ASSESSING THE ENVIRONMENTAL POLLUTION USING NEUTRON...
Transcript of ASSESSING THE ENVIRONMENTAL POLLUTION USING NEUTRON...
ASSESSING THE ENVIRONMENTAL POLLUTION USING
NEUTRON ACTIVATION ANALYSIS – K0 METHOD
ON MOSSES
Adrian Florinel BUCSA
Institute for Nuclear Research, Pitesti, ROMANIA
1. INTRODUCTION
• The problem of toxic pollutant agents that exists in environment was and still is a main interest subject for nowadays health protection
issues.
• Evaluating the impact of these agents on human health can influence major decisions that are to be taken by the authorities
concerning the industrial activities developed in the inhabited areas or from the surrounding areas that directly impact the
environment and inferentially the man.
• Precise measurements of toxic particles in the environment at the level of microelements are essential for an efficient assessment of
the pollution degree.
• In order to determine the elements’ concentration in the samples, it was employed as analysis method the Neutron Activation using
k0 standardization (NAA-k0).
• The Neutron Activation Analysis is an analytic technique based on measuring the number and energy of gamma radiation emitted by
the radioactive isotopes produced in the sample matrix by irradiation with neutrons in a nuclear reactor.
• In the urban areas, the air’s quality is strongly influenced by many
human activities. The high population density, the heavy traffic and the
house heating system in winter and various industrial activities influence
the concentration of trace radionuclide elements in the atmosphere.
• Consequently, the population is exposed to potential adverse effects of
changes in the composition of urban air. Thus, monitoring of air quality
has become a standard of quality control procedure in the urban
environment.
• The purpose of this paper is to determine the concentrations of the
chemical elements that affect the human health – toxic agents that are
present in the air and that are retained through fallout in the ground
mosses – a genuine pollution indicator.
• This plant has the ability to retain in the vegetative tissue the chemical
elements precipitated from the atmosphere – (acts as a sponge –, because
the cuticle that would stop the penetration of elements in the cells lacks
totally and they don’t have roots (they present rhizoids that anchor them
to their substrate)
Figure 1. Different types of ground mosses
• Moss samples were picked-up from certain locations (the locations considered with a higher degree regarding environment pollution),
and then these were processed (dried in oven) and finally they were inserted in polypropylene vial and ready to be irradiate in neutron
flux.
• For the experimental part of this research work there have taken a total of 9 samples from different locations of the city of Pitesti. Out
of the total samples we chose to analyze only 4 samples due to the lack of time.
• After collecting the samples, they were stored in polyethylene bags at room temperature for 10 days after which they were weighed
and then placed in an oven at a temperature of 40oC. There were made regular measurements of the masses and then the work
continued with drying them in the oven until the ground moss’s mass became constant.
• This step was made for the following reasons:
- Water vaporization from the vegetative tissue of the mosses;
- To obtain homogeneous and concentrated samples.
2. SAMPLING
Figure 2. Mosses masses evolution from sampling to ready to irradiation state
Table 1. Samples selected for irradiation in TRIGA ACPR
Sample
no. Sampling location
Initial mass 40oC dry
[g] [g]
1* TRIGA Reactor stack 5,887 3,065
2 Rad-waste treatment plant 3,055 2,785
3 Water purification plant 8,378 4,021
4* PITESTI SOUTH Train Station 3,115 2,984
5 TRIVALE Forrest 3,298 2,902
6* ARPECHIM petrochemical
refinery
3,921 1,732
7* ROLAST S.A. rubber factory 5,426 3,136
8 Pitesti Downtown 8,862 3,990
9 GH. DOJA neighborhood 5,573 2,166
Figure 3. Satellite map of Pitesti with sampling location
• For irradiation, we have chosen a quantity approximately equal from the all four samples; these were weighted in polypropylene vials
with small dimensions and then were sealed.
• The samples irradiation was conducted in the TRIGA ACPR reactor in the rabbit (D10 location). The study was conducted on a total of
four samples of ground moss from the environment (rough samples) because of lack of time.
• The samples together with neutron flux monitor (foil of Au-197) were irradiated in TRIGA ACPR reactor’s rabbit for 4142 seconds.
