Predviđanje strukturnog integriteta cijevi parogeneratora utemeljeno na ispitivanju vrtložnim strujama

doctoral thesis

• Title (english): Structural Integrity Assessment of Steam Generator Tubes based on Eddy Current Examining
• Author: Zrinka Čorak Cvjetičanin
• Mentor: Vladimir Mikuličić (mentor)
• Committee member: Nikola Čavlina (predsjednik povjerenstva)
• Committee member: Vladimir Mikuličić (član povjerenstva)
• Committee member: Damir Markučič (član povjerenstva)
• Committee member: Nenad Debrecin (član povjerenstva)
• Committee member: Dubravko Pevec (član povjerenstva)
• Granter: University of Zagreb; Faculty of Electrical Engineering and Computing; (Department of Energy and Power Systems); Zagreb
• Defense date and country: 2010-11-26, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Electrical Engineering; Power Engineering
• Universal decimal classification (UDC): 621 - Mechanical engineering. Nuclear technology. Machinery

Abstract

Parogenerator je jedna od najvaţnijih komponenti nuklearnih elektrana, glede funkcionalnosti i sigurnosti. Temeljni zahtjev koji se javlja u radu nuklearnih elektrana, a koji proizilazi iz uvjeta sigurnosti, je oĉuvanje integriteta primarnog kruga, a samim time i parogeneratora. Površina cijevnog snopa parogeneratora predstavlja više od 50% ukupne površine primarnog kruga pod tlakom. Oštećenje cijevnog snopa moţe rezultirati propuštanjem fisijskih produkata u sekundarni krug, a potom preko... More kondenzatora dospjeti u okolinu. Osnovna zadaća svakog vlasnika elektrane je uspostaviti ravnoteţu u poduzimanju preventivnih mjera kao što su praćenje, ispitivanje te korektivne akcije u cilju oĉuvanja integriteta cijevi parogeneratora. Procjena integriteta cijevi parogeneratora predstavlja kljuĉni faktor u ostvarenju navedenog cilja. Zadovoljiti spomenutu zadaću podrazumijeva provoĊenje širokog spektra istraţivanja koje svaki vlasnik elektrane mora provesti:
- Istraţivanje degradacijskih mehanizama koji se javljaju na parogeneratoru
- Istraţivanje raspoloţive tehnologije ispitivanja cijevi parogeneratora, koja moţe zadovoljiti potrebe utvrĊivanja stanja
- Uspostavljanje odgovarajuće metodologije za utvrĊivanje strukturnog integriteta cijevi na poĉetku i na kraju radnog ciklusa
- Kvantifikacija neodreĊenosti koje su povezane s mjerenjem
- Izbor strategije za provoĊenje analize strukturnog integriteta
- Provjera modela za utvrĊivanje strukturnog integriteta cijevi, s podacima s umjetnim i po mogućnosti stvarnim oštećenjima Temeljem navedenih istraţivanja uspostavlja se program ispitivanja kojim se definira opseg ispitivanja, tehnike ispitivanja koje se trebaju primijeniti te razina osposobljenosti osoblja za provedbu ispitivanja. Podaci ispitivanja omogućuju provoĊenje cjelokupnog postupka utvrĊivanja strukturnog integriteta cijevi parogeneratora, kako na poĉetku, tako i na kraju radnog ciklusa. U ovom radu obraĊeni su svi navedeni elementi potrebni za utvrĊivanje strukturnog integriteta cijevi parogeneratora. Prikazani su pojedini utjecajni faktori i naĉini njihovog odreĊivanja. Posebna paţnja posvećena je tehnici ispitivanja te utvrĊivanju neodreĊenosti koje su povezane s ispitivanjima. Provedena su opseţna istraţivanja u cilju utvrĊivanja relacijske ovisnosti, koristeći cijevi s umjetnim (mehaniĉkim) oštećenjima.
Za sluĉaj aksijalnih oštećenja na slobodnoj duljini cijevi provedena su cjelovita laboratorijska istraţivanja. Ona su omogućila uspostavljanje relacijske ovisnosti tlaka pucanja i strukturne varijable, te odreĊivanje svih popratnih neodreĊenosti: relacijska neodreĊenost, neodreĊenost svojstava materijala, neodreĊenost mjerenja te neodreĊenost porasta oštećenja. Svojstva materijala cijevi utvrĊena su za radne uvjete parogeneratora (300 oC), pa je relacijska ovisnost svedena na radne uvjete. Posebno vrijedan doprinos u istraţivanju strukturnog integriteta cijevi uĉinjen je korištenjem cijevi sa stvarnim oštećenjima, iz parogeneratora. Na izvaĊenim su cijevima provedena laboratorijska istraţivanja u svrhu utvrĊivanja neodreĊenosti mjerenja, na naĉin da su sva oštećenja koja su prethodno odreĊena metodom vrtloţnih struja, podvrgnuta razornim ispitivanjima, ĉime su dobiveni neprocjenjivo vrijedni podaci glede neodreĊenosti mjerenja metodom vrtloţnih struja. Jedan broj izvaĊenih cijevi iskorišten je za utvrĊivanje relacijske ovisnosti, pa su podvrgnuti tlaĉnim testovima pucanja za razliĉita oštećenja. U konaĉnosti je za cijevi sa stvarnim oštećenjem utvrĊen strukturni integritet. Sve što je navedeno omogućuje da se na parogeneratorima VVER-tipa uspostavi znanstveni pristup utvrĊivanja strukturnog integriteta cijevi, koristeći suvremene matematiĉke modele. Provedena su cjelovita laboratorijska istraţivanja za pojedine sluĉajeve oštećenja, koja do sada nisu bila izvedena. Za potrebe ovog rada istraţivanja su provedena za cijevi s umjetnim oštećenjima, aksijalno orjentiranim na slobodnoj duţini, te za cijevi sa stvarnim oštećenjima (kombinacija jamiĉaste i naponske korozije). Ovo će omogućiti vlasnicima elektrana novi pristup u utvrĊivanju strukturnog integriteta cijevi parogeneratora, koji omogućuje pouzdanije ispunjavanje sigurnosnih zahtjeva u radu elektrane. Less

