Zasnova in analiza večnamenskega lahkovodnega mikroreaktorja z UZrH gorivom

Paskova, Katerina (author), Trkov, Andrej (mentor), Goričanec, Tanja (comentor)

V magistrskem delu sem analizirala sredico večnamenskega mikroreaktorja. Cilj je bil zasnovati sredico, ki bi bila prilagodljiva in bi jo bilo mogoče z zamenjavo nekaterih gorivnih elementov prilagoditi različnim namenom uporabe. Gorivo UZrH je bilo izbrano zaradi promptnega negativnega temperaturnega koeficienta, saj ima moderator prisoten že v samem gorivu. Analiza je zajemala določitev sprejemljivih parametrov geometrije gorivne palice, gorivnega elementa in sredice, izbiro ugodnih metod kratkoročne kontrole reaktivnosti ter določitev položajev obsevalnih kanalov in njihovih vplivov na nevtronski spekter. Simulacije so bile izvedene s pomočjo odprtokodnega stohastičnega programa za transport nevtronov in fotonov OpenMC. Parametrična študija je pokazala, da je osnovna sredica podmoderirana in da so temperaturni reaktivnostni koeficienti negativni. Za kontrolo reaktivnosti so bile izbrane kontrolne palice, saj zagotavljajo dovolj negativne reaktivnosti za varno zaustavitev reaktorja, hkrati pa so bile tudi prostorsko ugodne. Model OpenMC je bil kasneje sklopljen z internimi programi za termohidravlične izračune. Sredica je bila optimizirana z uporabo različnih obogatitev goriva v gorivnih elementih in z dodajanjem prevlek gorljivih absorberjev na izbrane gorivne palice. Pri tej konfiguraciji so bili konični faktorji moči pod limitnimi vrednostmi, znanimi za delujoče reaktorje. Na podlagi teh obogatitev in razporeditve gorljivih absorberjev so bile simulirane konfiguracije sredice z obsevalnim kanalom ter izračunani konični faktorji moči. Rezultati kažejo, da lahko obravnavani mikroreaktor deluje s parametri znotraj varnostnih omejitev, pri čemer konični faktorji moči predstavljajo netrivialen izziv. Kontrolne palice so bile v nadaljnji analizi razdeljene v banke, kar omogoča boljšo kontrolo reaktivnosti in bolj enakomerno porazdelitev nevtronskega fluksa. Bilo je pokazano, da je z uporabo specifičnih materialov v obsevalnem kanalu mogoče doseči različne nevtronske spektre, kar omogoča prilagoditev obsevalnih pogojev zahtevam posameznih aplikacij ter posledično izboljša učinkovitost aktivacije, karakterizacije materialov in drugih nevtronskih eksperimentov.

• Language: Slovenian
• Keywords: mikroreaktor, SMR, OpenMC, temperaturni profil, večnamenski, sledenje bremenu, obsevalni kanal
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FMF - Faculty of Mathematics and Physics
• Year: 2026
• PID: 20.500.12556/RUL-186228
• COBISS.SI-ID: 289865219
• Publication date in RUL: 28.08.2026

Secondary language

• Language: English
• Title: Design and analysis of a multifunctional lightwater microreactor with UZrH fuel

Abstract

In this master's thesis, I analysed the core of a multifunctional microreactor. The aim was to design a core that would be adaptable and could serve different purposes by swapping some of the fuel assemblies. UZrH fuel was selected because part of the moderator is present directly in the fuel, leading to a prompt temperature feedback effect. The analysis covered determining acceptable parameters for the fuel pin, assembly and core geometry, favourable short-term control methods, as well as irradiation channel positions and neutron spectrum properties. The simulations were performed using the open-source stochastic programme for neutron and photon transport, OpenMC. The parametric study demonstrated that the primary core design is undermoderated and the reactivity feedback coefficients are negative. Control rods were chosen for reactivity control, as they provided sufficient negative reactivity to safely shut down the reactor, while also being spatially convenient. The OpenMC model was later coupled with internal programmes for thermohydraulic calculations. The core was optimised by using different fuel enrichments in the fuel assemblies and by adding burnable absorber coatings to some of the fuel pins. With this configuration, the power peaking factors were calculated to be within the limits known for functioning reactors. Using these enrichments and burnable absorber positions, core configurations with irradiation channels were simulated, and their power peaking factors calculated. The results indicate that the considered microreactor can operate with parameters within the safety limitations, with the power peaking factors being the main non-trivial challenge. In further analysis the control rods were separated into banks for better control and a more even neutron flux distribution. Finally, different neutron spectra can be achieved by using specific materials in the irradiation channel, enabling the irradiation conditions to be tailored to the requirements of specific applications and consequently enhancing the efficiency of neutron activation, materials characterization, and other neutron-based experiments.

• Keywords: microreactor, SMR, OpenMC, temperature profile, multifunctional, load-following, irradiation channel