atw - International Journal for Nuclear Power | 2.2024

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72 Research and Innovation fuel (UO₂) at the beginning of the fuel length. This is due to the higher enrichment of the fuel which eventually burns out at the end of the fuel length. The packing fractions and enrichment of the FCM fuel kernel result in a significant difference in keff and burnup at the beginning and end of the fuel length. The keff and burnup rate versus the Effective Full Power Day (EFPD) for one complete fuel length is depicted in Fig. 8 and Figure 9, respectively. At the beginning of the fuel length, the reactivity of UO₂, UCO, and UN has been found to be 23501pcm, 28931pcm, and 29147pcm, respectively with the boron concentration of 140ppm. The UN has high reactivity due to the advantage of the density. The effective multiplication factor of UCO and UN FCM fuel is relatively 8.5 % higher than the UO₂ at the beginning of fuel length. However, the effective multiplication factor decreased monotonically for FCMbased fuel after 650 EFFDs with 140ppm soluble boron concentration. Contrary to this the average burn of UO₂, UCO, and UN FCM fuels remain similar. similar to the effective multiplication factor the burn up of UCO and UN-based FCM decreases monotonically after 650 EFPDs of the SMART reactor, resulting in a significant diminution of fuel cycle length (Fig. 6). It can also be seen from Figure 10 that the reactivity of FCM fuels decreases drastically with the burnup. (1) (2) (3) Where T is the fuel temperature and ρ is reactivity, which is a function of the criticality of the system and can be expressed as: (4) Using Eq (4) in Eq (3) and differentiating with respect to temperature gives the Eq (5) (5) Similarly, MTC can be expressed as follows. (6) (7) Fig. 10. The burnup vs the effective multiplication factor with 140 ppm boron concertation 3.3 Fuel temperature coefficient and Moderator temperature coefficient The reactivity coefficients have a significant effect on the effective multiplication factor, as they alter the interaction probability of neutrons with fissile and fertile fuel. These reactivity coefficients are the Fuel Temperature Coefficient (FTC) and Moderator Temperature Coefficient (MTC). The FTC is defined as the change in the reactivity with the change in the fuel temperature, while the MTC refers to the change in reactivity due to the change in moderator temperature. FTC and MTC can be expressed mathematically shown in Eq1 and Eq 2 [24] whereas the FTC in terms of reactivity is depicted in Eq 3. It has been noticed that the FTC of FCM fuels is less negative compared to the reference fuel (UO₂). The FTC has been evaluated from 300K to 1200K with the degree change of 100K. The 300K is considered as the reference temperature. FTC became less negative with the increase in fuel temperature. The least value of FTC has been found -1.82881 pcm/K with the 400K increase in fuel temperature from the reference temperature for UO₂. The FTC for the reference fuel remains in the range of -1.82881 pcm/K to 1.50749 pcm/K for the increase in fuel temperature from 100K to 900K from the refence fuel temperature. On the other hand, the FTC for the of UN and UCO has been found to be less negative compared to the standard fuel. However, the FTC for the FCM fuel also increases with the increase in fuel temperature. The FTC for UN and UCO remained in the range of -1.39908 pcm/K to -0.99062 pcm/K and -1.51367 pcm/K to -1.05743 pcm/K respectively with the increase in fuel temperature from 100K to 9000K from the reference temperature. When the coolant temperature increases the density decreases due to thermal expansion of coolant. The resonance escape probability decreases, which causes Ausgabe 2 › März
Research and Innovation 73 Fig. 11. Comparison of the Fuel temperature coefficient of FCM fuel with Standard fuel. Fig. 12. Comparison of Moderator temperature coefficient of FCM and Standard fuel neutron spectrum hardening. Contrary to FTC, the MTC remains positive and decreases monotonically with the increase in moderator temperature. The MTC remains positive for the standing fuel until the moderator temperature reaches 900 K (600 K increase from the reference temperature). While the MTC for UCO and UN remain positive because the moderator density remains higher than 700 kg/m³. However, the moderator density is 725 kg/m³.Moreover, with the increase in moderator temperature the density of the moderator decreases which results in diminishing the neutron thermalization. 