The Processes of Three Natural Decay
Series in Underground Strata and Their
Common Characteristics
Wei Zhang
Associate researcher, IoT Perception Mine Research Center, China University of
Mining & Technology, Xuzhou, Jiangsu, 221008, China; The National and Local
Joint Engineering Laboratory of Internet Technology on Mine, China University
of Mining & Technology, Xuzhou, Jiangsu 221008, China; School of Environment
Science and Spatial Informatics, China University of Mining & Technology,
Xuzhou, Jiangsu, 221116, China
Corresponding author, e-mail: zhangwei@cumt.edu.cn
Dongsheng Zhang
Professor, School of Mines, China University of Mining & Technology,
Xuzhou, Jiangsu 221116, China
e-mail:dshzhang123@126.com
Lixin Wu
Professor, IoT Perception Mine Research Center, China University of Mining &
Technology, Xuzhou, Jiangsu, 221008, China; The National and Local Joint
Engineering Laboratory of Internet Technology on Mine, China University of
Mining & Technology, Xuzhou, Jiangsu 221008, China; School of Environment
Science and Spatial Informatics, China University of Mining & Technology,
Xuzhou, Jiangsu, 221116, China
e-mail: awulixin@263.net
Xufeng Wang
Professor, School of Mines, China University of Mining & Technology,
Xuzhou, Jiangsu 221116, China
e-mail: wangxufeng@cumt.edu.cn
ABSTRACT
In order to apply the radon technique to the detection of mining-induced fractures in overlying strata
with greater confidence, some fundamental knowledge of high energy physics must be understood. In
this paper, based on composition of substance (including atom and nucleus), the types and basic rules
for radioactive decay of a nuclide had been summarized. Moreover, the processes of three natural
decay series in underground strata and its common characteristics had been analyzed. The analysis
results indicate that all of their initial nuclides have relatively long lifetimes, all of their final products
are stable isotopes of plumbum after undergoing a series of radioactive decays, all of their mass
numbers follow a trend and all of these decay processes produce radioactive gases.
KEYWORDS:
coal mining; radon detection; mining-induced fractures; radioactive decay;
natural decay series
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Vol. 21 [2016], Bund. 02
710
INTRODUCTION
Radon is a chemical element with a chemical symbol Rn, it is a direct decay product of radium. In
nature, radon has three kinds of common radioactive isotopes. The three natural isotopes of radon are
219
Rn, 220Rn and 222Rn, with half-lives of 3.96 s, 55.6 s and 3.82 d, respectively. Due to the extremely
low concentration of 219Rn in the crust [1] and its short half-life, this isotope is usually undetectable.
Similarly, only a small amount of 220Rn is released from the crust, and it decays quickly due to its
short half-life. Indeed, the concentration of 220Rn in the crust is only 10% that of 222Rn, and the
overall quantity of natural 222Rn is significantly larger than that of natural 219Rn and 220Rn.
Additionally, the half-life of 222Rn is much longer than that of the other two isotopes.
In general, radon refers to 222Rn. It has a half-life of 3.82 days. Direct parent of 222Rn is radium
isotope (226Ra), and the indirect parent is uranium isotope (238U). The elemental form of radon
element is usually gaseous, which is the only radioactive heaviest inert gas in contact with human. In
normal state, it is colorless and tasteless and odorless, soluble in water and organic matter. The
chemical properties of radon are relatively stable, and it is difficult to produce chemical reaction with
other substances [2]. As radon is eventually from uranium decay, while uranium exists in coal, rock,
soil and water with certain content in nature, therefore, radon is ubiquitous in natural environment.
The activity of radon is very strong, and it has good migration ability in natural conditions. In
geological environment, radon can migrate by gaseous or dissolved form with ground and soil water.
Radon usually migrates by diffusion and convection effect in overlying strata, and the migration
distance from underground strata to surface depends on different lithological characters. For example,
the vertical migration distance in homogeneous sand is 360-420 m [3-5]. Moreover, the phenomenon of
increased radon concentration in surface oil above spontaneous coal combustion area at 400 m depth
had been observed in China [6]. These show that radon can migration to surface from underground
coal strata of 400-500 m depth.
Because radon has radioactivity, even if its concentration is very low, it also can be measured.
