estimation of the radioactive aerosols capture in accidental sequences of nuclear power plants

373 Pages·2017·9.41 MB·English

ESTIMATION OF THE RADIOACTIVE
AEROSOLS CAPTURE IN ACCIDENTAL
SEQUENCES OF NUCLEAR POWER PLANTS

DOCTORAL THESIS

Author:
César Berna Escriche

Supervisors:
Dr. José Luis Muñoz-Cobo González
Dr. Facundo Alberto Escrivá Castells

Valencia, September 2017

E
STIMATION OF THE
R A
ADIOACTIVE EROSOLS
C A
APTURE IN CCIDENTAL
S N P
EQUENCES OF UCLEAR OWER
P
LANTS

by
César Berna Escriche
Licenciado en Ciencias Físicas
at the Universitat de València
Ingeniero Industrial
at the Universitat Politècnica de València

Submitted to the Instituto Universitario de Ingeniería Energética
in partial fulfilment of the requirements for the degree of

DOCTOR of PHILOSOPHY

at the

Universitat Politècnica de València

September 2017

Certified by Dr. José Luis Muñoz-Cobo González. Thesis supervisor
Certified by Dr. Facundo Alberto Escrivá Castells. Thesis supervisor

I dedicate this work to
my parents Pedro and Pascuala,
to my Wife Reme
and to everyone
who awakened in me
the curiosity to learn

To my parents & wife:
Sir Isaac Newton once said ‘If I have seen further,
it is by standing upon the shoulders of giants’,
Thank you for being my giants.
.
ACKNOWLEDGEMENTS
The present document summarizes my research endeavors at the Group of Thermal-
hydraulic and Nuclear Engineering of the Institute of Energy Engineering of the Universitat
Politècnica de València (UPV). It does not fully capture, however, the wealth of
experiences provided by many outstanding and brilliant people I had the privilege of
meeting over these years. This work could not have come to fruition without the wonderful
atmosphere existing in the Group of Thermal-hydraulic and Nuclear Engineering.
I owe my full and sincere gratitude to my two thesis supervisors Dr. Jose Luis Muñoz-
Cobo González and Dr. Alberto Escrivá Castells. They devised this thesis and gave me the
chance to carry it out. For their full confidence in me, for their contribution to this work
through many hours of useful scientific discussions, for their advice, for their enthusiasm
developing my interest and for many more reasons I will be eternally grateful.
I want to express my gratitude to Dr. Luis Enrique Herranz Puebla and Dr. Claudia
Lopéz del Prá for their contribution to this PhD work. Without the collaboration between
CIEMAT-UPV to carry out the works of the ARTIST-España Project, that began 10 years
ago, this thesis would not have been possible.
I want to express my thankfulness to Dr. José Enrique Juliá Bolivar for his
contribution to this PhD work. Without his free collaboration to carry out the experiments
of pool discharge this thesis will not has had the circle closed.
I also want to thank my colleagues and friends of the Instituto de Ingeniería
Energética of the UPV, José Luis, David, Yago and Enrique for all our technical and not-
technical talks over these last years. The not technical ones had made the hard work days
more enjoyable. I do not want to forget all colleagues and friends who worked here through
the recent years: Arturo, Cris, Laura, Rafa, David and Tania.
Last, but not least, I would like to say that my words would not be enough to express
how I am feeling inside. My parents, without you and your full support I would never have
come so far, thank you for all your encouragement and support during all this time. I would
also like to express my gratefulness to my wife Reme for your tolerance and support
through these years, to support me and put up with my bad moments. I also want to thank
all who have crossed my path and helped to found the right track, or posed me facing new
challenges. However, it also helped me remember what is really important in life.

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ABSTRACT
The turbulent submerged jets can be found fairly frequently in a great variety of processes,
their study is essential in many industrial processes and engineering applications, such as in
underwater propulsion, in metallurgical processes, in chemical processes or in the nuclear
industry, among others. Within the nuclear world the submerged jets can occur in light
water reactors (LWR), in both pressurized water reactors (PWRs) and boiling water
reactors (BWR). These submerged jets are usually associated with complex multiphase
flows, so that all processes occurring after such injection will be essentially unstable and
turbulent.
A hypothetical severe accident in a reactor can cause deterioration of the core, so that the
fission products can escape from the core and be transported through the primary system
and, finally, can be released to the surrounding environment. But if there is a volume of
water in the escape pathway of aerosols, a discharge in the shape of submerged jet can
occur, whether in a suppression pool (during an accident with loss of power, SBO, in a
water reactor boiling BWR) or in the secondary of a steam generator (in an accidental
breakage sequence tube / s in U in a steam generator, SGTR, in a pressurized water reactor,
PWR). So that there is a capture of aerosols in those volumes, being reduced the amount of
them that escape outside. Usually these sequences have been considered only for BWRs
and for low discharge velocities, but these may also take place at higher velocities and, as
mentioned previously, in PWRs.
Throughout this thesis there is a contribution to a better understanding and quantification of
natural mitigation processes that occur when a jet is discharged into a volume of water, so
that it can be applied to discharges in suppression pools in a SBO sequence (BWRs), and
inside of a steam generator during a SGTR event (PWRs). Being the central activity the
expansion of SPARC90 code capabilities, so as to be able to quantify the aerosol capture
that occurs when the discharge takes place at high velocity (originally the code only was
developed to study discharges under globular regime, i.e., injection at low velocity).
So the process followed to carry out this work can be divided into several stages. The first
one focuses on the literature search for available information, in a specific way on
submerged jets and, given the scarce specific information, this has been extended to the
literature search of processes with phenomenologies that present analogies with submerged
jets. Within this part, it has on the one hand, finding aspects of jet hydrodynamics and on
the other, those related to aerosol capture processes. In a second stage, there are aspects of
the implementation into the new code subroutines of the expressions found and / or
developed in the previous stage. While for the third stage, remains the assessment of the
capabilities and behavior of the new models implemented in the code. For this last stage,
first, it has been proceeded to conduct a verification process which has been tested the code
robustness. And secondly, it has been proceeded to perform a validation process, which has
been carried out through the comparison of the results predicted by the code against the
limited experimental data that are available under similar conditions to those of the model.
vii
Being the comparison against the experimental data satisfactory, showing a marked
improvement in the code capabilities.

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