Uporaba spektroskopije gama za identifikacijo virov sevanja na reaktorju TRIGA Mark II

Marinko, Jernej (author), Snoj, Luka (mentor), Jazbec, Anže (comentor)

Spektroskopija gama je občutljiva in selektivna analizna metoda, ki omogoča merjenje energije in števila žarkov gama. Primerna je za identifikacijo in kvantifikacijo radioaktivnih izotopov v vzorcu, saj je priprava vzorcev preprosta. Uporablja se v raziskavah jedrskih reakcij, zagotavljanju varnosti jedrskih objektov, varovanju okolja in upravljanju radioaktivnih odpadkov. Metoda je hitra in nedestruktivna, vendar zahteva natančno umeritev detektorja in ustrezno programsko opremo. Prav tako interpretacija rezultatov zahteva razumevanje jedrskega razpada in delovanja detektorja. V diplomski nalogi smo s pomočjo spektroskopije gama analizirali vzorec elektronskih komponent ter določili njegovo aktivnost po obsevanju v jedrskem reaktorju in hkrati identificirali ali je izmerjena aktivnost nad mejo izvzetja. Ugotovili smo, da so v vzorcu prisotni elementi kobalt, cink, srebro, svinec in kositer. To smo ugotovili s pomočjo meritev aktivnosti posameznih izotopov (58Co 4,52 × 103 Bq, 60Co 8,47 × 103 Bq, 65Zn 7,76 × 103 Bq, 110mAg 1,39 × 105 Bq, 113Sn 1,95 × 103 Bq, 124Sb 7,64 × 104 Bq). Izmerjena aktivnost elementov je bila pod zakonsko predpisano mejo izvzetja, zato dodatni varnostni ukrepi za rokovanje z vzorcem in prenašanje le-tega niso potrebni. V nadaljevanju smo izmerili aktivnost vode za hlajenje reaktorja in ovrednotili hitrost absorpcijska doza, ki so ji zaradi gibanja v območju reaktorja izpostavljeni delavci. Hitrost absorpcijske doze je znašala 14,7 μSv/h, kar bi za operaterja, ki se vsakodnevno giblje v okolici reaktorja, predstavljalo efektivno dozo, večjo od zakonsko dovoljene v enem letu (20 mSv). Hitrost absorpcijske doze smo izmerili tudi s kvalificiranim detektorjem (Merilnik hitrosti doze Berthold LB 123 s sondo LB1236), kjer smo prišli do nasprotnega zaključka, da je hitrost absorpcijske doze 1,5 μSv/h. To pomeni, da delavec v enem letu ne bi prejel efektivne doze sevanja večje od zakonsko predpisane in sevanje vode ne predstavlja nevarnosti za delavce v okolici jedrskega reaktorja. V sklopu diplomske naloge smo tudi kritično ovrednotili rezultate in identificirali nekaj ključnih dejavnikov, ki vplivajo na analizo spektroskopije gama. Natančnost meritev bi izboljšali z uporabo umerjenega detektorja, katerega lastnosti so bile natančno integrirane v programsko opremo. Poleg tega bi lahko bolj natančno opredelili geometrijo in obliko vzorca elektronskih komponent ter odstranili ali podrobneje opisali absorbente. K napaki rezultata vode za hlajenje reaktorja pa so pomembno prispevali približki vrednosti, ki smo jih uporabili pri izračunu hitrosti absorpcijske doze sevanja. Za izvedbo kakovostne analize s spektroskopijo gama se moramo zavedati številnih dejavnikov, ki vplivajo na meritev, in njihovega vpliva na končni rezultat.

• Language: Slovenian
• Keywords: spektroskopija gama, sevanje gama, germanijev detektor, spekter gama, radioaktivnost
• Work type: Final paper
• Typology: 2.11 - Undergraduate Thesis
• Organization: FMF - Faculty of Mathematics and Physics
• Year: 2025
• PID: 20.500.12556/RUL-174314
• COBISS.SI-ID: 251670787
• Publication date in RUL: 01.10.2025

Secondary language

• Language: English
• Title: Gamma spectroscopy for determination of radioactive sources in TRIGA Mark II reactor

Abstract

Gamma spectroscopy is a sensitive and selective analysis method for measuring the energy and number of gamma rays. It is used for the identification and quantification of radioactive isotopes in a sample, as the sample preparation is simple. It is used in nuclear reaction research, nuclear facility safety assurance, environmental protection and radioactive waste management. The method is fast and non-destructive, but requires accurate calibration of the detector and appropriate software. Interpretation of the results also requires an understanding of nuclear decay and detector function and behaviour. In this thesis, an electronic components sample was analysed using gamma spectroscopy and its activity was determined after irradiation in a nuclear reactor. The sample activity was also compared to the regulatory limit for radioactive materials. The presence of cobalt, zinc, silver, lead and tin was detected based on the measured activity of isotopes (58Co 4,52 × 103 Bq, 60Co 8,47 × 103 Bq, 65Zn 7,76 × 103 Bq, 110mAg 1,39 × 105 Bq, 113Sn 1,95 × 103 Bq, 124Sb 7,64 × 104 Bq). The measured activity of the elements was below the regulatory limit and no additional precautions were needed for the transport and handling of the sample. In addition, we measured the activity of the reactor cooling water to determine whether it poses a risk for workers around the reactor. With the gamma spectrometry we measured 14.7 μSv/h dose rate, which would exceed the legal exposure limit for the workers in one year (20 mSv). The dose rate was also measured with a qualified detector (Berthold LB 123 with tip LB1236), which has shown a different value of 1.5 μSv/h. Therefore, in a year equivalent dose would not exceed the legal exposure limit and the cooling water does not pose a risk to the nuclear reactor operators. In this thesis, we critically evaluated the results and identified key factors influencing the analysis with gamma spectroscopy. The accuracy of the measurements could be improved by using a calibrated detector, the characteristics of which have been precisely integrated into the software. The geometry and shape of the electronic components sample could be more accurately characterised, and the absorbers removed or described in more detail. In addition, the approximations of values contributed to the error of the calculated dose rate of the cooling water. To preform quality analysis using gamma spectroscopy one must be aware of the many factors that affect the measurement and their impact on the final result.

• Keywords: gamma spectroscopy, gamma radiation, germanium detector, gamma spectrum, radioactivity