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:
1.
TS. Pham
Dmh Khang (Pho chu
tn)
2.
ThS. Dang
Phmvng
Nam
3.
TliS.
Nguyen Tlic Nghia
4.
Cac
sinh
\'icn nam
ihu'lu"
(Xu\cn.
Sctn.
Nga)

IIA
\()1 s :()f)4
BAO CAO TOM TAT
Ham
liTong cua
cac dong vj (
K"^,
U''^
Th''^
Cs'^' )
trong moi
tnrcmg
(da't,
thirc
vat) cua
tnrcmg
DHKHTN - DHQG Ha noi
a
Hoa Lac trong
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
2.
ThS. Dang
Phuong
Nam
3.
ThS. Nguyen The
Nghia
4.
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 trong
cac
mSu
moi
tru5ng
(dat,
thuc vat) cua cac dong vi
K^^
U^^^
Th^^^

Tren
ca
s6
nay 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
6
hien trucmg.
- Lay
mSu
dat thuc vat ve phong

thi
nghiem do 6 cac he do pho gamma cua cac
CO sa CO
he do 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:
1.
Do tnrcmg xa va xac dinh ham
luong
cua
K,
U^^^
Th^^^
trong cac nam
tir
2000
-^
2004 tren ban do 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:
6
kenh tong cong so dem tap trung
tuang
doi cao
a
khoang dem 3000
-^-
4000,
tan suat xuat hien
tuong
ling la 52%.
6
cac khoang dem khac
thl
tan suat xuat hien
ciia
so
dem
la
nho,
gia tri nay
bring 4%.
6
kenh
Kali,

so dem tap trung kha cao
a
khoang dem 200
-
300. tan
suat xuat hien
len
den 92%.
6
kenh
Uran,
tan suat xuat hien
a
khoang dem 200
H-
300 la 72%.
6
kenh Thori toan bo so dem tap trung trong khoang dem 100
^
200.
trong khoang dem hep
han,
tap trung so dem cao nhat trong khoang tii 140
^
160,
tan suat xuat hien
ciia
so dem trong khoang nay la 52%. Noi chung
truong
xa

Gamma tan man.
b.
Ham
lirang
trung
blnh K
,
U-^^
Th"'
c6 trong dat
a
Hoa Lac trong
nhCrng nam 2000
^
2004
dugc trinh
bay trong bang so
13
tren
hinh
ve so
01 la:
Nam
2001
H-
2002
bing
may
GAD
2002

^
2003
bang pho
gamma phong
thap 6 PTN.
Chua[n
bang
K.O
(4,48 %)
2003
4-
2004
bang
ph6
gamma phong
thap
a
PTN.
Chuain
bang
K
0(<f/t^7%)
K
(%)
2,70 ±0,36
3^^
^>±
0,003
U-^'(ppm)
7,34 ± 0,29

5,22 ±0,62
8,86 ±0,30
Th-^^-(ppm)
14,11
±0,89
14,59 ±0,54
22,85 ±0,55
1
Cs'-'^ppm)
20,61 ±0,41
Hau het cac diem do tu 5,
10,
25 diem trong 3 nam deu cho ta thay ham
lugng
K
a
khu
vuc
nay la khong dang
ke,
nho
hem nguang
do
ciia
may GAD -
12;
tham
chi a
cac
mCm

lay ve phong
thf
nghiem cung cho ta
vai nhung
ham
lugng
thap (
Z ^
3
)%.
Trong khi do ham lugng
K"^'^
dugc khao sat
oi
mot so
khu vuc,
chang
han
a
Ha noi nam 1990
c6
la 4,4
^i
f2|,
a
khu dat Nghia do - Cau
giay
trong nam 2000
c6
la

2,(W^^(
[3|,
o
khu nha may
thuy dicn
Hoa
binh
trong
nam 2()()()
c6
la
2,2iS^;
[4].
Ham
luong
trung
hinh
cua
Uran tren
cac
dicm
do
trong suot 3 nam thang giang trong mien tu (5
^
X) (ppm).
Kcl
qua nay trung
vi'ri
ivci
qua ao

a
cau giay trong nam 2000 la 6,92 ppm
[3]
va ket qua do
a
Ha noi nam
1990
c(3
la 7 (ppm) [2]. Ham lugng trung
binh
cua Thori
tren
cac diem do trong 3
nam thang giang trong mien tu
(14 ^
22) (ppm). Ket qua nay trung
voi
ket qua
c6
trong dat cua Ha noi do nam 1990 la 17 ppm [2] va do
a
khu vuc cau giay nam
2000 CO
la
18,7 ppm
[3].
• So vai
CO
do Hue, ham luong
ciia

K la 1,53%,
ciia
U'-^^la
4^
7 ppm,
ciia
Th'"-
la
11,1
ppm [2] thl ham lugng
ciia Thori ciia^khu
vuc nay
Ian haru
2.
Xac dinh suat lieu thuc nghiem a hien trucmg va so sanh vai suat lieu duac
tinh
tren ca sa so lieu
ciia
K
,
U^^^,
Th"^^
trong moi truang trong cac nam
tir
2000
^
2004 tren ban do theo
hinh
ve
1

tren manh dat
ciia
truang DHKHTN -
DHQG Ha noi.
Su dung may do lieu do a hien truang tren do cao >
Im
theo ban do tren cac
diem do va su dung cong thuc
(II.
1.1) [8] de
tinh
suat lieu chie'u xa (I) cho cac
diem do tren ca sa so lieu
ciia Kali
va
Uran
va Thori .
Chiing
ta nhan dugc
ket qua do thuc nghiem gia tri trung
binh
trong 3 nam thang giang trong mien
I,,
-
(9
^ 13) (laR/h)
va
I,,,
.^.^uye',
= (9 -12,7)

