determination of uranium concentration in jordanian oil shale using fission fragments techniques...

Determination of uranium concentration in Jordanian oil

shale using fission fragments techniques with CR-39 Khalid M. Abumurad

Department of Physics, Yarmouk University

P. O. Box 566, 21163 Irbid, Jordan

Department of Physics, Yarmouk University, Irbid 21163, JORDAN

24th International Conference on Nuclear Tracks in Solids, 1 – 5 Sept. 2008, Bologna, Italy

Determination of uranium concentration in Jordanian oil shale using fission fragments techniques with CR-39

Objective:

Concentration of uranium in oil shale in Jordan never studied before . This study will investigate:• uranium content of Jordanian oil shale using thermal neutrons and fission fragments etch pits recorded on CR-39 detectors.• Other natural activity from Th-series and K.




Introdution• Uranium is ubiquitous on the Earth. It is a metal

approximately as common as tin or zinc, and it is a constituent of most rocks and even of the sea. Some typical concentrations are: (ppm = parts per million).

• Very high-grade ore (Canada) - 20% U, 200,000 ppm• High-grade ore - 2% U,20,000 ppm• Low-grade ore - 0.1% U,1,000 ppm• Very low-grade ore* (Namibia) - 0.01% U100 ppm• Granite: 4-5 ppm• Sedimentary rock: 2 ppm• Earth's continental crust (av): 2.8 ppm• Seawater: 0.003 ppm


Oil shale is a fine-grained sedimentary rock, contains significant amounts of kerogen (a solid mixture of organic chemical compounds), from which technology can extract liquid hydrocarbons.



http://www.powerset.com/explore/semhtml/Sedimentary_rock

http://www.powerset.com/explore/semhtml/Kerogen

http://www.powerset.com/explore/semhtml/Chemical_compound

http://www.powerset.com/explore/semhtml/Hydrocarbon


• Oil shale is available in Jordan in large quantities with high proportion of minerals.• The estimated national reserve of oil shale is approximately 50 billion tonnes [1]. Russell, P. L. Oil shale’s of the world; their origin, occurrence and exploitation. – Oxford: Pergamon Press; 1990.

• Jordanian shales are generally of quite good quality, with relatively low ash and moisture content. Gross calorific value (7.5 MJ/kg) and oil yield (8-12%) are on a par with those of western Colorado (USA) shale; however, Jordanian shale has exceptionally high sulphur content (up to 9% by weight of the organic content). The reserves are exploitable by opencast

mining and are easily accessible.




Location:

There are more than 23 known surface and near surface deposits, eight of which namely,

El-Lajjun,

Sultani,

Jurf Ed-Darawish

, Attarat Um El-Ghudran,

Wadi Maghar,

Siwaga,

Khan El-Zabib

and El-Thamad

were investigated by NRA (Natural Resources Authority-Jordan)

at different levels. The major deposits of commercial scale interest are located south of Amman in central Jordan and are easily

accessible from the desert highway between Amman and Aqaba. See Map




Experimental procedure:Oil shale samples were collected from eight locations (El-Lajjun, Sultani, Jurf Ed-Darawish, Attarat Um El-Ghudran, Wadi Maghar, Siwaga, Khan El-Zabib and El-Thamad). These samples were powdered to fine paricles (~ 128 µm). One gram was taken from each studied and standard (from IAEA) samples and each was mixed with small quantities of pure starch as a binder.The mixture was compressed in the form of pellets with 2cm diameter and 2mm thickness. The pellets were sandwiched between two pieces (1.5x1.5cm2) of CR-39 detectors. The sandwiched pellets were irradiated by thermal neutrons from Am-Be neutron source of flux 4.62x105 n/cm2.s for 20 days. The irradiated detectors were chemically etched with 6.25N NaOH solution at 70oC for 8 h. The etched detectors were washed, cleaned, dried and then counted under an optical microscope.




Results and Discussion:The relation between track density in CR-39 detectors and uranium concentration in the standard samples is show in the following figure (Fig. 1)

Figure 1. Calibration curve. slope = Ts/Cs = Sensitivity (# of pits/mm2)/ppm.



0

50

100

150

200

250

300

350

400

1 2 3 4 5 6 7 8 9 10

Uranium concentration (ppm), Cs

Tra

ck

de

ns

ity

(#

of

pit

s/m

m**

2),

Ts


Uranium concentration, Cx, in the unknown oil shale samples was calculated using the following relation:

Cx = TxCs / Ts= Tx / (Ts/Cs) = Tx / slope.

The following table summarizes the U – concentrations in the oil shale samples collected from different locations:



Location Track Density (#/mm2) U–concentration (ppm) El-Lajjun1167 ± 19831.4 ± 5.3

Sultani457 ± 7312.3 ± 2.5

Jurf Ed-Darawish364 ± 62 9.8 ± 1.5

Attarat Um El-Ghudran620 ± 112 16.7 ± 2.2

Wadi Maghar465 ± 7412.5 ± 1.8

Swaga361 ± 619.7 ± 1.6

Khan El-Zabib1045 ± 15728.1 ± 4.2

El-Thamad1546 ± 21841.6 ± 5.8

Average753 ±11320.3 ± 3.0


0 2 4 6 8 10 12 140

100

200

300

400

500T

rack

den

sity

(#

of p

its/m

m2 )

Uranium concentration (ppm)




Average uranium concentration in rocks of some countries



CountryAv. U – Concentration (ppm)Reference

Turkey6.7 (Yegingil & Goksu, 1990)

Iraq5.5(Tawfiq, 1996)

India7.4(Iyer & Chaudhuri, 1997)

Mexico5.9(Gamboa et al, 1984)

Jordan (oil Skale)

20.3This work


Conclusions:• Uranium content of studied oil shale sample is low compared to phosphate U-content.• The byproduct (ash) going to have even lower concentration of uranium because most of the U-compounds are soluble in water.• Other natural radioactivity (from Th-series and K) will be washed away, since all K – compounds and most of Th – compounds are also soluble in water. (Submitted to the J. of Radiat. Meas.).• Ashes from shale oil industry are, radiologically safe to be used in building materials..




Thanks for your attention



determination of uranium concentration in jordanian oil shale using fission fragments techniques...

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