空气中氡的测量
氡、氡气（ Randon）
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氡气是地球放射性物质衰退时的自然产物，由土
壤、岩石、水泥、砂中，缓慢释出，无色、无
味，比重是空气七倍半，
是自然界惟一天然放射性气体。
常温下氡及子体在空气中能形成放射性气胶。附
着在颗粒物上，更容易被呼吸系统截留，滞留体
内，
一年肺部每四百个细胞就有一个细胞会因α粒子穿
过而突变，容易造成DNA损伤，增加患癌症的可
能性。
氡的衰变
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氡由铀238（238U)衰变产生。
氡会自发产生衰变，形成其他放射性金属粒
子的系列子元素，包括钋、铅210及铋等，
合称为子体（Radon daughters。
从放射性氡衰变到稳定的铅的时间约为25年
在衰变中产生的放射性物质，如可衰变物质
的含量过大，即放射性物质的“比活度”过
高，则对人体有害。
氡衰变成固体微粒
氡及其子体
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氡（radon）是不活泼的惰性气体，有
三种同位素：222Rn（镭射气，Rn），
220Rn（钍射气，Tn），219Rn（锕射
气，An）
219Rn半衰期仅3.96秒，从产生地点到
人类呼吸带之前就基本衰变完毕，卫生
学意义较小。
220Rn半衰期55.6秒，在特定环境下有
一定的卫生学意义。
通常说的氡是222Rn
氡的子体（daughters）
核素
主要衰变类型
半衰期
a粒子能量（MeV）
222Rn
a
3.824d
5.49
218Po（RaA）
a
3.05min
6.0
214Pb
（RaB）
β，γ
26.8min
214Bi
（RaC）
β，γ
19.9min
214Po
（RaC’）
a
164us
210Pb
（RaD）
β，γ
21a
210Bi
（RaE）
β
5.01d
210Po
（RaF）
a
138.4d
206Pb
（RaG）
稳定
7.69
5.3
基本定义
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氡子体：222Rn的短寿命子体
氡：222Rn本身及其子体
氡浓度：222Rn的浓度
氡子体的照射常被称为暴露
氡的浓度
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Bq/m3
Ci/L
3.7Bq/L=10-10Ci/L
氡的危害
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氡是气体，吸入后全身很快与环境中的氡平
衡，离开后经肺快速排出
氡的子体是金属粒子，吸入后沉积在呼吸道
表面，不断衰变
含氡气体对人体的危害主要不是来自氡而是
氡的短寿命子体的a照射。
氡的来源
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室内氡约20%来自建材。80%室外渗入。
天然石材由于产地、地质结构和生成年代不
同，其放射性也不同。
火成岩类建材(尤其是花岗岩石材)含有放射
性元素，特别易释放出氡。
释出氡的建材有砖沙、水泥、石子、瓷砖及
石膏，建材中典型之氡~40Bq/kg。
温泉中也可能存在有放射性氡元素存在。
氡的危害
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氡对人的辐射伤害占一生全部辐射伤害>55%
氡诱发肺癌的潜伏期在15年以上，世界上1/5肺癌与氡有关。
氡是除吸烟外肺癌的第二大因素，WHO列为致癌的19种物
质之一。美国每年5000~20000人因氡产生肺癌，占肺癌总
数10~14%。
氡气混合二手烟对健康危害至巨大。在同一氡气量的环境下，
吸烟者患上肺癌的机会要比非吸烟者为高
氡对人体脂肪有高亲和力，影响神经系统，使人精神不振，
昏昏欲睡。暴露氡气的工人，除上呼吸道疾病及肺癌外，也
有慢性肾炎，与氡蜕变为肾毒性的放射性铀有关。增加孕妇
自然流产及畸形儿机率。
氡的暴露
Outdoor
Population-weighted average
Max./min. (Region average)
In world
14Bqm-3
~12
10Bqm-3
Overview
Indoor
Population-weighted average
Max./min. (Region average)
In world
24Bqm-3
~6
39Bqm-3
Thoron concentration in dwelling in China
Region and period
Hubei 80’ period
Guangdong 84-86
Baotou 80’ period
Shanxi 80’ period
Beijing 2000
Beijing 2000
Zhuhai 2000
Hongkong
World
number of Points
37
220
8
895
10
54
EEC(Bqm-3)
0.5(0.03~0.6)
1.13
0.65
1.07
0.8(<LLD~1.7)
1.41(0.4~3.08)
2.7(0.03~4.7)
0.75
0.3
Outdoor Thoron Concentration in China
Region
Period number of points
mean range（EEC Bq m-
3）
Hubei
43
Guangdong
1984～1986
Baotuo
1984
Shanxi
1985～1987
World
110
0.18
0.03-0.82
0.5
4
0.49
337
0.49
0.1
0.08-3.6
Occupational Radon exposure level
Radiation exposures to workers in underground mine
and workplace
individual dose, mSv/a
Typical value
Range Collective
Type of work
dose
Underground mine
4.8
2.88×104
Underground non-ferric metal mine 16
>9.6×102
Underground iron mine
12.8
Other underground mine
Underground workplace
4
Cavern
8
Tunnel
30
0.36-18
1-120
2.3-36
0.18-160
0.2-31
0.14-40
Rn Concentration in house built by
different materials
Concrete and brick
Wood-Soil
Cave
Underground room
Cinder added
18.9Bqm-3
38.4Bqm-3
60.9Bqm-3
480Bqm-3
242Bqm-3
The concentrations of Rn in dwelling with cinder-added construction
Area
Hubei
Number of room
8
Rn concentration, Bq/m3
Average
Range
64
20.9 -125.3
Hunan
20
281.2
Huangshan
63
235
Anhui
87
89.2
15.4-1244
Guizhou
10
100.6
64.4-138.5
Jiangxi
30
315
120-570
Xiushi
20
446
180-640
Fujian
4
121
242
206.5
total
189.6 -550.4
15.4-1244
Internal exposure arising from Rn and Tn in Soil/woody
structural dwellings mSv a-1
Location
Gansu
Dwelling
Cave house
Rn
0.69
Tn
7.18
Total
Tn/Rn ratio
7.87
10.4
