Experimental Studies on Two-Layer Corium Heat Transfer in Light Water Reactor Lower Head in LIVE2D Facility

Figures & data

Fig. 1. Heat flux focusing effect at vessel in the upper metallic layer.

Fig. 2. LIVE2D test vessel during the two-layer test. The upper layer thickness is 75 mm.

TABLE I Thermal-Physical Properties of Simulant and Prototypical Materials

Property	Lower Layer Simulant: 50% KNO3-50% NaNO3		Upper Layer Simulant: Thermal Oil		Liquid Steel
	at 224°C	at 260°C	at 140°C	at 220°C	at 1327°C
Density (kg/m^3)	1964	1937	755	540	7020
Kinematic viscosity (mm^2/s)	2.76	2.23	11	9	5.84E−7
Thermal expansion coefficient [(1/K) × 10^−4]	1.05		44		1.1
Thermal conductivity [W/(mK)]	0.48	0.47	0.15	0.15	25
Thermal capacity [J/(gK)]	1.29	1.31	1.7	1.83	0.835
Prandtl number	14.5	12.0	94	59	0.14
Ra sidewall	10^12 to 10^13		10^8 to 10^9		10^8

TABLE II Thermocouple Positions at IT and the Upper Layer Positions

Lower Layer			Upper Layer			Interface/Upper Surface Position
Thermocouple	Polar Angle (deg)	Height (mm)		Polar Angle (deg)	Height (mm)		Polar Angle (deg)	Height (mm)
IT1	0	0	IT12	73	355	Layer interface	71.6	340
IT2	21	33	IT9	76	376	35-mm upper layer	75.8	375
IT3	30	67	IT13	80	406	75-mm upper layer	80.5	415
IT4	42	128	IT10	83	436	110-mm upper layer	84.6	450
IT5	51	184
IT6	58	234
IT7	66	291
IT11	68	313
IT8	71	335

Fig. 3. Temperature measurement inside and on the test vessel.

TABLE III Test Procedures

Melt Layer Configuration	Time of Initiation (h)	Power Subsequence in the Lower Layer, No Power in the Upper Layer
One layer: only salt layer	0	Variable power, stabilization of lower layer temperature
Two layers: upper layer 35 mm	4.4	1130 W → 1400 W → 900 W
Two layers: upper layer 75 mm	47.1	1300 W → 1800 W → 1150 W
Two layers: upper layer 110 mm	71	1800 W → 2200 W → 1600 W
Two layers: upper layer 75 mm	100.5	Extraction part of the oil from the vessel, power remained at 1600 W

Fig. 4. Melt temperature progression in lower and upper layers at radius of 1 cm. The height reference is the layer interface at 340 mm.

Fig. 5. Vertical temperature profiles at three radii in the upper layer. There is no complete interface crust during the power level.

Fig. 6. Radical MTs at (a) the layer interface and (b) at 390-mm height. (* indicates there is no complete interface crust during the power level.)

Fig. 7. Two-layer melt pool: (a) the interlayer crust is partially melted down in the central region, and (b) a new interlayer crust formed after power reduction which was slightly lower than the former one.

Fig. 8. Wall inner surface temperature in the upper layer and lower layer.

Fig. 9. Heat fluxes at different height positions of the vessel wall in three upper layer thicknesses.

TABLE IV Upper Wall/Lower Wall Heat Transfer Ratio and Heat Loss Ratio

Upper Layer Thickness: 35 mm
Power input (W)	1130	940	1085	1310	1405	900
Qw,up/Qw,dn^a,b	0.276	0.274	0.273	0.325	0.327	0.244
Qw/Qinput^c,d	0.418	0.425	0.379	0.366	0.369	0.393
Upper Layer Thickness: 75 mm
Power input (W)	1300	1800	1150	1600
Qw,up/Qw,dn^a,b	0.584	0.584	0.556	0.651
Qw/Qinput^c,d	0.414	0.452	0.439	0.453
Upper Layer Thickness: 110 mm
Power input (W)	2200	1800	1400	1600
Qw,up/Qw,dn^a,b	0.754	0.911	0.830	0.867
Qw/Qinput^c,d	0.469	0.471	0.469	0.460

^aQ_w,up: heat transfer rate at the wall immersed in the upper layer.

^bQ_w,dn: heat transfer rate at the wall immersed in the lower layer.

^cQ_w,: total heat transfer rate at the wall immersed in the melt.

^dQ_input: power input in the lower layer.