Meanwhile, radon has the geophysical-chemical properties of inert gas, thus it can migrate and
accumulate in micropores or microfractures. Radon formed by radioactive decay in underground coal
strata can penetrate surface into air, which provides a basis for detecting radon on surface. For
instance, German scholars found that abnormal radon concentration in surface soil above the mininginduced area of deep shaft mining [7]. In this literature, the specific mining depth did not been
explained, but we also could deduce that vertical migration distance is more than 400 m at least.
At present, attempting to apply the geophysical-chemical properties of radon in the field of
mining engineering, importing the radioactive measurement methods to detect the dynamic
development process of mining-induced fractures and its aquosity in overlying strata of underground
coal mining, which is still in preliminary stage [8-14]. In order to apply the radon technique to the
detection of mining-induced fractures in overlying strata with greater confidence, some fundamental
knowledge of high energy physics must be understood. In this paper, based on composition of
substance (including atom and nucleus), the types and basic rules for radioactive decay of a nuclide
had been summarized. Moreover, the processes of three natural decay series in underground strata
and its common characteristics had been analyzed.
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711
COMPOSITION OF SUBSTANCE
Atom
Elements in nature are composed of atoms. Atoms have different masses and sizes whose radii
are in the range of 10-10～10-12 m. Generally, each atom is composed of a nucleus and electrons
orbiting around the nucleus, so it has no net electric charge.
Nucleus
A nucleus consists of nucleons, in which neutrons and protons are the fundamental building
blocks of nucleon. These nucleons move along different orbits inside the nucleus. Nucleus has a
positive charge because neutrons are neutral while proton has a positive charge. The amount of
charges possessed by the nucleus is equivalent to the charges of electrons orbiting around the nucleus.
Generally, e (e=1.6021×10-19 C) represents the number of charges of a single electron. The mass of a
single electron is 9.1091×10-25 kg. The mass of a single proton is 1.6725×10-21 kg, which is 1836
times heavier than an electron. The mass of a single neutron is 1.6748×10-21 kg, which is slightly
heavier than a proton. Generally, an atom bears no net charge because the number of surrounding
electrons equals to the number of proton in the nucleus. The mass of an atom is concentrated on
nucleus and hence, its mass is the sum of proton (Z) and neutron (N) in nucleus and is termed mass
number (A = Z + N). The radius of a nucleus R is 1.5x10-13 A1/3, indicating that the volume of a
nucleus is also proportional to A.
For an element (X), all protons (Z) and neutrons (N) located inside a nucleus are generalized as
nucleon. Atomic number (Z) represents the number of proton inside a nucleus and hence, the total
charge of a nucleus is Ze. Nucleuses with same atomic number (Z) are surrounded by the same
number of electrons and those elements show similar chemical properties. In other words, same
element must have the same number of proton but could have different number of neutron (N). Thus,
their mass numbers (A = Z + N) could be different. Atoms or nucleuses containing a certain number
of protons and neutrons are called nuclides, which notation can be expressed as AZ X . Nuclides with
same number of protons but different number of neutron are called isotopes. For example, isotopes of
238
uranium are 235
92 U and
92 U .
RADIOACTIVE DECAY
Energy level of nucleus
The nuclear stability is tied with the neutron-to-proton ratios inside the nucleus, in which excess
number of proton or neutron causes nuclear instability. Modern high energy physics indicates that a
particle system can only take on certain discrete and discontinuous values of energy state. Each
discrete energy state represents different energies and the amount of energy possessed by the atoms at
certain state can be described as energy level. Generally, ground state is the lowest possible energy
level and all the nuclides in this state are stable. Any energy state that is higher than ground state is
called excited state. Nucleuses in an excited state are unstable and tend to return back to ground state
by dissipating excess energy using different ways. As illustrated in Figure 1, the excited states of a
Vol. 21 [2016], Bund. 02
712
nucleus can be categorized according to their energy levels, such as first excited state, second excited
state, third excited state, etc.
… … …
The fourth excitation level
The third excitation level
Excitation state
The second excitation level
The first excitation level
Ground state
Figure 1: Excitation level of atomic nucleus
Radioactive decay
Some elements are unstable in nature because their nuclei are in an excited state. These nuclei
tend to undergo structural change and transform into another kind of nuclei. At the same time, the
nuclei dissipate excess energy by emitting radiations (α-ray, β-ray, γ-ray). This phenomenon is termed
radioactive decay or nuclear decay. Elements that undergo nuclear decay are called radioactive
nuclides (isotopes). Generally, nuclei with proton number Z > 82 are categorized as radioactive
nuclides because they are unstable in nature.