(|LiR/h)
Suat lieu thuc nghiem xuat hien tren hien truang trong 3 nam phan bo trong
mien
til
(6
^ 19) (|aR/h).
Lieu hieu dung tuang duang trung
binh H=
(70,07 ±
2,74) mRem/nam. Ket qua nay tuang duang vai suat lieu trung
binh
a khu vuc
nha may thuy dien Hoa
Binh
(9,89
|iR/h)
[4], a khu vuc do thi Hue (8,25
|iR/h)
[9],
a khu
\'\1Q
thanh pho Vinh
(11,0 |iR/h)
[9].
Nhin
chung lieu hieu dung tuang
duang bien
ddi
trong khoang hep (55,05

83,04) mrem/nam nho han khoang
hien do\ tren toan nuac My (45
^
105) mrem/nam [91. Lieu hieu dung tuang
duang trung blnh a day thu nhan
dugc
la nho (70,07 ± 2,74 mrem/nam); trong khi
do
\\t\x
hieu dung khuyen cao
ciia
ca quan quo'c te ve an toan phong xa la 0,5
rem/nam [10|,
vi
vay
biic
xa
lu
nhien a
dcly
khong gay anh
huang
den
sue
khoe
con
nguai.
.r
Aac dmh hoat do rieng cua cac dong vi phong xa trong cac
mAu

thuc vat dac
trung
a
khu dat trucmg DHKHTN - Hoa lac trong nhung nam 2000
^
2004.
Su dung he do Gamma phong thap
ciia
Vien hat nhan Da lat va Trung tam
hat nhan, Vien Vat ly Ha noi vai viec thu gom cac la cay che xanh, cay cam
ngugi (cay c6 may), cay bach dan cho
tCmg
nam trong suot 3 nam lien theo
phuang phap
ciia Cue
moi truang (Bo Tai nguyen va moi truang) [7]. Chung toi
da xac dinh dugc hoat do rieng phong xa
ciia
cac d6ng vi
K^^,
U-^'\
Th-'",
Cs''^
Be^
bang phuang phap tuyet doi.
Chiing
toi da nhan dugc ket qua nhu sau:
Nam do
2000^
2001

2002^
2003
2003^
2004
2000^
2001
2002^
2003
2003 4-
2004
2000^
2001
2001 ^
2002
2003
^
2004
Doi
tugng
mSu
La bach
dan
La cay
com
nguoi
(c6
may)
La che
xanh
K^"(Bq/kg

tuai)
34,19
±
1,33
33,31
±
3,13
27,95 ±
1,53
56,35
±
6,63
45,94
±
3,93
35,91
±
2,94
30,32 ±
3,70
32,07 ±
2,13
30,99 ±
2.33
U-^^(Bq/kg
tuoi)
0,87
±
0,10
1,14±

0,17
1,73
±
0,21
0,95
±
0,11
1,33
±
0,15
1,06
±
0,20
5,13±
0,62
1,40
±
0,13
0,96
±
0,18
T^232
(Bq/kg
tuai)
0,91
±
0,11
1,04
±
0,10

1,15±
0,11
1,07
±
0,12
0,50
±
0,07
0,60
±
0,09
5,74
±
0,68
0,56
±
0,07
0,49 ±
0,08
Be^
(Bq/kg
tirai)
5,73
±
1,18
-
2,20
±
0,60
6,38

±
1,78
-
8,06
±
0,93
11,38
±
1,76
*
2,48 ±
0.73
Cs'-"
i
(Bq/kg
tuai)
0,14±
0,04
2,35
±
0,15
0,10
±
0,03
• '
2,52
±
0,09
1
!

0,05 ±
1
0,03
1
i
1
2.51
±
1
0.18
:
Mot dang
ph6
gamma
ciia
cac
miiu
thuc vat duac
minh
hoa tren
hinh
ve
so
09.
Cac
so
lieu nay tuang duang vai cac so lieu nghien cuu ve
nhiem \a moi
iruang iren doi
tugng

luang
thuc, thuc vat a mot so nuac tren
ihe
giai.
ihf
du trong
che kho
ciia
Thai nguyen a thi
truc:fng
Ha noi vao nhung nam 1980
[11] c6 luaniz
Cs ' la
0,01
Bq/g;
trong che tuai mua a thi truang Ha noi trong cung thai gian c
o
la 0,0003 Bq/g, trong mang kho mua a thi truang Ha noi vao nhung nam 1980
lugng
Cs'''
CO la
0,002 Bq/g va lugng
K"^*
c6 la 0,73 Bq/g.
f.
Tinh hinh thirc
hien kinh
phi ciia
de
tai«

De tai dugc duyet va cap kinh
phi
chi cho nam cuoi trong nam 2003
^
2004
la 10 trieu dong tien Viet nam; chi
phi
cac khoan cho truang, cho bo mon, thuc
chi cho viec nghien cuu chi con ca (8
^
9) trieu dong tien Viet nam. Mot khoan
kinh phi Ngan sach Nha nuac rat nho, c6 the noi khong
dii
cho mot phep do thuc
nghiem, trong khi do de tai da phai thuc hien truac do 2 nam khong c6 mot chut
kinh
phi
nao. Chiing toi phai nha
sir giiip
da
ciia
cac ban be a cac ca sa c6 thiet bi
ho trg, khong lay tien thue do dac. Thuc te kinh
phi
da tap trung chi cho
phdn
chuyen mon c6
tinh
chat rat tugng trung cho cac can bo khoa hoc ca (80
-r

90)%
cho chuyen mon con (20
^
10)%
cho van phong, giay ta, nghiem thu, xemina
g.
Kien
nghj.
De tai nay can dugc tiep tuc tren doi tugng nuac, khong
khi
vai kinh
phi
phai tang cuang ca gap
(3^4) Ian ciia
de tai cu; c6 nghia la de tai can dugc
tiep
tuc vai kinh
phi
ca 30
-^
60 trieu de hoan tat mot mang
Ian
ve moi truang nhiem
xa
a
viing dat
ciia
truang DHKHTN
a
Hoa lac.

