Experimental and Analytical Investigation of Formation and Cooling Phenomena in High Temperature Debris Bed

Figures & data

Figure 1. A chain of detailed individual phenomena related to the formation and cooling of debris.

Table 1. Important phenomena relevant to the formation and cooling of debris beds, test data and validation plan of THERMOS.

		Existing test data *1
Identification of important phenomena		Available tests	Completed/planned validation*2	New validation tests added in this project
I: Molten jet breakup and formation of debris bed: THERMOS module = JBREAK
Focusing data items		FARO [15]	P	DEFOR-A [11–13,23]
		JAEA [14]	-
		COTELS [17]	-
a.	Breakup behaviors (breakup length, etc.)	✓		✓
b.	Droplet trajectories			✓
c.	Geometries of debris beds at discrete elevations			✓
d.	Velocity and temperature fields in a pool during jet breakdown			✓
e.	Distributions of entrained droplet size	✓		✓
f.	Mass fraction of agglomeration of partially solidified droplets			✓
II: Melt spread on a cavity floor submerged under water: THERMOS module = MSPREAD
Focusing data items		KATS-12 [25]	C [30]	PULiMS [10–13]
		ECOKATS-1 [26]	C [29]
		VULCANO-VE-U7 [27]	C [30]
a.	Transient temperature distributions	✓ (dry floor)		✓ (wet floor)
b.	Non-isotropic spreading behaviors	✓ (dry floor)		✓ (wet floor)
c.	Jet impinging behavior on a floor	✓ (dry floor)		✓ (wet floor)
d.	Growth of upper and bottom crusts	✓ (dry floor)		✓ (wet floor)
e.	Upper surface heat transfer			✓ (wet floor)
f.	Bottom surface heat transfer (crust/melt-substrate)	✓ (dry floor)		✓ (wet floor)
g.	Bottom surface heat resistance (roughness/water intrusion, etc.)			✓ (wet floor)
h.	Substrate materials (concrete/ceramic, etc.)	✓ (dry floor)
i.	Surface unevenness and melt eruption in case of wet floors			✓ (wet floor)
III: Water-vapor two-phase thermal hydraulics in a heterogeneous debris bed piled on a cavity floor: THERMOS module = DPCOOL
Focusing data items		DEBRIS Top/bottom flood [42,43]	C [8]	Under planning
		DEBRIS downcomer [44]	C [7]
		Chu’s air injection tests [36]	C [8]
		COOLOCE13 [39]	C [7]
a.	Fluid-particle friction	✓
b.	Water-vapor friction	✓
c.	Fluid-particle heat transfer	✓
d.	Dryout due to the counter current flow limitation	✓
e.	Down-comer and chimney effects	✓
f.	Combined solid contact and fluid convection heat transfer			✓
IV: Self-leveling of particle layers: THERMOS module = DPCOOL
Focusing data items		ANL [48]	-	No plan
		PDS [51–53]	C [7]
		JAEA [49,50]	P
a.	Influence of gas velocity on particle flow	✓
b.	Influence of gravity – buoyancy on particle flow	✓
c.	Influence of instantaneous and reposing angles on particle flow	✓
d.	Influence of particle surface geometry on particle flow	✓
V: Penetration of molten metals and/or oxides into solidified oxide particle beds): THERMOS module = REMELT
Focusing data items		MP-2 [59]	P	REMCOD1/2/3 [11–13]
		PHEBUS-FPT4 [58]	P
		MASCA [57]	-
a.	Influences of contact angle on penetration flow			✓
b.	Influences of porosity (saturation of pores) on penetration flow			✓
c.	Influences of temperature distribution on penetration flow			✓
d.	Influences of material interactions on penetration flow	✓

*1: ✓= Adequate resolution for validating THERMOS modules *2: C = Completed, P = Planned

Figure 2. A structure of THERMOS composed of four modules.

Figure 3. Schematic view of three facilities in the KTH test series.

1. DEFORA [9]

2. PULiMS [9]

3. REMCOD-1 and 2 [11–13]

Table 2. Schedule of experimental and analytical investigation of the formation and cooling phenomena of high-temperature debris bed [9–13].

Figure 4. Representative data of the DEFOR-A test.

1. Agglomerated debris data [11–13], [23], [61]

2. Laser scanning image of captured debris (A27) [13]

Table 3. Test matrix of DEFOR-A [11–13].

Test parameters	A7^*3	A9^*3	A22_S1^*3	A23	A24	A25	A26	A27^*4
Charged composition for melt preparation^*1, weight % of Bi2O3	42.6
Melt composition prior to delivery^*2, weight % of Bi2O3	N/A							35.8 ± 0.9
Melt temperature in the funnel, K	1349	1343	1221	1280	1248	1216	1299	1342
Oxidic melt superheat in the funnel, K	206	200	78	137	105	73	156	52^*5
Nozzle diameter, mm	25	20	25	25	34	34	34	20
Free fall height in the atmosphere, mm	200	180	200	205	170	170	170	195
Estimated break up length, mm	453	442	507	564	518	510	510	612
Depth of Catcher-1, mm	520	620	615	615	700	700	700	620
Duration of melt release, sec	10	11	6.5	5.8	5.3	5.7	5.5	6.9
Average melt flow rate, l/sec	0.3	0.273	0.42	0.54	0.62	0.59	0.59	0.54
Water pool depth, m	1.42	1.52	1.515	1.515	1.6	1.6	1.6	1.52
Water initial temperature, K	356	355	346	332	346	363	346	360.5
Water subcooling, K	17	18	27	41	27	10	27	12.5

*1 Composition of the Bi₂O₃:WO₃ system charged into the furnace.

