31(4)[CD],299 J(;6 Tap chi CAC KHOA HOC VE TRAI DAT 12 2009 NGHIEN CLTU DAC DIEM DI T H U 6 N G KHI PHONG XA PHUC VU TIM KIEM PHAT HIEN QUANG AN VA DANH GIA MLTC DO 6 NHI6M MOI TRUONG TREN MOT SO M 6[.]
Trang 131(4)[CD],299-J(;6 Tap chi CAC KHOA HOC VE T R A I DAT 12-2009
VA D A N H GIA MLTC D O 6 N H I 6 M M O I TRUONG
LE KHANH PHON NGUYEN THAI SON
N G U Y I N V A N N A M , N G U Y S N ANH TUA^
I M d DAU Nude ta thudc mien nhiet ddi khi hau ndng dm
mua nhieu, lap ddt da be mat chiu tae ddng phong
hod xam thirc manh me Bdi vay da phdn cac md
quang ndi chung va cac md quang phdng xa ndi
rieng thufte dang quang "dn", cac than quang thudng
bj chdn viii dudi eae tdng phii bd rdi Do khi phdng
xa, dae biet la khi radon cd kha nang Ian truyen di
xa khdi ddi tupng sinh ra ching nen phupng phap
khi phdng xa la phupng phap phdng xa cd chieu sau
nghien cuu (chieu sau phat hien quang dudi tdng
ddt phil) Idn nhdt Cac ddi dirt gdy, dap vd dia chdt
tao thanh dudng ddn khi eiing gay ra cac di thudng
khi phdng xa
Mudn nang eao hieu qua dp dung cac phuong
phap khi phdng xa trong nghien ciru dja chdt va
tim kie'm quang phdng xa, edn thie't phai lam sang
td eae dae die'm cila di thudng khi phdng xa tren
cac ddi tupng dia chdt khdc nhau, lira chpn dupe
thie't bi ky thuat ed dd nhay, dd tin eay eao, dua ra
dupe tieu ehudn dia chdt - dia hod - phdng xa phan
biet dupe dj thudng quang (lien quan vdi eae md
chira chdt phdng xa) vd di thudng phi quang (lien
quan vdi cac da ed hoat dd phdng xa cao va cac
ddi duft gdy dap vo dia chdt)
Trong dieu tra mdi trudng cdn lam sang td dae
die'm phat tan vd tieh tu radon trong Idp khi quyen
sat mat ddt tu cac ddi tupng dia chat khae nhau (phu
thude vao loai md quang, cdu triie dia chdt) va dae
diem bie'n thien ndng dO khi phdng xa theo thdi gian,
theo nhirng bie'n ddi cila thdi tie't Tir dd dua ra quy
trinh quan trde mdi trudng gdm lira chpn thie't bi,
mang ludi, thdi gian quan trdc, xii ly tdi lieu nham
xae dinh chinh xae ndng dd khi phdng xa trong khdng
khi phuc vu viec tinh lieu ehie'u trong qua dudng hit thd va danh gia mire dp 6 nhiim khi phdng xa, mot trong nhirng dang d nhiem phdng xa nguy hiem nhdt kho phdng tranh nhdt
Nhirng dieu ndi tren ehirng td tinh cap thiet cila d^ tai nghien cUu vd cung la npi dung dupe de cap trong bai bao nay
II NGHIEN C i r u XAY DUNG M O T SO MO HINH T H A N QUANG CHL/A CHAT PHONG XA
C U A N U d C T A
De lam sang td eo sd khoa hpe ap dung phuong phap khi phdng xa trong cong tac tim kieni nhdt la trong tim kie'm phat hien cac than quang an va danh gia 6 nhiem mdi trudng, chung toi da tien hanh xay dung mo hinh than quang ehUa chat phdng xa dien hinh etla nude ta Id quang ddt hie'm va sa khoang ven bie'n, ddng thdi tinh toan xae dinh eae di thudng phdng xa tren mo hinh quang
1, Mo hinh than quang sa khoang titan
Theo eae tai lieu hien cd cua Lien doan Dia chat V (1984), Nguyen Kim Hoan (1985), Nguyen Tie'n Thuan (1998), Vd Ngpc Anh (2004), quang sa khoang titan cd ham lupng khong ddng deu, phan
bd tap trung d eae bai cat gdn cac eo, vinh, d phdn phia nam hoac bdc cac mom nho ra bien noi cd dieu kien de hinh thanh cac than quang dat gia tri cdng nghiep