In general, there are three common types of radiation decays:
1. α-decay
α-decay is a type of radioactive decay in which a nucleus ejects an α-particle spontaneously and
thereby transforms into another kind of nucleus. The α-particle that consists of 2 protons and 2
neutrons is identical to a high-velocity helium nucleus, 42 He . It is a positively charged particle with
kinetics energy of about 4～9 MeV.
The mass number, A, of a parent nuclide is reduced by 4 and its atomic number, Z (nuclear
charge), is reduced by 2 after α-decay. Therefore, a new element that is 2 places to the left in the
periodic table than the original element is formed. The generic equation of a α-decay can be
represented as follows:
A
Z
X →
Y + 42 He
A -4
Z-2
(1)
In this equation, X, Y, A, and Z represent the parent nucleus, the daughter nucleus, the mass
number of the parent nucleus (atomic weight), and the atomic number of the parent nucleus (proton
number).
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713
2. β-decay
β-decay is a type of radioactive decay in which a nucleus ejects a β-particle (electron)
spontaneously or captures an electron and thereby transforms into another kind of nucleus. There are
three types of β-decays which are known as β‾-decay, β+-decay, and electron capture.
β‾-decay is a process that a neutron in the parent nuclide converts into a proton and
simultaneously induces the emission of an electron (β‾) and electron antineutrino ( v ). β‾ particle is a
high-velocity electron that has identical mass with a stationary electron and bears a negative charge.
The mass of a β‾ particle is far lighter than a nucleus, thus, the mass number of a parent nuclide is
identical its daughter nuclide. A new element that is 1 place to the right in the periodic table than the
original element is formed. The generic equation of a β‾-decay can be represented as follows:
A
Z
X → ZA+1Y + β − + v
(2)
In this equation, electron antineutrino ( v ) is neutral with a mass of 1/2000 of an electron.
β+-decay is a process that a proton in the parent nucleus converts into a neutron and
simultaneously induces the emission of an electron (β+) and electron antineutrino ( v ). β+ particle is a
high-velocity electron that have identical mass with a stationary electron but bears a positive charge.
Thus, the mass number of the parent nuclide is identical with the daughter nuclide. A new element
that is 1 place to the left in the periodic table than the original element is formed. The generic
equation of a β+-decay can be represented as follows:
A
Z
X → ZA−1Y + β + + v
(3)
The capture of orbital electron is a decay process in which a parent nuclide absorbs an atomic
electron from outer shell. This process converts a proton to a neutron and simultaneously induces the
emission of an electron neutrino. Thus, the mass number of the parent nuclide is identical with the
daughter nuclide. A new element that is one place to the left in the periodic table than the original
element is formed. The generic equation of an electron capture process can be represented as follows:
A
Z
X + β − → ZA−1Y + v
(4)
3. γ-decay
γ-decay is a radioactive decay in which an unstable daughter nuclide that has been through an α/β-decay changes from a higher energy state to a lower energy state through the emission of γ-photons.
Thus, the mass number (A) and atomic number (Z) remain unchanged after γ-decay.
The basic rules for radioactive decay of a nuclide
Everything in nature follows some basic rules. If a radioactive nuclide is collected, we will find
that its amount may reduce gradually owing to radioactive decay. A radioactive nuclide changes into
another kind of nuclide during a radioactive decay process. Although radioactive decay is a random
process, it still follows some statistical behaviors and mathematical exponential formula. Four
different physical quantities can be used to describe the basic rules for radioactive decay of a nuclide,
including decay constant, half-life, mean lifetime, and radiation activity.
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714
1. Decay constant (λ)
The decay rate of a radioactive nuclide can be represented as dN/dt in which dN is the number of
nucleus that decays within time t to t + dt [15-16]. Experimental study showed that dN is proportional to
the number of undecayed nucleus within time interval dt, which can be expressed as follows:
dN
= −λN
dt
(5)
In this equation, λ represents the decay constant of a radioactive nuclide and “-” sign shows that
the decay rate is decreasing.
The basic rule of radioactive decay can be derived from integrating equation (5) by which t = 0
and the initial amount of nucleus is N0. It can be expressed as follows:
N = N 0 e − λt
(6)
In this equation, N represents the number of nuclei of radioactive nuclide at a given time t, N0
represents the number of initial nuclei of radioactive nuclide at t = 0, and λ represents the decay
constant of a radioactive nuclide.
