Hàm lượng của các đồng vị (k40, u238, TH232, cs137 ) trong môi trường (đất, thực vật) của trường ĐHKHTN ĐHQG hà nội ở hoà lạc trong những năm 2002 2004

DAI HOC QUOC GIA HA NOI TRUCiNG DAI HOC KHOA HOC TL'NHIEN HAM LirONG CUA CAC DONG VI (K^", V''\ TH^'", Cs''\ ) TRONG MOI TRLrC)N(; (DAT, THUC VAT) CUA TRUC)NG DHKHTN - DHQ(i HA NOI O HOA LAC TRONC; NHUNG NAM 2002 ^ 2004 MA SO : QT - 03 - 04 Chii tri de tai: PCJS.TS Dang Hiiv Hven Cac can bo iham gia: TS Pham Dmh Khang (Pho chu tn) ThS Dang Phmvng Nam TliS Nguyen Tlic Nghia Cac sinh \'icn nam ihu'lu" (Xu\cn Sctn Nga) IIA \ ( ) s :()f)4 BAO CAO TOM TAT Ham liTong cua cac dong vj ( K"^, U''^ Th''^ Cs'^' ) moi tnrcmg (da't, thirc vat) cua tnrcmg DHKHTN - DHQG Ha noi a Hoa Lac nhOng nam 2002 ^ 2004 Mas6':QT-03-04 b Chu tri de tai: PGS TS Dang Huy Uyen c Cac can bo tham gia: l.TS Pham Dinh Khang ThS Dang Phuong Nam ThS Nguyen The Nghia Cac sinh vien nam thii tix (Xuyen, Son, Nga) d Muc tieu va noi dung nghien curu: Muc tieu cua de tai la thu gom duac cac so Ueu thuc nghiem dau tien cac mSu moi tru5ng (dat, thuc vat) cua cac dong vi K^^ U^^^ Th^^^ Tren ca s6 danh gia phong biic xa tu nhien (sua't lieu bu:c xa tu nhien) cua moi tnrcmg Noi dung nghien cuii cua de tai la: - Do trucmg biic xa gamma a hien tnrcmg nam 2001 ^ 2002 - Do suat lieu burc xa hien trucmg - Lay mSu dat thuc vat ve phong thi nghiem cac he gamma cua cac CO sa CO he phong thap chuan chinh xac cua Vien nghien ciJu hat nhan Da Lat, cua Trung tam nghien ciru - Vien Vat ly Ha noi e Cac ket qua dat duac: Do tnrcmg xa va xac dinh ham luong cua K, U^^^ Th^^^ cac nam tir 2000 -^ 2004 tren ban theo hinh ve 01 tren manh dat cua trucmg DHKHTN DHQG Ha noi a Tir hinh ve 02, 03, 04, 05 ve su phan bo so xung theo tan so xuat hien chung ta nhan duac: kenh tong cong so dem tap trung tuang doi cao a khoang dem 3000 -^4000, tan suat xuat hien tuong ling la 52% cac khoang dem khac thl tan suat xuat hien ciia so dem la nho, gia tri bring 4% kenh Kali, so dem tap trung kha cao a khoang dem 200 - 300 tan suat xuat hien len den 92% kenh Uran, tan suat xuat hien a khoang dem 200 H300 la 72% kenh Thori toan bo so dem tap trung khoang dem 100 ^ 200 khoang dem hep han, tap trung so dem cao nhat khoang tii 140 ^ 160, tan suat xuat hien ciia so dem khoang la 52% Noi chung truong xa Gamma tan man b Ham lirang trung blnh K , U-^^ Th"'- c6 dat a Hoa Lac nhCrng nam 2000 ^ 2004 dugc trinh bay bang so 13 tren hinh ve so 01 la: Nam 2001 H- 2002 bing may GAD 2002 ^ 2003 bang gamma phong thap PTN Chua[n bang K.O (4,48 %) 2003 4- 2004 bang ph6 gamma phong thap a PTN Chuain bang K 0( To measure the gamma radiation in the field in 2001-2002 > To measure the radioactive dose at the sites in the field > Samples of soil and vegetation collected in the environment for determining radioactive concentration by low- level gamma spectrometers that belong to Nuclear Physics Institute, Dalat and Nuclear Department, Physics Institute, Hanoi Result: Determination of K, U and Th contents during 2000 -20004 at the sites in the campus of Hanoi National University in Hanoi mapped in figure a) As can be seen