Tir sd lieu cua cac tai lieu ke tren, co the mo hinh hda cac than quang sa khoang ven bie'n mien Trung nhu sau : cac than quang ed chieu day trung binh tu 1,4 m de'n 4,5 m bao hda theo tia gamma
Trang 2(chieu ddy bao hda theo tia gamma h > 1 m), be rdng
40 m - 1,000 m, chieu dai tu 800 m de'n 8.000 m
deu bao hda theo tia gamma va cd the coi nhu than
quang ed dang Idp nam ngang keo dai vo han
Chi trir md An My va Xuong Ly, tai eae md khae,
mot bd phan than quang bi phu vdi be ddy tang phu
trung binh tir hang chuc de'n 70 cm, chieu ddy tdng
phu cue dai tdi 4,0 met
Trong cac than quang cd mdi tuong quan ty le
thuan giua ham luong quang ilmenit vdi ham lupng
cac khoang vat phu nhu zircon vd rutin Trong zircon
ham lupng cac nguyen td phdng xa U^Og khoang
0,011 - 0,014 %, Th02 khoang 0,0108 - 0,0128 %
Trong monazit ham lupng Th203 chie'm ty le tU
2,31 de'n 6,52 % trung binh 3,79 % Ngudi ta da
xac dinh trong cac ddi sa khoang ham lupng thori
bie'n thien trong khoang 0,0009 - 0,018 %, Quang
sa khoang vdi gia tri ham lupng bien ciia ilmenit la
10 kg/m^ cd hdm lupng q-n, ~ 0,002 %, quang dat
ham lupng cdng nghiep (>50kg/m ) ed q-n, > 0,01 %
Nhu vay md hinh die'n hinh ddi vdi cac than
quang sa khoang ven bie'n mien Trung la than quang
chira chdt phdng xa dang Idp nam ngang, cac kich
thudc iing vdi trudng hpp niia khdng gian birc xa
vo han Quang Id tren mat ddt hoac bi phu cd chieu
ddy tu hang chuc centimet de'n 3- 4 m thanh phdn
chil ye'u la cat hat nhd
2 Mo hinh than quang dat hiem chira chat
phong xa
Tai nhieu vung cua nude ta nhu Lai Chau, Lao
Cai, Yen Bai ed cac md ddt hiem vdi trir lupng Idn
thudc loai md trung binh va Idn tren the' gidi Trong
quang ddt hie'm cd chira cac chat phdng xa Th, U
Quang ddt hie'm cila nude ta thudng cd dang tui,
dang d, dang mach hoac dang thau kinh Ham lupng
tdng oxid ddt hie'm TR2O3 tu mdt vdi phdn tram de'n
tren 30 %, trung binh 10 % Ham lupng Thori trong
da't hie'm vd phong hod la 0,0199 % de'n 0,0441 %,
trong ddt hie'm quang gde la 0,0087 % de'n 0,0204 %,
ham lupng urani trong ddt hie'm tu 0,001 % de'n
0,01% Cac than quang ed be ddy til 2 m de'n 7 m,
trung binh 3-4 m, chieu dai tU hang chuc tdi hang
tram met
Tuang tu nhu ddi vdi quang sa khoang ven bie'n,
md hinh than quang ddt hie'm cd hi rdng hang chuc
met, chieu dai tdi hang tram met, chieu ddy trung
binh 3-4 m, cue dai tdi 7 m ed the' coi nhu la Idp
quang nam ngang keo dai vd han
3 Tinh toan sir phan bdnong do khi phong xa tren mo hinh lop quang
Viec tinh toan sir phan bd ndng dp khi phdng xa dupe thue hien chung cho hai ddi tupng sa khoang ven bie'n va quang ddt hie'm dudi dang md hinh mdi trudng 2 Idp nam ngang vd han, lap thir hai la Idp quang phdng xa nam phia dudi vdi cac tham sd : ham lupng chdt phdng xa q2, ndng dd khi phdng xa N2, mat dd P2, he sd Id rdng ri2, he sd khue'eh tan D2, a()2 - luong eman tu do thoat vao 1 cm da trong
1 giay, (Bq/cmls), he sd eman hda Kc2 Ldp thir nhdt la ldp phu nam d phia tren cd chieu ddy h va
cac tham sd N|, pi, r|i, D|, K^ {hinh 1)
-Nkh
N„
N|, r|i.Pi Di,Kci
qo
N
N„
• d z
Q T
O-i N-> n ? 0-) D?