During the entire irradiation period, the presence of the sample in the irradiation location did not disturb the average value of the
thermal neutron flux.
• The calculus made after irradiation showed that the mean value of neutron thermal flux was about 9.47E+11 neutrons / (cm2*sec).
• It should be mentioned that the short irradiation period of time did not allow the activation of heavy metals elements. Hence, in 4142
seconds of irradiation we succeed to activate short life-time isotopes: 55Mn, 41K, 45Sc, 121Sb, 139La, 151Eu, 75As, 81Br, 58Fe.
3. IRRADIATION PREPARATION
• For this experiment it were used the following samples, devices and installations:
ground mosses samples, polypropylene vials, TRIGA ACPR reactor (rabbit) and
detection system consisted of bin and power supply, high resolution germanium γ-ray
detector, amplifier, detector bias supply, pulsating source, multichannel analyzer
(MCA) and personal computer, Figure 4.
• The detection system was delivered with a software specially used for radiation
spectrum analysis (GENIE 2000).
• The high resolution gamma ray detector is shown in the Figure 5.
4. MEASUREMENTS
Figure 5. HPGe Gamma ray detector scheme Figure 4. Block diagram for high resolution gamma ray analysis
HPGe detector main characteristics: 2 calibration curves:
a) Energy calibration curve;
b) Efficiency calibration curve.
These calibration curves were obtain by using 5 certified sources of Am241, Co60, Cs137, Ba133 and Eu152
a) b)
• TRIGA ACPR Research Reactor – It is an annular core pulsed reactor produced by
General Atomics.
• ACPR reactor can operate in pulsed mode of 20.000 MW.
• It has only one central irradiation channel used for fuel rod irradiation and other
structural materials in pulsed mode.
Irradiation facilities
• C6 Capsule (Max temperature 290 C; Pmax: 6 bar) is an irradiation device used for
irradiation tests in transient regime of experimental fuel rods;
• Neutronography installation;
• PGA (Prompt gamma analysis);
• Pneumatic rabbit for NAA;
• Due to modernization process finalized in 2011, TRIGA Reactor’s lifetime has
been extent until 2030.
Figure 6. TRIGA ACPR Research reactor at NRI Pitesti
TRIGA ACPR REACTOR (ANNULAR CORE PULSED REACTOR)
Neutron flux measurements TRIGA ACPR rabbit (D-10) by Au-197 monitor foil irradiation
Irradiation date: 11/8/2016
Start: 11:07:14
Stop: 12:16:16 Tiradiere(sec) 4142
Pter (MW) 63kW
Monitor Au 0,1% Φmonitor 4 mm
M(g) 4.59E-03
σ0 (cm^2) 9.88E-23
Counting no. T(h) (cooling) R (decay/(nucl*s)) Rcd Thermal flux (n/cm^2*s) R (average)
(decay/(nucl*s)) Std dev (n-1) (rate)
Average thermal flux
(n/cm^2*s) Std dev (n-1) (flux)
1 23.55 1.7790E-10 2.10 9.432E+11
1.7862E-10 1.4677E-12 9.470E+11 7.78E+09
2 28.58 1.8020E-10 2.10 9.554E+11
3 53.58 1.7653E-10 2.10 9.359E+11
4 67.66 1.7679E-10 2.10 9.373E+11
5 145.83 1.7930E-10 2.10 9.506E+11
6 151.07 1.8030E-10 2.10 9.559E+11
7 163.7 1.7830E-10 2.10 9.453E+11
8 168.78 1.7960E-10 2.10 9.522E+11
6
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- Reactor’s parameters: f and α ( Høgdahl Convention, well-described)
- Irradiation and measurement aspects: neutron self-absorbtion in sample, dead time,
counting time, coincidence correction, etc.