in figures 2, 3, and , the distributions of the pulse frequency are shown that: The values of total counts focus on the range of 3000 - 4000, rate of the occurence is 52% Out of this range, rate of the occurence is small, only 4% At Kali and Uran peak, the values of counts focus on the range of 200 300, rate of the occurence increase to 92% and 72%, respectively At Thori peak, and all values of counts, which focus on the range of 100- 200, are narrower range than those at Kali and Uran peak Majority of the count values concentrate on the range of 140-160 and the rate of the occurence is 52% In general, the gamma radiation field is scattered b) Average contents of K, U and Th in soil in Hoa Lac (that mapped in fig.1) during 2000 -20004 are shown in tab 13 K (%) U (ppm) Th (ppm) Cs (ppm) j 2001-2002 by GAD 12 2002-2003 by low- level gamma spectrometer, standard sample (K20-4.48%) 2002-2003 by low- level gamma spectrometer, standard sample (K2O - 4.48%) At the majority of the sites measured in the field (5 sites in the first year 10 sites in the second year 10 and 15 sites in the third year), K average contents are under the detection limit of GAD-12; Also, Kali contents of samples collected at these sites, which were measured in Lab, are in good agreement with those of other reports For example Kali contents in Hanoi in 1990, in Nghia Do, Cau Giay in 2000 and Hoa Binh hydroelecthc power in 2000 were estimated are 4% [2], 2,08 % [3] and 2.28 % [4], respectively Average Uran contents, which measured in the sites during three year vary from to ppm , agree with results of other reports (the results obtained in Cau Giay in 2000 and In Hanoi in 1990 are 6.92 ppm and ppm respectively.[2.3]) Average results of Thory content, which measured at the sites during three year vary from 14 to 22 ppm , are in good agreement with results of other reports (the result obtained in Cau Giay in 2000 and in Hanoi in 1990 are 17 ppm and 18.7 ppm respectively.[2.3]) However, the results of K, U and Th contents are larger than those obtained in Hue Determination of the radioactive dose measured directly in the field and based on K U and Th contents of environmental samples during 2000 20004 at the sites in the campus of Hanoi National University mapped in figure ^ There are two methods for estimating radioactive dose as follow: To measure radioactive dose directly by using the dosimeter which keeps 1m above the ground at the sites in the field ^ To calculate the external radiation level based on K U and Th contents of environmental samples by formula ( 11.1.1) [8] Averaged results of the external radiation level obtained by the dosimeter dunng years I m = 9- 13 u R/h; average results of the external radiation level obtained by calculating during years are: I c = 9- 12.7 \.i R/h These results agree with those which measured at Hoa Binh hydroelecthc power (9.89 (.1 R/h) [4], in Hue city (8.25 \.i R/h) [9], in Vinh city (11 u R/h) [9] Average result of dose equivalent H, is 70.07 ± 2.74 mRem/year Generally, values of dose equivalent H, which vary in narrow ranger (55.05-83.04 mRem/year)[9] are