Hinh 1 Md hinh tinh sir phan bd ndng dd khi
phdng xa trong ldp eman hda vd han (ldp quang phdng xa) va trong trdm tich phil Ndng dp khi phdng xa N trong mdi trudng cd
dp Id rdng r| bie'n ddi chi theo hudng true z Phuong trinh vi phan can bang lupng khi phdng xa trong ldp
dx cd dang sau : - :
trong dd : ddng khi phdng xa di qua dien tich S cua ldp dz
Q = DSdN/dz-I-VNTIS ' (2) a„ = N,;v = K,qp} 3,7.10"' (3) Sir phan bd ndng dp khi phdng xa theo chieu
sau Idy mdu z dupe xac dinh bang each giai phuong trinh vi phan (1) [2, 6, 7]
a) Tri/dng hap be day tang ptiCi ti >10cd the coi nhu h ^ 00
Ndng dp khi phdng xa tai dd sau Idy mdu z dupe tinh theo cdng thire [2, 6) :
Trang 3N = Nf,e -J|(.-.) (4)
trong dd No - ndng dd khi phdng xa tai be mat ldp
quang
1 Wo=N2»
trong dd N2x - ndng dd khi phdng xa trong Idp quang
bao hda
N Rn
2« l,2.IO-'K,i,„.q„.K,^
ri I
/V]i = 8 , l l 0 X T n q n , ^ ^
(6)
n I
qu (%), q-n, (%) - ham lupng urani, thori trong ldp
quang, K^Kn, KCTH - he sd eman hda cua radon va
toron, Kcb - he sd can bang phdng xa eila ddy urani,
p - mat dd, r| - dp Id rdng eila quang
d = D,b,/D2b2 ; h^^^XrjJD^
b) Be day tang phu hOru han (h <10 m), nong
do khi phong xa tai do sau z tinh theo cong thitc
[2,6]:
N = No
Sh
Sh
\D^
[i^i
(7)
Tir ede cdng thire (4) va (7) chang nhiJng cd the'
tinh dupe ndng dd khi phdng xa tai eae dp sau lay
mdu khi khae nhau ddi vdi md hinh ldp quang bao
hda ma edn du bao dupe chi^u ddy tdng phil vdi
thdng tin tien nghiem ve ndng dp khi phdng xa tren
be mat ldp quang No, gia tri he sd khue'eh tan D va
gia trj ndng dd tdi thie'u Nn,i„ ma thie't bi khi phdng
xa ed the' xae dinh dupe mOt each tin eay
khi
c) Nong dp khi phong xa trong moi tntdng khong
Tir md hinh cac Idp quang va ddt phtl nhu d hinh
1, cd the' tinh dupe ndng dd khi phdng xa trong khong
khi tren mat ddt Nkh(O) vd d dd eao H each mat ddt
Nkh(H)
/V,,(0) = / V „ J ^
V A
N,,(H) = N,,(0)e -Jl"
(8)
(9) trong dd A - he sd khudy ddng khi tai mat ddt cd gia
tri lO' emVs, khi H = 30-50 m thi A=I0''-10'cmVs
Bang ly thuye't va thirc nghiem ed the xac dinh ndng dd radgn trong khdng khi sat mat ddt hang nghin Idn nhd han gia tri cua nd N, cila nd trong mdi trudng ddt da Khi khdng cd gid thi ndng dp radon trong khi quye'n giam cham theo dd eao, cdn ndng dd toron giam rdt nhanh va hoan toan triet tieu
d khoang each khdng qua 10 cm each mat ddt |2, 6|
KET QUA AP DUNG
/ Tim kiem phat hien quang sa khoang an
theo dae diem di thirdng khi phong xa
De danh gia kha nang tim kiem phat hien quang
dn, phuang phap khi phdng xa diing may phd alpha hien dai RAD-7 do My san xudt (may ed kha nang xae dinh rieng biet ndng dp eae khi phdng xa Rn va
Tn theo phd alpha ciia chung) dupe trien khai tren 5 khu md sa khoang titan mien Trung Tren cac md nay
