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Title:Analiza kritičnosti v odlagališču za izrabljeno jedrsko gorivo
Authors:ID Čalić, Dušan (Author)
ID Ravnik, Matjaž (Mentor) More about this mentor... New window
Files:.pdf MAG_Calic_Dusan_2009.pdf (2,13 MB)
MD5: 0FDB68D8824B485CF16EA7CF671DE0CA
PID: 20.500.12556/dkum/b806e551-2399-432e-a441-bd8a3c531198
 
Language:Slovenian
Work type:Master's thesis
Organization:FGPA - Faculty of Civil Engineering, Transportation Engineering and Architecture
Abstract:V delu so obravnavani izračuni kritičnosti za model vsebnika z izrabljenim jedrskim gorivom. Vsebnik bodo uporabili za odlaganje visoko aktivnih odpadkov in izrabljenega jedrskega goriva v globokem geološkem odlagališču. Najpomembnejša varnostna funkcija vsebnika je, da bo izoliral gorivo za zelo dolgo časa. To lahko dosežejo le tako, da zadovoljijo varnostnim funkcijam že pred odložitvijo goriva v odlagališče. Model vsebnika v odlagališču smo modelirali na podlagi geometrijskih lastnosti in lastnosti materialov vsebnika in odlagalnih celic, ki temeljijo na Švedskem preliminarnem modelu vsebnika, in lastnosti izrabljenega goriva iz jedrske elektrarne Krško. Gorivni elementi z maksimalno obogatitvijo goriva 4.951% 235U v gorivnih palicah iz cirkonijeve zlitine se vstavijo v vsebnik, obdan z glino, ki se nahaja v matični kamnini. Da zagotovijo varnostnim zahtevam goriva, pomnoževalni faktor ne sme preseči 0.95 pri abnormalnih pogojih, ki lahko nastanejo v vsebniku. Izračuni kritičnosti za normalne in abnormalne pogoje v odlagališču so bili opravljeni z uporabo računalniškega programa MCNP5 in podatkovne knjižnice ENDF/B-VI. Rezultati so pokazali, da tak vsebnik zadošča varnostnim kriterijem v abnormalnih pogojih le ob upoštevanju zgorelosti goriva. Izračuni zgorelosti goriva so bili opravljeni s programom ORIGEN 2.1, kjer smo za vhodne podatke upoštevali povprečno moč in maso urana. Modeliranje sistema z računalniškim orodjem je edina metoda, s katero je mogoče določiti vplive odlagališča na okolje, zato smo rezultate preverili z referenčnimi analizami. Zaradi nepoznavanja vhodnih podatkov, ki imajo velik vpliv na rezultate, so tudi odstopanja relativno velika. Zato smo z analizami poiskali tiste parametre, ki najbolj vplivajo na reaktivnost in lahko služijo kot pomembni indikatorji za prihodnje analize. Kljub večjim razlikam v rezultatih je pomembno, da so vsi zaključki enaki. Kritične razmere v vsebniku lahko nastanejo le v primeru, ko se v vsebniku nahaja sveže gorivo in ko je ves prazen prostor v vsebniku zapolnjen z vodo. Da zagotovimo zahtevam za kritičnost, moramo nujno upoštevati zgorelost goriva. Rezultati kažejo, da je v primeru, da je obogatitev goriva večja od 4% 235U, minimalna zgorelost goriva, ki ga lahko vstavimo v vsebnik, 20 MWd/kgU. Na podlagi rezultatov smo zaključili, da lahko shranimo izrabljeno jedrsko gorivo iz jedrske elektrarne Krško v vsebnike, ki temeljijo na Švedskem modelu le pod določenimi pogoji. Poleg tega pa je pomembno oceniti vse predpostavke, ki smo jih upoštevali pri izračunih, saj so nekatere zelo konzervativne.
Keywords:kritičnost, visoko radioaktivni odpadki, zgorelo gorivo, odlagališče, Monte Carlo
Place of publishing:Maribor
Publisher:D. Čalić]
Year of publishing:2009
PID:20.500.12556/DKUM-11103 New window
UDC:621.039
COBISS.SI-ID:13400342 New window
NUK URN:URN:SI:UM:DK:ZPHQUJUJ
Publication date in DKUM:23.09.2014
Views:1854
Downloads:128
Metadata:XML DC-XML DC-RDF
Categories:KTFMB - FG
:
ČALIĆ, Dušan, 2009, Analiza kritičnosti v odlagališču za izrabljeno jedrsko gorivo [online]. Master’s thesis. Maribor : D. Čalić. [Accessed 31 March 2025]. Retrieved from: https://dk.um.si/IzpisGradiva.php?lang=eng&id=11103
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Secondary language

Language:English
Title:Criticality calculations in deep geological repository
Abstract:Criticality calculations have been performed for a spent fuel disposal canister model. Disposal canister is being used for disposing a high level waste and spent nuclear fuel in a deep geological repository. The primary safety function of the canister is to isolate the spent nuclear fuel within the canister for very long time. This can be ensured only by fulfilling the safety functions prior to the disposal. Criticality calculations of the canister are just one of them. A model with geometric and material properties of the disposal canister and disposal holes based on the Swedish preliminary disposal concept was made, however spent fuel characteristics were adopted from the spent fuel from NPP Krško. Fuel element with the maximum fuel enrichment of 4.951% 235U in the zirconium alloy fuel rod is just one part of their multibarrier repository concept, known as KBS-3 were the fuel is placed in the canister, surrounded by a bentonite clay and deposited in a saturated crystalline host rock. To assure safe disposal conditions of the fuel, one of the requirements is that the multiplication factor must not exceed 0.95 in the most conservative conditions in such a canister. Criticality calculations were performed for normal and abnormal repository conditions using computer code MCNP5, coupled with a cross section data library based mainly on the ENDF/B-VI. The results showed that this type of the preliminary disposal canister meets the safety criteria in most abnormal conditions only if the discharge burnup of the fuel is taken into account. Burnup calculations were performed using ORIGEN 2.1, where the average power and the mass of uranium were considered. Since the modeling with the computer code is the only option for verifying these kinds of calculations the results, based on the reference analyses were verified. There is some discrepancy among the results but this is mainly due to the unknown inputs which can influence the results. The important parameters that may have the biggest influence on the reactivity were pointed out and they can serve as important indicators for future analyses. However the conclusions from the three reports are the same. Critical conditions may arise only in the case where the canister is filled with fresh fuel and the void positions are filled with water. To assure criticality requirements it is necessary to consider the burnup of the fuel. The results indicate that the minimum allowable discharge burnup is about 20 MWd/kgU if the initial enrichment is above 4% 235U. Based on calculations it can be concluded that the spent nuclear fuel from NPP Krško can be stored in the canisters based on the Sweden model however under some conditions. However it is important to review all assumptions used in this work since some of them may be very conservative.
Keywords:criticality, high level waste, spent fuel, repository, Monte Carlo


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