Risk insights of the cracking of carbon steel and stainless steel

Figure 7.7 shows an example of the radionuclide release fraction to the environment from a cask (Sprung et al. , 2000). Casks include canister and other overpacks. Strictly speaking, this figure was constructed for a trans­portation cask. Nevertheless, the radionuclide release behaviour would be similar in the storage cask. The radionuclide release fraction is expressed by (1.0 — Retention). In this range of the surface opening area, the surface

image117

7.7 Cask-to-environment release fractions (1.0 — Retention) versus open cask surface area (Sprung et al., 2000).

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Time (yr)

———- [C14] ————- [Cs135 ]————— [I129 ] ———- [Pu212 ]

7.8 Example в-SOAR (Markley et al., 2011) dose results for only commercial SNF using combined degradation rate in a stylized reducing geological disposal system (Ahn et al., 2011a). Used with permission from American Nuclear Society (ANS).

opening is already wide enough to result in the release fraction approaching to 1. This retention mechanism is in addition to the low radionuclide release fraction from the degraded UO2 matrix and the failed cladding. In reality, the surface area opening by SCC may be smaller because the model of Eq. [7.1] is conservative.

Figure 7.8 (calculated using the в-SOAR model of Markley et al., 2011) shows an example of a calculation of radionuclide release from the seismic — induced SCC of various disposal containers (Gwo et al., 2011). There is an additional factor lowering the magnitude of radionuclide release due to the restricted perforation made by SCC.

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