da tie'n hanh khao sat gamma mat ddt ty le 1:25000, phuong phap khi phdng xa tren hang nghin diem dupe tie'n hanh ddi vdi mot sd mat cat dae trung ciia tirng md (bao gdm cac mat edt qua cac khu vue ed than quang sa khoang Ip ra mat ddt, than quang sa khoang bi phil bdi ldp bdi tieh mdng va than quang
sa khoang bi phil bdi Idp phil tuong ddi ddy) Dp sau Idy mdu khi 60 - 80 em Tren m6t sd mat cat da
cd cac Id khoan vd hao Idy mdu phan tich kiem tra Tren mat edt dia chdt phdng xa BN65 vung Ban
Nham Phu Yen {hinh 2), ed the thdy than quang sa
khoang BN4 Ip ra mat ddt Tai eae doan mat edt quang Id ra mat ddt d trung tam va canh phai, deu phat hien cac di thudng cudng dp gamma, di thudng ndng dp khi phdng xa Tn va Rn Gia tri di thudng cudng dd bire xa gamma bie'n thien trong khoang 20-30 ^R/h, gia tri dj thudng ndng dd T^ bie'n thien trong khoang 2000-3500 Bq/m^ Idn gdp 1,5-2 Idn gia tri di thudng ndng dp Rn, /V^^"~ 1500-2200 Bq/m\ Tir eae gia tri cudng dp birc xa gamma, ndng dd khi phdng xa Tn vd Rn, dung cong thire (8) de dang xae dinh dupe quang ed ham luong thori qTi,> 0,01 %, ham lupng urani qu > 0,002 % tuong irng vdi loai quang sa khoang titan ed ham lupng cdng nghiep
> 50 kg/ml Cac tinh toan ly thuye't chi rd, khi quang bi phil, da't phil hdp thu va lam suy giam cudng dp bire xa gamma Ndng dd cac khi phdng xa eung bi giam ddn khi Ian truyin tir than quang di qua ddt phil len mat ddt Khi radon cd chu ky ban ra Ti<n = 3,8 ngay, thdi gian sdng trung binh T = 5 ngay, nen khi mdi
Trang 44000-1 V U N G B A N N H A f M - B I N H 0 ! N H 4000
\ A
I \ / \ / \
A A
Ig (flR/h
3
[ ^
DuOng bi^u di^n g i ^ tri
nong (Jo Rn
D u u n g bj^u di^n gt^ tn
n 6 n g d O T n
DutJng bieu di§n gia tri
c u n n g d p ph6ng x a Ig
CHI DAN
T r ^ m tfcti ti6n hap bi^n - gi6: c ^ t mdu x ^ m , x ^ m v ^ n g ntiat c h i j ^ khioang vat nang mau x a m den Tramtichi bien tijen dai; cat mau
x ^ m s a n g
y~^—-[ ranh gi6i dia ctiS'I Fj^j^^ T h a n qudng s a k h o a n g f^^^=^^ v a so hieu
L6 khoan tay
Hinh 2 Mat cat dia chdt - phdng xa tuye'n BN65 khu md Ban Nham (Phu Yen)
trudng ddt phil cd tde dd khue'eh tan ~ I m/ngay thi
khi Rn cd the' Ian truyin qua Idp ddt phu ddy 5 m (tai
nhiing noi ed dap vd dia chdt, ddt da bj v5 vun vd
nhdu, do tac dung ddi luu cua khi, quang dudng Ian
truyen eua radon cd the' Idn han nhi^u Idn tdi hang
chuc, hang tram met) Cd nghia Id khi Idy mdu khi
trong da't phil d khoang each 5 m each bi mat thdn
quang thi ndng dd khi radon giam di hang nghin Idn,
d khoang each 3 m ndng dd radon giam di hang trdm
Idn so vdi gia tri No eila nd tren hi mat ranh gidi
than quang va ddt phu Khi dd sau Idy mdu khi each
hi mat than quang 0,5 m, ndng dd radon bang No/2
Trong khi dd do cd chu ky ban ra nhd Tjn = 54,5
giay, nen ndng dd khi toron bi giam rdt nhanh trong
ddt phu Ndng dd toron trong ddt phil each be mat
