Simulation of the fracture behavior of Zircaloy-4 cladding under reactivity-initiated accident conditions with a damage mechanics model combined with fuel performance codes FEMAXI-7 and RANNS

Figures & data

Figure 1. An elevation of the cladding tube model.

Table 1. Damage model parameters.

		Temperature (K)
		300	620
	[−]	0.10	0.40
	[μm]	2	15

Figure 2. FEM models of the cladding tube: (a) horizontal cross section, (b) vertical cross section, (c) geometry of the damage region for smooth specimens, and (d) geometry of the damage region for pre-cracked specimens.

Figure 3. Fracture appearances of a smooth specimen in the simulated burst test at 300 K.

Figure 4. Simulation results of the RAG–EDC test: (a) outer surface strain at failure compared with experimental results and (b) fracture appearances of pre-cracked specimens.

Figure 5. Hoop strains calculated under different stress states around the tip of a 100-μm crack in a wall of 570 μm thickness: (a) hoop strain distributions at ϵ_m,θ = 2% and (b) variations of strain concentration with increasing hoop strain ϵ_m,θ.

Figure 6. Sensitivity of failure strains at 300 K to the damage parameters and : (a) residual hoop strains calculated in the burst test analysis and (b) outer surface hoop strains at failure calculated in the RAG–EDC test analysis.

Figure 7. Fracture appearances of the claddings in the NSRR tests L6 and H6: horizontal cross sections of the fuel cladding around the fracture positions.

Table 2. Summary of the RANNS calculation conditions.

	Employed model
Thermal expansion coefficient [14,15]	Pellet: MATPRO-A, cladding: MATPRO-11
Thermal conductivity [16,17]	Pellet: Ohira and Itagaki model, cladding: MATPRO-09
Specific heat [15]	MATPRO-11
Gap conductance [9,18]	Modified Ross and Stoute model
Young's modulus [15]	MATPRO-11
Pellet plasticity [19]	0.15 σy (≤ 1273 K), σy (> 1273 K) σy: yield stress given by Tachibana's model
Cladding plasticity [20]	The latest MATPRO model with initial cold work 0.5, K (Zry) = 1.0, and n (Zry) = 1.0
Pellet relocation amount [9]	1% of pellet outer diameter
PCMI in axial direction [9]	Friction coefficient approach adjusted with scaling factor Ffric = 1.0

Figure 8. Evolution of (a) axial stress with increasing hoop stress and (b) axial strain with increasing hoop strain in the cladding periphery.

Figure 9. Radial temperature profiles in the cladding wall at failure time.

Figure 10. Cladding inner surface strains at failure calculated with the damage model compared to the NSRR test results.

Figure 11. Simulated fracture appearances of the pre-cracked claddings in cases D0.0F, D1.0F, and P0.0F.

Figure 12. Simulated crack propagation in case P0.0F. Through-wall penetration by a crack is achieved with very a small strain increment.

Figure 13. Evolutions of the state variables ω_D and D at the tip of a 50-μm crack with increasing cladding inner radius, in the cases D0.0F and D1.0F.

Hagrman DL, Reymann GA. MATPRO-VERSION 11: a handbook of materials properties for use in the analysis of light water reactor fuel rod behavior. NUREG/CR-0497. Washington (DC): US Nuclear Regulatory Commission; 1981.

 Google Scholar

Suzuki M, Saitou H, Udagawa Y. Light water reactor fuel analysis code FEMAXI-7; model and structure. JAEA-Data/Code 2010-035. Ibaraki (Japan): JAEA; 2010. Japanese.

 Google Scholar

Ross AM, Stoute RL. Heat transfer coefficient between UO₂ and Zircaloy-2. CRFD-1075. Ontario (Canada): Atomic Energy Commission of Canada Limited; 1962.

 Google Scholar

Tachibana T, Furuya H, Koizumi M. Effect of temperature and deformation rate on fracture strength of sintered uranium dioxide. J Nucl Sci Technol. 1976;13:497–502.

 Web of Science ®Google Scholar

Geelhood KJ, Luscher WG, Beyer CE, Cuta JM. FRAPTRAN 1.4: a computer code for the transient analysis of oxide fuel rods. NUREG/CR-7023. Washington (DC): US Nuclear Regulatory Commission; 2011.

 Google Scholar