From equation (5) and (6), decay constant is the probability at which the nuclei decreases because
of radioactive decay per unit time and thus, its unit is s-1.
2. Half-life (TB)
Half-life, TB, is the time required to for the number of nuclei to fall to half of its initial amount.
When half-life is defined as N = N0/2, equation (6) can be written as follows:
TB =
λn 2
≈
λ
0.693
(7)
λ
From equation (7), the number of nuclides remains after 10 half-lives is calculated to be
N = N 0e −10 lTB =
N0
N
= 0 . At this stage, the radioactive nuclide has been decayed completely.
10 ln2
e
1024
3. Mean lifetime (τ)
The decay time of nuclides differs from each other because the radioactive decay is a random
process. Thus, they have different lifetimes. Lifetime is defined as the time of existence of radioactive
nuclide and mean lifetimes is referred to the average time of existence of the majority unstable
nuclides. Therefore, τ can be calculated based on the following equation:
t=
1
N0
∫
∞
0
∞
1
0
λ
λNtdt = ∫ te −λt dt =
4. Radiation activity (radiation intensity)
≈ 1.44TB
(8)
Vol. 21 [2016], Bund. 02
715
Units λ, TB, and τ are used to express the decay rate of a radioactive nuclide but they are not
related to the number of nucleus. In practical application, both the decay rate and the radiation
intensity or so-called radiation activity are essential. Radiation activity (radiation intensity) is the
amount of nucleus that decay or the number of emitted radiation per unit time [17-20], which is
generally expressed in Nλ. Therefore, radiation activity is associated with both decay constant (λ) and
the number of nucleus (N) in an atomic nuclide.
Previously, radiation activity is measured in units of curie (Ci), milicurie (mCi), microcurie (μCi),
and picocurie (pCi) (1 Ci = 103 mCi = 106 μCi =10 12 pCi). Nowadays, becquerel (Bq) is the unit of
radioactivity in the International System of units (SI), which is defined as one radioactive decay per
second. Therefore, the SI unit of the concentration of Radon is Bq/m3, which refers to the number of
decay per unit volume and time. The conversion between curie and becquerel is 1 Ci= 3.7e10 Bq.
Natural decay series
Decay series is a group of elements that consists of parent nuclide and its daughter nuclides in the
periodic table. Natural decay series is referred to a collection of naturally occurring radioactive
nuclides. Three main natural decay series are observed in nature, which are the uranium series
(uranium-radium series), thorium series, and the actinium series (actinium-uranium series) [21-23].
Their atomic numbers are in the range of 81~92. Majority of the nuclides in these three series emit γray during α- and β-decays.
1. Uranium series (uranium-radium series)
Uranium series includes 15 nuclides. The decay process is illustrated in Figure 2. This series
238
9
begins with 238
92 U which has a relatively long half-life (4.5×10 a). Beginning with the
92 U , it
undergoes 8 times of α-decays and 6 times of β-decays before converting into a stable nuclide
The decay process can be expressed as follows:
238
92
In uranium series,
238
92
4
0
U → 206
82 Pb +8 2 He + 6 -1 e + (γ )
226
88
Rn
include
(9)
Ra with a half-live of 1600 a. Then,
α-decay to convert into the only gaseous radioactive nuclide
nuclide
Pb .
U undergoes 3 times of α-decays and 2 times of β-decays before
converting into a radioactive nuclide
222
86
206
82
daughter
nuclides
with
222
86
short
226
88
Ra undergoes an
Rn in this series. The isotopes of
half-live,
e.g.
218
84
Po (TB=3.1
214
214
-4
min), 214
82 Pb (TB=26.8 min), 83 Bi (TB=19.7 min), 84 Po (TB=1.64×10 min) and daughter nuclides with
long half-live, e.g.
