Investigations of Natural Radioactivity Levels in Cement, Cement’s Raw Materials and Some Related Environmental Samples Using Gamma Ray Spectrometer
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Date
2020-02-02
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Addis Ababa University
Abstract
Natural radioactive materials can be originated from various geological materials enriched
with radio elements. Commonly known natural radioactive materials are primordial radionuclides,
238
92 U, 235
92 U, 232
90 Th and 40
19K, which are known for their long half lifetime. Parts
of the earth or earth surface like sedimentary rock, limestone and sandstone, and clay rocks
are the known geological materials in hosting such radioactive materials. The distribution
of radio elements in earth crust depends on geo-chemical conditions of their hosts, weathering,
human actions, and the like factors. Therefore, their distribution in and/or on earth
surfaces is not homogeneous, vary from places to places. Radionuclide hosting materials
can be used for different purposes in different factories as a raw material. Cement factories
are the known consumer of such raw materials in the production of Portland cement. In this
study, the levels of activities and health hazard indices in raw materials and final products
of Portland cement samples were measured at cement factories in west Shoa Oromia regional
state, Ethiopia. Besides, activities and health hazard indices of related environmental
samples, soil, were measured.
The study had been accomplished using high efficiency gamma ray spectrometer with
Digital Signal Analyser, (DSA) coupled with High Purified Germanium detector and high
efficiency gamma ray spectrometer with modular detector electronics, coupled with Thallium
activated Sodium Iodide (NaI(Tl)) detector. The gamma ray spectrometers are controlled
by GENIE2K-high channel number performance, computer software, and out put
results are displayed on coupled personal computer.
The activity levels and corresponding health hazard indices of 238
92 U, 232
90 Th and 40
19K in the
main cement raw materials (Limestone, Sandstone, and Clay rocks), additive raw materials
(Coal, Pumice and Gypsum) and final cement product (Ordinary Portland cement, Pozzolana
Portland cement and semi-processed cement called clinker) samples were measured. As the
main cement raw materials, maximum activities were measured in clay samples, 50:58_
2:42, 150:40_7:41 and 365:00_17:11 Bq=Kg, for 238
92 U, 232
90 Th and 40
19K respectively, where
low activity concentrations were measured in Limestone samples, 7:43_0:35, 1:75_0:29
and 17:02_1:56 Bq=Kg respectively, for 238
92 U, 232
90 Th and 40
19K.
In additive cement raw material samples, maximum activity concentrations were measured
in pumice samples as 78:00_4:00, 107:53_5:49 and 1307:65_60:70 Bq=Kg, for
vi
238
92 U, 232
90 Th and 40
19K radio elements respectively. Low activities were measured in gypsum
samples, 1:56_0:14, 1:79_0:33 and 28_2:0 Bq=Kg, for 238
92 U, 232
90 Th and 40
19K respectively.
In the same way, the final product of cement, Portland cement, got a maximum reading of
31:63_1:46, 45:87_2:30 and 369:71_16:94 Bq=Kg for 238
92 U, 232
90 Th and 40
19K respectively.
The related environmental samples, collected from floriculture industry near Holeta
town, Oromia special zone, gave activity concentration readings for 238
92 U, 232
90 Th and 40
19K, as
197:18_16:88, 8:00_0:29 and 360:40_21:20 respectively.
The elemental concentration values for natural radio elements in above were also calculated
for additive cement raw material and floriculture soil samples. The results have a
direct relation with activity concentrations, maximum activity concentration will give maximum
elemental concentration values. The health hazard indices, Radium equivalent activity
(Raeq), Absorbed dose (DR), Annual dose rate (ADR), External hazard index (Hex) and Internal
hazard index (Hin) were calculated for each studied sample. These parameters have
a direct relation with activity concentrations that maximum activity concentrations will induces
maximum health hazards to the environments.
The measured activity values were compared with other’s work investigations for the
same sample types and world average values given by United Nations Scientific Committee
on the Effects of Atomic Radiation (UNSCEAR-2000). It was found that results from some
samples (Pumice, Coal and Clay) were crossed the values given by the committee, and
others are with in the permissible values given by this committee.
Description
Keywords
Investigations, Natural Radioactivity Levels, Cement, Cement’s Raw Materials, Some Related, Environmental Samples, Using Gamma, Ray Spectrometer