than quang 10 cm da giam di hang tram Idn so vdi
gia tri No eila nd tren hi mat ranh gidi than quang
va da't phu
Chinh vi vdy di thudng phdng xa ndi chung va
dj thudng khi phdng xa ndi rieng tai eae khu vuc
quang bj phu cd dae die'm khae han so vdi tren eae
khu vuc quang Id tren mat ddt
Hinh 3 dua ra mat cat dia chdt phdng xa tuye'n
BN68 khu md Ban Nham Tai canh trai cua mat cat,
than quang ed ehilu ddy Idn ham lupng cao (quang
gidu cd ham luong > 100 kg/m ) bi phu bdi ldp bdi
tieh eat set chieu ddy 60 em - 1 m gay ra di thudng phdng xa cd cac dae diem sau : cudng dp bire xa gamma ed gia Ui tir 5 - 16 pR/h, ndng dd R„ khoang 6.000 8.000 Bq/m^' ndng dp toron Nn, ~ 2000
-4000 Bqlm\
Khi ddt phil ed hi ddy Idn se ed kha nang hdp
thu hoan toan birc xa gamma do eae chdt phdng xa trong than quang phat ra (b^ ddy ddt phii hon 1 m), Khi phdng xa toron eiing khdng the' Ian truyen xa
khdi hi mat than quang tdi khoang each hang met
Diin dd cd nghTa tai cac khu vuc quang bj phu
bdi ldp bdi tich cd hi ddy Idn, tren mat ddt
khdng the' phat hien dupe di thudng gamma va di thudng ndng dd khi toron Ne'u ddt phil khdng qua ddy (chi^u ddy ddt phu khdng qua hang chuc met) thi cd the phat hien dupe di thudng ndng dp khi radon
Mat eat dja chdt phdng xa tuye'n 26 khu Hoai
Nhan {hinh 4) minh hpa cho di6u vira ndi d tren
Tai day than quang sa khoang HN2 bi phil bdi Idp bdi tich ddy 3 - 5 m Hoan toan khdng phat hien dupe di thudng gamma va di thudng ndng
dd toron Di thudng ndng dd radon ed gia tri 400
-500 Bq/m nhd gdp hang chuc Idn so vdi di thudng ndng dd radon tren tuye'n 68 khu md Ban Nham
Trang 5Rn.Tn (8q/m )
10000
CHI D A N
| / ''•y I 0 6 thi Tn Tram tich hon hop bien - gio" cSt mau xam, xam Vcing nhat chijra khoang vat nang mau xam aen Than quang sa khoang
va so hieu
Hinh 3 Mat cat dia chdt - phdng xa tuye'n BN68 khu md Ban Nham (Phii Yen)
R n Tr,( B q / m 3 )
BOO
M A T C A T O I A C H A T - P H O N C S X A T U Y E N 2 6
K H U H O A I N H O N , T I N H B I N H f > | N H R n , Tn< B q / m ^ ) aoo
E
^3
D u c r n g b i ^ u dien f
n o n g d 6 R n L
O u O n g b i e u diSn
n 6 n g d 6 T n f
O u t J n g b i ^ u d i ^ n [
c u a n g 436 p h 6 n g x a I g
C H I D A N
T r ^ u n tfch h 6 n h o p b i ^ - 5p6: c S t hat nho d^n
t r u n g m d u x d m , xdnn v d n g , c 6 c h u r a c^c k h o a n g v&X q u a n g h a i n h o m a u d e n
T r ^ m tfch b i ^ n s6t b*t nndu x ^ m xSnn x a n h edit x ^ m t r S n g
^ ranh gitSi d i a chSt 7—J T h S n q u a n g s a k h o & i g
^ ^ v a s o hieu
Hinh 4 Mat edt dja chdt - phdng xa tuye'n 26 khu md Hoai Nhan (Binh Dinh)
2 Tim kiem quang an va danh gia 6 nhiim moi
trudng khu mo dai hie'm theo dae diem dj thudng
khi phong xa
Tren md quang ddt hie'm phdng xa X ngudi ta
da tie'n hanh phuang phap khi phdng xa bang may
