doctoral thesis
Anže Jazbec (Author), Luka Snoj (Mentor)

Abstract

This thesis describes the development of a stochastic method to calculate gamma and neutron dose rates for the JSI TRIGA reactor, which can be applied to normal and emergency operations. Knowing the dose rates during normal operation is essential to keep workers safe and in the design of appropriate shielding for new experiments while knowing the dose rates during a postulated accident scenario is necessary for developing an emergency response plan. A completely new MCNP model was designed containing the reactor core and the surrounding components within the concrete shield. Furthermore, the reactor platform, reactor hall, reactor basement and the control room were included in order to calculate the gamma and neutron dose fields within the radiation controlled area. Neutrons and prompt gamma rays were validated in the case where a beam tube was left open, and the reactor was at low power. In this way, neutron and gamma dose rate measurements could be taken around the beam port. The delayed gamma source was validated in the case where one of the irradiated fuel elements was placed in a transport cask, and the surrounding dose rates measured. The good agreement between the calculated and measured results meant the model could be used to predict dose rates during normal operation with newly designed shielding for the beam tube no. 5. Before the shield was constructed, its performance was evaluated by the methodology developed in this thesis. Furthermore, an accident scenario involving the loss of water (LOWE) in the reactor pool and the spent fuel pool were analysed using the same methodology. The LOWE scenario is one of several design-based accidents scenarios to be considered when operating the JSI TRIGA reactor, that was analysed for the first time by the same method. The LOWE for the reactor pool was previously analysed using deterministic methods. Provided results will be used for the next revision of the Safety Analysis Report of the JSI TRIGA Mark II research reactor.

Keywords

nuclear reactors;TRIGA reactor;model MCNP;dose rate field;loss of water event;LOWE;

Data

Language: English
Year of publishing:
Typology: 2.08 - Doctoral Dissertation
Organization: UL FMF - Faculty of Mathematics and Physics
Publisher: [A. Jazbec]
UDC: 621.039.5(043.3)
COBISS: 49249795 Link will open in a new window
Views: 367
Downloads: 79
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Other data

Secondary language: Slovenian
Secondary title: Izračun nevtronskega in gama doznega polja znotraj reaktorske hale reaktorja TRIGA Mark II na IJS
Secondary abstract: V tej disertaciji je opisano, kako lahko stohastične metode uporabimo za računanje doznega polja v okolici reaktorja TRIGA. Simuliramo lahko tako normalno obratovanje reaktorja kot tudi nezgodne dogodke. Poznavanje doz je ključno za zagotavljanje varnega delovnega mesta operaterjem in raziskovalcem. Ocena doznih polj za nezgodne primere je pomembna za ustrezno načrtovanje varnostnih in zaščitnih ukrepov. Sprva je bil narejen popolnoma nov MCNP model reaktorja TRIGA, ki zajema reaktorsko sredico, obdajajoče komponente znotraj betonskega ščita, kar je bilo že modelirano tudi v obstoječem modelu. Poleg tega je bila modelirana tudi reaktorska ploščad, celotna reaktorska hala, reaktorska klet in komandna soba z namenom izračuna nevtronskih in gama doznih polj. Vir nevtronov in takojšnjih gama žarkov je bil validiran na primeru odprtega obsevalnega kanala št. 5. Reaktor je obratoval na nizki moči, med tem pa smo lahko merili dozno polje v okolici kanala. Vir zakasnelih žarkov gama je bil validiran na primeru, ko smo obsevan gorivni element vstavili v transportno posodo, v njeni okolici pa smo pomerili dozno polje. Ker so se izračunani rezultati dobro ujemali z izmerjenimi, smo model uporabili za nadaljnje računanje doznega polja v primeru obratovanja reaktorja na polni moči v okolici novega ščita pri kanalu št. 5. Na podlagi dobrega ščitenja ovrednotenega z metodo razvito v disertaciji, smo ščit tudi namestili. Napravili smo tudi analizo doznega polja v okolici reaktorja za primer nezgode izgube reaktorskega hladila (Loss of water event - LOWE), kjer smo prav tako uporabili enako metodo Takšna analiza je bila v preteklosti že opravljena, vendar le z determinističnimi metodami. Prvič do sedaj smo napravili analizo doznega polja v reaktorski hali za primer nezgode puščanja bazena za izrabljeno hladilo. Rezultati bodo uporabljeni v novi reviziji Varnostnega poročila za raziskovalni reaktor TRIGA Mark II na IJS.
Secondary keywords: jedrski reaktorji;reaktor TRIGA;model MCNP;dozno polje;nezgoda izgube reaktorskega hladila;Triga Mark II (jedrski reaktor);Disertacije;
Type (COBISS): Doctoral dissertation
Study programme: 0
Embargo end date (OpenAIRE): 1970-01-01
Thesis comment: Univ. v Ljubljani, Fak. za matematiko in fiziko, Oddelek za fiziko
Pages: XXI, 134 str.
ID: 12255922