- Detection efficiency calculated for absorption in sample (according with Moens)
- k0 nuclear data and decay correction scheme (all are available in open literature)
NAA-K0 standardization method
NAA-k0 Analysis results uncertities
Induced by Contribution
k0
Q0
α
f
εp – measurement and conversion
Real coincidence correction
~ 1%
~ 1 %
~ 1,5%
~ 1%
~ 2%
~ 1,5%
Total (quadratic summation ) ~ 3,5%
Elemental concentration
Label
Mn K Br Eu La As Sc Sb Fe
[ppm] ± [%] ± [ppm] ± [ppm] ± [ppm] ± [ppm] ± [ppm] ± [ppm] ± [%] ±
Sample 1 890,17 55,7 2,39 2,04E-03 123,1 3,29 0,76 0,106 24,99 4,57 5,74 0,799 5,87 0,599 5,47 1,1 1,97 4,23E-03
Sample 2 807,75 9,55 1,68 5,41E-04 76,36 5,92 0,61 8,33E-02 25,43 2,29 7,33 1,25 5,29 0,824 7,23 0,773 2,05 7,71E-03
Sample 3 762,5 46,2 1,66 1,09E-03 51,03 9,32 0,65 0,148 22,25 3,05 4,88 0,561 7,78 1,2 1,1 0,318 2,07 3,46E-03
Sample 4 704,5 26,87 1,2 7,00E-04 31,01 4,69 0,82 7,87E-02 25,36 3,01 5,35 0,551 6,09 0,43 3,21 0,358 1,78 1,25E-03
• In K0 standardization method the precision depends on a number of parameters like
Q0, f şi α, measurement geometry and real coincidence effects.
• Uncertities values (for NAA) are:
5. RESULTS
Fe
The discussion related to iron toxicity is limited to
ingestion and exposure through environmental pathway.
Target organs are liver, cardiovascular system and
kidneys.Iron affects usually the myocardium and liver
cells and provokes coma, metabolic acidosis, shock, liver
malfunction, coagulopathy, long term affection of organs
and might cause death too.A dose between 0 mg and 60
mg per each mass kg is considered lethal for human
body.
Eu
There are no clear evidences of toxicity property of
europium comparing to the other heavy metals.
Europium chloride indicates a limit intake value for
intraperitoneal area of 550 mg/kg and 5000 mg/kg for
ingestion. Europium nitride shows a slightly smaller
limit intake value for intraperitoneal area of 320 mg/kg,
while the severe toxicity for ingestion is reached at
around 5000 mg/kg.
Sb
Antimony dust inhalation is very dangerous and in
some cases might be lethal; in small doses level, it
provokes headache, dizziness and depression. In case
of prolonged contact with skin surface in provokes
dermatitis; it also affects kidneys and liver, causing
severe nausea and might lead to death in several days.
As
Arsenic might be found in every source of water from
the globe and involves the exposure of both fish and
shellfish. Other exposure pathways are from dyes,
fungicide and from substances that inhibit the wood
aging. Target organs are blood, kidneys, CNS, digestive
system and skin. The ability of arsenic to involve in
redox conversion between As(III) and As(V) makes him
available and more abundant in environment.
Mg
Manganese compounds are less toxic than any other
spreader metals like nickel and copper. However,
exposure to manganese dust should not exceed the limit
value of 5 mg/m3 even for short periods of time
because of his toxicity. Manganese poisoning was
linked to malfunction of locomotive system of human
body and to some cognitive malfunctions.
Br
Bromism – this state of CNS depression is caused by
the moderate toxicity of bromide in several grams dose
level for humans and other animals. The long half-life
of bromide ions (approximate 12 days) provokes the
poisoning of vital fluids. Bromine ingestion can cause a
skin hives similar to acne.
Sc
Elemental scandium is considered a non-toxic
element. The average lethal dose for scandium
chloride (III) for mice was determined to be 4
mg/kg for intraperitoneal area and 755 mg/kg for
ingestion. Due this, the scandium compounds must
be handled similar to the compounds which shows
moderate toxicity.
K
Because of its strong reactive behavior,
potassium must be carefully handled with skin
and eyes protection. Large potassium quantities
ingestion might lead to hyperkalemia strongly
affecting the cardiovascular system.
La
Lanthanum shows a moderate level of toxicity and
must be handled with care. It produces
hyperglycemia, it implies the decreasing of blood
pressure, spleen degeneration and liver
malfunctions.
NAANAA