Core Concept of Small Rotational Fuel-Shuffling Breed-and-Burn Fast Reactor with Nitride Fuel and Sodium Coolant

Figures & data

TABLE I Core Specifications

Parameter	Value
Thermal power (MW)	450
Core eight (cm)	220
Core equivalent radius (cm)	106.5
Total number of assemblies	168 + 1 (coolant channel)
Number of fuel pins in an assembly	271
Fuel assembly pitch (cm)	15.8
Fuel material	^15N isotope 99% enriched UN
Coolant material	Sodium
Cladding material	ODS
Fuel rod radius (mm)	0.405
Cladding thickness (mm)	0.55
Fuel pin pitch (cm)	0.9434
Pellet density	90% TD
Smeared density	83% TD
Bond material	Helium
Fuel volume fraction	66.85%
Cladding volume fraction	19.39%
Coolant volume fraction	13.76%
Reflector material	Sodium
Shuffling pattern	Rotational
Fuel cycle length and steps	860 days and 56 steps^a
Average fuel temperature (K)	800
Average coolant temperature (K)	700
Coolant speed (m/s)	10.0

^aSteps mean the number of shuffling. In this case, shuffling is repeated with an interval of 860-days burnup.

Fig. 1. (a) Whole-core layout and (b) fuel shuffling pattern and position ID in one-sixth core.

Fig. 2. (a) Calculation geometry and (b) fuel cell model for heat removal analyses.

Fig. 3. Change of k-eff during the equilibrium cycles.

TABLE II Axial Distribution of Burnup, Average Discharge Burnup, Neutron Fluence, and DPA Value in the Discharged Fuel

Axial Region (cm)		Discharged Burnup at Equilibrium Sate					Fluence (All Energy) in Cladding (n/cm^2)	Fluence (E > 100 keV) in Cladding (n/cm^2)	DPA of Cladding Material
		Burnup^a (MWd/kgHM)	Fissions per Initial Metal Atom	Average Discharge Burnup (MWd/kgHM)	Average Discharge Burnup by Hand Calculation^b (MWd/kgHM)	Average Fissions per Initial Metal Atom
Zone 1	0 to 20	25.1	0.03	187.4	187.3	0.2	2.55E + 23	1.28E + 23	64
Zone 2	20 to 40	77.7	0.08				6.19E + 23	3.46E + 23	173
Zone 3	40  to 60	171.5	0.18				1.14E + 24	6.79E + 23	339
Zone 4	60 to 80	263.3	0.27				1.68E + 24	1.01E + 24	506
Zone 5	80 to100	322.1	0.33				2.01E + 24	1.24E + 24	618
Zone 6	100 to 120	341.4	0.35				2.16E + 24	1.31E + 24	656
Zone 7	120 to 140	322.1	0.33				2.01E + 24	1.24E + 24	618
Zone 8	140 to 160	263.3	0.27				1.68E + 24	1.01E + 24	506
Zone 9	160 to 180	171.5	0.18				1.14E + 24	6.79E + 23	339
Zone 10	180 to 200	77.7	0.08				6.19E + 23	3.46E + 23	173
Zone 11	200 to 220	25.1	0.03				2.55E + 23	1.28E + 23	64

^aDischarge burnup is the amount of energy per uranium in the initial fuel. In this analysis, we repeated the burnup calculation between shuffling. At the beginning of each burnup, the fuel composition is changed, with the previous composition obtained from the burnup calculation, resulting in a change in the initial loaded fuel. Therefore, after each burnup calculation in shuffling, the burnup output is corrected by the mass ratio of HMs in the discharged fuel.

^bThe average discharge burnup is precalculated based on thermal power and residence time and the amount of HM in the core.

TABLE III Axial Distribution of Pu Vector Ratios in Discharged Fuel

	Zones 1 and 11	Zones 2 and 10	Zones 3 and 9	Zones 4 and 8	Zones 5 and 7	Zone 6
^238Pu (%)	0.125	0.27	0.56	0.84	0.99	1.03
^239Pu (%)	91.627	86.50	78.77	72.72	69.35	68.31
^240Pu (%)	7.871	12.40	18.77	23.42	25.89	26.63
^241Pu (%)	0.350	0.75	1.63	2.44	2.93	3.09
^242Pu (%)	0.027	0.07	0.27	0.58	0.85	0.94

Fig. 4. Radial power distribution at the BOEC and EOEC of the equilibrium cycle.

Fig. 5. Axial temperature profile in hottest channel.