phd alpha RAD-7 eila My Tren mdt sd tuye'n xac
dinh rieng biet ndng dd Rn va Tn trong cac Id
chodng ed dp sau 0,8-1,0 m trong ddt phil de nghien ciru kha nang ap dung phuong phap khi phdng xa trong tim kie'm quang Tren dien tich khu
md tie'n hanh do ndng dd Rn trong khdng khi gdn
700 die'm phuc vu danh gia d nhiem khi phdng xa
va tinh li^u ehie'u trong xdm nhap vao ca the' ngudi qua dudng hd hdp
Trang 6Sau day dua ra su phan tich luan giai cac dae
di^m di thudng khi phdng xa nhim lam sang td kha
nang dp dung phuang phap khi phdng xa trong tim
kie'm quang va danh gia d nhilm mdi trudng khu md
Tren tuye'n II md ddt hie'm X {hinh 5) da xac
dinh dupe cac dj thudng ndng dd Rn va Tn tren than
quang ddt hie'm
Than quang ddt hie'm gom 2 phdn : nhanh I kich
thudc nhd nam phia trai tuye'n, dudi ddt phil ddy
5-7 m Nhanh II kich thudc Idn hon nam phia phai
dudi ddt phil ddy 1-2 m Di thudng ndng dd Rn cd
bien dd cue dai NRnmax = 250.103 Bq/m tai khoang
giira nhanh II, di thudng ed be rdng chung 100 m
nam tren toan bd tdng da phirc he Pusamcap chira
eae than quang ddt hidm Dieu dd xae nhan phuong
phap khi radon cd kha nang phat hien eae than
quang chira urani nlm dudi ddt phil 5-7 m tdi hang chuc met, khi radon cd the' Ian truyin ra xa khdi than quang ke' ca theo chilu ngang tdi hang chuc met Dae die'm nay phu hap vdi ke't qua tinh toan ly thuye't theo eae cdng thirc (4, 5, 6, 7) da noi 0 tren
Di thudng ndng dd Tn chi phat hien dupe tai nhanh II cHa than quang npi ed ddt phil ddy khdng qua 1 -2 m, khi dd dd sau phat hien di thudng khi toron tuong irng vdi dd sau Id chodng Idy mdu khi
Di thudng ndng dp toron cd bien dp nhd hpn di
thudng Rn va dat gia trj cue dai Nmrnax - 50.10
Bq/m tai khoang nhanh II cda than quang Do cd chu ky ban ra nhd (Txn = 54,5 giay) nen phuong phap khi phdng xa toron cd dp sau nghien ciru nhd
va tinh dinh xir cao hon so vdi phuang phap khi phdng xa radon
DO THI NONG E)0 KHi PHONG XA TUYEN
i/r*i lo^^i&jVTirii
Nlll IO*5iB*'m5l
MAT CAT D|A CHAT TUVehJ 2
(SO
1)0
I * )
MO
?» *l> 60 DO 1110 lao ^*o Ito •Kfo yfo ito
C H I D A N
I" ; ; j i.^i>it<ii>iirii ck-inv; pi;-.|_-L
t
[z:
S y i ' o i t
y.^\ * • Uixofi iLKJy K A U t
Q H e D ^ ii>
Hinh 5 Mat cat dia cha't - phong xa tuye'n 2 mo da't hie'm X
Trang 7Ddi vdi muc dich nghien cim mdi trudng phdng
xa, hinh 6 dua ra so đ dang tri ndng dp radon trong
khdng khị Tren đ thdy rd cac than quang đt hiém
phdng xa da gay ra cac di thudng ndng dp radon vuot
qua tieu ehudn an toan eho phep (NKn> 100 Bq/m )
ed dien tich phan bd Idn gdp hang chuc, hang tram
Ian dien tich phan bd cua than quang Gia tri cue dai
ciia di thudng tren mdt sd than quang dat tdi gia trj
NKn > 500 Bq/m Idn gdp 5 Idn tieu ehudn an toan eho phep De dang nhan thdy di thudng ndng dp khi phdng xa ed xu hudng Ian n5ng theo hudng dong nam
