atw 2017-12
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<strong>atw</strong> Vol. 62 (<strong>2017</strong>) | Issue <strong>12</strong> ı December<br />
| | Fig. 13.<br />
Debris Mass Changes in Sensitivity Analysis.<br />
| | Fig. 14.<br />
Success Region for In-Vessel Injection without the first relocation to the RPV lower plenum.<br />
ENVIRONMENT AND SAFETY 753<br />
| | Fig. 15.<br />
Metallic Layer Mass Fraction in RPV lower plenum.<br />
| | Fig. 16.<br />
Total Debris Mass Rearrangement based on the first relocation time.<br />
4 Summary and conclusions<br />
In this paper, a sensitivity study is<br />
performed to the in-vessel phase of<br />
SAM for a Korean 1000 MWe NPP<br />
using ROAAM+ framework. The<br />
selected scenario is SBO with RCS<br />
depressurization followed by in-vessel<br />
external injection. The impacts of<br />
injection timing and flow rate as well<br />
as the uncertainties associated with<br />
the core melting and relocation process<br />
have been examined. The main<br />
conclusions that could be drawn from<br />
this work are summarized as follows:<br />
• In order to implement the in-vessel<br />
phase of SAM strategy, it is recommended<br />
to open the POSRVs<br />
within 30 minutes after the entry<br />
of a severe accident.<br />
• If the external injection with the<br />
flow rate of more than 10 kg/sec<br />
into the vessel performed within<br />
5.0 hours after the entry of a severe<br />
accident, the molten mass is<br />
retained in the core. The first<br />
relocation to the RPV lower plenum<br />
is not occurred.<br />
• When the reactor vessel integrity<br />
is maintained through the derived<br />
SAM strategy, the maximum<br />
amount of melt accumulated in the<br />
RPV lower plenum is about 114 tons.<br />
The derived SAM strategy and<br />
the information on core melting and<br />
relocation may be used as the initial<br />
conditions for the next phase of SAM<br />
evaluation such as ERVC and the<br />
ex-vessel phase in the future.<br />
Acknowledgments<br />
This study was supported by the <strong>2017</strong><br />
research fund of the KEPCO International<br />
Nuclear Graduate School<br />
(KINGS), Republic of Korea.<br />
References<br />
[1] Westinghouse, Status report 81 –<br />
Advanced Passive PWR (AP 1000),<br />
IAEA, 2011.<br />
[2] Gidropress, Status report 93 –<br />
VVER-1000, IAEA, 2011.<br />
[3] AREVA NP & Mitsubishi Heavy<br />
Industries, Status Report – ATMEA1TM,<br />
IAEA, 2015.<br />
[4] KEPCO & KHNP, CHAPTER 19<br />
PROBABILISTIC RISK ASSESSMENT<br />
AND SEVERE ACCIDENT EVALUATION,<br />
U.S. NRC, 2014.<br />
[5] KEPCO & KHNP, Status Report 103 –<br />
Advanced Power Reactor (APR1000),<br />
IAEA, 2011.<br />
[6] T. G. Theofanus, On Proper Formulation<br />
of Safety Goals and Assessment of<br />
Safety Margins for Rare and High-<br />
Consequence Hazards, in Reliability<br />
Engineering & System Safety, 1996.<br />
[7] W. Y. S. A. J. S. K. F. X. C. T. S. T.G.<br />
Theofanous, Lower head integrity<br />
under steam explosion loads, in Nuclear<br />
Engineering and Design, 1999.<br />
[8] C. L. S. A. S. A. O. K. T. S. T.G.<br />
Theofanous, In-vessel coolability and<br />
retention of a core melt, in Nuclear<br />
Engineering and Design, 1997.<br />
[9] P. K. Sergey Galushin, Analysis of core<br />
degradation and relocation phenomena<br />
and scenarios in a Nordic-type BWR, in<br />
Nuclear Engineering and Design, 2016.<br />
[10] W. V. P. K. C.-T. T. A. Goronovski, Effect<br />
of Corium Non-Homogeneity on Nordic<br />
BWR Vessel Failure Mode and Timing,<br />
in ICAPP-2015, 2015.<br />
[11] S. L. N. K. P. Yakush, Risk and uncertainty<br />
quantification in debris bed coolability,<br />
in NURETH 15, 2013.<br />
[<strong>12</strong>] D. B. S. K. P. Grishchenko, Development<br />
of TEXAS-V code surrogate model for<br />
assessment of steam explosion impact<br />
in Nordic BWR, in NURETH-16, 2015.<br />
[13] S. G. Pavel Kudinova, A FRAMEWORK<br />
FOR ASSESSMENT OF SEVERE ACCIDENT<br />
MANAGEMENT EFFECTIVENESS IN<br />
NORDIC BWR PLANTS, in Probabilistic<br />
Safety Assessment and Management<br />
PSAM <strong>12</strong>, 2014.<br />
[14] Westinghouse Electric Company,<br />
APR 1400 RCP Seal Design and ELAP<br />
Capability, 2014.<br />
Environment and Safety<br />
Analysis of the In-Vessel Phase of SAM Strategy for a Korean 1000 MWe PWR ı Sung-Min Cho, Seung-Jong Oh and Aya Diab