VGB POWERTECH 7 (2021) - International Journal for Generation and Storage of Electricity and Heat

Study on the integrity of containment against hydrogen threats VGB PowerTech 7 l 2021
Comprehensive analytical study on
the integrity of containment against
hydrogen threats during severe
accidents in 650 MWe PWR
Yu Jung Choi, Doo Yong Lee, Jin Yong Lee, Youn Joon Choo and Dae Young Lee
Kurzfassung
Analytische Studie zur Integrität des
Sicherheitsbehälters bei schweren
Unfällen mit Wasserstofffreisetzung
in einem 650-MWe-DWR
Ungeachtet der Installation von PARs (Passive
Auto-Catalyst Recombiners) in allen in Betrieb
befindlichen KKWs (Kernkraftwerken) in Korea
als Gegenmaßnahme zur Kontrolle von Wasserstoff
bei schweren Unfällen nach den Nuklearunfällen
in Fukushima, gibt es Bedenken über wasserstoffbedingte
Risiken wie Wasserstoffverbrennung
oder Explosion in der Öffentlichkeit. Die
meisten Studien über Wasserstoff bei schweren
Unfällen konzentrierten sich auf das Verhalten
des Wasserstoffs im Sicherheitsbehälter. Daher
wurde in dieser Studie eine umfassende analytische
Untersuchung der Integrität eines Sicherheitsbehälters
zu Gefährdungen durch Wasserstoff
in KKWs durchgeführt. Als Referenzanlage
wurde der Westinghouse-PWR (Druckwasserreaktor)
des Typs 650 MWe ausgewählt. Um die
Integrität des Sicherheitsbehälters zu bestätigen,
wurde eine Analyse schwerer Unfälle mit dem
MAAP5-Code für die Referenzanlage durchgeführt.
Anschließend wurden die aus den Berechnungsergebnissen
von MAAP5 gewonnenen Informationen
zu Massen- und Energiefreisetzung
als Basisinformationen für die Analyse der Wasserstoffverbrennung
mit dem GASFLOW-MPI-
Code verwendet. Anschließend wurden die Ergebnisse
des Druckverhaltens bei der Wasserstoffverbrennung
aus dem GASFLOW-MPI-Code
für die Bewertung der strukturellen Reaktion
auf die Integrität eines Sicherheitsbehälters mit
dem ABAQUS-Code verwendet. Schließlich bestätigten
die Bewertungsergebnisse, dass die
strukturelle Integrität des Sicherheitsbehälters
für das Referenz-KKW gegenüber Gefährdungen
durch Wasserstoff innerhalb des Sicherheitskriteriums
für den Sicherheitsbehälter lag. l
Authors
Yu Jung Choi
aKorea Hydro & Nuclear Power Co.,Ltd
Daejeon, Republic of Korea
Doo Yong Lee
Jin Yong Lee
Youn Joon Choo
Dae Young Lee
FNC Technology Co.,Ltd.
Gyeonggi-do, Korea
Regardless of installation of PARs (Passive
Auto-catalyst Recombiners) at all operating
NPPs (Nuclear Power Plants) in Korea as a
countermeasure of hydrogen control during
severe accidents after the Fukushima nuclear
accidents, there are still concerns about hydrogen-related
risks such as hydrogen combustion
or explosion for the public. But, most
hydrogen studies under severe accident conditions
were focus on the hydrogen behavior
in the containment. Therefore, comprehensive
analytical investigation on the integrity
of a containment against hydrogen threats in
NPPs was evaluated in this study. The Westinghouse
type 650 MWe PWR (Pressurized
Water Reactor) was selected as the reference
plant. To confirm the integrity of the containment
against hydrogen threats, severe
accident analysis was performed using the
MAAP5 code for the reference plant. Then,
mass and energy discharge information obtained
from the calculation results of MAAP5
was used for basic information of hydrogen
combustion analysis using the GASFLOW-
MPI code. And then, pressure response results
of hydrogen combustion from the GASFLOW-
MPI code were utilized for evaluation of
structural response to the integrity of a containment
using the ABAQUS code. Finally,
the assessment results confirmed that the
structural integrity of the containment for
the reference NPP against the hydrogen
threats was within the safety criterion for the
containment.
1. Introduction
Following the Fukushima nuclear accidents,
there has been growing interest in
developing effective countermeasures
against hydrogen explosions during severe
accidents at NPPs. As part of follow-up
measures, the Korean government has conducted
a comprehensive safety inspection
of all operating NPPs in Korea. A total of 50
recommendations for safety improvement
of operating NPPs were drawn as a result of
the safety inspection [1]. Among them, the
installation of passive hydrogen removal
facility was derived as one of the countermeasures
against severe accidents. The objective
of hydrogen control under severe
accidents is to secure the integrity of a containment
as the last barrier of defense in
depth. Accordingly, in order to hydrogen
control in the containment against events
such as hydrogen combustion or explosion
under severe accident conditions, PARs
(Passive Auto-catalyst Recombiners) were
additionally installed in all operating NPPs.
However, despite the installation of PARs,
there still remain concerns about the possibility
of hydrogen threats such as hydrogen
combustion or explosion in terms of
the integrity of the containment.
There are many studies on the behavior
and control of hydrogen in containment in
the events of severe accidents. THAI (Thermal-hydraulics,
Hydrogen, Aerosol, and
Iodine) projects, under the framework of
the international OECD/NEA (Organization
for Economic Cooperation and Development/Nuclear
Energy Agency), were
representative international joint research
projects. The THAI projects were performed
many experimental and analytical
studies in a total of three rounds from 2007
to 2019. Concerning hydrogen issues, hydrogen
distribution, hydrogen deflagration,
PAR performance under various conditions
such as ignition, O2 starvation,
counter-current flow conditions were performed
experiments and benchmark analysis
[2]. In Korea, hydrogen behaviors in
OPR1000 and APR1400 containment during
severe accidents were studied [3-4].
However, the THAI projects dealt only with
the behavior of hydrogen inside the THAI
facility, and all most analytical studies also
only dealt with the thermal-hydraulic behaviors
of hydrogen inside the containment.
In the event of a severe accident,
comprehensive quantitative evaluations of
the hydrogen threat and the consequent
structural integrity of the containment
have rarely been performed.
Therefore, in this study, a comprehensive
analytical evaluation of the integrity of the
containment building was performed to
check the possibility of hydrogen threats
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