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Title: Combined effects of radiation damage and He accumulation on bubble nucleation in Gd 2Ti 2O 7

Pyrochlores have long been considered as host phases for long-term immobilization of radioactive waste nuclides that would undergo α-decay for hundreds of thousands of years. This work utilizes ion-beam irradiations to examine the combined effects of radiation damage and He accumulation on bubble formation in Gd 2Ti 2O 7 over relevant waste-form timescales. Helium bubbles are not observed in pre-damaged Gd 2Ti 2O 7 implanted with 2 × 10 16 He/cm 2, even after post-implantation irradiations with 7 MeV Au 3+ at 300, 500, and 700 K. However, He bubbles with average diameters of 1.5 nm and 2.1 nm are observed in pre-damaged (amorphous) Gd 2Ti 2O 7 and pristine Gd 2Ti 2O 7, respectively, after implantation of 2 × 10 17 He/cm 2. In conclusion, the critical He concentration for bubble nucleation in Gd 2Ti 2O 7 is estimated to be 6 at.% He.
Authors:
 [1] ;  [1] ;  [2] ;  [3] ;  [1] ;  [4] ;  [1] ;  [5] ;  [6]
  1. The Univ. of Tennessee, Knoxville, TN (United States)
  2. Idaho National Lab. (INL), Idaho Falls, ID (United States); National Renewable Energy Lab. (NREL), Golden, CO (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); The Univ. of Tennessee, Knoxville, TN (United States)
  4. Lanzhou Univ., Gansu (China); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  5. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  6. The Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Report Number(s):
INL/JOU-16-39501
Journal ID: ISSN 0022-3115; PII: S0022311516304536
Grant/Contract Number:
AC07-05ID14517
Type:
Accepted Manuscript
Journal Name:
Journal of Nuclear Materials
Additional Journal Information:
Journal Volume: 479; Journal Issue: C; Journal ID: ISSN 0022-3115
Publisher:
Elsevier
Research Org:
Idaho National Lab. (INL), Idaho Falls, ID (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
Language:
English
Subject:
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; He; He bubble; Oxide; STEM; Waste form
OSTI Identifier:
1396002
Alternate Identifier(s):
OSTI ID: 1359432