Khoa quan ly
n
iO
A^
^/tu^'^"^
Chii tri
de tai
Dang
Huv liven
hii tri dc lai
Project: Contents of
(K'*^,
U^^^
Th^^^
Cs^^^)
isotopes in the environmental
samples
(soil,
vegetation samples) in a campus of college of science, Vietnam
University during 2002 -2004
Code: QT-03-04
Head of
the
Project: Asso.Prof. Dr. Dang Huy Uyen
The
staff:
Dr. Pham Dinh Khang
Msc. Dang Phuong Nam
Msc. Nguyen The Nghia
Aim of the Project:

In
order to estimate the radioactive dose of K, U and Th isotopes in the
environment, samples collected were measured radioactive concentration by
low- level gamma spectrometer in Lab.
Content of the Project:
> 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:
1.
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 1
a) As can be seen in figures 2, 3, 4 and 5
,
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
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%)
K (%)
U (ppm) Th (ppm)
Cs (ppm) j
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 5 to 8 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 7 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.
2.
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
1.
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 3 years I
m
= 9- 13 u R/h; average results of the external radiation
level obtained by calculating during 3 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 does not cause the
human being health.
3.
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 3 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 metho
[7].
The results are shown in tab,
by a method given
year
•
sample K
40
U
ZJB"
Th
T7T
Cs
Be
tea leaf
gum leaf
chrysopogon
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 1
Ban do nghien
ciJu
2
Do
trucrng
xa va xac dinh ham
lugng
cua
K^°,
U^^^,
Th^^^
3
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
trong moi
trudng
20
Xac dinh hoat do rieng cua cac dong vi phong xa trong
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
Ma
dau
Van de nghien curu do 6
nhilm
phong xa trong moi trucmg da
tro
thanh
thirdng
xuyen theo khong gian
th5i
gian tren cac doi tuong (dat,
nuoc,
khong
khi,
thuc pham, thuc vat ) nhieu hoi nghi khoa hoc do to chuc nang luong
nguyen
tir

quoc te (IAEA) to
chiJc
da
thuong
xuyen thong bao cac tin tuc nay
rat day du cho cac nu6c. Dac biet nhieu nam gan day nhieu su
c6 ciia
mot vai
nha may dien nguyen
tir
( My, Nhat, Lien Xo cu) da lam
6 nhi^m
moi truang
va da
CO
luc anh
huong
den Viet Nam nhu vu
Trecnobim.
nhiSu
nu6c da co
chien tranh
cue
bo ( chien tranh vung Vinh, Nam Tu,
)
da
diing t6i
vu
khi
CO

dau dan
chiia
chat Uran ngheo lam cho moi trucmg bi
6
nhi^m.
Vi
vay
van de kiem soat moi truang thu5ng la cong viec
thu5ng
xuyen cua cac nuac.
O nuac ta, cac dong vi nay trong moi trucmg da
dugc
nhom can bo Khoa
Vat ly truang DHKHTN, DHQG va Bo mon Vat ly hat nhan nghien cuu
nhi^u
nam trong cac
chuong
trinh cap nha
nu6c
tu nam 1980, tuy nhien cac
so lieu ve cac dong vi nay
a
khu vuc dat mai dugc nha nuac giao cho Dai
Hoc Quoc Gia,
thi
day la so lieu dau tien. Cac so lieu nay co the giup cho
DHQG sau nay phat trien toan dien va co the lam ca so doi
chung
cho cac
cong

trinh
nghien cuu ve moi trucmg cua mot khu vuc nghien cuu khoa hoc
hien dai va con co mot phan
16n lao
la gop
siic
vao viec bao ve canh gi6i dat
nuac khi cac nuac
lang gi6ng
co su dung t6i vu
khi
hat nhan lam 6
nhi6m
moi truang trong khu vuc. Dac biet
a
khu vuc dat Truang DHKHTN tuong
lai se
CO
mot he thong thiet bi may moc hien dai cho
linh
vuc hat nhan. Vi
vay viec nghien cuu moi truang nay truac khi xay dung phong may Vat ly
hat nhan
h^
viec tra thanh nhu
cau
cap bach. Chung toi da chon dia ban
nghien cuu la khu dat
ciia
truang DHKHTN nhu hinh ve

01.
k
15
A
y
IlinliOd Plichi 1)0 (licm
do
6'
khu vuc
quanh
ho cua khu dai Dai hoc Khoa hoc
tit
nhien,
Dai hoc Quoc gia (Hoa Lac).
-
f\^
LcK Oc
-^a.
^€A^
CU
"twv^
>vJ^
l^<r]
^
t^>o^^
6
D
-
CAC CONG VIEC DE TAI DA THUC HIEN
I. Do

trirong
xa va xac djnh ham lugng cua
K,
U,
Th:
I.l
Do truang xa gamma tren 25 diem trong
hinh
ve 01
ki
hieu A,
troniz
nam
200 U
2002 a hien truang
[11
Biing may GAD -
12 ciia
Lien doan Vat ly dia chat, chiing
tcM
da
[6
chuc di
do truang xa
a
hien truang; chiing toi da xac dinh dugc truang xa
ciia
Gamma tu nhien va tong cong phan bo trong dat.
• Ket qua cua so dem trong
100

giay tai 25 diem do
ciia hinh
ve so 01
dugc the' hien trong bang so 01.
Bang
01:
So dem trong 100 giay
Diem do
1
2
3
4
5
6
7
8
9
10
11
1
12
i 13
14
15
16
17
18
19
Tong cong
2809

