Sains Ma1aysiana 25(4) 1996: 93-104                                                              Sains Fizis dan Gunaan/

Physical and Applied Sciences

Penentuan Isotop Uranium dan Torium dalam Monazit,

Xenotim dan Zirkon Menggunakan Spektrometri Alfa

(Determination of uranium and thorium isotopes in monazite,

xenotime and zircon using alpha spectrometry)

Amran B. Ab. Majid, Mohd Zahari Abdullah

Jabatan Sains Nuklear

Universiti Kebangsaan Malaysia

43600 UKM Bangi Se1angor D.E. Malaysia

Zaharudin Ahmad

Institut Penyelidikan Tekno1ogi Nuklear Malaysia

ABSTRAK

Kaedah penguraian, pemelarutan, pemendakan bersama, ekstraksi pelarut dan pemendapan elektrik telah dikaji dan digunakan untuk mendapatkan suatu teknik yang terbaik dalam penentuan isotop uranium ²³⁴U, ²³⁵U & ²³⁸U) dan torium ²²⁸Th, ²³⁰Th & ²³²Th) menggunakan sistem spektrometri alfa. Kepekatan isotop U dan Th dalam bahan rujukan piawai River Sediment dan Rocky Flats Soil (NBS) telah dianalisis untuk menentukan kejituan teknik yang dibangunkan. Kajian ini mendapati kepekatan isotop yang diperolehi adalah menghampiri nilai teraku (sijil) dan peratus perolehan semula pembawa yang besar (70-90%). Ini menunjukkan teknik yang dibangunkan sesuai digunakan untuk penentuan isotop uranium dan torium. Seterusnya teknik yang dibangunkan telah digunakan untuk menentukan kandungan uranium dan torium dalam sampel monazit, xenotim dan zirkon tempatan. Kepekatan jumlah isotop uranium yang diperolehi didapati berada dalam julat 21.03 - 171.25 Bq/g manakala kepekatan jumlah isotop torium pula terletak antara 27.48 - 242.87 Bq/g.

ABSTRACT

The determination technique for U (²³⁸U, ²³⁵U, ²³⁴U) and Th (²³²Th, ²³⁰Th, ^228Th)   isotopes using alpha spectrometry was developed. The developed technique involved digestion, dissolution, coprecipitation, solvent extraction and electrodeposition methods. The NBS River Sediment and Rocky Flats Soil Standard Reference Materials were analysed to determine the accuracy of the technique. A good accuracy and high percentage recovery of the carrier (70 - 90%) indicated that the developed technique was suitable for U and Th isotopes determination. The technique was used to determine the U and Th concentration in monazite, xenotime and zircon samples. The results showed that the U and Th total concentrations were in the range of 21.03 to 171.25 Bq/g and 27.48 to 242.87 Bq/g respectively.

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