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

VGB PowerTech 7 l 2021
Verification of SPACE code based on an MSGTR experiment at the ATLAS-PAFS facility
Non-dimensional Collapsed water level (-)
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
SG Level for PAFS operation
0.4
SG collapsed water level
Exp. (SG-1) SPACE code (SG-1)
0.2
Exp. (SG-2) SPACE code (SG-2)
0.0
0.0 0.2 0.4 0.6 0.8 1.0
Non-dimensional Time (-)
Non-dimensional Mass flow rate (-)
1.0
0.8
0.6
0.4
0.2
0.0
Mass flow rate of PAFS line
Exp. (Steam supply line)
Exp. (Return water line)
SPACE code (Steam supply line)
SPACE code (Return water line)
-0.2
0.0 0.2 0.4 0.6 0.8 1.0
Non-dimensional Time (-)
Fig. 9. Comparison result of SG collapsed water level.
Fig. 10. Comparison result of PAFS line mass flow rate.
1.3
1.0
Non-dimensional Collapsed water level (-)
1.2
1.1
1.0
0.9
Collapsed water level in PCCT
Exp.
SPACE code
0.8
0.0 0.2 0.4 0.6 0.8 1.0
Non-dimensional Time (-)
Non-dimensional Temperature (-)
0.8
0.6
0.4
0.2
0.0
Fluid temperature of PAFS line
Experiment PAFS model Default option
Steam supply Steam supply Steam supply
Return water Return water Return water
-0.2
0.0 0.2 0.4 0.6 0.8 1.0
Non-dimensional Time after PAFS opseration (-)
Fig. 11. Comparison result of PCCT water level.
Fig. 12. Comparison result of fluid temperature at PAFS line after PAFS
operation.
lation result is consistent with the experimental
results. Following the PAFS operation,
the pressure in an intact SG-2 drastically
decreased due to the cooling by PAFS;
the SG-2 depressurization trend is similar
to the core cooling rate trend.
F i g u r e 9 shows a comparison of the SG
collapsed water levels in the experiment
and in the SPACE calculation. The water
level of broken SG-1 increased and reached
the full water level. By contrast, that of
an intact SG-2 decreased rapidly and
reached a set point of the PAFS operation.
As the PAFS signal was triggered, the PAFS
operation valve automatically opened, and
the main steam from the SG-2 flowed
into the steam supply line. As shown in
F i g u r e 10 , the mass flow peaked, and
then natural circulation flow was formed.
The mass flow rate in the case of SPACE calculation
was consistent with the experimental
result. The main steam from the
steam supply line flowed into the condensation
tubes, and the condensate circulated
through the return water line to the economizer
of the steam generator. After the
PAFS was actuated, the water level also increased
due to the thermal expansion, as
shown in F i g u r e 11 .
3.2.4 Wall condensation heat transfer
model for PCHX
The wall condensation heat transfer rate in
PCHX is one of the dominant factors for determining
the PAFS cooling capability.
Therefore, the many precedent studies related
to condensation in PCHX were performed.
The wall condensation models
were incorporated into the SPACE code
heat transfer package. For pure steam condensation,
like the problem addressed in
this paper, the same model used in RE-
LAP5/MOD3.3 was selected as a default
model. The maximum value among Nusselt’s
[14], Shah’s [15], and Chato’s [16]
correlations is used to consider the geometric
and turbulent effects. The experimental
correlation for PAFS is also included in the
wall condensation model as an option in
SPACE code [17]. Based on the calculation
results mentioned in chapter 3.2.1, this
model was applied. In this section, the default
model and experiment correlation
model for PAFS were compared to confirm
the prediction ability of SPACE code for
PCHX cooling performance. Chen’s model,
which is the default option in SPACE code,
is applied to the outside of PCHX [18].
The fluid temperature after PAFS operation
is shown in F i g u r e 1 2 . The calculation
result shows that the fluid temperature on
the return water line is higher than the experiment,
and that the default option case
is highest. That means that the calculation
results which were obtained using the default
option and the PAFS model underestimated
cooling performance. However, the
calculation using the PAFS model was
more accurate than the default option.
4. Conclusions
In this study, a MSGTR experiment with
the PAFS operation performed by KAERI
was simulated using the SPACE code. This
study focused on verifying the prediction
capability of the SPACE code for MSGTR
accidents, which is one of the multiple fail-
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