phuong phap ddi voi P-32.

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Hgi nghi Khoa hgc vd Cdng nghe hgt nhdn todn qudc Idn thu IX, Ninh Thudn 18-19/8/2011 413

II. THUC NGHIEM

1. Thu gop va chuSn bi mau nude tieu

Mlu nuoc tieu ciia cac doi tugng khong bi nhiem xa trong (P-32, 1-131, ... hay cac dong vi phong xa khac tir qua trinh san xuat chat phong xa hay xa tri bSng d6ng vi phong xa, ...) dugc thu gop vao cac binh nhua sach lo^i 0,5 lit. Sau do cho them vao 5 ml Focmandehit (Formol) de bao quan tranh bi hoc miai hoi sau mpt thoi gian luu mlu. Do kilm tra tren he ph6 kl gamma phong thap de xac djnh hien trang "phong xa" cua mlu. Sau do mlu dugc cho them mgt lugng dong vi phong xa P-32 va I-13I biet truoc. Do lai tren pho gamma de xac djnh s6 dim tai dinh nang lugng 364,5 keV cua I-131 (Hinh 1).

1

•o 5 0 0 •

4 0 0 •

300 -

200 •

100 •

Hinh 1 :Ph6 g a m m a cua mliu nLrac tieu co dong vj P trub-c khi l^ch hoa

•

r l

364,5

_.^ . »

200 400 600 800 1000 1200 1400

- 3 2 va 1-131

1600 1800 2000 Nang li/ong (E/2)

2. Tach hoa P-32 trong mau nirorc tieu 2.1. Nguyen tic

• Khi CO mat ion Mg^* va ion NH^ trong dung dich ammoniac, ion POl~ tao nen Icet tiia mau tring NH4MgP04, khong tan trong dung djch ammoniac nhtmg tan trong axit:

NH; +Mg''+ POl' = NH, MgPO, i

• Khi CO mat mu6i molipdat (NH4)2Mo04 trong dung dich HNO3, ion PO]' tao nen IcSt tua amoni photpho molipdat (NHi)3 [Pmoi204o] co mau vang khong tan trong axit nitric nhtmg tan trong kiem va dung dich amoniac:

7,NH; + PO]- +nMoO^- + IW = (NH,),[PMo,fi,„] + l2Hfi i 2.2. Quy trinh

1. Lay 50 ml nuac tiSu vao binh tron 250 ml. Them 1 gam KMn04 va 4 ml H2SO4 (d = 1,84) dun tren bep each cat trong 2-4 gio.

2. Them dung dich 0-xalic acid cho dSn luc dung dich mau mjt mau, loc bo kfa tua (neu co). Them 1 ml dung djch chit mang P (15,3 mg P0^"4).

3. Them dung djch NH3 (d) cho din liic dung djch mau co moi tnrang kiem.

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414 Hdi nghi Khoa hgc vd Cdng nghi hgt nhdn todn qudc lan thu IX. Ninh Thudn 18-19/8/20}}

4. Them 5ml thu6c thu Mg^^, khuiy 5 phut, ly tam hon hgp tach thanh hai ph§n: Tua mau trang va dung dich.

5. Hoa tan tua bing 3 ml dung dich HNO3 3M (a)

6. Dun can phin dung dich va chuyen ve moi truong kiem bang NH3, cho tilp 1 ml dung dich chat mang photpho va lap lai buoc 4. Lay tua, bo dung dich. Hoa tan tua bSng 3 mi dung dich HNO3 (b). Nhap hai phan (a) va (b).

7. Them vai gigt Aerosol O.T va lam Im dung dich bing nuoc nong. Them tir tir 30 ml dung dich thu6c thu molybdate, kholy khoang 5 phut, ly tam, bo phin nu6c noi. Rica kk tua hai lan bang 3ml dung dich NH4NO3 0.5 M.

8. Hoa tan kit tiia bing 5ml dung dich NH4OH (d = 0,88).

9. Chuyin toan bg dung dich mlu vao cuvet chuyen dung, do hoat do P-32 tren h? do nhip nhay long ALOKA-LSC-6100 trong thoi gian 20 phut/mlu.

lO.Tinh toan va hieu chinh hoat dg P-32.