±42
2663
±
46
2869
±46
2751
±42
2714±48
2947
±45
2856±5I
1326±28
2746
±25
3386±72
3593±78
3575±51
3267
±49
3605
±32
3471
±61
3767±55
3 344
±30
3414±65
2970± 15
Kenh

K'"
288±6
286±17
276
±7
254±15
280±15
264±13
264±7 .
196±15
218±15
281±12
261
±4
283±12
286±11
277
±9
270±10
285±16
242
±9
271±17
298
±25
Kenh
U"-"^
228±19
190±10
226±16

227± 17
214± 15
241
±3
215±2
187±7
225
±14
286±15
297±10
289±22
255±6
288±41
286
±20
322±19
278± 19
295
±8
329± 14
KenhTh-'-
138±9 !
135±8
155±13
253±5
154±17
155±8
135±8
121±11
115±8

155±14 !
169±8 :
151±7
1
147±10
154±15 i
164±9
1
187±16
i
158±15 !
152±16
198±9
20
2843
±42 228± 11 233± 16
127± 10
21
2312± 18
238
±3
295
±8
56
±3
11
2^
24
4727±84
451± 11

620
±26
3483
±75
274
±6
369
±4
3598
t
2
1
277± 17
362
± 15
2X91 t2^)
111
^~l
2(^2
t 10
124± 10
153r
1
59
r
[7
r2Sr9
Sai
so
thong ke cho phep doi

voi
kenh
tOng
cong la
2*"/;,
kenh
K""'
la
5'i.
kCnih
U-'''vakenhTh-'-la8^/r.
Bang
.so
02 phiin bo so xung theo tan so xuat hien va
so'
diem do tren kenh tons cons
So
xuns
Tan suat xuat hien So diem do
000 -
2000 0.04
1
2000-3000
0.4 0
2000-4000
0.52
13
>4000 0.04
t n
SI

0.6i
0.5
0.4
0.3
0.2
0.1-
n
\J
i
t
/
xu t hi n
1
1 2
V^
1
S-i^
3
4
s xung
Hinh
so 02: Bieu do phan bo so xung
theo tan so xuat hien tren kenh
t6ns
cons
Bang so 03 phan bo so xung theo
tan
so xua't hien va so diem do tren kenh
K
4(:

So xung
100^200
200^300
300-400
>400
Tan suat xuat hien
0.04
0.92
0
0.04
So diem do
1
11
0
4
t n su t xu t hi n
1
0.8
0.6
0.4
0.2
0
'
y
^
y
1 2
i
i
3 4

Hinh so
03: Bieu do phan
bo
so xung theo tan so xuat hien tren kenh K
40
Bans so 04: Phan bo so
xuns
theo tan so xuat hien va so do tren kenh
U'
:is
So xung
100^200
200^300
300^400
400^500
500^600
>600
Tan
sual
xuat hien
0.08
0.72
0.16
0
0
0.04
So diem do
2
18
4

0
0
1
t n su t xu
thi
n
0.8/1
s xung
Hmh
so 04: Bieu do phan bo xung theo
trin
so xuat hien tren kenh
U-"^^
Bang so 05: Phan bo so xung theo tin so xuat hien va
so diem do tren kenh
Th"-*"
So xung
100-IS
720-
140
I Tfin
suat
xuat hien
'
0.04
' ().2S
So diem do
7
'
140-160

160-180
>
180
I 0.52
I 0.08
i 0.08
^ 13
2
2
t n su t
xu^t_hi
n
0.6;
0.5;
0.4
0.3
0.1
0
,/
/
y
.>
•v
s xung
Hinh
so 05: Bieu do phan bo so xung theo tan so xuat hien tren kenh
Th"'"
Phan bo xung
a
cac kenh theo tan so xuat hien cho thay:

a
kenh tong cong so
dem tap trung tuang doi cao
a
khoang dem
3000-4000; 2000^3000,
tan suat
xuat hien
tirong umg
la 52% va 40%. O cac khoang dem khac thl tan suat xuat
hien
ciia
so dem la rat nho, gia tri nay bang 4%.
6
kenh
KaH,
so dem tap
trung kha cao
a
khoang dem
200^300,
tan suat xuat hien len den
92%,
C)
kenh Uran, tan suat xuat hien
a
khoang dem
200-300
la 72%.
0 kenh Thori, toan bo so dem tap trung trong khoang dem

100^200,
trong
khoang dem hep han, tap trung so dem cao nhat trong khoang
tCr
140-
160,
tan suat xuat hien
ctia
so dem trong khoang nay la 52%.
•
Sir
dung phuang phap ma tran, xac dinh cac he so anh huang bang
each
.\ac dinh
toe
do dem tai cac kenh tuang
ung
khi do phong va do cac mau
chuan da biet truac ham luang tai nguon chuan quoc gia cua Lien doan Vat
ly dia chat a
Lucmg
San Hoa Blnh.
Cac mau chuan:
K"^',
U''^Th-^^
ham
lucrniz wiawsi
mm:
6
K"'=(48±5)%

