Utjecaj numeričkog modela postrojenja LOFT na rezultate proračuna eksperimenta LOFT L2-5

undergraduate thesis

• Title (english): Influence of the numerical model of the LOFT facility on the calculation results of LOFT L2-5 experiment
• Author: Ivan Čičak
• Mentor: Siniša Šadek (mentor)
• Committee member: Siniša Šadek (predsjednik povjerenstva)
• Committee member: Paulina Dučkić (član povjerenstva)
• Committee member: Štefica Vlahović (član povjerenstva)
• Granter: University of Zagreb; Faculty of Electrical Engineering and Computing; Zagreb
• Defense date and country: 2021-09-02, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Electrical Engineering

Abstract

Najvažniju stavku nuklearnih elektrana predstavlja njezina sigurnost te nam L2-5 test daje dobar uvid u ponašanja PWR elektrane za vrijeme velike izljevne nesreće. Nodalizacija testa se provodi unutar RELAP5 programa te su sve potrebne termičke i hidrauličke informacije prikupljene za vrijeme stvarnih izljevnih nesreća koje su se provodile s ciljem osmišljanja samog programa RELAP5. Program na osnovu matematičkih operacija te rješavanjem diferencijalnih jednadžbi dolazi do simuliranja stvarnih prilika za vrijeme nuklearnih nesreća. Nakon puknuća hladnog cjevovoda dolazi do velikog snižavanja tlaka unutar primarnog kruga PWR elektrane te gubitak velikog dijela fluida koji bespovratno izlazi iz sustava. Preostali fluid počinje ključati te se zbog gubitka rashladnog sredstva i smanjenog prijenosa topline uzrokovano velikim toplinskim otporom pare temperatura jezgre bitno povisi. Nakon prorade sustava za zaštitno hlađenje dolaze do ponovnog uranjanja jezgre u tekućinu te dolazi do snižavanja temperature jezgre čime sustav ulazi u stabilno stanje. Nodalizacija samog postrojenja unutar RELAP5 programa bila je proizvoljna te smo u ovom radu testirali utjecaj povećavanja kao i smanjivanja broja kontrolnih volumena jezgre te povećavanje kontrolnih volumena tlačnika i parogeneratora ali sa zadržavanjem njihovih originalnih proporcija čime je utvrđeno da nodalizacija nema utjecaja na rezultate pokusa samih komponenta na kojima su izvršene izmjene kao ni na komponente kojima je model ostao isti.

Abstract (english)

The most important aspect of nuclear power plants is its safety, and the L2-5 test gives us a great insight into the behavior of PWR power plants during large break loss of coolant accident. Nodalization of the test is conducted within the RELAP5 program in which all of the necessary thermal and hydraulic information (which were collected during the actual LBLOCA accident) was entered. The program is based on solving differential equations and using basic mathematical operations to simulate real conditions during nuclear accidents. After the rupture of the cold leg, there is a large drop in pressure of the primary loop of PWR nuclear plant, the fluid begins to irrevocably leak. Remaining fluid starts to boil after the loss of primary coolant and large pressure drop, boiling causes heat transfer to slow down and that significantly raises the core temperature. After the initialization of emergency core cooling system core gets reflooded and the temperature significantly decreases, power plant enters its stable state. The nodalization of the model itself was arbitrary and in this paper, we tested the effect of increasing and decreasing the number of control volumes of the core, and increasing control volumes in pressurizer and steam generator while still keeping their original proportions and found that nodalization has no effect on the test result of the exchanged elements of the model same as on the models that remained the same throughout the whole experiment.

• Keywords: RELAP5; LOFT; LBLOCA; PWR; jezgra; tlačnik; parogenerator; nodalizacija; kontrolni volumeni
• Keywords (english): RELAP5; LOFT; LBLOCA; PWR; core; pressurizer; steam generator; nodalization; control volumes
• Language: croatian
• URN:NBN: urn:nbn:hr:168:424115
• Study programme: Title: Electrical Engineering and Information Technology; Study programme type: university; Study level: undergraduate; Academic / professional title: sveučilišni/a prvostupnik/ prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka elektrotehnike i informacijske tehnologije (sveučilišni/a prvostupnik/ prvostupnica (baccalaureus/baccalaurea) inženjer/inženjerka elektrotehnike i informacijske tehnologije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Closed access
• Created on: 2023-01-13 14:45:22