Milestone 2.8: Preliminary Radiolytic Gas Generation Measurements from Helium-Backfilled Samples
- Idaho National Lab. (INL), Idaho Falls, ID (United States)
The Department of Energy (DOE) is currently managing nearly 13 metric tons of aluminum-clad spent nuclear fuel (ASNF) with the intention of extended (> 50 years) dry storage in helium-backfilled canisters. Due to in-reactor and cooling pond conditions, oxyhydroxide corrosion layers have formed on the surface of the ASNF elements. These corrosion layers are susceptible to radiolysis and the formation of molecular hydrogen gas (H2) due to the fuel’s inherent radiation field. Consequently, a rigorous evaluation of the effect of helium gas on radiolytic H2 production is necessary to support the Technical Considerations and Challenges for Extended (> 50 yrs) Dry Storage of ASNF program, especially as previous Task 2 - Oxyhydroxide Layer Radiolytic Gas Generation Resolution work demonstrated a significant effect of gas composition on the radiolytic yield (G-value) of H2. Here we report preliminary G-values for the radiolytic formation of H2 from the gamma irradiation of pre-corroded aluminum alloy 1100 coupons flame sealed in helium environments. Irradiations yielded G(H2) values of (5.1 ± 0.5) x 10–4 and (9.4 ± 0.9) x 10–4 µmol J–1 for pristine coupons, and (10.1 ± 0.4) x 10–4 and (15.1 ± 1.2) x 10–4 µmol J–1 for pre-corroded coupons for 0% and 50% relative humidity, respectively. These helium environment G(H2) values are between 28% and 58% higher than previously reported values for argon environments. This enhancement is attributed to the significant difference in first ionization energy between helium (24.59 eV) and argon (15.76) facilitating additional processes, e.g., Penning ionization. These new preliminary helium environment G(H2) values will be employed by Task 3 - Sealed and Vented System Episodic Breathing and Gas Generation Prediction to model the effect of radiolytic H2 accumulation in helium environments to evaluate the practicality of the extended storage standard canister design.
- Research Organization:
- Idaho National Laboratory (INL), Idaho Falls, ID (United States)
- Sponsoring Organization:
- USDOE Office of Environmental Management (EM)
- DOE Contract Number:
- AC07-05ID14517
- OSTI ID:
- 1768757
- Report Number(s):
- INL/EXT--21-61404
- Country of Publication:
- United States
- Language:
- English
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