210
82
Pb (TB=22.3 a),
210
83
Bi ( TB=5 d), 210
84 Po ( TB=138.4 d).
Vol. 21 [2016], Bund. 02
238
234
U
4.5e9 a
716
Th
24.1 d
234
Pa
1.17 min
6.75 h
234
230
U
2.45e5 a
226
Th
7.7e4 a
222
Ra
1600 a
Rn
3.82 d
218
214
Po
3.1 min
214
Nuclide symbol
Atomic number
A
Z TB
U: 92
α-decay
Pa: 91
Th: 90
β-decay
X
X: Nuclide
A: Mass number
Z: Atomic number
TB: Half-life
Decay mode
Bi
19.7 min
214
Ac: 89
Pb
26.8 min
210
Po
-4
1.64e s
Pb
22.3 a
γ photon
Ra: 88
210
Rn: 86
Bi
5.0 d
Po: 84
Bi: 83
210
Pb: 82
Po
138.4 d
206
Pb
Stable state
Figure 2: Decay process of uranium series ( 238
92 U )
2. Thorium series
Thorium series includes 12 nuclides. The decay process is illustrated in Figure 3. This series
10
begins with 232
a). Generally, 232
90 Th which has a relatively long half-life (1.4×10
90 Th undergoes
6 times of α-decays and 4 times of β-decays before converting into a stable nuclide
decay process can be expressed as follows:
232
90
4
0
Th → 208
82 Pb + 6 2 He + 4 -1 e + (γ )
208
82
Pb . The
(10)
The decay process of thorium series is much more simply than uranium series. In addition, the
lifetime of isotopes in thorium series is also shorter than those in uranium series. In thorium series,
232
90 Th undergoes 3 times of α-decays and 2 times of β-decays before converting into a radioactive
nuclide
224
88
Ra with a half-live of 3.64 a. Then,
only gaseous radioactive nuclide
shorter than the half-life of
222
86
220
86
224
88
Ra undergoes an α-decay to convert into the
Rn in this series. However, it has a half-life of 55.6 s which is
Rn (3.82 d) in uranium series.
Vol. 21 [2016], Bund. 02
232
228
Th
10
717
Ra
5.75 d
1.4e a
228
Ac
6.13 h
228
Th
1.91 a
224
220
Ra
216
Rn
55.6 s
3.64 a
212
Po
10.6 h
0.15 s
212
Nuclide symbol
Atomic number
A
Z TB
Th: 90
Ac: 89
α-decay
X: Nuclide
A: Mass number
Z: Atomic number
TB: Half-life
Ra: 88
Rn: 86
β-decay
Po: 84
γ photon
X
Decay mode
Pb
208
Bi
60.6 min
212
Po
-7
3e s
Tl
3.05 min
208
Pb
Stable state
Bi: 83
Pb: 82
Tl: 81
Short
process
Figure 3: Decay process of thorium series ( 23290Th )
3. Actinium series (actinium-uranium series)
Actinium series includes 13 nuclides. The decay process is illustrated in Figure 4. The decay
process in actinium series is much more complicated than that of either uranium or thorium series. In
addition, the lifetime of isotopes in actinium series is even shorter than those in thorium series. This
235
8
series begins with 235
92 U which has a half-life of 7.1×10 a. In actinium series,
92 U undergoes
several times of α- and β-decays before converting into a stable nuclide
series, gaseous radioactive nuclide
219
86
207
82
Pb . Similar to other
Rn is also released during the decay process. It has a half-life
of 3.96 s, which is much shorter than the half-life of
222
86
Rn (3.82 d) in uranium series.
Vol. 21 [2016], Bund. 02
235
231
U
7.1e8 a
718
Th
25.5 a
231
227
Pa
3.25e10 a
Ac
21.7 a
227
223
Th
18.8 d
Ra
11.44 d
219
Rn
3.96 s
Nuclide symbol
Atomic number
A
Z TB
U: 92
α-decay
Pa: 91
Th: 90
β-decay
X
X: Nuclide
A: Mass number
Z: Atomic number
TB: Half-life
215
211
Po
-3
1.78e s
211
Decay mode
207
Bi
2.14 min
211
Po
0.52 s
Ac: 89
Pb
36.1 min
Tl
4.79 min
207
Pb
Stable state
Ra: 88
Rn: 86
Po: 84
Bi: 83
Pb: 82
Tl: 81
Figure 4: Decay process of actinium series ( 227
89 Ac )
CONCLUSION
There are some common characteristics in the decay process among these three natural decay
series (uranium, thorium, and actinium) as follows:
(1) All of their initial nuclides have relatively long lifetimes, which are in the range of 108~1010 a.
Therefore, these 3 series can exist for very long in nature.
