Evaluation of Bubble Formation and Break Up in Suppression Pools by Using Pattern Recognition Methods
Hujala, Elina (2013)
Diplomityö
2013
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi-fe201304082709
https://urn.fi/URN:NBN:fi-fe201304082709
Tiivistelmä
During a possible loss of coolant accident in BWRs, a large amount of steam will
be released from the reactor pressure vessel to the suppression pool. Steam will
be condensed into the suppression pool causing dynamic and structural loads to
the pool.
The formation and break up of bubbles can be measured by visual observation
using a suitable pattern recognition algorithm. The aim of this study was to
improve the preliminary pattern recognition algorithm, developed by Vesa Tanskanen
in his doctoral dissertation, by using MATLAB. Video material from the
PPOOLEX test facility, recorded during thermal stratification and mixing experiments,
was used as a reference in the development of the algorithm.
The developed algorithm consists of two parts: the pattern recognition of the
bubbles and the analysis of recognized bubble images. The bubble recognition
works well, but some errors will appear due to the complex structure of the
pool. The results of the image analysis were reasonable. The volume and the
surface area of the bubbles were not evaluated. Chugging frequencies calculated
by using FFT fitted well into the results of oscillation frequencies measured in
the experiments.
The pattern recognition algorithm works in the conditions it is designed for. If
the measurement configuration will be changed, some modifications have to be
done. Numerous improvements are proposed for the future 3D equipment. Mahdollisen jäähdytteenmenetysonnettomuuden aikana suuri määrä höyryä vapautuu reaktorin paineastiasta lauhdutusaltaaseen. Höyry tiivistyy lauhdutusaltaassa aiheuttaen dynaamisia ja rakenteellisia kuormituksia altaaseen. Kuplien muodostumista ja luhistumista voidaan mitata visuaalisin havainnoin sopivan hahmontunnistusalgoritmin avulla. Tämän työn tarkoituksena oli parantaa Vesa Tanskasen väitöskirjassaan kehittämää hahmontunnistusalgoritmia MATLAB:lla. PPOOLEX-laitteistolla mitattua lämmön kerrostumis- ja sekoittumiskokeissa kuvattuja videoita käytettiin referenssinä algoritmia kehitettäessä. Algoritmi koostuu kahdesta osasta: kuplien hahmontunnistuksesta sekä tunnistettujen kuplakuvien analysoinnista. Kuplien tunnistus toimii hyvin, mutta laitteiston monimutkaisesta rakenteesta johtuen joitakin virheitä esiintyy. Kuvien analysoinnin tulokset ovat järkeviä. Kuplien tilavuutta tai pinta-alaa ei määritetty. Chugging-taajuudet, jotka laskettiin käyttäen FFT:tä, sopivat hyvin kokeissa mitattuihin oskillointitaajuuksiin. Algoritmi toimii olosuhteissa, joihin se on suunniteltu. Jos mittauslaitteistossa muutetaan jotain, muutoksia täytyy tehdä myös algoritmiin. Työssä ehdotetaan myös lukuisia parannuksia tulevaan 3D-laitteistoon.
be released from the reactor pressure vessel to the suppression pool. Steam will
be condensed into the suppression pool causing dynamic and structural loads to
the pool.
The formation and break up of bubbles can be measured by visual observation
using a suitable pattern recognition algorithm. The aim of this study was to
improve the preliminary pattern recognition algorithm, developed by Vesa Tanskanen
in his doctoral dissertation, by using MATLAB. Video material from the
PPOOLEX test facility, recorded during thermal stratification and mixing experiments,
was used as a reference in the development of the algorithm.
The developed algorithm consists of two parts: the pattern recognition of the
bubbles and the analysis of recognized bubble images. The bubble recognition
works well, but some errors will appear due to the complex structure of the
pool. The results of the image analysis were reasonable. The volume and the
surface area of the bubbles were not evaluated. Chugging frequencies calculated
by using FFT fitted well into the results of oscillation frequencies measured in
the experiments.
The pattern recognition algorithm works in the conditions it is designed for. If
the measurement configuration will be changed, some modifications have to be
done. Numerous improvements are proposed for the future 3D equipment.