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Research Papers: Nuclear Power

# Core Melt Solidification Characteristics in PRV Lower Head-Experimental Results From LIVE Tests

[+] Author and Article Information
Xiaoyang Gaus-Liu

Institute for Energy and Nuclear Technologies, Karlsruhe Institute of Technology, Hermann-von-Helmholz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germanyxiaoyang.gaus-liu@kit.edu

Alexei Miassoedov, Thomas Cron, Jerzy Foit, Thomas Wenz, Silke Schmidt-Stiefel

Institute for Energy and Nuclear Technologies, Karlsruhe Institute of Technology, Hermann-von-Helmholz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany

J. Eng. Gas Turbines Power 132(10), 102924 (Jul 16, 2010) (6 pages) doi:10.1115/1.4001081 History: Received October 02, 2009; Revised October 15, 2009; Published July 16, 2010; Online July 16, 2010

## Abstract

Core melt solidification phenomena in the lower plenum of pressurized reactor vessel during external reactor vessel cooling is investigated in late in-vessel phase experiment tests under different external cooling conditions and melt pouring positions. The melt solidification behavior, which has not yet been given sufficient attention, is an important issue since it influences not only the transient but also the steady state of melt pool thermal hydraulics. A noneutectic melt ($80 mol %$$KNO3–20 mol %$$NaNO3$) was used to simulate the core melt. It has been found out that when the vessel is cooled with water during the whole test period (water cooling), the cooling is more effective than the case that the vessel lower head is first cooled with air and flooded by water (air/water cooling). Water cooling at the beginning leads to faster buildup of crust layer on the vessel inner wall and lower crust thermal conductivity compared with air/water cooling. In comparison with the air/water cooling, the water cooling also achieves shorter time period of crust growth. During the solidification period in all tests, the constitutional supercooling condition is fulfilled. Pouring position near the vessel wall results in considerable asymmetry in the heat flux distribution through the vessel wall.

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## Figures

Figure 5

Crust thickness profile under different cooling conditions: L3: air/water cooling; L3A: water cooling

Figure 7

Crust thermal conductivity at the polar angle of 37.6 deg

Figure 8

Crust liquidus temperature and crust composition in L3A test at polar angle of 37.6 deg

Figure 9

SEM image of the crust. KNO3 mol % concentration: point 1: 89%; point 2: 74%

Figure 10

Temperature of the melt ahead of the crust in transient state (top) and in steady state (bottom)

Figure 4

Steady state heat flux distribution: (top) L3 test, air/water cooling and (bottom) L3A, water cooling

Figure 6

Crust growth rate under different initial cooling condition at the polar angle of 52.9 deg during the 10 kW phase

Figure 3

Melt temperature evolution at 174 mm from the vessel vertical axis: (top) air/water cooling and (bottom) water cooling

Figure 1

LIVE test vessel and instrumentation

Figure 2

Liquidus line of KNO3–NaNO3 measured at KIT

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