(2) All of their final products are stable isotopes of plumbum after undergoing a series of
208
207
radioactive decays, which are 206
82 Pb (uranium series),
82 Pb (thorium series), and
82 Pb (actinium
series).
(3) All of their mass numbers (A) follow a trend, in which the mass number of nuclides in
uranium series is A=4n+2 (n=51~59), the mass number of nuclides in thorium series is A=4n
(n=52~58), and the mass number of nuclides in actinium series is A=4n+3 (n =51~58).
(4) All of these decay processes produce radioactive gases (emanation), which are indicated by
black circles in Figure 2~4. These emanations are the isotopes of radon with an atomic number of 86,
Vol. 21 [2016], Bund. 02
719
220
219
which are 222
86 Rn ,
86 Rn , and
86 Rn . All of them are inert gases. They are known as uranium
emanation, thorium emanation, and actinium emanation.
ACKNOWLEDGEMENT
The research is financially supported by the National Basic Research Program of China (No.
2015CB251600), the National Natural Science Foundation of China (No. 51404254), the China
Postdoctoral Science Foundation (Nos. 2014M560465 and 2015T80604), the Jiangsu Planned
Projects for Postdoctoral Research Funds (No. 1302050B), the Fundamental Research Funds for the
Central Universities (No. 2013QNB24) and the Research Fund of Key Laboratory of Safety and
High-efficiency Coal Mining, Ministry of Education (JYBSYS2015106). We wish to thank Doctor
Wei Zhou from the Chengdu Univerisity of Technology for the assistance of literature collection.
Special thanks are given to Doctor Juanjuan Li from the China University of Mining & Technology,
for her language assistance. The authors are also grateful to the editor and anonymous reviewers for
their helpful comments and constructive recommendation.
REFERENCES
1.
Baixeras, C., Erlandsson, B., Font, L., and Jonsson, G. (2001) “Radon emanation from soil
samples,” Radiation Measurements, Vol. 34, No. 1-6, pp 441-443.
2.
Zhuo, W., Iida, T., Moriizumi, J., Aoyagi, T., and Takahashi, I. (2001) “Simulation of the
concentrations and distributions of indoor radon and thoron,” Radiation protection
dosimetry, Vol. 93, No. 4, pp 357-368.
3.
Villalbaa, L., Colmenero Sujo, L., Montero Cabrera, M. E., Cano Jimenez, A., Renteria
Villalobos, M., Delgado Mendoza, C. J., Jurado Tenorio, L. A., Davila Rangel, I., and
Herrera Peraza, E. F. (2005) “Radon concentrations in ground and drinking water in the
state of Chihuahua, Mexico,” Journal of Environmental Radioactivity, Vol. 80, No. 2, pp
139-151.
4.
Tricca, A., Wasserburg, G. J., Porcelli, D., Baskaran, M. (2001) “The transport of U- and
Th-series nuclides in a sandy unconfined aquifer,” Geochimica et Cosmochimica Acta, Vol.
65, No. 8, pp 1187-1210.
5.
Calugaru, D. G., and Crolet, J. M. (2002) “Identification of radon transfer velocity
coefficient between liquid and gaseous phases,” Comptes Rendus Mecanique, Vol. 330, No.
5, pp 377-382.
6.
Wu, J. M., and Gao, S. Q. (2004) “Study on temperature detection technique at fire district
of coal spontaneous combustion and its application,” China Safety Science Journal, Vol. 14,
No. 10, pp 109-112.
7.
Rohnsch, W., Przyborowski, S., and Ettenhuber, E. (1992) “Investigation and evaluation of
the radiation exposure situation in uranium mining areas of Eastern Germany,” Radiation
Protection Dosimetry, Vol. 45, No. 1-4, pp 127-132.
8.
Zhang, W.; Zhang, D. S.; Wu, L. X.; and Wang, H. Z. (2014) “On-site radon detection of
mining-induced fractures from overlying strata to the surface: A case study of the Baoshan
Coal Mine in China,” Energies, Vol. 7, No. 12, pp 8483-8507.
Vol. 21 [2016], Bund. 02
9.
720
Zhang, W.; Zhang, D. S.; Wang, X. F.; Xu, M. T.; and Wang, H. Z. (2014) “Analysis of
mathematical model for migration law of radon in underground multilayer strata,”
Mathematical Problems in Engineering, Vol. 2014, No. 2014, pp 1-9.