Earth/woody structure
0.89
2.62
3.51
2.9
Hengyang Earth/woody structure
0.36
5.3
5.66
14.7
The population of high Radon
exposure level
232Th
Content in soil (Bq/kg)
Country
China
India
Malaysia
Thailand
U.S.A
World median
Concentration
Mean
Range
49
1-438
64
14-160
82
63-110
51
7-120
35
4-130
30
The population of high Radon
exposure level
232Th
Content in Soil in China (Bq kg-1)
Concentration
Region
Mean
Range
Fujian
96.3
19.5-260
Zhang Zhou
109
17.8-190
Xia Men
93.5
66.1-125
Zhu Hai
193
11-345
Hongkong
146
Radon monitor
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Active radon monitor with negative
pressure
Passive radon monitor without negative
pressure
氡的测量
passive techniques
Charcoal
Track etch detectors
Electret detectors
Active techniques
Gas concentration
Lucas cells
Ionisation chamber
Gas and progeny concentration
Alpha total count analysis
Alpha-Spectroscopy
(Beta proportional counter)
Why passive techniques?
Passive techniques are more than electricitysaving!
Easy to handle by unskilled staff!
Cheap, well approved!
Recommended choice in long-term screening
measurements
Passive techniques give just one value - no need
to discuss anything but the average!
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Why active techniques?
They do not need any (or just a few) additional
laboratory work!
Fast detection at site!
Low limit of detection isn´t influenced by the
sampling time but the sensitivity of the system
(detector size, chamber volume, integration time)
Recommended choice for the case study concerning
special characteristics of building or time variation!
Fig. 1 Radon & Thoron Dosimeter
Absorber
Hook
CR-39SSNTD
Sampling chamber
Radon & thoron
Diffusion window
Fig. 2 The schematic diagram of passive and integrated thoron
dosimeter with absorber
Thoron monitoring technique with absorber
CR-39SSNTD
222Rn
218Po
214P
o
212Po
65.6μm
polycarbonate
(a)
(b)
Fig.3 The principle of discriminating radon with absorber
The sensitive thoron monitoring technique
with electret
+
216Po+ 212Pb+
Radon & thoron
Fig.4 Collection of the electrostatic field to charged thoron progenies
Fig.5 The simple radon/thoron chamber
P
Scintillation cell
Chamber
AB-5
·2
P
·1
·3
·5
·4
P
(a)
Thoron chamber
(b)
Chamber
Fig.6 The schematic diagram of a simple thoron chamber
P Pump
Volve
Flowmeter
Filter
Source
Desicator ·Sampling hole
2.5
800
2
700
600
1.5
500
400
1
300
Thoron Calculation
Thoron measurement
Radon calculation
200
0.5
100
0
0
0
10
20
30
40
50
Depressurisation(in cmHg)
Fig.7 Variation of exhalation rate with depressurization
60
Radon exhala tion rate(mBqm-2 s -1 )
Thoron exhal ation rate(mBqm-2 s -1 )
900
2.5
800
2
700
600
1.5
500
Thoron calculation
Thoron measurement
Radon calculation
400
1
300
200
0.5
100
0
0
0
0.2
0.4
0.6
0.8
1
Distance from tube center(m)
Fig.8 Variation of exhalation rate with distance from vacuum location
Radon exhalati on rate(mBqm -2 s -1 )
Thoron exhalat ion rate(mBqm -2 s- 1 )
900
Small chamber dimension = short flight distance!
Another solution: 12cm³ chamber volume and diffusion
Isolation
Shielding
Leather Membrane
Housing
Screen
PVC-Isolation
Chamber Wall
Rubber Seal
Detector
About ... attached and unattached fraction
Screen
Impactor stage
Back-up filter
Online α-impactor with electronics
(active)
Activity size distribution 218Po
3,25 nm
0,45
nucleation mode:
AMDn = 25 nm
n = 2,5
fn
= 16 %
0,4
1939 nm
1 / C * ( C /  (ln d))
0,35
1095 nm
626 nm
343 nm
accumulation mode:
AMDa = 320 nm
a
= 2,5
fa
= 83 %
0,3
0,25
0,2
0,15
0,1
0,05
158 nm
0
1 d [nm]
72 nm
Back up
10
100
1000
10000
100000