smaller than those in the whole U.S (45-105 mRem/year) Average result of dose equivelent H obtained is under the permissible dose given by the International Commission on Radiological Protection [10] (0.5 mRem/year) [10] Therefore, the radioactivity in the environment human being health does not cause the Determination of the radioactivity of vegetation samples in the campus of Hanoi National University in Hoa lac during 2000 -20004 Samples of vegetation (tea leaves, gum leaves and chrysopogon) collected in the environment during years for determining radioactive concentration by low- level gamma spectrometers that belong to Nuclear Physics Institute, Dalat and Nuclear Department Physics Institute, Hanoi Radioactive concentration K^° U^^^ Th^^^ Cs-137, Be-7 by a method metho given [7] The results are shown in tab, year • sample tea leaf gum leaf chrysopogon K40 UZJB" Th T7T Cs Be The gamma spectral of the vegetation samples is shown in fig.9 The results obtained are similar to those of similar vegetation samples found by other authors in the whole world For example Cs-137 in Thai nguyen tea leaf in Hanoi market in 1980 is 0.01 Bq/g, fresh tea leaf in Hanoi market in the same time is 0.0003 Bq/g, Cs-137 and K-40 in dried bamboo samples in Hanoi market in 1980 are 0.02 Bq/g and 0.732 Bq/g respectively MUC LUC Ma dau Ban nghien ciJu Do trucrng xa va xac dinh ham lugng cua K^°, U^^^, Th^^^ Xac dinh suat heu thuc nghiem d hien truofng va so sanh v6i suat Ueu dugc tinh tren co s6 so Ueu cua K, U , Th moi trudng 20 Xac dinh hoat rieng cua cac dong vi phong xa cac mlu thuc vat dac trung a khu dat truing DHKHTN Hoa Lac 24 Ket luan va kien nghi 42 Tai Ueu tham khao 43 Phu luc c6 Ih^ cam nhan dugc, tha'p dd'n muc ma anh huong cua no d6i vdi sue khoe chi o mure t6'i thi^u Tai nan xay tai nha may didn hat nhan Chemobyn 26/04/1986, ca dd'n luc lugng don dep Chemobyn thi lidu buc xa ma hg bi chid'u kh6ng gay bat cii m6'i nguy hi^m hay riii ro sue khoe nao cho gia dinh hg hay nhung ngucri c6 quan hd vdi hg Cac lidu xa cung nho tdi muc kh6ng dd lai di truydn gi cho thd' hd chau hg Theo kd't qua lidu, lidu trung binh ciia nhung ngucri tham gia dgn dep la 120 mSv Tu nam 1988 gia tri ciia li6u dugc giu a mure gi6i han binh thucmg hang nam la 50 mSv Trong ICRP khuyd'n cao rang Uiu ca nhan trung binh kh6ng ndn vugt qua 500 mSv Sau su c6' xay chi co 31 nguoi tir vong thl li^u xa ma hg nhan dugc tu 4000 ^ 6000 mSv Con nhiing ngucri mlc bdnh buc xa trdm trgng phai vao bdnh vidn thi da h6i phuc va xua't hidn sau vai t u ^ dd'n vai thang Khi b ngoai trdi chung ta bi chid'u m6t lugng buc xa binh thucmg Tuy thu6c vao dia di^m chiing ta s6'ng, burc xa tu nhidn cho Udu la khoang 1-^2 mSv m6i nam, tnrcmg hgp ngoai Id la khoang 10 -^20 mSv/nam Nhung hdu xa nhu thd' la kh6ng thd' tranh khoi M6t thuc te cho tha'y nguoi van s6'n^ va t6n tai tir thd' hd tdi thd'hd khac Tit chung to chung ta dang sd'ng m6t m6i truong dam bao mure lilu chid'u cho phep Li^u khuyd'n cao ciia ICRP dd'i vdi dan chung xa co so hat nhan la 50 mSv hay la rem cho sud't doi nude ta v ^ dd nhidm phong xa mdi trucmg dugc theo