A study on macroscopic fuel cladding ductile-to-brittle transition at 300°C induced by radial hydrides

Figures & data

Table 1. Test samples

Sample ID	Assembly array	Local burnup (GWd/t)	Fast neutron fluence (×10^25 m^−2)
KYL4	8 × 8	57.5	11.7
KYL5		57.9	11.5
KYM5		52.5	8.36
KYM3		55.3	9.31
KYM4		54.4	9.02
KY87	9 × 9	68.8	12.8
KY90		67.5	13.2
KY96		68.4	13.1
KY94		67.7	13.1
KY95		68.1	13.1
KY92		66.6	13.1
KY93		66.5	13.0

Table 2. Hydrogen contents and values of Flθ/A for the samples along with the UTS and circumferential permanent strains to failure obtained from the tube burst tests described in Section 2.3

		Hydrogen content (ppm)
Sample ID	HCRT time (day)	Bulk	Liner removed	Flθ/A (mm/mm^2)	UTS (MPa)	Circumferential permanent strains to failure (%)	Notes
KYL4	-	205	133	10.4	763	7.5	As irradiated
KYL5	-	187	128	7.8	770	27.4	As irradiated
KYM5	9	713	192	24.7	750	6.5
KYM3	21	1303	320	52.1	628	0.4
KYM4	21	1401	343	47.5	643	0.5
KY87	-	120	67	8.1	728	7.6	As irradiated
KY90	3	265	102	17.5	725	5.0
KY96	3	277	150	15.3	722	5.8
KY94	9	661	204	20.2	743	4.5
KY95	9	655	113	19.1	735	5.3
KY92	21	1434	213	29.4	697	0.9
KY93	21	1515	315	30.9	546	0.2

Figure 1. Transverse metallographs of (a) KY87 (as irradiated), (b) KY90 (HCRT-3 days), (c) KY94 (HCRT-9 days), and (d) KY92 (HCRT-21 days). The cross sections of each sample were etched with a solution of HF, HNO₃ and H₂O₂ in a volume ratio of 0.8:3.0:40.0

Figure 2. Schematic of the image analysis for obtaining length and radial orientation of each hydride. The rectangular target domain does not include the Zr liner region nor the interface between the Zr liner and Zircaloy-2 region

Figure 3. Schematic of the tube-burst test device

Figure 4. Circumferential stress-strain curves obtained from the tube burst tests. The circumferential strains displayed were calculated as diameter increments at the longitudinal center of the samples during the test, and this calculation differs from that of the circumferential permanent strains to failure displayed in Figure 6

Figure 5. Circumferential UTS against Flθ/A

Figure 6. Permanent circumferential strain to failure against Flθ/A

Figure 7. Post-test photographs of (a) KY87 (as irradiated), (b) KY90 (HCRT-3 days), (c) KY94 (HCRT-9 days), and (d) KY92 (HCRT-21 days). Percentages in the lower right of each image indicate the circumferential permanent strain to failure

Figure 8. Post-test transverse metallographs of (a) KY87 (as irradiated), (b) KY90 (HCRT-3 days), and (c) KY94 (HCRT-9 days). Percentages in the lower right of each image indicate the circumferential permanent strain to failure

Figure 9. SEM fractographs of (a) KY87 (as irradiated), (b) KY90 (HCRT-3 days), and (c) KY94 (HCRT-9 days). Percentages in the lower right of each image indicate the circumferential permanent strain to failure

Figure 10. Post-test transverse metallographs of the samples subjected to HCRT for 21 days; (a) KY92, (b) KY93, (c) KYM3, and (d) KYM4. Percentages in the lower right of each image indicate circumferential permanent strain to failure

Figure 11. SEM fractographs of the samples subjected to HCRT for 21 days; (a) KY93 and (b) KYM3. Percentages in the lower right of each image indicate the circumferential permanent strain to failure