Modeliranje brzine doza komponenata primarnog kruga tlakovodnog reaktora primjenom hibridne determinističko-stohastičke metodologije

doctoral thesis

• Title (english): Dose rates modelling of pressurized water reactor primary loop components by hybrid deterministic- stochastic methodology
• Author: Mario Matijević
• Mentor: Dubravko Pevec (mentor)
• Committee member: Dubravko Pevec (predsjednik povjerenstva)
• Granter: University of Zagreb; Faculty of Electrical Engineering and Computing; (Department of Applied Physics); Zagreb
• Defense date and country: 2013-05-28, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Electrical Engineering
• Universal decimal classification (UDC): 621.3 - Electrical engineering

Abstract

U disertaciji je razvijen 3D simulacijski model primarnog kruga tlakovodnog reaktora PWR tipa (Pressurized Water Reactor) za efikasan proračun brzina doza koji se temelji na hibridnoj determinističko-stohastičkoj metodologiji. Provedena je analiza kritičnosti i proračun štita reaktora, primarnog kruga i zaštitne zgrade korištenjem CSAS6 i MAVRIC sekvence SCALE6.0 programskog paketa. Razvijen je detaljan model kombinatorne geometrije, materijala i karakteristika PWR postrojenja na temelju najboljih dostupnih podataka. Izvori ionizirajućeg zračenja komponenti primarnog kruga su uključili neutrone i fotone iz kritične jezgre reaktora te fotone od aktivacije primarnog hladioca kroz dvije rashladne petlje. Provedena je verifikacija razvijenog modela tehnikom plavljenja (flooding) te njegova parcijalna validacija usporedbom brzina nuklearnih reakcija s referentnim rezultatima H.B.Robinson-2 testnog primjera. Promotrena je mogućnost boriranja biološkog štita reaktora s prirodnim borom i borovim karbidom (B4C) u svrhu smanjenja emisije sekundarnog gama zračenja nastalog procesom radijativnog uhvata termaliziranih neutrona. Utvrđena je potrebna količina prirodnog bora koja dovodi do zasićenja u atenuacijskoj moći boriranog betona za smanjenje tokova čestica i doza. Analizirana je raspodjela i atenuacija brzina doza kroz elemente primarnog kruga unutar velikih struktura zaštitne zgrade fleksibilnim opisom adjungiranog izvora. Istražena je korisnost u definiciji materijalnih značajki adjungiranog izvora, kada se transport čestica dodatno usmjeruje u regije s materijalima od interesa. Kvantificirana je prednost FW-CADIS metodologije u odnosu na CADIS metodologiju i manualne tehnike redukcije varijance u MAVRIC sekvenci. Dane su preporuke za optimizaciju kontrolnih i numeričkih parametara MAVRIC sekvence u hibridnoj FW-CADIS metodologiji u svrhu efikasnog Monte Carlo modeliranja kompleksnog modela. Znanstveni doprinosi su: (1) razvijena je simulacijska procedura za određivanje brzine doza komponenti primarnog kruga reaktora bazirana na hibridnoj determinističko-stohastičkoj metodi; (2) određena je potrebna količina prirodnog bora biološkog štita reaktora za smanjenje sekundarne gama emisije; (3) optimizacija kontrolnih i numeričkih parametara hibridne metode za efikasan Monte Carlo proračun brzine doza unutar velikih struktura; (4) kvantifikacija prednosti FW-CADIS metode u odnosu na CADIS i manualne tehnike za redukciju varijance unutar MAVRIC sekvence.

Abstract (english)

A 3D simulation model of pressurized water reactor (PWR) primary loop components for effective dose rates calculation based on hybrid deterministic-stochastic methodology was developed in proposed dissertation. Criticality and shielding calculations were performed using CSAS6 and MAVRIC sequences of SCALE6.0 code package. A detailed model of a combinatorial geometry, materials and characteristics of a PWR facility was based on best available input data. The sources of ionizing radiation in PWR primary loop components included neutrons and photons originating from critical core and photons from activated coolant in two primary loops. Validation and partial verification of proposed model were performed with flooding technique and with comparison of reaction rates to referenced H.B.Robinson-2 benchmark results. The reduction of secondary gamma emissions from radiative capture of thermalized neutrons in biological shield was examined via concrete boration with natural boron and boron carbide (B4C). Optimal boron concentration which leads to saturation of flux and dose rates attenuation was proposed. Distribution and attenuation of dose rates through large structures of containment building were analysed by flexible definition of adjoint source. The benefits of adjoint source definition with focus on material characteristics of a model was examined. Advantage of using FW-CADIS methodology over CADIS and manual variance reduction techniques inside MAVRIC shielding sequence has been quantified. Recommendations for optimal control and numerical parameters of a MAVRIC sequence with hybrid FW-CADIS methodology were given for effective Monte Carlo deep penetration shielding calculation. Scientific contributions are: (1) simulation procedure was developed to determine primary loop components dose rates based on a hybrid deterministic-stochastic method; (2) the required amount of natural boron was determined for reducing secondary gamma emissions inside biological shied; (3) control and numerical parameters of a MAVRIC sequence with hybrid methodology were optimized for effective Monte Carlo deep penetration shielding calculation; (4) advantage of using FW-CADIS methodology over CADIS and manual variance reduction techniques inside MAVRIC shielding sequence was quantified.

• Keywords: tlakovodni reaktor; primarni krug; zaštitna zgrada; bor; proračun štita; Monte Carlo metoda; deterministička metoda; brzine doza; MAVRIC; SCALE6.0
• Keywords (english): pressurized water reactor (PWR); primary loop; containment; shielding calculations; Monte Carlo method; deterministic method; dose rates; MAVRIC; SCALE6.0
• Language: croatian
• URN:NBN: urn:nbn:hr:168:432189
• Project: Number: 036-0361590-1579; Title: Gospodarenje gorivom standardnih i naprednih nuklearnih reaktora; Leader: Dubravko Pevec; Jurisdiction: Croatia; Funder: MZOS; Funding stream: ZP
• Study programme: Title: Doctoral study programme "Electrical Engineering and Computing"; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti, po-dručje tehničkih znanosti (doktor/doktorica znanosti, po-dručje tehničkih znanosti)
• Catalog URL: http://lib.fer.hr/cgi-bin/koha/opac-detail.pl?biblionumber=41287
• Type of resource: Text
• Extent: 195 str ; 30 cm
• File origin: Born digital
• Access conditions: Closed access
• Created on: 2019-11-27 13:02:28