MONTE CARLO SIMULATION OF MULTILAYER RADIATION SHIELDING

Ain Syazana Zolkepli; Suffian Mohamad Tajudin; Adila Hanim Aminordin Sabri; Arif Faddilah Mohd Noor; Mohd Zahri Abdul Aziz

Ain Syazana Zolkepli Universiti Sultan Zainal Abidin (UniSZA)
Suffian Mohamad Tajudin Universiti Sultan Zainal Abidin (UniSZA)
Adila Hanim Aminordin Sabri Universiti Sultan Zainal Abidin (UniSZA)
Arif Faddilah Mohd Noor Universiti Sultan Zainal Abidin (UniSZA)
Mohd Zahri Abdul Aziz Universiti Sains Malaysia (USM)

Keywords: toxicity, PHITS simulation, multilayer radiation shielding, x-rays, gamma rays

Abstract

Abstract

Lead (⁸²Pb) is one of the most used materials for attenuating x-rays and gamma rays in high-dose rate radiation facilities. However, it has been proven to have several pitfalls such as the heavy weight, toxicity of lead and its’ high cost. This study was conducted to study the multilayer radiation shielding of non-lead materials to replace lead-based materials by using the Particle and Heavy Ion Transport code (PHITS) simulation. A parallel photon beam of mono-energy source was set in a vacuum environment. Multi-layered shielding composed of ¹³Al, ⁵⁰Sn, ⁵⁶Ba, ⁶⁴Gd, ⁷⁴W and ⁸³Bi was simulated with a total thickness of 6 cm fixed for each multilayer combination. The distance from the point source-multilayer shielding-scoring region was kept constant at 50 cm throughout the series of simulation. The shielding properties of different materials at common energy ranges in radiology and nuclear medicine (100 keV until 1 MeV) were obtained. For each multilayer combination, the materials were encoded with their symbols and density in the PHITS task folder. Next, they were arranged in the desired orientation, either from low to high atomic number (orientation A), or high to low atomic number (orientation B). Among different non lead multilayer shield combinations proposed in this study, the two layered shielding consisting of W/Gd (orientation B) showed the most significant attenuation properties at 1 MeV photon energy. There is no optimal combination that provides equally effective attenuation in all cases as the proposed multilayer shielding materials must be individually tailored to match an application at a particular energy range.

Abstrak

Plumbum (⁸²Pb) ialah salah satu bahan yang paling biasa digunakan untuk melemahkan sinar-x dan sinar gamma dalam kemudahan sinaran kadar dos tinggi. Walau bagaimanapun, ia telah terbukti mempunyai beberapa perangkap seperti berat berat, ketoksikan plumbum dan kosnya yang tinggi. Kajian ini dijalankan untuk mengkaji pelindung sinaran berbilang lapisan bahan bukan plumbum bagi menggantikan bahan berasaskan plumbum dengan menggunakan simulasi kod Pengangkutan Zarah dan Ion Berat (PHITS). Rasuk foton selari sumber tenaga mono ditetapkan dalam persekitaran vakum. Perisai berbilang lapisan yang terdiri daripada ¹³Al, ⁵⁰Sn, ⁵⁶Ba, ⁶⁴Gd, ⁷⁴W dan ⁸³Bi telah disimulasikan dengan jumlah ketebalan 6 cm tetap untuk setiap gabungan berbilang lapisan. Jarak dari kawasan pemarkahan perisai sumber-pelbagai lapisan dikekalkan malar pada 50 cm sepanjang siri simulasi. Sifat perisai bahan yang berbeza pada julat tenaga biasa dalam radiologi dan perubatan nuklear (100 keV hingga 1 MeV) telah diperolehi. Untuk setiap gabungan berbilang lapisan, bahan telah dikodkan dengan simbol dan ketumpatannya dalam folder tugas PHITS. Seterusnya, ia disusun mengikut orientasi yang dikehendaki, sama ada dari nombor atom rendah ke tinggi (orientasi A), atau nombor atom tinggi ke rendah (orientasi B). Di antara kombinasi perisai berbilang lapisan bukan plumbum berbeza yang dicadangkan dalam kajian ini, dua perisai berlapis yang terdiri daripada W/Gd (orientasi B) menunjukkan sifat pengecilan paling ketara pada tenaga foton 1 MeV. Tiada kombinasi optimum yang memberikan pengecilan yang sama berkesan dalam semua kes kerana bahan pelindung berbilang lapisan yang dicadangkan mesti disesuaikan secara individu untuk memadankan aplikasi pada julat tenaga tertentu.