10. Zhang, W., Zhang, D. S., Ma, L. Q., Wang, X. F., and Fan, G. W. (2011) “Dynamic
evolution characteristics of mining-induced fractures in overlying strata detected by radon,”
Nuclear Science and Techniques, Vol. 22, No. 6. pp 334-337.
11. Zhang, W., Zhang, D. S., and Fan, G. W. (2011) “Design of comprehensive test system for
detecting overlying strata mining-induced fractures on surface with radon gas,” Mining
Science and Technology (China), Vol. 21, No. 6, pp 823-827.
12. Zhang, W., Zhang, D. S., Ma, L. Q., Wang, X. F., Fan, G. W., and Xu, M. T. (2011)
“Development of a comprehensive test system for detecting mining-induced fractures in
overlying strata on surface with radon and its application,” Chinese Journal of Rock
Mechanics and Engineering, Vol. 30, No. 12, pp 2531-2539.
13. Bai, Q., Fang, F., and Li, X. (2011) “Study of correlation of fracture caused by coal mine
production and radon concentration,” Computing Techniques for Geophysical and
Geochemical Exploration, Vol. 33, No. 2, pp 175-178.
14. Zhang, W. (2012) “Mechanism Research on Detecting Mining-induced Fractures and Its
Aquosity in Overlying Strata by Radon on Surface,” Xuzhou: China University of Mining &
Technology PhD Thesis, pp 1-3.
15. Xue, S., Dickson, B., and Wu, J. (2008) “Application of 222Rn technique to locate subsurface
coal heatings in Australian coal mines,” International Journal of Coal Geology, Vol. 74, No.
2, pp 139-144.
16. Gutierrez, J. L., Garcia-Talavera, M., Pena, V., Nalda, J. C., Voytchev, M., and Lopez, R.
(2004) “Radon emanation measurements using silicon photodiode detectors,” Applied
Radiation and Isotopes, Vol. 60, No. 2-4, pp 583-587.
17. Sakoda, A., Ishimori, Y., and Yamaoka, K. (2011) “A comprehensive review of radon
emanation measurements for mineral, rock, soil, mill tailing and fly ash,” Applied Radiation
and Isotopes, Vol. 69, No. 10, pp 1422-1435.
18. Holub, R. F., and Brady, B. T. (1981) “The effect of stress on radon emanation from rock,”
Journal of Geophysical Research, Vol. 86, No. 3, pp 1776-1784.
19. Schubert, M., Paschke, A., Lieberman, E., and Burnett, W. C. (2012) “Air-water partitioning
of 222Rn and its dependence on water temperature and salinity,” Environmental Science and
Technology, Vol. 46, No. 7, pp 3905-3911.
20. Koike, K., Yoshinaga, T., Suetsugu, K., Kashiwaya, K., and Asaue, H. (2015) “Controls on
radon emission from granite as evidenced by compression testing to failure,” Geophysical
Journal International, Vol. 203, No. 1, pp 428-436.
21. Rama, and Moore, W. S. (1984) “Mechanism of transport of U-Th series radioisotopes from
solids into ground water,” Geochimica et Cosmochimica Acta, Vol. 48, No. 2, pp 395-399.
22. Porcelli, D., and Swarzenski, P. W. (2003) “The behavior of U-and Th-series nuclides in
groundwater,” Reviews in Mineralogy and Geochemistry, Vol. 52, No. 1, pp 317-361.
Vol. 21 [2016], Bund. 02
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23. Reynolds, B. C., Wasserburg, G. J., and Baskaran, M. (2003) “The transport of U-and Thseries nuclides in sandy confined aquifers,” Geochimica et Cosmochimica Acta, Vol. 67, No,
11, pp 1955-1972.
24. Diogo Henrique Fernandes da Paz, Francisco Cardoso dos Santos Neto, Kalinny Patrícia
Vaz Lafayette, Filipa Malafaya: “Analysis of Sustainability Indicators on the Management
Construction Sites CDW in Recife, Brazil” Electronic Journal of Geotechnical Engineering,
2015 (20.26): 12791-12800. Available at ejge.com.
25. Patricia Lopes Rycheta Arten, André Nagalli: “The Disposal of Personal Protective
Equipment Used in the Heavy Construction Sector” Electronic Journal of Geotechnical
Engineering, 2013 (18.H): 1511-1519. Available at ejge.com.
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