U-''=
(0.025
±0.001)%
Th-'-=
(0.049 ±0.03)%
So dem
truns blnh
cho 3
k'in
do irons
thoi sian 100 jiiav
Mau
do
Mau chuan Kali
1
;
Mau chuan Uran
j
: Mclu
chuiin Thori
''
Phong
KenhK
10492
5910
4421
509
Kenh
U"''
204

5828
3981
193
Kenh Th-'-
;
90
i
405
i
4801
90
Ket qua tfnh he so vai sai so nho thua 10% duac bieu
diln
bai ma tran sau
^208
216040
79836^
r
A =
-I
I
•21
a,-, a
~^
ar
13
^23
a^i
a-,-, a^.^,
225400

12600
77306
96142
Truang hap cu the so nguyen to phong xa co trong
mSu
la 3: Kali, Uran,
Thori. Cac
buc
xa duac chon de phan
tich:
Doi vai Kali - 40 dua vao vach 1.46
MeV
do
K"^*'
phat ra.
Doi vai Uran
-
238 dua vao vach 1.76 MeV do
Bi"'"^
phat ra.
Doi vai Thori - 232 dua vao vach 2.62 MeV do
Th'^**
phat ra.
Vai mau bat
kl
cac so dem N,,
N., N^
da tru phong, tuang ung vai 3 vung
nang
lugng

dac trung cho 3 nguyen to dugc xac dinh theo phuang trinh
luven
tfnh 3
an
so, co dans sau:
N|=a,,q,+a|,q.+a,,q;,
N,^
a,|q|+a ,q.+a,,q;,
NFa;iq|+apq,+a,,q,
Cac so hang
tudo
N,,
.\,,
N^
chi'nh
la
loc ^o
dem lai 3 kenh:
Kali,
Uran, Thori
diroc
xac
duih
bang
llurc
nghiC>m.
Giai phuinm
trinh luven linh 3 an so
iron
thu

7
dugc cac gia tri
q,, q., q;
q,
la ham lugng cua
Kali
q-,
la ham lugng cua Uran
q^
la ham lugng cua Thori
Bang chuang
trmh
C""
dugc trinh bay cu
the a
phan phu luc. ham lugng cua
Kali, Uran, Thori dugc tfnh va cho ket qua a bang so 06.
Bang 06. Ket qua do thirc nghiem tren 25 dia diem
7,16 ±0,29
16
12 ±i)}H
i Diem do
1
1
1
1
2
3
4
i

5
1
1
i 6
7
8
9*
;
10*
1
11
12*
1
13
14*
;
Ham
lugng K
(%)
0,30 ±0,10
0,46
±0,11
0,24 ± 0,08
0,13±0,11
0,32
±0,11
0,12 ±0,70
0.24 ± 0,40
0.05 ± 0,08
0,30 ± 0,06

0.16 ±0.06
Ham luang
U-'^^Cppm)
5,44 ± 0,22
3,78 ±0,15
4,71 ±0,12
4,83 ±0,19
4,19±0,18
5,41 ±0,22
4,94 ± 0,20
4,17±0,17
6.16 ±0,25
7,50
±0,30
2,84 ±0,11
7,78
±0,31
6.35 ± 0,25
7,63
±0.31
Ham luang
Th-'-(ppm)
1
13,64
±0,84
13,55 ±0,83
15,8 ±0,95
15,28 ±0,94
15,85 ±0,95
15,41

±0.94
13.39
±0,82
i
12,04 ±0,74
11,I5±0,68
1
15,14±0,93
;
17,21 ±1,05
1
14.69 ±0,90
14.46
±0.89
15.02
±0.92
6
9,97
±0,32
8.4
.13
8
17*
7.01 ±0.28
5,50 ±0.95
18
8.03 ±0.32 14.76 ±0.90
19*
7.89 ±0.32
19.56

± 1.12
20*
21*
1
22*
1
1
23*
24*
1
1
25*
i
1
1
TB
6.08 ± 0.24
7.88 ±0,32
24,17 ±0,97
11,43
±0,56
10,88 ±0,44
7,39 ±0,30
7,34 ±0,29
12,41 ±0,76
15,16 ±0,93
9,73 ± 0,60
14,42 ±0.88
1
15,11 ±0.93

i
12,35 ±0,76
1
i
14,11
±0,89
1
Ket qua
ciia
ham lugng K, U, Th cho thay:
- Hau het
a
cac
die'm
do ham lugng cua K co gia tri am,
didu
do chung to ham
lugng
CLia
K
a
khu vuc nay la khong dang ke', nho han nguang phat hien cua
pho ke nha'p nhay GAD-12. Trong khi do ham lugng K dugc khao sat
a
mot
so khu vuc,
chang
han
a
Ha Noi nam 1990 co la 4,4% [2],

a
khu dat Nghia
do-
Cau giay trong nam 2000 co la 2,08% [3], hay
a
khu vuc nha may thuy
dien Hoa Blnh trong nam 2000 co la 2,28% [4].
- Ham lugng trung blnh tren 25 diem do cua Uran la 7,34 ppm, gia tri nay
Ian
han ham luang cua Uran
a
Ha Noi nam 1990 co la 7ppm [2] va 6 khu vuc
Nghia do - Cau giay trong nam 2000 co la 6,92 ppm [3] va
a
khu vuc nha may
thuy dien Hoa Blnh trong nam 2000 co la 4,36 ppm [4].
- Ham lugng trung blnh tren 25 diem do cua Thori la
14,11
ppm, gia tri nay
nho han ham lugng cua Thori
a
Ha Noi nam 1990 co la 17 ppm [2] va
a
khu
vuc Nghia do - Cau giay trong nam 2000 co la 18,7 ppm [3] nhung lai
Ian
han
ham lugng
ciia
Thori

