atw 2018-02


atw Vol. 63 (2018) | Issue 2 ı February


emergency air filtration system of

the plant is needed in addition to limit

the radionuclide releases into the


With respect to mitigation of the

hydrogen risk in the annulus it is

demonstrated that the implementation

of a small number of PARs would

be a very efficient and fully passive

mitigation measure without additional

aerosol release into the environment.


The authors like to acknowledge the

German Federal Ministry for the

Environment, Nature Conservation,

Building and Nuclear Safety for the

financial support of the project



[1] Recommendation of German Reactor

Safety Commission (RSK): Hydrogen

Release from Containment. Annex of

the Proceedings of 475 th meeting of

RSK, 15.04.2015.

[2] Band, S., Schwarz, S., Sonnenkalb, M.:

Nachweis der Wirksamkeit von

H 2 -Rekombinatoren auf der Basis

ergänzender analytischer Untersuchungen

mit COCOSYS für die

Referenzanlage GKN-2. Final Report

of BMUB project 3609R01375,

GRS-A-3652, March 2012.

[3] Schwarz, S., Sonnenkalb, M.: Analyse

der Belastung von Gleitdruckventuriwäschern

in SHB-Ventingsystemen

von DWR KONVOI und

SWR-72 bei Unfällen. Final Report

of BMUB project 3613R01320,

GRS-A-3820, August 2015.


Ivan Bakalov

Research Fellow

Gesellschaft für Anlagen- und

Reaktorsicherheit (GRS) gGmbH,

Kurfürstendamm 200

10719 Berlin, Germany

Dr. Martin Sonnenkalb

Department Head

Gesellschaft für Anlagen- und

Reaktorsicherheit (GRS) gGmbH,

Schwertnergasse 1

50667 Cologne, Germany

Sensitivity Analysis of MIDAS Tests Using

SPACE Code: Effect of Nodalization

Shin Eom, Seung-Jong Oh and Aya Diab

1 Introduction The SPACE thermal hydraulic analysis computer code has been developed by KHNP (Korea

Hydro and Nuclear Power) [1]. The SPACE code is based on the three-field governing equations (vapor, continuous

liquid, and droplet). It improves the accuracy by solving the mass, energy, and momentum conservation equations for

each phase and adopts the proven numerical methods as well as the models for various thermal hydraulic phenomena.

With the new code, the best estimate

LOCA (Loss Of Coolant Accident)

methodology needs to be reestablished.

For APR1400 LBLOCA (Large

Break LOCA, APR1000: Advanced

Power Reactor 1000 MWe), KREM [2]

has been developed one of the best

estimate methodology using RELAP5

code [3, 4]. With the new code, one

needs to look at the code performance

to develop best estimate + uncertainty

method. In this paper, as a part of the

development effort, we focus on the

impact of nodalization on the code

predictions, more specifically, on the

ECC bypass phenomenon.

For APR1400 LBLOCA, ECC bypass

phenomenon is one of the important

phenomena which would occur in the

downcomer during the reflood phase

of LOCA [5]. To study the ECC bypass

phenomenon, KAERI carried out the

ECC bypass tests using the MIDAS

facility [6, 7, 8]. MIDAS simulation is a

part of the assessment of the KREM.

One of the important parameters

for the MIDAS test is ECC bypass fraction.

The results for each nodalization

were compared with MIDAS test data.

The main aim of this study is therefore

to examine the sensitivity of the

SPACE code to the number of thermal

hydraulic channels in the downcomer


| | Fig. 1.

Isometric View of the MIDAS Facility [7].

| | Fig. 2.

Top View of the MIDAS Facility Downcomer [7].

2 MIDAS test

The MIDAS test facility is a steamwater

separate effect test facility

which is scaled down from APR1400

[9]. It is focused on the investigation

of the ECC bypass phenomenon in the

downcomer annulus. The test condition

was determined, based on the

analysis of the TRAC (Transient

Reactor Analysis Code) [10]. The

isometric and top view of the MIDAS

facility is depicted in Figure 1 and

Figure 2.

To investigate the effect of the DVI

injection nozzle location on the ECC

bypass fraction, fifteen separate effect

Environment and Safety

Sensitivity Analysis of MIDAS Tests Using SPACE Code: Effect of Nodalization ı Shin Eom, Seung-Jong Oh and Aya Diab