A study on natural radioactivity in Khewra Salt Mines, Pakistan.

COMSATS Institute of Information Technology (CIIT), Department of Physics, Islamabad, Pakistan.
Journal of Radiation Research (Impact Factor: 1.45). 01/2012; 53(3):411-21.
Source: PubMed

ABSTRACT The Khewra Salt Mines, the second largest salt mines in the world, are located 160 km south of Islamabad, the capital of Pakistan. Around 1000 workers are involved in the removal of salt from these mines. More than 40,000 visitors come annually to see the mines. The visitors and workers are directly exposed to the internal and external radiological hazards of radon and gamma rays in these mines. The general public is affected by the intake of the salt containing the naturally occurring radionuclides. Therefore the concentration of radon (²²²Rn) in the Khewra Salt Mines and activity concentrations of the naturally occurring radionuclides in the salt samples from these mines were measured. Both active and passive techniques were employed for the measurement of radon with Radon Alpha Detector (RAD-7) and SSNTD respectively. The concentration of ²²²Rn was 26 ± 4 Bq m⁻³ measured by the active method while 43 ± 8 Bq m⁻³ was measured by the passive method. The activity concentration of the radionuclides was measured using gamma ray spectrometry with HPGe detector. The mean activity of ⁴⁰K in salt samples was found to be 36 ± 20 Bq kg⁻¹ and the concentration of ²²⁶Ra and ²³²Th in the salt samples was below the detection limits. Gamma radiation hazard was assessed in terms of the external gamma dose from salt slabs and the rooms made of salt and the annual effective dose due to gamma radiation. The exposure to radon daughters, annual effective dose and excessive lifetime cancer risk due to radon in the mines were estimated. The mean annual effective dose due to an intake of ⁴⁰K from the salt was calculated as 20.0 ± 11.1 µSv, which is lower than the average annual effective dose rate of 0.29 mSv, received by the ingestion of natural radionuclides. Due to the low concentration values of primordial radionuclides in the salt and radon ²²²Rn) in the mines, a 'low level activity measurement laboratory' is suggested to be established in these mines.

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    ABSTRACT: The state of Azad Kashmir is rich in three types of rocks, namely, sedimentary, metamorphic, and igneous rocks. These rocks contain extensive deposits of graphite, marble, limestone, quartzite, granite, dolerite, and sandstone, which are widely used for the construction of dwellings in Azad Kashmir and Pakistan. Therefore, knowledge about the presence of natural radioactivity in these materials is desirable to assess the radiological hazards associated with it. In this context, 30 rock samples were collected from different geologic formations of the Muzaffarabad Division, Azad Kashmir. After processing the samples, the specific activities of 226Ra, 232Th, and 40 K in them were measured using a P-type coaxial high-purity germanium detector. The observed highest dose rate values for sedimentary, metamorphic, and igneous rocks have been found to be 83.16 ± 1.08, 135.87 ± 1.18, and 115.98 ± 1 nGy ⋅ h–1, respectively. The radium equivalent activity (Raeq) varied from 23.76 ± 1.15 for dolerite sample (igneous rock) to 293.69 ± 2.60 Bq ⋅ kg–1 for marble (metamorphic rock). The Raeq values of all rock samples are lower than the limit mentioned in the Organization for Economic Cooperation and Development (OECD, 1979) report (370 Bq ⋅ kg–1, equivalent to γ-dose of 1.5 mSv ⋅ y–1). The values of external (Hex) and internal hazard indices (Hin) are less than unity. The mean outdoor and indoor annual effective dose equivalents are 0.073 mSv ⋅ y–1 and 0.29 mSv ⋅ y–1, respectively. The mean (over all types of rock samples) annual effective dose equivalent is reported as 0.36 mSv ⋅ y–1.
    Russian Geology and Geophysics 09/2014; 55(9):1103–1112. · 1.41 Impact Factor


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