a
khu vuc nha may thuy dien Hoa Blnh trong nam 2000
CO
la
1
1,73
ppm [4]
- So vai
CO
do Hue, ham
luOTg
cua K la 1,53%, cua Uran la 44,7 ppm, cua
Thori la
11,1
ppm [2|
thi
ham lugng cua Thori cua Uran va Kali a khu vuc
nav
Ian
han.
1.2.
Ham
lifitniz
cac
mzuven
to
K,
U. Th
tromz
dat tren 10 diem nhu hinh vc 01

v(Vi kv
hicu (
MM.
woivz
nam 2002 -
2()()3.
151
Sau khi
nghien cihi
ham
krtmg
cua cac
nguyen
to K. U. Th o
irurnLi
\a
gamma
l!\>ng
nam 2001 2002,
\o\
dclcclor
nhap nhay (GAD
12).
chuim
9
toi thay gia
iri
cua K co dieu can phai suy
nghi,
thuc ra la qua

nh(')
so
v(Vi
cac
gia tri a cac nguon dat khac
ciia
dat nuac cung nhu cac gia tri o cac nuac
niioai:
vl
vav
chuns
toi quvet dinh lav mau dat a 10 dia diem dac
irumz nvdivd
ve phong thf nghiem do trong he pho gamma phong thap cua Trung tam Vat
ly hat nhan cua Vien vat ly, Trung tam khoa hoc cong
nghc
va moi truang
quoc gia Viet Nam.
1.2.1.
So do khoi cua thiet bi do:
He do pho gamma
cila
trung tam vat ly hat nhan vai detector ban dan
HPGe
CO
sa do hmh ve so 06:
2
^tl>^
X
1

8
4
5
•
6
Hmh ve so 06
Trons
do
1.
MSu cSn
do
2.
Detector ban dan Ge (sieu tinh khiet)
100cm'
3.
Tien khuyech dai Model 2002
CSL
4.
Khuyech dai tuyen tfnh Model 2004
5.
ADC Model 8701
6. May tfnh co cai dat phan
m^m
ghi nhan, xu
Iv
pho
SlOO
CANBERRA.
7.
Nguon nuoi cao ap.

8. May phat xung chuan.
He pho ke gamma sau khi len den 3000V dugc chuan nang lugng ,
kiem tra do phan giai bang
Ra"^.
Do phan giai nang lugng la 2KeV tai
dinh
609,3 KeV hoac la bang
1,8
KeV doi vai nans
luans 1332
KeV cua
Co"^".
1.2.2.
Chuan nang luong [61.
Viec nhan dien cac dong vi phong xa tu pho gamma thong qua nang
knrng
dinh gamma va thai gian ban ra.
VI
vav viec xac dinh chfnh xac
nan<^
lugng cua cac dinh gamma la rat can thiet dac biet la trong cac truang hap
nhan dien dong vi tu dong qua cac chuang trinh xu ly pho. Dieu nay phu
ihugc
vao do phan giai nang lugng va do On dinh cua he pho ke
trt)ng
sunt
Unn
gian do. Trong cac he pho ke gamma, nguai ta thuong dung cac nguon chuan
da
biel

chfnh xac nang
lu(tng ctia
cac dinh gamma
de
chuan nang
knrng
Thuc
(e
cac pho
ke
hien
dai ciing
khong the dat duac do tuyen
linh Iv tmnm Wmvi
giai do rgng hang ngan kenh. Viec chuain nang lugng dugc thuc hien bang
viec lam khap cac so lieu bieu
didn
moi lien he giua nang lugng va so kenh
vai mot ham toan hoc la da thuc bac nhat hoac bac hai do su tuyen tfnh cua
ADC ia khong
tuyel
doi nen viec chon da
thiJc
bac hai la phu hgp han ca.
Duang chuan nang lugng dugc bieu
di^n a hinh
ve so 07
•
•
-

•
-
-
1
•
i
/
^
So
'<eu irii/c nghitim
-
Oi/Ong ;ain khdp
/
^^
'
•
1 -~
T
V
1
. i .
•
~
•
-
-
1500 2000
S6 kenh
Hinh
veso07:

Diayng
chuan
ncing ha/ng
cua he phdn tich pho gamma
Cac nguon chuain
dijng
de' chuain nang lugng bao g6m:
-^'Am(59,54
KeV,
T,/.=
433 nam),
'^^'Cd
(88,04 KeV,
1^^,^453,26
ngay),
'•^'
Cs(661,66
KeV,
T,/.=:30,l
nam),
-'^Mn(834,85
KeV,
T,/.=312,2
ngay),
''Zn
(1115,53
KeV,
T,/2=243,8
ngay),
'^

Co
(1173,24
KeV va 1332,5 KeV,
T,p_=5,27
nam),
"Na (511
KeV va 1274,54 KeV,
T,,.=2,6
nam),
''Y
(1836,06 KeV,
T,^.=
106,6
ngav).
1.2.3.
Chuan hieu suat ghi cua detector
[61
Hieu suat ghi cua detector dac trung cho kha nang ghi nhan cua tia
gamma do
mau
phat ra. Trong vat ly hat nhan thuc nghiem, hieu suat detector
dugc dinh nghia la ty so giua
toe
do dem photon n(E) co nang lugng E va
toe
do phat xa cac photon co nang luang E la R(E)
til
nguon phong xa:
n(E)
£(E)=