*2 Melt composition in the furnace prior to delivery into the test section estimated by SEM/EDX analysis.

*3 A7, A9 and A22_S1 were conducted under different projects [12,61].

*4 A27 is a confirmatory case of A9

*5 The superheat is based on the composition analysis. In other cases, the superheat is based on the initial melt composition.

Table 4. Test matrix of PULiMS [10–13].

Test parameters	E7	E8	E9	E10	E11	E12	E13	E14	E15	E16	E17	E18
Charged composition, weight % of Bi2O3 ^*1	42.6
Melt composition, weight % of Bi2O3 ^*2	N/A									36.5 ± 0.9	25.4 ± 0.8	41.0 ± 1.0
Symmetry	360°	360°	360°	180°	180°	180°	180°	180°	180°	90°	90°	90°
Melt temperature in the funnel, K	1235	1168	1182	1179	1189	1158	1219	1182	1293	1284	1303	1164
Oxidic melt superheat in the funnel, K	92.2	25.2	39.2	35.7	46.1	15.4	75.6	38.7	150.2	9^*3	−164^*3	−17^*3
Nozzle diameter, mm	20	20	15	20	30	15	15	15	17	17	17	17
Free fall height in the atmosphere, mm	200	200	200	90	65	122	72	72	104	65	56	56
Total released mass of melt, kg	28.1	25.3	27.3	30.8	39.3	32.6	23.8	27.2	44.2	17.7	2.3	15.1
Duration of melt release, sec	16.9	17.6	24.9	17	10.6	55	21.9	22.4	16.3	11.1	11.8	20.7
Average melt flow rate, kg/sec	1.66	1.44	1.10	1.81	3.69	0.59	1.09	1.21	2.71	1.59	0.15	0.73
Water pool depth, m	0.100	0.200	0.200	0.200	0.190	0.150	0.200	0.200	0.168	0.201	0.210	0.210
Water initial temperature, K	364.2	369.1	369.1	363.2	364.2	367.8	369.2	368.7	365.0	363.6	357.2	364.2
Water subcooling, K	9.0	4.1	4.1	10.0	9.0	5.4	4.0	4.5	8.2	9.6	16.0	9.0
Particulate debris mass fraction, %	5.8	2.3	1.9	2.5	3.8	1.2	1.8	1.6	8.6	4.2	16.5	2.2

*1 Composition of the Bi₂O₃:WO₃ system charged into the furnace.

*2 Melt composition in the furnace prior to delivery into the test section estimated by SEM/EDX analysis.

*3 The superheat is based on the composition analysis. In other cases, the superheat is based on the initial melt composition.

Figure 5. Representative data of the PULiMS test.

1. Comparison of spreading front positions measured by video analysis [12,13]

2. End state of E10 [12]

3. Post examination of E10 [12]

4. Post examination of E13 [12]

Figure 6. Melt-coolant interactions observed in PULiMS.

1. E7 [10]

2. E15 [12]

3. E17 [13]

Table 5. Test matrix of REMCOD-1 and 2 [11–13].

Phase		Exploratory test		REMCOD-1				REMCOD-2
Focus point		Commissioning & exploring test procedures		Crust formation	Penetration into superheated layers	Remelting of once solidified metal	Penetration into superheated layers	Penetration into superheated layers under slightly wettable conditions
Case IDs		E01-E03	E04-E07	E08	E09	E10	E11	E12	E13	E14	E15
Phenomena	Melt penetration depth			✓				✓	✓	✓	✓
	Melt infiltration				✓		✓
	Remelting					✓
Design feature	Exploratory tests	✓	✓
	Heaters			✓	✓	✓	✓	✓	✓
	Force sensors		✓	✓	✓	✓	✓	✓	✓
	Additional thermocouples			✓	✓	✓	✓	✓	✓
	Installation of catchers				✓	✓	✓
	Laser scanning		✓	✓	✓	✓	✓
	Air venting								✓	✓	✓
	Improved measurement							✓	✓	✓	✓
Melt	Material (MP)*1	Tin (505.2 K)		Tin + Bismuth (eutectic; 412.2 K)
	Temperature	Superheated
Particle layer	Compartments	C1-C3	C1-C4	C1-C4	C1-C4	C1-C2	C1-C4	C1-C4	C1-C4	C1-C4	C1-C4
	Shape	Cylinders and spheres (Al2O3/SS/glass/ZrSiO4)							Spherical particles (Cu/SS)
	Porosity	0.31–0.456							0.33–0.41
	Hydraulic diameter	0.24–2.75 mm
	Temperature	Room temperature		<412.2 K	>412.2 K	Initially<412.2 K; reheating >412.2 K	>412.2 K	<412.2 K			>412.2 K
	Wettability	Non-wettable (> 90${ }^{\circ }$)/Neutral (glass) ($\sim$90${ }^{\circ }$)							Wettable (< 90${ }^{\circ }$)

*1: Melting point

Figure 7. Representative data of the REMCOD test.

1. End state of E11 [12]

2. Penetration histories in E11 [12]

3. Penetration vs bed temperature in E08 [12]

4. Melt retention vs porosity in E09/E11 [12]

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