3. Xac djnh do sach phong xa sau khi tach hoa

Sau khi thuc hien qui trinh tach boa P-32, mlu duge do tren pho ke gamma phong thip HPGe Canberra trong cung dilu kien: hinh hgc mau, thoi gian do, khoang each giiia ra§u va diu do, ... nhu truoc khi thuc hien tach hoa P-32 de xac dinh do sach phong xa cua mau sau khi tach (Hinh 2).

s 1 2 0

TOO -

8 0 -

6 0

-tt) -

2 0 -

H i n h 2 : P I T 6 g a m m a cCra m 3 u n u ' 6 ' c t i 4 u c 6 < 5 6 n g v j P - 3 2 v ^ 1 - 1 3 1 s a u k h i tech h 6 a

J 2 0 0 4 0 0 6OO 8 0 0 1 0 0 0 1 2 0 0 1 4 0 0 1 6 0 0 1 BOO 2000 N£ing WnqtnQ&Z

4. Xac dinh hieu suat tach P-32 trong nirorc tieu Tinh hieu suat tach hoa dua vao cong thuc:

H{%) = ~xlOO 0)

Troiig do A la boat do xac dinh duge sau khi tach hoa va Ao la hoat do ban dau them vao nuoc tieu.

Mlu nuoc tieu da bilt boat do P-32 nhu 6 Muc I. Dung qui trinh tach hoa o Muc 2 de t^ch P-32, sau do mau dugc do tren he nhip nhay long Aloka 6100. Dung phuong phap ngoai suy hieu suit voi mau chuan C-14 do Nhat Ban san xuit dl xac dinh hoat do cua P-32. Tien

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Hgi nghf Khoa hgc vd Cdng ngh? hgt nhdn todn qudc lan thir IX, Ninh Thudn 18-19/8/2011 415

hanh qui trinh xac dinh hieu suit 3 lin trSn 3 mau nuoc tieu khac nhau. Tu do tinh dugc bieu suit tach hoa trung binh d6i voi P-32 trong man nuoc tilu la (90 ± 2)% [1].

5. Xac dinh gioi han phat hien

Gioi ban phat hi^n LOD (Limit Of Detection) cua nhan phong xa quan tam a muc tin c^y 95% dugc tinh theo cong thiic:

WD =2Zl±i.«VBl /

Trong do: LOD la gioi ban phat hien ciia thiet bj do, B la suit dim phong, va t la thoi gian do.

Hoat do phong xa thap nhat do dugc MDA (Minimum Detectable Activity) dugc tinh theo cong thurc:

MDA=^ (3) H ^ ^

Trong do MDA la hoat do phong xa thap nhat do dugc (Bq) va H la bieu suat do ciia thilt bi.

Thu gop 5 mau nuoc tilu sach "phong xa" va chuan bi mau thue hien nhu o Muc 1 nhung khong them P-32,1-131... vao mau, thuc hien tach boa P-32 ap dung qui trinh tach hoa a Muc 2. Mau sau khi tach hoa, dugc h6a tan bing 5 ml NH4OH. Do cac mau tren he do nhap nhay long trong thoi gian 20 phut/mau se xae dinh dugc LOD ~ 0,117 Bq. Hieu chuart den cac qud tinh hoa hoc nhu lam giau dong vi P-32, hieu suat tach boa, th^ tich mlu do xac dinh dugc MDA = 69,5 pCi/lit. Tir do xac dinh dugc boat do phong xa ciia P-32 tham nhap vao co thi qua ducmg hit tho (sau mgt ngay) theo phuong phap nhap nhay long va phucmg phap do t6ng beta (dimg 6ng dim GM) tuong ung la 74 Bq va 440 Bq. Ap dung chuong trinh danh gia lilu chilu trong chuyen dyng MONDAL-E se tinh dugc lieu hieu dung toan than tuong iing theo hai phuong phap la 0,08 ^Sv va 0,5 p.Sv.

6. Dinh lieu chieu trong cho mgt so doi tugng tham gia san suat F-32 6.1. Chudn bj vd do ho^t do mdu

Mlu nuoc tilu cua cac doi tugng tham gia san xuat doiig vi P-32 dugc thu gop 1 ngay sau khi san xuat, thi tich 100 din 200 ml. XOr ly so bg va tiln hanh tach boa P-32 nhu qui trinh o Muc 2. Sau do mau dugc bang hai phuong phap sau:

- Phuong phap nhIp nhay long trong thoi gian 20 phiit/mau, tinh hoat do P-32 bang phuong phap ngo^i suy hieu suat dung mau chuan dung dich C.

- Phuong phap dinh boat do P-32 bing do tong beta.

Kit qua xac dinh hoat do P-32 (Bq/ngay) va lugng xam nhap (intake) theo duong hit th6 dugc neu trong Bang 1 [1,4, 5].