doi le te nhirng nam 1950, 1960, sau dd vi chien tranh hdn midn Idn bi dut doan Mai tdi nam 1980 cho tdi mdi cd kd' hoach nghidn curu mdi trucmg nhidm phong xa ca'p nha nude, nhung tdi h^u nhu da bi lang qudn vi nguoi ta nghi rang o nuoc ta chua bi nhidm xa Idn dd it ngudi quan tam Song xin dugc luu y day la va'n dd m6i truang co tinh chat toan cau va cd xu the ciia toan thd' gidi dang lien tuc phat tri^n vd linh vuc va d6'i luu khdng khi, trongcac dai duong chac chin m6i trucmg Vidt Nam cung se bi anh hudng Khu da't Hoa Lac vira dugc nha nude phan cho dai hgc qud'c gia Ha N6i, nai day se la trung tam khoa hgc va ph6' ^t tinh ciia thii dd; han nua chua cd s6 lieu vd nhidm xa mdi truong nen chiing tdi :hpn khu da't mdi dd nghien cuu phuc vu cho vide phat tridn cua DHQG irong lai va cung ca'p cho tinh Ha Tay mdt tap sd lieu mdi ma tir trudc tdi chua li quan tam Do cung la muc tieu cua cdng trinh dang quan tam II Phuong phap va ket qua thuc nghiem II.l May suSit lieu Inspector M^y su dung mdt dng dd'm Geiger-Muller dd' ghi nhan buc xa 6ng dd'm Geiger- Muller phat xung didn mdi buc xa chuydn qua dng va gay idn hoa 6ng ddm Geiger-Muller phat xung didn mdi buc xa chuyen qua dng va gay i6n hoa O chd' dd ^SV/h, may lam xua't hidn muc buc xa tu 0,01 dd'n 1000 May suat li^u da dugc c h u ^ san Vdi may da trdn 25 di^m, d dd cao ri sau da chuyen d6i tu ^SV/h nhu d hinh ve sd a c kd't qua true tid'p dugc md ta d bang sd Bing s61: Su^Tl lie'u true ti^p trtn 25 dl^m nhir trtn hinh ve s61 Blim l.(^R/h) 9,12 ±0.34 7.98 ±1.14 9.12 ±0.34 7.98 ±0.34 7.98 ±0.34 9.12 ±0.34 7,98 ±0,34 6.84 ±1,14 7,98 ±0.34 10.26 ±1,14 7.98 ±0,34 10.26±0,80 9.12 ±1,14 10,26 ±1,14 10.26 ±0,80 11,40 ±0,34 9,12 ±0,34 10.26 ±0.80 11,40 ±0,80 7,98.0.80 9,12.1,14 18,24.0,34 10,26.2,28 10,26.0,34 9,12.1.14 9,58.0,72 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 TB i HOA BiNH • 15 • • 2S T* 21 22 • • 23 • 2t • • Hinh sd Phan bd cua suat lidu I^ theo tan sd xuat hidn va sd didm dugc minh hoa d bang sd Bing s6 PhSn b6 cua su^t IIAu IB Iheo tSn s6 nil hl^n v i stf aim Gliti1cualB(^R/h) TJin stf xulft hl^n Stf ditfm 8^7 7+8 8+9 S9 + 10 10 + 11 11+12 12 + 13 13 + 14 14 + 15 15 + 16 16 + 17 17 + 18 0.04 0.28 >18 0.04 7 0 0 0 0.28 0.28 0.08 0 0 0 Bi^u 66 phan b6 suat lieu l^ theo t ^ s6' xua't hidn va s6 diim duac minh hoa hinh ve s6' 76- 1 51 4- \ j • Series I ; 3- 2- • 1- U I•finh ve sd Qua day chiing ta tha'y suat lidu ddu tap trung cao d khoang - ^ ^ - 10 iR/h; t ^ sd suat hidn cua suat lidu d cac khoang dd la 28% Suat lidu bidn ddi fong khoang rdng tu ( H- 19 ^R^ )' dd suat lidu d khu luu giu igudn phong xa chu^n qud'c gia chi tu ( -^ 10 |IR^ ) 11 ] Didu dd chung td cd su ^^c v^ tinh chat da't tai khu vuc khao sat .khoang gia tri tir 12 -^ 18 ^xR/h thi 5ua[t li6u khdng xua't hidn Chi ridng didm 22 thi suat lidu tang nhanh ( 18,43 ^R/h ), ham lugng Uran, Thori cung cd nhirng gia tri khac thudng, c ^ dugc ki^m tra tid'p nhi^u ^ mdi cd kd't luan chfnh xac dugc Gia tri trung binh ciia suat hdu dugc la 9,58|iR/h Trong dia Vat ly mdi truong thudng xac dinh hdu hidu dung tuang duong H Li^u hidu dung tuong duang