Razvoj metode gama-spektrometrije visoke razlučivosti za primjenu u nuklearnoj forenzici

doctoral thesis

• Title (english): High-resolution gamma spectrometry method development for nuclear forensic applications
• Author: željka Topolovac
• Mentor: Ivana Tucaković (mentor)
• Mentor: Sanda Rončević (komentor)
• Committee member: Mirta Rubčić (predsjednik povjerenstva)
• Committee member: Željka Knežević Medija (član povjerenstva)
• Committee member: Ivan Nemet (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Chemistry); Zagreb
• Defense date and country: 2024-10-10, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Chemistry
• Universal decimal classification (UDC): 54 - Chemistry. Crystallography. Mineralogy

Abstract

Cilj ovog rada bio je prilagoditi metodu gama-spektrometrije visoke razlučivosti za brže i preciznije određivanje aktivnosti iz kompleksnih spektara nuklearnih i drugih radioaktivnih materijala odnosno za primjenu u nuklearnoj forenzici. Istraživani materijali podijeljeni su u pet skupina i analizirani gama- spektrometrijom visoke razlučivosti, a neki uzorci i dodatnim metodama. Analiza materijala s lokacije sanacije radiološkog izvanrednog događaja ukazala je na radioaktivno onečišćenje s 137Cs. Analize radioaktivnog materijala u bačvama ukazale su na prisutnost radionuklida 226Ra, 60Co, 137Cs, 238U, 241Am i 125Sb te je potvrđen je neravnomjeran raspored radionuklida u betonskim matricama unutar bačvi. U epruvetama nepoznatog sastava detektirani su 235U i 238U u prirodnom izotopnom omjeru. Sve primijenjene metode potvrdile su nehomogen sastav u uzorcima praha nepoznatog porijekla. Dva uzorka sadrže radionuklide iz 232Th niza i sličnog su sastava dok je treći uzorak radioaktivniji, sadrži radionuklide iz 238U niza te mineral urofan. U uzorcima praha i nakita iz slučaja Karasovići detektiran je uranij. U dijelu nakita narušen je prirodni izotopni omjer u korist 238U. Prah sadrži uranijem bogate faze – masuyit, uraninit i betafit koje ne potječu iz Hrvatske. Metoda gama-spektrometrije visoke razlučivosti pokazala se kao pouzdana primarna metoda za primjenu u nuklearnoj forenzici, a postupci analize uzoraka prilagođeni su za analizu nuklearnog i drugog radioaktivnog materijala.

Abstract (english)

The aim of this research was to modify the high-resolution gamma spectrometry method for faster and more precise determination of activity from complex spectra of nuclear and other radioactive materials, i.e. for use in nuclear forensics. The researched materials are divided into five groups and analysed by high-resolution gamma-spectrometry, and for some samples using additional methods. The analysis of materials from the location of the remediation of the radiological extraordinary event indicated radioactive contamination with 137Cs. Analysis of radioactive material in the barrels indicated the presence of radionuclides 226Ra, 60Co, 137Cs, 238U, 241Am and 125Sb, and confirmed the uneven distribution of radionuclides in the concrete matrices inside the barrels. In test tubes of unknown composition, 235U and 238U were detected in the natural isotopic ratio. All applied methods confirmed the inhomogeneous composition in powder samples of unknown origin. Two samples contain radionuclides from the 232Th chain and have a similar composition, while the third sample is more radioactive, contains radionuclides from the 238U chain and the mineral urophane. In samples of powder and jewellery from the Karasovići case uranium was detected. In part of the jewellery, the natural isotopic ratio was disturbed in favour of 238U. The powder contains uranium-rich phases masuyite, uraninite and betafite, which do not originate from Croatia. The high-resolution gamma spectrometry method has proven to be a reliable primary method for use in nuclear forensics and sample analysis procedures have been adapted for the analysis of nuclear and other radioactive material.

• Keywords: gama-spektrometrija visoke razlučivosti; nuklearna forenzika; nuklearni materijal; radioaktivni materijal
• Keywords (english): high-resolution gamma spectrometry; nuclear forensics; nuclear material; radioactive material
• Language: croatian
• URN:NBN: urn:nbn:hr:217:374593
• Promotion: 2024
• Study programme: Title: Doctoral study; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica u području prirodnih znanosti (doktor/doktorica u području prirodnih znanosti)
• Type of resource: Text
• Extent: 134, XVIII str. ; 30 cm
• File origin: Born digital
• Access conditions: Open access
• Created on: 2024-10-28 13:58:31