4. Conclusion In this work, the FCM fuel has been replaced with the conventional design fuel of the SMART reactor. The FCM fuel based on the UN and UCO carbide kernel of 850 mm and 870 mm respectively has been investigated. The FCM fuel was replaced without the alteration of core design and fuel pallet dimensions alterations. The candidate designs of UCO started at 87.3 % less fertile 238U and about 28 % of fissile material 235U, while the UN cases are 79.78 % and 28.84 %, respectively. FCM fuel presents several significant challenges from the perspective of reactor engineering. Retrofitting of UO₂ with the FCM fuel in the existing LWRs or SMRs is a significant difficult problem. The initial reactivity in the FCM fuel assemblies required a significant consideration of burnable poison (dissolved or rod positions). However, in the case of dissolved burnable poison is a challenge as it alters the coolant chemistry that is sufficient to suppress the BOL reactivity and result in a stable equilibrium cycle. It is evident that for the realistic configuration, the fuel length would be compromised in reference to the conventional UO₂ fuel. However, the Cycle length of 800 EFPDs is acceptable for the SMART reactor when the safety of the reactor is ascendent. From the safety perspective, the FCM has fuel, has less PPF, and has less negative fuel temperature and moderator coefficient throughout the fuel operating length. Finally, SMART reactors can be operated safely for 850 EFPDs with the FCM fuel of UN and UCO Kernels Acknowledgment This research work was funded by the institutional fund projects under the grant number (IFPIP: 120-135- 1443). The authors gratefully acknowledge technical and financial support provided by the Ministry and King Abdulaziz University, DSR, Jeddah, Saudi Arabia. Reference [1] Chun, J.H.; Lim, S.W.; Chung, B.D. Safety evaluation of accident-tolerant FCM fueled core with SiC-coated zircalloy cladding for design-basis-accidents and beyond DBAs. Nucl. Eng. Des. 2015, 289, 287–295. [2] Snead, L.L.; Terrani, K.A.; Venneri, F. Fully ceramic microencapsulated fuels: A transformational technology for present and next generation reactors- properties and fabrication of FCM fuel. Trans. Am. Nucl. Soc. 2011, 104, 668–670. [3] Snead, L.L.; Terrani, K.A.; Katoh, Y. Stability of SiC-matrix microencapsulated fuel constituents at relevant LWR conditions. J. Nucl. Mater. 2014, 448, 389–398. [4] Lu, C.; Hiscox, B.D.; Terrani, K.A. Fully ceramic microencapsulated fuel in prismatic high temperature gas-cooled reactors: Analysis of reactor performance and safety Characteristics. Ann. Nucl. Energy 2018, 117, 277–287. [5] C. Gentry, N. George, I. Maldonado, A. Godfrey, K. Terrani, J. Gehin, Application of fully ceramic microencapsulated fuels in light water reactors, in: Int. Congr. Adv. Nucl. Power Plants 2012, ICAPP 2012, 2012. [6] C. Gentry, I. Maldonado, A. Godfrey, K. Terrani, J. Gehin, J. Powers, A Neutronic Investigation of the Use of Fully Ceramic Microencapsulated Fuel for Pu/Np Burning in PWRs, Nucl. Technol. 186 (2014). doi:10.13182/nt13-75. [7] Terrani, K.A.; Kiggans, J.O.; Katoh, Y. Fabrication and characterization of fully ceramic microencapsulated fuels. J. Nucl. Mater. 2012, 426, 268–276. [8] Al-zahrani, et al 2021. Neutronic performance of fully ceramic microencapsulated uranium oxycarbide and uranium nitride composite fuel in SMR. Annals of Nuclear Energy, 108152, DOI: 10.1016/j.anucene.2021.108152. [9] Terrani, K.A.; Zinkle, S.J.; Snead, L.L. Snead, Microencapsulated fuel technology for commercial light water and advanced reactor application. J. Nucl. Mater. 2012, 427, 209–224. [10] Venneri, F., Kim, Y., Snead, L.L., Terrani, K.A., Ougouag, A., Tulenko, J.E., Forsberg, C.W., Peterson, P.F., Lahoda, E.J., 2011. Fully ceramic microencapsulated fuels: a transformational technology for present and next generation reactors-preliminary analysis of FCM fuel reactor operation. Trans. Am. Nucl. Soc. 104 (668). [11] Pope, Michael A., Sonat Sen, R., Ougouag, Abderrafi M., et al., 2012. Neutronic analysis of the burning of transuranics in fully ceramic microencapsulated triisotropic tri-isotropic particle-fuel in a PWR. Nucl. Eng. Des. 252. 215-225 Vol. 69 (2024)
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4 Contents Inhalt Editorial Abschie
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6 Calendar Kalender 2024 07.03.2024
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8 Feature: Energy Policy, Economy
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18 Energy Policy, Economy and Law
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20 Energy Policy, Economy and Law
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Page 44 and 45: 44 Environment and Safety Initial
Page 46 and 47: 46 Environment and Safety S/N Docu
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Page 56 and 57: 56 Environment and Safety populati
Page 58 and 59: 58 Environment and Safety [38] A.
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Page 76 and 77: 76 Spotlight on Nuclear Law auf Ko
Page 78 and 79: 78 KTG-Fachinfo KTG-Fachinfo 02/202
Page 80 and 81: 80 KTG-Fachinfo Regierungsbericht v
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Page 88 and 89: 88 Kerntechnik 2024 Technical Sess
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