Analysis of the Effect of Severe Accident Scenario on Debris Properties in Lower Plenum of Nordic BWR Using Different Versions of MELCOR Code

Table 1

MELCOR modeling parameters.

		MELCOR 1.86 [18, 19]	MELCOR 2.1 [20, 21]	MELCOR 2.2 [1, 2]
Gap Thickness (m)		0.075e-3	0.0[26]	0.0[26]
Velocity of Falling Debris (m/s)		Default 1.0.; 0.1 value was used in MELCOR 1.86 calculations [12, 24].	0.01[26]	0.01[26]
Particulate debris porosity (-)		0.25[34]	0.4[26]	0.4[26]
Particulate debris equivalent diameter in LP (m)		0.02	0.002[26]	0.002[26]
The max. molten Zr breakout flow rate (SC1141(2)) (kg/m-s)		1.0	0.2	0.2
COR-package candling heat transfer coefficient.; (W/m^2-K)	HFRZUO, HFRZZR, HFRZSS, HFRZZX, HFRZSX, HFRZCP	1000	7500; 7500; 2500; 7500; 2500; 2500	7500; 7500; 2500; 7500; 2500; 2500
COR package radiative heat transfer parameters (FCELR, FCELA)		0.25; 0.25	0.1; 0.1	0.1; 0.1
COR package min. porosity for flow (SC1505(1) – COR package, SC4413(5) – CVH package) and heat transfer SC1505(2) calculations.		0.001; 1.e-6; 0.001	0.05; 0.05; 0.05	1.e-5[25].; 0.05; 0.05
Zircaloy Oxidation Rate Constant Coefficients by Oxygen(SC1001(1-2,2)),; (see [18–21] for details)		50.4 Kg^2(Zr)/m^4-s; 14630.0 K	26.7 Kg^2(Zr)/m^4-s; 17490.0 K	26.7 Kg^2(Zr)/m^4-s; 17490.0 K
Conduction enhancement for molten components (SC1250(1))		3200K	2800K	2800K
Minimum fraction of the initial volume available to hydrodynamic materials (SC4414)		0.001	0.01	0.01