Thermal properties of Three Mile Island Unit 2 core debris and simulated debris

Figures & data

Figure 1. Photographs of TMI-2 debris.

Figure 2. Microstructure of TMI-2 debris.

Table 1. List of TMI-2 debris samples.

Sample no.	Weight (g)	Density (×10^6 g/m^3)	Av. Porosity (%)	Main component
VIP-9D	21.9	7.80	32.1	(U, Zr)O2
VIP-9E	15.4	7.64	38.0	(U, Zr)O2
VIP-11A	226.5	6.32	12.2	Structure and control rod materials
VIP-11B	387.3	7.82	4.6	(U, Zr)O2
VIP-12A	33.5	8.25	18.8	(U, Zr)O2
VIP-12B	46.3	7.93	13.6	(U, Zr)O2
SIMDEBRIS-L		8.20	20.5
SIMDEBRIS-M		8.80	4.9
SIMDEBRIS-H		9.00	2.1

Figure 3. Microstructure of SIMDEBRIS (density: 8.2 g/cm³, porosity: 18–23%).

Table 2. Initial inventory of core materials in TMI-2 and composition of SIMDEBRIS.

Inventory of TMI-2		SIMDEBRIS
Material	Weight (kg)	Material	Composition (wt%)
UO2	93,100	UO2	72.1
Zircaloy	23,000	ZrO2	20.5
Stainless steel 304	4,640	Fe3O4	3.4
Inconel 718	1,210	Cr2O3	1.3
Ag-In-Cd	2,750	NiO	1.0
		Ag	1.7

Figure 4. Density of SIMDEBRIS as a function of temperature.

Figure 5. Estimated specific heat capacity of SIMDEBRIS in comparison with data of UO₂ and ZrO₂ [13,14].

Figure 6. Thermal expansion of SIMDEBRIS as a function of temperature.

Figure 7. Thermal diffusivity of TMI-2 debris, SIMDEBRIS, and UO₂ [20] as a function of temperature.

Figure 8. Thermal conductivity of TMI-2 debris and UO₂ [21,22] as a function of temperature. Values of TMI-2 debris were calculated with specific heat capacity and density of SIMDEBRIS.

Figure 9. Example of temperature history during measurement of melting temperature of SIMDEBRIS.

Figure 10. Pseudo-binary phase diagram of UO₂–ZrO₂ system.