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416 Hgi nghi Khoa hgc vd Cdng ngh^hgt nhdn todn qudc Idn th^IX, Ninh Thudn 18-19/8/201}

Bdng 1. Kit xdc dinh hogt do P-32 trong mdu nuoc tiiu cua 2 doi lufmg trong 6 d0 sdn xudt theo hai phuang phdp (Tdng beta -T.B. vd nhdp nhdy Idng-N.NL.) TT Ngay san

xuit "P Ngay do

mau D6i tugng

Hoat dp P-32 trong mau nuoc tiSu (Bq/ngay) va gid trj intake (Bq) cua 2 dSi tugng Dgt Lo phan ijmg ho?it dpng ngay 2^16-21112010

1 1 4/7/2010 1 7/7/2010 I T.Binh

Hoat dp P-32 (Bq/ngay) T.B.

149,2 ± 15,2 N.N.L.

161,5 ±11,7

Intake (Bq) T.B.

3,lE+03 N.N.L 3,3E-H)3 Dijrt Lo phan ling ho^t dgng ngiy 19-23/7/2010

2 3

25/7/2010 25/7/2010

27/7/2010 27/7/2010

T.Binh P.Thp

125,8 ±10,4 70,4 ±8,1

N.N.L.

140,2 ±9,7 74,1± 6,8

Intake(Bq) T.B.

2,6E+03 l,4E+03

N.N.L 2,9E+03 l,5E+03 Dot Lo phan iing hoat dong ngay 9-13/8/2010

4 1 15/8/2010 1 17/8/2010 | P.Thp

60,5 ± 7,2 N.N.L.

55,6 ± 5,4

Intake (Bq) T.B.

l,2E+03 N.N.L.

l,lE+03 Dot Lo phan ling boat dong ngay 6-11/9/2010

5 1 14/9/2010 1 16/9/2010 | P.Thp

210,4 ±17,2 N.N.L.

203,7 ±12,7

Intake (Bq) T.B.

4,3E+03 N.N.L 4,2E+03 Dot Lo phan ling hoat dOng ngay 4-8/10/2010

6 7

11/10/2010 11/10/2010

14/10/2010 14/10/2010

T.Binh P.Thp

35,6 ± 6,3 47,3 ± 6,5

N.N.L.

32,1 ±4,1 52,5 ± 8,4

Intake(Bq) T.B.

7,2E+02 9,7E+02

N.N.L.

6,6E+02 l,lE+03 Dgt Lo phan iing hoat dpng ngay 8-12/11/2010

8 9

14/11/2010 11/11/2010

17/11/2010 17/11/2010

T.Binh P.Thp

Hoat dg P-32 (Bq/ngay) T.B.

179,8 ±17,2 193,7 ±17,9

N.N.L.

186,5 ±14,3 210,5 ±16,9

Intake(Bq) T.B.

3,7E+03 4,0E+03

N.N.L 3,8E+03 4,3E+03 Dgt Lo phan ung hoat dpng ngay 3-7/01/2011

10 11

9/01/2011 9/01/2011

12/01/2010 12/01/2010

T.Binh P.Thp

- -

N.N.L.

34,2 ±5,2 30,9 ±4,7

Intake(Bq) T.B.

- .

N.N.L 7,0E+02 6,4E+02 Dgt Lo phan (ing hoat dpns nsav 17-21/01/2011

12 13

23/01/2011 23/01/2011

26/01/2011 26/01/2011

T.Binh P.Thp

- .

N.N.L.

25,8 ±4,2 28,7 ± 5,4

Intake(Bq) T.B.

_ _

N.N.L.

5,3E+02 5,9E+02 Dgt Lo phan ling hoat dgng nsav 14-18/02/2011

14 15

20/02/2011 20/02/2011

23/02/2011 23/02/2011

T.Binh P.Thg

65,3 ± 8,5

-

N.N.L.

76,4 ± 9,3 22,6 ±4,1

Intake(Bq) T.B.

l,3E+03

.

N.N.L.

l,6E+03 4,7E+<I2 Ghi chii: - khong xac dinh

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Hdi nghi Khoa hgc vd Cdng ngh? hgt nhdn todn qudc Idn thir IX, Ninh Thudn 18-19/8/2011 417

6.2. Bank gid liiu chieu trong ddi vdi P-32

Til gia tri boat do P-32 xac dinh dugc (Bq/ngay), tinh thoi dilm nhan phong xa tham nhap vao co the theo duong ho h i p la 1 ngay (thoi diem tiJr liic san xuit P-32 din luc liy m l u nuoc tieu), sii dung phin mem MONDAL-E tinh dugc gia tri tham nhap theo duong hit tho trong Bang 1 va lieu toan than gay ra do hit phai P-32 trong Bang 2.

