High burn-up operation and MOX burning in LWR; Effects of burn-up and extended cooling period of spent fuel on vitrification and disposal

Figures & data

Figure 1. Evolution of heat generation rate of UO₂ and MOX spent fuel per THM.

Figure 2. Contribution of minor actinides in UO₂ spent fuel (70GWd/THM) on heat generation rate.

Figure 3. Contribution of minor actinides in MOX spent fuel (45GWd/THM) on heat generation rate.

Figure 4. Contribution of transuranium isotopes in MOX spent fuel (45GWd/THM) on heat generation rate.

Table 1. Waste loading and number of glass units per THM at various conditions of burn-up and cooling period (upper table, UO₂ fuel; lower table, MOX fuel)

		Waste loading (wt%)		Number of glass units				Restriction factor
				(Glass unit/THM)		(Glass unit/GWd)
UO2 Fuel	Cooling period (year)	Burn-up (GWd/THM)
		55	70	55	70	55	70	55	70
	4	20.88	20.49	1.515	1.966	0.0275	0.0281	Heat
	10	21.81	21.68	1.406	1.777	0.0256	0.0254	MoO3 content
	20	21.90	21.76
	30	21.96	21.81
		Waste loading (wt%)			Number of glass units						Restriction factor
					(Glass unit/THM)			(Glass unit/GWd)
MOX Fuel	Cooling period (year)	Burn-up (GWd/THM)
		28	33	45	28	33	45	28	33	45	28	33	45
	4	16.32	16.17	16.05	1.550	1.820	2.435	0.0554	0.0552	0.0541	Heat
	10	19.85	20.01	19.53	0.995	1.175	1.614	0.0355	0.0356	0.0359	PGM content
	20	20.85	20.52	20.02			1.607			0.0357
	30	21.17	20.83	20.32

Table 2. Required separation ratio of Mo and PGM and waste loading of waste glass

			UO2 Fuel		MOX fuel
Cooling period	Burn-up (GWd/THM)		55	70	28	33	45
10	Waste loading (wt%)		29.0	27.8	20.1	20.1	19.5
	Required separation ratio (%)	Mo	44.7	41.4	-	-	-
		PGM	42.3	41.1	3.1	1.4	-
20	Waste loading (wt%)		34.3	33.1	22.4	22.0	21.5
	Required separation ratio (%)	Mo	58.2	56.5	-	-	-
		PGM	56.3	56.2	14.4	14.4	14.9
30	Waste loading (wt%)		39.3	38.1	23.9	23.6	23.2
	Required separation ratio (%)	Mo	65.9	65.1	-	-	-
		PGM	64.4	64.9	21.9	22.9	25.0

The hyphen means separation of the element is not required because heat generation rate is already reached to 2.3 kW/glass unit without its extraction

Figure 5. Number of glass units per THM with respect to restriction factors of waste loading of waste glass and effects of cooling period of spent fuel; (a) UO₂ fuel, (b) MOX fuel.

Figure 6. Number of glass units per GWd with respect to restriction factors of waste loading of waste glass and effects of cooling period of spent fuel; (a) UO₂ fuel, (b) MOX fuel.

Figure 7. Evolution of heat generation rate of waste glass with 4 years cooling period of spent fuel; (a) UO₂ fuel, (b) MOX fuel.

Table 3. Effects of Am separation on heat generation rate and storage period before disposal for waste glass from MOX spent fuel with burn-up of 45GWd/THM

		Am separation ratio (%)
	Cooling period of spent fuel (year)	0	30	50	70	90
Waste loading (wt%)	10	19.53	19.10	18.78	18.47	18.15
	20	20.02	19.42	19.01	18.60	18.19
	30	20.32	19.62	19.15	18.69	18.22
Initial heat generation rate (kW/glass unit)	10	2.30	2.15	2.05	1.94	1.84
	20	1.96	1.74	1.60	1.45	1.31
	30	1.73	1.47	1.31	1.14	0.97
Approximate time to reach 0.35kW/glass unit (year)	10	290	130	90	70	60
	20	480	250	120	70	50
	30	560	350	150	70	40

Figure 8. Effects of extended cooling period on evolution of heat generation rate of waste glass; (a) UO₂ fuel with burn-up of 70GWd/THM, (b) MOX fuel with burn-up of 45GWd/THM.

Figure 9. Contribution of minor actinides on heat generation rate of waste glass (MOX fuel, Burn-up; 45GWd/THM, Cooling period of spent fuel; 10 years).

Figure 10. Evolution of heat generation rate of waste glass as a function of Am separation ratio; (a) overall figure, (b) enlarged figure (MOX fuel, Burn-up; 45GWd/THM, Cooling period of spent fuel; 10 years).

Figure 11. Relationship between the maximum temperature of buffer material and occupied area per waste package corresponding to Figure 7 (a) and 8 (a) (UO₂ fuel, Burn-up; 70GWd/THM).

Figure 12. Relationship between the maximum temperature of buffer material and occupied area per waste package corresponding to Figure 7 (b) and 8 (b) (MOX fuel, Burn-up; 45GWd/THM).

Figure 13. Relationship between the maximum temperature of buffer material and occupied area per waste package corresponding to Figure 10 (MOX fuel, Burn-up; 45GWd/THM, Cooling period of spent fuel; 10 years, Am separation is applied).

K. Kawai: High Burn-up Operation and MOX Burning in LWR; Effects of Burn-up and Extended Cooling Period of Spent Fuel on Vitrification and Disposal