H ti Id vdi suat li6u chid'u va dugc xac dinh bang c6ng thiic : H = K.I Q.N.t Trong dd : K la hd sd phu thudc vao m6i truong, khdng khf K = 0,869 I la suat lidu chid'u biic xa gamma dugc xac dinh bang thuc ngliidm Q la he sd pham chat ciia buc xa, vdi biic xa gamma Q = N la hd sd tfnh cho cac yd'u td mdi trudng, vdi khdng khf N = t la thai gian chid'u Nd'u I bang ^R/h thi H dugc tfnh mrem/nam Cac kd't qua vd lidu hidu dung ciia 25 didm dugc trinh bay d bang sd Bing %6 Lltu hl^u dung tirong duong flltfm Hdnrem/nim) 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 62,06 ±2.4 55.05 ±2.32 01.73 ±2.49 Trung blnh 60.62 ±2,58 59.78 ±2.55 63.75 ±2.48 58.30 ±2.12 S49.01±2.04 56.74 ±2.12 72,70 ±2,73 56.32 ±2.48 73.18 ±2.84 67.12 ±2,43 72.79 ±3.36 72.46 ±2.86 80.63 ±3,24 69.25 ±2.76 73,63 ±2,75 83.04 ±3.45 59.20 ±2,31 71.98 ±2,64 140,26 ±5,41 82,02 ±3.05 86,11 ±3,24 64,08 ±2.32 70,04 ±2,74 Nhln chung lidu hidu dung bien d6i khoang hep (55,05 H- 83,04 mrem/nam ), nam khoang bien ddi cua gia tri tren toan nude My (45^105 mrem/nam) [2] Ridng cd didm sd 22 thi lidu hidu dung tuang duong Idn tdi 140,26 mrem/nam Trong dd lidu trung binh ca nhan d Phap tu ngudn phong xa tu nhidn udc tfnh la khoang 250 mrem/nam [3] 11.2 m k6 gamma phong th^p cua vien nghidn cmi hat nh^n Da Lat Detector Ge (HP)_PGT co thd tfnh nhay 71 cm\ hidu sua't ghi tuang ddi 15,1%, ty sd peak/comfoton laf 42, dd phan giai la 1,92 KeV tai 1332 KeV cua «Co Detector dugc dat budng giam phdng kfch thudc 50x50x50cm, vdi cac p che chan (tfnh tu ra) gdm mm Al, mm Cu, cm Fe, va 10 cm Pb sidu sach phdng xa, phdng tfch phan ciia he thd'ng tu 100 ^2000 KeV bang 1,7 cps, giam 100 Ifin so vdi phdng ngoai budng TiT tidn khuyd'ch dai RGl duac khuyd'ch qua khd'i khuyd'ch dai ph6 Silena 7613, sau dugc bidn d6i tfn hidu sd titn ADC Fast — 7070, luu tru trdn khd'i MCD CMTE 8K kdnh, khd'i dugc ghep ndi vdi IBM —^PCva truy nhap qua chuong trinh~PC MCA Ph6 dugc luu tru irfen PC va xir ly bang cac ph^n mim GANAAS, GAMMAN — cac p h ^ mdm chuydn diing ciia IAEA phan tfch ph6 gamma So dd khd'i dugc md ta d hinh ve s6' De-tec-t0 TKD KDP ADC MCD PC Nguan nudi Hinh ve So dd khdi ciia he gamma phdng tha'p Hoat d6 ridng cua mdt sd nguydn td phdng xa mau la che, cay com ngu6i va mSu la cay bach dan thu gop 24/11/2001 dugc trinh bay trdn bang sd M6t dang ph6 gamma ciia la che dugc minh hoa trdn hinh ve sd Bang sd Hoat dd ridng ciia mdt sd ddng vi phdng xa mau thuc vat thu ?6p tai Hoa Lac thang 11/2001 BA'ng vj Mau \i Bach d^n (Bq/kg tifffl) Mau cdy com ngufil (Bq/kg tirol) Mdu \i che (Bq/kg tuoi) aiy 0,873 ± 0,096 0,954 ±0,105 5,126 ±0,623 '"Th 0.910 ±0,109 1,070 ±0,118 5.735 ± 0.679 34.19 ±1,33 56,35 ±6,63 30.32 ±3,70 5.733 ±1.183 6,377 ±1,775 11.383 ±1,763 0,135 ±0,035 0,079 ± 0,027 0,047 ± 0,026 «K 'Be '"Cs Cac kdl qua duac ii'nh loan mac d6 im c^y 95^( 'Gia Ihiei ^'"U iranp thai can bang phong xa voi "'Ra So dem s 5< » 8^keV ' L-:3^-^Ra-:26) 239keV Pb-212 296keV.Pb-214 ajSir.eV Ar-7?S 352keV Pb-214 as a: TO • ^09keV B I - : M 1> •a> ^ t-^ o •c se ro *- J* rb> ^" rs c- ^^ » TO B9 —• CU 30 Z2>t — u^ rj O' •-n '-/» '.U 911kcV Ac-:28 9