R{E)
Hieu suat phu thuoc vao nhieu yeu to nhu cau
hinh
nguon - detector,
vat lieu
che
tao detector, Do rat kho che tao ra hai hoac nhieu detector
giong het nhau, nen nguai
sudung
phai thiet lap viec chuan hieu suat cho lung
detector rieng biet. Ve nguyen tac co the xac dinh hieu suat ghi bang
iinh
loan. Tuy nhien
phirang
phap nay doi hoi nhung
iham
so chfnh xac ve kich
thuac vung nhay cua
tinh
the, be day lap chet, hinh hoc do
Vi
the de dan
dcMi
sai
so irong ifnh
loan.
Trong thirc te, nguai ta thuong su dung
phuc^ng
phap do dac
ihuc

nghiem ket hgp vai cac cong thuc ban thuc nghiem de xac dinh hieu
suai ghi
cua detector. Muon xac dinh hieu suat ghi ta can phai co mot bo nguon chuan
vai cac dinh gamma co nang lugng phu deu trong dai nang lugng ma detector
CO
the* ghi nhan dugc.
De loai
bo sai so do hieu ung cong dinh tot nhat la su-
dung
cdc
nguon dan nang nhu:
-^'Am,
"'
Cs,
'>ln,
'^"
Co tu cac so lieu thuc
nghiem vi hieu suat ghi
a iixng
nang lugng cua dinh gamma cu the ta co the
khap vai mot ham ban thuc nghiem de'
tlm
duang cong bieu dien moi lien he
giua hieu suat ghi va nang luong. Wax cac detector ban dan HPGe. thuong
dijng
la ham co dang:
Ln£
=
J^ci„L„E"
Trong do z la hieu

.suat
ghi cua detector, E la nang
lugng
tia
gamma,
a^
la cac he so ham khap.
Hinh
so 08 la duang cong hieu suat ghi cua detector ban dan HPGe
due^c diin2
de do dac trong cac
thi
nghiem:
0=
0.0
P
(KP
Hinh
veOH:
Duc'rii'^
coiii^
hieu suat
s,'///
ciiu
detector 100 cm'
Baniz
so 07. Hieu suat
shi
cua detector HPGe - 3905
(iOOcm

E(KcV)
40
W)
SO
100
El'W'i)
() S94.3
6.6264
13.227
16.977
E(Ke
140
160
ISO
200
V)
: Eff(^r)
17.96
17.061
15.917
14.736
E(KeV)
:
240
260
2S()
300
Et'f(^;)
12.5S
1 1.652

IO.S24
1().0S7
120
700
8.19
4.1028
220
13.6
320
720
3.9847
740
9.4316
340
j
400
460
520
8.8473
7.7363
!
6.3988
'
5.6145
360
420
480
540
8.3253
i

7.0563
!
6.1132
5.3904
380
'
440
1
500
'
560
7.8573
6.71 19
'
5.8517
5.1861
580
640
•
4.9968
>
4.5049
i
600
i
660
4.8211
1
4.3622
620

i
680
4.6575
4.2284
3.8734
760
3.7683
780
3.669
800
3.5749
820
3.4857
840
3.40
860
3.3205
880
3.2438
900
3.1708
920
3.1014
940
3.0345
960
2.9708
980
2.9099
000

2.8515
1020
2.7956
040
2.7418
060
2.6903
1080
2.6407
1100
2.593
1120
2.5471
1140
2.5028
1160
2.4602
80
2.4191
1200
2.3794
220
1.3411
240
2.3041
1260
2.2683
1280
2.2336
300

2.2001
320
2.1677
1340
2.1363
360
2.1058
1380
2.0763
1400
2.0476
1420
2.0199
1440
1.9929
460
1.9520
480
1.9413
500
1.9165
1520
1.8925
1540
1.8691
1560
1.8464
1580
1.8243
1600

1.8028
1620
1.7818
1640 7614
1660
1.7415
1680
1.7221
1700 .7037
720
1.6849
1740
1.6669
1760
1.6494
1780
1.6323
1800
1.6157
1820
1.5994
840
1.5836
1860
1.5681
1880
1.553
900
1.5382
920

1.5238
1940
1.5097
960
1.4959
1980 .4824
2000
.4693
2020
2080
2140
1.4564
1.4915
.3849
2040
1.4438
2060
2100
1.4077
2120
2160
.3739 2180
1.4315
.3962
1.3631
2200
1.3526
2220
1.3422
2240

1.3321
2260
2320
2380
1.3222
1.2937
1.2669
2280
1.3125
2300
2340
1.2846
1
2360
2400
1.2584
2420
1.303
1.2757
1.25
2440
1.2418
2460
1.2337
2480
2258
2500
25(^(1
2620
2680

21S1
958
1748
L55r
2520 .2105
2540
2580 887
2600
2640
2700
[68 [
1487
2660
2720
203
S17
1.1615
1.1425
13
2740
2800
2860
2920
2980
i
1.1364
1
1.1189
'
1.1024

:
1.0868
1
1.0721
12760
2820
i
2880
! 2940
3000
1
1.1305
1.1133
1.0917
'
1.0818
1.0674
2780
2840
2900
•
2960
1.1246
1.1078
1.0919
1.0769
1.2.4.
Xif
ly ph6 gamma
[6]