Ket qua tinh lieu tong cgng doi voi 15 lan thu gop mau cua 2 d6i tugng dugc neu trong Bang 2, trong do ky hieu DTT (pSv) la lieu hieu d\mg toan than (theo cac dot thu g6p mlu) ciia timg doi tugng bi nhilm P-32. Tir Bang 2 thay r i n g kit qua nhan dugc lilu toan than CO gia tri n i m trong dai tuong iing la 0,79 - 4,80 ^iSv theo phuong phap do t i n g beta va 0,51 - 4,80 nSv doi vdi phuang phap do nhIp nhay long.

Bdng 2. Kit qud tinh liiu todn thdn diing chuong trinh MONDAL-E cho hai phuang phdp (Tdng beta vd nhdp nhdy ldng).

TT

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Ngay san x u i t ^ P 4/7/2010 25/7/2010 25/7/2010 15/8/2010 14/9/2010 11/10/2010 U/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

Ngay do miu 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

Doi tugng T.Binh T.Binh P.Tho P.Tho P.Thp T.Binh P.Tho T.Binh P.Tho T.Binh P.Thg T.Binh P.Thp T.Binh P.Thp

Dl Phuong phap

t6ng beta 3,40 2,80 1,60 1,40 4,80 0,79 1,10 4,10 4,40

_ _ _ _

1,50

-

T (HSV) Phucmg phap nhap

nhay long 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 Ghi chu: - khong xac djnh

Gia tri Heu toan than xac dinh dugc tir Bang 2 cho thay tat ca cac gia tri nay rat thap so v6i gioi han qui dinh 20 mSv/nam [2], Dilu nay noi len ring cac d i i tugng bi nhiem xa P-32 thap, van dam bao vS mat an toan biic xa.

7. So sanh ket qua djnh lieu

Trong dieu kien phuong phap xii ly hoa va lam giau mau nhu nhau, phuang phap do ting beta va phuong phap nhap nhay long cho kit qua dinh lilu co su sai khac khong qua 14% (Hinh 3). Tai m6t s6 dot san xuat ciia thang 01, thang 02 nam 2011 do cac d6i tugng bi

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418 Hdi nghj Khoa hgc vd Cdng ngh? hgt nhdn todn qudc Idn th& IX, Ninh Thudn 18-19/8/201}

nhiem P-32 thap, phucmg phap do tong beta khong xae djnh dugc tuy nhien do bing nhip nhay long eo the phat hien. Dilu nay cho thiy phuonp phSp nhIp nhay long cho dg nh^y vk do tin cay cao hon so voi phuong phap ting beta khi d6i tugng bi nhilm x^ P-32 6 miic thip.

GA th| so sinh N^u todn than

Tliii' t y theo phuong phSp

Hinh 3. So sdnh liiu P-32 todn thdn do bdng phuang phdp tdng beta vaphuangphdp nhdp nhdy long

III. KET LUAN

Tir ket qua thuc nghiem trSn thiy rang phuong phap dinh lieu bang phep do nh^p nhay long co dg nhay va do tm cay cao. Co the ap dung de dinh lilu chilu trong cho cac nhan vien biic x^ co tiep xiic voi nguon phong xei ho P-32 o eac co so biic xa cung nhu cho ck bfnh nhan chin doan va dieu tri bing P-32 6 c^c eo sd y te.

TAI LIEU THAM KHAO

[1] P.H. Thai v^ c0ng su, "Nghien cihi xac lap qui trinh xac dinh P-32 va I-I3I trong nudrc tieu bang phucmg phap nhap nhdy long phuc vu dinh lilu chilu trong cho nbSn vien biic xa", Bao cao ting kit dl tai d p Co so nam 2010, Vifn NLNTVN, 2011.

[2] N.V. Hung, "Nghien ciiu dinh lilu chilu trong tren co sd phuong phap do toan thSn v£l phan tich nuoc tieu ngudi", Lu^n an tiln sT V^t ly, Bg GD & DT, 2003.

[3] D.L. Horrocks, "Application of liquid scintillation coimting", Packard Instrument Co., Inc., 1974.

[4] Y. Kobayashi, "Liquid scintillation analysis, science and technology", Packard Instrument Co., Inc., 1987.

[5] NCRP, "Use of bioassay procedures for assessment of intenal radionuclide deposition", Report No. 87, Bethesda, MD, 20814, UK, 1987.

[6] IAEA, "Indirect methods for assessing intakes of radionuclides causing occupational exposure". Safety reports series No. 18,2000.

[7] IAEA, "Measurement of radionuclides in food and environment", Technical report series, No. 295, Vienna, Austria, 1989.