- tay bdc Uung vdi hudng gid mua chii dao va phuong thung lung dja hinh cua vung md Day la dieu can luu y trong quy hoach kién true cac cong trinh nha xuong san xudt va dan dung cila vung de tranh tac hai
d nhiem khi phdng xa đi vdi siic khoe con ngudị
[ZD ILJ
1 1
ED
1 ^ IH3 EEEl
i: H I D A N Du^m ,1.: R.,,1oii,;, ?.,- iii DiiOup ilouy UnvujJ Radou
Dinli QUI ^Ti do cao boậMioi Difouy 0 10 E)iioii^ UIOQ L»up L>aQ r>i ilmwả iioug lio inctou n o u ^ iiLiou^ iilii \ i f i qiịn ri^u cliụ'^ii an lọiii olio j-Miep
Than quSng flat hifim - Baril - Fluorit
Hinh 6 So đ đng trj ndng đ radon trong khong khi md X
K E T LUAN
1, Tren ed sd xir ly tdng hpp eae tai lieu dja chdt
phdng xa hien cd da dua ra md hinh dae trung eila
than quang sa khoang ven bién mien Trung va quang
đt hiém chira chdt phdng xa, cac cdng thirc tinh
toan ly thuyét ndng đ khi phdng xa toron va radon
da lam sang td dae diém di thudng khi phdng xa
tren md hinh than quang lam co sd lufln giai tai lieu
thue téeila cdng tae tim kiém phat hien quang dn
2 Két qua khao sat thue té tren 5 vung md sa
khoang miin Trung vdi hang chuc nghin diém do
gamma, hang nghin diem do khi phdng xa da minh
ehirng kha nang tim kiém phat hien quang dn theo
dae diém dj thudng khi phdng xa : quang sa khoang
ham lupng cdng nghiep Id ra tren mat đt, gia trj ndng đ khi toron phu thudc vao ham luong quang nhung ludn ludn Idn gdp 2 - 3 Idn ndng dO khi radon Khi quang bj phil bdi eae ldp bdi tieh cat set thi eae gia trj eudng d6 gamma, ndng dp khi phdng xa deu
bj giam dị Khi be đy đt phu h > 80 cm (chieu sau tdi da ciia cac Id chodng Idy mdu khi) thi ndng dp khi toron se nhd han ndng dO khi radon Tren cac than quang cd đt phil đy (khdng qua 10 m) chi cd thé phat hien dj thudng yeu cua ndng dp khi radon cdn di thudng gamma va dj thudng ndng dp khi toron bj triet tieụ
3 Két qua khao sat phdng xa tai khu md X chi
ro phupng phap radon cd thé phat hien dupe than quang đt hiém bj chdn vCii dudi tdng đt phu cd
Trang 8dd ddy tCr 5-7 m tdi 10 m Cac than quang ddt hie'm
phdng xa da gay ra cac dj thudng ndng dd radon
trong khdng khi NR„ > 100 Bq/m vuot qua tieu
ehudn an toan cho phep tren dien tieh Idn gdp hang
chuc, hang tram Idn dien tieh phan bd ciia cac than
quang Tai mdt sd than quang bien dd cue dai dj
thudng ndng dd radon trong khdng khi dat tdi gia
trj NRnmax > 500 Bq/m"* Idn gdp 5 Idn tieu chud'n an
toan cho phep, Dj thudng khi phdng xa cd xu hudng
Ian truyen theo hudng gid thdi va phuang thung
liing dja hinh Day la di^u edn luu y trong quy hoach
kie'n true eae cdng trinh san xudt, cdng sd, dan dung
d^ tranh tac hai bijc xa do d nhiem khi phdng xa
ddi vdi siic khoe con ngudi,
Bdi bao hoan thanh dua tren ke't qua nghien cim
cua di tdi khoa hpe trpng die'm cdp Bd, ma sd
B2008-02-57TD Ngudn tai lieu la ke't qua nghien