Muc
dich ghi
nhan pho
aamma
la xac dinh
nana luana
va dien
tich
cac
dinh pho lam ca so cho viec nhan dien nguyen to va xac dinh hoat do phong
xa. Pho gamma don nang gom hai phan chfnh: Dinh quang dien va nen
compton. Phan cua pho gamma thuang do su dong gop cua cac loai
bii'c
xa
nhu phong xa tu nhien tu cac vat lieu cua detector, tu dat da, khong
khi
xung
quanh detector, tii cac tia vu
tru
Trong nhieu truang hgp phong gay anh huang rat
Ian
den chat lugng
ph6
gamma vl the viec che chan la rat can thiet, thong thuang nguai ta hay
sir
dung
chi
lam vat lieu che chan han che phong phong xa. Trong thuc nghiem
nang lugng cua buc xa gamma ung vai cac dinh quang dien co the' xac dinh
bang viec chuan nang lugng. Hoat do phong xa dugc xac dinh dua tren dien

tich
cua cac
dinh
pho. Co hai phuang phap
chinh
de xac dinh dien
tich
dinh
pho gamma la phuang phap so va phuang phap lam khap pho. Ngoai cac
phuang phap so, ngay nay nha cong cu may
tinh
dien tu phat trien, phuang
phap lam khap de
tinh
dien tfch
dinh
pho ngay cang dugc su dung nhieu nhat
la doi vai cac
ph6 ciia
buc xa gamma. Noi dung
ciia
phuang phap la khap cac
so lieu cua dinh vai mot ham giai
tich thich
hgp va phan
tich
ham do de tfnh
dien tfch.
Thong thuang cac dinh dugckhap theo dang Gauss va coi phong la ham tuyen
tfnh hay ham bac hai. Vai thong ke

vira
du cac dinh se co dang gan Gauss khi
do chat lugng khap se tot nhat. Neu thong ke so dem qua
Ian
hoac qua nho
dinh se lech khoi dang Gauss dan den sai so trong viec
tinh
dien tfch cac dinh.
Chiing toi da su dung chuang trinh lam khap la
Canberra-SlOO.
Cac chuang
trinh nay co
tdc
do phan tfch nhanh, co the phan biet va lam khap hau het cac
dinh vai chat lugng tot trong sai so cho phep. Chuang trinh nay dugc cai dat
tren cac may tfnh ca nhan , co the' vua ghi nhan vua xu ly
ph6.
Viec phan tfch
pho CO
the' tu dong hoa mot phan sau khi da thuc hien cac quy trinh nhu thiet
lap
ciic
thong so can thiet
chuiin
nang luang, do phan giai, hieu suat
*^hi
Phan tfch pho
sudung
cac chuang trinh may tfnh co
toe

do cao xu
Iv
nhanh co
the nhan biet va xu ly hau het cac dinh vai chat
lucprng
lot co the tach
ducrc
cac
dinh chap nhau mot phan. Cac so lieu thu duac cho biet dav du cac thong tin
ve pho gamma nhu nang luang, dien tfch, do phan giai cua cac dinh gamma.
so dem
phong cung
vc'ri
cac sai
so
phan tfch, thai gian
d() De ct) dune
cac
thong tin chfnh xac ve cac dong vi, he pho ke gamma
phai en dn
phan
giai
nang luang tot,
vice
chuan nang luong phai dam bao do chinh xac cao.
14
1.2.5.
Phuang phap tfnh toan [61
a) Phuang phap tuvet doi.
Hoat do rieng (Bq/Kg) cua nguyen to can xem xet tfnh tai thai diem do

mau
la:
ni.£,f .1
trong do: A la hoat do rieng cua
mau
phan tfch (Bq/Kg)
N la dien tfch cua dinh tia gamma tai nang lugng E
(tiic
so xung
tong cong trong thai gian do)
B
la hieu suat ghi tuvet doi
(%)
f
la hieu suat phat cua tia gamma tai nang luang dinh dang xet
(%)
t la thai gian do mau phan tfch (gy)
k la he so tro hoa, k =
ni.
I
no
I
m
la
khoi lugng mau phan tfch (kg)
b) Phuang phap tuong doi.
Phuang phap tuong doi dua tren su so sanh ham lugng
ciia
mot dong vi
can

xac dinh vai ham lugng cua no trong
mdu
chuan, vl vay trong khi chon mau
chuain can phai dam bao matrix cua mau phan tfch va
mSu
chuan la giong
nhau. Ham lugng cua mau phan tfch dugc tfnh theo mau chuan nhu sau:
S tn
i
m
C HI
A^, A^.
la ham lugng
ciia
mau phan tfch va mau chuan tuong ung (ppm/Kg)
hoac
(%)
m„,
m^
la khoi lugng
miu
phan tfchva mau chuain tuong ung (kg)
S,^, S^
la dien tfch dinh da
trii
phong
ciia
tia gamma trong mau phan tfch va
miiu
chuain tuong ung (xung/gy)

c) Mau chuain.
Mau chuan dugc chuain bi bang
each
them vao mot lugng da biet
ciia
dong
vi lam chuain va chat
n^n
(co thanh phan giong mau phan tfch). Co nhieu
phuang phap chuain bi nguon chuain nhu phuang phap hoa hoc, phuang phap
ca hoc. Ca hai phuang phap nay
d6u
dam bao yeu cau sau:
- Chat nen phai sach phong xa
- Ham lugng cac nguyen to
ciia
n^n
xap xi vai mau phan tfch.
- Cac dong vi chuan phan bo deu trong
nt^n.
De danh gia phong phong xa
srin
co trong
nt^n
nguai ta diing phuang phap
them chuan, tu do ngoai suy
dirge
hoat do rieng cua nen.
Mau
chuan

diroc
su dung trong thuc nghiem do cac mau dat a day c(') kfch
ihucVc,
khoi luong. thanh phan
nhu
sau:
Duong kfnh
irong
cua
h(">p man
1,}
cm
15