Effects on Criticality and Burnup Calculations Changings ADS Cladding Material
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ADS system The materials used for the structure of the ADS are iron and lead for the coolant and the spallation target. The spent nuclear fuel matrix was obtained from a PWR standard fuel (33,000 MWd/T burned), with 3.1% of initial enrichment left by 5 years in the pool [10]. The spent fuel was then reprocessed by Ganex process and spiked with thorium [11]. The simulated core was a cylinder of 12.0 m3 filled with a hexagonal lattice formed by 156 fuel rods. The fuel rod radius is 3 cm and rod height is 400 cm. The fuel used in 120 rods was ThO2; it has an initial mass of ThO2 about 13571 kg. The fuel used in the other 36 rods was reprocessed fuel spiked with thorium (4071.50 kg). The axial and radial geometry are shown in Fig.1 The theoretical density for reprocessed fuel spiked with thorium was 10 g.cm-3.The reprocessed fuel has been spiked with 53% of thorium to reduce the percentage of fissile isotopes, which had 60% of fissile isotopes (233U, 235U, 239Pu, and 241Pu) after reprocessing and to obtain a keff around 0.98. The materials used for the clad are ODS (oxide dispersed strengthening), ferritic martensitic steel (T91), austenitic stainless steel (15/15Ti), and stainless steel (SS-316). All of them are used in liquid metal fast reactors [12]. The duration of these materials during 20 years is
Figure 1 – Axial and radial cross section Table 1. Fuel composition reprocessed by Ganex method and spiked with 53% of thorium [8] Nuclide Fraction Nuclide Fraction Nuclide Fraction 232 239 242 Th 4.6637E-01 Np 2.0539E-03 Cm 1.0826E-03 233 238 244 U 8.6754E-12 Pu 7.7613E-03 Cm 1.2411E-03 234 239 245 U 6.4825E-07 Pu 2.0323E-01 Cm 4.3188E-05 235 240 143 U 3.3737E-05 Pu 6.9479E-02 Nd 5.1593E-03 236 241 147 U 1.7246E-05 Pu 6.5328E-02 Sm 1.0346E-03 237 242 153 U 2.4571E-08 Pu 2.4688E-02 Eu 2.2001E-04 238 241 U 4.1012E-03 Am 3.4769E-03 O 1.2005E-01 237 242m Np 1.9855E-2 Am 6.3986E-06 238 243 Np 3.253E-05 Am 4.7214E-03 DISCUSSION The effects on the source multiplication factor and the mass depletion of using different clad materials for the ADS system. The burnup calculations were performed using 292 time steps of 25 days; the total simulated time was 10 years and the thermal power of operation throughout this period was 515MWt for each case. The number of initial particles for MCNP5 calculations was 2000. The burnup for 20 years is around 2.2E+04 GWd/MTU for the reprocessed fuel and 7.9E+04 GWd/MTU for the fuel rods with ThO2. Neutronic The emphasis of this work was to study the fuel irradiation of the different materials as a theoretical approximation of the neutronic behavior under long irradiation, despite this the cladding materials will not withstand such long periods of irradiation. Fig.2 shows the source multiplication factors for different clads used in this study. The criticality behavior is very similar in all simulated cases. The system of reference is the one simulated without clad material (no clad). The source multiplication factor without clad has slightly higher values of criticality, as shown in the Fig.3. It
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