ciru eua di tai vd thu thap tiif Luu trir Cue Dja chdt
va Khoang san Viet Nam
TAI LIEU DAN
[ I ] VO NGOC ANH, 2004 : Luan an Tie'n sT dja
chdt "Nghien cim dae die'm dj thudng phdng xa du
bao tai nguyen sa khoang titan va danh gia anh hudng
eila mdi trudng phdng xa ddi ven bie'n Trung Trung
B(3", Luu trir Thu vien Dai hpe Md - Dja chdt Ha Ndi
[2] V,I, BARANOV, A.X XERDIUKOVA L.V
GORBUSINA I.M NAZAROV, Z.M EPfflMKINA
1966 : "Cac bai toan va thi nghiem phdng xa" Nxb
Atomizdat, Moskva (Nga van)
[3] NGUYfiN VAN NAM, LE KHANH PHON, 2006 :
"Nghien cull su phan bd ndng dd khi phdng xa phuc
vu tim kie'm, tham dd va nghien cim mdi trudng
quang sa khoang ven bi^n", Tuye'n tap bao cao Hdi
nghj Khoa hpe Idn thii 17, Dai hpe Md - Dja chdt
[4| NGUYEN VAN NAM, 1984 : "Bao cao ke't qua
tim kie'm quang titan sa khoang ven bie'n thudc vung
hoat ddng eila Lien doan Dja chdt V" Luu trir Cue
Dja chdt vd Khoang san Viet Nam, Ha Ndi
[5] G.F NOVIKOV, 1989 : Thdm dd phdng xa, Nxb Nauka, Leningrad (Nga van)
161 LE KHANH PHON, 2007 : Bao cao "Dae trung trudng phdng xa va d nhilm phdng xa thi xa Lai Chau, huyen Tam Dudng va huyen Phong Thd" [7] Dia vat ly hat nhan tham dd (edm nang Dja vat ly), 1986, Nxb "Ldng ddt", Moskva (Nga van)
SUMMARY
Researching anomalous features of radioactive gas
to detect covered ore and to evaluate environmental contamination in the radioactive mines The theoretical calculations of concentration of radioactive gas radon and toron on the model of the typical body and mining mineral sand at Central coastal zone and the radioactivities contain of rare earth mine indicate : the body of layer-ore contains horizontal substance with the dimensions correspond half-space of infinite radiation The result detects hidden-ore by characteristic of anomaly of radioactive gas At the exposed surface of ore-body, anomaly
of toron-gas depends on content of ore by always larger than 3 to 5 times of anomaly of radon gas When the ore is covered, the concentration of toron-gas will reduce quickly ; when the thickness
of covered soil h > 80 cm, the concentration of toron-gas will be smaller than radon-gas, but when the thickness 3 m < h <10 m, the concentration of radon-gas will completely disappear and till remain the ability detect weak concentration of radon Radoactive reseach in area of X mine show the radon method is possible to discover a radoactive rare earth ore body under the depth of 5-7 meter to
10 meter The radoactive rare earth ore body cause
an anomalous radoactive air concentration NR„>100 Bq/m^, exceeding safety value Anomalous areas are often to hundered times large than distributed area of ore body, and tend to transmit by wind direction and valley rellief
Ngay nhan bdi 04-11-2009
Trudng Dai hoc Mo Dia Chdt Lien doan Dia chdt Xa hie'm