Abstract (english)

Steam generator is one of the most important components of nuclear power plants regarding functionality and safety. Crucial requirement in the work of nuclear power plants, and that arises from safety requirements, is the retaining of the integrity of the primary circuit, thus a steam generator as well. The surface of the steam generator tube bundle makes for more than 50% of the overall surface of the primary circuit under pressure. Defects of the tube bundle can lead to fission... More products´ release to the secondary circuit, and then, through the condenser, to the environment. The main task of every nuclear power plant owner is to establish the balance in taking precautions such as monitoring, inspection and corrective actions, with the aim of retaining the steam generator integrity. The steam generator integrity assessment is the key factor in achieving the mentioned aim. Performing the mentioned task implies conducting a wide range of researches that need to be executed by a nuclear power plant owner:
- Research of degradation mechanisms that occur on steam generator
- Research of available technology of steam generator tube inspection that can meet the requirements of as-found condition determination
- Implementation of the appropriate methodology for identifying the structural integrity of tube at the beginning and at the end of the cycle
- Quantification of measurement uncertainties
- Selection of the strategy for conducting the structural integrity analysis
- Verification of the model for identifying the structural integrity of tubes with data of artificial defects and if possible real defects On the basis of the mentioned research, a program of inspection is established, that defines the scope of inspection, inspection techniques that need to be applied, and the qualification level of the staff assigned for performing the inspection. Inspection data enable the execution of the entire procedure of identifying the structural integrity of steam generator tubes at the beginning, as well as at the end of the cycle. This thesis explores all mentioned elements necessary for identifying the steam generator tube structural integrity. Particular impact factors and manners of their identification are presented. Special attention is paid to inspection technique and defining burst pressure relationship, using tubes with artificial (mechanical) flaws.
For the case of axial flaws on the free span, comprehensive laboratory researches have been conducted. They enabled the identification of the burst pressure relationship and identification of all accompanying uncertainties, relational uncertainty, material property uncertainty, measurement, and growth uncertainty. Tube material property uncertainty is identified for working conditions of steam generator (300oC), so burst pressure relationship is reduced to operating conditions. Valuable contribution to research of structural integrity of tubes was made by using tubes with real defect from the steam generator. Laboratory researches on pulled out tubes were conducted, for the purpose of identifying measurement uncertainties, in the manner that all flaws that had previously been identified by the eddy current method underwent destructive examination, which generated highly valuable data regarding nondestructive measurement uncertainty. A certain number of pulled out tubes was used for identifying burst pressure relationship, so they were subject to burst pressure testing for different flaws. Eventually the structural integrity for tubes with real defect was identified. Above mentioned enables a scientific approach of identifying the structural integrity of tubes using contemporary mathematical models to be established on VVER steam generators. Comprehensive laboratory research for particular defects occurrence was conducted, that had not been conducted until now. For the needs of this thesis, researches were conducted on tubes with artificial flaws axially oriented on the free span, as well as on tubes with real defects (combination of pitting and stress corrosion cracking). This will allow owners of nuclear power plants a new approach in defining the structural integrity of steam generators tubes which enables improved reliability and safety in the nuclear power plant operation. Less

• Keywords: procjena strukturnog integriteta; VVER-tip parogeneratora; degradacijski mehanizmi na VVER-tipu parogeneratora; ispitivanja metodom vrtložnih struja; sonde vrtložnih struja; neodređenost mjerenja; neodređenost materijala; porast oštećenja; utvrđivanje strukturnog kapaciteta cijevi na početku ciklusa; utvrđivanje strukturnog kapaciteta cijevi na kraju ciklusa
• Keywords (english): structural integrity assessment; VVER steam generator; degradation mechanisms on VVER steam generator; eddy current examination; eddy current probe; measurement uncertainty; material property uncertainty; growth rate; condition monitoring limit; operational assessment limit.
• Language: croatian
• URN:NBN: urn:nbn:hr:168:650123
• 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=34354
• Type of resource: Text
• Extent: 152 str. ; 30 cm
• File origin: Born digital
• Access conditions: Closed access
• Created on: 2019-03-26 11:08:25